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Old 09-01-2010, 13:27   #1
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Bridle Triangle Angles

Last week my old bridle disintegrated and I need to make a new one. I've read through a lot of the bridle posts here, but I haven\t found exactly what I was looking for.

I have a beam of 7.42, but between the points where I will fix the bridle permanently I have about 7 meters. To give some quick specifications: I have a 43 feet catamaran weighing around 10 tons, a Rocna 33 anchor and all chain rode. I'm heading into the Pacific, so that's where I'll be doing all my anchoring soon.

I plan to make a bridle along these lines (which I found in another post on bridles):



The big difference will be that I have stainless steel thimbles where the bridle connects to my boat. They will be permanently attached there with a shackle on each pontoon.

Now on to my questions:

1. I hear a lot of different things about the length of the bridle on a catamaran. Some say it should be a 90 - 45 - 45 triangle, others say 60 - 60 - 60, some say the legs should be so short that the bridle doesn't hit the water, while others again say it should be as long as you can.
So now I reach out to all of you, which do you prefer ... and why?

2. How thick and which kind of nylon rope would you use for the bridle?

3. Would you make the bridle out of one long rope (like in the picture above), or out of 2 ropes that get shackled together right before the chain hook?

I appreciate any help.
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Old 09-01-2010, 18:17   #2
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Hi,
Having a similar sized Catamaran - I used the following bridle - measurements and angles are approximate in the sketch to fit your distance between hulls.
I use 1" (25mm) 3 strand Nylon - with an "Eye" splice at each end - the eye sufficiently large to go over the outside cleat.

The center of the bridle is fixed to the chain hook.

The bridle is not fixed permanently.
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Old 09-01-2010, 18:59   #3
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I like it long and in the water a bit, as that can help prevent keel wraps...

Quote:
Originally Posted by SettingSail2009 View Post
Last week my old bridle disintegrated and I need to make a new one. I've read through a lot of the bridle posts here, but I haven\t found exactly what I was looking for.

I have a beam of 7.42, but between the points where I will fix the bridle permanently I have about 7 meters. To give some quick specifications: I have a 43 feet catamaran weighing around 10 tons, a Rocna 33 anchor and all chain rode. I'm heading into the Pacific, so that's where I'll be doing all my anchoring soon.

I plan to make a bridle along these lines (which I found in another post on bridles):




The big difference will be that I have stainless steel thimbles where the bridle connects to my boat. They will be permanently attached there with a shackle on each pontoon.

Now on to my questions:

1. I hear a lot of different things about the length of the bridle on a catamaran. Some say it should be a 90 - 45 - 45 triangle, others say 60 - 60 - 60, some say the legs should be so short that the bridle doesn't hit the water, while others again say it should be as long as you can.
So now I reach out to all of you, which do you prefer ... and why?

2. How thick and which kind of nylon rope would you use for the bridle?

3. Would you make the bridle out of one long rope (like in the picture above), or out of 2 ropes that get shackled together right before the chain hook?

I appreciate any help.
...when lying to 2 anchors (if you don't use all chain rode). The mass of the bridle plate and the shackles will keep the line down, like a kellet, when the tide turns.

I prefer a plate to a hook, but had to make one that fit my needs. There is a post on my blog (Sail Delmarva: Search results for chain hook)
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Old 10-01-2010, 01:29   #4
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Quote:
Originally Posted by thinwater View Post
I prefer a plate to a hook, but had to make one that fit my needs. There is a post on my blog (Sail Delmarva: Search results for chain hook)
I like the innovation of the slotted plate with keeper - must get measurements.
Although the chain hooks I use (if proper chain hooks) have never been a problem.
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Old 10-01-2010, 06:19   #5
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Quote:
Originally Posted by thinwater View Post
...when lying to 2 anchors (if you don't use all chain rode). The mass of the bridle plate and the shackles will keep the line down, like a kellet, when the tide turns.

I prefer a plate to a hook, but had to make one that fit my needs. There is a post on my blog (Sail Delmarva: Search results for chain hook)
The bridle plate is a great idea, but isn't the weak point the caribiner? The specs on all of those I've seen are far less than a similarly sized galvanized shackle.....
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Old 10-01-2010, 06:39   #6
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Quote:
Originally Posted by Laidback View Post
Having a similar sized Catamaran - I used the following bridle - measurements and angles are approximate in the sketch to fit your distance between hulls.
This is perfect, thank you very much. Out of curiosity, why did you opt for the short bridle instead of having a longer one?

Quote:
Originally Posted by Laidback View Post
I use 1" (25mm) 3 strand Nylon - with an "Eye" splice at each end - the eye sufficiently large to go over the outside cleat.
The bridle is not fixed permanently.
I'm planning to have it permanently attached, so I'll add stainless thimbles at each "eye".
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Old 10-01-2010, 06:45   #7
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Quote:
Originally Posted by thinwater View Post
...when lying to 2 anchors (if you don't use all chain rode). The mass of the bridle plate and the shackles will keep the line down, like a kellet, when the tide turns.
You said you prefer a longer bridle in your title and I definitely see a lot of merit to it. What sort of angles do you have, if you compare to the drawing made by Laidback.

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Originally Posted by thinwater View Post
I prefer a plate to a hook, but had to make one that fit my needs. There is a post on my blog (Sail Delmarva: Search results for chain hook)
Interesting concept, but I've never had problems with my chain hook slipping off the chain.
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Old 10-01-2010, 07:49   #8
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I found the attached diagram somewhere (probably on this board) that implies that the longer the bridle the better as far as distributing load. The downside would be that as the legs get longer, their ability to prevent sailing at anchor is reduced. What it does not show is the compression force created between the hulls. I think making the bridle so short that it is out of the water is a really bad idea.

I use legs equal to my beam, so making an equialateral 60-60-60 triangle. My normal bridle is a single line with a Wichard chain grip in the center. I tried a regular hook, but found it would not stay on the chain if the bridle hit the bottom. I wouldn't trust the Wichard grip in a blow. I have a storm bridle made up that uses separate lines shackled to an ABI bridle plate. I would wire a "keeper" to make sure it stays on the chain.
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Old 10-01-2010, 07:49   #9
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We use 2 different bridals. One short for very shallow water to keep the hook off the bottom and a longer about 20' for deeper water.

I find the longer one also works better in storm conditions as it provides a little more shock resistance due to length. It also helps when we need to deploy at second anchor in storm conditions as we have 2 bridals already made up for deployment.
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Old 10-01-2010, 08:59   #10
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Quote:
Originally Posted by JayH View Post
I found the attached diagram somewhere (probably on this board) that implies that the longer the bridle the better as far as distributing load.
Thank you for the diagram.

Quote:
Originally Posted by JayH View Post
The downside would be that as the legs get longer, their ability to prevent sailing at anchor is reduced.
This hasn't been much of a problem, but I am mostly in anchorages, where the wind is strong enough to keep everyone in the same direction. When I head into the Pacific, I'll hopefully get away from crowded anchorages all-together.

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I think making the bridle so short that it is out of the water is a really bad idea.
This has been my thought as well, but I was curious what other people were thinking about it.

Quote:
Originally Posted by JayH View Post
I use legs equal to my beam, so making an equialateral 60-60-60 triangle. My normal bridle is a single line with a Wichard chain grip in the center. I tried a regular hook, but found it would not stay on the chain if the bridle hit the bottom. I wouldn't trust the Wichard grip in a blow. I have a storm bridle made up that uses separate lines shackled to an ABI bridle plate. I would wire a "keeper" to make sure it stays on the chain.
This is precisely what I was looking for. The equilateral triangle is a recommendation I've also gotten from 3 other (non-forum) sources, so now that's the direction I'll be taking.

I really like the look of the Wichard chain grip, because I sometimes have problems when I'm alone onboard, that the chain hook drops off the chain, before I can lower it into the water. The Wichard chain grip will solve that problem.

Are you using 1" - 3 strand nylon on both bridles, or is the storm bridle heavier? Is your storm bridle also equilateral?

Quote:
Originally Posted by sv_makai View Post
I find the longer one also works better in storm conditions as it provides a little more shock resistance due to length.
I've found the same thing .... on my old bridle.
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Old 10-01-2010, 12:46   #11
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Quote:
Originally Posted by SettingSail2009 View Post
Are you using 1" - 3 strand nylon on both bridles, or is the storm bridle heavier? Is your storm bridle also equilateral?
My storm bridle is a little heavier and a little longer. 3-strand is plenty strong, so you don't want to make it so thick that it doesn't stretch. The Earl Hinz anchoring book is helpful for figuring out how to size your ground tackle.

One other thought: I've never figured out a good way to increase scope once the bridle is attached. I've never had to do it, but my plan is to attach a new bridle and cast off the original. With the Wichard, it will stay attached and I can retrieve it later. Probably a good idea to have multiple bridles ready to go.
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Old 10-01-2010, 18:31   #12
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Setting Sail,
Depending where your anchor roller is in relation to position where ends of the bridle are attached may determine the angle one uses in the design.
In the sketch and using your dimensions. I have given 4.03 metres (13ft) for each side of the bridle - this gives plenty enough stretch. Remembering also that a catamaran has the ability to anchor in 'thinwater' Also when the bridle is hanging vertically - The hook will be 6ft 6" from the anchor roller.
One thing to avoid is having the bridle long enough so that in a wind change having the centre of the bridle ending up under a hull on the outside.
The Chain Hooks to look for can be found here McMaster-Carr

The High-Strength (Grade 80) Alloy Steel Grab Hooks with Securing Pin—For Lifting
A spring-loaded pin on these forged hooks prevents the chain and hook from separating when chain slackens. Hooks have a red powder-coated finish. Maximum temperature is 500 F.
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Old 10-01-2010, 18:39   #13
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I guess I am showing my lack of knowlege here but....... what is a bridle actually do?
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Old 10-01-2010, 18:41   #14
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Depends on the biner. The one in the image is not what I use.

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The bridle plate is a great idea, but isn't the weak point the caribiner? The specs on all of those I've seen are far less than a similarly sized galvanized shackle.....
They are available with strengths to 8000 pounds, the one I use is 5000-pound rated.

And there is no good reasons a shackle could not be used. With my boat, there is no need.

Another advantage is that I can easily attach a 2nd rode to the hole at the apex.

Will a standard chain hook work? Yes, very well. Do be certain NOT to splice the rope into the hook eye, even with a thimble. They can be VERY rough and more than a few snubbers have chaffed through at that point. The picture posted looked correct in that matter.
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Old 10-01-2010, 18:47   #15
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Each leg is about 3' longer than the distance between the bows.

Quote:
Originally Posted by SettingSail2009 View Post
You said you prefer a longer bridle in your title and I definitely see a lot of merit to it. What sort of angles do you have, if you compare to the drawing made by Laidback.



Interesting concept, but I've never had problems with my chain hook slipping off the chain.
There is a 2nd reason too; if the anchor is launched from a roller on a bow, it is handy to be able to get both legs to one side, with some slack. It makes it easier to manage hook-up and recovery from near the roller.

No, I have never had a hook some off, and often I do not use the gate. However, if you do not have a deep slot the balance is wrong, different angles than a chain hook, and it will fall off. Also, the hook can fall off if it hits the bottom - the reason given for using a short bridle.
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