CF undercarriage

Aerospace Composites sells unidirectional carbon fiber which is .005" and 3.5 oz./sq.ft. This would probably be a good material to make a CF undercarriage for next year's plane. I'm aiming for 55 oz. Does anyone have an idea about how thick the CF has to be to handle the loads?

Jim,

I used the CF woven cloth rahter than the unidirectional. It allowed me to set up 45 degree grain. I made 3 gears (so far). The first had 4 layers of cloth and about 15 strips of CF tow. It is probably too springy. The last has 10 layers of cloth and about 15 strips of tow and is a bit too stiff. So, I suspect that about 8 layers of cloth would do it.

This is all, of course, contingent on the type of epoxy used, how much post cure time is used and the amount of compression applied to the mold.

It needs to be alot thicker than would be required for the load in order to be stiff enough. The flex is controlled by the panel thickness or cross section of the strut. It could be cored with a balsa strip or similar and be lighter--the middle layers are just acting as spacers for the outer. A good starting point is the same thickness as Dural--it'll be lighter and stiffer. Then work on it from there.

FWIW

I recently made a set of composite gear for a 32 ounce profile. They are straight-legged with a 10 inch spread and 3.75 rise, tapering from 1.00 wide at the fuselage to .50 at the wheels; all inside radii are .50. The lay-up is .070 thick; 14 plies- 11 longitudinal, 1 each at ±45° and one at 90°. I used the same unidirectional CF you propose, used Pro-Set epoxy vacuum bagged at 21 in Hg with porous bleeder; it was post-cured per the manufacturer's spec. The weight is 10 grams per leg.
This gear is amazingly stiff- far stiffer than necessary for my plane. In my judgement, .080 thick with similar geometry will be more than adequate for yours. They will probably prove to be too stiff, but you can mess around with different density tires to get the degree of shock absorption that works best.
Derek Moran

I recently purchased what seems like a fine carbon fibre gear set for the 'zoot suit' Nobler from RSM. I picked the .35/40 size, they offer another for larger ships.

http://www.rsmdistribution.com/building-03.htm#gear

Why make a custom one?

Larry (too zoot to snooze) Lowe

>>Why make a custom one?<<

Well, apart for custom applications (but I need one "this" wide), it's fun to make your own stuff.