laying a mooring - bridle or single point

tim_ber

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Single point is cheaper (but very heavy sinker) and method I'd prefer because it is cheaper and a heavier chain is used and is simpler (and simple is best).

Bridle is more expensive and secure points are anchors (I've never heard of this method before - except when used as a method of anchoring in a cove where swinging room was limited).

However, I have been advised by the authority lending me the patch of seabed that I must use the bridle method because it creates a smaller swinging circle than a single point method.

BUT does it?

When anchoring, we all let out a lot of chain because the chain is horizontal on seabed and gives the large swinging circle; the chain is helping secure the boat as well as the anchor.

But with a single point mooring a lot of chain is not let out because a great big 250kg mass sits on the seabed instead of an anchor PLUS length of horizontal chain.

So, doing the maths, does the bridle method give a reduced swing radius compared to the single point method?

Seabed is flat (not a valley like my last mooring place)

I don't know if the authority is counting on the mid point of bridle rising from seabed at times.

Thanks in advance.
 
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If by "bridle" you mean a system of two anchors joined on the seabed by a chain, and with the riser coming from the middle, I cant see how it would in any way reduce swinging. If you took a riser from each anchor point and joined them ( say) 5 metres below the surface, and then took a single riser from that joining point, you would reduce swinging. Is that what they mean?
 

SHUG

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The bridle comes into its own in tidal moorings where the anchors can be laid along the line of the current flow. The ususal arrangement is to take a riser from the centre point and thereafter it is like a singlepoint mooring.
The choice should be based on the type of seabed.
 

vyv_cox

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The method posted by Bosun Higgs is normal in tidal moorings, e.g. Menai Strait, with anchors up- and down-tide. Can't see how it restricts swinging though. My only other suggestion is bow and stern mooring in which the boat cannot rotate about a single riser, thus reducing risk of clashing.
 

neil_s

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The single point (clump) really needs a chain of 3 x the depth at high water as a minimum - like all other anchors. Many harbour authorities like it because they can stipulate that you use an enormously heavy clump ( a lot heavier than 250 Kg) and then have a short chain. This minimises the swinging circle. This is OK in light weather, but when it blows up rough it is very hard on the boat which is moored short in a heavy, steep sea. Using two anchors on a bridle is better, but you still need to have a minimum length from each anchor to the boat of 3 x the depth at high water. As an examble, my own single clump mooring has a depth of 5 metres at high water springs, which suggests a chain of minimum length of 15 metres, yet the harbour authority stipulates that the mooring sites are 24 metres apart. If you assume a boat length of 9 metres added to 3 x depth allowance, it is possible for your boat to sit on next door's mooring clump at low tide! I have thus cut my chain so that it is 12 metres long. OK for Summer? As long as the next door boat isn't some flighty lift keel racer which is wind rode when your fin keel world cruiser is tide rode. I would like to use my mooring all year so I am thinking of getting myself two anchors. Eric Hiscock in 'Cruising under sail' suggests they should be 2 x bower weight, ie 50 lb. for a 28 foot boat, and they should also be 6 m apart.

Cheers! Neil
 

ghostlymoron

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The single point (clump) really needs a chain of 3 x the depth at high water as a minimum - like all other anchors. Many harbour authorities like it because they can stipulate that you use an enormously heavy clump ( a lot heavier than 250 Kg) and then have a short chain. This minimises the swinging circle. This is OK in light weather, but when it blows up rough it is very hard on the boat which is moored short in a heavy, steep sea. Using two anchors on a bridle is better, but you still need to have a minimum length from each anchor to the boat of 3 x the depth at high water. As an examble, my own single clump mooring has a depth of 5 metres at high water springs, which suggests a chain of minimum length of 15 metres, yet the harbour authority stipulates that the mooring sites are 24 metres apart. If you assume a boat length of 9 metres added to 3 x depth allowance, it is possible for your boat to sit on next door's mooring clump at low tide! I have thus cut my chain so that it is 12 metres long. OK for Summer? As long as the next door boat isn't some flighty lift keel racer which is wind rode when your fin keel world cruiser is tide rode. I would like to use my mooring all year so I am thinking of getting myself two anchors. Eric Hiscock in 'Cruising under sail' suggests they should be 2 x bower weight, ie 50 lb. for a 28 foot boat, and they should also be 6 m apart.

Cheers! Neil
Eric Hiscock in 'Cruising under sail' is a mine of information even after all these years!
 

neil_s

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Sorry - I just checked with Eric's book - he quotes anchor separation as 6 times the depth at high water, not 6 m as I said above.

Neil
 

tim_ber

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Thanks for that.

The upstream downstream bit never occurred to me.

They told me it was because of swinging radius which perplexed me a bit, but Neil's post has given me something to digest too.
 

William_H

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Moorings

As said using a very heavy weight you must have a rode that allows the boat to ride on a rode at say 45 degrees to horizontal at worst case high tide storm surge plus waves. Any steeper then the pull horizontally of the boat is going to translate to some lift of the weight. If the boat tries to lift the weight because rode is too short you will either lift the weight or more likely destroy your attachment points on the boat. Either way you are in trouble.
A bridle system does give more leeway in that the middle of the bridle can be lifted in extremes on wave peaks giving effectively bit more rode but with decent weight chain and anchors and unless the bridle is very long you still need a decent rode length. So not much difference in swing circle. olewill
 

tim_ber

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As said using a very heavy weight you must have a rode that allows the boat to ride on a rode at say 45 degrees to horizontal at worst case high tide storm surge plus waves. Any steeper then the pull horizontally of the boat is going to translate to some lift of the weight. If the boat tries to lift the weight because rode is too short you will either lift the weight or more likely destroy your attachment points on the boat. Either way you are in trouble.
A bridle system does give more leeway in that the middle of the bridle can be lifted in extremes on wave peaks giving effectively bit more rode but with decent weight chain and anchors and unless the bridle is very long you still need a decent rode length. So not much difference in swing circle. olewill

Thanks for that.

So my understanding is that if the swing circle is not greater with the single point / clump/ heavy weight, then all I do is make good calculations, leave enough chain spare, use snubbers, use rope to boat and chain to boat (but slack) as backup in case rope ever snapped / chaffed...

and I have gone from £600 system (bridle) to £300 system (single weight)

and as long as barge and winch can handle the heavy weight, the system is easier to lay and recover.

I will talk to the authorities and see if they will let me go for the cheaper method.

Have a good weekend all.
 

tim_ber

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Thanks for that.

I did miss it.

I watched all of your 'regular' films before I got onto the scuttlebutt section and then my subscription ran out soon after your new website went up (and very good it is too).

I will be renewing, of course.

Hope to bump into you on the water one day (not literally).
 

dylanwinter

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should not have happened

Thanks for that.

I did miss it.

I watched all of your 'regular' films before I got onto the scuttlebutt section and then my subscription ran out soon after your new website went up (and very good it is too).

I will be renewing, of course.

Hope to bump into you on the water one day (not literally).

the film was put up just a a few weeks ago

I am posting new films every friday

the "new" website went live on Oct 3

every subscriber had his sub set back to three months so nothing ran out between Oct3 and jan3

if it did.... drop me a line and I will give you the three months grace that everyone else got

Dylan
 
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tim_ber

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the film was put up just a a few weeks ago

I am osting new films every friday

the "new" website went live on Oct 3

every subscriber had his sub set back to three months so nothing ran out between Oct3 and jan3

if it did.... drop me a line and I will give you the three months grace that everyone else got

Dylan

Thank you, but no.

I will renew the tiny subscription (when work eases off a bit to allow me time to sit and watch large chunks of video) in the hope it helps you to keep doing what you are doing.

And the best of luck with all the media attention you are getting from USA etc. I hope it provides an income.
 

Mavis

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If by bridle, they mean a chain from each anchor right up to the buoy then your swinging circle will reduce.
 
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