Friday, April 11, 2008

DLG Plan: Part 6, Finishing the glider

This photo of the finished glider - LIPZOID - was taken just before its maiden flight. See the video in Part 5 below.

Parts for the left side of the fuselage. From the left: 1/16" ply, 3/32 balsa (the hole is for the DT viscous button timer - I modify the basic cheepo buttons available from Flitehook for £1.50) and 1/16" balsa. Edges were sanded so that the surfaces blend together smoothly.

After the front of the fuse is finished, I cut out the wood boom block (pine) and measure out and cut the rear of the fuse.

I ca'd a bit of thin clear plastic to reinforce the rear of the fuselage, as this will come into contact with the spruce block when the boom is up. This was then trimmed and cleaned up.

This is the pine boom block ready for gluing with ca. Then it was glassed with the cloth running round the 5mm carbon fibre tube.

Ready for drilling. It was quick and easy to drill the pine boom block first. Glued one 1/16" ply cheek and when dry, marked and drilled it. Then did the same for the other ply cheek.

Wing being glued to fuselage. I simply sanded the top of the fuselage flat to mate with the wing underside. However, because of the upsweep under the LE, I also made a small wedge shaped balsa piece to match the space between LE and fuselage.

This is a close up of the wedge under the LE.

Close up of the finished boom block socket.

Glass cloth was applied to wing joints - two 2" squares, one over the LE and the other over the TE, plus a strip top and bottom. Lightly tacked with a spray glue, ready for resin to be sparingly brushed on. In addition, the left wing was given extra reinforcement in the form of oval patches in the middle of the joint on both surfaces (not shown in this picture). The centre wing-fuselage joint was also reinforced in a similar manner.

Detail of rear of fuselage. The gf cloth reinforcement is visible as is the nylon hing bolt. I used two transparent hair bands around the boom (Lark's Head knot) looped over a bamboo peg in the middle of the wing. The yellow band is thinner pole elastic for the timer.

Detail of the boom arrangement. Pink band is 1.6mm pole elastic, tied (Surgeon's knot) to the thinner yellow elastic. The yellow is tied to nylon fishing line with a small loop tied to the end. The loop is hooked over the timer arm. Coaxing it to operate reliably (one turn of the arm should take about 1 minute) is good fun and surprisingly easy. Under the wing the pink elastic is tied to a steel pin head and run round two cocktail stick pegs. Also, you can just see the adjusting screw for decalage.

Glider with boom in the up position. Just numbers (BMFA and mobile) to apply. The finished model without ballast was 83 g, a bit heavier than I would have liked. I definitely overdid the glassing, especially on the tail. On the other hand, it's pretty strong and I reckon it will need to be because it's going to get a good bashing!

I enjoyed this design and build process. It is always amazing to see one's model fly. LIPZOID seems to be fairly stable with hardly any trimming effort so far. My tip launching was not very consistent, but thankfully, the model recovered from most of the scary attitudes. There was one very heavy landing, but just a minimal repair to the right wing was needed (I knew that was going to happen because there was a natural softer spot in the wood there). I'm now waiting for good weather to have a decent trimming session. I'd like to try increasing the decalage and perhaps moving the CoG more forward. It's at 50% at the moment.

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