A Better Leash Design

[Beasho]

With winter comes bigger waves.  Having broken my leash several times I am now interested in a better leash design.
 
Does anyone know where to source the 5/16”, 11/32” or larger diameter surfing grade polyurethane cord?
 
I have been having a very difficult time finding the source for polyurethane leash material on the web.  I found one type that appears to be close, but slightly softer and more stretchy.  I would assume that this material could be acquired easily but haven’t found any immediate sources.

[Beasho]

Seasoned surfers swear by the ‘hand tied’ leash.  The following photos show where the leash broke.  Note that the hand tied design actually strangled the polyurethane.  Red arrows show compressed material.

Testing the design on a bench showed that with each successive large load the leash end pulls, and ‘necks’ (shrinks in diameter).  The result is that the rigging then tightens its noose and never allows the polyurethane to regain its original diameter.  Failure may (unfortunately) be a simple function of load size X cycles.  (see dissected view of leash in 3rd photo)

However, since I am using a waist harness it would be great to simply swap out the middle section of the leash, and/or replace with a less expensive option at shorter intervals.  Alternately, learning from Kenalu, the thimble design (that I have been testing below) allows for a leash to be modularly changed very quickly.  A back up could even be stashed inside your wetsuit thus saving a session (?).

[Beasho]

The design I have been testing below uses a stainless steel thimble, similar to what is used with wire rigging.  Ideally the thimble distributes the load without pinching.  If tied correctly around the tail end there may also be an opportunity to allow the leash end of the poly to recover without strangulation. 

Could there be something to this design that might prevent the leash from failing at the ends?

[surfcowboy]

This looks good. Anytime you can lessen distortion of a material you are making it less likely to fail.

Is the tie as strong? What's under your string wraps?

[getsupngo]

Still haven' t broke the 15 foot long one.
Many shorter ones have broke and are done.
If it were any longer.
I'd call it the big donger.
Hard to say what use if the board was aluminum.

 
 

[DavidJohn]

This is what you're looking for... http://surfforsanity.com.au/2012/08/11/balin-surf-sup-leash-review/

DJ

[supguy35]

i use the dakine big wave leash you have to go to a shop and most likely have them order it.

[Sup-position]

We used these in conveyor systems.

http://www.habasit.com/en/round-and-trapezoidal-belts.htm
The Belt is weldable, end to end.


heavy duty would be..
12 mm = 8% elongation at 45.8# force.
10 mm = 8% elongation at 31.9# force.

[Beasho]

The Habisat looks promising.  A bit worried about the caveat:  "Protect belts from sunlight, UV-radiation, dust." 

Have you actually used this stuff, and can it be bought in lots 10 feet at a time e.g. how much would 50 feet cost?

[PonoBill]

The Balin leash looks like it's tied like your failed leash. The easiest approach to get material might be to buy a heavy surf leash and modify it. Once you strengthen a failure point you reveal others. I've seen leashes break in the swivel, at the cuff attachment, and at the railsaver attachment as well as the rope that attached leash to board.

The PU rope generally breaks at flaws. If you knick the surface of the rope it creates a stress concentration point, just as the necking does. One reason I'm less than thrilled with current coiled leash construction. They all have a little heat mark at the end of the coil. No idea why it's there other than a manufacturing limitation, but I think it's a potential weak spot.

I've been adding "second chance" connections to some of the weak points by adding a loose loop of kite line so that if the attachment breaks, the kite line will probably hold through at least that incident and give you a chance to see the failure. Of course one of those loose loops Jammed in the rudder drum on Headmount's board the other day, causing substantial rudder grief. 

That's a great direction. I'd be looking for a plastic thimble to reduce the missile hazard and perhaps help abrasion.

Now we just need to figure out how to stop swivel failures.

[Wetstuff]

 Beasho  ..If you want some to try - I have a couple of spools of 3/8's (.375,9+mm) translucent rojo that I used on another job.  I'll send you a test length..    PM'me.

I got a Sticky Bumps coil leash ..about 7-8mm x 10' with (what seem to be) proper moulded ends. I had to mod it to change it from ankle to below-the-knee attachment.

Jim

[surfcowboy]

The UV applies to everything. I'll bet it's swapped way before that's an issue. Remember that a belt on a machine would run in the sun for 12 hours a day for years. You'll succumb to uv damage before it does.

[Beasho]

I'd be looking for a plastic thimble to reduce the missile hazard and perhaps help abrasion.

Now we just need to figure out how to stop swivel failures.

Pono: Great idea!  Here is how it looks using a plastic thimble after a few bench tests. Granted this Poly was a bit stretchier & softer than the surf grade stuff, but you can see how the design is crawling around the thimble.  The plastic might be a bit more tacky than the stainless? 

What I am thinking of is a sleeve around the leash end, then affixing the tail somehow to this sleeve. Ideally the load is distributed via skin friction to the thimble, and then the remainder held by the tie.  The sleeve would be key to allowing the leash end to recover, thus not crawl, after load.

I agree that there will always be a weak link its just uncanny how a new leash almost never fails, and the vast majority of failures (90% in my experience) have been the polyurethane rather than other related components.  Eventually we have to worry about plugs coming out, leg tendons and boards just breaking. 

I aspire to a solution like the PowerEx Skinny mast.  When I used to  windsurf I broke 5 carbon masts in 2 years until I bought a PowerEx skinny.  10 years later I never broke another mast. 

Note too:  The addition of clear shrink wrap allows for inspection of internals thus potentially averting imminent failure. 

[eeck62]

Resurrecting this thread as I too am trying to figure out a better leash design.  I just stretched my Ocean and Earth Ultimate leash from it's original 8ft to at least 20+ ft when my board got caught perfectly by a wave.  Unfortunatley it only came back to about 11ft, which I can't stand, and it looks a little stringy.  It did not break and leave me swimming though.

Thoughts:
1. I like shorter leashes (7-8ft) as I get my board quicker.  Leashes that short don't seem to come in a thick enough diameter.  Also, it is probably harder on the leash being short.
2. I like the Creatures of Leisure design (or any similar design) where the leash cord attaches via the dynaflex end that helps evenly distribute the load.  The even distribution of load prevents stress points.
3. The Ocean and Earth moulded end is a great design for even stress loading preventing a failure point.

The plastic thimble is good if you can keep it from rolling.  We used the same type of connection with large cables.  The difference I see is that the cable end extends a couple feet from the thimble with several wire rope clamps on it preventing the wire rope from rolling around the thimble.   I could also see using some shoe goo glue or something similar to provide friction and prevent the thimble from rolling.

I have some ideas I am going to test and will report how they turn out.  In the mean time I ordered a short Crow Haley waist leash 

Erik

[Dwight (DW)]

Resurrecting this thread as I too am trying to figure out a better leash design.  I just stretched my Ocean and Earth Ultimate leash from it's original 8ft to at least 20+ ft when my board got caught perfectly by a wave.  Unfortunatley it only came back to about 11ft, which I can't stand, and it looks a little stringy.  It did not break and leave me swimming though.

Thoughts:
1. I like shorter leashes (7-8ft) as I get my board quicker.  Leashes that short don't seem to come in a thick enough diameter.  Also, it is probably harder on the leash being short.
2. I like the Creatures of Leisure design (or any similar design) where the leash cord attaches via the dynaflex end that helps evenly distribute the load.  The even distribution of load prevents stress points.
3. The Ocean and Earth moulded end is a great design for even stress loading preventing a failure point.

The plastic thimble is good if you can keep it from rolling.  We used the same type of connection with large cables.  The difference I see is that the cable end extends a couple feet from the thimble with several wire rope clamps on it preventing the wire rope from rolling around the thimble.   I could also see using some shoe goo glue or something similar to provide friction and prevent the thimble from rolling.

I have some ideas I am going to test and will report how they turn out.  In the mean time I ordered a short Crow Haley waist leash 

Erik

You just confirmed what I've always thought. The Ocean & Earth Ultimate leash is the best. It stretched 20 feet and didn't break. Exactly what I want my leash to do.  BTW, Slater's Kommunity Project leash is identical.