3M Panel Bonding adhesive part 8115

[loman]

Has anyone used this stuff and if so what is your opinion. The front part of my fiberglass hood is still flexing badly at 100 mph in the 1/8 mile, and I'm afraid of running it again in the 1/4 mile because it seems to be flexing more and more with each pass. I installed a piece of sheet metal underneath the hood last week to redirect the air but it didn't help. After brainstorming the past week with a couple of people, we came up with idea to add some more bracing underneath the hood. I was going to fiberglass it to tie it in with the rest of the hood. Then today I stopped by a shop that builds fiberglass truck bodies for pulling trucks and 4x4's, even race trucks ( I never even heard of these guys but I stumbled onto them this morning). I took my hood to them and showed them the bracing that I had made and asked about fiberglassing it in. They suggested using the 3m panel adhesive to install my bracing and thought that would be good enough and I wouldn't need to fiberglass it.

[Lou's Comet]

I use 3M 08115 all the time. Love it !!

I use it mostly on steel but have used it on fiberglass before, I have never had it fail, yet. I was skeptical at first but when working at the ford dealership one of the techs used it to put a complete side on a cargo van. I really wasn't sure it was such a good idea, but within a year the cargo van got hit on same side, hard! And the adhesive held!

Started using it a lot after that. Wheel archs, rockers, door skins, etc. Been using it for over 8 years and haven't had one comeback. Used it on my comet for seam sealer. And plan on using it on my hood and the dash I am building.

Rough up area good with 36grit for a good mechanical bond. Clean really good with wax and grease remover and go at it. Put it on both pieces, I use a disposable tin brush, then run a bead on one of the pieces put it together, clamp your pieces in place and 24 hours later you should be good to go.

Plan ahead, fit the pieces and have your clamps and such ready, work time is around 45 minutes but about 30 mins or so it starts to setup at least in my shop.

You will need the gun for it. Buy the 3m gun, it will work with other brands. Watch pricing some charge a lot. I was getting it thru Summit Racing for like $38 a tube. The only local place that had it wanted $65 a tube. Talked my local supplier into stocking it and he sells it for same price as Summit. He use to sell SEM but I didn't like the Sem, was runny.

Lou

[poboyjo65]

ditto what Lou said. Looked at his build thread & after lots of welding & lots more to go I decided the price wasnt that bad when you figure in grinding discs ,welding gas & wire & the most important ,time & energy/work. it is welded & sealed all at once. paint-able too. you WILL like it. if any gets dropped on your concrete floor you better scrape it flat or if it has already dried sand it or it will pull a chip of concrete with it if you scrape it with a straight hoe!

[loman]

Thanks for the quick responses. That's the kind of info I was looking for and wanting to hear. I forgot to mention, my bracing is some thin 1" steel box tube, so I will be bonding steel to fiberglass. I found a supply house fairly close to me that sells it for $47 and the gun for $50.

Reading your response and reading the instructions online, am I right in assuming people are replacing panels and skins with this stuff instead of welding or is it a combo of both?

[Caveman49]

Yep, the guys above hit it spot on. The body shop in town uses it, and one of the guys told me that you'll tear or rip other metal around it before it gives.

[CALIFORNIA CALIENTE]

A set of hood pins is A LOT cheaper and they flat work!! ROY.

[Lou's Comet]

Thanks for the quick responses. That's the kind of info I was looking for and wanting to hear. I forgot to mention, my bracing is some thin 1" steel box tube, so I will be bonding steel to fiberglass. I found a supply house fairly close to me that sells it for $47 and the gun for $50.

Reading your response and reading the instructions online, am I right in assuming people are replacing panels and skins with this stuff instead of welding or is it a combo of both?

Good price for the gun!

Depends on the panel, most panels just glue on. Some you need to weld also. I do a lot of trucks. Fords the rear wheel archs on beds, GM the rockers. I glue .them all on now. Rockers on unibody stuff I glue and weld.
One of the nice things about the glue(and there are many) is don't worry about rust coming back. When you weld rockers (or any other repair panel) on the heat from welding burns the paint/coating off on the inside, and it will start to rust on the unsealed inside seam. With the glue I hit the inside of the rocker with a angle grinder to bare metal, then run 3/4 tape around the edges where the glue will be. Then coat the rest with POR. Once dry I pull the tape and have bare metal edge for my glue. Brush it on, brush it on the vehicle side, then run my bead of glue. When clamped in place the glue squeezes out on both sides and seals the seam/edge. Everything is coated and inside seams are sealed tight. Repairs that lasted 2-3 years now last a whole lot longer. Between the 8115 and the new epoxy primers rust coming thru and bubbles in filler are very rare.
Lou

Lou

[ec164]

I also used it to finish my engine bay after welding holes shut, so it could be sanded smooth and not melt like bondo when I had mine powder=coated, and it never moved, good stuff....................Al

[loman]

I already have 4 hood pins and don't really want to add 2 more. As for the hood, part of the problem I think is the thickness. The hood is about an 1/8" thick. When the hood is pinned on the car I can grab the front edge and with very minimal pressure lift the front edge of the hood and it comes up very easily. It is magnified when going down the track. I could possibly relocate the front 2 pins further forward and this might solve the problem, but then I have to fill the old holes and repaint the hood. I would also have to fabricate a bracket of some sort to weld onto the box tube core support frame I have. I thought it would be easier and less work to try to stiffen the hood with metal bracing by using the panel bonding adhesive .

[loman]

Good news.
The panel ponding adhesive on the extra support worked great. My hood didn't even think about moving last Sat at the 1/8 mile track. I don't know if I will get to try it out on the 1/4 mile, because we only be racing 1/8 the rest of the year at Gateway but I'm not sure.
Bad news.
We clamped the steel support pieces in place overnight while the adhesive cured. We used welders clamps with the least amount of pressure on them. We used some cardboard and some plastic underneath the clamp on the good side of the hood. I was holding that while someone else set the clamps. Well one of them apparently had more pressure than the rest and left a very noticeable indentation on the painted side of hood. Where I used box tube bracing that extends back to the middle of the hood it somehow deformed around it. We didn't even clamp that part. We layed a 2x4 across the 2 braces with a little weight on it. Looking at the top of the hood it looks like the fiberglass and epoxy tried to pull the tubing through the hood. Its not too bad, but it is very noticeable. Lastly, the front edge of the hood never fit real good, it always seemed like it was the wrong angle. Well once installed on the car, I noticed the angle is worse now. It somehow pulled that front edge further out. I don't know if that was because the reaction of the adhesive and fiberglass or maybe the hood had been weakened overtime from all the flexing and the curing of the adhesive exaggerated that. Hindsight, I would never had used clamps and just applied adhesive and let set up. Live and learn.

I will live with it for the rest of the racing year and may try a couple of things, but it might be new hood time this winter. We'll wait and see.

[Caveman49]

Bummer. Couple questions, do you have to go down the track with your hood on? And, what kind of 1/8th mile time you getting?

Thanks, and Motor Safe.
Lee

[loman]

You don't have to run a hood, but I want a hood on my car because it looks better in my opinion. As for 1/8 mile time, my last pass this weekend was a 6.46 @ 106 mph.

[Caveman49]

I was just wondering about the hood going down the track, yeah it looks good for sure. MAN, that is a kick A.. time for an eighth mile. I guess I need to look at some of your past postings to learn what it is you're running, HP, gear, etc....
Thanks Loman, and motor safe!
Lee

[loman]

Caveman, make sure you check out California Caliente and 383Merc's cars. They are more impressive than my rattle trap. I have a big block but they are running small blocks and are in the 10 second range in 1/4.

[poboyjo65]

Loman do you think you could cut the adhesive somehow, maybe try it again or do you think it has a permanent new shape?