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crayiii · 05-07-2019, 10:20

We're currently on a mooring in Grenada where it's gusting up to 30-35. I have two 1.25" lines (I think they are nylon) coming from the mooring pendant to outboard cleats on our 42' catamaran.

The lines are each out about 25' (our beam) and centered. We are getting jerked pretty hard to the point we need to hang on when we feel it coming.

Is there a way for us to minimize this? More scope, less scope? Smaller line to the pendant?

**tkeithlu** · 05-07-2019, 10:59

Sounds like the distances are too short for the elasticity of nylon to be much help. Elastic snubbers such as these

https://www.amazon.com/Sea-Dog-EPDM-...a-561118903134

are a next step, but not much help here and now. Can you back off?

crayiii · 05-07-2019, 11:04

Quote:

Originally Posted by tkeithlu

Sounds like the distances are too short for the elasticity of nylon to be much help. Elastic snubbers such as these

https://www.amazon.com/Sea-Dog-EPDM-...a-561118903134

are a next step, but not much help here and now. Can you back off?

I actually just pulled them in really tight because it was allowing us to accelerate and snap up to a stop. Started getting these spider webs in the gelcoat.

Montanan · 05-07-2019, 11:39

Quote:

Originally Posted by crayiii

We're currently on a mooring in Grenada where it's gusting up to 30-35. I have two 1.25" lines (I think they are nylon) coming from the mooring pendant to outboard cleats on our 42' catamaran.

The lines are each out about 25' (our beam) and centered. We are getting jerked pretty hard to the point we need to hang on when we feel it coming.

Is there a way for us to minimize this? More scope, less scope? Smaller line to the pendant?

Is sounds like you have comparatively little stretching of your snubber. The diameter of 1.25" is likely much too thick to be able give much, I would suggest 3/4 or preferrably 5/8 inch line maximum, and the 25 foot length is rather short causing much inward / sideways angle of pull on the cleat, instead of forces aligned with the cleat. The longer the better, 50 to 70 feet for your size of vessel.

Reference Practical Sailor Article regarding this subject: https://www.practical-sailor.com/iss...e_11951-1.html

"Snubber Length
• Double-braid or brait nylon snubber length = 1.3 x boat length. For dynamic climbing rope, snubber length = 1.1 x boat length. These are minimum snubber lengths; longer is better, up to about 60 feet.

Snubber Diameter
• Snubber diameter = Displacement^0.4 x 0.00832, where diameter is in inches and displacement is in pounds. Multiply this by 1.6 for catamarans to compensate for added windage. For two-leg bridles, multiply the final diameter by 70 percent. (One leg will occasionally carry the load, but this is offset by reduced yawing.)"

Montanan · 05-07-2019, 11:57

Per your photo your snubber is running against two of your stanchions. See image below.

Why don't you attach your snubber to the inner hardpoint or run the snubber over the outer beam of the hull when using the side bow mounted cleats so as to not apply huge cyclic loading to your stanchions? Those chrome tubes are not made to take any significant loading, e.g., the weight of a person falling onto a life line and not the entire inertia of the boat moving about on mooring or anchor rode. Suggestion: Never use a stanchion as a fairlead.

crayiii · 05-07-2019, 12:07

These Lagoons are set up horribly for a mooring ball. The way I had it is the way most owners recommend doing it. I've just moved them down to the eyes where Lagoon has the anchor bridle connected. Much better ride so far but upside down, over the lifeline, non visible, tensioned bowlines are not pleasant!

Montanan · 05-07-2019, 12:35

If you are located in shallow water and a length of 50 to 70 feet of bridle lines is too much, just reposition the line attachments to your mid-ship cleats from the bow cleats or to your winches so as to allow for continuous use of a long - hence springy bridle lines by taking up some of the length alongside your beam.

Montanan · 05-07-2019, 12:46

The set up of the bow line attachments hard points on the Exit Only Catamaran with a stainless steel loop extending off the bow and the bridle line held by D shackles attached to the steel loop and with the bridle passing the D shackle through a steel thimble / eyelet makes for chafe free lines and tremendous axial load sharing on the bow. No cleating or fairleads or chaff guards required. The bridle doesn't touch the deck, toe rail or deck fixtures. The five larger diameter through bolts would derive much greater sheer strength than the two narrow thickness bolts in most stand up cleats.

Reference near to the bottom of the linked article: Blue Water Catamaran - Exit Only Sails Offshore Around The World.Â* Captain Dave - Privilege 39

"If you examine these pictures, you will see the parachute sea anchor chainplates that I put on my bows for use during storms, and I also sometimes use them at anchor in harbors if a major storm is headed my way. They create a chafe free way to attach a bridle to Exit Only.

These chainplates are twenty-five inches long on deck and consist of six millimeter thick stainless steel. On the underside of the deck is the same size of stainless plate, but it is only twenty inches long. Large bolts go through the deck and through both chainplates, and there is nearly zero chance that these chainplates will ever move. If they move, it's because both bows will have been pulled off the boat.

Welded down both sides of the chainplate and sticking out in front of it is a stainless steel bail that is about as thick as my finger. The part of the bail that sticks out in front of the bow is where I attach my parachute bridle using d-shackles that I wire closed after the bridle is in place. The bridle has large stainless steel thimbles on it so there is no chafe on the arms of the bridle where they are shackled to the bails."

crayiii · 05-07-2019, 13:10

Quote:

Originally Posted by Montanan

The set up of the bow line attachments hard points on the Exit Only Catamaran with a stainless steel loop extending off the bow and the bridle line held by D shackles attached to the steel loop and with the bridle passing the D shackle through a steel thimble / eyelet makes for chaf............"

Wow, you have a ton of great info on your site!

thinwater · 05-07-2019, 13:43

Quote:

Originally Posted by crayiii

I actually just pulled them in really tight because it was allowing us to accelerate and snap up to a stop. Started getting these spider webs in the gelcoat.

I'd pay attension to that gap. I understand it is just the tail that is in there, but that could be bad from a chafe standpoint of the bridle fell in there.

I had one like this:

That I fixed like this:

thinwater · 05-07-2019, 13:55

Mooring ball set-ups are more complicated re. surging than anchoring, because of the dynamic of the short but heavy chain, ball that pulls under, and heavy pendant. Normally they are sheltered from waves, so what you are experiencing must be the result of a sort of mismatch between the spring rate of the mooring and the momentum of the boat. If you were anchored, the advice would be more scope and a longer, thin snubber. But this is different.

* How much is the boat yawing side to side (compass bearing)? That can cause jerking, because the boat develops slack as it tacks to one side. The solution at a mooring (anchoring is different) can be either a longer or shorter bridle, which ever breaks the cycle.
* Do you have a thinner nylon line (5/8")? Leave the heavy lines in place, but perhaps even longer. Attached the thin line to the ball and the second set of cleats, such that the main lines have ~ 2 feet of slack in them. This thin line will wear out in a year or less, but will soften the ride. The main line backs it up.

I sure wouldn't be reaching down to the eyes every time!

crayiii · 05-07-2019, 14:05

Not a lot of swell but the wind is coming down through the cut and gusting. We're yawing a bit but now that I've moved the lines down to the eyes, the jerk is gone. I've also let out another 15 feet of scope.

I think what I'm going to do (said this in another thread) is attach a lenght (I'm thinking 35 feet) of 3/4 3-strand nylon to each eye and have a mantus mooring snap shackle on each to clip to mooring pendants. I'll also loop in but keep slack a dockline as a backup.

I don't like snap shackles for this use but with two of them and a backup line, I'm okay with it.

The lenght is what I'm wondering. We're 25' on the beam.

thinwater · 05-07-2019, 14:16

Quote:

Originally Posted by crayiii

Not a lot of swell but the wind is coming down through the cut and gusting. We're yawing a bit but now that I've moved the lines down to the eyes, the jerk is gone. I've also let out another 15 feet of scope.

I think what I'm going to do (said this in another thread) is attach a lenght (I'm thinking 35 feet) of 3/4 3-strand nylon to each eye and have a mantus mooring snap shackle on each to clip to mooring pendants. I'll also loop in but keep slack a dockline as a backup.

I don't like snap shackles for this use but with two of them and a backup line, I'm okay with it.

The lenght is what I'm wondering. We're 25' on the beam.

How much are you yawing (compass course)? Not "a bit" since that doesn't mean anything, but a range of numbers.

I assume you mean another 15 feet of bridle, since you are on a mooring. How deep is the water?

Bridles are typically 1-2x beam. More results in single-leg loading, which causes fatigue. Less increases yawing and snubbing. Once in a while very short bridles are used to keep the ball away from the hulls, but only in calm winds.

crayiii · 05-07-2019, 14:25

Quote:

Originally Posted by thinwater

How much are you yawing (compass course)? Not "a bit" since that doesn't mean anything, but a range of numbers.

I assume you mean another 15 feet of bridle, since you are on a mooring. How deep is the water?

Bridles are typically 1-2x beam. More results in single-leg loading, which causes fatigue. Less increases yawing and snubbing. Once in a while very short bridles are used to keep the ball away from the hulls, but only in calm winds.

20 deg is the most I've seen since lengthening and moving the the bridle off the cleat. 12 deg is 80%of the time.

We've got 14 feet under the keels