DIY Carbon fiber hoops


#1

I’ve been exploring the possibility of making carbon fiber hoop sections. I’m not a PPG-er (yet) so I’m putting my tests here in the hopes of feedback from the community about whether this is a good idea. I’m also open to suggestions for changes.

Here is a picture of the finished test piece:

Here is a movie explaining the results:

In a separate post I’ll list the steps. Here are pictures of the connecting pieces, which I’ll print on a Form2. The red sections are screw pins from here:


#2

Here are the pictures explaining the process:


Carbon fiber sleeves (we will use two layers)


1/2" insulation foam from hardware store. Look for sections that don’t have dents.



Slide the sleeve over the foam, pull tight, and secure with zipties. This is still dry. The fibers should be at 90° angle when expanded over the foam.


I use MGS epoxy because I have some left over from my airplanes, but West systems would work fine as well.


Wet out the sections with epoxy resin. Try to get rid of as much extra as possible. Just use enough to give rigidity to the first layer.




Let the epoxy cure just so that it is fairly stiff and will withstand the heatshrink compression. Cut off zipties. Trim off the extra fibers and protect with tape.


Note the flat section. I used too much resin on this sample and it pooled on the waxed paper. Use less, and flip over a few times during curing.


Slide the second layer of sleeving over the first.


Secure second layer with zipties.


We will use special heatshrink from sollercomposites:
https://www.solarcomposites.com/composites/carbon%20fiber%20sleeves.html#Shrink


Wet out the second layer. You can have as much resin as you like, and you should saturate the fibers.


Slide the heatshrink over the set of sleeves, and start at one end with your heatgun. Use just enough heat to shrink the heatshrink and force the extra resin out the cool end. Go slow and let the resin soak in as you go.


Let cure for 36 hours.


When cured, run a boxcutter or xacto knife along the heatshrink to cut it.


Peel off the heatshrink.

I finished these by using 1500 grit wetsand, and then 3 coats of UV-resistant clear coat.


#3

Super dope, I like it. Ya CF tube for the outside ring would save some weight. I’m really interested to see where you take this.


#4

Here is a better movie explaining the finish coat and my plans for the connectors:


#5

Here are some updates in pictures and a video.


#6

That’s Interesting.
I was thinking of making carbon fiber hoop section on my future eppg project. my design is a bit different than a tube. its more like the tubing for the open EPPG but tapered at the back end.
i just designed a form for it in Fusion 360 today. I’ll be printing it with PLA. im thinking of using my mg mold release spray to remove the PLA core so im left with just the hollow Carbon fiber part.
I’ve made molds using PLA for epoxy casting before, it works great for a cheap form.

any progress with your hoop since posting?


#7

Yes very interesting
But why does the hoop have to be a tube?
The majority of the design is flat pieces of CF. Simple and attractive.
Why cant the hoop also be the same. 2 flat pieces with supports between that somehow lock into the arms the same way into/onto a 3D printed thingy doohickey.
Can CF not flex enough in the “hooping” circular form we need ?
I am sure the netting could be attached the same way with rivets?


According to this vid flex - 1 to 1.3 would be good – closer to 1.3 looks better to me.
Cheers


#8

Seems reasonable. Questions I would have:

  1. the edges of CF are super sharp. Would we need some kind of heatshrink wrap over the entire piece to protect the lines?
  2. How well would the spacers work to maintain the curve? Would they tear out rather than hold the appropriate bend?

#9

I did a test with aluminium. It takes the shape just placing the holes in the right place.

Here i tested it until it broke


#10

I never thought of the lines - I am wondering if in the cutting process a rounded edge could be put on them and then maybe some type of coating added afterward, maybe some more epoxy so the lines will slide.

As for spacers and the bend – got no clue!


#11

Very interesting !
I am guessing that CF will splinter when taken to failure.


#12

that’s a nice test but it needs a center support or it could buckle. I Sketched one up real quick.
My model is 10mm thick and would use M4 bolts. you would need 48 pieces to make a 5’ ring 40mm tall (not including aluminum thickness)
This is just to demonstrate currently no way to attach it to PPG arms.might be a bit crazy lol
I can make the sections longer so less parts to make.
but essentially you could have modular sections. I’ll make the model available if anyone is interested.




#13

Very nice - but I think cent needs to be more aerodynamic


#14

The hoop doesn’t need to be too strong IMHO. It’s main function is to support the netting to prevent lines, clothes, fingers etc from hitting the props. (Especially lines, you wouldn’t want say an A-line spooling up onto a prop spindle!). So these blocks home printed in cheap and lightweight plastic should be enough even with only equally cheap plastic strips. Who needs CF? Maybe if the blocks were deeper they would suffice on their own?

Regards

Paul


#15

“needs to be more aerodynamic” Valid point. that’s why i chose to model it with holes it would add so much drag just being a round I or H beam. I could round the edges too. I been working on another design for a few weeks that’s basically an airfoil ring.

it doesn’t need to be CF i used the material in F360 for contrast / reference the first two pictures are what F360 thinks aluminum looks like…
Getting a CF strip long enough may be very difficult. aluminum would be easier and much cheaper. I dont have any aluminum on hand to test it.
It could be printed at a low infill setting and make it light weight. I cant print in ABS yet so i cant make anything fly-able. without risking it warping in summer.

Anyone know the weight of the EPPG tubing? making something heavier isn’t ideal.


#16

The current 30mmx15mm hoop tubing on the openppg weighs 0.168 ounce per inch.
Your linked pieces are interesting but one potential hazard is hinging. Were you bolt each piece together if the edges round out at all and enough lateral force is applied they could hinge which would cause the hoop to fold.


#17

Thanks for the tubing information. so far my pla parts are 16.15g per piece. which is 0.57oz or 0.132Oz / inch. that’s without bolts or outer/inner strips.

I’m currently printing 3 pieces to test the flex in that direction without aluminum or CF strips. With the strips it should be much more rigid and less likely to hinge.
For example you can snap a Popsicle stick in half pretty easy but if you build an I or H beam from it its a lot more rigid. That’s the general idea with this one.


#18

Found this from the unit Phil got ride of – may use it to cover edge
image

Also – does the hoop need 2 rings of CF. If the have just he outer with the center support, or a reduced more aero dynamic version to give some extra rigidity to the CF ring that would be better. As Pauloz stated it does not need to be too strong. Just enough to keep lines out during luanch and landings - if you wipe out we have seen the strongest hoops out there still give and props break. In our case props are really cheap

Cheers