Wakefield Rubber-Powered Model F1B

We haven’t held a regional competition in the VM–GM (F1B, F1C) categories for 7 years—which is a shame for these interesting categories. We hope that some model aircraft enthusiasts will decide to build such a model.

Building a rubber-powered model requires a great deal of skill and perseverance. This also applies later on during the flight-testing phase. I therefore recommend this category only to experienced model builders. Furthermore, as you can see from the plans shown, there are many mechanical parts that need to be fabricated. If you can’t turn parts yourself, you might know a precision machinist. The fuselage tube (Ø30 x 0.3) can be obtained from Dieter Siebenmann while supplies last and is world-renowned.

For the wing assembly, we use a 2-cm-thick blockboard as the base. The wing is constructed in four parts. We then glue 6-mm-thick, soft balsa wood onto the blockboard, cutting it to the size of the respective wing shape. A profiled negative mold is screwed onto both end faces. Using a long sanding block measuring approximately 1.5/6 x 60 cm, we can now shape out the entire negative mold. Now we begin to assemble the airframe. The lower balsa board is sanded according to the plan, and we glue the front and tail spars onto it. The entire assembly is glued to the negative mold using small drops of glue, positioned so that we can easily remove the glue drops later with a razor blade. Next, use a curved ruler to cut the undersides of the ribs and glue them onto the wing form. Once all the ribs are in place, screw a second set of profiles to the front end of the upper wing surface. Using the long sanding block, you can now carefully shape out the top surface. To attach the upper skin, we use contact adhesive, position the small board at the front spar, and spread the adhesive evenly toward the rear.

The elevator and ailerons are also constructed in the same way.

For the fuselage cone, we need a mandrel as a form. A pre-cut balsa strip (0.8 mm) is wet-wrapped around the mandrel using gauze bandages. Glue the ends together butt-jointed only after it has dried. For the aileron shaft and the elevator mounts, reinforcement rings made of balsa wood must be glued in place. To cap the cone, glue the aluminum part in place using Araldit, following the drawing. Important: Be sure to thread all the wires beforehand for the ailerons, differential control, and thermal safety device.

A Seeling (Germany) 3-function timer is installed in the pylon (wing mounting). The wing mounting consists of steel wire (1.5 mm) — with the corresponding MS tubes (preferably aluminum-reinforced) at the wing center sections. Aluminum parts should be anodized; this makes them more durable and provides additional reinforcement, especially for the fuselage. All shell parts are coated twice with two-component clear coat. Use the thinnest possible consistency (available from J. Maeder, Zurich).

The next issue will cover the construction of the propeller blades and test flights. W. Heise