Choice of Material for Snubbers

[Andrew Troup]

I had Dockhead's solution as my chief bulwark against the dreaded scum.

If I ever got too cheesed off with the residue, I had a couple of backup ideas:

Saltwater jets, a couple each of high pressure, and high flow, emerging from fittings welded into the bow plating under the roller, aimed at the chain outboard of the roller, to get the bulk of the mud.


I also dreamed up a cassette which would clip over the chain outboard of the bow roller , with inwards facing brushes. Hollow fibreglass tubes disposed horizontally on either side would keep the cassette from coming inboard, while permitting the chain to grow sideways as the boat yawed. Saltwater piped through the tubes and into the brush heads.

The advantages of doing this is that my chain is going to run a long way aft, and would be dripping mud all the way if not dealt with first.

[Dockhead]

Originally Posted by Kenomac

Exactly what I was trying to explain in my previous post, only put into words in a more precise way. I'm obviously in 100% agreement with Jedi.

If what Nick is trying to say, and what you are agreeing with, is that it doesn't matter what material you make your snubber from, as long as you "use the right approach", please allow me to politely disagree.

Some materials are inherently better than other materials for certain purposes, irrespective of your "approach" or design of the system.

A snubber's purpose is to absorb energy. As nylon has 3 to 4 times the capacity to absorb energy as polyester does, it is hugely superior for this purpose, despite some disadvantages like vulnerability to chafe.

Sure, you can make the polyester snubber 3 to 4 times longer to compensate, but if you have room to make your snubber 3 to 4 times longer you will get even more benefit by using a thicker and longer nylon one. You simply can't get around the greater energy capacity of nylon.

We could use an analogy of choosing materials to make a mast out of. You can make a good mast out of different materials -- wood, steel, aluminium, carbon fiber come to mind. Each of these has different advantages and disadvantages, but all of these achieve a high degree of strength per unit of weight compared to most other materials, which is what makes them suitable (actually it's amazing how good wood is, by this measure). You can't make a mast, however, out of zinc. Well, but of course you can! The difference in strength between aluminium and zinc is about the same as the difference in energy absorption between nylon and polyester. So you just make it 3 to 4 times thicker, right? Sure, but now how heavy is it going to be!! Why would you bother? If you can tolerate that much more mass in your mast, why not make it out of an inherently better material, and make it 3 to 4 times stronger?

Likewise the choice between nylon and polyester for snubbers.

[Dockhead]

Originally Posted by Andrew Troup

I had Dockhead's solution as my chief bulwark against the dreaded scum.

If I ever got too cheesed off with the residue, I had a couple of backup ideas:

Saltwater jets, a couple each of high pressure, and high flow, emerging from fittings welded into the bow plating under the roller, aimed at the chain outboard of the roller, to get the bulk of the mud.


I also dreamed up a cassette which would clip over the chain outboard of the bow roller , with inwards facing brushes. Hollow fibreglass tubes disposed horizontally on either side would keep the cassette from coming inboard, while permitting the chain to grow sideways as the boat yawed. Saltwater piped through the tubes and into the brush heads.

The advantages of doing this is that my chain is going to run a long way aft, and would be dripping mud all the way if not dealt with first.

In my opinion, these engineering challenges are worth dealing with a thousand times over for the huge advantage in trim you will get. Using your chain as part of your ballast -- pure genius

I wouldn't worry too much about your naval pipe -- you can just direct a hose down it.

If I were you, I would rig up a normal anchor wash and just wash the chain off as it comes in just like everyone does. Then when you're done, just spray the hose down your naval pipe. The bilge pump will pump the water out and hopefully most of the scum.

You'll have to clean out the sump from time to time, which you can do with the chain out.

It won't stink and it won't contaminate your bilge. It will vent through the naval pipe.

I bet this will work fine

[Dockhead]

Originally Posted by JonJo

You are going to carry 550lb of 13mm chain, plus some 16mm chain on a 7t yacht? Depends on the anchor - but your ground tackle weight, windlass included, will be 5% of the yacht weight.

The idea is that his chain locker is low enough that the stored chain forms part of his ballast. With a ballast ratio of 40%, he will need 2.8 tons of ballast. Even 1000 pounds of chain will not be a problem -- that would be only 18% of his total ballast.

[Andrew Troup]

Jonjo

I don't want cordage anywhere near the bottom, thanks (sharp rocks are more than a match even for dyneema, in my estimation)

Anchor is 30kg

Hydraulic windlass, centrally located, serves triple duty as utility and salvage winch, so not overly concerned about the weight... (pumps and stored hydraulic power already required for other duties, so no penalty there)

I need internal ballast anyway (lifting keel); so why not use chain?
I'm a big fan of informal ballast, next best thing to a multihull .... especially ballast which is easy to jettison in a grounding or flooding situation (and, in the case of chain, easy to reload, when you come back for it)

Lugging around lots of formal ballast has always struck me as a bit of a shame, a slight stain on an otherwise lovely means of transportation (the monohulled sailing yacht).


Noelex

You say you see no merit in trying to "devise a system that will work without a snubber".

What I'm trying avoid to the maximum extent possible is being dependent on a snubber, certainly in sheltered waters. I don't mind rigging one for convenience, peace of mind, comfort, quiet.... I just would prefer not to be cornered into having to do so.

I've given an example where two experienced skippers in in such a situation both did without elastic snubbers, by choice.

I possibly forgot to mention they did so for a period of three days, with winds constantly at storm force, and up to 80 knots.

They chose not to fit snubbers, each for their own reasons. If the integrity of their anchor systems had been predicated on snubbers, as you seem to advocate, they might have come to grief.

(In the case of one boat it's actually not an option, due to the height of the bulwarks forrard, and the anchors' emergence from hawses set well down from the weather-deck)

I'll have relatively little windage, for a boat my size (Low freeboard, flush deck, short standing rig...) so I think that's a helpful factor.

I would also point out that any boat has to be able to fend for itself during the period while the anchor is being laid, and for as long as it takes to get a snubber on. The settling down period might entail changing scope to find a 'sweet spot', assessing whether the chosen location is in fact optimal, taking a nervous pee, swabbing vomit from the decks, checking Twitter and Facebook ;-) etc etc.

During this whole - correction - some of this time, the gear on a yacht which relied on elastic snubbing could be at risk.

Similarly on departure, the yacht has to manage after the snubber is removed.

- - - -

I don't expect to be flooded with crew for a number of reasons, so I would prefer to have the fewest "set piece" demands on my attention, and my time, when coming to anchor in bad conditions.

I haven't decided yet on the final details of my hydraulic windlass but my preference is to go for a design which can 'drive back', in other words, a potentially self-snubbing, and certainly self-protecting setup.

(A planetary gearbox or double-reduction wormbox, rather than a high ratio single-reduction wormbox)

The added weight and cost would to some extent be offset by the fact it would not need to be overrated for heavy shockloads to the extent of a conventional windlass.

Lacking a gearbox which can drive back, you're limited as to the conditions where you can safely fetch your anchor, if the boat is plunging.

Such a winch, with suitable cross-flow relief, would simply 'give' if snatch loads exceeded the set value.

I haven't mentioned this hitherto, as it seemed like a distraction on a forum like this, not being something which others would be likely to find either attractive or available.

I'm reasonably sanguine about the prospects it will work for me; but if I find myself in a situation where I need elastic snubbers, I'm fine with that, too ..... I'll have suitable line to hand, and they'll have less to do....

I'm not trying to win others over to my way; I'm just making the point that there is more than one way to skin the cat.

And it seems to me that some of the current conventional wisdom about snubbers could do with a bit of iconoclasm.

[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.

[Dockhead]

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.

Sure it does! Have you never had a deck wash? Check out the offerings from Jabsco and others.

You have a hose in our anchor locker, and a switch. As you haul the anchor, you spray off the chain BEFORE it touches your bow roller. All the crap flies off into the oggin. If you do it right, the chain will be almost perfectly clean before it ever touches your boat.

You know, not just boats with naval pipes have a problem with filthy chains. My previous boat did not have a sealed off chain locker; the locker communicated with the bilge. I had a deck wash and religiously washed off the chain, lest the stench drive everybody off!

Check it out: Groco C-60 Deck Wash Pump Kit

[JonJo]

Andrew

I'm almost speechless

I might suggest taking your 30kg Bruce out, anywhere with a sand bottom, and try it with 16mm chain. You might be disappointed. If you can do this and see the seabed it will help. I might suggest, this will anathema to you, you try a long length of a wire strop (whatever strength and length, 3m min, you feel is suitable). Consider the wire strop as a consumable and replace as soon as you have the slightest doubt. If you want weight, take more 13mm chain (but not 16mm chain).

Jonathan

[Kettlewell]

How about some thoughts concerning the real world? Sure, lots of heavy chain out in deep water might provide some cushioning, but who wants to be anchored out where you can deploy that mess in a storm? Myself, I'll be tucked up in some shallow hidey hole where the water will be six feet deep at low tide and yes I might be limited in my swinging room so I'll put out very long rodes, but several of them in different directions so my boat stays where I want it to. I have done this very thing through numerous hurricanes, tropical storms, and ordinary gales. The hidey hole is the place to be: less wind, no serious wave action, and usually better holding ground in nice deep mud. In situations like this I have often used as much as 200 feet or more of nylon, sometimes with no chain, connected to something like a Fortress. The stretch means a smooth ride, much less stress on the vessel and the anchor, and I don't sail around because I have out multiple anchors.

But, even the proponents of the massive chain in deep water theory should re-read Van Dorn's Oceanography and Seamanship and Alain Frayse, who both demonstrate pretty convincingly that a mixed rode--around 50:50 nylon and chain--provides the best holding power.

[s/v Jedi]

Originally Posted by Kettlewell

But, even the proponents of the massive chain in deep water theory should re-read Van Dorn's Oceanography and Seamanship and Alain Frayse, who both demonstrate pretty convincingly that a mixed rode--around 50:50 nylon and chain--provides the best holding power.

No they don't. Because it is not true. The best holding power is a full chain securely locked in a strong chain stopper, plus a 30' nylon snubber. We can argue a bit about the length and material of the snubber but is is silly to make it 50% of rode length.

When part of your rode is rope you always loose.. Has been demonstrated a zillion times, even here on CF in numerous threads.

[Kettlewell]

When part of your rode is rope you always loose.. Has been demonstrated a zillion times, even here on CF in numerous threads.

We're talking about holding power. If anchored in coral waters or some place where chafing the line is of concern, use all chain, but also use a very long snubber line to maximize holding power. Never broken a snubber line or anchor rope. But, I would have out multiple anchors in a survival storm in case something did let go.

[s/v Jedi]

Originally Posted by Kettlewell

We're talking about holding power. If anchored in coral waters or some place where chafing the line is of concern, use all chain, but also use a very long snubber line to maximize holding power. Never broken a snubber line or anchor rope. But, I would have out multiple anchors in a survival storm in case something did let go.

Yes, only my primary rode is all chain, couldn't carry the weight otherwise. But I completely disagree with your "very long snubber" theory, which IMHO will do more harm than good, while a regular snubber of the correct length would help enormously. More (stretch) is not always better...

Also, the fact that you never broke a rope rode, does not change anything about all the boats that have been lost due to their rope rodes breaking. When the water isn't crystal clear to the bottom, you never know what is there. why use rope when you also have chain, to save the chain?

When you never broke a snubber, it only means your snubbers are probably too thick, which explains why you need them to be so long before they work for you.

[Kettlewell]

For the record my usual snubber for daily use is 3/8" 3-strand nylon, with length varied depending on the conditions. For storms I might go up to 1/2", but that little 3/8" one has held in some pretty heavy conditions like a 56-knot chocosana squall in the San Blas without much shelter--probably had 30 feet out or so.

[sabray]

Remember that boat that beached in Polynesia last year? Lesson was good snubber with best of chafe protection. Back it up with chain stopper or similar secondary. I like the hybrid approach using Dyneema at the cleat and chafe points with the working absorption part outboard getting wet in the water.

[s/v Jedi]

Originally Posted by Kettlewell

For the record my usual snubber for daily use is 3/8" 3-strand nylon, with length varied depending on the conditions. For storms I might go up to 1/2", but that little 3/8" one has held in some pretty heavy conditions like a 56-knot chocosana squall in the San Blas without much shelter--probably had 30 feet out or so.

That sounds pretty good to me. When the 3/8" holds up through a storm, check for hard spots afterwards, which indicate near failure. You have to replace in that case.