Streamlined tubing curvature

[Jackal]

The first time I ordered streamlined tubing I thought it was damaged because it had a slight curve detectable when placing on a flat surface. The vendor (Wicks) told me for the last 20 years or so the quality has been such that it exhibits a slight curvature. So I built cabanes and landing gear with such. I just received the material for the N-Struts. These are longer, so the curvature looks worse. You don't need to place it on a flat surface, due to the length the slight curvature can be seen simply sighting/viewing down the tube. The fact that these "long skinny" pieces will be in Compression as N-Struts has me uncomfortable.

What do we do? Build airplane with them??

Has anyone found streamlined tubing that is "perfectly straight"? Has anyone attempted/succeeded in straightening this material, and if so how?
Has anyone increased the dimension of the tubing (over the last 20 years) due to the loss of integrity in compression due to the curvature? Has anyone any other ideas?

Thanks for any input!

[alvinsager]

Hi,
When I built my last plane either the plans or Tony Bingelis' books suggested torch heating one side of the lower longerons to bow them out to counter the fabric tension. I can't remember which side to heat, so I wouldn't try it until I found out which.
Good luck,
Al

[mmcgrew]

FWI : It is a common practice to straighten metal tubing before it can be used. We do it all the time with SS, brass and aluminum. For SS we have a truing table that we clamp the metal too while we apply heat. Leave clamped until cool. Does not take much heat.

Michael
N9648B