Science Project: Panel Bonding Adhesives Options

[shuie]

Has anyone ever done a floor pan replacement or other major structural metal replacement with panel bonding adhesives instead of spot & seam welding?

The bond is supposed to be as strong as a proper weld, there would be no worries about overheating and warping the metal, the entire seam would be joined & sealed which should make the tub A LOT stiffer. It would certainly be cheaper than buying a welding rig. I guess the downsides would be that working within the setup time for the adhesives could be difficult and you would need a lot of clamps. Maybe the unibody would be too stiff if every seam was joined like this?

My interest in this is academic. This is not something I am planning on trying since I've already welded almost all of my replacement panels in. I do need to use an adhesive to attach a fiberglass piece to my steel hood and I've seen threads on the forums where reputable shops have attached metal flares with adhesives so I thought I would ask about it. I'm sure there is a good reason why I have never seen anyone use the adhesives for something like a floor pan.

[shuie]

I have a couple of small things left to do on the car that I could weld, but I am going to give this stuff a shot. I went to the local paint supply shop and bought some. It was $60 for the gun alone and another $30+ for the adhesive, so it definitely isnt cheaper than welding wire and shielding gas.

(IMG:http://www.914world.com/bbs2/uploads_offsite/lh6.googleusercontent.com-2075-1354930154.1.jpg)

After working with it today I can say that it is definitely not as easy as welding either. The clamping would be a huge PIA on something large like a floorpan. I guess you could use self tapping screws or rivets or a floorjack to press everything flat together while the adhesive cured, but it would be clunky to work with. I am going to try it first on my firewall bushing & my reinforced clutch tube. The firewall bushing will see almost no stress and the clutch tube will see a good bit. I'll update this thread if either fails.

This particular 3M part no. has a 90 minute setup time and 24hr cure time. I read through the material sheet and it says you can weld through this stuff before it cures, but not to use it over a weld thru primer. I also talked with the paint shop folks and they said the way to use it is to tack weld the panels in and then run a seam of the adhesive. The guy at the shop says he doesn't know if the bond is stronger than a weld, but that he uses it for roof skins, door skins, and quarter panels and has never seen a panel separate.

(IMG:http://www.914world.com/bbs2/uploads_offsite/lh5.googleusercontent.com-2075-1354930155.2.jpg)