Wed Jun 2 2010

Sub floor work

...not sure if I've mentioned this before or not, but I'm going to add some fireproof insulation to both the back of the firewall and the floor of the footwell. The insulation I purchased is good to 2000 degrees F and seems similar to fiberglass insulation. It's soft stuff, so I'm going to encase it in an aluminum foil "envelope", then trap the envelopes (one per are) under sub panels for both the floor and firewall. I had previously purchased some .032 aluminum for the floor and some .020 for the firewall and today was the day I started working on it. Since I don't own a large enough shear to cut these panels, I decided to give a try with a pneumatic hand shear from Harbor Freight. Hopefully this thing works well, but I've got my doubts. I've had quite bad luck with stuff from Harbor Freight, but maybe this time it'll be different.

Well, examining the cutting blades doesn't fill me with confidence. The surface finish is quite poor and there's a significant gap between the moving blade (center) and the stationary blades (sides). I think I'll give it a try on a piece of scrap first.

Well, it actually does cut the aluminum. It's kind of a jerky process as the blade has very little travel and the bad finish on the faces of the blades kind of digs in to the aluminum. I'm definitely going to have to cover the area with tape to cut down on scratching / gouging.

OK, I marked out the sheet (with a bit of extra material) and clamped on a straight edge. Let's give 'er a go!

Arg!!! Yet again I've been bitten by the crappy stuff at Harbor Freight. The crappy surface finish and resulting gouging and jerkiness made me jump the edge of the straight edge. This POS is going back to Harbor Freight pronto.

Well, I finished the cut with snips.

On EAA's Hint's for Homebuilders, they describe how to "creep up" on your finished line to avoid distortion, but I can see that my snips have such agressive teeth that I'm not going to be able to get a clean edge. I need to come up with another solution.

I dunno why I didn't think of this earlier. My dad had described this technique to me long ago for making straight cuts on wood panels, so I thought I'd give it a try on the aluminum panel. It worked great...just clamp a straight edge along the sheet, use a straight cutting router bit, and run the router along the edge. The only improvement I need to do for the next cut is to cover the exposed surface with tape. Some of the chips got caught between the router base and the surface of the metal causing scratches.

Here's the panel cut to rough size. I need to make two bends...a 90 degree up bend in the front and an 78 degree up bend at the back edge. I'm going to give Tom Thompson (my buddy Scott's dad) a call to see if he has a brake and would help me out.