Fueslage Longeron Scalloping

[FredHoffman]

Hi,
I wanted to know how others handled the shrinking of the fuselage fabric. There seems to be a balance between getting it tight enough and not so tight as to create excessive scalloping of the thinner rear longerons. I shrank to only 275 degrees and called it quits due to the scalloping. Even the initial shrink at 250 there was a bit of scalloping. What I ended up with is an average of 1/16" bow to a max of 3/32" bow between weld clusters. It is only noticeable sighting down the fuselage. Is this in the range of what other others are seeing?

I talked to a guy who restored cubs and he said to hammer the tubes with a rubber mallet to bow all the longerons out before covering. I didn't have the guts to try this. I also read about those that used a 2x4 and rubber mallet to straiten them out after covering. Another cub builder talks about a reversed clamp bending them back strait. Just wondering if I should try this or just accept what I have got and move on.

Just attempting to get it perfect....

Thanks,

Fred

[stede52]

Fred,
You stopped shrinking at the right time, very nice job . Its not important to shrink everything to 350 degrees, however it is is important to make sure every inch of the fabric has been heated/shrunk evenly without causing excessive scalloping, 1/16" - 3/32" of scallop is very good.

[FredHoffman]

Thanks Steve,

I'll leave it alone and move on.

Fred

[gkremers]

Fred,
I spoke to Jak about this when I was doing the fabric work. He said the factory shrinks just about everything to 300, the only place they go higher is areas within the prop blast. At 300 I have a more scalloping than you, mine averages 1/8" in those areas with max of around 5/32". If I were to do it again I'd only shrink to 275. No wonder why some of you guys build 2, you actually know what NOT to do on the second one.

Oh well, moving on to the painting stage.

Gary