Lightweight Dynamic Tiedowns

[GrummanBear]

Unfortunately my “hangar” is a hail shed while waiting..and waiting..for a space to open within 60 miles of the city. See a lot of chains and ratchets. Both are relatively heavy, and ratchets have a lot of issues (rot, rust, breakage, weight, low abrasion resistance).

Solution: under 1.5 lbs combined total weight, adjustable from 2ft to 15ft, rot proof, virtually unbreakable (5200lb dynamic strength/20,000 lb static), yet has dynamic stretch which lowers the forces on airframe in high wind. The Blake’s Hitch, tied correctly, is an adjustable prusik with slight hand control, and yet will absolutely not move. Also handy for ramp tie downs while traveling.


How to make:
I retire my climbing ropes every two years from “life support” use as a safety thing. Most climbers do. For this I used my old dynamic rock climbing line. Works with 6 ultralight carabiners or stainless steel hooks. Cut to length, use lighter to melt the bitter ends, and French whip the ends with masonry line to guarantee no fraying. I also whipped the eye on the ground side for a cleaner look. Loop through airframe end carabiner or hook and tie to the line with a Blake’s Hitch. Done.

 

[AggieMike88]

Where in Texas?

 

[GrummanBear]

San Anton’. Kiddos are just east of you in Mckinney during the school year though

 

[Larry Vrooman]

The Blakes Hitch looks harder to tie than it is. It's really very simple, and after you do it once, it is very easy to remember.

- Loop the running end (free end) of the line over the standing line (the long straight portion running from the ring on the ground to the ring on the plane) four times, wrapping down and away from the tie down ring on the wing;
- bring the running end of the line back up to and *over* itself between the wraps on the line and the wing;
- run the end of the rope *under* the standing line; then
- run the end of the line along the standing line through the first 2 loops and then out through the middle of the knot.

The knot holds much better under tension so snug the line up. An overhand knot on the end and snugged up against the Blakes Hitch will help prevent it loosening if it isn't kept taut (rope stretching when wet, loose on one side with the wind lifting the other wing, etc).

Personally, I use my old static rope rather than dynamic rope, but then I have a tailwheel aircraft. Given the three point taillow position of a tailwheel aircraft when tied down, any stretch in the rope allows an increase in angle of attack which increases lift and consequently strain on the rope and the airframe.

If you fly a nose dragger where the AoA is both low and fairly constant, then dynamic line makes more sense.

 

[eman1200]

for those who prefer a visual:

Blake's Hitch

 

[AggieMike88]

San Anton’. Kiddos are just east of you in Mckinney during the school year though

If you want some company at a local eatery or watering hole, ping me and @JCranford ... we both have been known to haunt the NE side of the metromess

 

[GrummanBear]

If you want some company at a local eatery or watering hole, ping me and @JCranford ... we both have been known to haunt the NE side of the metromess

For sure! We are restoring this old tub and plan to keep it at one of the lakes in your neck of the woods when it’s done (this fall) as a place to fly in and stay to spend more time up north when the kids are in school.

Before...


Progress...

 

[kgruber]

Except, I don't cut my old climbing rope. It is long enough to do all three tie downs.

 

[GrummanBear]

Except, I don't cut my old climbing rope. It is long enough to do all three tie downs.

That’s kinda like tying both shoes with one long shoelace. Technically works, but not real practical