Pisces (oz11814)

About this Plan

Pisces. Radio control flying wing model, for electric or diesel power.

Quote: "This fantastically versatile flying wing - usable as a powered glider, a 7-1/2 PG glider or a six cell-540 power electric soarer - is for two function radio. Pisces Flying Wing, by Frank Wilde.

Designed and built in March, Pisces was the astrologically obvious name for this aircraft. Its reason for being was that a friend, Mike Reynolds, happened to see a photo of an all-wing electric job from the Detroit area in an American magazine which was said to be capable of 80 mph using a similar power unit to his (Leisure motor and six cells). He prevailed on me to design something similar, specifying a Dactyl (oz1567) outline, (the Dactyl is an old free-flight wing from way back in '49) with a wing structure similar to Pete Holland's Flapdoodle, a design that he had been flying for some time. Well now, I don't think we hit the 80 mph mark, except perhaps in a dive, but we were certainly impressed by its all round performance.

A second model was built, this time by Paul Channon, using a Ripmax Le Mans 480T motor. Both prototypes were capable of flights around 15 min, Raul also recorded 22 min and 44 min, and later took third place in a 1 kg contest at Oxford. It was soon evident we had a problem - every once in a while, particularly if there was lift around that took Pisces up and away both jobs would try to 'tuck under' which in Mike's case unfortunately resulted in two write-offs, l eventually came to the conclusion that there was some interference between the long servo leads and the aerial. The mini servos were wing mounted so there was a grand total of 46 in of 'live' flex, in view of which standard servos mounted in the wing root are indicated on the plan.

It is significant that a dieseil-powered version has no such problems, this being produced by myself because the surprise to me was its soaring capabilities, especially in view of that wing section which was 'bashed' up with the aid of a piece of 1/8 in sq spruce and some pins! The wing structure is really only suitable for a symmetrical section. Covered with Solartex it is both light and rigid.

Construction: All the leading edge ribs may be made in one sandwich block, these to be numbered 1, 1A, 2, 2A, etc, all the As being kept for one side (just an honest endeavour to be exact). Make up the main spar. Mark the rib position on the bottom leading edge sheet and glue the main spar in place, web to the rear. Pin down the trailing edge and fit the root rib. This requires the temporary removal of a slice indicated by the dotted line to enable it to rest flat on the board. Rib 14 is then glued to the main spar. The sheet is then lifted and glued to the root and tip ribs, a length of 1 in trailing edge stock being used for packing. This requires careful adjustment to get the tip rib at the right angle. The remaining ribs are now glued and pinned in position, followed by the first 1/8 in leading edge strip, surplus lower sheet being trimmed off to this.

The top sheet may now be fitted. Rib 14 requires to be double to carry the tip sheet and the No 1 rib glued to the root rib to carry the top sheet of the centre section. Fit the 1/8 carved part at the tip followed by the top the bottom sheets indicated. A slot requires to be cut through the root rib between the spars and part A inserted and glued in place to strengthen the centre section.

The wing flaps are joined inverted flat on the board, so the only dihedral is by virtue of the taper, the joint to be reinforced by glass fibre or a couple of perforated alloy plates epoxied in place. Former No 4, complete with locating dowels should be fitted with the wing in place on the fuselage to ensure correct alignment. The motor micro switch is mounted on a piece of 1/8 sheet faced with 1 mm ply - be sure the toggle is in line with the push rod. The radio gear is packed into the wing and secured with tape.

The front of the wing is held down by a flat brass swivel clip. Be sure there is no slop in the cranks, in the absence of a suitable drill these may be drilled with a piece of 20 gauge wire. A 6 x 4 prop was used on the original. A 7 x 5 cut down to 6 in diameter gives more speed but slightly less power run.

Flying: Initial tests are best made under power as flying speed is fairly high. Do check that the elevon angles are correct. Roll rate is a bit slow due to reduced travel with a transmit-ter mixer but perfectly axial thanks to the correct side areas I have always advocated sweep back for stability, as the C P is spread over an area rather than one point, spanwise drift will be minimal with the sec tion employed also being offset by the lack of dihedral Pusher power unit means clear airflow over the centre section, a flat sided fuselage together with the fins provides good directionl stability, providing what t would call 'tricycle' stability. External ele-vons are easier to install than the built in type with the attendant hinge problems. Being further back the elevon is in 'cleaner' air. It seems to me that one of its chief vir-tues is penetration --- it tends to 'bounce' rather than slow up when encountering lift.

The, model was not designed specifically for the 1 kg class - it just happened to comply. A bit slower than say good opposition, but quite equal durationwise. Maybe it would be a bit faster with tissue and Solarfilm covering rather than Solartex."

Pisces, R/C Model World, July 1985.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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