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Old Nov 10, 2012, 09:12 PM
AndyKunz is offline
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The thread title says 40" but with the wing tips I just finished, it's actually 44". The DX18 is one of the first protos. The length from back of spinner to end of fuselage is 27.5" but the elevators will extend a little further back.

OK, wingtips.

The tips are made by sandwiching some balsa. The center core is a piece of 1/4" balsa (cut to rough shape) with the grain running chordwise. This is because the wood extends behind the wing to end with the aileron TE, and this makes it a little stronger. The top and bottom pieces are 3/16" with the grain running spanwise. This is easier to sand to the airfoil. This sandwich is clamped between two solid blocks and clamped overnight.

I didn't show it, but you can do a good bit of ligthening of the wingtip by removing wood from the 1/4" section before gluing the sandwich together.

The root side is then sanded square then glued to the wing tip. Note how the inner layer can be lined up to serve as a reference later when sanding. The glue again is given plenty of time to cure.

After the glue dries you can do a little carving and then sanding. I use blue masking tape at the root to keep from sanding the whole wing skin down to nothing The paper is coarse and attached to a real long sanding bar. This ensures a good airfoil shape matching the wing cleanly.

Next the tips are rounded with a smaller block not as coarse, then lighter grit, and finally with the flexible sander.

As you sand the airfoil to shape you will notice that the layers provide a good reference to how evenly you sanded.

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Last edited by AndyKunz; Nov 10, 2012 at 09:19 PM.
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