Wednesday, September 5, 2007

Hot box progress

This morning I wired a switch for the hot box; this took a couple tries, I just don't think intuitively when it comes to electricity I guess, but it turned out:

I also installed four casters on the bottom of it, so it rolls around the garage easily. Last night I bought a small roll of reflective foil-based insulation:

After wrapping, stapling, and taping this on three sides of the box, I had this:

There still seemed to be too much heat loss out of the front though, so I ended up sealing the front with the insulation as well, and cutting a small slot for the foam to slide in and out. Look, the Heat Box Monster is sporting a yellow tongue:

My box is only about 4.5 feet long, some of the longest hull-side planks need about five feet, hence the extra foam hanging out above. Not a big deal.

Closing off the front produced a dramatic improvement. After only about five minutes of exposure the part of the foam plank that was inside the box felt extremely pliable and soft. Almost too soft -- when I experimented with laying it into the mold, it was very easy to make depressions in the foam by pushing against it. You can also see that one end of the plank exhibited some scalloping:

Still, the hot box experiment is showing great promise at this point. I'll have to get an egg timer (wife is gone, I'll go and check the kitchen next) and experiment some more to figure out the appropriate exposure times. Then I'll mount small grab handles on top, and perhaps a small lawn mower engine to make it self-propelled, etc. Haha, just kidding.


allen said...

Hi Jay,

I botched a few planks before I got the time and temp right. In my case, I found that the trick for me was to pull the foam out BEFORE the heat fully penetrates the foam. For two reasons. one, doing this will prevent the foam from ever getting too hot and ruining itself by puffing up. Two) if the interior portion of the foam is allowed to remain relatively cool, it acts as an internal guide that helps the foam bend more uniformly. In other words, it becomes the neutral bending plane where by the surface of the foam on the concave side compresses while the convex side stretches. ( if the middle 1/4 in. is still somewhat firm, It holds itself true like an internal batten.)

Jay said...

Thanks for the comments Allen. After reading your response, I'm a bit concerned that the thinner foam (3/8") on my F22 may not respond as well to the heatbox treatment -- there's not much "interior portion" available in 3/8" foam. I may experiment a bit more though.