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Dec 10, 2018, 04:19 PM
Entropy is happening!
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Laser method notes.

The advantages of this method are:
1. Light and strong.
2. Ease of construction.
3. Quick and cheap. Foam for the ribs can often be found from recyclers.
4. Accuracy. All ribs cut together in the one set up. Cannot get them better aligned than that.

For my next constant chord wing using this method, I plan to construct the spar first. It will go something like this:

1. A foam core tapered in thickness will be hot wire cut. Dimensions will be the airfoil thickness minus the carbon caps, minus 1 mm for sanding/fairing balsa. Lets say, nominally 35 mm high and 8mm tapering to 4mm thick, (for example sake only).
2. This core will be faced in 1 mm Pauwlonia ( but could be balsa or basswood et. al.) with vertical grain orientation.
3. End grain of the timber is then sanded down to the foam.
4. Pre-made carbon spar caps are then added to the top and bottom of the assembly. These will be layed up using common uni-carbon/laminating epoxy which is cheap.
The thickness of these caps are tapered out to the tips.
5. The caps are glued on and the assembly wrapped with Dyneema, Kevlar, or other similar high strength braided line. Then all given a light application of thinned epoxy resin.
6. The "laser method" hot wire cut ribs are cut with a slot to take the spar. The building board might be in two parts, to enable separation of the two halves to allow the spar to be lowered into place, glue applied, then the two halves brought together.
7. The joiner boxes will be glued into the main spar and the assembly wrapped again.

I fully expect this assembly to be super light and super strong.

Video of a top cut:
(1 min 35 sec)
Last edited by Jim.Thompson; Dec 25, 2018 at 07:21 PM.
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