Delta 1270 (Delta 363) Notes
Introduction
Many years ago Pete Russell designed his Delta 362 and I had many pleasant hours of flying with this design. It was presented as Plan number RC/1224 in the now defunct magazine Model Aircraft and a 49" version was eventually produced and featured on the cover of the June 1968 Radio Modeller, this model surfaced again in an article in the June 2001 RCM&E and is still available as Plan RM29 Both models are very similar but the extra 10" of the 363 span turns a medium size Delta into a large one. Make sure it will fit into your car ? Due to the age of the original design, some 41 years for the 363 it is a very out of date plan. The radio installation relies on mechanical mixing or a separate servo's for the elevator and ailerons. With modern radio equipment it is possible to dispense with the elevator and use elevons, two servo's with mixing in the transmitter. The rudder is essential for directional control on take off and landing. A steerable nosewheel would be an added luxury but is not essential and as usual vulnerable to damage. For copyright reasons the plan presented here has been redrawn and is not 100% identical to the Delta 363. The new design is called the 1270 and comes out at a 50" or 1270mm. Constructional details are different as is the Fin, Aerofoil Section, Control Surfaces, Undercarriage etc.
Construction
Due to its size and the symmetrical aerofoil it is not an easy model to build. Begin by cutting out the ribs from 1/4 grain 1/16" balsa and carefully slot the leading edges of the ribs. (the slots need to be a perfect fit and dead true to the center line) Make up the leading edges and loose fit to the ribs. Make up a complete trailing edge and once you are 100% happy with the angles and alignment tack the ribs to the T/E with thin superglue and pin down. Fit the top T/E. Re check the alignment and glue the L/E to the Ribs. Cut out the center rib, face one side with thin ply and attach the engine bearers to the ply face at a suitable width for your chosen engine and drilled to suit.. Position the two ply formers the rear one spaced to suit the chosen fuel tank and drill for the pipes & throttle cable etc. Drill for the nose leg and fit. (this is hard to do later once the u/s sheeting is in place, note the length to suit a 12" prop) Attach the two ply formers with Araldite. Now fit the center rib. With extreme care slot the ribs for the 1/4" x 1/4" & 1/8" x 3/8" spars and fit. These can be tapered out to R7 if required. Once this part of the build is completed you should have a fairly rigid large delta. Fit the 1/16" sheet leading edges, front capping strip & the 1/16" x 3/8" rib cap strips. Slot in the main U/C assy. and reinforce with plenty of ply gussets. The bearer should fit flush with the lower sheeting. Sheet the underside two bays wide. The rest is more or less straightforward. Not a model for a beginner but then beginners do not fly fast Delta's or do they. If you are considering building more than one, a simple assy. jig may be a possibility. This will ensure a perfectly flat build with all angles correct.
Flying
Delta's are very challenging to fly, they are very fast but can be flown slowly & are hard to stall. However they are very difficult to fly once they get going as orientation is a problem. Unless you keep your eye on the ball you can forget which way up they are. A very colorful covering helps. Also allow plenty of UP on your first flights and use your rate switches. I have now completed my model, see photo's below and it flew straight off the board. Center of Gravity. Always difficult with a Delta. Mine flies well with the C of G 21" FORWARD of the Trailing Edge. Whatever you do it MUST be forward of the rear wheels. Make sure it sits in a slightly Nose Up attitude on a level surface. Good luck.
Problems
The only serious problem I had was with the Elevons. With the original design these were far too flexible as they are quite long. They need to be made from very hard balsa, reinforced at the horn locations and a couple more places. They need to be at least 1/4" thick at the hinge line. Also a long take off was required as my first model sat slightly nose down & C of G too far forward.
Due to the large amount of data these files take a couple of minutes to download.
Download Sheet 1 Delta 1270.pdf
Download Sheet 2 Delta 1270.pdf
Text © Colin Usher 2011 Illustrations © Colin Usher 2011
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