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lillia28 10-10-2011 10:42 AM

Mooring Pendant Length
 
I'm trying to figure out a couple of mooring questions. Does length of the pendant affect the scope of the mooring rig? It seems to me that the effective scope is to the mooring ball. Most of the pre-made pendants are offered in lengths of 12 to 20 feet. If the length is 1.5 the distance from the water line to the chock, do that many boats have freeboard of 9 to 14 feet? It seems to me a long pendant just increases the swing circle. If the wind is stretching the chain, the scope will still be to the ball regardless of how far the boat is from the ball. If you are expecting a storm surge, wouldn't it be more prudent to add a shot of chain, rather than depend on pendant length? Or am I missing something?
Anyone have any experience with the dyneema pendants?

Thanks
lou

Maine Sail 10-10-2011 11:18 AM

Quote:

Originally Posted by lillia28 (Post 784515)
I'm trying to figure out a couple of mooring questions. Does length of the pendant affect the scope of the mooring rig? It seems to me that the effective scope is to the mooring ball. Most of the pre-made pendants are offered in lengths of 12 to 20 feet. If the length is 1.5 the distance from the water line to the chock, do that many boats have freeboard of 9 to 14 feet? It seems to me a long pendant just increases the swing circle. If the wind is stretching the chain, the scope will still be to the ball regardless of how far the boat is from the ball. If you are expecting a storm surge, wouldn't it be more prudent to add a shot of chain, rather than depend on pendant length? Or am I missing something?
Anyone have any experience with the dyneema pendants?

Thanks
lou

The longer the better. Short pendants can fail earlier than longer ones as the heat generated by making the tight bend over the chock can impose undue heat and chafe loading. They also leave you with less shock absorber/shock loading absorption when the chain is drawn near bar tight in a storm.



http://www.pbase.com/mainecruising/image/129592514.jpg

Barquito 10-10-2011 11:38 AM

The scope will include the chain. Look at the two boats in Maine Sails photo. The rope and chain will (amost) be in a straight line through the ball to the anchor. the one in the foreground has less scope than the one in the back. Some mooring fields just don't have anough room to have anything longer than the minimum to keep from bumping other boats.

delite 10-10-2011 01:07 PM

The longer the pendant the more likely it will become fowled in the mooring ball chain when there is slack in the line. We used to have a long pendent to our mooring ball but grew tired of untangling the mess every time we went sailing.

jackdale 10-10-2011 01:42 PM

Low modulus lines like Dyneema and Spectra should NOT used as a pennant. Use something that will stretch and absorb shocks, like nylon. I like a bridle that run from cleat to cleat with a full round turn on the ring. Then run a second bridle in case the first fails.

Maine Sail 10-10-2011 03:29 PM

Quote:

Originally Posted by Barquito (Post 784531)
The scope will include the chain. Look at the two boats in Maine Sails photo. The rope and chain will (amost) be in a straight line through the ball to the anchor. the one in the foreground has less scope than the one in the back. Some mooring fields just don't have anough room to have anything longer than the minimum to keep from bumping other boats.

That is untrue. The boat in the fore ground has shorter pendants and will suffer from more chafe issues in a storm. Scope in this mooring field is dictated by the harbor master so both boats should be within a few feet of each other scope wise.

Maine Sail 10-10-2011 03:32 PM

Quote:

Originally Posted by jackdale (Post 784580)
Low modulus lines like Dyneema and Spectra should NOT used as a pennant. Use something that will stretch and absorb shocks, like nylon. I like a bridle that run from cleat to cleat with a full round turn on the ring. Then run a second bridle in case the first fails.

Actually Spectra and Dyneema make bomb proof pendants but they should be used only to get through the bow chocks to the normal nylon/polyester pendants so that you still have some shock absorption.

Maine Sail 10-10-2011 03:38 PM

Quote:

Originally Posted by delite (Post 784563)
The longer the pendant the more likely it will become fowled in the mooring ball chain when there is slack in the line. We used to have a long pendent to our mooring ball but grew tired of untangling the mess every time we went sailing.


If your mooring system is set up incorrectly this can and will happen. We have not had a pendant tangle in our mooring ball or chain in 12 years and we use dual, long unequal length pendants. One of our moorings, our storm mooring in front of the house, has one 25 foot and one 30 foot pendant.

We use that mooring perhaps twice per year and the pendants have never once fouled anything. We have also ridden out some very severe Nor' Easters and never had any chafe issues.

I have studied mooring failures for nearly 25 years and short pendants always fail earlier at the chock, most likely due to heat. Another big area for failure is anchor chafe. Our town harbor master now mandates anchors be removed from the bow in storm conditions.

billyruffn 10-10-2011 10:56 PM

Quote:

Originally Posted by delite (Post 784563)
The longer the pendant the more likely it will become fowled in the mooring ball chain when there is slack in the line. We used to have a long pendent to our mooring ball but grew tired of untangling the mess every time we went sailing.

To prevent this problem put a float every 3-4 ft along the pennant between the ball and the boat.

RobGallagher 10-10-2011 11:32 PM

Quote:

Originally Posted by Maine Sail (Post 784622)
If your mooring system is set up incorrectly this can and will happen. We have not had a pendant tangle in our mooring ball or chain in 12 years and we use dual, long unequal length pendants. One of our moorings, our storm mooring in front of the house, has one 25 foot and one 30 foot pendant.

We use that mooring perhaps twice per year and the pendants have never once fouled anything. We have also ridden out some very severe Nor' Easters and never had any chafe issues.

I have studied mooring failures for nearly 25 years and short pendants always fail earlier at the chock, most likely due to heat. Another big area for failure is anchor chafe. Our town harbor master now mandates anchors be removed from the bow in storm conditions.

In the setup you describe;
Is there a swivel on the shackle that connects the pennants to the top chain or do you simple attach the pennants to one shackle? I'm debating on using a single pennant, bridle, or long/short option.
I'm leaning towards long/short with them going to two separate cleats.


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