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Panel Adhesives study

Due to the growing use of panel adhesives in collision work, guys in the resto-biz, as well as home resto-buffs, are asking - and experimenting with - the idea of using panel adhesives in replacing panels onto old cars. But is that a good idea?
 
I'm an old-school guy that has tried to keep up with the trends. For sure, the new panel adhesives are VERY strong, but while few -  if any - resto shops I know are glueing things like floorpans in, collision shops are definitely glueing quarters and some other items. The important part is to understand that MOST adhesives used by OEMs have no place in the body shop. For instance, structural, or load-bearing, adhesives are usually applied at the body-in-white stage when metal panels are fresh from the presses and covered in forming oil, and plastic panels are still covered in mold-release chemicals. To cure, they require temperatures as high as 130°C. Not only is that temperature hard to acheive in resto (or backyard!) shops, but also, everything around it would have to be able to survive such high-temperature bake cycles. 
 
At the manufacturer, lightweight steel cars are made with tailored blanks and bake-hardenable steels, as well as aluminum, and are using this joining technology as well as adhesive bonding, laser welding, and mechanical fastening. At Lotus, for example, engineers use a combination of mechanical fasteners and adhesives to assemble extruded aluminum frames. The BIG difference in resto's is that the panels are not in the same state as are the fresh, new panels atthe manufacturer. There's dirt, rust, undercoating and more to contend with in an older car - any or all of which can compromise a panel adhesive.

OEMs are investigating new adhesive/welding approaches to repairing vehicles, but again, this is still different than resto-work. Weld-bonding combines spot welding with a structural adhesive. That's the method that may be something best used in replacing floorpans in a resto situation. While I've used panel adhesive to repalce a newer quarter panel (section), it wasn't an entire quarter and did require a fair amount of overlap to glue to. At this point, if it was me replacing a floor pan or trunk section, I'd still weld it solid, but soon I'll be taking a crack at the adhesives in some of my restos. What it comes down to, is that much of the strength of the earlier cars consists of the welded floor, quarter and other panels, while the newer Mercedes are engineered to accept being glued at different areas.

Not sure if that helps, but that's my humble, semi-educated, opinion as of today. I'll add more info (and experience) as more becomes available.                Cheers, E-tek Restorations.
 
 
 
 
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