Update 12-01-2020: Lucas from Univair called me back. He’s been very helpful, but can’t give me a good answer on how to set the drag wire tensions. He gave me a name of an engineer at Univair (Mike Wotovitch) who I haven’t called yet, but Lucas talked to him and said I could call to discuss it with him. Apparently, everyone who would have known is either retired or worse yet, no longer with us.

Update 11-30-2020: I spoke with Lucas at Univair and he thinks the right wing drawing (-1111001-1DWG, at $154.54!) they have contains the info for the drag/anti-drag wires. I also spoke with Gary Redden and he doesn’t think so. Lucas is going to open the drawing when he gets a moment and check it for me.

To mark the measuring points, I drew a line straight up from the centerline of the compression tube to the front and rear spar with a square, then marked the point midway on the spar and made a T. The spar measured 1 1/2” so I placed the mark at 3/4”. I did this on each section of the wing. The wing root bay was hard to do because of the drag wire attachment point being behind some brackets.

Then, using my trammel device, I measured each bay from those points. One Piper owner said to start the measurement from the wing attach point using a bolt for the first measurement.

I read a post on the Short Wing Piper Club about checking the drag wires and it matches with what I’m doing, pulling the wire 1/2″ at the center of the bay and reading the tension. – jlk

Wow. Not much information out there on this subject. I had a wing drag wire that was loose and I tightened it up. Now I need to make sure the wing is straight and the drag wires have the correct tension. The maintenance manual only provides the drag wire tensions, but not how to set them.

Now, the wing drag tension is a bit tricky. Again, nothing in the manual on this except the tension values. Nothing on how to check them. I watched a video by two gentlemen ( https://www.youtube.com/watch?v=X2fU-1TQg-g )checking the drag wires on a cub and this was their setup. Not sure if the 1/2” pull distance is the same for the Stinson wing. The Stinson service manual provides the tension settings for each bay, but that’s it. I guess this was common knowledge back in the 40’s, but it isn’t now.

The bay I’m testing in the photo is the third bay in from the wing root. The book says 82 lbs of tension, so about 7 ft/lbs of pull. I’m getting 10 ft/lbs on both wires. I’m guessing that if both wires have an even pull and it’s close, it’s good. Any comments?