Aluminum Delaminating from Wood Substrate
Question (WOODWEB Member) :
I was called in to try and help. All I could do was lift the metal with a hot air gun from the closer end to the humps, shoot fresh contact on it, and roll the stuff back out. Sure enough there was an extra sixteenth to eighth of an inch hanging over the ply when this was done. It got the humps out but there were some ripples.
Why did this happen? Could it have been avoided by using one of the metallic face HP laminates? I ask because my gut says this isn't over yet, and I want to have the right answer when asked. My client used the architect spec'd fancy aluminum, and I think that is where the blame begins. Thanks in advance for all responses.
From contributor S:
Also, did you backer the 1/4" birch? It is floating on standoffs and the backside exposed if I understand your description.
From contributor F:
I think you can still have a problem using the laminate backed material as I believe your right in that it was a contraction problem. I'm guessing the baltic birch, and possibly the material under that have shrunk over the winter months. This is what likely caused the metal to do what you’re describing. I had a similar problem happen on a large commercial bar I built. I used a combination of Neatform and wacky wood to make up the curves and laminated with HPL. As I was attaching the material directly to the curved wooden frame I did not use a backer material. After the first winter the seams between the 12' long HPL sheets had opened about 1/16"! Unfortunately I'm not sure I can offer any resolution for your problem as I believe it is likely more than skin deep.
I think you've been visited by the evil unequal movement monster! Aluminum will expand and contract due to changes in temperature and the ply will do the same as a result of moisture increases or decreases. Short of using an aluminum backer substrate I don't think you will ever get the two to behave well together! I would check into sign maker substrates to see if you could find an aluminum honeycomb substrate that would allow the level of bending you need and go that route. I did a liquor cabinet a couple years ago for a privately owned helicopter and used 5/8" aluminum honey comb panels that we got through a local sign shop. Assembled using mechanical fasteners, epoxy and covered all outside visible surfaces with ebony veneer. We met the weight requirement and the FAA said it met their requirements. Bet something like that but maybe 1/4" thick would do the trick for you!
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