Newflee

Does anyone have experience with this hybrid cloth in making landing gears.
I have to make one for a 33% decathlon that weighs 35 lbs. The original gear was 1/4" 6061-T6. My question is if I should lay it up entirely of CF/Kevlar cloth or alternate layers of glass and the hybrid? I don't want to make it entirely from the hybrid if I don't have to for cost and waste reasons. I want to retain the 1/4" thickness but wonder if a solid 1/4" of the good stuff will be required.

Any experience will be great.

BTW I have made one from carbon and it is very strong but I think maybe too brittle, thus the carbon/ Kevlar hybrid.

Thanks
Lee

davidfee

Rather than alternating glass and cf/kevlar, use a few layers of the hybrid on the outsides and make a glass "core." This way the stiff fibers are on the outside where they will do the most good. As for the brittleness, remember that the carbon will most likely snap before the kevlar "sees" any real load. So this hybrid looks really cool... but engineering it's use is rather challenging.

-David

rsieminski

On a 35# plane, I don't think I'd use glass at all. I made some out of glass that were way too flexable. All the other sets I've made were carbon/kevlar cloth, carbon tow, carbon/kevlar cloth. I used the kevlar going in the same direction as the gear long ways.
Here's the details:
http://mywebpages.comcast.net/webmas...e/cf-gear.html
and a picture of the finished product:

and another:


I mostly go with the arch shape, because of strength. That top corner, like on conventional gear, takes a lot of stress. They could be done that way, but you'd ned to add extra layers on the corner radius. Take your time, and they'll come out nice!

Ghostrider FIN

Looks great! Do you use one direction carbon inside the landing gear to fibers set same direction as the gear long ways? Do you have picture about that carbon used in side of a gear? I think i make this kind a landing gear to my CG Sukhoi Su-26 because it original aluminum gear weights way too much.

rsieminski

Yes, it's uni-directional fiber called Tow. All the fibers inside run the long direction. It's cool looking stuff. It's flat, with a thread every 2 inches or so to keep all the fibers in line. The completed gear, suitable for a .90 sized plane, weighs around 2 oz. The carbon/Kevlar is really just for the outside layer, for looks, in this case.

mogles

My Feedback: (7)

I am hoping to do the same as your gear looks really cool. However, I am confused. Plastic mold baked at 150 degress? wouldn't it melt?

Can you post some pics? I would love to see the mold.

Thanks much.

scole

My Feedback: (5)

What i use is particle board cut up and glued together about 1/2" wider than the gear itself. You then cut the shape of the landing gear from the block, and sand it smooth. The buy a formica sheet about 2'x4' and cut 2 strips the width of the mold and use contact cement to glue them on the face of the mold. Put a layer of PVA mold release on the formica and your set. I like this alot better than the foam mold because you can really crank down the vacuum in the bag to get lighter landing gear.

scole

My Feedback: (5)

Here is the mold

rsieminski

I broke the 1/2 the mold for the gear pictured, but have since been working on a mold exactly like scole has described. I used MDF in place of the particle board. It's a little harder, more like compacted dust, but really anything will work. Get gloss Formica, and get some nice uniform coats of PVA on the mating surfaces. I have switched my process a little. I now put a thin layer of epoxy on the surface, and wait for it to gel up, then make my layup on a piece of glass. Epoxy, CF, squeegee, epoxy, CF, squeegee, epoxy, CF, squeegee, ..... Let it sit for a bit, until it's almost at the tack stage, then put it in the mold, compress and bake. If you can catch it in time, it gets to an almost hard phase, that allows for easy trimming. It's really got to be an experience 1st hand kinda thing. You can practice on cheap glass a couple of times, to get a feel for it.
Try it, it's fun to do. I've been making CF props lately. I'm working on a big one right now, 22x8. CF parts look so cool when they're done.
--Rick

scole

My Feedback: (5)

Hey Rick, how do you make your props?

rsieminski

I make a temp 1/2 mold out of clay 1st then pour epoxy over it, peel out the clay, pva, and more epoxy. I'll try to post a pic when I get home tonight.

scole

My Feedback: (5)

Thats cool, i'd like to see a pic also when you get home. I want to try this!

davidfee

Here are some pics/instructions on making small carbon props.
http://members.cox.net/davidfee/PROPS.html

Making large ones would require slightly different techniques.

-David

rsieminski

That's exactly how I do it!

scole

My Feedback: (5)

I got a Q. with that. Do you put clay on the left side of the prop before you put the epoxy in? And how do you make the other half of the mold? I'm exited! I want one!

Newflee

I guess it is a little off topic now but since I started the thread I should mention that my gears (main and tail) turned out great. The main is made from three layers carbon cloth each side of about 10 layers hybrid and the tail is 90 % carbon with hybrid in the middle. It was layed up on a form much as has been described in this thread except it was not vacbagged. I think it will work out fine, and I may have struck a perfect ballance between the carbon and the hybrid. I have sat on the center section of this Decathlon with my full weight and the gear flexes but does not fault. The tail gear deosn't even move. Perhaps it is too stiff.

These pics show the look. My main objective was to put a slight bow in the gear as scale and at the same time achieve a little more strength....gear weighs 8 oz. (approx.) whereas the 1/4" 6061-T6 weiged 18 0z.

Newflee

and the TG

scole

My Feedback: (5)

Dude, it that your first time? It looks Awesome!

Newflee

First time with what?.... Just kidding.
Actually I have made lots of composite parts but never before with high tech materials.
I'm certainly pleased with what turned out.
Thanks for the compliment!


Lee

davidfee

Yes, exactly. The clay supports the entire prop... not just a single blade. I'm very sorry that my pictures don't show *exactly* what the clay should look like. I was in a bit of a hurry when I took those pictures, as I was just doing a mock-up. I'd already made the molds and figured some pictures would have been helpful.

You make the other mold half by popping off the outside "dams" and scouping out the clay. You want to get as much of the clay out as possible, without scrapingor removing the prop. Then use a bunch of wax and PVA over the whole thing. Clamp the dams back on and pour the other side.

Hope this helps,
David

scole

My Feedback: (5)

Ok, i got it now thanks.

Jim J

Lee, what wt and whose CF/Kev cloth are you using. ALways wanted to try that but I was afraid it wouldn't hole. I have the
glass/ some cf. vaccum equip....I was thinking of doing the wing tips cf ....I know you said you were doing it on the SD>
Later. Jim

scole

My Feedback: (5)

I mainly use the 5.8oz plain weave carbon fiber and the 5.9oz hybrid cloths in 2x2 twill. My favorite is the red and black hybrid, it looks very cool! One main thing that you will you a lot is a vacuum bagger. Make sure you get a good one or make one like i did.

Newflee

Jim, to be honest I don't have a number to give you on the weight but most of the hybrid stuff I've seen is pretty similar.
The SD wingtips that I"m going to make will just be glass. I don't see any reason to use expensive materials there.


Lee

Jim J

I have thebagger already. It is great for doing foam core wings. I have the glass and some CF for wing reinf but hadn't started doing any layups and forming. I will look for the red and black...sounds like it would be pretty impressive.
I'll get back here later. Thanks for the input and the info on the wings Lee. '
Later. Jim