Seam welding a shell

you cant really continuously weld car metal as it warps. You can tack and over tack to get a continuous weld but not make it in one weld due to heat build up.

I've heard good and bad on seam welding. There is a suggesttion that doig it to modern vehicles (ie those first built after about 1970) is a bad idea as cars were starting to get safety crumple zones by then - the car is designed to fold up and absorb impact forces in a crash. Seam welding affects this and causes crash forces to be loaded in places the vehicle disigner didn't intend meaning the structural integrity of the shell is not predictable.

So for a road car its probably not recommended.

As with cages and any kind of structural mods you need to know the structure of the car and what will work and enhance it rather than plonk some stiuff in and weld soem seams up and say jobs a good un.

I have had a little to do with seam welding in my time. If you plan on spending a fair amount of time doing hard driving its definately worth while.

The welds basically the best option is a stitch weld for various reasons, but the most obvious and biggest is probably to make it easier to tell if there is any damage from hard driving, plus if one weld crack it does crack the rest.

Definately do not weld up all seams. This is unnecessary and dangerous. It will affect certain danger reducing parts in the body design also leave the extra load on the same paces you are trying to avoid from happening as its all the same now (sorry thats the best way I can think to explain it right now). The best thing to do is weld up the trouble spots of your particular car, these are use areas around the suspension and so forth. Most cars are similar but you should check the specific models for specific problems. Best way is to get in touch with rally drivers/ car builders who are running the same car and see if you can get the trouble spots out of them. Just explain what your after and most of the time they will be happy to share and will save loads of time, and be much more effective.

Hope this helps a bit, feel free to ask anything else and I will do my best to help out.

The point about crumple zones makes sense when you think about it, the shell itself is pretty mint with minimal rot. i may well end up just stitching the front and rear turrets, adding a strut brace and some sort of roll cage, although the plan is to make it as light as possible .