You can buy, at office supply places, full-sheet transparent label material.

I used this to make the markings for my Estes Titan II. The original didn't have decals; I scanned in the pattern, and used Corel Draw to recreate the roll bars and stripes and such, on a different layer, and used that for printing.

Print nice and dark and maybe darken with ink marker after the fact.

You still need to cut out the pieces carefully.

I hit the Titan with matte spray and that concealed the transition between paint and label and it really came out nice.

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NAR #27085 - Oregon Rocketry - SAM