RC Glider Tow Release

Remote control glider aerotow is great fun and can be done with a variety of gliders and tow planes. To do it safely it is important to have a reliable and easy to use release mechanism on both the glider and tow plane.

This tow release mechanism is designed for remote control gliders in the 1m-3m wingspan size range. It is designed specifically to work in foam or balsa gliders and tow planes that need the tow point mounted in the top or bottom of the fuselage. By mounting the tow release mechanism in the underside of the glider it allows a motor glider to be towed without having to remove the motor or make any changes to the nose cone. As long as you make sure the motor can't come on while you are being towed, you don't even have to remove the prop.

Required hardware

• 1x 9g - 12g standard micro servo (works great with HS55 or HXT900 servos)
• 2x short lengths of steel wire 1-2mm diameter
• 1x M3x12mm machine screw

Supports
The main body of the tow release will require some support material for both the recess for the flange, and the slot that the pivot arm fits into. The pivot arm can be printed without support if printed on it's side, but will require some support if printed flat.

Assembly
Before assembling the mechanism you will need to drill out the holes for the steel wire in both the main body and the pivot arm. These holes have been intentionally designed under sized, so you can drill them to suit your choice of wire.
I have used both 1mm and 2mm and both work well, so any wire in that range should be fine.

Flange types
There are 3 different types of flanges that you can choose to suit your plane.

• Type 1 has a wide flat flange to spread the load or allow the tow release to be installed in an existing hole.
• Type 2 is curved to follow the curve of a glider fuselage.
• Type 3 is a small flat flange to suit flat external surfaces.

The flanges are designed to be extra long so you can cut them to length to fit your plane, or you can adjust you slicer settings to stop printing at the right height.

Tow line
I use these tow release mechanisms with a tow line made from "builders" sting line with a small loop of thick fishing line tied on at each end. The fishing line makes for an easy to insert loop, that reliably comes free without snagging on release. From my experience with gliders in the 1.5m-3m size range a tow line about 12-16m long works well.