Anchor snub lines

Delfin

Delfin

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My 30' 5/8 snub line has seen its useful life, so I've replaced it with a blatant rip off of a design copied from Evans Starzinger, with the addition of the Ultra rubber snubber. This is 25' of 5/8" octo plait with a sailor's thimble so it can be soft shackled to the chain. It is cow hitched to 3/8" Dyneema Dux which is long enough to go over the roller, providing great strength and chafe resistance. The rubber snubber provides the first line of energy absorption, followed by the octo plait. In a really serious blow, I will overlap this with 3/4" 3 strand nylon about 3 feet longer than this setup, so once that much stretch is induced, the 3/4" will take over and share the load.
 
Looking at the image your yacht is quite large. The snubber you describe is quite large diameter, maybe you can quantify how big the yacht is as on many yachts there will simply be no stretch with a snubber of that size.

At what sort of wind speed do you anticipate that the 3/4 inch will start to come into play?

Jonathan
 
Neeves said:
Looking at the image your yacht is quite large. The snubber you describe is quite large diameter, maybe you can quantify how big the yacht is as on many yachts there will simply be no stretch with a snubber of that size.

At what sort of wind speed do you anticipate that the 3/4 inch will start to come into play?

Jonathan
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Delfin weighs 65 tons, and with the crow's nest and masts probably has a fair amount of windage for a 55' boat. The 5/8" brait gives 10% stretch at around 20% of yield, or around 2,400 #, which I calculate will be generated with 50 knots of wind. Add wave action, and I would expect that at 40 knots or so the 3/4" would start to kick in. Most vessels in the 40' range would be advised to use no more than 3/8" to 1/2", in my opinion. The 5/8" 3 strand I have been using is pretty well stretched out now, measuring around 1/2" in diameter and quite stiff.
 
Neeves said:
Looking at the image your yacht is quite large. .....

Jonathan
Click to expand...
I thought the same as you ie that does not look like 25' of 5/8". The background suggests something large. Then I opened the web site in Delfin's signature ! Try it - amazing :)

@ Delfin - she is gorgeous but I am sure I am not the first to say that
 
Storyline,

I knew it was large and gorgeous. I thought maybe Delfin could spell it out for those not wanting to look at the website as when I'm offshore internet access is slow and expensive (so I tend not to delve) so its that one time when a picture costs more than 100 words - but who is counting!

Fortunately I have not seen the light - and think I'm still young enough to sail:)

Jonathan
 
Delfin said:
My 30' 5/8 snub line has seen its useful life, so I've replaced it with a blatant rip off of a design copied from Evans Starzinger, with the addition of the Ultra rubber snubber. This is 25' of 5/8" octo plait with a sailor's thimble so it can be soft shackled to the chain. It is cow hitched to 3/8" Dyneema Dux which is long enough to go over the roller, providing great strength and chafe resistance. The rubber snubber provides the first line of energy absorption, followed by the octo plait. In a really serious blow, I will overlap this with 3/4" 3 strand nylon about 3 feet longer than this setup, so once that much stretch is induced, the 3/4" will take over and share the load.
Click to expand...

Dyneema?
Great chafe resistance?

It looks like the rubber snubber is to go inboard of the bow roller?
judging by the big loop close to it, to go over a samson post?
 
Dyneema has great chafe and UV resistance. We are using Dyneema hollow tape to protect our snubbers from abrasion - seems to work a treat.

I'm not sure of the rubber snubber - it will have reached its maximum stretch before the chain is lifted off the seabed, but it is doing no harm. Great as a snubber when tied alongside (where the nylon lines might be too short).

Jonathan
 
Evans has used Dyneema as a convienent way of connecting to the chain, but when I looked at our 7 year old chain yesterday morning the surface is quite rough and I would be worried that the chain could cut through a soft shackle hence why i use a S/S chain shackle.

Pete
 
I am a bit confused as to the best length for a snubber. I have seen numerous references where considerable lengths are mentioned.

The system we use on Storyline is to set the anchor and adjust chain to get desired scope. Then we pull in around 3 metres of chain and attach some octoplait using a chain shackle. The octoplait is led over a second bow roller and made off. The chain is then lowered to form a slack loop and then secured on the foredeck by a chain hook. After we have lowered the chain, the attachment point of the snubber to chain is around the surface of the water. If it is very windy and the chain lifts off the sea bed the octoplait is extremely stretched but there is still a small amount of chain at the bow roller without load. Sorry if this sounds a bit convoluted but I hope you get the idea.

So, in short, our unstretched snubber is only about 3-5 metres or so. Is this long enough ?

Edit: just remembered I uploaded a video to YouTube showing the setup on a windy day (sorry Jonathan, it is bandwidth eater)www.youtube.com/watch?v=ysRMp7BM-po
 
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Storyline said:
So, in short, our unstretched snubber is only about 3-5 metres or so. Is this long enough ?
Click to expand...

Ours is the same (5m ish) and seems to work okay. If you ended up in a storm you could add another few meters and take it back to an aft cleat.

Pete
 
Storyline,

There is no rule on snubber length or size (diam). But most people who rely on a snubber would use something longer than yours, maybe 8m-10m. What you want is stretch (a short, thick snubber will not stretch under load a long, thin snubber might break (or be unmanageable)

A snubber is a bungy for a yacht. Think of the bungy jumper leaping into nothingness - when they reach the end of the bungy they feel very little, all the kinetic energy has been absorbed by the bungy as potential energy and they bounce up, and down etc.

You are trying to do the same thing with your snubber for your yacht. You want the load on the anchor to be absorbed by the snubber and none of that load to be transferred to the yacht - in practice that does not quite work, but you get the idea.

Snubbers should be considered as disposable. They degrade with constant cyclical load and when wet. They commonly fail without notice (well they make a big bang but most cannot detect weakness till they fail). Tie off your chain independently of the snubber - if the snubber fails you do not want the load on your windlass. But you might also consider that a snubber for 0-40knots might not be adequate for 30-50 knots (heaven forbid). Which is why Delfin has 2 snubbers.

40' yacht, 12mm octaplait, 8m-12m. 3 strand is just as good but less easy to handle. Bigger yacht, thicker cordage, but same length.

You do not want the chain hook, if you use a hook, to touch the seabed, they tend to fall off. To shorten (so it does not touch the seabed), run the snubber down the sidedeck to a midships horn cleat, or the stern cleat (use something to stop abrasion), old fire hose, sewn leather patches/tubes). Delfin is using a soft shackle instead of a chain hook - we have not tried soft shackles in this application but it seems to be enjoying much support.

We have a 6t x 38' cat. We use 14m of 11mm discarded lead climbing rope (it has to be retired by law here after a certain time etc and is thus free) which we run from the stern cleats up through the stanchion bases to turning blocks on the bow to a common chain hook. We carry a spare set of climbing rope snubbers on board - the idea of it being a consumable.

Jonathan

I'll check the youtube tomorrow, apology accepted:)
 
Neeves said:
Dyneema has great chafe and UV resistance. We are using Dyneema hollow tape to protect our snubbers from abrasion - seems to work a treat.

.....
Click to expand...

Dyneema is good on chafe when it's not highly loaded.
So hollow tape sleeve protecting a snubber would work well.
The dyneema is not carrying the load.
A 10mm dyneema snubber/(pendant? not sure of the correct term TBH) with 65T of Yacht bouncing around on the end of it is a very different set up.
High modulus ropes like dyneema do not share the load across the whole rope very well when bent.
That can magnify the effect of chafe, as some individual fibres are highly loaded, therefore more easily cut.
I would be concerned about the point load at the bow roller.
If the rubber thingy is one the deck, that will mean the rope at the bow roller is constantly moving, a recipe for chafe.
10mm seems small string for 65T?
 
Jonathan, thanks for the info. I think our octoplait is getting a bit aged now. It has been stretched many times in high winds at anchor. I will get a longer length when we do and try your system of running it down the side decks to a midships cleat to maximise the length that can be stretched.

As regards the chain hook. The one I use to attach the snubber is shown below. It does not go through the link obviously but crosses them. It cannot come undone easily. On deck then chain is attached with a claw type hook and I wrap a sail tie across so it cannot drop off if the bow is bouncing ! This hook is attached to an eye, spliced onto two lengths of three strand nylon which is taken to two cleats so there is no load on the windlass. The whole set up requires quite a bit of knitting with various lines used to make sure everything stays where it should.
View attachment 37422
Do not worry about the video, poorly edited and just a bit of fun but it does show the chain partly lifted and the whole system under considerable loading.
 
lw395 said:
Dyneema?
Great chafe resistance?

It looks like the rubber snubber is to go inboard of the bow roller?
judging by the big loop close to it, to go over a samson post?
Click to expand...
The Dyneema Dux is annealed, so there is no stretch at all. I read that riggers use ceramic knives to cut the stuff and they wear out after a dozen or so cuts, so I think it is pretty resistant to chafe. Yes, in my setup the rubber is inboard of the roller and there is enough room for it to stretch as much as it is going to between a 14" yachtsman cleat and a high density roller it goes over before joining up with the nylon snub line.
 
Neeves said:
Dyneema has great chafe and UV resistance. We are using Dyneema hollow tape to protect our snubbers from abrasion - seems to work a treat.

I'm not sure of the rubber snubber - it will have reached its maximum stretch before the chain is lifted off the seabed, but it is doing no harm. Great as a snubber when tied alongside (where the nylon lines might be too short).

Jonathan
Click to expand...
Yes, I'm not sure about the rubber snubber either, and it may be as you say, just doing no harm. My thought was that I would like to have a way to see when the line is loaded and this will be a ready gauge of that.
 
Pete7 said:
Evans has used Dyneema as a convienent way of connecting to the chain, but when I looked at our 7 year old chain yesterday morning the surface is quite rough and I would be worried that the chain could cut through a soft shackle hence why i use a S/S chain shackle.

Pete
Click to expand...
The thing that is nice about soft shackles is that they are so much stronger than steel. I believe that regular Dyneema or Amsteel that is not pre-stretched has more exposure to chafe, even though it is still pretty good. I use Plasma for soft shackles, although my chain is pretty smooth. Might be worth a try as they are superior in so many ways to the alternatives.
 
Storyline said:
I am a bit confused as to the best length for a snubber. I have seen numerous references where considerable lengths are mentioned.

The system we use on Storyline is to set the anchor and adjust chain to get desired scope. Then we pull in around 3 metres of chain and attach some octoplait using a chain shackle. The octoplait is led over a second bow roller and made off. The chain is then lowered to form a slack loop and then secured on the foredeck by a chain hook. After we have lowered the chain, the attachment point of the snubber to chain is around the surface of the water. If it is very windy and the chain lifts off the sea bed the octoplait is extremely stretched but there is still a small amount of chain at the bow roller without load. Sorry if this sounds a bit convoluted but I hope you get the idea.

So, in short, our unstretched snubber is only about 3-5 metres or so. Is this long enough ?

Edit: just remembered I uploaded a video to YouTube showing the setup on a windy day (sorry Jonathan, it is bandwidth eater)www.youtube.com/watch?v=ysRMp7BM-po
Click to expand...
I've read that 30' is usually about the minimum for a snub line. A shorter line will certainly help, but is mostly used for quieting the chain so you don't have to listen to it rumbling around.

Mr. Cox can comment, but from memory, the shock force on the ground tackle can be estimated by the formula Weight in tons * 100 * velocity squared divided by the distance the vessel can move before bringing the chain up short. That distance is determined by the travel to lift the chain off the bottom without a snub line, but with it is that value plus the stretch. The more stretch, the greater the effect of the divisor in the formula and the lower the force on the chain. So, with my setup, I might get 4 feet of stretch, which means if the shock load was going to be 10,000# without the snubber, it becomes 2500#. That's the rationale for a snub line - it amplifies the effectiveness of the anchor in almost all circumstances.
 
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