What size for snubber?

[Bash]

I use a simple chain hook, and have never had one fail me. These days I splice the line directly to the eye without bothering with a thimble.

[Andrew Troup]

I use a kleimheist, too, and it works really well, but I make it with a short, sacrificial webbing sling (endless loop). I carry a bunch of these, premade, using a beer knot to make them reliably endless. They're handy all over the place, eg providing lashing points to slotted toerails, etc etc.

This way of attaching a snubber seems to me to have several advantages: it passes over the bow roller more easily (because the flat webbing barely increases the outside dimensions of the chain, and does it progressively) -- which means you can apply it and remove it without hanging over the bow; it is arguably less chafe-prone than any rope can be, because of the greatly increased surface area in contact; and the fact that it provides a loop makes it quick, easy and strong to attach the snubber to it using a sheetbend (or a double sheetbend in really bad conditions).

In my tests, rope holds better to a tape loop than to a rope loop, in a sheetbend.

If you have to get the chain rode back into the locker in an emergency, a sharp serrated knife can saw through tape quicker than dyneema rope, and the remnants can safely be left to pass around the gypsy without jamming there or in the navel pipe, which cannot be said for rope.

[estarzinger]

Originally Posted by Jim Cate

So, I'd say that the windlass manufacturers warnings are a bit overblown... but as always, YMMV.

Jim, a few years ago, I had a conversation with some Lewmar windless engineers about this, and their concern is not 'breaking' the windless - as in breaking a gear or shaft - but that leaving a load on will deform the seals and bearings around the vertical shaft thus later allowing water to drip thru and causing corrosion.

Its interesting that people have had such different experience with snubbers - some breaking quite large ones and others using quite small ones reliably for years (like me). Can anyone suggest why there is such a range of experience?

Hawk is not small in the range of boats and I (at least) have sailed in the same waters where others are breaking big snubbers. My guess would have to be smoothness of roller/fairleads and chafe protection OR appetite for protected or less protected anchorages (I certainty favor more protected anchorages).

[noelex 77]

Originally Posted by estarzinger

others using quite small ones reliably for years (like me). Can anyone suggest why there is such a range of experience?

I would really like a bit more stretch. Our boats are a similar size what sized snubber do you use?

[estarzinger]

Originally Posted by noelex 77

I would really like a bit more stretch. Our boats are a similar size what sized snubber do you use?

I have used 10mm climbing line for years (with a regular chain hook). The only damage to it ever was in Hurricane Lenny, when I was less careful with chafe than I should have been, and the cover to the line chafed but the core was still solid.

Mentioned/photo in the thread above I have been experimenting this summer with a different 'all on deck' configuration using 5/16" (8mm) line (essentially doubled, as two legs share the load).

Less than once a year, with an extra big blow forecast, I get out a bigger bridle snubber with 5/8" line.

[noelex 77]

Thanks.

That is a lot thinner, but it means I should at least be able to go down a size or two safely.

[jcapo]

Originally Posted by estarzinger

Its interesting that people have had such different experience with snubbers - some breaking quite large ones and others using quite small ones reliably for years (like me). Can anyone suggest why there is such a range of experience?

I think it has to do with open fetch vs. protected anchorages.

My chocks will eat 3/4" nylon line with exhaust hose, the nylon reinforced hose, or fire hose for chafe gear in 25+ winds and the bow pitching badly in open anchorage waves. With the same wind in a protected anchorage and little bow pitching I'm fine.

I bought 15" cleats using 1/2" fasteners that I will add on both sides of the bow and not use the deck cleats and chocks when anchoring.

I have been attaching my nylon snubbers using double braid polyester with loops on each end. A prusik knot at the chain and the nylon snubber tied to the other polyester loop with a bowline. I'm switching to Amsteel for the nylon to chain attachment like others have mentioned. The double braid polyester does chafe a bit.

John

[Andrew Troup]

Evans

You ask "Can anyone suggest why there is such a range of experience?"

I suppose one possibility is that some people might be using a judicious span of chain to set a hard limit to the extension of the snubber

Others might belong to the school who let a 'big loop of chain' hang between the attachment points for the snubber.
I've heard this advocated to secure a chain hook against uncoupling.
If the snubber is fitted further down the chain (nearer the anchor) it might also be perceived as a way of achieving a slight improvement in catenary (a quasi-kellet)

In the latter case, there's clearly no upper limit to the load seen by the snubber.

[kbudd]

A related question: I have a windlass that I am going to install this winter. My rode will be about 50 ft of 3/8 chain and the rest nylon. I understand how if you have an all chain rode, the snubber takes the anchor load to a cleat. But how does one take the load off the windlass when you have a rope rode. Do you take the rode completely off the windlass and cleat it or do you use some sort of snubber that grabs the line?

[cfarrar]

kbudd: either way you want to take the load off the windlass. You can simply cleat belay your nylon rode on a cleat, or, if you're worried about it chafing, you can use a snubber on the rope rode just like you do on the chain. See this thread for the different techniques to hitch a snubber to your nylon rode.

[Jim Cate]

Originally Posted by estarzinger

Jim, a few years ago, I had a conversation with some Lewmar windless engineers about this, and their concern is not 'breaking' the windless - as in breaking a gear or shaft - but that leaving a load on will deform the seals and bearings around the vertical shaft thus later allowing water to drip thru and causing corrosion.

G'Day Evans,

Thanks for that! A very telling bit of info, since that is exactly what I experienced. The windlass continued to work normally as far as I could tell, but a couple of years later (more or less) it failed from internal corrosion. Dang! That earlier VWC 1200 didn't even have a seal on the main vertical shaft bearing which was a simple bronze bushing. I can't know if the leakage that lead to failure was due to distortion of the bearing or simply bad design, but it is surely suggestive. One notes that when I bought a replacement it did incorporate a seal in that area, although not one that would be harmed by side loads.

Do note that in this case we're not talking about "leaving the load" on the windlass as in habitually not using a snubber, but rather what happens when the snubber fails suddenly. And I'm still amazed that one can drive a 56:1 worm gear backwards!

Cheers,

Jim

[Andrew Troup]

Originally Posted by Jim Cate

.... I'm still amazed that one can drive a 56:1 worm gear backwards!

I'm amazed too.
I design such things for a living and although I know it's theoretically possible, it's very rare indeed to do it from a standing start, at that ratio. It must be well engineered in terms of fits and finishes.
The crucial factor is the helix angle, but for a worm of that ratio, it's invariably a single start, so there's a limited ability for the designer to vary the angle.

I've had to provide a guarantee that a 56:1 worm I designed would NOT run back (in a situation where it was carrying tons of sawn lumber). It was fitted with an automatic brake but the wormbox was expected to provide a backup line of defence: to ensure that it couldn't, I used plain bearings (cast iron) on the wormwheel, as I knew that (at least in theory, and now confirmed by your experience in practice) it could conceivably run back with rolling element bearings.

Generally there has to be some vibration to provide a hydrodynamic wedge of lubricant into the mesh to get things going from a standing start. I suppose in the conditions described your rig would have been pumping, the stays (and a roller heasail if you have one) would have been shedding vortices and humming a bit?

I've heard of a couple of other instances of runback of a windlass, in one case the motor acting as a generator blew the fusible links! But neither person knew what the ratio was, so thanks for that data point.

[Jim Cate]

G'Day Andrew,

Thanks for that feedback... very interesting. The gearbox has a bronze wheel and a s/s worm. Worm is supported by ball bearings, the wheel by fairly generous bronze bushes, and the whole thing is immersed in hypoid oil. In the instance reported I was below when the snubber parted and the runback began. The chain was feeding out at an estimated 30 ft/min (about half of the normal powered down speed) and seemed ready to continue until the bitter end. Being somewhat flustered, I simply jammed the pawl into place and the process stopped.

I can't remember much about vibration at the moment! But as you suggest, there would have been lots of potential sources. Incidentally, what sort of vibration would be needed to start things up? Cyclical changes in tension on the rode, simple "rattling about" of the whole structure or what?

At any rate, when I know that harsh anchoring conditions are likely I now add a backup snubber to take the load should the primary one part.

Cheers,

Jim

[Andrew Troup]

Jim

Vibration from either the rode or the deck could do the trick to defeat the metal-to-metal contact at the loaded tooth, and get things rolling.

The vibration would probably need a significant component at a critical frequency to get the thing resonating.

I'm even more amazed than I was if the wormwheel does not have rolling element bearings - are you certain they're plain bronze?

[noelex 77]

Originally Posted by Jim Cate

. In the instance reported I was below when the snubber parted and the runback began. The chain was feeding out at an estimated 30 ft/min (about half of the normal powered down speed) and seemed ready to continue until the bitter end. Being somewhat flustered, I simply jammed the pawl into place and the process stopped.

I am very surprised as well.
I understood the worm drive was self locking and could not be reversed. Presumably this applies at least up to the rated load of the winch. There is no other locking mechanism on most designs.

Are you sure it was not just the clutch that was allowing the gypsy to spin?