Chapter 18: Building the Canopy Frame
Step 11: Shaping the Canopy Frame Blocks
I did Step 11 vastly different from the plans!
First, I stacked blocks of blue wing foam onto the nose top and put a block of foam into the canard cavity. (The canard was removed for this process.) I made sure the blocks were tall enough to clear the nose profile templates. Since my tape line was set to 2.25 inches, all my canopy deck foam was hotwired to be 2.25 inches high. I secured the forward deck and canopy frame blocks with drywall screws coming up from under the shelves. With the canopy in place, I carefully shaped each block to match the canopy glass and marked each block's location on the shelves.
I removed the canopy glass and the turtleback. With the nose profile templates attached to the fuselage sides, I fired up the hotwire saw and dragged it over the nose profile templates to "carve" the nose top, canard cover, and forward canopy deck. I was elated as I watched the wire exiting the forward canopy deck foam precisely at the intersection point! (WARNING! DON’T ATTEMPT TO HOTWIRE URETHANE FOAM. It will produce a TOXIC GAS!) What could be simpler? What normally takes all day to do (cutting/carving the urethane blocks) took only 30 seconds!!
From there, I used a hacksaw blade and several flat sanding boards to rough the corners of all the foam into shape. I finished with a long, flexible sanding board made from a length of PVC strake foam with two sheets of sand paper glued to it. You need "the flex" to work around the corners and complex curves. I sanded at 45 degree angles (NOT side to side! NOT fore and aft!) until everything felt nice and smooth. I used my little joggle sanding tools to make the necessary indentations for the canard cover joggles, forward deck cut line, and the cut lines for removing the nose top.
Here are some pictures of this process. As you can see, there are far fewer blue foam blocks than the many urethane blocks per the plans method.
