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SanderO 05-07-2019 09:28 AM

Jack Lines
 
My jack lines are heavy coat wire... attached to the bow cleat with a large shackle. They need to be cleaned but the are structurally sound...

I am thinking of replacing with webbing or high something else.

Would they be tied to the cleat?
What size and grade material?
Removed when not sailing?

Suggestions please.

Minnewaska 05-07-2019 09:46 AM

Re: Jack Lines
 
Good upgrade. Hard to know if coated wire is corroded underneath. No shock absorption either.

I use commercial purpose made jacklines, made of webbing. Helps to twist them a couple of times, as you install, so they are easier to pick up and attach your tether. Lying wet and flat on the deck is hard to grab, especially if you are wearing gloves.

We tie ours to the stern and bow cleats, as well as a hard point on our coachroof, to keep the lines as far from the side as possible. I believe the number one trick is to keep the line/tether from allowing you to ever reach over the lifeline. We accomplish this along about 70% of the run and focus on those sections that have fewer handholds, such as the foredeck.

We only install them for passages that warrant it, in our opinion. Very rough weather or anytime overnight. I might leave them on for a week or two at a time, when I'm away, as I'm more inclined to take what Mother Nature dishes out. For weekends, I don't typically volunteer to head off in conditions I might need them for. If I were singlhanded, I'd leave them on permanently.

pdqaltair 05-07-2019 09:56 AM

Re: Jack Lines
 
Jacklines. Jack lines are utility ropes used to last things down and the like. Different meaning.

The bow and stern cleats really are not the best locations, they are just convenient. In fact, it is better if the jacklines end 4-5 feet from the bow or stern so that you cannot go over (4-5 feet still allows you to stand) at the bow).

Material is a tough question, because there is no one answer. I've researched this, including impact testing, and published articles. Larger boats need higher strength and lower stretch than smaller boats. Webbing is nice, but if I can't leave them rigged because of UV, that makes them basically useless IMO (not there when I need them). I like covered Dyneema or oversized rope (if you can keep them out from underfoot--easy on multihulls, depends on the boat) because I can leave these rigged. There is nothing wrong with stainless cable, but I would skip the cover, go over strength (because they do not stretch), and make certain the tethers have some stretch (which is where you really need it anyway).

A few hardpoints at work stations (mast, helm) are good too.

olson34 05-07-2019 10:13 AM

Re: Jack Lines
 
Agree with pd....
we have pad eyes in the cockpit, at helm and just outside the companionway. Webbing jack lines that only see the sun for about a month a year. You do have to really tighten and retighten those lines after wetting and drying, and it takes some extra wraps when you make a 'cleat hitch' to make the ends really secure from creep.

SanderO 05-07-2019 10:57 AM

Re: Jack Lines
 
This for deck only on mono hull. cockpit is set up already.

Minnewaska 05-07-2019 11:09 AM

Re: Jack Lines
 
UV is a good point. Iíve never left them installed long enough for it to matter.

Iím not a fan of rope running underfoot. Iíve done my share of slipping upon it, as it rolls. If out of the way, it may work better.

Scandium 05-07-2019 11:12 AM

Re: Jack Lines
 
You clip yourself into the bow cleat with a ~4-6ft tether? So if you fall off you'll be hanging from it underneath the bow of the boat, or along the side? How do you get back up? Are you alone, or do you rely on someone stopping the boat and pulling you up? BoatUS did a test and I believe they found you have about 60-90 sec to stop before drowning becomes a risk, so I would make sure this is all clear and set up properly.

Jeff_H 05-07-2019 11:12 AM

Re: Jack Lines
 
I am of the low-stretch school of thought with the thought that low stretch is likely to keep me on board and with the hope that the length of the line combined with catenary action should result in more than enough stretch to cushion the fall and prevent internal injuries. My current jacklines are kevlar cored 9mm line run from a hardpoint on the foredeck to my aft stern cleats. I understand PD's point about the hardpoint being forward of the stern cleat, but I have thought that the aft most position might give me a chance reaching the stern ladder or the loops of line that I hang off the quarters to give me something to grab onto and put a foot into. The current jackline sits against the intersection of the cabin and coaming with the deck so is minimally a tripping hazard.

If I was taking my boat offshore, I would want more hardpoints in the cockpit and would change to something like dyneema inside a webbing cover. I would want the jacklines fixed to hardpoints rather than cleats. The webbing is only there as a sun screen and further minimize the tripping hazzard.

Jeff

Minnewaska 05-07-2019 11:38 AM

Re: Jack Lines
 
My cockpit system consists of a homemade bridle that I afix around the base of the cockpit table. It has multiple attach points for each occupant, it provides full access to the helm and cockpit but physically prevents travel beyond the lifelines. I puked at midnight on last summers Gulf of Maine crossing and my head barely made it over the lifeline. Success. Sort of.

pdqaltair 05-07-2019 04:09 PM

Re: Jack Lines
 
Quote:

Originally Posted by Minnewaska (Post 2051600528)
UV is a good point. Iíve never left them installed long enough for it to matter.

Iím not a fan of rope running underfoot. Iíve done my share of slipping upon it, as it rolls. If out of the way, it may work better.

^^ Absolutely right.

I've had two boats where this was not an issue: On the cat I could run it along the cabin chime, well off the deck and usable as a hand line, like a railing. On the tri, it runs over the inner tramp lacing; stepping on lacing is a bad idea to start with (there are holes--small enough to meet standards, but still poor footing).

But no, neither rope nor cable should be run on deck. only webbing.

pdqaltair 05-07-2019 04:17 PM

Re: Jack Lines
 
Quote:

Originally Posted by Scandium (Post 2051600530)
You clip yourself into the bow cleat with a ~4-6ft tether? So if you fall off you'll be hanging from it underneath the bow of the boat, or along the side? How do you get back up? Are you alone, or do you rely on someone stopping the boat and pulling you up? BoatUS did a test and I believe they found you have about 60-90 sec to stop before drowning becomes a risk, so I would make sure this is all clear and set up properly.

I hope you did not take my statement that way, because I meant the reverse.

You clip to a jackline that ends 4-5 feet aft of the bow, to prevent falling forward. You can still reach the bow, of course, because sometimes you must. I then clip down low to a toe rail or railing, if I need to work at the bow. I would be sitting--it's hard to fall over a lifeline that way. I've done this with the short leg doubled; even with the bow playing submarine, you can't fall off.

Going to the bow in heavy weather is never pretty. Scooting rather than walking is often smart. There is no stand-up plan that is mistake proof.

paulk 05-07-2019 04:17 PM

Re: Jack Lines
 
We have webbing that replaced SS wires. The webbing is nice because it doesn't roll underfoot if you step on it. We rig them between a padeye on the foredeck and mooring cleats on the stern quarters. (We don't need the mooring cleats for anything else when we need jacklines rigged.) If they're polyester UV is not going to damage them much.

pdqaltair 05-07-2019 04:20 PM

Re: Jack Lines
 
On outboard powered boats there is an additional reason to end the jacklines well forward of the transom; if you fall of the back you could be chopped to death. I'd rather drown.

No, you are not likely to go off the back when the engine is running, but it could happen.

colemj 05-07-2019 05:30 PM

Re: Jack Lines
 
What about dyneema webbing?

We currently have a set of West Marine 1" polyester webbing jacklines. I've never been happy with them, but jacklines on a catamaran are not as critical (don't jump on that - I'll explain later). 1" polyester webbing has a breaking strength of ~1,500lbs. This is the same as 7/64" dyneema line, which is spiderweb-thin. There would be no issue with rolling under foot, and no issue with being in the way. The only issue might be actually finding it to clip on to.

Dyneema line has become very cheap. Particularly if you buy cutoffs, which is just fine for most jackline applications. I just bought 60' of 1/4" Endura 12 for $15.

So who here would feel comfortable with 7/64" jacklines? They are the same strength as 1" polyester webbing and won't roll under foot. For you metric fans, that is 2.5mm.

Jacklines on a catamaran only need to keep one from reaching over the edge. They will never really take a giant load, and one has so many other options for obtaining stability while stumbling around - bimini frame, grab rails, shrouds, simply falling toward the centerline, sitting down on the tramp, etc.

Our jacklines get run up the center of the boat, which puts them 8-10' from the edge of the boat. If one did fall, they would not reach the edge of the boat, so the jackline would only experience the load of the person slipping, and not a load of a person being dragged through the water.

The most dangerous part of going on deck in most catamarans is that short distance from the front of the cockpit to the front of the cabin house. This short side deck is usually wider than that on a monohull, and has the shroud located right there. Once forward of the cabin house, one is on a very wide deck, and even sunken in a trampoline. So there is ~8-10' between cockpit and solid bimini grab holds and the expanse of the foredeck that one must pay particular attention to. Luckily, the shroud is located in the middle of this distance, so that provides a good hand hold. Again, the jackline is 8-10' away from the edge, so there is no danger of going overboard.

For this short zone, we rig lines from the stern cleats, up to the shrouds at chest/middle height, and down to a bow cleat. These lines can be made tight, and don't interfere with the sails. This is serves as a high lifeline. Now, there is a nice hand hold outboard to use, and if one did somehow fall outboard, they would likely fall onto this lifeline.

As for the cockpit, we have nothing, and don't wear tethers or vests there. I'm not sure how we could even fall out of the cockpit - it is sunken, wide, and deep. We would have to be lifted 5' in the air and thrown 12-20' sideways to even come close to leaving the cockpit.

Mark

colemj 05-07-2019 05:43 PM

Re: Jack Lines
 
Definitely remove the jacklines when not needed. UV isn't even the real driver - they are just in the way and dirt magnets otherwise. Devise your system so that they are easily installed, removed, and stored. Webbing is great for this - rolls up into a tiny package.

If you determine that jacklines are needed whenever you are sailing, then leaving them in place seems more reasonable, though.

We think of jacklines as passage-making gear. Day sailing, or even a short over-night in planned weather we don't rig them because we are rarely on deck, and both of us can easily be up and active if there was any need to go on deck. However, for us all lines are led to the cockpit, so going on deck is a rare thing anyway. If we do need to be on deck, it is usually for a reason that being clipped to a jackline is a valuable thing.

Mark

RegisteredUser 05-07-2019 05:45 PM

To me...jacklines can double as handhold lines...rigged chicken/safety bars.
I would like to be able to wrap an arm and/or leg around and hug it tight..if ever needed.
Top of my boat is an obstacle course...even at quiet anchorage...:)
If rough...scoot crawl..always weight down low..and hold the fk on to sumping..
I run a 1/2" line to mast then to bow cleat..is off the deck and easy aid when moving

I love dyneema but id want simething large enough i can squeeze the juice out of

bristol299bob 05-07-2019 05:51 PM

Re: Jack Lines
 
I rig webbing pulled tight as I can between dedicated hard points a foot back from the bow and 2 ft from the stern. After reading this thread I'll consider moving them even further from each end.

I also have 3 hardpoints in the cockpit to directly connect tethers.

But I have come to rely on fixed tethers at workstations ... I have a fixed tether at the mast and one near the bow. The tether at the mast is quite comfortable (chest height) and easy to get steady and get the job done. The one on the bow ... well ... I'm secure, but thats all I can say. its the bow of a monohull afterall. For me, working at the bow of a monohull in conditions that require a tether is just not pleasant no matter how you slice it.

pdqaltair 05-07-2019 07:14 PM

Re: Jack Lines
 
Quote:

Originally Posted by colemj (Post 2051600580)
What about dyneema webbing?

We currently have a set of West Marine 1" polyester webbing jacklines. I've never been happy with them, but jacklines on a catamaran are not as critical (don't jump on that - I'll explain later). 1" polyester webbing has a breaking strength of ~1,500lbs. This is the same as 7/64" dyneema line, which is spiderweb-thin. There would be no issue with rolling under foot, and no issue with being in the way. The only issue might be actually finding it to clip on to.

1" polyester webbing suit able for jacklines is actually about 6500 pounds, once an allowance for stitching is made. World Sailing and ISO say 5000 pounds finished. (You can confirm by reading WS Offshore rule)


Dyneema line has become very cheap. Particularly if you buy cutoffs, which is just fine for most jackline applications. I just bought 60' of 1/4" Endura 12 for $15.

So who here would feel comfortable with 7/64" jacklines? They are the same strength as 1" polyester webbing and won't roll under foot. For you metric fans, that is 2.5mm.

Not 7/64, probably 1/4" to meet strength requirement. That is what APS does for the ones they make. In part this is because Dyneema does NOT stretch, making for higher forces than polyester. Additionally, the fittings will need to match the Dyneema line, about 8000 pounds.

Jacklines on a catamaran only need to keep one from reaching over the edge. They will never really take a giant load, and one has so many other options for obtaining stability while stumbling around - bimini frame, grab rails, shrouds, simply falling toward the centerline, sitting down on the tramp, etc.

Yes, they can. Stuff wave at 15 knots and see. Also, the wide cabin top and hard top are great places to fall from. I've been launched from the cabin top and it can be a LONG way (I had a PDQ before the tri in my avitar).

Our jacklines get run up the center of the boat, which puts them 8-10' from the edge of the boat. If one did fall, they would not reach the edge of the boat, so the jackline would only experience the load of the person slipping, and not a load of a person being dragged through the water.

The load of a person running/stumbling 12 feet considerably exceeds that of a 6' vertical fall. You can do the math. I've had harder stops on multis than any mono.

The most dangerous part of going on deck in most catamarans is that short distance from the front of the cockpit to the front of the cabin house. This short side deck is usually wider than that on a monohull, and has the shroud located right there. Once forward of the cabin house, one is on a very wide deck, and even sunken in a trampoline. So there is ~8-10' between cockpit and solid bimini grab holds and the expanse of the foredeck that one must pay particular attention to. Luckily, the shroud is located in the middle of this distance, so that provides a good hand hold. Again, the jackline is 8-10' away from the edge, so there is no danger of going overboard.

For this short zone, we rig lines from the stern cleats, up to the shrouds at chest/middle height, and down to a bow cleat. These lines can be made tight, and don't interfere with the sails. This is serves as a high lifeline. Now, there is a nice hand hold outboard to use, and if one did somehow fall outboard, they would likely fall onto this lifeline.

As for the cockpit, we have nothing, and don't wear tethers or vests there. I'm not sure how we could even fall out of the cockpit - it is sunken, wide, and deep. We would have to be lifted 5' in the air and thrown 12-20' sideways to even come close to leaving the cockpit.

Mark

Just sayin', watch the assumptions.

colemj 05-07-2019 08:32 PM

Re: Jack Lines
 
Quote:

Originally Posted by pdqaltair (Post 2051600602)
Just sayin', watch the assumptions.

OK, so I made a few assumptions. To whit:

1. We won't ever be stuffing our bows at 15kts while anyone is on deck. Seriously, do you think people cruise this way?

2. I won't be on our hardtop, or even our cabin top in serious weather. Why do you think someone will climb onto the hardtop in inclement weather? What reasonable person even rigs jacklines on their hardtop? If for whatever reason going up there was necessary, then the procedure would be a specific one, with a specific plan, and not rely on a general jackline.

3. 7/64" dyneema may be a bit light, but even 1/4" will not roll under foot. Still a viable alternative.

I disagree that a person taking a prat fall on a wide deck, or having one foot slip, or simply jerking quickly aside a few inches, considerably exceeds a dead fall of 6' coming short on a tether. This is probably easily shown through simple physics, but most people's experience is sufficient. I won't do the math, since I'm not the one questioning it. BTW, nobody is running to the foredeck. At least not anymore on a catamaran than a monohull, and nobody will be doing it for 12' on a catamaran, since the tether is 6'.

I'm with JeffH in thinking that stretch works against one in this case. As for end fittings, of course they need to be matched with the expected load. Otherwise, it is like cautioning against connecting anchor to chain with shoelaces - pretty much a waste of breath.

But what about dyneema webbing? Doesn't seem too expensive, won't roll underfoot, good UV and chafe resistance, and stronger than polyester.

Mark

pdqaltair 05-07-2019 09:17 PM

Re: Jack Lines
 
a. I've always sailed that fast. Some of it cruising, some just for fun. Heck, my PDQ would do double digits pretty easy, and my tri is faster. Why else have a multihull?
b. Each boat reefed from the mast. No big deal.
c. Yes, there were always hard points or jacklines on the cabin top. That's just good design, since a jam related to the mast or boom is always a possibility. I fact, rigged vertical jacklines, something like shrouds. Really nice when working on the hard top. No big deal.
d. Take your tether, tie it to a tree with 12 feet of slack, and run as though you tripped. It will hurt, a lot. It's just safety gear. If you don't actually take a worst case trip or stuff anything will work.

I like the idea of Dyneema. There are slackline companies that market limited amounts of Dyneema webbing. Try balancnecommunitee.com.

colemj 05-07-2019 09:47 PM

Re: Jack Lines
 
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

pdqaltair 05-07-2019 11:21 PM

Re: Jack Lines
 
Quote:

Originally Posted by colemj (Post 2051600614)
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.

dadio917 05-08-2019 12:45 AM

Re: Jack Lines
 
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.

SanderO 05-08-2019 10:20 AM

Re: Jack Lines
 
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.

Minnewaska 05-08-2019 10:32 AM

Re: Jack Lines
 
truckers hitch so tension could be applied?

Jeff_H 05-08-2019 10:36 AM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600704)
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

SanderO 05-08-2019 11:17 AM

Re: Jack Lines
 
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.

pdqaltair 05-08-2019 03:38 PM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600724)
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.

pdqaltair 05-08-2019 03:42 PM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600704)
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.

pdqaltair 05-08-2019 03:48 PM

Re: Jack Lines
 
Quote:

Originally Posted by Jeff_H (Post 2051600716)
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.

Jeff_H 05-08-2019 04:22 PM

Re: Jack Lines
 
Quote:

Originally Posted by Jeff_H (Post 2051600716)
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

Quote:

Originally Posted by pdqaltair (Post 2051600788)
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

SanderO 05-08-2019 04:35 PM

Re: Jack Lines
 
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.

pdqaltair 05-08-2019 06:29 PM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600800)
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.

SanderO 05-08-2019 06:40 PM

Re: Jack Lines
 
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!

colemj 05-08-2019 08:00 PM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600800)
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

RegisteredUser 05-08-2019 08:12 PM

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.

pdqaltair 05-08-2019 08:32 PM

Re: Jack Lines
 
Quote:

Originally Posted by SanderO (Post 2051600800)
...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.

RegisteredUser 05-08-2019 08:37 PM

How bout dem Braves?

Springs wound tight....


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