Scienceguyorg Ramblings: Viscous DT on Blue Ridge Special Rubber Model

Monday, April 16, 2018

Viscous DT on Blue Ridge Special Rubber Model

For a long time I have had this idea about installing a viscous DT (dethermalizer) system on a sport rubber powered free flight model. My first experiment installing a DT system was to install a fuse on a Guillow’s Lancer. This worked well and gave me experience handling a fuse but I wanted to try a viscous system because I wanted a system kids could use without playing with fire. Presently I am writing a couple of articles on viscous DT systems so this would be a good time to try a system on a smaller airplane.

Previously I had built a Blue Ridge Special from plans but lost it this winter on a frozen lake, I had the Volare two plane short kit so decided to build one and install a tiny rotary damper system using the E2 style rotary damper, the price is under $3. To keep the weight of the airplane as light as possible I used really light wood, which the instructions caution against. The leading edge started to bow in but I warped it straight, the problem came back when I covered the plane with Esaki tissue. All the covering was ripped off and laminated a piece of 1/16” square to the leading edge. Recovering went better except now the trailing edge was too soft. When I build the second model I think a light plastic will be used.

To make a timer I referred to Manuel Cisneros article; you remove a plastic gear, slip a tube over the shaft, and place a pin through the shaft. My particular rotary damper appeared to take more force to turn it so I slipped another plastic tube over the first tube to increase the torque. On this same model rotary damper on a glider it turned fine without the extra tube. The rotary damper was mounted on top of the fuselage because I was afraid it might interfere with the rubber motor if mounted on the side. Instead of popping up the rear of the stabilizer I decided to pop up the front of the wing.

Coming Down from DT

Recently I purchased a couple of small needle nose pliers with rounded jaws, this tool works good for bending wire in nice looking loops. All the wire used was from a common straight pin. The hinge in the rear of the wing would have a good deal of stress on it so I used a small strip of fiberglass cloth over it. Two sides of 1/16” balsa were used to make a small pylon, a short length of 1/8” square balsa under center of the wing in front slides into the groove between the two pylon sides. This should keep the wing from shifting in flight. A toothpick made a good peg for the DT line to wrap around.