Trying to Make a Better Anchor Snubber

[zeehag]

i snub my formosa 41 with a line with which i make a bridle by making a hitch around th echain and thru th e hawse on both sides of bow, to remove the stress from my sprit. this works just fine-i lost only one hook so far, so i wont use hardware any more-- the line with a hitch around the chain works quite nicely.
ther ear emany unprotected anchorages here on west coastal mex, so practicing is a good idea, until you find what makes you happy and sprit not endangered

[thinwater]

Originally Posted by RainDog

My reasoning goes like this:

1) The main goat of a snubber is to reduce shock loading on the chain and anchor
2) AYBC Horizontal load shows a 35' boat will put 900 lbs of pressure on a rode a 30 knots. 1800 lbs at 42 knots.
3) In winds of 20 knots or less the catenary of the chain will provide all the shock absorption needed
4) The snubber should start to provide shock absorption at 25 knots, and withstand occasional gusts of 50 knots without breaking.
5) Extrapolating from the AYBC table, 25 knots = 600 lbs and 50 knots = 2600
6) Worst case scenario is where the catenary is gone and then a wave or gust hits the boat. In this case I would like a few feet of stretch to absorb the shock of the wave without pulling the anchor out of the ground.
7) The ideal rope would have lots of stretch in the 600 - 900 lb range (where it will do almost all of its work) and 900 lbs should be 20% of breaking strength or below. Ideally 45 knots gusts would not push the rope over 50% of breaking strength.
8) The ideal rope has 900 lbs as 20% breaking strength and 2600 as 50%, so basically a 5200 lb breaking strength is ideal.
9) For New England Ropes 3-strand nylon, this would be 3/8 or 7/16.

Of course this rope must be protected from chafe where it exits the boat.

Close, but there is information missing and a few errors.

6 an 7 indicate a few feet of stretch at ... what length? If you want 4 feet of stretch at 20% load (regardless of the line size) you need about 35-40 feet (12% stretch).

The ABYC values are calculated based on exposed anchorage and waves. Wind force is about 4x less. Also, the moment you introduce rope the force goes down. The ABYC table will not help you much.

3 is correct. The ABYC tables are all wrong in that range if you have enough scope. If they were correct you could not pull in chain by hand!! I might say up to 15 knots, depending on the boat, depth and chain size (my chain is straight at 20 knots in shallow water).

The result--which would require a chart of force with the snubber is place--is that you are about 1 size heavy and that it should be about 30-40 feet long.

Thus, 3/8" is enough and 8mm climbing rope will work. I know several 40+ boats that use 10 mm climbing rope and cruise full-time.

The benefit is even less strain on the anchor, almost certainly never passing 1500 pounds. The way I see it, you've strengthened your ground tackle by softening it! Bravo.

[thinwater]

Just spent and interesting day testing tandem anchor rigs and snubbers for an up-coming article.

• Yes, the wind load is 3-5 times less than the ABYC table.
• Yes, I recorded values GREATER than the ABYC loads when I remove the snubber (since it is a catamaran, I used an Amsteel bridle) and anchored in shallow (4'6", all chain, 10:1 scope) water.

Honestly, it didn't look that different without the snubber, but anchors that had been set all afternoon immediately started dragging (I was using undersize anchors intentionally--testing and I want to observe the dynamic effects of surge).



Certainly shallow water was a major factor--it was the point of this specific testing--but interesting none the less. A fun way to spend an afternoon.

[carstenb]

æI used to use a rolling hitch for my snubber to anchor connnection, but now use a dyneema soft shackle.

If I have to release the snubber from the anchor - I simply cut the shackle.(never had to do this yet)

[Sandero]

I am not sure I understand this thread.... but I will chime in with my experience and solution. I use 5/16" chain, a CQR w/ a CL bow roller. and a Maxwell vertical windlass. My boat is a 36' fractional rig with a fairly high freeboard and a fin keel. The boat tends to sail around at anchor and I will use a steadying sail when the winds are consistently over 25 knots in the anchorage.

I made a snubbing line from 3/4" double braid nylon with rubber mooring compensator about 6 or 8' from the working end of the snubber. The snubber attaches to the chain with a ss reefing hook shackled to the line which has a small eye splice at the working end. The OAL length of the snubber is about 30' and includes a length of tubing for chafe protection which can be slid to "where its needed" and a lobster float a the bitter end.

I deploy the anchor with the required scope then hook the snubber to the chain and let out more chain which pulls the snubber over the bow roller as it goes "down". Once the compensator on the snubber is down and just above the water I tie the snubber off to one of the bow cleats leading it "around" the windlass drum to keep it fair (not chafing the aft end of the bow roller stem plates). I then let more chain out so the that the snubber line and the cleat are seeing the anchoring load.

The bow roller includes a "notch" and this pretty much keeps the snubber line centered and in place.

The snubber line is rated to exceed typical anchoring rode specs.

I have had no problems with chafe, setting the snubber or retrieving the chain/anchor. The retrieval begin with removing the slack from the chain aft or the snubber and then more to take out the catenary. This causes the boat to be pulled forward (make way) and the chain forms a new catenary which allows me to take in more chain until the snubber hook comes over the bow roller . I can then easily remove it and continue to retrieve the chain taking out the catenary and so forth.

One benefit of this system is the ability to know that the anchor is "set" properly by observing the compensator. As the loads increase AND if the anchor is well set the compensator will "untwist" a bit. If the anchor is dragging, the compensator will NOT untwist and there is not enough force (tension) in the anchor chain... simply the weight of the chain itself.

A second benefit of the mooring compensator is that it will add MORE stretch to compensate for "shock" loads from swells or wave action... which is the primary purpose of these compensators.

The stainless steel reefing hook has a rather long U shape and it's easy to hook through the chain and quite secure. I don't see it failing from anchor loads. Obviously the weakest component of the system would be the first to fail. I've used this same set up for a few decades and it is almost as new!

[James Diego]

Originally Posted by Sandero

I am not sure I understand this thread.... but I will chime in with my experience and solution. I use 5/16" chain, a CQR w/ a CL bow roller. and a Maxwell vertical windlass. My boat is a 36' fractional rig with a fairly high freeboard and a fin keel. The boat tends to sail around at anchor and I will use a steadying sail when the winds are consistently over 25 knots in the anchorage.

I made a snubbing line from 3/4" double braid nylon with rubber mooring compensator about 6 or 8' from the working end of the snubber. The snubber attaches to the chain with a ss reefing hook shackled to the line which has a small eye splice at the working end. The OAL length of the snubber is about 30' and includes a length of tubing for chafe protection which can be slid to "where its needed" and a lobster float a the bitter end.

I deploy the anchor with the required scope then hook the snubber to the chain and let out more chain which pulls the snubber over the bow roller as it goes "down". Once the compensator on the snubber is down and just above the water I tie the snubber off to one of the bow cleats leading it "around" the windlass drum to keep it fair (not chafing the aft end of the bow roller stem plates). I then let more chain out so the that the snubber line and the cleat are seeing the anchoring load.

The bow roller includes a "notch" and this pretty much keeps the snubber line centered and in place.

The snubber line is rated to exceed typical anchoring rode specs.

I have had no problems with chafe, setting the snubber or retrieving the chain/anchor. The retrieval begin with removing the slack from the chain aft or the snubber and then more to take out the catenary. This causes the boat to be pulled forward (make way) and the chain forms a new catenary which allows me to take in more chain until the snubber hook comes over the bow roller . I can then easily remove it and continue to retrieve the chain taking out the catenary and so forth.

One benefit of this system is the ability to know that the anchor is "set" properly by observing the compensator. As the loads increase AND if the anchor is well set the compensator will "untwist" a bit. If the anchor is dragging, the compensator will NOT untwist and there is not enough force (tension) in the anchor chain... simply the weight of the chain itself.

A second benefit of the mooring compensator is that it will add MORE stretch to compensate for "shock" loads from swells or wave action... which is the primary purpose of these compensators.

The stainless steel reefing hook has a rather long U shape and it's easy to hook through the chain and quite secure. I don't see it failing from anchor loads. Obviously the weakest component of the system would be the first to fail. I've used this same set up for a few decades and it is almost as new!

This is one good way to snob a boat! Depending upon the wind and swell, I may do the same!
My Dad always told me that there was more than one way to skin a cat; bobcat that is not a house tabby.
Thx for the suggestion!

[bobnlesley]

...more than one way to skin a cat...

This is true, but as with most things, there is a correct way to do it:
Cat_Skinning

ain't Google wonderful

[thinwater]

Originally Posted by Sandero

I am not sure I understand this thread.... but I will chime in with my experience and solution. I use 5/16" chain, a CQR w/ a CL bow roller. and a Maxwell vertical windlass. My boat is a 36' fractional rig with a fairly high freeboard and a fin keel. The boat tends to sail around at anchor and I will use a steadying sail when the winds are consistently over 25 knots in the anchorage.

I made a snubbing line from 3/4" double braid nylon with rubber mooring compensator about 6 or 8' from the working end of the snubber. The snubber attaches to the chain with a ss reefing hook shackled to the line which has a small eye splice at the working end. The OAL length of the snubber is about 30' and includes a length of tubing for chafe protection which can be slid to "where its needed" and a lobster float a the bitter end.

I deploy the anchor with the required scope then hook the snubber to the chain and let out more chain which pulls the snubber over the bow roller as it goes "down". Once the compensator on the snubber is down and just above the water I tie the snubber off to one of the bow cleats leading it "around" the windlass drum to keep it fair (not chafing the aft end of the bow roller stem plates). I then let more chain out so the that the snubber line and the cleat are seeing the anchoring load.

The bow roller includes a "notch" and this pretty much keeps the snubber line centered and in place.

The snubber line is rated to exceed typical anchoring rode specs.

I have had no problems with chafe, setting the snubber or retrieving the chain/anchor. The retrieval begin with removing the slack from the chain aft or the snubber and then more to take out the catenary. This causes the boat to be pulled forward (make way) and the chain forms a new catenary which allows me to take in more chain until the snubber hook comes over the bow roller . I can then easily remove it and continue to retrieve the chain taking out the catenary and so forth.

One benefit of this system is the ability to know that the anchor is "set" properly by observing the compensator. As the loads increase AND if the anchor is well set the compensator will "untwist" a bit. If the anchor is dragging, the compensator will NOT untwist and there is not enough force (tension) in the anchor chain... simply the weight of the chain itself.

A second benefit of the mooring compensator is that it will add MORE stretch to compensate for "shock" loads from swells or wave action... which is the primary purpose of these compensators.

The stainless steel reefing hook has a rather long U shape and it's easy to hook through the chain and quite secure. I don't see it failing from anchor loads. Obviously the weakest component of the system would be the first to fail. I've used this same set up for a few decades and it is almost as new!

In the November 2013b Practical Sailor, energy absorption readings were taken with both typical 40-foot nylon snubbers and rubber snubbers. The result was that rubber snubbers absorb an insignificant amount of energy by comparison to a longer snubber (<5%) and thus give only an illusion of effectiveness. Read the data.

[Sandero]

Originally Posted by thinwater

In the November 2013b Practical Sailor, energy absorption readings were taken with both typical 40-foot nylon snubbers and rubber snubbers. The result was that rubber snubbers absorb an insignificant amount of energy by comparison to a longer snubber (<5%) and thus give only an illusion of effectiveness. Read the data.

I didn't see the tests... but I can SEE the compensator lengthen when the load increases. I CAN'T see the line that is reaved (sp?) around it stretch. My line from chain to cleat is about 15' and the compensator can stretch several inches... perha9s 3. 5% of 15' is 9"... and I would be surprised of the line stretches 9" under a surge load. I am sure the line might stretch a bit as well.

I suppose if the compensators did nothing no one would buy and use them. No?

[thinwater]

Originally Posted by Sandero

I didn't see the tests... but I can SEE the compensator lengthen when the load increases. I CAN'T see the line that is reaved (sp?) around it stretch. My line from chain to cleat is about 15' and the compensator can stretch several inches... perha9s 3. 5% of 15' is 9"... and I would be surprised of the line stretches 9" under a surge load. I am sure the line might stretch a bit as well.

I suppose if the compensators did nothing no one would buy and use them. No?

9 inches is nothing. A 40' snubber might stretch 10-15% in rough weather, or 72 inches, before getting into serious fatigue loads.

The truth of rubber snubbers is that they have some value on short docklines (where more length is not available) and that is about it. As for the market, people buy Alga-X and copper bracelets, everyone believed the world was flat, and many still believe the world was made in 7 days. Sometimes the crowd is right, and sometimes the crowd simply does not know any better, which is why we have these discussions.

[Sandero]

Originally Posted by thinwater

9 inches is nothing. A 40' snubber might stretch 10-15% in rough weather, or 72 inches, before getting into serious fatigue loads.

The truth of rubber snubbers is that they have some value on short docklines (where more length is not available) and that is about it. As for the market, people buy Alga-X and copper bracelets, everyone believed the world was flat, and many still believe the world was made in 7 days. Sometimes the crowd is right, and sometimes the crowd simply does not know any better, which is why we have these discussions.

Fine and dandy... my snubber from chain to cleat is closer to 12- 15' than 40'...

[thinwater]

Originally Posted by Sandero

Fine and dandy... my snubber from chain to cleat is closer to 12- 15' than 40'...

15 feet of 3-strand nylon will stretch 12% and 20 % BS, or 21 inches. Typically a snubber is sized to operate at 20% BS in the worst storm, remembering that the force is several times lower than ABYC tables because of the snubber.

The worst problem with the rubber snubbers is that they are all done by about 500 pounds, just about where real storm loads start. But that is only the one they tested and certainly that varies. I do not know.

In my mind, short snubbers are for light winds, and long snubbers are for when it blows. Adding a rubber snubber to a 12-foot snubber is like putting sneakers on an elephant to make it quiet. It is simpler to use the right length snubber for the job.

Kind of like adding a bungee cord to a trolling line to cushion the strike. The mono does that. stretching dozens of feet.

[Sandero]

Thinwater...

O course you use the right tool for the job. 99% of my anchoring is not in storm conditions but in normal to light conditions in protected anchorages in the lee. Under these conditions my system works a charm... and when and if the winds and sea stat changes to storm conditions, I can set a second anchor and let out more scope of up to 40' on my snubbing line.

[Ocean Girl]

I can see what Thinwater is talking about. Watching our snubber with a nylon bungee in the middle, the bungee doesn't really do as well as a nice long snubber. But, we recently have hit a few anchorages where our snubber is too long. So I will make up a shorter snubber. Not sure about a bungee, the big black one we had snapped, the long slim one we have seems to not be very stretchy..?
Has anyone made a bungee by splicing/weaving multiple small bungees? This would be for light applications, just the usual summer squall >30 knots, on a short snubber.
Thanks
E

[rgesner]

As Jonathon Neeves describes in Practical Sailor, you can extend a nylon or dynamic climbing rope bridle the full length of the boat for increased shock absorption:

"We attach our bridle to the stern cleats and run up the side decks, through the stanchion bases, to a dedicated turning block we attached to each bow. Our snubbers are about 12m, so we have little hanging in the water. Monos can usually make some arrangement to get a snubber up the side decks and to a chain hook (or whatever) but watch for areas of potential abrasion. We leave our bridle attached permanently.
We attach each arm of our bridle to a common shackle which is then attached to the chain hook, cast stainless type. We used to use 3 strand and splice but now use 11mm lead climbing rope - which is unspliceable. Artificial climbing walls must discard climbing rope after a specific time or if suffering a major fall. We have been given lengths of retired ropes, ask they need to get rid of it, the lengths are 13m -15m perfect for a snubber. Climbing rope for the lead climber is specifically made to stretch so as to minimise injury to the climber it has slightly less strength than the equivalent 3 strand or multi plait but more elasticity. It will be too small for a 50' yacht."