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Saturday, July 6, 2013

Sirius Interrogator Build Part 6, PRM Fin Covering

At one time, PRM covering was sold through the Estes catalog.
PRM stands for Paper Reinforcement Material.
It's a white self-adhesive paper, great for reinforcement of thinner balsa.
It's also used when you don't feel like filling the balsa grain.

This kit also gives you the option of cutting out fins in the traditional way -  cut out and fill the balsa grain. A separate card stock fin pattern is supplied.
These days, 1/16" thick fins seem too thin and weak. The PRM paper lamination makes the thin balsa very strong.


I did lightly sand the flat balsa sheet with 400 grit on a block. This removed any "fuzzies" and should give a smoother surface for better adhesion.
The backing is peeled off and the entire printed sheet is applied to the balsa. Burnish and smooth out the RM.

A second piece of un-printed PRM is applied to the back.

Use a new blade, you'll want a clean cut through all three layers.

TIP: Set your straight edge over the fin surface and keep all your cuts to the outside of the fin. This way your blade has no chance of slipping in and cutting the fin surface.

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