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Here is another technique for making ribs. Mold them. Get a block of basswood that is at least 2" wide x 4" tall x 6" long. Lay the block on its side (4" side down) and draw a curve using a French Curve drawing template along its length, Bandsaw the block along that line. You now have two halves of a RIB SHEET MOLDING FIXTURE (RSMF).illusionist wrote:does anyone have an idea as to where i can get curved wing ribs to create the aerofoil?
Use either 1/20" or 1/16" balsa sheet. Cut 3 sheets to fit the width and length of the RSMF. Now, soak or slow cook the sheets (simmer) in water for about half an hour. Pull the sheets out, blot the excess water off and layer onto the bottom half of the RSMB. Press down the top half of the RSMF and clamp everything together- tight.
If you use a metal clamp, you can heat the assembly in a slow oven (200 degress) for an hour. If not, let dry for two days. When dry, unclamp the RSMF and remove the top half. Then carefully remove the 3 sheets of balsa. If really dry, they will remain curved. In fact, if you press them flat and then release them, they bounce back into their new curved state. The top and bottom sheets are the sacrificial sheets. Its the middle sheet that is important.
From here on its easy. 1) Cut a straight line to true the LEADING EDGE. 2) Mark that leading edge with a colored Sharpie marker. 3) Slice the ribs by pushing the sheet flat and cutting the length along a straightedge.
An Master Airscrew Balsa Stripper is a great tool for this step!
All the ribs will pop back to their curved shape and actually be tougher as their grain runs parallel to the camber of each rib. When you use them in building, try to trim them by only by cutting from the back edge which allows the curve/camber to be consistent throughout the wing or stabilizer. You can vary the camber of a rib sheet by choosing different places to make that primary, leading edge cut before slicing the ribs.
Arthur C. Clarke
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