Choice of Material for Snubbers

[Delfin]

Originally Posted by Andrew Troup

Dockhead

Your solution to the mud is admirably simple, and fine as far as it goes, but it does nothing to prevent the on-deck trail from the bow to the mast.

If, as you say you will have hydraulics you might consider a hi pressure wash down pump, aka pressure washer. Besides easily blasting off whatever comes up with the anchor including kelp, it is a great way to keep the boat very clean between washings. I consider mine one of the most useful pieces of equipment aboard, although you rarely see them. The pump measures about 10" square so they are hardly a space burden.

[Kettlewell]

I can't recall if anyone in this thread says they are using something like Brait, Octoplait, or Megabraid for a snubber--one of the 8-plait, or 12-plait nylon lines. Some of them aren't available in small enough sizes for me, but for those of you using 1/2-inch or 5/8-inch snubbers it seems like one of those braids would be the ultimate for the stretchy part.

One thing the marine ropes have going for them, as opposed to climbing ropes and others, is the marine ropes apparently have coatings on the fibers that drastically reduce water aborption and loss of strength, and also reduce friction within the rope when things are wet. I don't know what they do to it, but I have found that New England Ropes 3-strand nylon lasts and lasts and lasts, and never stiffens up.

[estarzinger]

Originally Posted by JonJo

Evans,

>>If I have this correct your have transferred from a nylon (climbing rope) snubber to a dacron snubber.

No, my current snubbers are dyneema from cleat to just past bow roller and then nylon (climbing line although i will also test some nylon 8brait when i get my hands on a piece) to the dyneema soft shackle chain attachments.

This system design has excellent chafe prevention (with the dyneema) and excellent stretch (with the nylon), and I think the only major remaining design question is which nylon construction offers the greatest resistance to heat damage. I can find no good data on that, and may have to construct a cycle test next winter to figure it out.

Interestingly NER, who I copied this idea from, suggest nylon double braid construction for the nylon portion. I am going to ask an engineer i know there why, as I would have thought that would be the last choice of construction (least stretch and most heat retention). But I suspect they have a good reason, which will be valuable to understand.

This dyneema/nylon hybrid design had zero failures thru hurricane sandy and Irene. I am told it was the only major design/system to have zero failures.

[Dockhead]

Originally Posted by Kettlewell

I can't recall if anyone in this thread says they are using something like Brait, Octoplait, or Megabraid for a snubber--one of the 8-plait, or 12-plait nylon lines. Some of them aren't available in small enough sizes for me, but for those of you using 1/2-inch or 5/8-inch snubbers it seems like one of those braids would be the ultimate for the stretchy part.

One thing the marine ropes have going for them, as opposed to climbing ropes and others, is the marine ropes apparently have coatings on the fibers that drastically reduce water aborption and loss of strength, and also reduce friction within the rope when things are wet. I don't know what they do to it, but I have found that New England Ropes 3-strand nylon lasts and lasts and lasts, and never stiffens up.

I have been using octo for years. Fantastic stuff. It's also superior for rope rode.

[s/v Jedi]

Originally Posted by Dockhead

I have been using octo for years. Fantastic stuff. It's also superior for rope rode.

I use Yale 1.25" octoplait (polyester I think!) for my secondary anchor rode but ordinary nylon 3-strand for my snubbers as it's quicker to splice and works as good as I wish.

[Dockhead]

Originally Posted by s/v Jedi

I use Yale 1.25" octoplait (polyester I think!) for my secondary anchor rode but ordinary nylon 3-strand for my snubbers as it's quicker to splice and works as good as I wish.

My secondary rode is also polyester.

3 strand works fine for a snubber, but octo will give more energy absorption if you need it. I still can't splice octo, though - as far as I can tell, it requires witchcraft. :-)

[estarzinger]

Originally Posted by Dockhead

To continue the thought about pitching: . . . .
-- we're concerned only about the angular velocity.

No, actually you should only be concerned with the velocity vector component pointed at the anchor. With 5:1 scope that's 11 degrees above horizontal. Relatively little of the angular 'pitch velocity' is in that resultant vector direction (because pitching is primarily a vertical velocity). A velocity component at a higher angle than that (the chain scope angle) is really only lifting the chain (note: yes, I am simplifying here).

Pitching does introduce a significant fatigue cycle.

Since the waves have forward velocity, their impact will drive the boat back and will impart some amount of aft velocity (in the direction of the anchor), peaking as the bow climbs up the wave. But that is captured (mostly) by the x/y velocity measurement.

If you have really serious waves, there can be a breaking crest 'jet' at the top, which can have quite high direct force transfer (the 'jet will have velocity in double digit knots and weight about a ton per sqm). This is a significant issue on para-anchors. But it is not a boat velocity issue.

[estarzinger]

Just one other comment from the mooring experience base . . . . regarding bridles and back up snubbers (on monohulls) . . . . the mooring experience says that two equal length snubbers (a typical bridle) will fail well before one shorter (primary) and one longer (back up) snubber.

[colemj]

Originally Posted by Kettlewell

I can't recall if anyone in this thread says they are using something like Brait, Octoplait, or Megabraid for a snubber--one of the 8-plait, or 12-plait nylon lines. Some of them aren't available in small enough sizes for me, but for those of you using 1/2-inch or 5/8-inch snubbers it seems like one of those braids would be the ultimate for the stretchy part.

Brait is what we use for our bridle (snubber for you monos). Started out with double braid, but that proved too "jerky", went to 3-strand which was good but got stiff and cumbersome, then moved to brait which was just right...

Mark

[Dockhead]

Originally Posted by estarzinger

No, actually you should only be concerned with the velocity vector component pointed at the anchor. With 5:1 scope that's 11 degrees above horizontal. Relatively little of the angular 'pitch velocity' is in that resultant vector direction (because pitching is primarily a vertical velocity). A velocity component at a higher angle than that (the chain scope angle) is really only lifting the chain (note: yes, I am simplifying here).

Pitching does introduce a significant fatigue cycle.

Since the waves have forward velocity, their impact will drive the boat back and will impart some amount of aft velocity (in the direction of the anchor), peaking as the bow climbs up the wave. But that is captured (mostly) by the x/y velocity measurement.

If you have really serious waves, there can be a breaking crest 'jet' at the top, which can have quite high direct force transfer (the 'jet will have velocity in double digit knots and weight about a ton per sqm). This is a significant issue on para-anchors. But it is not a boat velocity issue.

I stand corrected! Wow, that`s a good analysis.

[colemj]

Originally Posted by estarzinger

Just one other comment from the mooring experience base . . . . regarding bridles and back up snubbers (on monohulls) . . . . the mooring experience says that two equal length snubbers (a typical bridle) will fail well before one shorter (primary) and one longer (back up) snubber.

Is there reasoning behind this? A bridle is about the only option multis have.

Mark

[s/v Jedi]

Originally Posted by colemj

Is there reasoning behind this? A bridle is about the only option multis have.

Mark

You can back up with a longer bridle... also makes you practice the octo splice a bit more so you will have no problems when doing them for me

[cfarrar]

I'm not sure about an 8-plait snubber. I find that Octo is susceptible to the strands being "picked" on anything sharp or hard. When using my Octo rode (on the rare occasions I deploy all my chain) I attach a sacrificial (3-strand) snubber to take the abuse.

[DumnMad]

Thanks guys. You've conducted a good seminar here today.

[JonJo]

Originally Posted by Kettlewell

One thing the marine ropes have going for them, as opposed to climbing ropes and others, is the marine ropes apparently have coatings on the fibers that drastically reduce water aborption and loss of strength, and also reduce friction within the rope when things are wet. I don't know what they do to it, but I have found that New England Ropes 3-strand nylon lasts and lasts and lasts, and never stiffens up.

Climbing ropes can also be supplied with coatings to reduce any degradation, or reduction in performance, by water during use. Of course if you are a cheapskate like me and get your rope free from a climbing wall it will not be coated (as it seldom rains indoors).

I have seen no test results on the longevity of these coatings nor have I seen any independent tests on how good they are. The manufacturers point out that a wet rope is weaker, they point out that some of their ropes are treated (to make them more water resistant) - but omit to say (technically) what affect the coating actually has, or how long it lasts. Coated ropes cost more, of course.

Water reduces ultimate breaking strength but how it impacts ultimate breaking strength at low cyclic loading (a marine anchor snubber) is another area I can find no technical detail. The only testing of cyclic loading is on climbing rope, which also has the greatest elasticity, how cyclic loading impacts 3 strand or 8 or 12 plait (wet or dry) no idea.

Choice, in the absence of any data, must depends on what is available of a size to suit the individual, how important it is to splice and whether one wants to prioritise longevity (probably 3ply or 8/12 plait) or elasticity (probably climbing rope - limited size range) but this latter can be overcome with a longer snubber. Dacron can also come into the mix alongside nylon.

But it does seem there is some room to do a whole range of testing (including can a snubber be too long).

Jonathan