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MJH · 05-08-2021, 11:59

Quote:

Originally Posted by skipmac

Helping son in law set up a mooring for his 56' sport fisherman. He normally keeps it at a dock but the dock has no pilings to hold the boat off in a wind so he's setting up the mooring for bad weather.

The block, chain and ball are pretty straightforward but some questions about the pendant. Since this will be for nasty conditions he wants to go with something as bulletproof as possible and due to the size and weight of the boat (90,000 lbs fully loaded) he has found nothing off the shelf that seems appropriate. And since my experience with moorings (as opposed to anchoring) is minimal time to ask the CF experts.

From waterline to bow chocks is close to 10' so I think total length of the pendant from buoy to cleat should be about 30'.

My first idea for the design is a single, 15' nylon line from the chain for stretch, from there a double Dyneema bridle to the chocks and cleats for strength and chafe resistance?

Limited experience with Dyneema as well but I seem to recall it can be slippery so would there be a concern with the Dyneema slipping on a cleat? If so, maybe eye splices in the ends? Also am I correct in assuming Dyneema is more chafe resistant?

Chapman says that the pennant should be 2.5 times the distance from buoy to chock...of course you will have to add the distance from chock to cleat for total rope length; don't forget chafe guards. I use two lines attached directly to the chain below the buoy, not to the buoy ring on top for my 3-legged system since 1995.

That said, you don't give the makeup of the underwater connections to this drag system, I assume all galvanized chain. Chain does not give any stretch when impacted by wind/waves, so the pennants are all the stretch you will have to counter it and it ain't much...each of my three legs is 300' three-strand nylon from anchor to bridle and I can see it work in a storm, boat moving to and fro. So, I would expect the impact jolts to be felt on the boat unless the block drags. Three-strand nylon gives the most stretch but I found it doesn't work well as a pennant because it will hockle quickly. Braided nylon works better but has less stretch.

Chapman gives a recommendation of a 3,000 lb. mushroom anchor for a 60' LOA boat in winds up to 75K. You have doubled that weight for this drag system. Please keep us advised how it all works out.

Good Luck.

~ ~ _/) ~ ~ MJH

deblen · 05-08-2021, 12:35

https://www.cruisersforum.com/forums...-252412-2.html

**skipmac** · 05-08-2021, 13:47

Thanks all for the replies. Some additional details.

Mooring is a 6000 lb block with integral carbon steel eye with 3/4" chain about 3' longer than depth at max high tide to a large ball. Local regulations mandate the main chain passes through the mooring ball to an eye on top so no need to go under the ball to connect a pendant.

In a completely protected harbor so limited fetch and worst case scenario maybe 3' chop. No room for large waves or swells to build so bouncing and chafe will be moderate though of course still a concern and must be addressed.

Nicholson58 · 05-08-2021, 14:16

The line between the cleat and any part of the boat it touches will stretch. Minimize this as much as you can. Avoid situations that cause the greatest change of direction at that rub point. This line needs to have the minimum possible stretch so that it is not sawing itself in two. We originally used 1-1/2 inch 3-strand nylon with Kevlar chafe for a mooring pennant. Swinging our 40 ton sailboat in a windy Caribbean anchorage ripped through all of this in 3-5 days. There is about 10 inches between the cleat and the hawse port. Stretch of up to 1-1/2 inches was evident of the line at the hawse. We switched to 1” Dynema four years ago, problem ended. You will still want Kevlar antichafe to protect. The nylon braided jacket. I sew this on through the Dynema along its entire length, several rows.

You could consider running a purpose built cable or chain with heavy eyes and attract the lines external to the vessel so lines do not pull around a corner. Safety line around this.

The big boys use rollers in their deck pipes.

Cadence · 05-08-2021, 15:06

Quote:

Originally Posted by skipmac

Helping son in law set up a mooring for his 56' sport fisherman. He normally keeps it at a dock but the dock has no pilings to hold the boat off in a wind so he's setting up the mooring for bad weather.

The block, chain and ball are pretty straightforward but some questions about the pendant. Since this will be for nasty conditions he wants to go with something as bulletproof as possible and due to the size and weight of the boat (90,000 lbs fully loaded) he has found nothing off the shelf that seems appropriate. And since my experience with moorings (as opposed to anchoring) is minimal time to ask the CF experts.

From waterline to bow chocks is close to 10' so I think total length of the pendant from buoy to cleat should be about 30'.

My first idea for the design is a single, 15' nylon line from the chain for stretch, from there a double Dyneema bridle to the chocks and cleats for strength and chafe resistance?

Limited experience with Dyneema as well but I seem to recall it can be slippery so would there be a concern with the Dyneema slipping on a cleat? If so, maybe eye splices in the ends? Also am I correct in assuming Dyneema is more chafe resistant?

What he may consider a mooring buoy that is a tapered top and bottom buoy. like a spar buoy. 6' above and 6' under.
It pivots with pull lessening the strain. With some ballast. The chain provides most of the ballast. Great for a hook on the top to place pendants for easy retrieval .

deblen · 05-08-2021, 15:38

https://www.youtube.com/watch?v=7QqbY5LwZGg

Nicholson58 · 05-08-2021, 16:05

Keep in mind that the 6000 # block, concrete? Will displace about half that weight in water. The block under water will ‘weigh’ 3000#. A 90,000# boat on a blow is going to drag that hunk all around. I’d say it was OK for a low windage sailboat at #20,000. We weigh 40 tons and may not pick up such a mooring in most places. I think a more appropriate anchor would be a mess of engine blocks chained together 6000# of big engine parts is way more effective than concrete. BTW, I have 14” diameter X 48” long concrete pipes for moorings at the lake house for small boats. Last week in a straight line storm the Sunfish dragged one. Big gusts.

SailingVeracity · 05-08-2021, 16:15

My 51ft 37K# ketch lives on a swing mooring in Bermuda, 12ft water. Mooring is a 4 ton forklift counterweight buried in the mud with 10ft x 2 ½ inch ships chain to 20ft x 1 ¼ inch chain through a buoy, 1 ½ inch swivel and 20ft x 5/8 inch chain over the bow roller to the samson post. 2 x 1 ¼ inch nylon double braid bridles take the load off the chain.
We seem to have annual hurricane hits and so far have weathered several car1 and 2, 2 x cat3 and 1 x cat4 storm with little problem.
If she does go, I want to take the bow to my insurance company and tell them to pay up!
My mooring inspectors call this “mooring porn”!
Yes, overkill, but I sleep well.

Nicholson58 · 05-08-2021, 16:19

Quote:

Originally Posted by SailingVeracity

My 51ft 37K# ketch lives on a swing mooring in Bermuda, 12ft water. Mooring is a 4 ton forklift counterweight buried in the mud with 10ft x 2 ½ inch ships chain to 20ft x 1 ¼ inch chain through a buoy, 1 ½ inch swivel and 20ft x 5/8 inch chain over the bow roller to the samson post. 2 x 1 ¼ inch nylon double braid bridles take the load off the chain.
We seem to have annual hurricane hits and so far have weathered several car1 and 2, 2 x cat3 and 1 x cat4 storm with little problem.
If she does go, I want to take the bow to my insurance company and tell them to pay up!
My mooring inspectors call this “mooring porn”!
Yes, overkill, but I sleep well.

8000# iron! Now that’s what I’m talking about!

Manateeman · 05-08-2021, 18:56

So you have a situation we’re you don’t have a lot of swing room and you have 10 feet from waterline to deck. Two serious issues right there. You didn’t say what the boat was made out of but sports fishermen are not the easiest boats to get the perfect mooring set up.
Let’s assume the block, chain and buoy are perfect. There are two ways to lessen the shock to whatever you have to secure the pendant to. 1, some force absorbing item. 2, lowering the attachment point on the hull.
Putting a very strong eye at the waterline is easy in aluminum hulls, requires a bit of thinking in glass and a lot of planning in wood.
The higher you go up from the waterline, the more stress is on the pendant. You can see this in films. The mooring pulls the boat down and then up again as the wave passes.
In Alaska they attach the snubber right at the waterline. The pendant runs flat parallel to the sea. They run the main chain or rope loose up to the bow in case the snubber breaks.
If you cannot modify the boat, some type of shock absorber will help. Haslett or one of the Norwegian elastic snubbers used in aquaculture nets.
Sampson doesn’t just make ropes, they have some of the best anti chafe material. They have the experience and can provide you with proven expertise which professional mariners trust in every working day.
The manatee crew.

C420sailor · 05-08-2021, 19:54

Chafe gear can’t be overstated. My 14,000lb boat on a 400# mushroom in soft mud dragged a little during a TS/CAT 1. I don’t think it was ever set right. Anyway, what almost got it was chafe of the three strand through the bow gear. One pendant was hanging on by a thread after only a few hours.

Eye opening to say the least.

Benz · 07-08-2021, 03:36

If you use a dyneema bridle, by all means splice eyes in it. I like to have dyneema from the cleat/bitts/ whatever all the way through the chocks. That way nothing is sawing on the chocks.
Some folk attach the boat to the mooring with all dyneema: I'd want to be sure it was a quiet harbor before I did that, but the heavy mooring chain will provide SOME catenary. If you can pull that off, you have lots less parts to attach together, just two dyneema legs with eyes in each end and a means to attach it (I just made a similar pennant for a 90' Gunboat catamaran, spliced to a monstrous Tylaska T50. You could use something more simple).

Manateeman · 07-08-2021, 05:14

Why would you use a T50?

Benz · 07-08-2021, 14:44

Quote:

Originally Posted by Manateeman

Why would you use a T50?

Because that's what the customer wanted. Fancy yachts have an obsession with big Tylaska shackles to attach dinghy tow bridles and mooring pennants. Inexplicable to me, but engineering is not my department: I just make what the client specifies.