Replacement of hinge bracket rivets - selection

To explore possible fixes of the 0.9 degree rotation option, I considered the possibility that there might be a some play associated with the 3/16" AN3 bolts, or matters might be better if the hinge was rotated 180 degrees. I removed the remaining 4mm stainless steel rivet. The first rivet had already been removed since the gun jumped and the rivet was set about 0.5mm proud of the surface.

This left the question of how to get replacements. TAF Australia held no stock.

Calculation of required grip range: Hinge Bracket 1 (2.5mm) + Spar Doubler Channel (1.3mm) + Spar Channel (0.64mm) + Control Horn Mounting Angle (2.5mm) = 6.94mm minimum (7.30mm measured, including primer)

The grip range of Bunnings 4.0mm is 6.4mm - too low

AB Bolts & Nuts held 4mm stainless steel rivet from (either) Hobson or Bremic

The Hobson data sheet gives a guide to the appropriate 4mm rivet: Shell code 5 = 4.0mm, rivet number 56 with a grip range 6.5mm-9.5mm and length of 14mm is appropriate

Enlarging the hole to 4.8mm was considered, but according AC43.13-1B page 4.20 the distance from a rivet hole centre to the edge of a plate should be at least double the rivet diameter. This distance, for the hinge, is 8mm precluding the use of anything larger than 4mm.

The rivet when pulled in space, was seen to span a roughly elliptical cross section 4.6mm - 5.2mm. This was all in excess of 4.1-4.2mm of the existing nominally 4mm hole in the aluminium spar channel and doubler, and just in excess of the slightly swelled hole in the hinge plate, of 4.1- 4.3 mm.

Re-riveting the existing holes seems justified

Re-riveting of the control horns to the control horn mount also was considered. The combined plate thickness is 5.5mm, falling in the 4.9-6.4mm grip range of a rivet number 54, with rivet length 10.8.

It was noted the rivet head was non-magnetic and the rivet tail was slightly magnetic (about 30% that of steel). The rivets are 304 stainless steel. This is stronger than type 316, but less corrosion resistant. These rivets will be coated once reinstalled.

The required grip range for the rib 1 reinforcing angle 4mm rivets was measured to be 6.15mm (including primer), so this was just within the 0.5-6.5mm grip range of the 4x10mm aluminium polygrip rivets