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Sheesh, I've got Chef2Sail telling me I don't represent SN boaters in general, and you telling me I don't represent multihull cruisers. Some of us have multihulls for the comfort and space and livability, and not to buzz around at maximum speed in the bay on an nice day. 8-10kts is fast enough on a 6-day passage with 2 aboard. Slower and safer in crappy weather. We will never stuff a bow at 15kts cruising, and I bet you wouldn't either. That was just puffery.

Our cruising boats are reefed from the cockpit. Definitely no big deal, and much safer and easier. Why bring up the off-watch person from a valuable short sleep on a long passage to do something so fundamental and easy?

We don't have jacklines on our hardtop, and see no reason for that. Do monohulls have jacklines on their bimini's? Cabin top has nothing to access - the mast is accessed from the deck, and there is nothing on the boom necessary to access that isn't within inches of the gooseneck. Besides, sitting on the cabin top on a catamaran is relatively safe, and it would take tremendous force to move one there. The boat doesn't heel, doesn't generate high and long force vectors in any direction (lots of high, short vectors), and the cabin top is pretty much the center of rotation and pitch on a catamaran.

Why would I tie a 12' tether to a tree when I only use a 6' one on the boat? Why don't you actually do the math you claim for the conditions you claim? Anyone who has been on a boat will understand that a free drop fall on a 6' tether is not the same as a stumble or slide on a 6' tether - there is friction and counter rotation/inertia/momentum involved in those. You claim physics otherwise, so show your work.

Mark
 

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Sheesh, I've got Chef2Sail telling me I don't represent SN boaters in general, and you telling me I don't represent multihull cruisers. Some of us have multihulls for the comfort and space and livability, and not to buzz around at maximum speed in the bay on an nice day. 8-10kts is fast enough on a 6-day passage with 2 aboard. Slower and safer in crappy weather. We will never stuff a bow at 15kts cruising, and I bet you wouldn't either. That was just puffery.

No it was not. I didn't claim I was typical either.

Our cruising boats are reefed from the cockpit. Definitely no big deal, and much safer and easier. Why bring up the off-watch person from a valuable short sleep on a long passage to do something so fundamental and easy?

Didn't say I brought some one up. I also see no reason to limit a thread to a single style of sailing. Sometimes I sail slow and easy. Sometimes I do not.

The other obvious corollary to this line of reasoning is that jacklines are not needed at all, since everythin can be managed from the cockpit. There is some logic to that. Or PFDs. And most often, I don't use either.

We don't have jacklines on our hardtop, and see no reason for that. Do monohulls have jacklines on their bimini's? Cabin top has nothing to access - the mast is accessed from the deck, and there is nothing on the boom necessary to access that isn't within inches of the gooseneck. Besides, sitting on the cabin top on a catamaran is relatively safe, and it would take tremendous force to move one there. The boat doesn't heel, doesn't generate high and long force vectors in any direction (lots of high, short vectors), and the cabin top is pretty much the center of rotation and pitch on a catamaran.

Why would I tie a 12' tether to a tree when I only use a 6' one on the boat?

I didn't say a 12' tether. I said 12 feet of slack (your tether is on the center line; go 6' to windward and then stumble 6' past it = 12 feet. This is the worst case. But if you can do this with 6' of slack without bruises I'd be surprised, since I cannot.

Why don't you actually do the math you claim for the conditions you claim? Anyone who has been on a boat will understand that a free drop fall on a 6' tether is not the same as a stumble or slide on a 6' tether - there is friction and counter rotation/inertia/momentum involved in those. You claim physics otherwise, so show your work.

A 3' fall over the rail = 3x170#=610 ft-pounds.
A 3' fall takes about 0.4 seconds and reaches a final speed of about 8 knots.
I'm betting a fall across the deck, including a downhill stumble, can easily reach 8 knots. Most joggers average about 7 knots.

Adjust the assumptions as you see fit. The conclusion is only that they are comparable and that there is nothing magic about a vertical drop.


Mark
I'm not being critical. I'm not sayin' this is going to happen on your boat. I'm sayin' these are the forces that the World Sailing and ISO standards are based upon; catching a 6' drop of a grown man in wet gear. It is described in the ISO standard.
 

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We use webbing secured to a pad eye maybe (guessing) 6 ft. aft from the tip of our 2' sprit and pad eyes on each side just at the front of the cockpit. Can easily enter and exit the cockpit tied in. Cockpit has two pad eyes. Doesn't take long to put out and take in so we only have them out on passages. Always rinse them wit fresh water and dry when done. The webing does get slippery if stepped on.
 

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Discussion Starter #24
How does one secure 1" dacron webbing to a pad eye?

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Use one length of dacron webbing secured to aft pad eye at the starboard outside forward end of cockpit coaming.... run to the starboard bow cleat, thru and around and then across for deck to the port bow cleat, run thru and around and then back the an aft pad eye at the port outside forward end of cockpit coaming. Obviously a failure would render both lines useless as jack lines at least temporarily.
 

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truckers hitch so tension could be applied?
 

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How does one secure 1" dacron webbing to a pad eye?

Opinions please:
I would assume that you add an eye to the 1" webbing by having the eye professionally sown by a company who is certified to do that kind of structural sewing. Then you shackle the eye to a hardpoint. But that is part of why I like the dyneema line inside of a piece of webbing. The dyneema can be spliced with an eye that achieves most of its original strength. The webbing provided UV protection, and slip risk reduction. The webbing would need to stitched over the dyneema at the splices but that is okay in my mind since the webbing is not structural.

Jeff
 

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Discussion Starter #27
I am wondering if I can't use 2 D rings which tighten when the webbing is tension... I have something like this to tension my dodger bows. Getting rings sewn professionally is a bit of a pain but doable.
 

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I am wondering if I can't use 2 D rings which tighten when the webbing is tension... I have something like this to tension my dodger bows. Getting rings sewn professionally is a bit of a pain but doable.
You would have to be sure the buckle system would hold 5000 pounds. Although this can be done with buckles, I belive rings slip at MUCH lower values. it would require testing.

Both Practical Sailor and Sailrite have published sewing test results for DIY. The methods are specific but doable.
 

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How does one secure 1" dacron webbing to a pad eye?

Opinions please:

Use one length of dacron webbing secured to aft pad eye at the starboard outside forward end of cockpit coaming.... run to the starboard bow cleat, thru and around and then across for deck to the port bow cleat, run thru and around and then back the an aft pad eye at the port outside forward end of cockpit coaming. Obviously a failure would render both lines useless as jack lines at least temporarily.
One problem with a single length of webbing is that you double the stretch. Polyester is already arguably too stretchy (it's right on the edge for larger boats).

Additionally:
* If you have to cut one loose, now you have none.
* If you damage one (chafe?) both must be replaced.
 

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I would assume that you add an eye to the 1" webbing by having the eye professionally sown by a company who is certified to do that kind of structural sewing....
Jeff
Does this exist? In a practical sense, not really.

In a former life I manufactured climbing gear, and generally, we are talking self-certifications though ISO (6 sigma break testing program). That's it and many are not. Realistically, a sailmaker will do it. You will also need to source the correct webbing, which is a problem.

You are right that the Dyneema approach is probably best for DIYs. Fewer question marks and a solid finished product.
 

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I would assume that you add an eye to the 1" webbing by having the eye professionally sown by a company who is certified to do that kind of structural sewing....
Jeff
Does this exist? In a practical sense, not really.

In a former life I manufactured climbing gear, and generally, we are talking self-certifications though ISO (6 sigma break testing program). That's it and many are not. Realistically, a sailmaker will do it. You will also need to source the correct webbing, which is a problem.

You are right that the Dyneema approach is probably best for DIYs. Fewer question marks and a solid finished product.
I don't know whether its true that companies that are certified to do that kind of structural sewing exists, but I see 'OSHA' certified safety harnesses and tethers and so I have always assumed that there are companies that are certified to do structural stitching. That said, I have no idea if that is actually the case.

Jeff
 

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Discussion Starter #32 (Edited)
With all due respect... I do not need a system designed to 5000# load... static or dynamic. This WAY more than the force of a 200# human be tossed my boat motion from a wave.

Stretch? I how much stretch will a 25' line loaded when a person is tossed by a wave? Another nonsense concept. Actually a little shock absorption is not a bad idea!

I will keep the vinyl coated wire jack lines as back up.... so I am not concerned about being with no jack lines.
 

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With all due respect... I do not need a system designed to 5000# load... static or dynamic. This WAY more than the force of a 200# human be tossed my boat motion from a wave.

Stretch? I how much stretch will a 25' line loaded when a person is tossed by a wave? Another nonsense concept. Actually a little shock absorption is not a bad idea!

I will keep the vinyl coated wire jack lines as back up.... so I am not concerned about being with no jack lines.
* Safety Factor. Your anchor chain has a safety factor. Your shrouds have a safety factor. For safety critical applications a 10:1 safety factor is common, depending on the materials.
* Wear.
* Dynamic forces. If you cannot calculate it or measure, then you guess, I assume.
* Humans HAVE broken tethers on boats. You can google this. That is the reason the standards were updated to include a drop test. People died. And they weren't 200-pound humans. Most recently a skinny guy died on one of the Clipper Race boats (CV30--google it) because his tether parted; I believe new standards will result, since a clip meeting the last standard failed.

You have declared disrespect for ANSI, ISO, OSHA, ISAF/WS, and UIAA. OK.

I don't always or even often use tethers. But I would not want to have safety gear that was unreliable. That's worse than none, if you have fooled yourself into believing that it is good.
 

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Discussion Starter #34
I have Lirakis harnesses and they are very robust.

I am not contemplating any offshore work in the foreseeable future. And I don't know whether I will do new jack lines or not... but for the use contemplated... 1" dacron will suffice.

Thank you for your concern!
 

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Stretch? I how much stretch will a 25' line loaded when a person is tossed by a wave? Another nonsense concept. Actually a little shock absorption is not a bad idea!
Actually, stretch is one of the things I dislike about our current polyester webbing lines. When they are wet, they get very loose, and when they are in the sun, they get like guitar strings.

On our recent trip from Antigua to Georgia, I just rigged some old dyneema halyards as jacklines and liked that much better. I think I will be replacing the webbing with 1/4" dyneema in the future.

As for shock absorption, there will be enough of that just in the bowstring effect from the unsupported run, as well as the stretchy tether. In addition, one won't be coming up dead short on the jackline, they will also be sliding along it for some distance, which reduces the shock force. But personally, I think the less stretch in the static system the better - the dynamics will be providing the force reduction.

Mark
 

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Sure.
Tether onto a mast..padeye or side rail and you arent asking how much 'give' that hardware allows.

Good discussion...but north is still north.
 

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...Stretch? I how much stretch will a 25' line loaded when a person is tossed by a wave? Another nonsense concept. Actually a little shock absorption is not a bad ....
In testing, as much as 2 feet (PS Magazine). Or you could place a 25' section between two trees, without pretension, and step onto it. The static load will be on the order of 500 pounds and it will sag about 2 feet, depending on the product. Certainly body weight is reasonable. Try it. I have. Any slackliner or tight rope walker know of this. and look how many sailors, like ColeMj, have simply noticed it. Any engineer can check my math; it's high school physics and trig. Nothing complex in the static case.

Why belittle a concept you have not studied and have no personal knowledge of? You can test this for yourself.
 
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