Sealing the Wood?

[SteveH]

I'm at the point of preparing the wood prior to covering with aluminum on my tear. I've put one coat of thinned spar varnish on it, but was wondering what your woodworking gurus thought about it. How many coats of varnish do I need on the wood under the aluminum to seal it?

[Guy]

Dear SteveH,

Max out just one more. Use some synthetic steel wool over the thinned layer you have. Put on one more coat. Then choose your glue(hehehe) carefully. Spar Varnish is flexible so it does not crack when the spar on a boat sways in the wind. It is actually a good choice for the sealant under the aluminum since aluminum shrinks and expands differently than plywod. Make sure you choose a flexible glue.

[TRAIL-OF-TEARS]

I thought the glue was just a temporary hold for the aluminum while you put the trim on. It is the trim that holds the aluminum on. Am I thinking right or am I way off. Guy, what would be a flexible glue? would a silicone adhesive work? Thanks

[Dave M]

try something like 3m 5200. its a very tough adhesive but slightly pliant so it will flex just enough under the aluminum.

my understanding is that you should have both glue and trim to hold it on. Many peoples panels break free of the glue bond (due to non-flexible glue) and are ok with just the trim but look somewhat deforemed.

[norm perkiss]

I'm not to the aluminum siding stage yet, but I have been watching the board for technique. My observation is that it's about 50-50 on "gluing" or just letting the aluminum "float". It seems with the edge trim, door trim, fenders and anything else you can think of to bolt on, the aluminum won't go anywhere. I'm going to float mine.
Norm

[SteveH]

Don't know his last name, but I spoke with George from the teardrop fix-it shop today about this very subject. George has been repairing and building original type tears for 11 years. He tells me to use ordinary contact cement to glue on the side aluminum, but wait until it is a hot day and have the aluminum out in the sun and hot before you put it on. He said by using his method, it will stay on and not bubble.

[Guy]

Gents, The best, easily available, and inexpensive flexible glues for bonding Aluminum to metal are 3M77 and 3M90. Both are available in spray cans so they are easy to use (and the spray is low mist so they do not get on everything). I believe that "90" does not begin to weaken until about 160 deg F.

I would not use 3M 5200, a rather fine adhesive, in this case. 5200 is a marine sealant/adhesive that has great properties in a marine setting, ie salt water and water line joints. However, it is not that great in the type of high heat that beats down on the top of a tear in summer.

Ordinary anything will give you ordinary results and you should get more for your hard work. The above glues may cost 2 or 3 dollars more but they will last.

As for application, especially when using two different materials, put two coats of spray on each material. Spray them both with one lightcoat and then take an hour break, come back spray again and attach.,

[asianflava]

Gents, The best, easily available, and inexpensive flexible glues for bonding Aluminum to metal are 3M77 and 3M90

I have a can of "Super 77" is that the same thing? Black can with white and red writing.

I've had it for maybe 6 or 7 years. I don't even remember what I have it for. I used to use it to glue carpet to subwoofer enclosures but I haven't made an enclosure in more years than that.

[Guy]

Yes, it is. Hopefully, newer than 6 years old. This glue does its job so well you cannot buy it in California.