Thoughts on the DJI Digital FPV System

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Not too long ago, DJI released a new digital video-transmission system for FPV miniquad pilots. I’ve been keeping an eye on it. I’ve been watching videos. I’ve been listening to what people say. I’ve been trying to figure out if this is a system that I’m going to want to buy into.

I am not going to be buying into DJI’s ecosystem at this time. DJI’s new system has a lot going for it, especially if you’re a brand new pilot and haven’t already invested in analog gear.

I’m going to do my best to explain why DJI’s FPV system isn’t for me. I’m going to start with problems that are easy to measure, then work my way towards the less concrete things.

The DJI FPV Air Unit is too big

The Air Unit is the box of electronics and the FPV camera that sit on your miniquad. It is just too big, and in some cases, much too heavy.

It won’t fit nicely into any of my existing freestyle frames. To be honest, this is a minor complaint. I’m cutting my own frames now anyway. Correcting this problem would just involve cutting new bottom and top plates for two or three of my quads.

If you’re not me, you might have to buy new frames. You’ll probably be spending $50 to $100 per frame, right?

The Air Unit weighs about 45 grams. That extra 20 to 30 grams or so compared to my existing VTX and camera won’t be a big deal on my 5” freestyle miniquads, but what about my 3” and 4” sub-250 gram Kestrel builds? My camera and VTX combination on my micros is already lighter than what I use on my 5” rigs, so the Air Unit might add even more weight.

The current size and weight of the Air Unit make it unusable for my 3” and 4” builds.

I fully expect DJI to miniaturize this hardware. When they do, I will have to revisit this topic!

Even if they do miniaturize the Air Unit, we’re not going to see it on whoops or toothpicks any time soon. This brings me to my next problem.

I don’t want to carry two sets of goggles

My ThinkTank backpack is huge, but it is already more than full. I’d have to rearrange everything just to fit the larger DJI goggles in place of my Fat Shark goggles. I definitely don’t want to have to find a way to squeeze both sets of goggles in there!

My goal is to fit everything I need for a day out flying in my bag, so it is already packed pretty tight!

Can’t you plug an analog receiver into the DJI goggles?

Yes. Sort of. There is a way to make this happen, but you have to modify the goggles a bit. I think this will be a fantastic option for people that buy into DJI’s system. You can fly your nice, big, expensive quads with your digital link. Then you can still fly a TinyHawk around the house with an analog receiver.

So far, I haven’t heard any good things about using the analog input on the DJI goggles. Maybe this will get better with a firmware update, but it sounds like for the time being, using the DJI goggles to fly an analog quad isn’t a great experience.

My TinyHawks

The weird analog feed to the DJI goggles might be good enough for playing around with a TinyHawk around the house, but I don’t want to use it with my HD micro freestyle builds.

Don’t you want HD video, Pat?!

My impression so far is that DJI’s HD video feed isn’t a straight-up upgrade over what I have today. Some things are greatly improved. Other aspects, not so much.

It is absolutely amazing that you can get eight pilots in the air at once, and they all have amazing video feeds. When you have good signal, the picture is clear.

I have some concerns about the dynamic range and the speed of the DJI camera’s transition from light to dark.

NOTE: That’s my GoPro HERO5 Session going around the track!

My Runcam Eagle Micro sometimes looks like I’m flying in an oversaturated cartoon landscape, but I can usually see my friend walking in the shade under dense trees. When I’m flying through a parking garage, I can see shapes in the sun outside instead of just blown-out highlights.

Maybe I’m worried over nothing. Maybe if I could fit the DJI Air Unit on my 3” builds, I would ignore this concern completely!

What about the DJI system’s range?

I can’t make up my mind here. We’ve seen Le Drib fly his DJI system inside a building where his analog setup was barely working. We also hear about it randomly dropping out when analog would be fine.

In other words, DJI’s range and overall performance isn’t a straight-up upgrade over what I’m already flying. Sure, it has plenty of improvements, but I still keep seeing the drawbacks. In some situations, the DJI gear outperforms my analog gear. In some situations, my analog gear can do better. In most situations, the only thing I’m giving up is the more detailed HD image.

Price isn’t the problem

I absolutely adore my TBS Crossfire. Knowing that my control link is absolutely rock solid makes me so much more confident. If you’re a new pilot, though, and you’re planning to use DJI’s control link, then the DJI system’s price compares quite favorably to analog.

The DJI FPV Experience Combo costs about $1,000 and comes with goggles, a controller, and enough Air Units and antennas for two quads.

An old shot of my ThinkTank backpack

If you add up Fat Shark HDO goggles ($500), a RapidFire module ($160), a Taranis Q X7 ($105), a Crossfire Micro TX module ($70), two Crossfire Nano RX modules ($35 x 2), and a pair of RaceDayQuads VTX modules ($25 x 2), you’ll end up at $955.

As you build more quads, the analog pricing starts to look better, but not by a ridiculous margin. However, that top of the line analog system I listed isn’t the only option. You can spend half as much on the goggles and video receiver, and you can completely skip the Crossfire stuff. That wouldn’t be as fair a comparison, though.

One important thing to note here is that you can buy into our old analog video system on a budget. Sure, top-of-the-line analog hardware is comparable in price to the DJI FPV system. The goggles I run cost $200 less than the Fat Shark HDO goggles. I’d bet you could get a pretty nice analog setup for half the price, and entry-level hardware can be had for 10% of the price of the DJI setup.

If they cost the same, why buy into analog today?

Your friends are already flying analog. When I went to a MultiGP race for the first time last month, every single pilot was flying analog. These were all people I hadn’t met before, and I could tune in to any of their video feeds to spectate.

When I go flying with my friends, I can tune in to their flights, and they can tune in to mine. They can give me pointers. I can praise them when I see them pull off a neat maneuver. We can all hoot and holler when we see a spectacular crash!

My Falcon Freestyle quad

I’d hate to be the one person in the group using DJI goggles, especially if I’m new to the hobby. If your quad is doing something funny when you yaw 180 degrees, I might need to see it happen through the goggles to help you out. Maybe it doesn’t happen when I fly your quad because the problem is something the pilot is doing.

This alone is enough reason for me to still recommend analog today. For me, FPV is about community. I’d hate to be the one guy out there doing it alone!

DJI FPV goggles aren’t compatible with DJI’s photography drones

What?! This surprised me quite a bit when the system was released. If you told me that I can carry one set of goggles and use it with my FPV miniquads AND a Mavic 2, it would be amazing. I’d go right out and buy a Mavic!

The FPV goggles aren’t compatible. They’re two very different video protocols. Isn’t that a bummer?

Maybe DJI’s products will converge in a few years!

What about Fat Shark Byte Frost?!

I had high hopes for Byte Frost. The video transmitter board is just a standard 30x30 board that will fit right in your stack. I can even fit that in my 3” Kestrel, and it isn’t nearly as heavy as the DJI Air Unit!

Unfortunately, Byte Frost just doesn’t look like it can compete with DJI. In Joshua Bardwell’s test, Byte Frost’s range with directional patch antennas was worse than DJI’s range with omni antennas.

Byte Frost seems to only support four quads at a time, while we’ve all seen DJI’s system allow 8 pilots to fly simultaneously.

That said, it is my understanding that Byte Frost has low, consistent latency. When your signal gets weak, the DJI system’s latency increases and the quality drops. When the Byte Frost signal gets weak, it seems to start dropping bits of the picture, but the latency stays low.

Even though it has a couple significant advantages over the DJI FPV system, I don’t believe things look good for Byte Frost at this point.


Maybe you don’t care about having to carry two sets of goggles. Maybe your entire fleet can carry a DJI Air Unit. Maybe the DJI FPV system is a good fit for you.

It just isn’t a good fit for me, and I bet that’s true for most of you folks, too. Electronics always get smaller and cheaper. I have hopes that the next revision of DJI’s FPV system will be a better fit for more of my fleet, and the revision after that will likely be even better! It doesn’t have to fit on my whoops. If DJI can cover my 3”, 5”, and larger quads, I would feel comfortable leaving my Fat Sharks at home!

What do you think? Are you excited about DJI’s digital video quality? Do you want to fly with a feed that looks more like a GoPro? Or do you think that the community of spectators is still more important? Let me know what you think in the comments, or stop by the Butter, What?! Discord server to chat with me about it!

Betaflight 4.1 and the RPM Filter

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I’ve been procrastinating for a long time. All my 5” freestyle quads and even my 4” micro Kestrel have the hardware to support Betaflight’s RPM filter. All you need is an F4 flight controller and, until recently, blheli_32 ESCs. Using the RPM filter with Betaflight 4.0 requires a bit of extra tinkering, but it didn’t seem like I big deal.

The trouble was that my quads were all flying great. I worked hard tuning Betaflight 4.0. I wanted to reduce propwash oscillation as much as I could, and I think I did a pretty good job. I turned off as many filters as I could. I loosened up the remaining filters a bit to improve latency. Then I pushed my D-term as far as I could.

I thought it was flying great. When we flew with Alex Vanover, I asked him to fly my quad, and he didn’t seem to think it needed much tuning. If I thought it was flying great, and the fastest drone racing pilot in the world thought it was flying well, why would I mess with it?

I messed with it

Mark Spatz at UAV Tech posted a video about the settings you should start with if you want to try flying Betaflight 4.1 with the RPM filter. Everything is straight forward now. When I set it up, I had to download test firmware for my ESCs, but bidirectional Dshot support is currently in the official blheli_32 release, so you won’t have to worry about that.

I’m flying an iFlight TwinG F7 flight controller. It has two identical gyros, but one of those gyros is rotated 90 degrees. Betaflight reads both gyros and takes the average of those readings. This buys you a few decibels of noise filtering with no increase in latency. Betaflight 4.0 could not perform this sensor fusion while using the RPM filter. Betaflight 4.1 can!

I updated one of my quads to Betaflight 4.1. I set up the RPM filter according to Mark Spatz’s instructions. I set up my rates, but I left the PID settings alone. Then I took my quad to the golf course.

I can’t believe that it flies better!

We’re running out of improvements at this point. When I upgraded from Cleanflight to Betaflight, it was like a quantum leap forward. You’d say things like, “Holy potatoes! I can’t believe it stops smoothly after a snap roll!”

Then I upgraded from Betaflight 3.3 on an Kakute F4 to Butterflight on a Helio Spring. The difference wasn’t as dramatic, but I will say this is the first time I had a quad that could handle propwash well.

Upgrading from the defunct Helio board to my dual-gyro F7 flight controller and Betaflight 4.0 was a nice upgrade. Tuning became a little easier and propwash handling improved. There are also a lot of nice quality of life updates, too.

NOTE: If you have a Helio Spring, you should check out EmuFlight. They’re doing a good job resurrecting Butterflight and the Helio’s IMU-F. Don’t let your old hardware go to waste!

Our quads are already flying amazingly well—nearly perfectly. Can it really get much better?

Yes. Betaflight 4.1 with the RPM filter flies noticeably better, but it is the sort of improvement that you’re only going to notice when you’re pushing things to the edge of what Betaflight 4.0 can handle.

You can always fly around propwash oscillations. When I flew that first pack with the RPM filter, I did my very best to do the opposite. I tried to bring out as much propwash as I could!

I did the move where you fly forward, cut the throttle, then do a 180 degree turn. Then I’d blip the throttle pretty hard and go back the other way. My 4.0 tune did well at this, and so did the RPM filter. No surprises there.

NOTE: I don’t have great before-and-after comparison of my well tuned quad. I tested on my backup quad, which was much closer to running stock Betaflight 4.0 settings. That’s my backup quad in the Tweet above.

Then I started popping up over trees to do some power loops and S-turns. This is the time when I’m most likely to be bummed out about propwash in my GoPro footage. You know when you don’t quite line up the move like you should, and you just can’t hit the throttle until the very last moment. I did my best to simulate those moments.

I’d line up my exit under the tree, fall with zero throttle until the last possible moment, then I’d punch the throttle harder than I should. I’ve practiced doing this smoothly for so long that it is difficult to do it poorly on purpose, but when I did, I couldn’t see any oscillations in my goggles, and it sounded smooth to my ears.

You could see some oscillation in the GoPro footage, but it is extremely brief.

My settings

This is the part where I’d usually just paste in a dump from the Betaflight command line. I don’t want to do that this time. I think it is important to understand a little about what you’re changing.

There are plenty of videos showing you what to do. If that’s the way you prefer to ingest your knowledge, you should check out UAV Tech’s RPM filter guide or [Joshua Bardwell’s RPM filter setup guide][wdrpm]. These are the places where I got my information!

Betaflight 4.1 RPM Filter

On the configuration tab in the Betaflight Configurator, you need to enable bidirectional Dshot. On my F7 flight controller, I’m running a 4K/4K PID loop. You can probably get away with an 8K/8K PID loop, and I’m going to experiment with this, but for now, you should play it safe.

NOTE: I forgot to mention motor poles. If you’re flying 2306, 2205, 2206, or 2207 motors, then the default of 14 is most likely correct. You can check the specs of your motor on the manufacturer’s or vendor’s website, or you can count the magnets. If you’re setting this up on a micro, 14 is likely to be incorrect!

I’ve learned that at if you have bidirectonal Dshot enabled in Betaflight, and your ESC firmware doesn’t support it, then Betaflight will refuse to communicate with your ESCs. At least it shouldn’t go bananas on you if you fail to correctly upgrade your ESC firmware!

Betaflight 4.1 RPM Filter

You’ll need to be running blheli_32 version 32.7 or newer. You should also be able to use the JESC firmware on blheli_s ESCs, but I haven’t tested this.

Betaflight defaults to using three layers of RPM filtering. I believe that gives you a total of 12 notch filters. One for each motor at three different resonance frequencies. I was happy with how my quad flew with one level of RPM filters, but Joshua Bardwell talked me into trying the default of three.

You should set the width of your dynamic filter to 0. With the default of 8, you will be running a pair of dynamic filters that are 4% or 8% above and below the target frequency. We don’t need that with the RPM filter. When you set this to zero, you will remove one of those dynamic filters and decrease your latency.

I’m running my dynamic notch filter with a Q-factor of 250. Joshua Bardwell recommended starting at 200. The higher the number, the narrower the filter, and the lower the latency. I’m unsure how I got up to 250, but it is working fine for me, so I’m sticking to it.

Betaflight RPM Filter Filtering Settings

NOTE: I didn’t adjust any of the checkbox or numbers in the boxes above the RPM filter and below the sliders. These adjust themselves as you move the sliders up and down!

You should lower the dynamic filter’s minimum frequency to 90 hz.

The rest of my filter tuning consisted solely of moving the two sliders farther and farther to the right. I’d move then two or three clicks, go outside, and fly around for a minute. If my motors were still cool, I’d move the sliders again.

I have both sliders maxed out, and my motors barely get warm.

Who should upgrade?

If your quad is flying just fine, and you’re not complaining about propwash oscillation, you should probably just keep doing whatever it is that you’re doing. It is difficult to get better at flying if you keep changing your setup. If you’re happy, just keep flying.

What if your quad doesn’t fly so well? Do you have weird twitches and vibrations? Maybe you just have a failing component that just has to be replaced, and no amount of software will be able to make it fly right. Then again, maybe Betaflight 4.1 and the RPM filter will help out your problematic quad.

Or maybe you’ve been running Betaflight 3.4 or 3.5 for a long, long time. You’ve been hearing good things about Betaflight 4.0, but you just weren’t ready to put in the effort to upgrade your flight controllers. I’d say now is the time to upgrade, especially if you’re going to be able to use the RPM filter with your hardware.


I’ve been thinking about upgrading to a prerelease of Betaflight 4.1 for months. I wish I did it sooner. There’s not much excuse to wait now, because as I was writing this blog post, Betaflight 4.1 was officially released!

What do you think? Am I going to have to buy the JESC firmware for my Kestrels? Have you been running the RPM filter for a while? Were you using it with Betaflight 4.0, and did your quad’s flight characteristics improve even more when you upgraded to Betaflight 4.1? Do you also think it is time for everyone to start upgrading? Let me know in the comments, or stop by [the Butter, What?! Discord server][bwd] to chat with me about it!

What I’ve Learned About 4-Inch Miniquads

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When I started designing my Kestrel, I knew that I would have to experiment with 4” propellers. 4” props don’t get a lot of love, and that has been a problem. Lots of people fly 3” or 5” props, so there’s a huge selection of props. Since nobody flies 4”, there are only three or four props worth trying, and none are a great fit for what I’m hoping to accomplish.

What was I hoping to see?

I remember the first time I tried 6” props on my 5” quad. It had some fairly powerful 2600 kv T-Motor F40 Pro V2 motors. I figured it wasn’t going to work out well. Larger props need to spin slower, and those high-kv motors had me a little worried.

I quickly learned that it wasn’t a real problem. If my memory serves, I was getting roughly 30% longer flight times compared to 5” props. This was true whether I was doing slow, cruising, long-range-style flights, or punchy freestyle flying.

My 3-inch Kestrel

When flying 6”, you will see a lower top speed compared to 5”, but you’ll gain a ton of grab in the air. If you’re falling out of a long dive, the 6” props can just catch you like nobody’s business.

Math and pi tell us that a 4” prop has a disc area that is 77% larger than a 3” prop, while a 6” prop only has 44% more surface area than a 5”. It is a bigger difference, but I was hoping to see the same sort of changes: longer flight times, more bite on the bottom end of the throttle, and lower top speeds.

Can we build a sub-250-gram 4” freestyle quad with an HD camera? Will flight times be long enough for some long-range flights? Will it feel more like a 5” freestyle quad?

My testing with 6” had me concerned

A bunch of us own an old Bind-N-Fly miniquad from Aurora RC called the BFight 210. We all loved it. I got my first one free as a review unit. I immediately bought another for my nephew. Several friends also bought them. It was always going on sale for $120 or less, and we all bought them during sales. It was a tremendous value.

It wasn’t a speed demon, and it felt terrible if you tried carrying a GoPro. I believe it had 2205 2300 kv motors. New pilots were regularly seeing 9-minute flight times. My record on a long-range style cruise was over 11 minutes. How amazing would the BFight 210 be with 6” props?!

BFight 210

It was terrible. The 2204 motors just didn’t have the power to handle such a big prop. It felt terrible, and flight times didn’t improve. In hindsight, this isn’t surprising. At the time, it was a bummer.

4” props on a 270-gram Kestrel

I missed the 250-gram mark with my 4” Kestrel build, but I know I could bring it down and save a few dollars doing it. I used the beefy Aikon AK32PIN 20x20 blheli32 4-in-1 ESC, and I used a big 1,000 mW VTX. If I switched to a Diatone Mamba F4 20x20 stack, a 200 mW VTX, and maybe pulled back from a 650 mAh to 550 mAh 4S battery, I’d save $40 and easily shave 20 grams off the build.

My 4-inch Kestrel Build

There are tons of 4” props available, but most of them are for airplanes, and many of the rest are ancient, inefficient bullnose propellers. The best props I’ve found to pair with my little EMAX 1606 2800 kv motors so far are the HQ 4x3x3. I’m aware of the new EMAX Avan Scimitar 4x2.4x3 props. I plan to throw a few into my cart the next time I’m ordering miniquad supplies!

UPDATE: I did order some EMAX 4x2.4x3 props!

I have to say that overall, I am mostly pleased with the way my 4” Kestrel build flies. It feels more like a 5” freestyle quad than any 3” I’ve flown. I feel more confident coming out of sketchy split-S maneuvers or power loops that just weren’t lined up well.

That was the good news

Propwash handling is terrible with this combination. Mark Spatz has an excellent video explaining why gentle props on powerful motors make it much easier for your Betaflight to fight propwash, but I can’t seem to figure out exactly which video that is! I have relatively big, heavy props on relatively tiny motors.

Sure, I can fly around this propwash, but I always forget that I need to. I try to fly it like it is my 5”, and that doesn’t work out.

I’m also not seeing any real gain in efficiency. My 220-gram 3” Kestrel with 1306 motors usually manages 4 or 5 minutes of the sort of freestyle flying that I tend to do. The 4” rarely makes it past 4 minutes.

When I’ve purposely taken slow, boring flights with the 3” Kestrel, I’ve pushed past 8 minutes of flight time. I’ve never managed more than 6 minutes with the 4” Kestrel.

That said, I’m willing to give up that extra minute of flight time. My 4” Kestrel feels much more like a 5” freestyle quad than my 3” build!

The Caddx Turtle is just awful

The first obvious problem with the Turtle or Split is that the HD video and FPV video settings are tied together. There’s only one sensor on that camera. That means ISO and shutter speed are shared, and the settings that make the HD feed look reasonable make for a poor flying experience.

The field of view on the Turtle is tiny compared to a GoPro with SuperView. That’s always a disappointment.

NOTE: I’m sorry. I rarely upload Caddx Turtle video, because I just dislike it so much. The video I embedded here looks kind of hokey, I think. Maybe I need to start uploading my vlogs in 60 fps when flying with the Turtle?

The Turtle produces serviceable HD footage when you’re flying slow and just cruising. Once I start doing quick, snappy moves, I’m disappointed with the video. I just can’t get enough motion blur into the image, even with an ND filter. It just looks like a slideshow. I don’t like it.

These cameras are getting better every few months. The Caddx Tarsier and the Runcam Split Hybrid both look like a huge steps in the right direction.

What can we do if 4” props are too heavy?

I’d really like to try a biblade version of the HQ 4x3x3. I even emailed HQ to ask if they had anything like that. The response was confusing, so I’m going to assume this won’t be an option.

I decided to take matters into my own hands. I dropped my heavy vise onto the bed of my Shapeoko CNC machine, and I clamped in one of my old 2306 motors. I positioned the router about 1.75” away from the center of the motor, and I manually cut down some of my HQ 4x4.3x3 and HQ 4x3x3 props.

This worked surprisingly well!

I don’t have a lot of data on 3.5” props

I’ve flown two batteries so far. They weren’t even fresh batteries. They’ve been sitting in my bag at full charge for the better part of a month. They fly just fine, but I don’t feel comfortable comparing efficiency to what I used to see on freshly charged batteries.

These cut-down props are now bullnose props. Bullnose props should be significantly less efficient than a properly designed 3.5” prop. We don’t have any of those to compare with, though. A 3.5” prop has 36% more disc area than a 3” prop, so this is much closer to the upgrade from 5” to 6” props.

I can tell you that the huge propwash problem is almost completely gone. Like with any quad, if I try my hardest, I can definitely coax some propwash oscillation out of the 3.5” bullnose props. I know for sure that I hit some accidental propwash at least once, but it wasn’t as bad, and it would have been easy to avoid.

I’m going to have to do some back-to-back testing. I need freshly charged batteries. I need to fly some 3”, 3.5”, and 4” props. I need to fly more than one battery on each prop, too.

In any case, I’m pretty excited.

Shaky video on my 4” Kestrel

I’ve been cutting Kestrel frames for my friends, and I don’t really enjoy spending a ton of time in the garage cutting carbon fiber; it is too hot out there!

That means my two Kestrels are built using my oldest parts. Most of the magic on the Kestrel happens where the bottom plate meets the rubber suspension. I have to size that tab just right. Too small, and it just wobbles around. Too large, and the suspension doesn’t absorb vibration. This has been tweaked a bit on almost every bottom plate I’ve cut.

On top of that, I’ve also redesigned the bottom plate to make it more rigid. Of course, my two Kestrels use old bottom plates. My tabs aren’t quite the right size, and my bottom plate is much less rigid.

I noticed that my 4” Kestrel’s fuselage can be twisted quite easily. I figured my less-rigid bottom plate was weakening in all my crashes, and it probably is, but I also learned that the McMaster-Carr grommets get soft and deformed over time. I swapped some new grommets in, and that helped a lot.

The Business End of the Kestrel Frame

It is still looser than I would like.

Here’s the bummer. I swapped out the grommets and swapped from 4” to 3.5” props at the same time. Did the stiffer grommets correct the problem? Are my 3.5” props just a little unbalanced? They have to be a little out of balance, right?

I’m due to cut myself some up to date bottom plates. I’m just not looking forward to disassembling the entire Kestrel to replace one plate!

9 months flying HD micro freestyle quads

In many parts of the world, there’s a 250-gram weight limit on model aircraft. I’m not too worried about this today, but it sure seems like the same sort of rule will be coming here, too. I think it is prudent to be testing the waters.

I also love the idea of having a hold-my-beer quad. When I’m flying my 3” Kestrel, I can record HD footage, and everything in the air costs around $250. That’s including the battery. That’s somewhere between the cost of a GoPro HERO5 Session and a HERO7 Black.

Sure, the quality isn’t nearly as good as a GoPro, but I also won’t feel as bad when my Kestrel gets stuck on a roof or sinks to the bottom of the ocean.

That seems to be the only time I would really want to fly one of my 3” or 4” micros. My 5” Falcon freestyle quad flies better, records better footage, and I’m rarely worried about the possibility of losing the whole thing.

On the other end of the spectrum, if the spot that I’m flying isn’t a good fit for my 5” freestyle miniquad, I’m probably not going to fly a 3” either. There’s a much better chance that I’ll be monkeying around with my minuscule EMAX TinyHawk Freestyle if there’s likely to be people or delicate property nearby.

I keep saying that things are constantly improving. By the time the United States has a 250-gram weight limit, maybe the successor to the Caddx Tarsier will be as good as my GoPro Session. I’m sure Betaflight will continue to improve. Motor and prop selection for micros will only get better.

Until that time, my 3” and 4” Kestrels will be relegated to occasional flying.

Is the rubber suspension required? Is it even helpful?

This is the real question. I decided to use the Acrobrat-style suspension on the Kestrel, because it sounds like an excellent idea. Does it really help?

My honest answer has to be that I have absolutely no idea! Maybe there should be a 3” and 4” version of my open-source Falcon frame? That would be a good way to test the effectiveness of the suspension.

The Kestrel's Suspension

I hope that the suspension is helpful. Maybe a fresh build with brand new props doesn’t need the rubber bushings at all, but what happens when you bump a tree? Will the bushings save your footage?

If the bushings would save my footage after some slight prop damage, they’d be worth the additional hassle!

Hardware problems in my 3” and 4” Kestrels

I broke my 3” Kestrel a long time ago. I got stuck in a tree, and had to use turtle mode quite a lot to wiggle it loose. It was stuck quite well, then it fell down a few branches, and got stuck again, and then a third time. When it finally hit the ground, the Caddx Turtle was dead. It wasn’t dead when I started my attempt to recover the poor thing.

It hasn’t flown quite right ever since. It’ll fly OK if I add a ton of filtering, so I haven’t made the effort to fix it. The new revision of the Diatone stack is only $38, but I didn’t really want to take everything apart and resolder every connection!

Last week, an ESC on my 4” Kestrel failed. This is both a surprise and a bummer. I chose a relatively expensive and heavy ESC board for that build. I figured that an ESC that folks are using in 5” racing builds with 2207 motors ought to be bulletproof on my tiny 1606 motors. It wasn’t.

The smart, frugal thing to do would be to replace the ESC board with the little Diatone ESC. I’m not going to do that.

I ordered a pair of Diatone Mamba stacks, and I’m going solder them into both my Kestrels next week. Sure, the Diatone F4 flight controller is a downgrade from the F7 board that is currently in the 4” Kestrel, but I like the idea of them running the same inexpensive hardware.

I’d like to be able to point to either of them and say that you could build either for around $250 or less!

I’ll use this repair opportunity as an excuse to cut new bottom plates for my Kestrels. I have the oldest prototype plates in mine, and they have extra material cut out to make them lighter. That also makes them quite a bit softer. It is time to bring my own builds up to match everyone else’s!


I’ve used quite a lot of words just to explain that I’m excited about trying 3.5” props. That’s really all I’m here to say today. I’m excited about 3.5” props, but I don’t have much solid data to give you at this point. I’ll fly some more over the next week or two, and we’ll see what I find out!

What do you think? Have you tried 3.5” props? Are you flying 3” or 4” props? Do you think splitting the difference is interesting? Let me know in the comments, or stop by the Butter, What?! Discord server to chat with me about it!

Slow USB Flash Drives Are All Right As Long As They Are Cheap

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I’ve been doing my best to post quality deals over at Butter, What?!, and several of those deals have been extremely cheap USB flash drives and microSD cards made by Silicon Power. After posting those deals, I noticed that a few of the folks over at /r/buildapcsales are really upset about Silicon Power’s USB flash drives.

As stated on their listing on Amazon, these flash drives have a USB 3 interface. However, the product listing also states that the drives only manage read speeds of 70 megabytes per second and write speeds of a measly 5 megabytes per second.

Presumably, this is because Silicon Power is using old, cheap flash chips. I ordered a pair of the 64 GB drives for $9.99. My tests showed 40 megabytes per second on reads and 19 megabytes per second on writes. That is a good bit faster than USB 2, so these drives are benefiting from the USB 3 interface. They just aren’t benefiting all that much.

Slow drives are just fine, especially when they’re cheap!

When I was young, we used to trade 5.25” floppy disks with our friends. They might bring a save game over to our house, or I might send them home with a copy of the game I just bought. The polite thing to do is bring your own floppies, right?

That didn’t always work out. I was often scrounging around the house for an old, dilapidated floppy disk that could be sacrificed. You didn’t want to waste one of your good disks on an inconsiderate friend!

Skip ahead 10 or 15 years, and we’d be talking about CD-R discs instead of floppies. Skip another 10 years to today, and we’re talking about USB flash drives.

If I discover that I need to send you home with two seasons of a TV show that you just can’t stream from anywhere, I’m going to throw it on a USB flash drive.

You don’t have a USB flash drive with you?! That’s just fine. I’m going to throw it on one of my slow $5 drives. If you forget to return the drive, it is no big deal.

What else do we use flash drives for?

I use mine for small, occasional backups. Sure, most of my backups are stored in the cloud, but there are a few things that I like to keep on hand locally. Specifically, I store a backup of my Bitwarden password vault, my ssh keys, and my GnuPG keys on a flash drive. Slow is fine for this, because the data is so tiny.

Every once in a while, I need to create a bootable USB flash drive. Most of those times, I’m only copying about 700 megabytes onto the flash drive. Even on a slow drive, that will only take a minute or two.

What would I use a fast, expensive USB flash drive for?

I’m struggling to come up with a use case. I don’t even own any fast flash drives. The arrival of Dropbox and similar services probably put the last nails in the USB flash drives’ coffin for me. Why run around with data in your pocket? All my data magically shows up on every computer I own automatically.

Maybe you haven’t caught up to the rest of us. Maybe you’re still manually copying files around and running them from one place to another. I’d rather see you get on board with the convenience and simplicity of file sync than see you buying lots of fast USB flash drives!

The Silicon Power 128 GB USB flash drive made me sad

They aren’t the only manufacturer that I should be picking on. I’ve posted a deal on a slow Kingston drive in the past, too. However, there’s a Silicon Power flash drive that I really want to pick on, though.

Their 128 GB USB 3 flash drive was on sale for $9.99 with free Prime shipping. That’s about as good of a deal as the 2-pack of 64 GB drives from the week before. I almost posted it on Butter, What?!

I couldn’t find anything in the product description about actual transfer rates. There’s a bunch of talk about the huge speeds of the USB 3.0 bus. They might even be implying that their drive is going to make good use of those speeds. There’s no mentions of tested, real-world transfer rates.

There are plenty of customer reviews talking about how slow these drives are.

This is disappointing. I’m happy to buy something that is slow, as long as you tell me about it up front, and the price is right.

In this case, the price is right, but the advertising is deceptive. I don’t like that.


I’m going to keep posting these sorts of USB flash drive sales to Butter, What?!, but only if the product descriptions are honest. I can’t keep buying them, though. I believe I’ve bought every flash and microSD deal I’ve posted so far. I’ll probably buy one more pair of cheap USB flash drives, then I’ll have to stop for a while. My collection is getting too big!

What do you think? Do you agree with me that cheap, slow flash drives are a good value? Do you prefer faster drives? What are you doing with them? Let me know in the comments, or stop by the Butter, What?! Discord server to chat with me about it!

I Competed In My First Drone Race!

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We have an active and awesome MultiGP chapter here in Dallas, and their field is just a 25-minute drive from my house. I’ve been invited out to their races before, but I never managed to make it out. I know from the days when I used to occasionally take my car out to the local drag strips that organized racing isn’t really my cup of tea.

A few weeks ago, Brian and I drove across town to go flying with Alex Vanover. He convinced us that we should go out to Carrollton for some drone racing. I went out that Friday to spectate, and I decided I should give it a try, so I signed up to race the next week.

Even just spectating was fun

I got to see some fast racing quads, and I had the opportunity to meet some cool people. We told some folks about our favorite, secluded flying spot here in our neighborhood, and we had three or four new friends show up for some freestyle flying with us the next day. That was awesome!

The fine folks at Dallas Drone Racing had a couple of televisions set up along with a projector. The screens were all showing a grid of FPV feeds, so even if you don’t have your own equipment, you can still see what the pilots are seeing.

I brought my Fat Shark goggles. They gave me a better view of the action, but they definitely weren’t required.

I’ve always avoided racing, because I dislike all the organization that is required. You’re always waiting for your turn. Everyone flies in a certain order. When your next turn comes up, you had better be ready; you can’t just let someone go ahead of you and just take the next spot.

Half of the participants were just there to have some fun flying and hang out with their friends. They’re doing exactly what my friends and I do when we fly at a park, except they get called up to run a few laps every once in a while. It’s not that much different than what I’m already doing!

Racing isn’t quite like I expected!

In the past, my friends and I have set up children’s soccer goals with the nets cut out and used them as drone racing gates. They’re not much higher than your waist, and not all that much wider than they are tall. The MultiGP gates are huge. I bet you could drive a Miata through them.

My brain didn’t want to understand the scale of the track. Compared to the places where we usually fly freestyle, the entire track was tiny. Something about the length of the track combined with these big, honking gates just doesn’t compute for me.

I broke my first quad before finishing a lap!

There’s more than a little hyperbole in that statement, and it was totally my fault due to lack of testing. A few days before the race, I broke the Immortal T antenna on my favorite quad’s Crossfire Nano module; that poor thing has taken such a beating over the last 15 months!

When I got home that day, I replaced the antenna. I put the quad in one corner of the house, and I wandered around the house with my radio. I had perfect signal all throughout the house, so I figured I’d be in good shape. I figured wrong.

I bumped one of the inflatable gates during my first lap, and I fell out of the sky. I tried to use turtle mode to flip back over, but I just couldn’t arm the quad. I noticed that my link quality was reading 7. The antenna wasn’t the only problem with that Crossfire Nano!

No big deal. I had two more quads in my bag. It was just a bummer that I missed out on my first three practice laps.

I need way more practice

I knew my fingers were shaky the entire time. I didn’t think they were shaking as much as the first time I flew down in our little creek near the house, but listening to my GoPro footage makes me think otherwise. I wonder how many times I’d have to go out racing before that will stop?!

Speaking of GoPros, I’m pretty sure I was the only goofus flying a heavy freestyle quad with smooth, gentle freestyle props, and carrying a GoPro. I was also the only pilot with GPS. The best I managed was 57 MPH on the long straight through the finish line. I’m curious how fast the really fast pilots were going!

The gates are big, and once I got used to the scale of the track, they weren’t too hard to hit. The problem I had was with puzzling out which gate to aim for next. There were two parts of the track that I miscalculated almost every time.

At one of the two-story gates, you were supposed to go through the top part, S-turn and reverse through the bottom, then do about a 180-degree turn to the right to line up for the next gate. My eye liked to catch one of the inflatable flags, and I would accidentally aim for that flag instead of the gate.

I had a similar problem at one of the other double-decker gates. By the time I realized my mistake, I’d be way out of line for hitting the next gate. That isn’t so bad, because I could still manage to make it through the right gate. The problem is that the weird line I was on would leave me going in mostly the wrong angle when coming out of that next gate.

I did better and worse than I expected

That first night when I went out to spectate, I formulated some opinions. It looked like those big gates would be easy to fly through, and I anticipated that I would be able to compete with 1/3 to ½ of the pilots that I saw flying that night.

The gates were easy to hit, though I did bump into more than my fair share. The race I competed in was the final race of the Mission Food series, and I get the feeling that things were a little more competitive than the race I spectated. I think the course was a little meaner, too.

I had several laps around 45 or 46 seconds, and my best lap was just over 42 seconds. I had some laps at just over 60 seconds even when I crashed and had to flip back over. The lap timer failed to call out my times pretty often, too.

I even did better than I thought!

I was going to tell you that I failed to string together three of those 45-second laps into a single race, but I’ve learned that that isn’t even true!

On my final race, the robot that announces lap times read out 1:36 for my first lap. I remember thinking that this sounded awfully high, but I just pushed ahead. I crashed on my last lap, and I bent a prop badly enough that I couldn’t take off.

As it so happens, that lap reading was incorrect. According to my GoPro footage, I did complete three laps at 0:48, 0:45, and 0:42. I crashed on my fourth lap. That’s the lap I wasn’t supposed to be taking!

I’m much more proud of this run than I thought I was!

Just because I was finished doesn’t mean everyone else was done!

I got knocked out rather quickly. I believe I got to squeeze in three practice runs that should have been about three laps each. When I moved on to the heat I was actually competing in, I didn’t really fly any differently. As far as I was concerned, I was still practicing!

There was plenty of racing to watch after I got knocked out of the competition, and it seemed like every race was over faster than the one before.

Would I do it again?

Sure! I don’t think I’d want to race every week, but it’d definitely be fun to do on occasion. Drone racing is something I should get better at. I’m certain that if I were a better racer, then I would also be a better freestyle pilot.

I’d definitely be willing to go out to spectate more often. There are a lot interesting and friendly people at the local drone races. It is fun to see what sort of quads they’re flying, what sort of hardware they choose, and just generally see what they’re all up to!


If you’re flying FPV, you should find your local MultiGP chapter and stop by to see what they’re up to! I had a lot of fun, they’re a great community, and there’s a lot to learn from them, especially if you’re new to the hobby!

Are you already participating in drone races? How do you think I did on my first time out? Are you an FPV pilot somewhere in the vicinity of Dallas, TX? Let me know in the comments, or stop by the Butter, What?! Discord server to chat with me about it. Rarely a week goes by that we don’t organize a small flying meet-up in Discord. Maybe you’d want to join us?!

Spending an Afternoon Flying with Alex Vanover

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We had an awesome and extremely interesting experience this week. Brian and I got to spend an afternoon flying miniquads with one of the fastest FPV drone racing pilots in the world.

How this came about was rather curious. It was my birthday a few months ago, and I can only imagine that I’m quite difficult to shop for. I’m one of those terrible people that immediately buys just about everything I really want.

My Falcon Frame

We already knew that Alex Vanover lived somewhere nearby. Brian’s wife, Julia, noticed that he had an hourly rate listed somewhere on the Internet. I guess that you could pay Alex to work on your broken miniquads. For all we know, he posted this information a few years ago and completely forgot about it.

Julia told him that we didn’t need anyone to work on our quads. She just wanted to know if she could hire him to fly with us. I have absolutely no idea how that conversation went, but a couple of months later, Brian and I found ourselves in the car driving out to a small airstrip on the other side of the metroplex to meet up with Alex Vanover.

Meeting Alex Vanover

The Dallas/Fort Worth metro area is rather large. Brian and I left Plano at around 2:00 p.m., and we headed west. About 30 minutes into our journey, we were nearly driving through our old neighborhood in Irving, where we lived nearly 20 years ago. About ten minutes later, and it felt like we were leaving civilization.

After another 15 minutes passed, we were making our way slowly through the roadways surrounding a small airstrip. Google Maps had us off course by one street. We could see Alex just off in the distance. He was carrying a big racing flag out to the end of the field; we could see he was in the middle of setting up his practice track.

Vanover is an interesting guy. He’s 19. He’s an amazing freestyle pilot. He lives in a hangar at an airport. We were standing next to the field where he put in most of his huge number of hours of practice that made him into one of the fastest drone racing pilots in the world. How cool is that?!

We introduced ourselves, and Alex asked what sort of flying we wanted to do. We quickly decided to drive to a nearby park for some freestyle flying.

I have to wonder what Alex was expecting

I’ve seen videos of drone racing. I’ve seen what the DRL tracks look like. I’ve never actually attended an actual drone race.

I assumed Alex would be expecting us to be hardcore drone racing fans. At worst, I figured he’d expect us to act like my mother would when she ran into the local TV weatherman. You wouldn’t have wanted to be that weatherman!

Later, I gathered that he expected us to have quads that flew poorly. It sounds like that’s fairly common, and I bet it is more likely to be the case when someone is actively looking for help.

I’m not good at PID or filter tuning. If I have a machine that is flying all sorts of wrong, the best I can do is take guesses to try to get it flying better. I do understand the settings well enough that I can take a quad that is flying OK and make it fly a little better, though.

What did we actually do?!

The three of us sat at a picnic table, we took turns flying, and we talked a lot. This is pretty much what I do every time I go flying with friends. Why should it be any different when hanging out with a professional?

The first thing Alex took up with his 5” racing build. He flew it using one of my brand new 1,000 mAh 6S packs. He told me that he’d feel bad if he smoked my brand new battery, but I told him to do his worst. I got these oddly shaped batteries on sale for $18 each last week. Killing one wouldn’t be a big loss, right?!

Watching ridiculously fast racing footage on YouTube is one thing. Seeing a professional racing pilot blast around under the trees at full throttle less than 10 feet away from you is a very different experience! If I were smart, I would have at least gotten DVR footage of that run. Unfortunately, I’m not that smart.

He discharged my battery in less than 2 minutes, and it was a ton of fun to watch. The difference between my casual flying and the flying of a pilot that runs through 100 batteries a day while practicing is nothing short of astonishing.

I think I flew three batteries. I’m pretty sure Brian only flew one, but it was the most impressive contiguous five minutes of flying I’ve ever seen him do. Alex put a few batteries through a DRL Racer 4, and he put one battery through my Falcon build.

That last part had to be my favorite. Watching a skilled freestyle pilot do things that I simply can’t do using my own machine was awesome. Not only was he flying the quad that I fly every day, but Alex was flying a frame that I designed.

Alex had nice things to say about my quad, my frame, and my tune. I even have some of the kind words on video! I wouldn’t feel right publishing any of that video. It is just the tail end of flight footage on the GoPro. I don’t know that either of us realized any of the words would have wound up on a recording.

I don’t want the world to get the mistaken impression that my open-source frame is awesome just because Vanover said nice things to me about it, especially when neither of us realized he was still on camera.

That said, it was nice to hear praise from a professional.

I need to fly with better pilots more often

This is the most important lesson I learned while flying with Alex Vanover. He didn’t explicitly give me this advice. He’s only seen me fly one afternoon. For all he knows, that’s exactly the way I fly every day.

It isn’t. I know I pushed myself a little harder. Sure, I did the same boring thing I do every time I fly at a new park. I spent most of my time doing split-S maneuvers over all the trees. It is an easy, safe move.

Who am I kidding? I do the same thing at the abandoned golf course where I fly every single week!

There was a particular cluster of trees Alex showed us while he was flying the DRL Racer 4. There’s a rather large and mostly vertical gap in the center of the cluster. I explored the gap, then I did a tall power loop over those trees. I wasn’t lined up, so I aborted.

Vanover said, “Ah! It looked like you were going to go for the gap!”

I don’t think I have the skill to have lined up the gap from that angle, but I did go right back in and try again. I would have taken another pass at it even if Alex hadn’t egged me on. I lined up the power loop again, dropped down through the gap, and I smashed directly into the base of the largest tree trunk on my way out!

It was no big deal. My battery got ejected, I broke the hub of an Ethix S4 prop, and broke the tip of another prop. I replaced the props, loaded a fresh battery, and I tried again. That attempt went much more smoothly.

I was definitely more aggressive than I would normally be at a brand new park, but I was also being cautious. I like the title of this blog post. Can you imagine if I had to use the title Spending an Afternoon Getting My Quad Out of A Tree With Alex Vanover?

I would say Brian was similarly encouraged. You should check out his flight video, too.

You should book a flying session with Alex Vanover!

We asked if he’d like to do this sort of thing more often. We probably asked twice. If this was just a weird, one-time thing, I might not have even written about it.

Alex said that he would like to do this sort of thing again. I also know his schedule can be hectic. I don’t know exactly what he charges. This was a birthday present, so I’m not supposed to ask that sort of thing. I have a rough idea, though, and I don’t believe he charged us enough.

The most comparable event I can think of is Kwad Camp. I know how much Kwad Camp costs. Sure, Kwad Camp is a much longer event, and there are more pilots to talk to, but you’re also competing with more than a dozen other people for their time.

More importantly, those pilots aren’t Alex Vanover. Sure, the guys at Kwad Camp are great pilots, and they all seem like good people. They’re not racing on television. They’re not one of the fastest pilots in the world.

I have nothing but flight footage

I brought my Osmo Pocket, but I didn’t use it at all. I wanted to have a good time. I didn’t want to use the afternoon as a vlogging experience. Alex didn’t really sign up to be some sort of guest on my YouTube channel, and I wouldn’t even have wanted to ask him to.

I have no pictures, no videos, and no selfies.

I just wanted to have fun. Just like I do every time I go out flying with friends. We spent more time chatting than flying. Just like when I go flying with my friends.

After the flying session

After we were packed up and heading to the car, we invited Alex to grab some dinner with us. Brian and I had to eat on the way home anyway, and it would have been rude not to extend an invitation. I figured there was a 50/50 chance that he would decline the invitation.

On one hand, we probably already used up more time than he had been paid for. On the other hand, everyone has to eat.

There really wasn’t a lot of food close to the park. We wound up stopping at Wendy’s. I heard a rumor that you can get a Frosty there!

What do you do at dinner? You exchange stories. Brian and I mostly had stories that you probably wouldn’t care about, especially if you’re here to read about drone stuff. The only thing relevant to this blog that the two of us talked about were the quadcopter build classes we hosted at Plano’s Makerspace.

Alex had fun and relevant experiences to share with us. We learned more about Rotor Riot’s trip to Croatia. We got some behind-the-scenes information about how Alex lost his quad and GoPro while flying at the Game of Thrones castle. We got to hear some interesting stories about DRL. Now that I’ve met a DRL pilot, I’m going to have to tune in to see what it is all about!

Alex invited us out to come check out the Mission Foods drone race in Carrollton tomorrow night. I plan to attend, but I’m worried that it is going to get rained out!

Wrapping up the day

We took the ten-minute drive back to Alex’s hangar. On the way back, we chatted about the weather; it seemed like quite a mild day for Texas sitting in our spot in the shade. We talked about growing up in Texas, what it is like living out of the way at an airport, train derailments, and our almost complete lack of abandoned buildings to fly at around Dallas.

While driving past the runway, I pointed while wondering why the end of the roof straight off somebody’s porch was sitting next to the runway. Alex was kind enough to explain to me that the tetrahedron was a wind indicator.

We drove past Vanover’s practice track and pulled into his driveway. We had three identical ThinkTank backpacks in the car, so we had to make sure Alex didn’t take the wrong one; I’m not sure which one of us would be more disappointed if that happened!

I fished out one of my prop tools to leave behind with him, we exchanged pleasantries, and before I knew it, Brian and I were driving away.


Alex is an interesting guy. I would say that he’s almost exactly what I expected. He’s friendly, knowledgeable, and polite. He’s very excited about what he’s doing, and that’s always fun to see. He’s had some awesome experiences, and he’s only at the very beginning of his journey.

If you’re thinking about hiring Alex to fly with you, to help you with your miniquad hardware, or to have him help you become a better pilot, I would highly encourage you to do so!

My Thoughts on Open-Source Hardware

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I happened to watch Thomas Sanladerer’s video about designing a replacement part for his MPCNC build. I can’t stop thinking about it.

This situation is fascinating to me. A lot of the discussion floating around the Internet about this seems to involve the motives of one or both parties. That’s interesting, too, but I want to steer clear of that side of things.

I have my own open-source hardware designs. I’ve thought about having some of them manufactured. I’ve put a bit of thought into the licensing, and what that licensing protects me from and allows end users to do. I’ve also put some thought into the viability of marketing my potential products.

Your copyright and license protect your design, but not your hardware

If you’re Apple or Ferrari, this isn’t quite the truth. They have huge budgets and top-notch legal teams.

You, me, Thomas Sanladerer, and Ryan at V1 Engineering don’t have this luxury. I doubt any of us could afford to fight in court over these minor details. For us, the copyright protects our designs but not the hardware.

If I feel that the shape of the fuselage of my Kestrel is an important part of my marketing, I had better have filed for a trademark. If you decide to cut something similar, I won’t have the power to stop you.

Even if you are cutting the carbon fiber using my open-source CAD files, I don’t believe I would be able to stop you from selling what you have manufactured. I don’t believe that the copyright of my CAD files could be applied to the product that’s been cut by your CNC machine.

You don’t need our CAD files to copy our designs

With my quadcopter frames, all you need to do is buy one frame and drop the physical parts onto a flatbed scanner. You don’t need my design files at all.

My 3-inch Kestrel

Even if you did need to redesign the parts manually, that isn’t a gargantuan task. If Thomas Sanladerer can create a parametric part that is compatible with the MPCNC in a few hours, then maybe the design isn’t really all that valuable.

We aren’t entitled to profits

I would love to have my breadboard vise manufactured. It is a 5-hour 3D-printing job, so to sell them, I have to charge quite a lot for 25 cents worth of plastic. You shouldn’t buy one from me. You should print your own!

I’m excited about my 5” freestyle miniquad frame, but I don’t think I’ll try to have it manufactured. Sure, it is precisely the frame that I want to fly, but it just uses my favorite ideas from a bunch of existing frames. You should just buy one of those.

I think my 3” Kestrel frame is unique enough, but I don’t think the market is big enough to justify the effort and investment of acquiring inventory. I’ve seen how big the third largest FPV quadcopter store in America is, and it isn’t big at all. Micro quads are currently a niche within a niche, and I’ve heard a bit about the volume of electronics being sold for custom 3” builds, and it seems to be quite low.

Even if I had locked up all this intellectual property of mine as tightly as I could, I don’t think I’d be making any serious money with any of this stuff.

You aren’t entitled to our designs

I think everyone is already aware of this, but I still think it is important to bring it up.

When I started my journey into the world of CNC, I quickly learned how much different the CNC community is compared to the 3D printing community. Open-source is everywhere in the 3D printing world; most of the best slicers, models, and 3D printer designs are open-source.

Open source CAM software for CNC machines is light-years behind open source slicers. When you search for beginner CNC projects, half the search results are people asking how to make money with their machine. The landscape is just so very different!

Low-cost alternative suppliers may help you make money

Twenty years ago, everyone was stealing copies of Microsoft Office and Windows. Microsoft had no interest in stopping you. Every home user of Office was another advocate for the use of Office at the workplace, and businesses did pay. It was only in recent history that Microsoft really started clamping down on this sort of piracy.

The Arduino is another example. You can buy a genuine Arduino Uno for $22 plus shipping. You can buy a more advanced Arduino Leonardo clone with free 2-day shipping from Amazon for $9.99. You can order similar boards straight from China for half that price.

There are plenty of people willing to pay the extra $12 to $15 to support the original. The people that buy the clones for $5 to $10 are still helping to grow the size of the Arduino ecosystem. Everyone wins.

Would Arduino be making more money if they didn’t open-source their design and software, and if they kept the cloning at bay? The number of projects using an Arduino would be smaller, for sure. Maybe they’d be doing OK, but I doubt it.

Would you rather take 100% of the profits from a small project, or 20% of the profits from a huge project?

Open-source hardware can reassure your customers

I’m just a guy cutting carbon fiber in his garage. If I do decide to have my Kestrel frames manufactured for me, and you decide to fly my frame, how do you know replacement parts will be available a year from now? My product may be a flop, and I can never have a second batch produced. Maybe I’ll go bankrupt. Maybe I’ll get hit by a bus. Anything can happen.

I want my customers to know that they can produce their own replacement parts if need be. If I go bankrupt, maybe another company will step in to fill the void. Maybe my customers could have a friend cut some carbon fiber for them. Maybe they’ll order parts from CNC Madness using my CAD files.

The Arduino enjoys a similar advantage.

What about the MPCNC?

I like the MPCNC project, but it isn’t for me. If V1 Engineering had an account at Patreon, I would subscribe without hesitation, but I have no interest in buying their product or building this machine.

The kit looks tempting at only $275. The recommended spindles are much smaller than what I run on my Shapeoko. The two recommendations are priced at either $53 or $109 at Amazon. You’ll need to source $12 worth of conduit, and you’ll need to run about $30 worth of filament through your 3D printer.

V1 Engineering sells the 3D-printed parts for $135, and I think that’s a great value. The time and effort to print your own parts isn’t inconsequential, not to mention the potential reprinting of failed parts. I would definitely spend the extra $100 or so to have that work done for me.

That’s under $550 for a machine that is roughly comparable in size to a $1,680 Shapeoko XL. I’d even be willing to bet that the MPCNC could handle almost every cutting job I’ve attempted on my Shapeoko XXL.

That said, the MPCNC won’t begin to approach the rigidity or power of my Shapeoko XXL. They’re different machines for different jobs at different price points.

MPCNC STL file licensing

The STL files for the MPCNC are licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. As with many open-source licenses, this means that any changes you make to these STL files must also be released under the same license. You’re also not allowed to profit from the sale of those STL files.

Whether you’re allowed to sell the parts you print using the STL files could probably be argued either way. I don’t really want to touch on that part of the discussion.

What I do find interesting is that this license cuts both ways. If anyone published an improvement to the MPCNC STL files, and V1 Engineering wants to integrate those changes, then V1 Engineering has to follow the license as well. V1 Engineering doesn’t own the copyright to those new changes, so they can’t sell those changes, either. They’d have to obtain permission from the copyright holder of those new changes.

I don’t know how this is being handled today, but I could see this creating a schism at some point in the future.


I hope I wasn’t too hard or too easy on either Ryan at V1 Engineering or Thomas Sanladerer. I wanted to explain the research I’ve done and the thoughts I’ve had regarding open-source hardware over the four years since I published my breadboard vise to Thingiverse.

What do you think? Do you prefer to use open source hardware? Have you published any of your open hardware projects to the world? Do you have a project I should know about? Let me know in the comments, or stop by the Butter, What?! Discord server to chat with me about it!

What Happens When Brian and I Start Another Blog?

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About four months ago, Brian Moses and I started another blog. We decided that this was a good idea almost two years ago, but life and procrastination got in the way. Near the end of April, I said to hell with waiting and planning. I decided I was just going to stand up a nearly empty, completely undecorated Jekyll site.

That right there is the most important piece of blogging advice I could give anyone. Stop waiting. Write something now. Post it on the Internet. It doesn’t matter what it looks like. It doesn’t matter if your theme is perfect. It doesn’t matter what blog engine or theme you choose. The sooner you post your words, the sooner Google will find them, and the sooner people will start reading them!

What were our plans for Butter, What?!

I think I covered out plan pretty well on the first blog I posted on Butter, What?!, but I can cover the basics in a short paragraph or two.

We wanted a place to post content that just wouldn’t fit on or Just about everything I’ve ever written on has involved some amount of research or testing, and some sort of value that I’ve personally added to the topic.

I wanted a place where I can just write a paragraph or two simply explaining why I think something is interesting or cool, and then give you links to the content.

We also wanted a place where we can collaborate, and not just with each other. Brian and I also want to collaborate with other bloggers and content creators, and we want to use whatever social media and Google search clout that we might have to help promote other people that are doing interesting things.

A rising tide raises all ships

Maybe there’s a limit to just how much love Google search will give and Ever since Google started shifting their search results more heavily towards YouTube videos and gigantic websites, our traffic has taken quite a hit. I’ve been hovering at right around half the traffic I used to see roughly two years ago. I don’t want you to think I’m unhappy about this, but I’m certainly not excited about it!

If Brian and I split off some of our time to write content for Butter, What?!, would we see less traffic on our own blogs? Would Butter, What?! drive some traffic back in our direction, or will it just be a one-way street leading out of our sites and into Butter, What?!

A rising tide raises all ships. At least, that’s what we are hoping. Butter, What?! is just getting out of its infancy stage, but it seems to be working. The traffic at isn’t dropping, and I’m seeing a trickle of traffic coming to from Butter, What?!

Here’s a real piece of data. According to Matomo, I saw 53 confirmed visits referred from Butter, What?! in August. Any of my blog posts that rank between my top 30 and 40 would see roughly as much traffic. This is definitely a good start!

Our real goal is to help more than just our two old ships and the S.S. Butter, What?! Now that Google is starting to notice us, it might be time to start reaching out to other bloggers!

I remember when I started blogging at

I bought right around the turn of the century. For a decade, just about the only thing on the site was the animated gif of my spinning head. In 2009, I started blogging and set up Google Analytics. In 2012, I switched from Google Analytics to Piwik, then sometime later the open-source Piwik project changed its name to Matomo.

In the early days of my blog, I was excited when I saw 10 visits in a day. When I would write a new post, I would double or triple my page views for the day just by Googling my own site to find URLs to include in my new blog post. About a year later, I was seeing 50 visits each day, and I was no longer capable of significantly skewing my own reporting.

I don’t have easy access to all my historical data, but I remember that for a long time my search traffic was doubling every six months. It wasn’t a steady rise, though. It would be pretty level most of the time, then it would suddenly take a jump towards bigger and better numbers. Brian’s results were similar, and it took quite a while for this to plateau.

We’re at the point today where the traffic graphs for Butter, What?! are looking like a hockey stick. We don’t have a ton of content written yet, so I expect we’re nearing our first plateau, but we don’t know for sure!

How much traffic is Butter, What?! seeing?

The new blog went up on May 2, 2019. Traffic from Google was pretty much a dial tone until the middle of July. Until then, nearly 100% of the traffic to Butter, What?! was a result of our tweets, Facebook posts, and links from our existing blogs.

Traffic from Google was still extremely tiny in July, but it was finally a steady trickle. Before the month was over, we were seeing 10 clicks per day from Google search.

Butter What Matomo Data

I started to get excited at the beginning of August. Butter, What?! had almost twice as many search clicks in the last week of July as it had the entirety of the previous three months. I was excited, even though we only saw 60 clicks that week. I was excited, because the numbers were still growing every week.

Today, we’re seeing 30 to 40 search clicks per day, and it looks like that number is still increasing.

August was the first month that Butter, What?! broke 1,000 visits. We had more visits referred from Google search in August than we had total visits in July: 686 vs. 581. August was exciting!

The quality of traffic is better than I expected!

Brian and I are always looking at metrics like average visit duration and average time on page. Visit duration tends to be higher when you have a lot of relevant and related content. Google might point you at, because you’re interested in my virtual machine host. Then you might see my blog about my 20 gigabit-per-second Infiniband setup, so you’ll stick around to read that.

Butter, What?! is young. It doesn’t have a ton of content. A lot of the content that it does have is designed to point you towards other content, like those YouTube videos I post every Monday. I expected we’d see a lot of short visits, but that hasn’t been the case.

Butter What Matomo Data

I haven’t checked Brian’s Matomo data, but most days, Butter, What?! has an average visit duration nearly double what I’m seeing on!

I imagine that has more to do with having over 300 articles, and most of those posts are getting quite old. If you manage to click on a blog post about an old Android phone that I owned 5 years ago, you probably got here by mistake, right? You’re going to leave quickly!

Our old blogs also do a much better job of making our other content available to our readers: recent posts are listed in the sidebar and related posts are listed at the end of a post. Butter, What?! doesn’t have any of that yet, and this is another reason that I’m surprised that our time on site has been so high and our bounce rate has been so low.

Traffic is light, but not insignificant!

If this were 2016, the 1,001 visits Butter, What?! had in August would have felt completely inconsequential to me. It isn’t 2016 anymore. Brian and I have had our search traffic drop by nearly 50% since then.

Those 1,001 visits are right around 4% of the combined traffic of and Even if things don’t improve, the search traffic alone from Butter, What?! will account for 5% of our total traffic in September.

If Butter, What?! accounts for 10% of our traffic by the end of the year, I will be quite pleased with our efforts!

What will next month look like?

If search traffic levels off, then September will compare to August in much the same way that August compared to July. We’ll see more search clicks in September than we saw total visits in August.

Butter What Matomo Data

Google’s search console says we’re leveling off. We have roughly the same number of search impressions this week as we had last week, but our click-through rate is up from 3.5% to 4.5%.

Brian and I haven’t been doing as good of a job at posting and reposting our new Butter, What?! content on social media lately. I feel better about relying on search traffic anyway, but I’m going to try to do a better job at this in the near future.

UPDATE: What did the next month (September) look like?!

I don’t think one month’s additional progress warrants a whole new blog post, but I do think it is worth posting an update to let you know how true my predictions turned out.

Butter, What?! saw 2,111 visits in September with 1,786 of those visits coming from Google. That’s twice as many visits as we say in August, and search traffic is 2.5 times higher.

Search Traffic for September 2019

In August, Butter, What?!’s traffic accounted for about 4% of the combined traffic of our three blogs. In September, that number rose to nearly 9%.

I’m quite pleased with these numbers.

I don’t expect the increase in traffic to be as big in October. According to Google’s search console, Butter, What?!’s traffic is only up 10% this week compared to last week. I’m still excited about that; compounding a 10% improvement each week will add up fast! Just not as fast as 2.5 times.

UPDATE: October’s numbers!

Butter, What?! saw 3,723 visits in October with 3,229 of those visits coming from Google. We didn’t quite double the numbers from September, but I’m definitely pleased with these numbers. Total visits are up more than 75%, and clicks from Google are up 90%.

If traffic levels stagnate, November will still see 17% more search traffic than we saw in October.

In October, Butter, What?!’s traffic account for more than 11% of the combined traffic of our three blogs. I’m impressed by this, because traffic is up 12.5% and traffic is up 25% over last month.

I don’t have any conclusions to draw. I just wanted to post an update with fresh numbers!


I have no idea who the target audience for this blog post might be, but I’m excited about how things are going, and I figured it might be interesting to someone! We started a new blog, and it is starting to accrue some content and gain some search traction.

How do you think we’ll be doing next month? Or by the end of the year? Do you want to get involved with what we’re doing? Let me know in the comments, or stop by the Butter, What?! Discord server to chat about it!

Designing My Carbon Fiber Prop Tool

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I’ve been looking for an idea for something I can send out as a perk to my patrons on I’ve also been on the lookout for a part that I can squeeze into the wasted areas of my carbon fiber sheets.

Carbon fiber sheets aren’t ridiculously expensive, but they also aren’t what you’d call cheap. Some of the parts for my Kestrel and Falcon frames have rather odd shapes, and they need to be oriented in such a way that the length of parts follow the strands of carbon. I wind up with a lot of 1” by 2” areas all over the place that are just too small to fit quadcopter parts.

I’ve already written at length about why I’m designing this prop tool over at Butter, What?! In this blog post, I’m going to tell you about what I learned while designing this prop tool. If you want to read about why I’m designing this prop tool, you can read about it at Butter, What?! I had to overcome some new problems related to CNC machining that don’t apply to my usual 3D-printing designs.

A CNC router can’t cut sharp interior corners

A CNC router, like my Shapeoko XXL, cuts material with a round bit. If I just subtract a 8mm hexagon from my carbon fiber, each of the six corners will have a radius that matches my endmill instead of a sharp corner. Without that sharp corner, my 8mm nut driver won’t fit over the 8mm prop nut!

In theory, this isn’t a big deal. You just have to tell the CNC machine to cut a little deeper into each of those corners. They call these cuts “dog bones.” What’s the best way to add dog bones with a parametric OpenSCAD design?

CAD and CAM have close ties in the CNC world

I toyed with two different ways of accomplishing the same goal. I’m disappointed because both options require my OpenSCAD model to be aware of the diameter of my endmill, or at least be set up to accommodate the largest endmill I might use for this operation.

I’m using a 2mm endmill, because that’s what I use to cut Falcon and Kestrel parts. I’d like to be able to cut prop tools as part of the frame cutting jobs.

On every CNC part I’ve designed so far, all the cutting operations for my perimeters involve an inside or outside contour tool path. That means that the 2D CAD file that I’m exporting matches the dimensions of the physical part. Instead, you can tell your CAM to follow your CAD file’s path with zero offset.

I toyed with the idea of experimenting with that third option. I could scale down my hexagon by the radius of my endmill. Then I could just add a perpendicular 1mm line at each of the six corners. Just the fact that I haven’t attempted this before seemed like a good enough reason to give it a shot, but I quickly realized that it was going to be a lot more work to plot out the shape I needed with OpenSCAD.

I abandoned this idea so quickly that I don’t even have a screenshot of what it looked like!

Prop Tool Dog Bones

I was also disappointed that this option would only work with a single endmill. I would have to export a new SVG file if I wanted to use my 1.6mm endmill, and that would be a bummer.

for (i=[0, 60, 120, 180, 240, 300]) {
  rotate([0, 0, i])
    translate([hex-c, 0, 0]) cylinder(d=2.1, h=t, $fn=12);

Instead, I placed a 2.1mm cylinder near the six corners of my 8mm hexagon, and I’m pleased with the result. It leaves room for the corners of the prop nut, it was easy to model with a simple for loop, and it will work with any endmill up to 2mm in diameter.

The scale of 3D printing makes this sort of thing simpler!

Working with a 0.4mm nozzle and relatively soft plastic is quite a bit different than working with a 2mm endmill and rigid carbon fiber, aluminum, or steel!

In either case, there needs to be a bit of clearance between the walls of my prop tool and the nut. With ABS plastic, it doesn’t matter that the 0.4mm extrusion of plastic doesn’t make perfect corners. That tolerance between the tool and the nut is probably already large enough to make up that tiny amount of extra material in the corners, and even if it isn’t, ABS would be soft enough to just get out of the way the first time you use the tool.

If we were cutting this tool out of steel, and we didn’t cut the dog bones into the six corners, we would have a real problem.

Engraving my website on the side

This was fun. It was my first attempt at a v-carve operation. When you engrave lettering to shiny, reflective aluminum, it shows up pretty well all by itself. When you engrave into carbon fiber, it still just has a matte black finish, and you can’t see it.

I borrowed some white nail polish from my wife. I slathered it generously over all the letters, then let it dry. I wasn’t sure how to remove the excess nail polish without ruining the finish of the carbon fiber sheet, so I just scraped it off with another flat piece of carbon fiber. It was strong enough to remove the excess nail polish, but not so hard that it would scratch up the smooth surface.

It worked better than I expected. There are a few problems with the first prototype. A few of the letters seem slightly misshapen. The details might just be a little too fine for the carbon fiber sheet’s epoxy to hold together well.

I’ve scaled the letters up from 4mm to 4.5mm tall, and I’m planning on cutting the next one at about half the speed. With any luck, that will clean up most of the problem areas!

I’m quite pleased with how my first attempt at both v-carving and nail polishing came out!


The prop tool is open-source, and it is licensed under the GNU GPL version 2. I added the OpenSCAD source code, dxf, and svg files to the falcon-frames repository on Gitlab. The OpenSCAD source is a little rough. I didn’t put much work into making sure it was cleanly parametric. It has quite a few magic numbers sprinkled about, because I was more concerned with getting the hex openings sized correctly.

What do you think? Would you use a carbon fiber prop tool like this? I know I prefer my $15 Speedix prop tool, but I’ll be adding a carbon fiber prop tool to all my bags. Are you as good at misplacing prop tools as I am? Let me know what you think in the comments, or stop by the Butter, What?! Discord server to chat with me about it!

Backing Up My Bitwarden Database

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I’ve been using Bitwarden for a little over a month so far. I’m enjoying the experience, and I haven’t had any problems, so I expect that I will continue to use Bitwarden as my password manager for the foreseeable future.

That means I need a way to back up my Bitwarden database. Keeping my passwords backed up happened for free when I was using Keepass. Your Keepass database is just a securely encrypted file, and my cloud storage solution kept a copy of that file on each of my computers, my phone, and my tablets. There was also 90-days’ worth of history stored on my Seafile server.

Bitwarden is different. There is no password database file. From my perspective, everything is magically stored on the server. How am I going to keep a backup? Can I automate it? Where should I store the backup?

While I’m at it, I figured this would be a good time to update the backup process for my ssh and GnuPG keys as well!

When will I need to use a Bitwarden backup?

I did some testing for my own peace of mind. I disconnected my laptop from the network, completely shut down my web browser, and fired it back up again. I wanted to make sure that I had access to all my passwords even when the Bitwarden servers aren’t available.

As you would expect, this worked just fine. I can access my passwords, and I was able to export a CSV dump of my database without access to the Internet. What does this mean?

My Bitwarden backup script in action

It means that I will still be able to dump my passwords even if the Bitwarden company disappears off the face of the Earth over-night.

I don’t need daily backups, but that would be nice. In practice, I probably only need a backup any time one of my core passwords changes. If I lose my Slashdot password, they’ll let me reset it via email. If I lose my Gmail password, it would be a huge pain in the butt!

The Bitwarden CLI

The Bitwarden command-line tool seems pretty good, but its export functionality falls short of what I was hoping for. The command-line tool, the native application, and the browser plugin all have similar limitations, but I was able to set up something that will get the job done.

Exporting requires that you decrypt your vault. It would be nice if you could just pull your vault out of the app in its existing, unreadable state, but I wasn’t really expecting to be able to do that.

The Bitwarden CLI can export a CSV or JSON file, but it has to write to a file. You cannot export to STDOUT. I was hoping to be able to do something like this:

bw export --output - | gpg --output myvault.csv.gpg -e -r

You can’t do this. Bitwarden’s CLI doesn’t respect the tradition of using - as the filename to designate STDOUT.

Ugh. I don’t want my plaintext passwords to touch the disk.

I finally found a use for my USB drive with Brian’s face on it!

If I can’t encrypt the exported data before it touches the disk, then I guess I’m going to have to store Bitwarden’s CSV file on an encrypted disk. The export is going to be a manual process anyway, since it will require me to enter my passphrase, so why not use an encrypted USB flash drive?

I encrypted the flash drive using LUKS. If you’re on Windows, you could probably use something like Veracrypt. You could most certainly use a GUI to configure your LUKS encrypted disk, but I have absolutely no idea how to do that. These are the commands that I used:

cryptsetup luksFormat /dev/sdb
cryptsetup open /dev/sdb TemporaryName
mkfs.ext4 /dev/mapper/TemporaryName
cryptsetup luksClose TemporaryName

I may as well back up my ssh and GnuPG keys

I don’t often make backups of my ssh or GnuPG keys. I could write 2,000 words about my key-management practices, but I will try to be brief.

My ssh keys allow me to log into machines that are extremely important to me: my blog’s web server, my virtual machine host, or my NAS. I have at least one unique ssh key on my laptop, desktop, and tablet. If any one of those three computers is lost or compromised, I can easily remove its corresponding public key from all my servers.

Since I have different keys on three different computers that can log in to all my servers, I don’t need backups of my ssh private keys. If my laptop dies, I can simply generate a new key and update all my servers using one of the other two good keys.

GnuPG is different. While my ssh keys identify who I am and which machine I’m using, my PGP key only identifies me. There is no replacing my root PGP key. If I lose that private key, I’m probably in trouble. All sorts of backups and important files would become completely lost.

My PGP key doesn’t change very often. In fact, I’m long overdue for a fresh key! I even have a hard copy of my PGP key printed out.

Even though my PGP and ssh keys are encrypted and have strong passphrases, I don’t feel comfortable storing them anywhere in the cloud. As long as I’m going to be backing up my Bitwarden passwords to a USB flash drive, I may as well include my desktop’s ssh and GnuPG keys, right? It only requires an extra tar command or two!

I’m not sure that was brief.

My backup script

You don’t need to script any of this, but I did. I’m lazy. I can’t automate the entire process, but at least I can automate some of it!

#! /bin/bash

dir=/root/usbbackup  # bw cli snap won't write to /tmp
datestamp=$(date +%F)


cryptsetup open /dev/disk/by-uuid/$uuid usbbackup || exit 1

mkdir $dir || exit 1

mount /dev/mapper/usbbackup $dir || exit 1

## backup ssh and GnuPG keys and configuration
tar cf $dir/ssh-$datestamp.tar /home/wonko/.ssh
tar cf $dir/gnupg-$datestamp.tar /home/wonko/.gnupg
tar cf $dir/ssh-$datestamp.tar /home/wonko/.ssh

/snap/bin/bw unlock  # I don't know why I need this, but I do?!
export BW_SESSION=$(/snap/bin/bw login --raw)

/snap/bin/bw export --output $dir/bw-$datestamp.csv

/snap/bin/bw logout

gpg --output $gpgdir/bw-$datestamp.csv.gpg -e -r $gpgrecipient $dir/bw-$datestamp.csv

echo New files on USB drive at $dir:
ls -l $dir/*$datestamp*

echo New Seafile GPG files:
ls -l $gpgdir/*$datestamp*

umount $dir || exit 1
rmdir $dir || exit 1
sync # for paranoia
cryptsetup luksClose usbbackup || exit 1
sync # for more paranoia!

echo Backup complete, USB drive synced and unmounted.

My backup script isn’t exciting or sexy, but I figured somebody might ask about it, so here it is!


I feel a little safer. My passwords can survive if my house burns down or Bitwarden’s hosting goes out of business. Even if both catastrophes occur on the same day, there will still be a GnuPG encrypted copy of my passwords stored on my Seafile server.

What do you think? Are you using Bitwarden? What are you doing to keep your passwords safe? Do you have a semi-automated backup process like mine, or do you manually export your database every once in a while? Let me know in the comments, or stop by the Butter, What?! Discord server to chat with me about it!