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Contact adhesive for open cell foam - seat rebuild [TR4A]

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Popeye

Popeye

Obi Wan
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Hi all,

Just curious what the collective wisdom is for using contact adhesive on open cell foam. I am rebuilding the seats on my TR4A, and am using Weldwood high temp Landau adhesive https://www.dap.com/dap-products-ph/weldwood-landau-top-trim-high-heat-resistant-contact-cement/ at the suggestion of several folks here as well as on a hot-rodding forum. I am brushing, not spraying it on.

I have made a few trial bonds with the stuff and am struggling to get a strong bond... I am not getting an "instant" bond, and am able to pull apart the pieces a few hours after assembly. Some seem better than others, but none are "strong".

Questions
1. How thick should I spread the stuff? Right now I am putting down one coat on the foam followed immediately by a second coat. Should I put one coat, let it soak in and cure (~10 minutes), and then a second coat?
2. I am using a foam brush - should I use a bristle brush to apply more adhesive?
3. How important is clamping? When I assemble the seat, it may be difficult to get a strong "clamp" while not distorting the thick foam and seat cover.

Thoughts and suggestions are appreciated!

Thank you,
 
I have never had good luck with liquid contact cement on foam. I suspect my problem has been "patience". The open cell foam tends to wick the adhesive down from the surface. That makes it hard for the glue to skin and form that "tacky but not wet" condition you need to get the two surfaces to stick together. I suspect I just never waited long enough for the solvent to evaporate before trying to stick the surfaces together.

For my last few projects I have used 3M spray 90 (green can). 3M 90 is a contact adhesive so you apply it similarly to liquid. Spray it on both pieces of foam and wait a few moments for glue to skin and become tacky. Carefully align the two pieces and push them together. This has worked well for me on fixing foam, attaching vinyl, and other bits of trim.

I also have found 3M 90 to be very handy with metalwork. I will often print out a template full scale on an inkjet printer then bond it to the sheet metal with the spray adhesive. Cut to the lines, punch holes etc., then use lacquer thinner to remove the template and clean the surface of the metal.

EDIT: If you want to try 3M 90, you will find it at DIY centers like Home Depot and Lowes.

EDIT2: Sorry, I really didn't answer your direct questions.
You are applying the glue to both surfaces aren't you? If not, that's a fundamental problem. Apply a uniform, not too thick coat to both surfaces, wait until they are both "dry" but "tacky" then press them together. No clamping should be necessary.
I have never applied more than 1 coat of contact adhesive to each of the surfaces to bond. Time is not what you are after. As I mentioned above, touch the surfaces to inspect the glue. Don't join the two parts until they are both "dry-tacky". Again, no clamping will be needed. As soon as you press the surfaces together they should stick to each other. Attempting to pull them apart should tear the foam.
 
Thank you Doug. I am applying the adhesive to both pieces. The reason for using the brush on kind vs spray, is folks in cyberspace say that some sprays do not last well in a hot car interior. Obviously there are "good" and "bad" quality sprays; the 3M 90 you mention seems to be classified in the "good but expensive" column by said experts, as it is good for elevated temperatures.
 
Like Doug, I have found the 3M spray to work better than brush-on for upholstery (soft or flexible) stuff. For example, covering metal with vinyl. Although it initially sticks, it eventually fails. YMMV.
 
To conclude; I decided to stick with the Weldwood adhesive. (Mainly b/c I spent about $50 to get the darned stuff - not to ignore the collective wisdom of the BCF!) I found, after 24 hours cure time, it makes an awesomely strong bond (stronger than the foam), and remains flexible. I had not let the adhesive cure long enough when I made the original post.

My process is to apply a light coat of adhesive to the foam (both sides), let cure for about 5-10 minutes, then apply a second slightly heavier coating, let cure for 15-20 minutes and then glue. I find when using the adhesive with open cell foam, that it does not permanently "grab" during initial contact. This allows for some fine re-positioning of the parts. Once all is aligned, I squeeze as best as I can, and then let the assembly sit overnight before applying stress to the part.

Note, when gluing the vinyl / foam center support cover to the aluminum cover, I had immediate permanent stick; as there is much more contact between the two pieces.
 
Also, inspired by a photo in Alan Turner's excellent article on seat rebuilds, I found medium binder clips to be a perfect temporary clamp when assembling the seat covers. The seat covers can slowly be eased into place, pulling in various directions to get everything smooth. When satisfied with the fit, one binder clip can be removed and replaced with the permanent clip.

Seats3.jpg
 
Thanks for the update. I'm glad you found a little more time was all that was needed.

You will also find the binder clips are very handy when fitting new convertible tops to the front rail. I keep an assortment of the clips in the garage for all sorts of uses.
 
There are two Wellwoods, One with solvent and one water base. I would use the waterbase on anything with vinyl. The other will grip for 6 months and then pull the backing off the vinyl. With both, the true bond is after 24 hours. The solvent will grab harder at first but the waterbase catches up at 24 hours.
 
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