Carbon fiber tubes and rods

[woundedbear]

Hi everybody, Has anyone on the forum ever used small diameter carbon fiber tubing or carbon fiber rods in building a Guillow's model kit? I have seen carbon fiber veil material and was wondering if anybody has ever make thin walled tubes with this stuff? Looks like you could make thin walled tubes to reniforce wing leading edges,or maybe even build scale oleo struts with this stuff Anybody have any thoughts on this?

[Chris A.]

I have an He 219A-6 plan from Tom Arnold of FAC fame who used carbon fiber thread to strengthen the main wing spars. This technique was necessary as the large engine nacelles had to be integrated into and hung from the spars yet still leave clearnace for the rubber motors. If I was making a rubber model of the Martin B-26, carbon fiber thread reinforced wing spars would give me both motor clearance and wing strength.

[akjgardner]

I scrach built a Carl Goldberg Jr Satan with a carbon fiber arrow shat for the leafing edge and main spar. I have not flown it yet

[David Lewis]

I don't think anyone makes thin wall carbon tubes any more. I used to get them from Dr. Eder in Germany years ago. They were used for fuselage on indoor hand launch gliders, for example.

[RocketRobin]

I don't go to Germany for thin walled CF tube.
I go to my LHS.
I fly RC, so I use CF very sparingly. CF is conductive/reflective and can do nasty things to radio transmissions.

Cheers!
Rocket

[Bill Gaylord]

I use less and less myself, as efficient design shouldn't call for much of it, and it weighs, along with the glue used. The stuff is not cheap either. At one time I was on a major CF spar/tube kick.
I noticed the initial comment about LE reinforcement, where I would see that as a case in point, where for all the added effort of CF laminating, you can use an amply strong grade of hard balsa and end up at the same point. The last place I used any was for point reinforcement on the 24" Cub landing gear struts. The alternative to equal strength would have been to use 1/32" light ply, which would have been a bit heavier. The balsa strut legs were notched for the CF spar laminate, which reinforced the struts as well as the axle attachment point. Even in that case however, for all the added effort, 1/32" light ply would have been fine, and not much heavier. Since I covered the parts, the ply could have had lightening holes further lightening it, making the point that it really wasn't much benefit for the effort.

Another LE alternative is using wood dowel rod. 1/8" rod isn't terribly heavy, and is strong. There are cases where you want the thicker/deeper LE for a specific shape on the LE. In those cases however, a reasonable grade of balsa should be amply strong.

[woundedbear]

Bill Gaylord thanks for your input, your advice is always right on target. The weight of enoxy type glueing cancles out any weight savings that carbon fiber would yield. I do however have one question, where do you get 1/32-inch light plywood? I buy my wood from SIG manufacturing, and they only sell 1/8 and 1/4-inch light plywood. If you know of an internet seller who sells light plywood in the thinner 1/32 through 3/32-inch sizes please post the source for me, in fact if you know of any other source of balsa wood post that too. I have though maybe I could make 1/8-inch balsa plywood by using one sheet of 1/16-inch balsa with two 1/32-inch sheets, by using homemade sand bags to weigh it down. Ya' know sandblasting sand and heavy duty zip-lock bags reinforced with duct tape Back when I could still do heavy work I helped out a guy who restored cars and did a lot of sandblasting for him. Sandblasting sand is pre dried and I think it would work better than trying to use something like builder's sand. Back when I could still do the organic gardening thing, I once tried to sterilize some top soil to start my own tomato and sweet pepper plants Took a week to get the odor out of my house

[Bill Gaylord]

I'm fortunate to have an LHS that has 1/32" ply. I haven't used much of it lately, other than for motor mounts. I had seen people using it for control horns, but I always had to glue laminate the ends with thin CA, to keep it from delaminating around the holes. Once I got onto using sheet plastic for control horns, I haven't used it since for control horns. It is useful for apps such as cabin window framings, where you need something strong but don't want a massive, non-scale looking structure.

[davidchoate]

Not hollow carbon fiber, but I have seen on foam wings spars made of carbon fiber rods. I used then for the cabane struts inside windshield.

[Bill Gaylord]

I used them on the Cub, for the struts running from the instrument panel to the upper cabin.

[David Lewis]

There are two types of thinwall carbon tubes: Pulltruded (0.5 mm to 1.5 mm dia. with wall thickness 0.10 mm) and hand laid woven cloth (1.6 mm to 3.8 mm dia.).