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Old 05-02-2011, 04:48   #1
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Why Are Tethers so Expensive ?

I just ordered materials to construct a safety harness, and I'm looking at tethers, and I can't believe how expensive they are ( $100+). They're just made of shock cord, tubular nylon webbing and s/s fittings. All relatively inexpensive materials readily available.

What am I missing that makes them so expensive?

Bill
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Old 05-02-2011, 04:57   #2
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Most have expensive hooks.marc
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Old 05-02-2011, 05:30   #3
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What is your life worth? Tested specific hardware and higher quality *shock cord* is part of what you are paying for. Hooks that can be manually disengaged but will not unintentionaly disengage when rotated on their attachment point is one of the safety issues with tethers. Newer tethers have alittle indicator flag that lets you know when the item has been exposed to force that is likely to render it essentially non functional, or at least not able to withstand possible sudden huge strains and jolts.
Those are a couple of the things I for one do not feel able to duplicate as well as those who are the *experts* at it.
Fair Winds and be safe out there.
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Old 05-02-2011, 06:35   #4
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tethers

The first two posts have their merits. The high price is also known as the manufacturer's legal defense fund.

BTW, you can easily make your own to your own design specs. More than 50% of the tethers on my boat are 'homemade.'
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Old 05-02-2011, 06:53   #5
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When your on the pointy end drinking green water your awfully glad spent 200$ on a good tether
I sail with a guy whose tether is a 6 feet of 3 strand and two climbing carbinners, not sure its isaf legal but he hasnt fallen off the boat yet.
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Old 05-02-2011, 06:59   #6
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I made my own with the same components for a fraction of retail. But I have a buddy with a heavy duty sewing machine. He's sewn lots of stuff for me and saved a ton.
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Old 05-02-2011, 07:03   #7
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Its a rip-off, plain and simple. At the end of the day its just a resilient piece of plastic, just like any running rigging on the boat, which doesn't cost USD 300 per metre. You can get cheap ones (as in sensibly priced ones) every so often though, look around on the internet.
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Old 05-02-2011, 07:04   #8
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I've always thought they were over engineered too, as if we were going to use them for bungee jumping or mountain climbing. They are after all just a substitute for the other extreme which is a rope with bowline on each end.

How far can you fall on a sailboat? I've reduced that to almost nothing by routing the jackline right down the centerline from the stern under the boom to the mast and then to the bow. I clip on in the cockpit and the tether is just long enough to walk the perimeter of the boat--I couldn't jump overboard if I wanted to. This greatly reduces what the tether might have to do.
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Old 05-02-2011, 07:36   #9
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A lot of valid, conservative answers. They don't sell a lot of them, and that always drives up prices. I like to make my own for the simple reason that I sail catamarans and the lengths are never right for me.


Tubular webbing. Simple. The sewing must be proper; I would suggest breaking some samples (reduced stitching will allow them to break under body weight, then do the math). I used to manufacture climbing gear.

Shock cord. This is only for ease of self-retraction and is not a failure factor. In fact it is a mixed blessing; on some boats it helps keep the cord out of your way, and on other the opposite, as it makes the cord harder to flip.

Hook, Jackline end. Since we leave the tethers hooked on the jackline, a simple non-releasing carabiner is safe. If you are clipping on and off frequently you might want something else. Climbing locking biners are subject to corrosion and must be lubricated several times each season. Non-locking biners should not be used on this end, as levering off is possible.

Hook, harness end. If you gave me a tether with a spinnaker shackle, I would cut the shackle off and place it in the spares box. I've seen too many come off spinnakers and they take 2 hands to close securely. Ask a rigger if he would ride a spinnaker shackle to the mast head, or a climber if they would use one; they will think you are daft. I like wire gate climbing biners; there is nearly no chance they can lever off the harness end and I'm certain I can get them off under load, as I have done so many, many times climbing. But there are some nice double release SS biners out there now, a better choice. DO NOT use ordinary climbing biners; the gate will corrode and hang open, which is very bad. The wire gate biners like the marine environment just fine.

Fixed anchor points and jackline endings. These should always be examined, for the odd angle stresses they can place on hooks can be devistating. Even if the hook does not open, most hooks will fail at 4-10x below their rated strengths if loaded from the side. If there is great stress on the gate, even the locking gates can fail. I have seen dozens of carabiner and snap hook failures, sailing climbing and industrially, and ALL of the failures were do to miss-loading. It is best if all fixed points can swivel or flex in some way.


A few of my own thoughts on Jacklines, tethers and harnesses:
Sail Delmarva: Climbing Gear for Sailors; or Jacklines and Harnesses for the Unemployed
(Yes, there is a picture with a normal biner on the harness end. Don't do this. I was taking a bunch of kids out on a breezy day and was short on gear. IT was much better than nothing.)

Some calculations on jacklines. I once pulled the jacklines off a boat with my hands, even though the fittings all met code. His installation had too great a force multiplier.
Sail Delmarva: Sample Calculations for Jackline Stress and Energy Absorption

Some other applications of climbing gear, not exactly related.
Sail Delmarva: More Climbing Gear for Sailors
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Old 05-02-2011, 10:38   #10
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Originally Posted by GorillaToast View Post
I can't believe how expensive they are ( $100+). They're just made of shock cord, tubular nylon webbing and s/s fittings. All relatively inexpensive materials readily available.

What am I missing that makes them so expensive?

Bill
They have to be tested, certified and labeled to put on the market. You could sue them for a failure so they have to pay insurance to cover their ass. And that all adds up.
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Old 05-02-2011, 11:09   #11
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Their complicated carabiners are probably a very low volume product compared to climbing issue biners. The climbers don't use those double latch units at all, too heavy. Also it's important to remember that they're there not just to catch your body weight but your body weight accelerated through 20 feet with 10,000,000 gallons of green water pushing you and you STOP at the end of the line, hopefully.
Regardless, I plan to make my own. I used to climb so I'm familiar with the loads and construction techniques and both of my parents are upholsterers so I can sew well.
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Old 05-02-2011, 11:58   #12
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Their complicated carabiners are probably a very low volume product compared to climbing issue biners. The climbers don't use those double latch units at all, too heavy. Also it's important to remember that they're there not just to catch your body weight but your body weight accelerated through 20 feet with 10,000,000 gallons of green water pushing you and you STOP at the end of the line, hopefully.
Regardless, I plan to make my own. I used to climb so I'm familiar with the loads and construction techniques and both of my parents are upholsterers so I can sew well.
You will find that marine and climbing carabiners, and other lifeline components are built to the same strength ratings; about 4,500-5,000 pounds. In reality, if an item breaks at even 4,000 pounds attached to a chest harness, you will likely have serious internal injuries.

The longest fall I ever caught while climbing was about 100 feet. The impact was not great, as the equipment is designed to absorb that force and limit the impact on the climber to about 1,200 pounds; this is a UIAA requirement. It puzzles me that there is no equivalent marine standard fro impact attenuation; I suspect it is coming. On the other hand, I have seen 4,500-pound test gear fail on falls of only 4 feet; the lanyard had no shock absorbing properties and the climber suffered some serious butt bruising from the harness. OSHA now prohibits the use of such static tethers.

My point? It is important that the user understand how the system components work together.
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Old 05-02-2011, 12:15   #13
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Lawyers!
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Old 05-02-2011, 13:02   #14
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Thanks to all of you for your input. Lots of good information.

Special thanks to Thinwater for your links. I hadn't considered that rock climbing gear would be more than adequate for sailing concerns. I had already decided before starting this thread that my jackline would be run down the center of the deck, and that tethers should not be long enough to allow getting in the pond. But I was thinking wire, not understanding the need for stretch to absorb shocks to the body parts.

What are anyone's thoughts on harness closures? I've already ruled out the plastic buckles that come on PFDs. I saw that one mfg uses a 2" surcingle in the front along with 2 d-rings. Are those type closures prone to opening at inopportune times?
Bill
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Old 05-02-2011, 13:23   #15
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Liability and Product Recalls

As others have noted, legal issues and liability are a big part of the cost. Also, because of fears of lawsuits, manufacturers of life safety equipment will often recall items at the slightest hint of any defect. If they had knowledge of a possible defect and didn't recall the items, and later someone was injured, the lawyers would eat them alive. The manufacturer must absorb the cost of replacing (or refunding purchase price) for a lot of units, most of which were probably just fine.

Making your own stuff is fine, so long as you know exactly what you are doing, and do it carefully.
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