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Derek

Rust repair using panel adhesive

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When it came time to start repairing the rust my 240Z body I was trying to figure the best way for me to make the repairs. I have a full metalworking shop including a tig, mig, and spot welder so I had a few options to play with. I had been using some pretty awesome adhesives on my foundry patterns and thought I would investigate it more. My theory on the adhesives was that it would be better in two ways. The first would be no metal fatigue from the weld and the second would be superior strength because of th increased contact area. I did some research on the web and found that panel adhesive is some pretty spectacular stuff. I found plenty of tests where the metal would tear before the adhesive would fail. I purchased some SEM 39747 panel adhesive and an application gun.

 

 

 

Here's a shot of the first repair I did. This was not one I was looking forward to repairing. I decided that this was going to be a worst case test so I did a minimal of surface prep on the back side of the ¼ panel.

I roughed up the galvanized a bit and laid a pretty good sized bead around the piece. I was able to wedge it in place from behind. On other repairs I ended up using tech screws to hold pieces while they cured.

 

DSC_0006.jpg

 

Here's a shot of the repair. Notice how easy it was to repair the section between the ¼ glass sill and the patch panel. I just filled the groove with panel adhesive.

DSC_0008_001.jpg

 

I let the panel cure over night and gave it a few shots with the palm of my hand. Man was it solid, It gave off a thud like it was a solid panel. I made this repair about six months ago and have periodically rapped it with a rubber hammer and it hasn't budged.

 

 

 

 

Here's a repair I did this weekend.

refurb22007-12-08.jpg

I'm splicing in a repair panel on the bottom of the ¼ panel. The black stuff is por-15

 

refurb22007-12-09.jpg

 

I made a backing plate out of the left over material I cut from the patch panel. I screwed the backing plate to the inside of the ¼ and then screwed the patch panel to it. I then disassembled the piece and got the adhesive gun ready. I reassembled everything but this time with adhesive on all of the contact areas.

I made sure that I had a large enough bead so that it would create a water tight seal as well.

 

refurb22007-12-10_1.jpg

 

I stripped the clamps and screws this morning and man am I happy with this repair. It was a whole lot easier than welding and has rigidity about it that you don't get with spot welding.

 

 

I'm not sure of the long term effects of this but I read that BMW is using adhesives to hold on frame rails so they must be believers!

 

 

 

 

Derek

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This certainly seems to work well! If it does completely seal the rusted area from oxygen and water, then you've got a winner. You'll want to ensure that the back side is sealed as well. Perhaps some means of getting the POR-15 on the backside of the patch.

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Derek,

First of all, great to see you working on the car! Panel bond is acceptable for repairs in these areas a few percautions should be followed though. First the metal must be absolutely clean no moisture, debris or rust. Second the temp must be in the range specified by the manufacture of the epoxy. This is usually between 65 to 80 degrees but some require higher temps and primers to be applied. With BMWs you have to heat the area with a torch or high temp heat gun and apply the primer while the metal is still hot. Then you let this dry and cool. After that you apply the adhesive and they rivit the panels together with special blind rivits. Also I noticed a couple holes near the bonded area, DO NOT weld these up as the heat will compromise the bond. Use panel bond to fill those as well, just dimple the hole with a body hammer first. Then finish as normal with filler.

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Hi Rick

 

Yes I'm finally making it happen!

I'm taking the whole week off to get as much done as I can. This isn't a show car so I'm prepared for quite a few compromises! Thanks for the tip on the screw holes.

 

When are you guy's coming down for the shop tour? I hope to be blocking the primer this weekend so that would be a great time for a visit:eek:

 

Derek

 

Derek,

First of all, great to see you working on the car! Panel bond is acceptable for repairs in these areas a few percautions should be followed though. First the metal must be absolutely clean no moisture, debris or rust. Second the temp must be in the range specified by the manufacture of the epoxy. This is usually between 65 to 80 degrees but some require higher temps and primers to be applied. With BMWs you have to heat the area with a torch or high temp heat gun and apply the primer while the metal is still hot. Then you let this dry and cool. After that you apply the adhesive and they rivit the panels together with special blind rivits. Also I noticed a couple holes near the bonded area, DO NOT weld these up as the heat will compromise the bond. Use panel bond to fill those as well, just dimple the hole with a body hammer first. Then finish as normal with filler.

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I'm using SEM 39747 panel adhesive.

39747 MULTI-PURPOSE PANEL ADHESIVE is a non-sag, two component epoxy adhesive system formulated to bond steel, aluminum, SMC and fiberglass panels without the use of an external primer. 39747 provides long working times (90 minutes) allowing body shops to correctly position parts for proper alignment. This adhesive contains glass beads to insure adequate bond line control. 39747 is an easy to use 2:1 adhesive that forms resilient bonds and maintains its strength over a wide range of temperatures. 39747 is suitable for bonding a variety of substrates, especially automotive grade cold rolled steel.

 

 

what is the name of the product you used i am very interested.

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Yes you can. This stuff dries hard as a rock. I read about some complaints/concerns about shadowing through the paint but I think I'll have enough filler over everything to stop that.

 

Derek

 

wow, i never really gave adhesive a second thought, as i thought you had to overlap. but your fixes look great, and it looks like there won't be a great need for too much filler.

 

can you grind it after it cures?

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No more than a 1/4 of th tube. Probably less. Don't forget you need the dispensing gun as well.

Derek

 

I did a search for this product, and I found 7 oz. containers for about 25 bucks. How much of this adhesive did you use for that quarter panel fix?

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Guest adhesive tape

The ideas screws is really admirable and great work Derek. Keep on posting your ideas in this board. Thanks for the share.

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Hey Derek,

 

How are the bonded patches holding up? Just curious.

 

Cheers,

Ross

 

Hi Ross

The patches behind the 1/4 glass are fine. In the right light I can see the seam on the dog leg splice. Some of this may be due to shrinkage. I had a limited time to get the car done so I had to rush the cure times on the primers. I've got shrinkage in a few other areas as well. I should have let the high fill sit for a couple of weeks before I sanded. It's a daily so it's no big deal. Better prep may have made a difference on the seam as well. I was really powering through everything. I didn't strip the car so rust that I did'nt uncover during the body work is starting to pop up.

My plan was to get a decent paint job on it. Fix the small rust spots that pop up over a couple of years Then repaint. Of course I'll have to do it again and again and again.......

 

Derek

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