Scienceguyorg Ramblings: Testing New Dethermalizers

Friday, October 21, 2016

Testing New Dethermalizers

As I am advancing from building and flying free flight model airplanes purely for the fun of watching the models fly to flying in competition, I am trying to find out what works for me. This includes improving my building skills and the products used in completing the models. Recent blog articles have been about the Gizmo Geezer propeller system but I have also been experimenting with dethermalizer systems trying both old and new technology.

BSD DT Only Electronic DT

In addition to bringing the plane down from a thermal, because of the small flying sites I fly from at times the DT is used to terminate the flight before the airplane flies off the field into a tree. The first DT’s I used were viscous timers on discus launched gliders, for short flights I was able to control it fairly accurately. When I installed a viscous timer on a P30 model that was making longer flights I found that a lot of adjusting needed to be done to get over 2 minutes before the DT released. It is not just a matter of winding the dt farther as that puts more tension on the spring resulting in the DT running faster. By a lot of trial and error with adjusting spring tension I could get 2 minute DT time but not that accurately.

Fuse DT Guillow's Lancer

From the free flight contests I have entered this year, it is apparent the use of a burning fuse is very prevalent. It is light and relatively inexpensive; with some experimenting it might be fairly accurate. To get some idea how long the fuse would burn for a given length I did some tests burning the fuse hanging out of a tube with a rubber band at the edge of the tube, like how the snuffer tube would work in an airplane. I timed the burn times and found it fairly predictable, so I modified a rubber model I have been flying the Guillow’s Lancer to use a fuse to release the front of the wing bringing the airplane quickly. Some short test flights with the Lancer and the fuse DT looked promising.

E36 in Flight

After using the Texas Timers electronic DT in my e36 model, electronic DT seemed like the ultimate solution. At the Nats and one of the local contests I talked to people using an electric band burner DT on rubber powered models. I ordered one from Starlink for the Wilbur old time rubber model I am building. BSD Micro sells some really lightweight electronic timers that I wanted to try so I ordered one for the E20 event which controls the motor and has a tiny built-in servo to DT the model. There is a rotary dial programmer box available to set the times so I ordered that as well. In addition I ordered the DT Only unit to try on rubber powered models; this unit only weighs 1.5 grams without
battery.