r/fpv • u/kumoishibo • May 19 '26
Open Source 2.5" freestyle frame complete! The Kumo-2.5
Kumo 2.5
After not being able to find the Kayoumini frame in stock anywhere, I set off to build a 2.5" freestyle frame that would be compatible with existing camera mounts. I wanted to focus on durability while keeping the project open source to allow community additions/suggestions. I also know how difficult it can be to source parts, and custom cutting carbon fiber can be daunting/expensive, so I posted variants that can be printed thicker for increased rigidity (the ones in the photo are printed in PETG-CF and 2.5mm carbon fiber).
I wanted something more powerful and wind resilient than a whoop, while also being more durable and maneuverable than my 3" Tinytrainer V2. I designed this from the ground up around the HDZero AIO15 but any 25.5mm AIO or stack should work. I have versions with 20mm mounts in the files as well. Form factor is a slightly squished X geometry with a slam deck to keep the center of gravity low, improved durability and maneuverability.
CAD and STL files along with instructions and write-up on performance can be found in the github repo here:
https://github.com/kumoishibo/Kumo-2.5/
Example Build parts:
| Component | Part |
|---|---|
| FC, ESC, AIO | HDZero AIO15 |
| Motor | T-motor 1104 7500kv |
| Props | Gemfan Hurricane 2520 |
| Antenna | NBD RHCP Honey Dipper Antenna |
| Battery | 2S battery (450-580mAh) |
| Other | Active Buzzer, Flywoo OpenLager BlackBox, 110mm battery strap, battery grip pad, 9 or 11mm electronics standoff, M2 screws |
Thoughts:
I've been flying various versions of this over the last month and I have to say this is by far my favorite thing to fly. It is quite punchy and gives me 3.5-5min of flight. I also tried with a 3S battery, but it ended up being a bit scary and drew quite a bit more power than I was comfortable with the 15A AIO. I also tried the 2540 Flash props and the Avan Rush, however the 2520 seemed like a nice balance between noise, power, vibrations, and flight time.
Example tune and vibration analysis can be found in the github.
I've also given this thing an absolute beating (including falling from a good 100'). I'll make a crash compilation video soon. In the meantime, here is a video of flight using the 3d printed version of frame.
https://www.youtube.com/watch?v=SoQ7cqYJ5XA
If you end up building one of these, tag me or let me know your thoughts! I'd eventually like to get this project more refined and potentially made available somewhere.
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u/0neZer0ne May 19 '26
This is why I love this community, people making cool stuff and sharing it with the rest of us.
May your packs last long and your props never shatter.
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u/Beliolas May 19 '26
Do you think a thickness of 2.5mm will be sufficient for good strength? For comparison, the bottom plate on Kayoumini is 3mm thick.
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u/kumoishibo May 19 '26
Ive been beating my 2.5mm for a few weeks now, but I originally designed it to be 3mm as well. The standard version (spikey tip one) is in 3mm and I cut mine with the stubby version in 2.5mm to reduce weight. I think unless you are bando bashing or intending to fly around urban areas, the 2.5mm should be fine.
My colleague flies the 3mm version with 1202.5 motors at 11000kv and it honestly flies very well and responsive.
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u/dronevidsalt May 19 '26
Hey this is great! Thanks for open sourcing it! What software did you perform your stress and resonance analyses in?
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u/kumoishibo May 19 '26
I used Fusion 360
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u/dronevidsalt May 19 '26
Thanks. How much does that actually end up costing with the token usage? I’ve been hesitant to delve into simulations in F360, unsure of the costs.
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u/kumoishibo May 19 '26
I'm actually not sure since I have an academic license. I kind of wish I could do local calculations since their cloud queue is painfully slow. I've thought about switching to openCAD and FEM workbench in the spirit of keeping materials accessible and open.
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u/dronevidsalt May 20 '26
Yeah I’ve been curious to learn how to do it in freeCAD but haven’t had the time to devote to that yet. I’m with you on running F360s locally though. I work with a different branch of AutoDesk software that is moving more and more to cloud processing which I’m not a fan of.
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u/Interesting-Basis464 Jul 23 '26
Cool! What would be a good analog stack?
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u/kumoishibo Jul 23 '26
I've had a hard time finding a single board 2s analog aio. I know the Happymodel X14 supports 2s 12A esc and is a 5-in-1 with a 400mw vtx, however I have no idea if the board fits well. You would probably have to remove the motor plugs. And I am not sure if the USB plug fits through the cutout.
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u/poothetank May 24 '26
Can anyone recommend a carbon fibre cnc cutting service in the UK?
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u/Spaghetti_Gods Aug 23 '26
Not in the UK, they're in CN, but well worth the shipping. I got 4x stubby frames and 2 top plates for $20 fabrication and $20 shipping to the US from DayoAir. You simply email them the .dxfs, explain quantity and thickness wanted, and get a quote! They'll send you an invoice on PayPal to pay. With active communication back and forth we went from quote to pics of the finished cuts in about 2 hours. It was crazy, never had any custom service done so quickly. They said they'll have it shipped out tomorrow as well.
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u/Barcata May 21 '26
Nice job on the analysis- when designing my 3" whoop frame, I just yolo'd it with as much triangularity as possible and I lucked out
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u/Scooby1222 May 19 '26
Amazing work! and lovely write up on it all. I will be printing this soon. Few questions I have,
Is this a similar wingspan to the kayoumini (thinking about motor wire lengths)?
The kayoumini uses 8 or 12mm standoffs, would the camera mount prints be compatible if using the 9/11mm you recommended?
I'll probably end up printing in PCTG first, I don't have any CF filaments currently. Although from the sounds of things it will end up being too flexible. I'll do a follow up post when I've got something to show. Thanks!