Intercostals question

[t j]

Tjay, I attended a Polyfibre seminar about 20 years ago right after I bought my kitfox kit. He was from the polyfibre factory. The first thing he said when he began was, You Kitfox guys. You can bend your airframe if you shrink to 300...maybe it was 350 degrees, whatever the maximum is.

His instructions were to start low 200 or 250 and shrink the whole thing. Then increase by about 25 degree increments with a helper holding a straight edge on the tubing and shrink it all again. If you see a tube start to pull away from the straight edge, stop right there.


Mine is a Classic 4. My kit included intercostals for the horizontal stab only. I saw all these fancy Kitfox tails on the internet so called the factory and asked why my kit didn't have intercostals for the rest of the tail. He said it's just for looks, Your plane will fly just fine without them.

[jiott]

On my SS7 I shrunk to 350 on everything and had no structural deformation. In some areas where I was concerned I used the straight edge method to check and make sure.
The earlier models may be an entirely different story.

[TJay]

I decided to spend my Saturday building them. I wasn't going to install any but I really wanted the look of the newer planes. I think it should look nice,I still have to do the elevator but that's for a different day. Im not to worried about the weight since I have a heavy E gearbox way up front. Thanks for the input guys.

[jiott]

Make sure you stiffen any of those ribs that are not glued directly to a steel member, especially on the elevator. Otherwise they will deform into an "S" shape when you shrink. A 1/2" wide piece of ply glued perpendicular to the rib (as the build manual says) is required.

[TJay]

Thanks for the tip I will do that.