Ingenious Balsa Stripper
Mark Drela
This is an inexpensive, easy-to-make, and very accurate beam balsa stripper. Since it handles sheets up to 3/32 in. thick, it is designed with small models in mind, such as flying scale (especially Peanut), P-30, Embryo, Pennyplane, etc. Although I have used it to build very light indoor models, you might consider a very sophisticated and accurate micrometer beam stripper if you want to build stuff like indoor microfliers. (Micrometer strippers are available for $41.00 from Ray Harlan, 15 Happy Hollow Rd., Wayland, MA 01778.) For anything less exotic, however, this stripper is ideal.
The price of the whole thing should not exceed four dollars. The most expensive part will be the aluminum beam, which can be found in any good hardware store. Be sure to get one without nicks or scratches. The construction of the device is simple and self-explanatory. The entire stripper can be built in a matter of hours.
Using the Stripper
To use this tool:
- Securely tape a piece of balsa sheet to the board.
- Turn the screws so that the beam is near the edge of the sheet and make a truing cut.
- Keep the beam pressed against the screws and the blade flat against the edge of the beam when cutting.
- To cut a strip, back off the screws the necessary distance and cut again.
- Repeat the last step for another strip.
- Several light passes produce better results than a heavy cut; the edge of the strip is less likely to be wobbly.
The marking dots on the discs are intended to help keep track of the number of turns backed off. Be sure they are aligned in the beginning. If you lose count while backing off one screw, referencing the dot on the other screw will enable you to set things straight again.
Tapers, Ribs, and Fine Work
Undoubtedly, the biggest advantage of a beam-type stripper is that tapered strips can be cut just as easily and accurately as untapered strips. I have even cut indoor FAI prop spars with it with good results, although the cutting stroke had to be extensively practiced before such a critical operation was successful. Mark the beam off into fourths, fifths, and sixths to help figure out the screw settings for any given taper.
Another ideal application for this tool is rapid cutting of perfectly matched sliced ribs. Simply butt the bottom edge of the rib template against the beam and away you go. You can even accurately vary the thickness of the ribs as you go from root to tip. In any case, make sure the aluminum beam is parallel to the board at all times. Shim the rear edge of the beam when stripping sheets less than 1/8 in. wide.
Finally, as with any other balsa stripper, you can save considerable money by cutting your own strips from sheet stock. If you do a lot of building, for instance, this stripper will easily pay for itself in less than a year.
Transcribed from original scans by AI. Minor OCR errors may remain.
