Sullivan Wingtip Extensions

[stevesaircraft(Bri)]

I have a set of wings that I am restoring, fitted with the Sullivan tips.

When I pulled the tips off, I was surprised to find 2 x 1/4 inch solid plywood end ribs which the fibreglass tips screw to. (This mod was installed in 1987 when the aeroplane was converted to a tailwheel 22/20. Originally it's home was Cashmere, Washington but it came to Australia via the UK) I weighed them (almost 6 pounds each.) and immediately decided to use Univair butt ribs as replacements.

I have the original drawings and installation notes in my files and would be happy to scan them and email them to you. All I need is an email address.

The plywood is original to the STC. The STC has you screw on the tips and glue 3 inch fabric tape over the "seam" making them hard to remove if needed. That is the main reason I like using the aluminum rib with nut plates so its easy to maintain.

--Brian

[nogoodusernames]

I got ahold of Mr. Sullivan! A little while ago, but I've been busy getting my airplane disassembled.

Answer #1: No nose ribs are necessary or included in the STC data or drawings.

Answer #2: I'm just re-using what was on the Colt. It's .020 inch (all dimensions in inches hereafter).

Answer #3: The spar web extension is .090 minimum, he said I could go bigger if I wanted to. They are 16" long, and 5 3/8 and 3 13/16 (if my notebook is accurately interpreted) for front and rear respectively. He told me I could make them a few thousandths bigger and therefore less sloppy if I wanted to (so I did). I should have just cut them to his dimension. It would have saved me time on the belt sander. He said not to use anything super soft, but otherwise, the aluminum grade didn't matter much. I got some 6061 T6. I figured that wouldn't give me any trouble.

Answer #4:Hole size is #10 drill. There are four bolts through each extension. Two through the original web, and two at the tips through the holes that attached the brackets that held the wood bow.

Answer #5: Apparently just about any old aluminum extrusion will do, as long as it's not too small or thin. I got 3/4 x 3/4 angle, with 1/8 wall thickness. It seems to be fine.

Answer #6 (and #7): This is now obsolete, but formerly he just made some aluminum channel with .032 aluminum to back up the connection between the angle and the rib. Now, the rib is different. He made his own stamped ribs formerly, but now he tells people to use the Univair stamped ribs. This requires something to fill up the space that would normally be filled with the spar. I used some of the .090 plate I used for the spar extensions. Riveted to the Univair ribs, it took care of that.