RPM (oz7822)

About this Plan

RPM (Ron's Pylon Model). Free flight power model.

Quote: "Put your running shoes on and have fun with this little pylon power model. RPM, by Ron Prentice.

This small power model with a big climb and came into existence last spring. I had been turning out a cupboard and found a box of engines which I had bought from the family of well known American aeromodeller Bob Hawkins. Bob had designed many of the pre-war Cleveland Kits and on his retirement from the USAAF, lived near me in Somerset.

One of these vintage US engines was an OK Cub .024. I had tried to use this motor once before, but it just would not run for more than a second or two. This time I took the tank off to thoroughly cleaned the interior, and found that the jet hole was clogged with the detritus of years. Once this was removed, the engine proved to be a little gem, starting and running perfectly. Having a good small motor at my disposal, I started to think about what model to build for it. I decided that it would be a small pylon model, so out came the drawing board and RPM was born. Why RPM you may ask! When the Editor added the then un-named model to his forward planning list, he wrote RPM meaning Ron's Pylon Model and the name stuck!

The construction is quite straightforward, but in case a beginner should want to make it, here is the way to go about it.

Construction: Starting with the pylon, pin and glue the 3/16 square balsa to the plan to form the basic shape, add the gussets. When dry remove from the plan and glue to the 1/16 sheet sides, using plenty of pins to hold it together. When dry, trim off the surplus sheet but do not round off the edges at this stage. Next make the fuselage, starting with two 1/16 x 1/2 in longerons. Sand the rear end to the pointed shape shown on the plan. Cut the vertical spacers to length and glue between the longerons, pinning the structure to the plan. When dry, remove from the plan and lightly sand each side to make sure the spacers and longerons are flush. Cut out the two 1/16 sheet sides and glue them each side of the framework, again using plenty of pins and making sure that the bottom edge of the sheets are level with the lower longeron. Trim off the surplus balsa and round off the edges with sandpaper. Next cut away the section of top longeron where shown on the plan and glue in the pylon, using plenty of cement. When the glue is dry you can round off the edges of the pylon.

Find some nice light 1/16 balsa for the fin, making sure to cut out the shape with the grain as shown. Make a 1/16 slot in the rear of the upper longeron and glue in the fin. Cut out the front former from 1/8 ply and drill mounting holes to suit your motor. Epoxy four bolts with the heads away from the motor. When they are dry, epoxy the bulkhead on to the front of the fuselage. Cut out two wedges of soft balsa block and cement them behind the front bulkhead as shown. When they are dry, trim them down to shape with a sharp knife and finish off with sandpaper. If you intend to use a motor which is beam mounted, an alternative form of engine mount is shown on the plan.

Make the wing and elevator as shown, making sure to select strong medium/hard wood for the main spars, leading and trailing edges. Partly shape the leading and trailing edges before assembly and make sure to set the dihedral of the wing to the measurements given on the plan. When the wing and elevator are completed and the glue is thoroughly dry, sand them to the final shape, using fine sandpaper fixed to a block of wood.

Select some medium hard 3/32 sheet and make the wing platform, gluing strips of 3/32 square wood along the edges. Drill 1/16 diameter holes front and back of the pylon..."

Direct submission to Outerzone.

Update 25/06/2016: article pages, text & pics added, thanks to DeeBee1.

Supplementary file notes

Article pages, text & pics.

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