Un-Polly (oz15145)

About this Plan

Un-Polly. Outdoor HLG. Wingspan 18 in.

Quote: "THIS MONTH'S THREE-VIEW: THE UN-POLLY HLG: With all this talk of VIT, laminar flow, circle tow, Schneurle porting, thermistors, etc, how about a break for something simple? Like a simple hand-launch glider, as in this month's 3-view. Not much to it: V-dihedral wing, no DT or fancy finish, and you can get 2 wings, 2 fuselages, and 6 stabs from a 36-inch length of balsa. Looks like you could build it in less time than it takes to put in a DT on a regular HLG! And that's the idea, to have a simple, expendable HLG that I could make fly.

This last part was critical, since I've had trouble in the past in building HL gliders that were straight and well-aligned. It looked like my chances of getting a straight glider would be enhanced by using V-dihedral in the wings, since I'd have 1/3 the joints to make. Most of my indoor gliders have had V-dihedral, and nearly all had flown well. The few outdoor V-dihedral gliders I'd built had usually been quickly lost, so maybe I was on the right track.

I based the rest of the design on Bill Blanchard's Polly, using the same fuselage and tail surfaces. I used a fully parabolic planform to cut down the wing area, give a slightly higher aspect ratio, and give a better spanwise weight distribution by allowing more tapering of the wing blank before carving the airfoil. This should cut down on the model weight, so I cut down the fuse-lage stock slightly and decided to leave off the DT until I started losing gliders.

The stab was made of 1/20 stock to speed up construction and aid incidence alignment, since I didn't sand in an airfoil, just rounded the edges and tapered the tips after assembly. If 1/20 sheet is not available, pick out some of the thicker 1/32 stock from your dealer's shelves or your wood box.

I finished my Un-Pollys with a couple of coats of lacquer sanding sealer (Glidden's is a good one) and a thin coat of nitrate dope. I built one version with a 3/16-inch balsa wing and another with a 1/4-inch sheet wing. The 1/4-inch thick wing came out about 30 grams; the 3/16 model was a bit lighter. Both ships per-formed about the same and trimmed out easily. I lost one while maxing out at the Hawks' Spring Opener this year, but it took less time to build the model than to rig a DT.

I found that the V-dihedral model lent itself very well to an unusual HLG trimming scheme. I left the glide a bit stally, but with a definite glide circle, by removing clay after initial glide testing. When the model hits lift, it stalls, then slides off the wingtip into the glide circle, keeping itself centered into the thermal at all times. This is an excellent trim for breezy afternoon conditions, since the glider will drift downwind in the thermal, rather than gliding through or out of lift. This bobbing and weaving 'bounce' (hate to call it a glide) is not pretty, but it gets the time on the card. A more normal trim can be used in calmer, light-lift conditions."

Direct submission to Outerzone.

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