Upgraded Pawnee Tow Release and Bridle

[Sinkhappens86]

When I picked up my Pawnee from Jim Dolly last summer one of the conditions was that I needed to try his new and improved tow release location. We had discussed the fact that the normal tow release location is very far behind the CG and believed it was causing issues with larger gliders. Steve K's experience towing with the Pawnee vs the Porter seemed to confirm this. Jim's plan was to move the release location about 10 inches forward and use a bridle. So he left me with a couple marks on the side of the fuselage and told me to make his vision real. (No pressure)

So here's what we started with.













The first decision that needed to be made was whether to release on one side or both. Losing the bridle every time you need to dump a glider seems frustrating but having the loose bridle wrap around the elevator seemed worse. Decision was easy.

Next step was to reinforce where we wanted to put the releases. We used two of these from Alex at iflytailies.

https://www.iflytailies.com/store/tow-releases/

Here you can see the first reinforcement and the plywood rails for the servo installed. We used long pieces of rod to figure out where the servo should be positioned.










The final step was to cut the rods to length and add some gussets behind the release for some extra strength.



The bridle was made from some leftover tow line since we had upgraded to paracord. Probably should make something a little nicer looking, but it gets the job done.

[Sinkhappens86]

So what's the verdict on this location? The Pawnee was pressed into tow service on it's second flight ever at the Vermont Aerotow. I can sum up my experience with it in two stories.

First was towing a 6 meter Ventus, as soon as he released the pilot apologized to me saying "Sorry I got really messed up there" I didn't even notice or feel anything!

Second was a Swift that was doing aerobatics on tow. During one tow he got ridiculously low, way out of position and no glider should ever be there. It was mildly annoying, but I was never in danger of stalling or losing control.

Since then the bridle has been rock solid. Based on my experience compared to Steve K's normal release location, I would say this set up is superior in just about every way. It feels locked in when towing every glider I've had behind it. Jim Dolly was right, imagine that!

[jgallacher]

Nice pic of the Pawnee. I use a bridle on my turbo Duster tug. I have to release the line before landing and found the ends of the bridle getting tangled in the servos located by the elevator, Added 18" length of Ny-Rod outer tubing to the bridle and the problem went away.

[ARUP]

Now... that's cool! Great idea about the nyrod on the bridle, too!

[kd4jaz]

Can the tow point where the bridle comes together behind the tail slide from side to side or is it fixed in one location? Please post a picture of the tow line attach point (behind the tail)

[Sinkhappens86]

I am out of town for work for the next week or so. But I will take a picture when I get home. Each release has a line that simply runs to a swivel hook (Just like we use on the glider end) and is tied to it. Not sure if that answers your question, but I will get a picture soon.

[kd4jaz]

Is the tow line fixed at the point BEHIND the tail, or is it free to slide from side to side like on an old ski bridle behind a boat. Please reply to kd4jaz@gmail.com
Thanks,
Marc

[jgallacher]

I use a bridle on my low wing tow plane. I found that when released the bridle can get tangled with the tail plane hardware. I used a NyRod cover tube on both lines that extended past the horizontal tail surface. This fixed the problem.