by noseoil » Sun Oct 04, 2015 7:53 pm
I use a saber saw with a metal cutting (fine tooth) blade to rough-in the cuts. Basically, it's a magic marker line traced around the edge & I leave the line when I cut. That leaves about 1/8" (which is bigger than it needs to be), but that way there's room for error when mounting the sheet to get it in place.
When I did the side panels, I just used 2 wood blocks to keep the sheet from falling (an 1/8" saw kerf to hold the aluminum from moving) and hold it for marking. My wife held it in place while I ran the magic marker along the edge to get the line I wanted. It was then set on some 2 x 4's (carefully!) face down, & cut from the back side, since the saw will scratch the metal if you aren't careful. I would use a heavy tape (the Gorilla tape) to protect the surface if you will be cutting on a finished face. Keep the tape out of the cut or it can help clog the cutter.
To install the sheet, I didn't want screw holes or staples in the face, so I ran contact cement along the top edge of the cabin side & on the aluminum sheet on the back, only about an inch wide, just enough to hold the sheet. This lets you position the sheet on the blocks at the bottom, slide it where it needs to go, hold out the top to check things, then spot it in place. Once it's held by the glue at the top & the blocks at the bottom, I went ahead & coated the rest of the panel along the edge (the front & back edge) to hold it for trimming. It's basically like doing formica work, only you float the center & just do the edges. The glue acts like a bunch of clamps. For a finished trim, it's held well enough to take a pass with the router (tape or scratch). I wouldn't rely on the glue to actually hold the panel permanently, but for assembly it's quick, easy, cheap & effective. It's like having a clamp wherever you need one, just don't "spot" it until you're sure it's in the right place.
I use a 1/2" flush-cut bit with a bearing on the bottom. A solid nub at the bottom will work on formica, but it will just burn the edge on most things, so a bearing is the way to go. If you keep it oiled (just a drop of motor oil from time to time) the bearing will last a long time. If not, as soon as it heats up it will die. As long as you have less than 1/8" of aluminum to trim, it doesn't seem to want to clog. Any more than that & it starts to melt the edge & you have to stop to clear the bit.
The sheets are really held in place by the screws & trim, doors, windows & hardware, so if the glue joint fails, it doesn't matter! Hope this helps. Let me know if there are any questions, but this seems to be an easy way of dealing with things without a bunch of clamps & tape.
P.S. The butyl rubber tape is applied to the flat side only. It butts into the short edge & stops there. If it were placed on both surfaces, it would be impossible to get a clean edge and have it pull tight & uniform. With the tape on the "flat" side of the trim (the wide flange), once the screws go in to push down, it spreads the tape & squashes it sideways. This should be enough to cover the edge of the sheet. I didn't run all the screws down 100% tight at first. After sitting in the heat for a while (90+ degrees here), the tape spreads out & I can tighten them just a bit more. I don't think I would have as good a time if it was cold out, the tape is not nearly as pliable when it's too cold. I use a cheap Ryobi 18 volt cordless drill with a clutch. Since stainless steel screws are fairly soft, I set the clutch at about 4. I drill a pilot hole for the screw body, so only the threads bite into the wood to provide the grip. I have places with screws every 4", 5" & 6", depending on how tight the radius of a curve is. On a long flat run, it's 6" on center. On a small curve it's 4".
Last edited by
noseoil on Sun Oct 04, 2015 9:59 pm, edited 2 times in total.
