Caternary & Chain... - Page 7 - SailNet Community
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post #61 of 84 Old 11-11-2013
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Re: Caternary & Chain...

A riding sail set on the backstay is effective to eliminate sailing at anchor. Need not be very large.
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post #62 of 84 Old 11-11-2013
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Re: Caternary & Chain...

The riding sail is probably a good thing to a swag of 30-40 knots, after that, it might very well propel the blinking boat forward at a reasonably significant speed per say. Under this amount it might work to calm the ride per say....... this is a guess on my part too!

If I was in 50-60+ knot winds, I would swag as noted by many, that more scope, BIG anchor etc is best.

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post #63 of 84 Old 11-11-2013
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Re: Caternary & Chain...

This whole issue is one that has gotten some conversation on another forum, and I still stick by the fundamental premise I came to there which is that. "Pound for pound, additional weight in the anchor increases holding power faster than weight in the chain." Assuming this premise is true, and there is a lot of justification to believe that it is, then best practice would be to move as much weight from the chain to the anchor as possible.

In reality most cruisers carry anchoring systems that were designed decades ago when electric windlasses were expensive and very rare. With modern handling equipment the small anchor + lots of chain model, is incredibly inefficient requires carrying a huge amount of excess weight and provides minimal holding power. All in all this system is really due for a rethink.

Modern anchors generally create 40lbs of holding power or more for every pound of dead weight they have. While chain generates about 1lbs of holding power for every pound of weight. This massive difference is because modern anchors are incredibly efficient at converting their weight into holding power, while chain really adds nothing but dead weight.

So when we consider the 'average' anchoring system on a 40' cruiser what do we find? Typically a 60lbs primary anchor and 300' of 3/8BBB chain weighing in at 1.7lbs/foot. Then a secondary anchor of a slightly smaller size and the same amount of chain used to increase holding power in storms. A perfectly reasonable and reliable system... Until you consider that when it's all added up this system comes out to 1,070lbs of chain and 120lbs of anchor. Even while we know that anchor weight is much more important that chain weight.

Instead of this, my recommendation is to
1) get rid of the second anchor entirely, saving over 500lbs in weight alone
2) switch from 3/8BBB to 1/4 Grade 70 chain which will save 290lbs
3) Get rid of the 60lbs anchor and get a 120lbs one

All in all this saves 725lbs of weight from the bow of the boat, puts the weight where it matters the most, and puts an anchor on the boat that will hold thru anything. Heck it's heavy enough that it could work as a deadweight anchor in calm conditions. The only trick to this is that it pretty much requires an electric windlass, without one you would need to stick with a traditional system. But amazingly enough not a huge windlass, the Lewmar 1000 would easily handle this system.

Evan assuming you wanted to keep a completely separate anchor for some reason, switching to 1/4 G70 chain alone would save enough weight that you could switch to twin 120lbs anchors and still save weight.


Just as a btw, Steve Dashew on Windhorse (a 78' powerboat uses a 120lbs Ronca on 3/8 G70 chain).
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post #64 of 84 Old 11-11-2013
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Re: Caternary & Chain...

Quote:
Originally Posted by Stumble View Post
This whole issue is one that has gotten some conversation on another forum, and I still stick by the fundamental premise I came to there which is that. "Pound for pound, additional weight in the anchor increases holding power faster than weight in the chain." Assuming this premise is true, and there is a lot of justification to believe that it is, then best practice would be to move as much weight from the chain to the anchor as possible.

In reality most cruisers carry anchoring systems that were designed decades ago when electric windlasses were expensive and very rare. With modern handling equipment the small anchor + lots of chain model, is incredibly inefficient requires carrying a huge amount of excess weight and provides minimal holding power. All in all this system is really due for a rethink.

Modern anchors generally create 40lbs of holding power or more for every pound of dead weight they have. While chain generates about 1lbs of holding power for every pound of weight. This massive difference is because modern anchors are incredibly efficient at converting their weight into holding power, while chain really adds nothing but dead weight.

So when we consider the 'average' anchoring system on a 40' cruiser what do we find? Typically a 60lbs primary anchor and 300' of 3/8BBB chain weighing in at 1.7lbs/foot. Then a secondary anchor of a slightly smaller size and the same amount of chain used to increase holding power in storms. A perfectly reasonable and reliable system... Until you consider that when it's all added up this system comes out to 1,070lbs of chain and 120lbs of anchor. Even while we know that anchor weight is much more important that chain weight.

Instead of this, my recommendation is to
1) get rid of the second anchor entirely, saving over 500lbs in weight alone
2) switch from 3/8BBB to 1/4 Grade 70 chain which will save 290lbs
3) Get rid of the 60lbs anchor and get a 120lbs one

All in all this saves 725lbs of weight from the bow of the boat, puts the weight where it matters the most, and puts an anchor on the boat that will hold thru anything. Heck it's heavy enough that it could work as a deadweight anchor in calm conditions. The only trick to this is that it pretty much requires an electric windlass, without one you would need to stick with a traditional system. But amazingly enough not a huge windlass, the Lewmar 1000 would easily handle this system.

Evan assuming you wanted to keep a completely separate anchor for some reason, switching to 1/4 G70 chain alone would save enough weight that you could switch to twin 120lbs anchors and still save weight.


Just as a btw, Steve Dashew on Windhorse (a 78' powerboat uses a 120lbs Ronca on 3/8 G70 chain).
I agree with everything you posted except that Steve's main anchor on Windhorse was a custom 250 lb Rocna. "Was" because Windhorse was sold and he is working on a 97' powerboat currently. His ideas are worth listening to because he has more "real world experience" than anyone on this or any other forum.

Most boats out there above 40' or even smaller have a windlass in any case and all that is required is changing the gypsy to fit the lighter stronger chain.

Brian
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Last edited by mitiempo; 11-11-2013 at 10:47 PM.
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post #65 of 84 Old 11-11-2013
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Re: Caternary & Chain...

I'd love to see a picture of that 40 footer with two 120 lb hooks hanging on the (hopefully heavily modified) bow roller :-))

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post #66 of 84 Old 11-11-2013
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Re: Caternary & Chain...

Quote:
Originally Posted by jrd22 View Post
I'd love to see a picture of that 40 footer with two 120 lb hooks hanging on the (hopefully heavily modified) bow roller :-))
He posted " get rid of the second anchor". As far as looks, remember the quote "when others start laughing at the size of your anchor you are getting close".

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post #67 of 84 Old 11-11-2013
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Re: Caternary & Chain...

Quote:
Originally Posted by mitiempo View Post
I agree with everything you posted except that Steve's main anchor on Windhorse was a custom 250 lb Rocna. "Was" because Windhorse was sold and he is working on a 97' powerboat currently. His ideas are worth listening to because he has more "real world experience" than anyone on this or any other forum.

Most boats out there above 40' or even smaller have a windlass in any case and all that is required is changing the gypsy to fit the lighter stronger chain.
WOOPS, good catch, thanks. I am leaving as is for posterities sake.

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Last edited by Stumble; 11-11-2013 at 11:48 PM.
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post #68 of 84 Old 11-11-2013
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Re: Caternary & Chain...

Quote:
Originally Posted by jrd22 View Post
I think what is missing in this discussion about all chain or chain/rope is that the lighter chain/rope will be a straight line to the anchor, and therefore starting to lift the shank, in much less wind than the all chain.
Late to this party, but I think what's missing in this discussion is that the moment you back down hard on the anchor to set it, you've got all the chain off the bottom and are lifting the shank already.

All this "new research" seems to indicate to me is that with all-rope rode or with little scope, the anchor *might* break out at lower wind forces than might have otherwise been assumed due to the shank starting to lift earlier than expected.. but again, if the anchor is breaking out because the shank is starting to lift, then maybe it wasn't set (backed down on) properly in the first place?

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post #69 of 84 Old 11-11-2013
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Re: Caternary & Chain...

Quote:
Originally Posted by Stumble View Post
...The only trick to this is that it pretty much requires an electric windlass, without one you would need to stick with a traditional system.
Love your post and have a question...

If the system weighs less, why would it require an electric windlass more than the traditional (heavy chain) system?

You are lifting less chain weight as it hangs off the roller and down to the bottom, which makes up for the heavier anchor, unless you are in shallow water.

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Re: Caternary & Chain...

Quote:
Originally Posted by Bene505 View Post
Love your post and have a question...

If the system weighs less, why would it require an electric windlass more than the traditional (heavy chain) system?

You are lifting less chain weight as it hangs off the roller and down to the bottom, which makes up for the heavier anchor, unless you are in shallow water.

Regards,
Brad
Huge anchors quickly outstrip the ability of someone to lift without assistance. Most of us can manhandle a 60lbs anchor into a roller if we had to, not many of us can lift a 120lbs anchor without significant mechanical advantage.

Greg Rubin
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Last edited by Stumble; 11-12-2013 at 12:23 AM.
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