Wednesday, March 26, 2008

DLG Plan: Part 4, Wing breaks and fuselage

Photo left is just a reminder of where I had reached at the end of Part 3 in this build. The wing high point is just visible as a dotted line and both wing and fin have denser wood LE reinforcement.

After cutting at the breaks and sanding, the photo right shows what the aerofoil looked like.
The walnut LE shows up nicely. The TE is thicker than I would normally finish a HLG. However, I'm nervous about strength and kept the TE at just over 1mm thick to provide some surface area for the glue and to preserve some rigidity in the wing. Quite close to AG03.

Photo left is the wing drying. Glue is Araldite Precision slow setting epoxy. It's all standard HLG building so far. 109 mm under each tip (the convenient height of a tomato tin!) .

While the wing was setting, I glassed up some 1/32" (0.8mm) marine ply using medium glass cloth and two part epoxy. This will make the wing break reinforcing braces - it's cunningly sized to fit exactly within a tenon saw cut. I may also use it for the boom hinge plates (or 1/64 ply - haven't decided yet). Poly bag below and above, then weighted down with books overnight while it set. This is the first non-standard HLG bit.

A closeup of what the glassed ply looked like when dry. Probably too much resin this time. However, job done and it's much stronger and not significantly heavier than without the glass fibre.

Also while the wing was setting, I cut out the fuselage parts. Very simple: 6mm square spruce, a carefully selected coffee stirrer (thanks Starbucks!), and 1/4" (6mm) balsa 18mm wide. Glue these together with PVA and rubber bands, with the spruce butting against the coffee stirrer.

Then apply 1/32" (0.8mm) ply cheeks to reinforce the central part. This was standard marine ply, not the glassed stuff. Again, glue with PVA. The ply cheeks also act as the locator for the carbon fibre boom.

After cleaning up the glassed ply, and sawing the wing along the high point line from the underside with a tenon saw, test fit the glassed ply wing break reinforcer. Mark with a pen above and below the wing and trim.

Cut off the excess and lightly sand up the glassed ply brace. This is what it looks like - a sort of chevron. When happy, I glued it in place with Araldite Precision .

This is what the underside looks like after the glassed ply brace has been glued into the saw cut.

I hope it's strong. So far, this is easy and relaxing building. But will it fly, or is it destined to crash into the ground with a sickening crunch?....

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