Amerimax painted aluminum trim coil looks good for the skin. It is .018 thick with a durable paint coating on both sides and available at Home Depot in 24" x 50' rolls for $.75/ square foot. One roll will do 6-7 tails. Oh well. No need to worry about cutting mistakes. I could also get some with a pvc wrinkle pattern coating which would reduce denting and possibly create a slight golf ball surface effect? This stuff is .021" thick and $80 for a roll. Not that any of it is prone to denting. It seems to be a rugged aluminum blend that I was basically unable to dog ear the corner of with my finger.
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Amerimax Home Products, Inc.
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After looking at every piece of plywood in the store, I have also decided to just go ahead and use the 3/4" MDF that I have on hand for the spine and bulkheads and then skeletonize them with cutouts to save weight. It is rugged, takes a screw in the edge or glue with incredible strength, never warps and can be sealed with spray paint better than plywood. It is much heavier than forming with aluminum but will go together much quicker and is cheaper.
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I also finally came up with a solution to sealing and latching the front door to make sure it is convenient and water tight. Ready? Magnetic gasket. Duh! I racked my brain for weeks with different ideas on how to make the door stay shut and seal. Now I can use a light weight hinged aluminum panel sticking to a galvanized steel sheet track glued over the MDF bulkhead. Fit, flatness, and rigidity of the door will be complete non issues. A simple pad lock keeps it all safe when shopping or out of town.