Originally Posted by deadbodyman
It all depends Kevin they both have they're advantages,but the only way a flange joint will hold water is if it done upside down...The original panel has to be flanged not the new piece the open edge of the joint is facing down then when your done welding you seam seal the whole back side of the seam...
On a long seam I prefere a flange because its stronger and straighter when done needing little to no dolly work...as long as you prepped the flange so its not wavey ,if its wavey when you start it'll be wavey when you finish.
Butt joints are more likely to warp a panel but since the joint doesnt have the two layers its not as strong and can be hammered and dollied back into shape when it warps (and it WILL warp) another advantage of a butt is it can be dressed up on the inside and wont be noticed, a flanged joint is obvious from inside the trunk ....So you really need to know how to do both so you can decide which one is best for your applicationbut even a flanged joint has butts at the endsIts alot harder to make a proper flange joint but easier to weld butts are way easier to make but harder to weld.I do both ,but on long seams I do a lot more flanges than butts...
exactly. The guys that swear by open butt welds on everything are either used to production and small sail panels (Toyota recommends it), have never done them on big seams, or will Tig weld it and are very good metal fabbers. The metal fabbers will tell us and show us but if they aren't that good luck finding one of those guys actually showing you he does this in a shop environment on a long seam. The only reason I'm doing it is cause you upped my confidence in doing it with your suggestions that makes it easier, the flanger won't fit, it's cut uneven due to a last minute change of plans, it's in an area that will hold the metal against warpage, and I'm filming it, so there some ego involved for sure.
Most times I'd just play it safer and flange, and not feel an ounce of guilt about it.