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Sep 01, 2019, 01:26 PM
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Make a Balsa Cowl

This balsa cowl was made for a P-51B from plans (Aerofred). I had seen lots of videos on how to make a plastic cowl using liter bottles. Several builders encouraged me to haul off and buy a $25-$40 fiberglass cowl online. What?! However, I wanted a lightweight wood cowl that I could make. It took about 10 hours, but I used materials I already had on hand, so technically it was a savings. And it won't take me nearly as long next time.

Rare Earth Magnets (from Harbor Freight)
1/8" X 1/8" stringers (mine were basswood)
1/8" balsa sheet at least 3" wide
F1 and F2 formers from 1/8" basswood light ply
glue / epoxy -- I used Extreme Power medium CA and Titebond II
You need to have your motor on hand to get the measurements and centering correct -- I used a Great Planes Mount and a Rimfire .46 motor

Context: This balsa cowl will go with a P-51B-D. (A has the guns on top.)

Tips to watch as you go through it.

1. Make F1 and F2 first. Get them glued with balsa between them. My plans called for 3/8", so that meant three 1/8" sheet balsa glued together.
2. Cut out a full-size F3 on the fuse and your front 1/8" balsa should be 1/8" smaller all around than F2. You'll want to sheet/plank the former to blend with the angle on the F2. Cut 1/8" notches about 1" apart all around the formers.
3. Tack glue temporary guides inside the rear and front ends. By tack, I'm talking a tiny drop of CA near the motor hole. Make very sure that (a) the center of the temp guides are centered. This may mean cutting out the rear former, but not totally removing it to use as a guide. When finished, these formers need to be cut up and removed through the rear hole, which is big enough to fit your motor and mounting hardware.
4. Mount your motor to your firewall (F3). Then mount your cowl. It should line up perfectly. I had measured wrong and had to extend my motor on the mount 3/8" of an inch longer. It did fine, but I'm glad I had some wiggle room with the motor mount. Make sure the motor comes through the front hole correctly or you've got some sanding to do.
5. You can use rare earth magnets to hold the cowl to the fuse. I used six placements -- top, bottom, and two spread out on the sides. One version I have seen online bolts the cowl to the front and cut out a cowl hatch and used the batteries. With mine going on an electric motor, there shouldn't be vibration or fuel for which to worry..

This blog was helpful: https://www.rc-airplanes-simplified....E8Nn8OFK_hP6H4
Last edited by UpNup; Sep 01, 2019 at 10:19 PM.
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