Pull-Pull Kevlar Cable from TBM

[Vic3D]

Pull-Pull Kevlar Cable from TBM

This kevlar cable is used in place of the commonly used steel cable. Steel cable is good, and has good tensile strength, but it also has disadvantages. I have already snapped a cable flying on 2 planes in the past couple of years. Even though the Kevlar frays much easier, its tensile strength is larger than the steel cable. Another common issue in steel cable is that when you cross the cables inside the fuselage, you have a metal-metal contact that can cause RF noise. My favorite part of using kevlar cable is that it won't stretch with use like the steel cable.

Advantages of Kevlar:

• Light-weight
• More tensile strength
• Eliminates metal-metal contact in rudder system
• Easier to install
• Does not stretch

Disadvantages of Kevlar:

• Frays much easier than steel.

Installation:

I used the same hardware I had on the rudder system of my 41% Wild Hare Extra 300. I removed the old steel cable and proceeded with installing the kevlar. I did not feel like crimping the kevlar would work as good as it does on steel, so I decided to use 4-40 threaded hooks that screw into the ball-links. This way I can just double-knot (twice) the cable and be done with it. I threaded the hook with 3 loops of cable to give it more grip. Also, remember to tie a knot on the slack so the double knots don't come undone. I had to make sure the cable wouldn't rub against the fuselage so I installed small fuel tubing over the cable where it exits in the back (not shown in pics). You can also accomplish this with heat-shrink tubing and a couple drops of CA.

Flight testing:

The cable worked flawlessly, no slop and no signs of weakening after a couple of relatively rough 3D flights.

This cable comes in 24' rolls and sells for $2.95. Here's the link: http://troybuiltmodels.com/GHardwarePull.htm#PULL

Vic

[thewrap]

Good find there Vic

[SMOKEY]

Aerospace composite has a coated kevlar cord. They have 2 sizes. The larger cord is rated to break at 215 lbs. At 100 lbs load, the cord stretches 4.8 percent from what i remember. I inquired about this for my SD 40% yak.

Smokey

[Vic3D]

	Quote: Originally Posted by SMOKEY
	Aerospace composite has a coated kevlar cord. They have 2 sizes. The larger cord is rated to break at 215 lbs. At 100 lbs load, the cord stretches 4.8 percent from what i remember. I inquired about this for my SD 40% yak. Smokey

Wow. That is a whole inch in a 40 inch long cable.

I don't know if 40% rudders get up there though. Any aerodynamic experts care to chime in?

[N726AC]

Hey Vic, I have used TBM Kevlar pull-pull on my 35% SD Yak for over two years with no problems!