Bridle Question

[PetePetePete]

I think I've learned a great deal since joining here, and I want to see if I understand things...

If you have 30' of chain, 4' of freeboard, and a 28' bridle... how deep can the water be. The way I see it, the bridle, with that much chain is almost useless or am I wrong? (Perfectly fine with being wrong).

[Cheechako]

I'm not sure what your question is. 30 feet of rode will get you anchored in 5 or 6 ft of water. Is the "bridle" a snubber? You don't need a snubber with 30 ft of chain, just let the chain past the roller.

[thinwater]

Originally Posted by Cheechako

I'm not sure what your question is. 30 feet of rode will get you anchored in 5 or 6 ft of water. Is the "bridle" a snubber? You don't need a snubber with 30 ft of chain, just let the chain past the roller.

I'm guessing you don't regularly anchor in 5' of water on chain. I do. In strong conditions the chain will offer zero catenary and the forces on the chain will be staggering. I have measured (load cell) forces over 1000 pounds in just 25-30 knots with an 8000-pound boat. In a storm the roller would likely be destroyed. A long snubber can reduce this by ~ 50%.

In fact, this is when a snubber is most needed. At least 15', if there is any exposure to waves. Yup, it will touch bottom, unless rigged farther back than the bow.

http://www.practical-sailor.com/issu...e_11951-1.html

[PetePetePete]

Originally Posted by thinwater

I'm guessing you don't regularly anchor in 5' of water on chain. I do. In strong conditions the chain will offer zero catenary and the forces on the chain will be staggering. I have measured (load cell) forces over 1000 pounds in just 25-30 knots with an 8000-pound boat. In a storm the roller would likely be destroyed. A long snubber can reduce this by ~ 50%.

In fact, this is when a snubber is most needed. At least 15', if there is any exposure to waves. Yup, it will touch bottom, unless rigged farther back than the bow.

What is Ideal Snubber Size? - Practical Sailor Print Edition Article

I have to admit. I didn't understand that.

I guess my question is... if I have a 28' Bridle found here:
Mantus Anchors | Mantus Bridle - Mantus Anchors (The Small)

And I have 30' of chain (5/16)...

I'm assuming I can affix the bridle to any portion of the chain along it's 30' length that works with the depth of the water as it relates to the scope I wish to achieve.

So... for example, let's assume a scope of 7:1 for overnight. With a 3' depth and a 4' freeboard.

So that's 7' x 7' = 49'

49'-28' (Bridle)= 21'. Therefore, do we want to place the chain hook near the end of the chain, and then utilize the bridle to take the "hit" (so to speak) with one line on each sponson (in my case, since it's a WorldCat).

If that's all wrong... I'm ready to get schooled.

Thanks,
Pete

[AD28]

I never account for the bridle length, which isn't really 28' (I'll explain) anyway.

In your example, I'd let out the 49' of chain or chain/rode, and then attach the bridle at that point. Then let a bit more line out such that there is a catenary in the rode between the bridle attachment and the boat. If you only have a hook, and you only have 30' of chain, then you'll need to add a bit of line or something to the bridle so you can attach that bridle to the rope rode. (Search the forums, people have done this quite a bit)

Which would (here's the explanation) give you only about 9' or so more anchor/length by adding the bridle, because: 1. The bridle is attached to both bows, so that 28' bridle length is halved, more or less; and 2. the length is even shorter, because it is triangulated between the bows. Not knowing your beam but let's assume it's 14': the 28' is then two legs of a triangle, each of those two legs are 14' and the third, your beam, is 14' so then your distance from the boat to the end of the bridle is taken from the front x-beam (center between your bows) to the mid-point/apex of the bridle.

Hope that makes sense

btw it's 'hulls' not 'sponson' or 'pontoon'. Actually, they're 'vakas'... ah, never mind

[zeehag]

forget the bridle length. it is irrelevant at this time. you need to know where you can anchor with only 30 ft chain.
i found while sailing gom, as the man only used 30 ft chain, that we dragged a lot. you will do a lot better with 100 ft chain . find a second anchor you can piggy back with the one you primarily use so you have extra weight on the bottom. keeps your boat stuck better...
worry about the snubber after you have the gear to keep anchor stuck.
i was recently anchored in a locale with a lovely lagoon of 8-10 ft depth, and requiring 150 ft chain to keep boats from drag queen activities. it is quite entertaining watching someone try to find their boat after it has been relocated by neighbors due to dragging thru an anchorage at wind speed.....

[Cheechako]

Originally Posted by thinwater

I'm guessing you don't regularly anchor in 5' of water on chain. I do. In strong conditions the chain will offer zero catenary and the forces on the chain will be staggering. I have measured (load cell) forces over 1000 pounds in just 25-30 knots with an 8000-pound boat. In a storm the roller would likely be destroyed. A long snubber can reduce this by ~ 50%.

In fact, this is when a snubber is most needed. At least 15', if there is any exposure to waves. Yup, it will touch bottom, unless rigged farther back than the bow.

What is Ideal Snubber Size? - Practical Sailor Print Edition Article

You are correct that I have never anchored anything but a small rowboat in 5 ft of water! Nor would I. BTW, my 42 ft cat was anchored in 12ft-14ft of water in steady 30-35 winds, protected and no wave action. I was very surprised while snorkeling to discover there was lots of catenary in the chain. (Tobago Cays)

[PetePetePete]

LOL.

catenary = slack

LOL... just wanted to dumb it down for anyone who stumbles on it and doesn't google it (like I did).

...onward... so if I understand correct, without doing some kind of rode to bridle setup, the bridle isn't going to help me.

Ok... I'm going to keep reading...

[thinwater]

AD28. Check your trig. A 28' bridle will be 27' with a 14' beam. Try Pythagoras. 28^2-7^2=27^2. Perhaps you missed that BOTH legs are 28'. The Mantus bridles are long.

As for never anchoring in shallows, that depends on where you sail. Around here (mid-Atlantic, Chesapeake) that rules out many of the nicest places. I have been sailing for 30 years and have only anchored in > 10' twice that I can remember.

As for needing 100' of chain, popycock. This depends on the bottom type and the anchor, and bridles. I like chain, but it does not need to be a mantra.

Yes, you can attach the hook at rode length-snubber.
* Some the of the chain between the snubber and the boat is still pulling down on the hook.
* In 5 feet of water even all chain will lift off the bottom in 15-20 knots. Fact. Deeper water has different math.
* Nobody said the snubber had to attach to the bow cleats. Attach the sunbber to the midships cleats and run it through the chocks inside webbing to allow free movement. Works great, I do this most of the time.

I anchor a 16x34 cat in 5 feet all the time. I attach the hook at about the 40' mark and use a 35' bridle with the eyes over the mid-ships cleats. Great shock absorption, no yawing at anchor. If I decide I need more scope in a storm, I simply move the bridle to the bow cleats and let out ~ 18' more chain.

(This is a Mantus bridle. I use something different now, but this works fine. Yes, I relocated the chafe gear to where it was needed. I ran it outside the cleats because that created a nice smooth run.)

[Wanderlust]

PetePetePete,
Just to clarify ... a catenary is a bit more than the slack in a rode. In normal anchoring conditions, the chain either has some slack (part of it laying on the bottom), or is lifted up a little to form a curve from the anchor to the bow (the catenary). The benefit of the catenary is that sudden loads from gusts and waves are absorbed as the chain gets pulled closer to straight, and then the weight pulls it back down again.

Of course, as the wind gets stronger and waves get bigger, the catenary will be gone. If the chain gets pulled tight, the shock loads will be transferred to your deck and mounting points. If you ever experience this, you will appreciate why you need a bridle or snubber that stretches to absorbs these sudden jerks. This is normally attached to the chain with a chain hook or many cruisers tie it on.

You asked about rode to bridle attachment ...
http://www.cruisersforum.com/forums/...-95248-10.html

In your case, with only 30 feet of chain, the catenary effect will be small. So then you have the bridle. It will stretch, providing the main shock absorbtion.

So back your original question. With 30 feet of chain and 27 feet of bridle you have 57 feet of rode. Then decide the scope ratio you want. Aim for a minimum of 3:1 (maybe less for "lunch stops" where a drag would not be a disaster) but aim for 5:1 for overnighters if there is room. 3:1 gives you 19 feet to your deck, and 5:1 gives you 11 feet (i.e. 7 feet water depth). Strong conditions would want more scope, but you are fast running out of water depth ... calculate scope for high tide, safe depth for low tide.

If you were in shallower water, I would still use most of the chain and tie off the bridle a bit shorter.

This all assumes you have a decent anchor and suitably sized chain and bridle in normal conditions. No doubt you have a line from your chain to retrieve it and act as backup to the bridle. And of course, test to ensure the anchor is set.

[StuM]

Originally Posted by thinwater

AD28. Check your trig. A 28' bridle will be 27' with a 14' beam. Try Pythagoras. 28^2-7^2=27^2. Perhaps you missed that BOTH legs are 28'.

You should use a much shorter bridle for that beam of cat. While it will do a good job as a shock absorber, it will do very little to stop sailing at anchor, which is the other major reason for using a bridle on a cat.

[thinwater]

Originally Posted by StuM

You should use a much shorter bridle for that beam of cat. While it will do a good job as a shock absorber, it will do very little to stop sailing at anchor, which is the other major reason for using a bridle on a cat.

1. I think a few posters (not Stu) have overlooked the fact that a catamaran must always use a bridle to keep from sailing around, so we always use at least 1xbeam and nylon, killing several birds with one stone.

2. The correct length depends on several factors.
a. We like to keep the hook off the bottom to reduce chafe. However, in keeping with (1) this is not always possible. You can shorten up, but you loose stability (will yaw more) and shock absorption.
b. How much is needed to absorb wave and gust shock? Many calculations and testing agree that about 1 x LOA is about right in shallow water, tapering off to very little in water over 30 feet. However, cats frequently anchor in shallow water... because we can (obviously, never when waves can be over ~ 25% water depth).

As I showed above, one solution is to anchor the bridle back from the bow. You get the full shock absorption benefit without the hook lying on the bottom.

So while you don't need a bridle more than ~ 1x beam, there is no harm in more. Just cleat off what you don't need. When a storm comes, you can let out. Otherwise, adding scope to a cat with a bridle can be a real pain, particularly if the windlass is not centered.

As for Pete's original question, I admit I don't understand what he is asking. If he has only 30' of chain (no rope attached, which is not true, I hope), he can anchor at 7:1 scope (you don't use short scope in this little water) in about 3 feet of water. Obviously he is going to either need more chain or he will be attaching the bridle to the rope with a hitch. As soon as rope enters the equation, he has little need for the long bridle.

A longer bridle can help some boats sit still better. I don't know about his. 1x beam is too little for mine, 1.5 is good.

[PetePetePete]

Guess I wasn't clear. I'm sorry about that.

I have 30' of chain and 300' for rode.

Hope that clears things up.

[PetePetePete]

Originally Posted by thinwater

1. I think a few posters (not Stu) have overlooked the fact that a catamaran must always use a bridle to keep from sailing around, so we always use at least 1xbeam and nylon, killing several birds with one stone.

2. The correct length depends on several factors.
a. We like to keep the hook off the bottom to reduce chafe. However, in keeping with (1) this is not always possible. You can shorten up, but you loose stability (will yaw more) and shock absorption.
b. How much is needed to absorb wave and gust shock? Many calculations and testing agree that about 1 x LOA is about right in shallow water, tapering off to very little in water over 30 feet. However, cats frequently anchor in shallow water... because we can (obviously, never when waves can be over ~ 25% water depth).

As I showed above, one solution is to anchor the bridle back from the bow. You get the full shock absorption benefit without the hook lying on the bottom.

So while you don't need a bridle more than ~ 1x beam, there is no harm in more. Just cleat off what you don't need. When a storm comes, you can let out. Otherwise, adding scope to a cat with a bridle can be a real pain, particularly if the windlass is not centered.

As for Pete's original question, I admit I don't understand what he is asking. If he has only 30' of chain (no rope attached, which is not true, I hope), he can anchor at 7:1 scope (you don't use short scope in this little water) in about 3 feet of water. Obviously he is going to either need more chain or he will be attaching the bridle to the rope with a hitch. As soon as rope enters the equation, he has little need for the long bridle.

A longer bridle can help some boats sit still better. I don't know about his. 1x beam is too little for mine, 1.5 is good.

To be clear. My concern was as follows.

If I have 30' of chain out and I only put out 35' - that would mean I have 30' of chain and 5' of rode. Which I have to think is a poor idea to let 5' of rode take the stress of 30' of chain (or is it fine?)... so, what I would have thought the smart thing to do would have been to use the bridle in conjunction with the chain (not certain where to place the chain hook)... thus still getting the benefit of the weight of chain, but the bridle can take the shock for it.

Or... dumbing it down... if I'm in 7' (water+freeboard) and that gives me 49' at 7:1... do I just let out 30' of chain and 19' of rode tie it off on a cleat and say good night? If it's just that simple, smack on the head and I'm good - I can take it.

Or would I be better off using the bridle, and if so, how so.

Sorry for the long thread on what should be simple... I watched YouTube video after video... and whenever you see a person with a bridle they've got a zillion feet of chain in deep water. I'll be in the keys, in 3'-5' of water at times.

[StuM]

Yes, you DO want to use the bridle. But you need to make it much shorter. With a 14 ft beam, I'd be using around 15ft in each leg. That will give an "extension" of 13ft.

So if you want 7:1 in 3ft of water + 4ft of freeboard, you make that 49ft by letting out your 30ft of chain plus another 6ft of rode, attach your bridle to the rode with some sort of hitch and then let out more rode until the bridle is fully extended. Then let a bit more rode out so the rode is hanging in a loop. Finally cleat the loose rode.