Dethermalisers (D/T's)

You've built your model, you've followed the trimming tips on the Thermal Scout and Launching Advice pages and you are ready to start flying. If you haven't done any throwing for many years don't expect to reach great launch heights immediately, greater height at launch will come with practice.

Assuming you have trimmed your model and the model is gliding well, the next thing you will want (inevitably) are longer flights, good height at launch will give you these but the longest flights of all will come when you are able to launch your glider into rising currents of warm air - known as Thermals. If your glider enters a Thermal it will rise rapidly and could travel out of sight.

If you are flying your model on a small field, being able to bring the model down before it becomes un-retrievable has many benefits. The time required for a single UK competition flight is 1 minute (commonly known as a 'Max' ), so again there is no point in expending more energy than necessary when retrieving. We want to bring the model down to earth after 1 minute (or sooner) - how do we do that ? Answer :- With a simple dethermaliser mechanism (D/T).

The simplest mechanism is the burning (smouldering) fuse type, the fuse has a red spiral line running through it, each segment represents about 1 minute burning time.

The d/t fuse is passed through a small rubber band and then lit (see photo's).

The fuse burns down to the rubber band, when the rubber band is burnt through it releases a line which in turn releases either a Flap / Boom or Elevator, the models aerodynamic stability is upset and the model comes down to earth.

The aluminium tube that the fuse passes through acts as a 'snuffer' tube to put out the fuse.










Replace the plasticine (clay) with lead - set into the nose.




The fuse burns through the rubber band allowing the tail boom to be pulled into the D/T position







The tail boom is pulled up and the model descends to earth.







Ibis has a pop-up wing D/T.






On Ibis my D/T tube is set into the fuselage close to the wing.

When the fuse burns through the rubber band air pressure causes the wing to pop-up.






The wing in the D/T position.

(Aluminium foil is fitted to stop the fuse burning the model.)

In this position the model will descend gracefully to earth.








I taught I taw a puddy tat!
I did! I did tee a puddy tat!