Adam Dickson

Forming moulds from rev 1 wingtip nav light bumps

My rev 0 wingtips lack the nav light bumps found on the current rev 1 wingtips. I prefer to have them, given the work is not excessive and I have the materials. Taking a cast off rev 1 wingtips is for me the fastest way to form the shape well, faster than with clay. Another Sling 2 builder kindly allowed me to take such moulds from his wingtips. 2L of a flexible moulding product Pinkysil was used, 1L for each wing. The relevant wingtip areas were smeared with a thin film of petroleum jelly, as a release agent. The cables were terminated with some fishing line pushed back into the wingtip. The fishing line was then taped down and routed outside of the area of the moulding. The rivnut hole was sealed with tape. Casts were taken, the curing time was about 30mins, the moulds were readily removed, and the petroleum jelly and stray pinkysil removed with Isopropyl alcohol.

The fit is good when the moulds are placed on my wingtips, although I note the outer edges of the rev 0 parts are sharper than the rev 1 parts.

Due to the limited amount of Pinkysil available, together with some wastage, some of the taper at one end of the bumps was missed. I have augmented the moulds with silicone rubber to amend this which will assist forming this taper. This will also help with making flanges if I make a hollow bump structure. The Shore A hardness of the silicone rubber, at 25, is similar to that of the Pinkysil, at 20.

I plan to use these moulds directly to form the bumps, either by filling with epoxy (and flock) or by making a hollow structure building up from fibreglass tape and epoxy.

This post is from Adam Dickson