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Wednesday, July 28, 2010

FREE MODEL GLIDER PLAN: DOGEAR 6" Tiny glider

This is DOGEAR, a development of DOGCHEW (see previous blog post, again, just click and save the plan). DOGEAR differs mainly in the wing design. The planform is elliptical at the front with a basswood leading edge (or use lime wood which is also genus Tilia). Trailing edge is mostly straight with single taper near the tips. The wing is also thicker, 2.5mm (~5%) compared with the 1.6mm of DOGCHEW. By feel, I carefully sand a small "Phillips entry" under the LE, but the rest of the underside is flat. It is a typical HLG aerofoil. The wing is assembled as a straightforward three panel structure using epoxy at the breaks - the tips are raised by 15mm from the flat centre.

The three panel wing and the fact that dogs appear to find my models "tasty" were the reasons for the name DOGEAR.

Fuselage is laminated using pva (e.g. Titebond II). The thin glue layer increases stiffness and strength a great deal. A lighter way is to use spots of cyano. Alternatively, forget about the laminating completely and use hard 1/8 balsa instead. Please do feel free to experiment with nose length. In other words, cut it shorter if you wish. The size shown on the plan seemed work well in calmish conditions. I use epoxy for the wing fuselage joint and throw tab. Fin and stab should be sanded as thin as you dare, so that you can breathe and bend for trim.

My finish is the traditional 2 coats of thinned down sanding sealer with very fine Al-ox paper between coats. I finish the wing with sanding sealer before it is cut into three panels and the stab and fin before they are glued to the fuselage. A splash of dayglow colouring helps enormously for visibility. Apply Al-ox paper grips on the fuselage sides. In the photo below, you can see some inked stripes that also help to see the plane against the sky (er, I mean clouds, cos that's wot we av ere most in England).
By my reckoning, DOGEAR will stay up for about 5s longer than DOGCHEW in "still" air; by that I mean in very calm conditions outdoors early morning or late evening. I recorded consistent times of ~22-24s for DOGEAR in such conditions (I am sure a lighter version would do better).

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