This project is to create fairings to protect the aileron and flap servos from damage when the glider runs along a grassy runway during landing.
When the Radian Pro glider lands on the grassy runway at my local flying club, the servo horns controlling the ailerons and flaps run across the top of the grass. The horns can be grabbed by the grass and cause the horns to be wrenched with a force that can turn them on the shaft of the servo, jumping over teeth on the spline! The glider spins around instead of gliding along the ground in a straight line and when the glider stops, the aileron is not at the neutral position where it should be. This has happened to my glider and to radian pros of a few friends as well. The solution is to make fairings to protect the servos.
Making the Moulds
The first mould is made from pine wood on a three ply base. Holes are drilled along the internal corners to ensure the HIPS sheet is drawn right into the corner. The mould is coated with a thin layer of wood filler and sanded to make a smooth surface. A cavity is made underneath the mould so the holes drilled through to the base can connect with the holes in the top of the vacuum forming box.
Making the Fairings
The fairing is made from 0.5mm HIPS. After the first was made, I made three more moulds by pouring ‘plaster of paris’ into a form.
Each form makes two fairings by cutting the form in half. With four moulds in total I can make eight fairings from one HIPS sheet.
Attaching the Fairings
The fairings are attached with double sided foam tape on the underneath of the fairing flange. Alternatively, reinforced tape can be used on the top of the flange.
In these photos below, it can be seen that the tip of the servo horn is only about 5mm above the line from the wing tip to the bottom of the fuselage. This is why the grass can grab the servo horn. With the fairing installed, it acts like a skid and lifts the wing above the grass and conceals the servo horn safely inside.
These fairings have proven to be useful on other types of gliders which have been supplied without servo fairings. At the time of publishing this page, I have made seventy of these fairings for other members of my flying club.