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Closet Powerboater
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Discussion Starter #1
I'm an all chain kind of guy, so I use an anchor snubber. I also like attaching the snubber to a waterline fitting to reduce the needed scope. The bridle I used on my Formosa was short and rudimentary.

What I've got planned for the new boat is something super stretchy involging 3 strand nylon line, snubbers, and a sewn in length of shock cord as described in Brion Toss' book The Rigger's Apprentice.

Question is, what's the ideal length? I figure that as an absolute minimum, it must easily reach the chain at the roller from the waterline fitting. As an absolute maximum it shouldn't be long enough to get in the prop were it to be dragged along underway (it's happened to me before). So that makes it somewhere between 8ft and 30ft. As long as possible seems like a good idea for shock absorption, but if I anchor in the shallows, it could touch the bottom which may not be a good idea.

Any thoughts on the ideal length?

MedSailor
 

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What do you want it to do?
* Take to load off the windlass and roller? Short will do.
* Absorb wave impact? How big a wave?
* How deep is the water (shallows take longer snubbers, since there is less rode)?
* Mono or cat? I'm assuming mono.
* Hold the bow into the wind? 2 legs?

Personally, I like them longish as the ride is smoother (cat, shallow water). But others feel differently, and it depends on the use.

I'm not sure I like waterline fittings; can't adjust it and the snubber is in place under way (?). But I like the scope increase.
 

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Master Mariner
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Our snub line is about 25' of one inch three strand nylon line. I have seen it stretched down to perhaps 13/16ths or less in extreme circumstances, but it has never broken. I've replaced the thimble once, but that's it, in three years of constant anchoring. At times we will shorten the scope in very shallow water, but not otherwise.
We have two and have, a couple of times, added the second one when the wind exceeds 45 knots sustained, but as a back up, not to share the load. I have found on our vessel that the single snub line to the starboard bow chock and cleat minimizes sailing on the anchor.
You might want to consider that if your snub is attached at the water line, you cannot inspect it or change it's length. Caught out on a lee shore anchorage in building seas, you might be better served with your snub coming on deck? The stem fitting snub attachment is mostly used on steel vessels where a failure of the fitting is unlikely.
 

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Closet Powerboater
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Discussion Starter #4
Thanks for the input so far.

PDQAltair:

The intended purpose is to absorb shock from waves, to both improve holding and smooth the ride at anchor. It is also to take the load off the windlass, and to move the point of attachment to the waterline at the bow to reduce the needed scope.

Wave size will be all waves encountered at anchor between here and the end of our trip many years from now.

Monohull Nauticat 40.

Capta:

I'm not too worried about the fitting. It's the fitting that the bobstay attaches to, and the bobstay is under more tension than the forestay of the boat, so she's a pretty solid fitting. I share some of your concern about inspection because of it's location, but my bigger issue is that it can't be lengthened if one needs to put out more scope. I've thought about running a block to the deck where I could adjust the length of the snubber from the deck, but that seems a little exotic and chafe becomes more of an issue. .

I really like having the lower attachment point though as it lowers my amount of rode needed by 30ft due to the decrease in freeboard. Also, there are no chafe issues with it being attached there whereas anywhere on deck or on the bow can chafe. My intention is to use some bronze thimbles with shoulders that I found for 3/4" line.

MedSailor
 

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BJV
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We have a bow sprit and so use a bridal system on our 41' ketch
Anchor hook on a 3' three strand line to a clevis, where two 20' lines act as a bridal up to our bow fairleads to the sampson post. Adjust length based on conditions with about 10' on calm nights and let out to full length when wond and waves pick up.
 

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Thanks for the input so far.

PDQAltair:

The intended purpose is to absorb shock from waves, to both improve holding and smooth the ride at anchor. It is also to take the load off the windlass, and to move the point of attachment to the waterline at the bow to reduce the needed scope.

Wave size will be all waves encountered at anchor between here and the end of our trip many years from now.

Monohull Nauticat 40.

Then the 25' suggested sounds reasonable.

Bear in mind that with heavy use, if the line is thin enough to absorb shock (3/4" is too much--Starzinger uses 7/16" climbing rope, perhaps the minimum, on a light ~ 45" boat. 5/8" is more perhaps appropriate to you) it will last only ~ 6-12 months before retirement due to loss of elasticity. If you make it strong enough to last for years, it won't be absorbing shock.
 

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Ideal length for me is so the snubber doesnt hit the water. Barnacles can grow in it cutting the fibre.


Mark
 

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Closet Powerboater
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Discussion Starter #8
Then the 25' suggested sounds reasonable.

Bear in mind that with heavy use, if the line is thin enough to absorb shock (3/4" is too much--Starzinger uses 7/16" climbing rope, perhaps the minimum, on a light ~ 45" boat. 5/8" is more perhaps appropriate to you) it will last only ~ 6-12 months before retirement due to loss of elasticity. If you make it strong enough to last for years, it won't be absorbing shock.
Interesting thoughts on loss of elasticity. Also a possible good use for climbing rope. Any idea if climbing rope keeps its elasticity through thousands of repeated cycles? I've been told that tge rope needs a lot of time to recover between pulls and a follow up fall can be harder because the fibers haven't recovered. I'd love to know more about this because climbing rope is much more elastic than anything else out there.

As for size I want it strong but also stretchy. Thats the idea behind the brion toss trick. Basically you unlay 3 strand rope and insert shock cord in the middle and whip it in place. The three strand tries to compress the shock cord as it is pulled.

Does nylon itself loose much elasticity with use? If so there are a lot of folks on mixed rodes that still think they have a lot of elasticity in the system.

Mark, good point about growth. Not a problem in my area but later in higher fouling areas it likely will be.

Medsailor
 

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Interesting thoughts on loss of elasticity. Also a possible good use for climbing rope. Any idea if climbing rope keeps its elasticity through thousands of repeated cycles? I've been told that tge rope needs a lot of time to recover between pulls and a follow up fall can be harder because the fibers haven't recovered. I'd love to know more about this because climbing rope is much more elastic than anything else out there.

As for size I want it strong but also stretchy. Thats the idea behind the brion toss trick. Basically you unlay 3 strand rope and insert shock cord in the middle and whip it in place. The three strand tries to compress the shock cord as it is pulled.

Does nylon itself loose much elasticity with use? If so there are a lot of folks on mixed rodes that still think they have a lot of elasticity in the system.

Mark, good point about growth. Not a problem in my area but later in higher fouling areas it likely will be.

Medsailor
Regarding use of climbing rope for a snubber, please look at Starzinger's blog rather than have me translate it. Yes, there is relaxation time, but that has to do with much higher speed falls than you are considering.

Elasticity vs. time has been studied re. deep water moorings. It depends on the load, but perhaps 200,000 moderate load cycles, which works out to about very 20 stormy days. Light wind and smooth water days don't count. But there are many variables.

I can't see growth being an issue if you move around every few days; they'll die when it is hauled up. Perhaps have a short snubber if you are going to stay in a well protected harbor for a month. If it is not well protected, you need the longer snubber. And remember, the snubber is not what is really holding the boat; the chain should be secured through a good stopper, so that if the snubber breaks you are still secured. Rig another and ease out some rode.

The Brian Toss idea may work. Don't know how many have tried it. Granted he is a talented rigger; for most of us the result would likely be unreliable. And I don't see the point; just use a longer rope snubber and you will have a more fatigue resistant construction with less fuss.

As for folks using mixed rode, different case. They are using larger diameter (snubbers are smaller than the rode) and should not be operating in the load range where this matters. Additionally, with mostly nylon rode, normally they have almost too much elasticity, allowing the boat to surge (I've had both sorts on the same boat--there is a happy medium). Some claim polyester makes a better fiber rode, and I believe that (much less chafe, moderate elasticity).

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Another concern with waterline attachment is adjustment. What do you do when it is roaring and you need to move or add scope? You can't ease it. You can't even reach it to cut it. Many use this system--particularly charter cats--but this limitation bothers me a bit. Something to consider; make sure you have a way to clear it under load.
 
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