any reason not to use double braid (dyneema/polyester) sailing rigging for rope mod?

[raisins]

Stumbled upon this genre of rope. Here's one example of many.

https://www.westmarine.com/buy/sams...ack-sold-by-the-foot--P011595725?recordNum=24

The 5/16" is equivalent to 8 mm and is $1.41 a foot, which fits the budget. This would be used on Hawk Helium sticks with a versa button. I did the math on stretch and how far the stick slides down the tree, and with standard accessory cord it just won't be acceptable to me (this might cause the kick out some say rope causes but webbing doesn't). This rigging will stretch much less than webbing. I feel it has the properties of amsteel but with the positives of "normal rope" (has a protective covering, will hold a knot, etc).

So please tell why this might not be a good idea! I'm going to order 10 feet first and play with it and then order another 30 feet to finish 4 sticks total.

Samson and New England both make quite a few ropes like this, which vary in price. I can't tell why they vary in price just by reading the description. They all basically say the same thing to my eyes. There are many hunt friendly colors. I'm guessing the one I linked will look like gray tree bark from a distance.

Thanks - R

 

[KYHunter]

That seems a little pricey if I’m reading the site correctly. Why don’t you look into Amsteel Blue or regular Amsteel? Super strong, almost no stretch and is considerably cheaper

 

[raisins]

That seems a little pricey if I’m reading the site correctly. Why don’t you look into Amsteel Blue or regular Amsteel? Super strong, almost no stretch and is considerably cheaper

It's $1.41 for a foot of 8 mm line.

I think this stuff is just amsteel with a jacket.

Good point, but I was told that amsteel abrades pretty easily, doesn't like to hold a knot (slick), and is skinny (I think that would make the versa button wrap less binding) This stuff avoids all that, and I don't mind paying $50 for rope I'll use for years and that I need to trust.

 

[enkriss]

I would go with spliced amsteel over that. I had 5/16 amsteel on my sticks for 6 years.

 

[raisins]

That seems a little pricey if I’m reading the site correctly. Why don’t you look into Amsteel Blue or regular Amsteel? Super strong, almost no stretch and is considerably cheaper

Maybe I'm looking at the wrong places, but I'm seeing 5/16" Amsteel as being around the same price, sometimes more.

 

[Sandor27]

Only reason not to would be cost. I use this 5/16 (8mm) on my sticks.

https://www.amazon.com/Blue-Ox-Rope...&qid=1552430246&s=gateway&sr=8-37-spons&psc=1

That's only $0.37 per foot. At 2600lb strength, you'll be fine. I'm on my 4th season. Also nice that you can splice an eye loop and not have any knots at the button.
Stretch has never been a problem.

 

[KYHunter]

@raisins it sounds like you’ve sold yourself on it so give it a shot! Let us know how it turns out?

 

[Sandor27]

I'm curious about the math you did on stretch. What forces you estimated on the rope, what results you got... How far will the stick slide. Please share for the Geeks in the audience. Thx!

 

[raisins]

Sandor,

Thanks for the interest. I'm not an engineer or physicist, but have had some physics courses.

The more I think on this problem, the more I realize what a gross oversimplification it was; and how neat this question is. I knew about several things I ignored, but they keep growing! I won't list all my assumptions nor detail my exact thought process because that would make this become a very long post! It would be fun to discuss though.

Here's a low stretch rope for example.

http://www.novabraid.com/rope/novablue/

I couldn't find the same for nylon accessory cord, but used this as a decision point. If this is "bad" then accessory is worse.

For a 5/16" rope, I assumed a 4% stretch under my weight, using the chart on that page.

Assume a 2 foot diameter tree. That's one leg of a right triangle. The hypotenuse is the cross sectional length on the tree after stretch. You can use pi etc; but it simplifies to 2*1.04 = 2.08 ft. So, if you eye balled a yard stick from left to right on the tree along the stretched rope, it'd be around 2.08 ft under a 4% stretch.

Plug all that into the Pythagorean theorem (2.08 as hypotenuse, 2 for a leg, solve for little leg) to get the little leg of the right triangle, and that ends up being 6.9 inches.

-R

 

[raisins]

Sandor,

Thanks for the interest. I'm not an engineer or physicist.

The more I think on this problem, the more I realize what a gross oversimplification it was; and how neat this question is. I knew about several things I ignored, but they keep growing! I won't list all my assumptions nor detail my exact though process because that would make this become a very long post!

Here's a low stretch rope for example.

http://www.novabraid.com/rope/novablue/

I couldn't find the same for nylon accessory cord, but used this as a decision point. If this is "bad" then accessory is worse.

For a 5/16" rope, I assumed a 4% stretch under my weight, using the chart on that page.

Assume a 2 foot diameter tree. That's one leg of a right triangle. The hypotenuse is the cross sectional length on the tree after stretch. You can use pi etc; but it simplifies to 2*1.04 = 2.08 ft. So, if you eye balled a yard stick from left to right on the tree along the stretched rope, it'd be around 2.08 ft under a 4% stretch.

Plug all that into the Pythagorean theorem to get the little leg of the right triangle, and that ends up being 6.9 inches.

-R

Actually, I might not be too far off.

At around the 3 min mark here

You can see the rope move from roughly parallel to angled. Of course, there's a lot going on here, but again to simplify:

I paused the video and using a ruler and assuming his boot is 12 inches, I get a downward slide of 6.9 inches. (on my screen rope moves down around 1" and boot is 1.75" in length)

(1/1.75)*12 inches = 6.9 inches

Also, his tree is less than 2 foot in diameter. I think this helps the stick slide less. So, if he did this on a 2 foot diameter tree, I'm betting the slide would be like 8 inches or more. Too much for me in comparison to my stock straps pulled tight. I think he is using nylon accessory cord here, which is stretchy.

It seems you are trading noise from metal buckles for noise from the sticks sliding farther down the bark, if using accessory cord anyway.

Edit: Interesting realization I had while pondering this/reading, if you pinned a rope to the back of a cylinder and stepped on the front, and the cylinder was frictionless, then with a large enough cylinder you have so much leverage on the rope that your body weight could easily snap it (would have to be a big cylinder though).