Saturday, September 12, 2015

Shaping The C-1208 Canopy Foam

This was a slow week for making forward progress on the DOG Aviation RV-12. Having returned from Chicago after attending Marty’s memorial service, I have admittedly been in a little slump … and did not spend much quality time at the airport. Was hoping to fiberglass this weekend but a cold front has moved in … so will wait a few days for the temps to get back into the high 70’s or low 80’s before doing the glass work.

The recent drop in temperatures is a stark reminder that cold weather is right around the corner for this part of the country. After the canopy fairing lay-up is completed, I may not take the time to complete the finish sanding and smoothing of the fiberglass because there are plenty of tasks yet to be done that are somewhat temperature sensitive. The fuel tank needs to be assembled and sealed with Pro-Seal, along with sealing the firewall and miscellaneous places around the instrument panel and rear window. Plus, I would like to paint the fuel tank and some of the aluminum parts that came with the engine kit, and all of that requires warm temperatures … time to get seriously motivated again.

I did get a couple of small tasks accomplished this week beginning with shaping of the C-1208 canopy foam. It was nice to be able to roll the fuselage outside to sand down the foam blocks and not have a mess inside the hangar to clean up. Van’s suggests using a 15-18" long sanding block, but not having one that long (nor having a clue where to find sandpaper that long) I just carefully used a regular sanding block with 80 grit paper on it. Most of the block gets sanded away and although I could have used power tools, the foam block sands easily so I took my time shaping the block by hand.  It took about 45 minutes or so per side … good therapy.
Sanding the left C-1208 canopy foam and beginning the shaping process.
Completed right C-1208 canopy foam. The foam conforms nicely to the shape of the canopy skirt as can be seen in the area between my fingers.

Once the canopy skirts were sanded to shape the little aluminum inserts for the bolt tunnel were trimmed to the approximate size and bonded in place with a mixture of epoxy and flox. This is an addition I’m making and not part of the Van’s plans. Not really necessary, but it will add to a finished look when the glass lay-up is completed. The insert is just a little proud and will require a little filing to make it even with the foam. Also of note: The upper edge of the canopy foam adjacent to the upper edge of the canopy frame arms are to be cut down 1/8" below the edge of the arm. There is a small pocket visible in the photo below  - this area will be cut out anyway to 1/8" below the upper edge of the canopy arm … so no worries. After the foam material is removed and the area sanded, a mixture of epoxy resin and flox will fill this area and be immediately followed with the first lay-up of fiberglass cloth. The flox will provide a good bonding point for the lay-up.
The metal ring in now bonded onto the canopy frame. Went easy on the flox this round so as not to get any epoxy onto the bolt or washer. The remaining  small voids were filled later.

Van’s plans would have the builder doing the lay-up with the gas struts in place. Based on suggestions from other builders, the struts have been removed. I decided to make up a couple of foam block plugs covered with packaging tape to fill the void. These will be slathered with mold release so the fiberglass does not stick to them. I used the scraps from the C-1208 foam blocks and used two pieces to fill the void.
Longer foam block covered in tape is final length … aft foam block is being tested for a good fit.
Both foam block plugs in approximate position …. this should help hold the shape of the lay-up and keep epoxy away from the canopy deck.

Need to make the plugs for the right side later today and begin cutting out the patterns for the lay-up.