DRY FIT THE CANOPY FRAME
While waiting for cement to cure on the stab and elevetors during construction of one of our kits, I took advantage of the break to cement up the canopy frame assembly. First dry fit the 1/8" (3mm) plywood canopy frame parts (two side rails and the forward and aft bows) in the cockpit opening of the fuselage and check fit and mark with a fine point pencil where trimming or beveling is required.
CEMENT THE CANOPY FRAME
Next, after trimming any parts as needed, tape the frame parts in place in the cockpit opening leaving about 1/32" (.75mm) between the edge of fuse and edge of frame to accommodate the clear vacuum formed part. If some of the parts are too large or their inner edges not perfect or perfectly aligned, don't worry about it now, the entire part is going to be filled, sanded, primed and painted prior to mating with the canopy or the aircraft.
Chop some glass fiber cloth into fairly fine chunks and mix with five-minute epoxy and force into the joints between the side frames and bows. Don't worry too much about getting a fine line of cement on the fuse - notice I didn't put plastic wrap down - the fuse still has mold release on it from manufacturing. Just don't be too sloppy like me.
Now plaster the rest of the chopped glass and epoxy mixture on the joints covering about 1/4" (6mm) of the wood in either direction and then tear off 4 pieces of the wax paper you are mixing on and use them to press down the filler mix into the joints and form a radiused fillet. Make sure to press hard enough to squeeze the material all the way out past the joint laterally so there is enough to sand a square edge later.
Glass fibers chopped and placed in fillet of epoxy resin.
Fillets pressed into joint with waxed paper roughly forms them prior to curing out and sanding.
I chopped the remainder of the glass twice as fine as the first batch, mixed in an equal amount of West System filler and more five-minute epoxy and hardener and immediately peeled the waxed paper, and plastered the filler mix on top of the chopped glass mix and pressed it down into a nice radiused fillet as before with waxed paper left on until cured. This time I allowed the mix to squeeze up about 1/2" (12mm) on either side of the joints and took a little more care to bring it to an nice thin edge. (If you take your time do this well, no filing, grinding or sanding will really be needed until after primer on these finished surfaces.)
Let this cure a little longer than before so it's good and hard before peeling the paper. Now immediately trim the fillets down to flush on the inside and outside of the frames, and square up the joints that might not have fit perfectly in steps 1 and 2.
You can use a sharp knife, a hobby saw or your teeth, but I like the end wheels of the stationary belt sander for trimming and squaring up the canopy joints. With just the right diameter wheel for 1/6 scale and larger scale canopy bows, it takes about 5 seconds with 60-100 grit paper at each side of a joint to get it perfect and ready for fine sanding.
Canopy fillets after peeling the waxed paper.
Canopy frame fillets after trimming to shape on the belt sander.
TRIMMING AND FINAL SANDING THE FRAME
After grinding the fillets, it's a good idea to tape the assembly in the fuse overnight to cure really well.
While taped in place, mark the part with a fine point pencil for final trimming adjustment and then with sanding block, file, or if you're brave, the belt sander, get the bevels (on the front bow especially) to match the compound angles of the glazing. This is the most difficult part of the canopy mounting procedure (along with finding a good cement for glazing-to-wood joints). The angle is about 30 degrees at the top of the curve, and fairs to 0 degrees at the base of the canopy.
Don't sweat it too much though. If not perfect, you can always back-fill the glue joints later with a little filler and cement and clean it up and paint it when you paint the outside frames on the glazing.
1-36 forward canopy bow bevel angle sanded in.
Canopy frame final test fit in fuselage and ready for painting.
1/5 scale SGS 1-36 Sprite composite model from TMRC (now out of production) with canopy glazing in place on the finished frame.
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