Question on bending....or re-bending

In working on the vertical stabilizer, I have found that the rear spar doubler (VS-808PP) has come out of the crate with a significant bend in it. Since this piece is 1/8" thick, I'm guessing that the aluminum comes to Vans in a large roll rather than a sheet and the bend is left over from the aluminum supplyer''s manufacturing process.

When this piece is cleco'd to the actual rear spar, the assembly ends up with roughly a 1/4" bend in it, which is unacceptable.

My thought is that this is probably so common that I haven't been able to find anything about it on the forum. I'm of the opinion that some of the stress needs to be relieved to allow the actual spar to keep the assembly straight.

My questions are:

1) Is this as common as I think it is?
2) If so, what method did you use to take out the stress/bend?
3) I'm of the opinion that the doubler doesn't need to be perfectly straight, it just needs to have enough of the stress removed to allow the actual spar (VS-803PP) to keep the assembly perfectly straight, is this correct?

Pictures are below.





Thanks,

Fred

Mine was exactly the same, I just applied some pressure and bent it back and attached it to the rear spar. When it all goes together, it will come out nice and straight. When you get to parts like the flaps, the spars end up with a slight bow after you dimple the flanges. The plans even mention this will happen and that it's ok and the finished part will be straight - and it is

mine was similar. I don't recall intentionally bending it straight.

when I cleco'ed the skin on, holes lined up perfectly. If spar was bent due to the doubler curve, skin holes would not have lined up.

Back when I got my empennage kit I had the same question. Vans told me to put the doubler over my knee and straightening it. Since then chapter 5. General Information is covering this, see 5.13.1.

I think this is from the hole punch process, mine was the same, I think the early kits had no lightning holes.

Gentlemen,

Many thanks for the help.

ScaniaRV Back when I got my empennage kit I had the same question. Vans told me to put the doubler over my knee and straightening it.

Click to expand...

Problem solved.





Thanks again for all the replies!

Fred

ScaniaRV said:

Back when I got my empennage kit I had the same question. Vans told me to put the doubler over my knee and straightening it. Since then chapter 5. General Information is covering this, see 5.13.1.

Click to expand...

This is very interesting. When I got my kit last week and unpacked and inventoried everything, VS-808PP was not only bent, but had these stamp marks in it (circles and semi-circles) all across the face. What's worse, Vans wrapped it tightly on top of the HS spars during shipment, which resulted in the spars getting a slight bow on the end where VS-808PP was strapped to them. I thought it was a defect and contacted Vans expecting them to replace it, but they said that it was perfectly normal and that's how the part comes from the manufacturer. They said it will straighten itself out during the riveting process but I'm scratching my head wondering how this thick piece will bend back straight. Will use the techniques advised in 5.13.1. Thanks.

PHXflyer said:

This is very interesting. When I got my kit last week and unpacked and inventoried everything, VS-808PP was not only bent, but had these stamp marks in it (circles and semi-circles) all across the face. What's worse, Vans wrapped it tightly on top of the HS spars during shipment, which resulted in the spars getting a slight bow on the end where VS-808PP was strapped to them. I thought it was a defect and contacted Vans expecting them to replace it, but they said that it was perfectly normal and that's how the part comes from the manufacturer. They said it will straighten itself out during the riveting process but I'm scratching my head wondering how this thick piece will bend back straight. Will use the techniques advised in 5.13.1. Thanks.

Click to expand...

The HS spars likely had a slight bow in them even before the were put into the crate.
When you bend a long flange as on the spars, there is some stretching of material to the outside of the bend from the neutral axis, and compression of material to the inboard side of the neutral axis.
Add in a little spring back that has to be dealt with and you have varying amounts of force distributed down the length of the part which will cause it to bow slightly.
The bow in the VS-808 is from the punching process. Because it is so thick, the forces induced while punching cause it to curve slightly.