Kevin Wickart's Tech Tips #2

Quick and Easy Airfoils

The tools you will need are:

Masking tape and some abrasive substance. If my personality isn't handy, try my secret weapon...Go to Walgreen's, where just inside the entrance you will find the cosmetics accessories department. In the Nail Care section you will find a display of Kiss brand nail shaping sticks. These are the most wonderful things you can imagine. The most useful one (IMHO) is about 1" x 7" x .125" and has a 100 grit surface on one side and a 180 grit surface on the other. Both sides are open-coat so they don't clog very easily. If you're wearing denim slacks when you sand, you can just wipe the stick on your pants leg to clean it. These things make sanding airfoils even easier, and they cost all of $1.59 each.

INSTRUCTIONS:

1. Cut the wing out as a single piece.

2. Draw the centerline and any polyhedral cut lines on the *bottom* of the wing.

3. Draw the airfoil high point line on the top of the wing.

4. Apply a strip of masking tape along the trailing edge side of the high point line. This will help keep you from over-sanding the high point. Sand a flat surface from the tape down to the bottom of the leading edge, BUT...leave a "lip" of about 1/3 the total wing thickness so you can properly round the front of the airfoil.

5. Remove the tape and apply another strip along the leading edge side of the high point line so you can sand the trailing edge of the airfoil. Sand a flat surface from the tape to the bottom of the trailing edge. There is no need to leave a lip, BUT...either switch to finer grit sandpaper, change the pressure of your sanding, or reinforce the trailing edge with a strip of masking tape stuck to the underside of the wing--otherwise you'll make hamburger out of the balsa.

6. Remove the tape and look at the wing's cross-section. It should look like a very flat scalene triangle (except for the leading edge lip). Adjust as necessary.

7. BEFORE YOU DO ANYTHING ELSE...soak the knife-edge airfoil on the trailing edge of the wing with thin CA. If you don't, bad things will happen to it and you'll have to start all over. Keep the de-bonder handy.

8. Round off the lip on the leading edge of the wing, and round off the "corner" you created on the high point line. Now look at the wing cross-section again, and you'll see a beautiful airfoil.

Wasn't that easy?

--Kevin--