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Forgot to ask a question: What keeps the rubber band from slipping off the narrow edge of the "displacers"? In helirocs half a launch lug mounted to the tip of the rotor dihedral stop serves to hold the rubber band in place. I couldn't see what serves that function in your pics.
First, all my “displacers” and/or rotor stops are bilaminar or trilaminar. If bilaminar usually two pieces 1/8” balsa, with grain directions 90 degrees opposed, best is DIAGONAL (45 degrees) of axis of rocket. Once glued/laminated these are strong on any stress axis.
If trilaminar, the outside pieces have grain perpendicular to long axis of rocket, inside piece grain parallel.
If bilaminar, before you glue, put bevels on each outside margin. When you glue them, bevels face each other to make a v shaped trough. Drizzle thin CA after laminating for strength. Reason for 45 degree angle is so neither piece is parallel to the band (would break off really easily.)
Currently most of mine are trilaminar 1/16”. The middle piece is cut a shorter on width axis, so when glued together there is again a “trough” or canal that holds the band or string. Outside pieces are perpendicular to the band for strength purposes.
You can laminate/glue these with either wood glue or thick Ca. If wood glue, you need to stick them between wax paper and put them in a book or something to keep them flat and together, otherwise they warp. With thick CA you can just stick them in a clothes pin.
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