Custom Tether Design: Absorption & Reflectivity Questions

[thinwater]

Originally Posted by tarian

Thankgoodness I live in the EU were standards and EU directives for saftey equipment are tested ....

The US uses some EU standards, but work-at-height is governed by ANSI standards, which are, in fact, more stringent. But the framework of the rules is strict and fully equivalent.

[S/V Adeline]

Originally Posted by thinwater

Tell us what hooks you are using. (All prices from Amazon)



Kong double tether = $112


2 Kong Tangos = $60
Spinnaker shackle, 5500# breaking strength = $35
Webbing (15' to allow for sewing) = about $8 (1" climbing webbing will not meet the spec after sewing)
Elastic = $5

materials total = $115, without labor or thread.



Yes, I could sew something with 1-climbing webbing and carabiners for less. But it is not apples to apples.



3 locking carabiners = $36. Can you work these in the dark, while going through waves?

climbing webbing = $5 (mil-spec is ~ 3600 pounds after sewing, vs. the standard of 5000 pounds)
no elastic (makes it prone to tripping)
materials total = $41



It could even be safish. But it would not be comparing apples with apples. You will have to give up features.

20 yards of milspec 1in tubular webbing is $25
30kn locking hooks are $7 each. Personally I prefer non locking, but...it is a safety concern either way
I already have a roll of the elastic cord for inside the tube (tangle management) so I guess I'm cheating a little on my numbers.
Figuring 10ft of webbing per tether, 20 yards would make 6 tethers.
I need 4 tethers and I have other use for the leftover material.

[model 10]

Sewing up a tether is not rocket science. I've hung out with parachute riggers and inspected seatbelts for the FAA. It's just good sewing. If I needed to test one, I would use the tow hitch on my car.

[NPHiker]

Thanks for all the replies everyone, it seems there's a lot of wisdom and experience being shared, and I appreciate all the food for thought.

[thinwater]

Originally Posted by S/V Adeline

20 yards of milspec 1in tubular webbing is $25
30kn locking hooks are $7 each. Personally I prefer non locking, but...it is a safety concern either way
I already have a roll of the elastic cord for inside the tube (tangle management) so I guess I'm cheating a little on my numbers.
Figuring 10ft of webbing per tether, 20 yards would make 6 tethers.
I need 4 tethers and I have other use for the leftover material.

Milspec webbing does NOT meet the standard, so that is cheating. $7 locking carabiners are either non-UIAA (list source if you have a cheaper one) or are screw lock, which will either corrode or be too slow in use. They also do not open wide enough for railings, which is a short coming. Using non-locking biners does not meet the standard. The new defactor standard is via ferrata carabiners, which are not $7.

So what you have built is a non-compliant tether. You have not discovered a cheap way to make an ISO tether, you have discovered a cheap way to build... something. Go with it, if you like. It is better than nothing... unless you rely on it, in which case it may not be better. Just don't say that it meets the same standards.

[S/V Adeline]

Originally Posted by thinwater

So what you have built is a non-compliant tether.

Compliant with...what? Please show me in CG regulations where any type of tether, jackline, or other like device is required to meet some compliance to a code regarding pleasure craft. Specifically what the tether requirements are AND fines imposed if they are not present on the vessel.

[thinwater]

Originally Posted by S/V Adeline

Compliant with...what? Please show me in CG regulations where any type of tether, jackline, or other like device is required to meet some compliance to a code regarding pleasure craft. Specifically what the tether requirements are AND fines imposed if they are not present on the vessel.

The applicable standard is ISO 12401, as referenced in the World Sailing OffShore Rule. Other ISO standards cover connectors (aka carabiners). You can find these on line.



You mentioned using the "same materials" and being "better than" commercial tethers. I think we all inferred that you were aware of these standards.


Obviously, tethers are not required.

[requiem]

Originally Posted by S/V Adeline

Having done the drop test myself, maybe it's just me but it hurt alot more than any fall or wave has ever hit me. The force on the tether is huge. The force on your back and neck is hard to describe, surprised nothing broke inside.

As someone who also has some climbing background, this is a test you don't want to put your own body through. For perspective, such drops can break Dyneema slings (rated to ~22 kN). Humans are a bit squishier, however, and can absorb a bit more energy by flopping around and squeezing or breaking things (e.g. sacrifice the spleen to protect the sling), but once forces rise above 10 kN you're risking internal injuries.

This is why in climbing one should never climb above an anchor when tethered with a sling, and avoid positions that accumulate too much slack in the tether. On a boat of course you're less likely to encounter such a directly vertical fall.

Originally Posted by Marathon1150

We have also set up the jacklines and use a tether protocol that makes it nearly impossible to leave the boat over or through the lifelines. It took several full-time days and a lot of trial and error to accomplish this arrangement.

I'd be very curious to learn more about this setup; any chance you have it tidily documented somewhere?

[Q Xopa]

Originally Posted by requiem

As someone who also has some climbing background, this is a test you don't want to put your own body through. For perspective, such drops can break Dyneema slings (rated to ~22 kN). Humans are a bit squishier, however, and can absorb a bit more energy by flopping around and squeezing or breaking things (e.g. sacrifice the spleen to protect the sling), but once forces rise above 10 kN you're risking internal injuries.

This is why in climbing one should never climb above an anchor when tethered with a sling, and avoid positions that accumulate too much slack in the tether. On a boat of course you're less likely to encounter such a directly vertical fall.



I'd be very curious to learn more about this setup; any chance you have it tidily documented somewhere?

+1
Thanks

[Marathon1150]

Originally Posted by S/V Adeline

Marathon1150,
If you don't mind my asking, how much did the long arm/short arm tether set you back?

Good question but as I tried to imply in my original post, price isn’t the issue for me. But, to answer the question, the current West Marine price for the elasticized, bifurcated, Kong equipped tether is US$129. We paid a bit less.

I bought the also mentioned Plastimo single line, carabiner style tethers for way less, including a safety harness. I use the harness but never the tether as a primary because they are not bifurcated and the carabiners can accidentally be opened in some some situations.

Safety and risk are highly subjective and we all make personal decisions regarding risk tolerance and mitigation. Some people refer to me as the world’s most paranoid man.

[Marathon1150]

Originally Posted by requiem

I'd be very curious to learn more about this setup; any chance you have it tidily documented somewhere?

I have some photos that I can post soon but we used two sources of advice. One is the blog Morgan’s Cloud and second was a professional Bluewater sailing instructor that we had on the boat to do a safety audit before we left Mexico. Basically, the approach is to have a single jackline running down the centre of the boat. The long arm of our double tethers is not long enough to allow us over or through the lifelines in the cockpit. The challenge is getting from the cockpit around the dodger. We started with a jackline on top of the dodger but our solar panels were a serious obstacle. We now have a jackline on each side of the dodger that requires changing tether arms once forward of the dodger. At that point we are exposed, even using the short arm - still tethered to the boat but with some risk of being able to go over the lifelines. This situation exists for the duration of time required to clip the long tether to the central jackline in front of the dodger. We have seen boats with an accessible central jackline that is accessible from the cockpit but we were not able to achieve that situation.

[Tillsbury]

I make a lot of my own stuff, but have stopped short of tethers. I did like what Sailing Uma did with the very short tether though. I have some very high quality Spinlock tethers that are triple ended, but the long end is too long for my preference and the short end is too long (it gets in the way of things). Solution was to sew the long end up to remove almost all of its length from the join of the Y. Now my "long" end is what used to be short (5 feet extended, 3 feet relaxed, and what used to be the long end is just over a foot from my chest tether so it doesn't drag on things when I'm moving about but is available to clip on to the mast or some other point when I want to work in one spot with two hands. I mounted huge tether points at the forward and aft ends of the cockpit table support (part of the deck moulding with a big backing plate). Now when tethered aft I can stand at the helm or sit in the cockpit comfortably, and I can stand on the edge or extreme aft end of the deck at full stretch of the tether. If the stitching were to let go (it won't, it's Tenara) I'm still wearing a tested ISO tether.

So you can have the advantages of the right tether lengths for you without making the whole thing yourself, with its attendant possible liabilities.

[longjonsilver]

Aren't we ignoring the elephant in the room? It seems that most people don't use jacklines and tethers but instead rely on man overboard equipment - life rings, man overboard buoys, x marks the spot on their GPS and man overboard drills.

Isn't any sort of short tether (short enuf that you can't possibly go overboard) better than any sort of MOB drill or equipment? And yet we are discussing the theoretical possibility of the tethers breaking. How many of us know of the tethers breaking at sea - either anecdotal or documented cases? Compared to how many have died being drug by their boat with a long tether, or drowning in a MOB situation? Methinks that few if any have died as a result of a breaking tether. Tell me that i'm wrong, but i think that we are straining at gnats.

However, i agree with Marathon - on my boat, everybody is tied on to the boat at all times on deck while underway, with a short tether. (Again, a short tether is defined as short enuf that you can't fall overboard) i don't care if you are Joshua Slocum, Robin Knox-Johnson, Ted Turner, Buddy Melges, Sir Francis Chitchester, Donald Trump or Sir Francis Drake, on MY boat, you will wear your harness and tie off on a short tether on deck underway, or you WILL go ashore as soon as possible. Only He who walked on water and calmed the storm is exempt. For the rest of us: going overboard is just plain dumb.
jon

[thinwater]

The problems with dragging and "in the way" when not in use are technique.


Take the long tether and wrap it around your waste, like a belt. Then clip it back into the snap shackle (do NOT clip it to the harness--that deactivates the quick release, if you think about it for a moment). With the elastic type, you will barely know it is there.


A Volvo race guy taught me this. They know so many obvious details that mere mortals miss.

[requiem]

Originally Posted by longjonsilver

Isn't any sort of short tether (short enuf that you can't possibly go overboard) better than any sort of MOB drill or equipment? And yet we are discussing the theoretical possibility of the tethers breaking. How many of us know of the tethers breaking at sea - either anecdotal or documented cases?

Yes, prevention is usually the better fix!

The last tether failure I've heard of was just last year, due to the clip being side-loaded. Not a big surprise; the two easiest ways to break a carabiner are to load it over an edge, or to hook its nose.

If I were building a home-made tether I'd likely grab for climbing rope first, since it has more stretch and using knots is simpler than getting the stitching correct.

I'm not as familiar with sailing accidents; many of the tether-related failures appear to have more to do with the hardware fittings. E.g. split rings on the quick-release shackles failing because under load it can require ~40 lbs of force to open the shackle. However, a quick Google turns up the case of Glyn Charles, where his tether's stitching had failed when he went over the side.