Seam welding - Stitch welding ???
 

Wasn't sure where to put this. Thought about the race prep section but maybe it can go here since it is all BS anyway.

I'm putting together my donor Miata for the LS1 and this weekend I think I am going to do a little seam welding. I'm not exactly sure why I am doing it other than "because I can". I've got the interior out right now and I will be putting some of that cheap ass peel and stick foiled tar sheets (dynomat) in for heat/sound protection. Before I do I thought I would get the mig out burn some holes in the metal. I'm thinking just doing the seam on the door jam up to the windshield header on both sides. So, here's my question:

Any reason to do this? Any reason to do more than this one section for a street car? Advice/comments?

This is the area I was trying to describe:

http://www.flyinmiata.com/tech/seamw...a2c48fd7d4.jpg



BTW, I found this looking for the pic above. Cool!

http://monkeymagic86.files.wordpress...pg?w=614&h=459

sorry no comments on the seam welding other than it will give the car back its like-new rigidity.

but that pic of the "frog arms" makes me laugh. some people think if one hole is good, then more holes is better... but the fabricator probably negated most of the rigidity of the piece by drilling randomly.

Do it. 1" weld 2" gap along the entire door frame. If you really want to get nuts pull the seats, dash and do all the way across the car including the gussets.

cage

It is going to be a sleeper for the street, not a full on track car.

Apologies if this is a dumb question, but why the gap? why not one continuous weld?

I've seen it done both ways. I figured stitching gave less chance of warping. I see that Keith Tanner did a continuous weld on his Targa Miata.

I think one continuous weld would be too stiff. It would probably start cracking after a period of time. Either that or completely unneeded.

One of the first things i'm doing when I get my GTX back on the road is parking the miata in the garage for some seam welding. I've been wanting to for a really long time and since its my daily driver I just haven't had the chance.

One continuous weld would impart too much heat to the metal and induce unfavorable stresses as well as possibly weakening the metal overall (the HAZ that is). The gap prevents the metal from getting overheated while the "stitch" still imparts the desired stiffening.

When you seam weld, you always do it in strips so that warping can be avoided. You could go back and fill in the gaps. But as pointed out there is a point of diminishing returns. The seam area being even stronger by going continuous might not help much since other areas become the weak link. Most cars like the corner zones in a door entry to be strongest…see the sketch posted earlier. And on Miatas, the corners of the actual floorpan move, so Mazda beefed them up on the NB cars.

Now you tell me <G>. I just spent about 2.5 hours messing with the seams (not finished yet - probably another 2 hrs to go). You can view the progress/project here:
http://www.lightweightmiata.com/v8/seam/

http://www.lightweightmiata.com/v8/seam/seam07.JPG