Rolling Hitch on Snubber

[Dockhead]

Originally Posted by foolishsailor

That seems to me to be the main issue and why I don't use a rolling hitch on chain. The line is pulled at over 90degrees where it exits and is under dynamic tensioning. A recipe for trouble.

Over 90 degrees is not a sharp bend inside a knot. The humble rolling hitch is actually one of the strongest knots in existence (if not the most secure) because the angles are quite mild compared to most other knots. I've never seen a failure of a nylon snubber at the knot -- they usually break where they're led over the rail or through the anchor roller, or in the middle.

No knot which is capable of securing a rope to a chain and pulling it in the same direction will have an initial bend of less then 90 degrees -- by definition. If you're worried about this, then Andrew Troup's strap is the way to go (but recognizing that his strap also bends at more than 90 degrees ).

I'm not visualizing how a sheet bend -- or any bend -- could be used to attach rope to chain, unless you are making a loop in the chain. The sheet bend is one of my favorites in my pretty limited repertoire of knots, because of its extreme convenience, but I am conscious that it is neither strong nor secure. The best is the double fisherman's bend, which is apparently the world's strongest bend. This from a fascinating practical test of different knots in PBO recently.

[colemj]

Originally Posted by Dockhead

I do have a chain hook on board -- one which looks just like Nick's. I don't use it with my snubbers for the reasons stated. It is shackled -- with sturdy Wichard forged shackles -- to a length of heavy stainless chain which is shackled to my inner forestay chain plate, and I take all load off my windlass with it. This is only one of many good ways to do this, but one way or another, your chain needs to be attached to your boat in a strong manner.

Do yourself a favor and replace that stopper chain with spectra line. A chain hook like Nick's attached to a spectra line connected to a midline cleat is our chain stopper.

Mark

[Kettlewell]

The only funky thing I started doing lately was hanging a block under my bowsprit for the snubber. I did it for silence, as the line sliding around in the deck chock was noisy in a lot of wind.

It's had the advantage of absorbing most of the movement and having the line at the chock be relatively motionless, but it's only practical if you have a bowsprit.

Or you can rig a snubber from a bow eye down near the waterline, and it stays silent and water cooled too. The lower angle means you need less chain out.

[Dockhead]

Originally Posted by colemj

Do yourself a favor and replace that stopper chain with spectra line. A chain hook like Nick's attached to a spectra line connected to a midline cleat is our chain stopper.

Mark

That seems like a good idea. I'll think about that as a solution. Then a serrated rescue knife hung on the chain locker bulkhead would make a quick getaway pretty easy.

Do you keep a winch handle handy to release your windlass clutch?

[foolishsailor]

The issue is not within the knot but how fair the ends lead when leaving a knot. As I edited my post the rolling hitch was designed back before synthetics created zero stretch line.

Also I do use a system similar to Andrew, mainly because I like to let the strop run over my bow rollers easily.

[Jim Cate]

G'Day all,

Very interesting discussion for sure...

I'm surprised that I seem to be the only one using a normal s/s chain hook that routinely brings the hook up and down over the roller. This of course allows me to do the hooking and unhooking in relative comfort standing back near the windlass. My chain is 10 mm and the hook is spliced on to 16 mm double braid nylon. Every now and then it will come up at an unusual angle and get stopped entering the channel of the roller. Stopping the retrieval and letting out a couple of feet of chain and trying again has always solved this problem. The snubber is then left in the roller next to the chain. LIttle chafe is observed. My roller is homemade, about 4 inches wide and has stepped grooves to match the chain.

Second thing: How much stretch is really necessary in a snubber? Once there is enough to absorb shock loading, why do you need more? Eventually the full load must come on to the anchor. The idea of a snubber stretching tens of feet seems ludicrous to me. I typically veer out some 5 to 10 metres of my rather heavy line. I have observed this line stretching perhaps a half metre (estimated by watching the diminution of the hanging chain loop) when absorbing the energy of sheering about in heavy gusts or pitching in seas. Has seemed to be adequate... I wonder if a stretchier line would be better or just add to the problem by "rubber banding"?

Cheers,

Jim

[colemj]

Originally Posted by s/v Jedi

Octoplait is better than 3-strand; it is the eye splice that keeps me away from it. I hate to spend that much time on it for piece that I consider chafing gear. I did an eye splice in my 1.25" octoplait secondary anchor rode and it took me the better part of a day... within a year I had to cut it off during an emergency

Like everything else, practice solves that problem. You did better than me on your first splice. I think I spent 3 days and 15' of rope learning my first octoplait eye splice. Now I can put them in almost as fast as I can 3-strand.

Mark

[colemj]

Originally Posted by Dockhead

Do you keep a winch handle handy to release your windlass clutch?

Our windlass uses a special handle tool for its clutch, which is kept in the anchor locker. But our windlass goes in both directions, so I would normally use the controls for slacking chain. If everything is hitting the fan, Michele would be at the helm with the engines running.

Mark

[colemj]

Originally Posted by Jim Cate

I'm surprised that I seem to be the only one using a normal s/s chain hook that routinely brings the hook up and down over the roller. This of course allows me to do the hooking and unhooking in relative comfort standing back near the windlass.

You are not the only one. We don't have a problem running the chain hook (two hooks for us) over our roller and onto the deck. Likewise, Nick and a couple others also stated they had no problem.

I haven't made much of this point because the geometry, type and orientation of rollers and gear can vary so much boat to boat, that others could quite well have problems.

Mark

[foolishsailor]

Originally Posted by Dockhead

. If you're worried about this, then Andrew Troup's strap is the way to go (but recognizing that his strap also bends at more than 90 degrees )

No, it doesn't. The lines lead out of the stop almost fair. It is not the line within the knot that is relevant it is how the "bitter ends" of the knot leave the knot. A prusik knot tied to the end of a chain link will lead nearly fair from the knot itself.

Edit: just realised that the strop as it exits the sheet bend or whatever knot you tie the actual snubber too is effectively a 90 degree angle.

Ugh, I live to be wrong I guess.

Still prefer a strop over hook as my roller won't let a hook through...

[estarzinger]

for those of you using webbing loops . . . specifically what sort of webbing are you using? I have some 1" tubular climbing webbing on board . . . it is more than strong enough, but is a 'soft' construction and I suspect would crunch quite tightly if loaded by a sheet bend and it would not be much easier to untie than on a rope sling. I can try it, but wondered if there was some other sort of webbing that would be much easier in the untying phase?

Parts of this debate is similar to the preventer thread . . . in that there are two quite different failure modes (with snubbers: shock loads & chafe, with preventers: mast failure & preventer/boom failure) and a system can be oriented/designed toward one mode or the other. I personally have designed toward what I consider empirically the most common failure (chafe and preventer system failure) but I can certainly understand the thinking to design toward the less common but more serious failure mode (shock loads and mast failure). In our discussion/debate I think it's important to simply realize there ARE two failure modes on both systems and there IS a system design trade-off and people CAN intelligently choose two paths in both. Once you choose a primary path, you can then work around the edges of the system design to minimize the 'other' failure mode.

So, just for instance in snubbers, if you go with nylon to minimize shock loads, you then want to go heavy on chafe protection; but if you go with Dacron to minimize chafe, you want to go long and thin to maximize stretch. For any given piece of nylon line, you could in fact choose a size and length of Dacron line that had exactly the same stretch.

[Kettlewell]

How much stretch is really necessary in a snubber? Once there is enough to absorb shock loading, why do you need more? Eventually the full load must come on to the anchor. The idea of a snubber stretching tens of feet seems ludicrous to me.

A long stretchy bit of nylon dramatically reduces the peak loads on the anchor and boat, and improves anchor holding. It's like jumping off a bridge either attached with a bungie cord or with a chain--I know which I would prefer. Peak loads are much lower with the bungie. Anchor Testing and Rode Loads was an interesting recent article that discussed this somewhat.

[foolishsailor]

I have used both spectra cored braid and tubing but will be going to dyneema when I am next down to my boat. I am moving to dyneema as it is so bloody strong you can size it to your need based on your desire for abrasion resistance life versus breaking strength.

I am a full convert as we use it exclusively on my race boat in high abrasion environment with the smallest diameter we can get away with and it is shocking how well it works.

However my main reason for not using a hook is I can't pull the hook over my bow roller and prefer to rig it on the deck out of pure laziness.

[sabray]

How do you tour to the webbing?

[estarzinger]

^^

One solution I thought about was a spectra cord loop with a klemheist around the chain, and rather than a sheet bend to the snubber line, using a tylaska trigger shackle. I am quite sure that will work well. The tylaska will always open easily and it will go over the bow roller, but I have been trying to find an 'all textile' solution that avoids having a $200 piece of stainless in the water.