terry.mortimore

My Feedback: (1)

Hi Gang:

I didn't get much action in the Composite forum so I thought I'd try here.

I have a Bud Nosen Cessna 310 kit which I have read requires the addition of Carbon fibre laminate spar caps.

The wing span is 120" and is 2 1/2" thick at the root and tapers to 1 3/4" thick at the tip. Ive been told that a realistic wieght would be in the 25-27 lbs range. The plans show 1/4" balsa spars with no shear webbing. I plan to add shear webbing when I build the wing.

The question I which I would appreciate some guidance on, is what thickness to use for the carbon spar caps. A search of RC Universe turned up a note stating .014 would do the trick, but I'd like to know how this thickness was reached.

Any thoughts or guidance out there?


thanks, terry

Walter D

My Feedback: (16)

Of more importance than carbon fiber lamination is using hardwood, such as spruce for wing spars and then using balsa webbing (3/32) for the entire length of the wing, I believe the wing on this bird is fully sheeted, that should be more than enough strength.
The addition of carbon fiber will of course add to the rigidity of those wings, you can use the thinnest one available, as long as you glue the strips on both the upper and lower spars, it should be more than enough, hell, you don't even have to use carbon fiber, find wrapping tape, the one that comes with filament and stick that on the spars and it will work just as well as carbon fiber and a whole lot cheaper too, don't forget that if you are going to cover the wings with something like monokote or polyester fabric, the wings will be very, very strong, no way they will brake in flight.
I know that your question was "what thickness...", and the reason you haven't had any answers is that,... it doesn't really matter in this case, because the strength of the wing derives from many things, when this airplane was designed I don't believe carbon fiber was used in model airplanes just yet, and I have never heard of any one of them braking up a wing in mid air, on the ground, that's a different story.

Giant Scale

Probably the easiest and cheapest method is to replace the balsa spars with spruce stock. You can then add a 1/16" thick shear web and cap the spars with .007" unidirectional CF. This should be plenty strong and save you some weight.

Eaglewatch

I have an older 310 kit framed up, and I used shear webbing all the way out in the wing with spruce spars. I did not add any CF to the wing, as I saw no need to do so. The wing is fully sheeted, and (in my case) will be glassed and painted. I really doubt the wing needs any CF reinforcement, but if I was going to add it, I would use small diameter fibers, as I really don't think the wing will fail without extrordinary flight loads. The plane was designed as a sport scale flier, and does not lend itself to violent aerobatics. Therefore, if flying it as it were "designed" to fly, the wing should be plenty strong.

Regards,

Al Parry
[email protected]