Swan (oz14011)

About this Plan

Swan. Free flight boost glider model.

Quote: "Rocket Trails, with G Harry Stine. Globe-trotting Engineer Perfects Unique Rear-engined Boost/Glider. Pinky's Swan.

From time to time in these pages, I have mentioned AW 'Pinky' Guill who is probably one of the finest senior model rocketeers in the nation. Pinky is known for his beautiful scale models and his free-wheeling approach to boost-gliders. An old aeromodeler, Pinky somehow finds time to build model rockets between trips abroad as a senior engineer for Union Carbide International. He also serves as a Trustee of the National Association of Rocketry and as senior advisor of NAR's Fairchester Section in Connecticut.

For three years, Pinky has been working on rear-engined variable-geometry canard boost-gliders. His basic system uses a forward stab that swings sideways out of the fuselage when activated by the ejection charge. His early designs ejected their engines completely and his configurations used delta planform main wings. Some of Pinky's early birds are shown on page 174 of 'The Handbook of Model Rocketry.'

In order to comply completely with the NAR contest rules that prohibit the ejection of a spent engine casing without some means to decelerate its fall, Pinky decided to retain the engine casing within his bird. Of course, this increases the glide weight by 0.42 ounces due to the weight of the engine casing. To compensate for this, Pinky had to go to a configuration with higher lift-to-drag ratio, so he selected a nonswept elliptical planform main wing. The test flights with his new design indicated some serious panel flutter, so he added external stiffening ribs that serve double-duty as flow fences, not that he needed them on an unswept high aspect ratio wing.

The result was 'The Swan,' an unusual B/G design that caused considerable comment at NARAM-7 where it took third place in Senior Division Swift Boost-glider Duration.

Construction is straightforward with the exception of the canard release mechanism which must be preassembled before inserting it into the body tube. Two balsa plugs - commercial engine bulkheads will do - are assembled on a 5-inch length of 1/8-inch hardwood dowel. A piece of 1/32-inch music wire is bent as shown. Note: Assemble the bulkheads to the dowel and insert the tripwire in the following order. Bend the forward loop in the tripwire. Insert both unbent ends of the tripwire through holes in the bulkheads and slide the bulkheads onto the dowel, pushing them toward the center of the dowel. Bend the ends of the tripwire as shown. Then slide the bulkheads to each end of the dowel, making sure the ends of the tripwire are positioned through holes in the bulkhead as shown. Glue the bulkheads to the dowel. Assemble the elastic thread as shown. The assembly is now ready to be inserted into the body tube.

The operation of the canard release mechanism is as follows. A loaded engine is inserted into the aft end of the body tube and left against the engine stop wire in its rearmost position. The canards are swung back into their powered-flight position, The engine is then slid forward against the rear bulkhead. This pushes the tripwire forward into the notch in the tip of the canard, holding the canard folded into the body.

The ship is launched in a standard manner. When the ejection charge goes off, the engine moves 3/4-inch to the rear, the ejection gases being vented through fuselage holes as shown. The rearward movement of the engine allows the tripwire to move aft under tension of the elastic thread. This releases the canard surface so that it can swing out.

Without the canard surface extended, the bird has a very steep pitching moment curve and trims at zero angle of attack. It is ballistic. It will fly straight up and, if the canard stays folded, it will dive right back to the deck. When the canard deploys, its airfoil produces a positive pitching moment, and the bird trims out with a positive angle of attack on the wings.

Glide trim is rather tricky. I've watched Pinky fly the Swan to trim it. If it gets the slightest bit tail-heavy, it does not stall, but simply mushes down to the ground. Pinky has flown the bird several times in 10-mph winds with a 1/2A.8-2 engine, and it performs well under these conditions. He does not recommend using a Type B engine, as the wings have a tendency to come off with this much boost. This probably would not be the case if 1/4-inch sheet were used for the wings.

The Swan is fun to fly. It gets up there nice and slow and straight. There is a puff when the ejection charge goes off and the canards snap out. There is no falling engine, of course. The bird just hangs there.

This is not an easy B/G to build, but has undergone enough development to be reliable. Compare it with my 'Unicorn' in new AM Annual."

Direct submission to Outerzone.

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