On a rainy Independence Day holiday, I spent some time cutting the leading edge shells on the CNC machine. First I cut a piece of cardboard the size of the stock (6 x 1 inch) and then traced the airfoil profile onto it. This was laid onto the ground and a photo taken from directly above. The image was imported into CAD, sized, and a spline used to trace the airfoil curvature. After extruding, some other features were added to the ends to fit the ribs and make reliefs for the rib angle brackets. That solid file was imported into CAM and I set up a cut sequence, primarily chordwise, with some extra attention around the edges.
Cutting the first part out of some scrap identified some minor changes to the part. After making the adjustments and a quick trip to Home Depot for more foam, I set up the machine for running back-to-back parts. The 20 minute time between parts then became a rhythm of hearing my watch beep, going to the garage to service the machine and index to the next part, hit run, reset the timer, and walk away.
I taped a few of the pieces to the wing leading edge between ribs. It fits really nicely and supports the ribs as well. I'm thinking of glassing the back of the foam shell pieces and then also glassing the front once the pieces are all bonded to the wing. That should provide some extra ding-resistance and robustness.
Another minor change, I finally tried adding a variac to limit the voltage input to my router (poor-man's spindle). Previously, it ran full 1.75 HP continuously and was rather loud at 30,000+ rpm. Now I'm running about 50% voltage, which still appears to cut foam quite nicely at the lower RPM, and quiets down the router below the noise level of the shop-vac dust-collection system. Didn't even have to turn up the TV in the living room, which shares a common wall with the garage.
Happy Independence Day!
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