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.

[gothspeed]

Modern adhesives are great and have many uses. Though for the 914 floor board I am not certain there is enough 'interface' area to get a strong enough bond. Being as it is the floorboard, I would weld it ...... maybe you can rent a welder if you do not see using it long term.

But if you want to experiment with this adhesive idea, one good metal to metal epoxy I am aware of that may suit this application is 3M DP-420 ........ I am certain there are others but that is a great one I know off hand.

[Drums66]

....There are some damn strong 1's
personally, I would'nt trust them on that! (IMG:style_emoticons/default/idea.gif) (weld)

(IMG:style_emoticons/default/bye1.gif)

[shuie]

Any other thoughts on this idea? I've already welded all of my structural panels in. Would the adhesive have made the joints stronger than welding? Would using something like this over an entire seam of spot welds make the joint too stiff? Im guessing this stuff doesn't flex at all once it is set.

[Mikey914]

Unless you have clean pretreated metal, with enough surface area for the required strength of the bond, this would be a mess. The good thing about the spot welds is they can be drilled and panels replaced pretty easily.
Just my .02

[ldsgeek]

Assemblies have to be designed for this process. It's not simply a case of replacing welding with chemical bonding. As has been mentioned, this usually means larger interfaces with the loads aligned in the best direction for the bonding agent used.

[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)

[raw1298]

I used it to bond on fiberglass flares.