Acro Quad Build Log

[trigger]

A few weeks ago, I decided to build an acrobatic quad.
Helped by the wisdom and guidance of both Cyberdactyl and FGA, I settled on a design largely inspired by Warthox's Mini CP.

As it is my first scratch build, I feel like keeping a log along the way

The specs will be as follow :
- Carbon fiber center plates with carbon hybrid arms (around 300mm motor to motor)
- Sunnysky X2208 1500kv outrunners
- HQ 8x5 CF-reinforced props
- KISS 18A ESCs
- Naze32 Acro

Here's a preview of the design, made with FreeCAD :




Part I - Cutting the center plates

The first thing I did was cutting the center plates, from a 2mm thick carbon fiber sheet.
I printed a few 1:1 patterns, cut them out with a hobby knife, and taped them onto the CF sheet.

Using a dremel tool on a vertical stand, I first tried some #113 bits. They're cheap, and said to be able to cut through light metal.
Unfortunately, the first one I tried became dull after just a few centimeters.

So, I switched to the much more expensive #569 grouting bit... which cut through CF like a hot knife through butter.
In fact, it cuts so well that during my first attempt, I let the plate slip and it made a deep dent :


Thankfully, I had a big enough CF sheet, and could cut another two :


Next, I tried to file them down to shape... Easier said than done.
While the bowed-in square design looks great, it proved very difficult to get symmetrical circular edges.
As my inability to do so became more and more apparent, I decided to move on, and drill the holes for the arms. The idea being that they may serve as reference points to make the filing easier.

To get perfectly aligned holes, I used double-sided tape to hold the plates together, and taped a 1:1 printed pattern on top.


Worked like a charm

After that, I resume filing the center plates. Here's the result so far :


I'm still not 100% happy. They look quite uneven, so I'll spend more time trying to perfect their shape.

That's all I could do this week-end unfortunately. I hope I'll be able to work on it again this week. I'll update this thread at that time

 

[cranialrectosis]

Looks good, Trigger.

When my WarpQuad arrived, I had to finish the CF with sandpaper and files. The finishing took longer than most of the rest of the build but CF is worth it.

Have you considered 4mm thick plate for booms or are you sold on the square tubing?

 

[FinalGlideAus]

 

[trigger]

Looks good, Trigger.

When my WarpQuad arrived, I had to finish the CF with sandpaper and files. The finishing took longer than most of the rest of the build but CF is worth it.

Have you considered 4mm thick plate for booms or are you sold on the square tubing?

Thanks

I'll make another sanding pass tonight, hopefully fixing the odd shape issues, and get the finishing right.

For the arms, for now I'll try the square tubing : 10x10mm pultruded CF tubes with wood dowel reinforcements.
I also have some .5x.5" aluminum square tubes.
I should be able to get them done today, I'll update the post with a weight comparison.

As for your idea, I don't feel confident I can cut 4mm thick plates by hand at home. At least not reliably and not precisely enough to get 4 identical arms... The 2mm CF plate was already pushing my dremel tool quite a bit, 4mm may be too much of a struggle for that kind of equipment.
If I had a CNC router, that'd definitely be an option though

 

[trigger]

Just a quick non-update to say that I didn't gave up, but didn't have a lot time to devote to finishing the build lately.
The frame is 95% done, I started soldering the electronics (all 4 motors and ESCs), but now I'm on vacations away from home, and won't be able to work on the quad until the end of august.

In the meantime, I planned to fly my Mini-H, as well as some FT planes while on holidays... except I forgot all my batteries at home...
Oh, well...