Epoxy Panel welding vs. Tig, anyone have any experience?

[Gearbox]

Fitted up new outer rockers, Rocker support, fender support, and door jamb, and despite using some repro parts when OEM was not available, I was able to get a perfect fit (lots of grinding and pounding on the repros). Started to notice the way these parts were joined. Outer rocker attaches to the top threshold seam where the floor panel and inner rocker come together in a "C" channel. Bottom edge is welded right onto the floor panel. Rear is welded to the inner rocker support with the quarter attached to the sides, and front is left pretty much open with the top attached to the hinge post and sides and bottom front tacked to the fender support. Yeah, it does add some structural support, but from what I see, about 10% if that, with the bulk, if not all, being supported by the inner rocker/floor/console structure. Even with the rocker and rocker support off the car, I did not notice any deflection no matter how the car was jacked, and there was no door gap deviation.

Now, I have experience in monocoque fabrication for my race cars where the entire chassis is built from aluminum sheets, bent, riveted, and epoxied together. So, my thinking was to epoxy these panels together using stainless steel countersunk head blind rivets every 1.5" or shorter. Given the epoxy bond which is being used solo on new cars to hang quarters, door panels, and roofs, coupled with the SS rivets with 700 pounds of tensile shear strength each, it should be as good, or better than just spot welding or tig'ing every inch or so. Plus the counter sunk rivet heads could easily be covered with a thin layer of bondo, and most of them will not show anyway.

Biggest problem with welding is the tight corners and "C" channels that is almost immposible to tig, or spot weld even if I had a spot welder. Plus with lots of hidden spots, I'm thinking that this epxoy/rivet combination may just work. So has anyone out there ever use this system? After all, the original "real" Hummer was completely put together like this. Any thoughts or structural engineers from 3M out there? Thanks Allan

[Eric911S]

Hello: Since you seem to know what you are doing on the fab work why not use a mig welder? They operate at lower temps than the Tig and you can get the wire in places where the tig tip and rod can't. You could rivet and bond the panels just the same way belly pans are put on formula Fords. It will be strong enough but again will take some time and not look right. I drill 3/16 holes where the weld will go and fill it in to look like a spot weld. They look great and original. Good luck with your project. Thanks Eric

[Gearbox]

Ok Eric, you found out my secret.........I SUCK AT MIG. Oxy Acetone, no problem. Tig, adequate if I get the machine setting right and there is no breeze. But for some strange reason, Mig eludes me. But it might just be the Mig. Bought it off a snap on truck years ago. Tried gas mig'ing, then switched to the gasless wire. No success. The Lincoln Tig 185 I have is a great machine, but the Mig is a no name (outside of the Snap On decal) and I had nothing but trouble with it. Had a few freinds try it with the same results, yeah.....must be the equipment lol.

The reason I brought up this topic is that with all these new chemicals and epoxies for automotive use, why wouldn't we use this new technology. Seems like more and more cars are being built with them, and from a use stand point, it's tons easier, especially when the panels are slightly off. Much easier to draw panels together with rivets and have the epoxy hold along 100% of the joint than trying to weld the gap with spot welds. I was acutally expecting someone to chime in about the originality, and rivets, although well hidden, would be a taboo. Or that someone had catostrphic failures with the joints. But this is what I'm doing today, epoxy, and SS rivets every inch for the rocker support. I'll have my website updated with more pictures this weekend of the whole rocker assembly and repairs. Let me know what you think, thanks Allan http://www.thelolaregistry.com/Proje...rsche_911s.htm

[Eric911S]

Hello: Stop right now and go to Home Depot and buy a Lincoln mig welder. The 110 unit is great. I have used many migs and some really suck. The Lincoln or Miller are great units. The Lincoln I have is the SP 125 Plus an older model with a gas mix. It weldes flares on with no deflextion. I have used the tig you have and they are good for thin stuff but not the great for thicker aluminum. On a side note the Miller 110 plasma cutter works well on body shop parts. I had one and loaned it to a friend and he liked it so much he bought it from me. Now I need to buy another one. Lastly buy a good mig welder it will be the best $300-$500 you have spent in a long time. Good luck with your project. Thanks Eric

[Zeke]

Having done a fair amount of this work, I support your epoxy and rivet method. One advantage to the welding method is the ability to form as you go.

[Gearbox]

Did the epoxy/rivet method today. Had everything trial fitted three times with colecos for minor tweeking before I started so everything fitted right up. I would buy the mig in a heart beat (I like equipment), but after buying two at north of $500 each with utter failure, I've given up for now. But eventually, I'll break down and get another better known one. Thanks Zeke for the affirmation, I put correctly sized countersunk stainless rivets every inch and made sure I got a gapless joint and a perfectly flat seal btween the panels. With the epoxy and rivets, the entire assembly of the rocker support, outter rocker, and door jamb formed a very solid structure. I weighted the rocker up and down after it set up and it didn't budge. I'm confident it'll withsatnd daily use as good or if not better than just spot welding. Now for a bit of bondo to cover up the rivet heads and I'm on to the ohter side. Thanks again for the help, Allan

[DynoDave]

Gearbox,

I too am an advocate of using panel bonding adhesive wherever possible. I have done this type of repair in the past w/ excellent results. It looks like you have done an excellent job pre-fitting your panels.

Using the rivets to position the parts is esential, however, you may consider removing the rivets & filling the holes with additional panel bonding material. My experience has been that over time, the rivets can work loose & if they do, they will show up under your plastic filler & final paint work as small circles consequently ruining your finished product..., something to consider for the long run. Did you use 3M's 8115 panel bonding adhesive? The 3M material is an excellent panel adhesive w/ very high tensile strength & very good anti-corrosion properties.

Dave

[Gearbox]

Hey Dave, yes, that is the 3M product I used and thank you for your kind comments. Interesting that you bring up the rivets. I too was thinking about that. Fortunately, I hid the majority of the rivet heads in areas that would be covered up by weather stripping or undercoating. But I am contemplating removing them where the door jamb and quarter are joined, right at the edge of the door gap, and the "dog leg" that I made. Plus these are the least or non stressed areas. I've used this type of method in constructing monocoque race car chassis, bonding aluminum panels with structural rivets and epxoy with excellent results. Plus the rivets do the heavy lifting in that application. I found that with this new 3M stuff, the bond is so good, the panels do not have any room to vibrate or twist so rivets coming loose may not be such a big problem. Additionally, the rivets are coated with this stuff. The only drawback with the epoxy is that if there is some rust under the bond, the epoxy will lift. So the rivets would be a good back up......I hope. Thanks again Allan for an up to date progress on my 911, check out "Project Cars" on my website www.ThelolaRegistry.com