Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 18-04-2012, 00:10   #226
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by Bash View Post
That's crap. Ship rodes and yacht rodes are chain for the same practical reasons.

That's also physics.
I'll simply quote a study that's far more authoritative:
"This way of doing things has been reinforced over thousands of years, mostly with relatively large vessels, and has built a strong tradition. Ships from all eras have used very heavy chain, and relatively small and ineffective anchors. This for the most part works well. Unfortunately, the relevant factors do not scale down evenly to smaller boats such as today’s cruising and pleasure yachts. In fact, the best way to anchor a toy boat in the garden pond is with a relatively large toy anchor and a rode consisting entirely of an elastic line. Between this extreme and that of large ships, a compromise needs to be found.

Recognizing that a small boat is not a ship is the first step. While ships have massive inertia and waves/swells do not normally bother them, a yacht or motor-boat is subject to comparatively violent surge, and winds which are very high on a relative basis. As such the forces are relatively higher, and on the other hand small boats can carry anchors which are, for the size of boat, quite large. If a 10 m yacht carries a 15 kg anchor, this anchor scaled to fit a large container ship would simply be too massive to be practical.

It is then important to critically examine the mathematics of the catenary curve of a boat’s chain to investigate its true usefulness to a small boat. As the above “old way of thinking” is commonly adhered to, it is a widespread myth that all boats should carry as much chain as possible – and the heavier the better.

In fact, we shall see that catenary rarely offers much benefit which is truly worthwhile, and any unnecessary extra weight of the chain is often far better invested in other elements of the anchoring system."
Assuming that your vessel at 1/1000th the mass of a container ship is subject to similar relative environmental forces is simply absurd. Maybe in a mill pond on a windless day, but not in conditions we are talking about. The relative forces in play for small boats is radically different than it is for large vessels and the strategy needs to adapt accordingly.

Not to mention it would be impractical to moor a 220,000 ton container ship with nylon braided rode.

Physics is physics, but different factors come into prominence at different scales when environmental factors are the constant.
__________________

__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 00:43   #227
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by wolfenzee View Post
At present I carry 300' of chain (also 250' of rode w/25' of chain) ...scope I use depends on the bottom, weather and anchor, useually I use a 22 lb. Bruce primary anchor, but also have a 20 lb CQR and 45 lb Forfjord (and 15 lb northill I run off the stern when anchored in a river as a seconond anchor).
That's at least 502 lbs if the bruce is on the roller (assuming 3/8 chain). All that weight concentrated in the bow of your boat, assuming the rest of the rode is either weightless or stowed elsewhere along with all those other anchors).

Imagine what that does to your pitching moment in 10' seas. No thanks. Not even in my 20,000 lb boat. Downwind in big waves I want all the buoyancy forward I can get and I'm not going to schlep 400+ lbs of anchor chain every time it threatens to blow a little.

With a heavier anchor stowed properly amidships, 25-60 feet of chain stowed low, 12 feet aft of the bow, and a couple hundred feet of brait I've got a bullet proof anchoring system I can deploy in seconds and I'm not destroying the performance or sea keeping capabilities of my yacht.

It's worth thinking about.
__________________

__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 01:20   #228
Eternal Member
 
wolfenzee's Avatar

Join Date: Feb 2008
Location: Port Ludlow, WA (NW corner of Puget Sound)
Boat: 30' William Atkin cutter
Posts: 1,496
Send a message via ICQ to wolfenzee
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by JoeFish View Post
That's at least 502 lbs if the bruce is on the roller (assuming 3/8 chain). All that weight concentrated in the bow of your boat, assuming the rest of the rode is either weightless or stowed elsewhere along with all those other anchors).

Imagine what that does to your pitching moment in 10' seas. No thanks. Not even in my 20,000 lb boat. Downwind in big waves I want all the buoyancy forward I can get and I'm not going to schlep 400+ lbs of anchor chain every time it threatens to blow a little.

With a heavier anchor stowed properly amidships, 25-60 feet of chain stowed low, 12 feet aft of the bow, and a couple hundred feet of brait I've got a bullet proof anchoring system I can deploy in seconds and I'm not destroying the performance or sea keeping capabilities of my yacht.

It's worth thinking about.
In a 10' sea the boat goes through the wave with the spray pushed off to the side. Actually the bow on my boat has a lot of flair(see below), the purpose of this extra bouyancy is to keep the cockpit dry...this has a tendancy to make the boat a bit "saucy"...this is counteracted by the wieght of the chain, balnce diffrance is counteracted with a heavier engine. She still sits at her deasign waterline perfectly level (bulkheads are bubble plumb). Spare anchors are lashed to the boom gallows.

__________________
"It is better to die living than live dieing" (Tolstoy para-phrased by Jimmy Buffet)
"Those who think they know everything piss off those of us who do"
wolfenzee is offline   Reply With Quote
Old 18-04-2012, 01:57   #229
Eternal Member
 
wolfenzee's Avatar

Join Date: Feb 2008
Location: Port Ludlow, WA (NW corner of Puget Sound)
Boat: 30' William Atkin cutter
Posts: 1,496
Send a message via ICQ to wolfenzee
Re: Chain Versus Rope Scope ?

If your boat is the "Sparkman & Stephens, Design 1068 Nevins Yawl" Sparkman & Stephens: Design 1068 - Nevins Yawl or something close (as your specs seem to suggest) I can see why you stow your anchor and ground tackle as you do...but we have different boats.
__________________
"It is better to die living than live dieing" (Tolstoy para-phrased by Jimmy Buffet)
"Those who think they know everything piss off those of us who do"
wolfenzee is offline   Reply With Quote
Old 18-04-2012, 02:40   #230
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by wolfenzee View Post
If your boat is the "Sparkman & Stephens, Design 1068 Nevins Yawl" Sparkman & Stephens: Design 1068 - Nevins Yawl or something close (as your specs seem to suggest) I can see why you stow your anchor and ground tackle as you do...but we have different boats.
Yes, that's it, but pitching moment is pitching moment. What makes you "see why I stow the anchor and rode where I do?" The performance speaks for itself on any boat when you centralize mass.

Bringing that mass more central is not going to do anything other than improve your boat's sailing performance so long as you maintain proper trim.
__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 02:59   #231
Registered User
 
Strait Shooter's Avatar

Join Date: Aug 2010
Location: Straits of Juan De Fuca
Boat: Ingrid
Posts: 786
Re: Chain Versus Rope Scope ?

Great discussion!
Thanks everyone!

Would an all chain rode with a long nylon bridle not be ideal? Barring of course the weight distribution issue which is really more about boat design and getting the weight low and back.
__________________
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
Strait Shooter is offline   Reply With Quote
Old 18-04-2012, 03:06   #232
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by Strait Shooter View Post
Great discussion!
Thanks everyone!

Would an all chain rode with a long nylon bridle not be ideal? Barring of course the weight distribution issue which is really more about boat design and getting the weight low and back.
Did you read the article? If not, I'll paraphrase the author (designer of the Rocna anchor):

It is then important to critically examine the mathematics of the catenary curve of a boat’s chain to investigate its true usefulness to a small boat. As the above “old way of thinking” is commonly adhered to, it is a widespread myth that all boats should carry as much chain as possible – and the heavier the better.

In fact, we shall see that catenary rarely offers much benefit which is truly worthwhile, and any unnecessary extra weight of the chain is often far better invested in other elements of the anchoring system...

The catenary from the chain is often assumed to be a good shock absorber, in addition to lowering the angle of pull on the anchor, as it takes some time to straighten. However, this is a fallacy, as this quasi “spring” disappears in bad conditions when it is most needed....


Sufficient length is required to get any measurable shock absorption from brait type rode.

The quote above is selective and I'd encourage you to read the article and evaluate your requirements based on a number of the factors mentioned therein. If you're n Patagonia your needs will be different than the Bahamas. There is no single right answer, only general rules (as in life).

As mentioned, I favor brait with a short length of chain (25-60 ft) and adjust depending on conditions and depth.

A means of sampling the bottom is also a good addition to your anchoring kit.
__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 03:16   #233
Registered User
 
Strait Shooter's Avatar

Join Date: Aug 2010
Location: Straits of Juan De Fuca
Boat: Ingrid
Posts: 786
Re: Chain Versus Rope Scope ?

I did read the article. It's o.k. with you if I question or disagree isn't it? I don't usually blindly follow anyone or anything.

So explain to me why you feel a chain rode with a long nylon bridle is bad. You didn't do that, you sound like you're kinda blindly following a specific article.

I'm just asking a question.
__________________
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
Strait Shooter is offline   Reply With Quote
Old 18-04-2012, 03:21   #234
Registered User
 
Strait Shooter's Avatar

Join Date: Aug 2010
Location: Straits of Juan De Fuca
Boat: Ingrid
Posts: 786
Re: Chain Versus Rope Scope ?

So if you have an all nylon rode, maybe some chain on the end and it parts because of chafe or whatever in nasty conditions, you wouldn't like to have a chain attaching your boat to the bottom?

What's so wrong with having the best of both worlds?
__________________
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
Strait Shooter is offline   Reply With Quote
Old 18-04-2012, 03:29   #235
Registered User
 
Strait Shooter's Avatar

Join Date: Aug 2010
Location: Straits of Juan De Fuca
Boat: Ingrid
Posts: 786
Re: Chain Versus Rope Scope ?

Just because he's the "designer of the Rocna anchor" (fan fair and rose petals) doesn't mean he's the all knowing answer guy does it?

I work with lots of engineers and designers and am not as easily impressed perhaps.

A physicist? I use heavy chain, cable and rope to move big heavy things on a daily basis, not on paper. If I put you a 1,000 feet in the air on your 20,000 lb boat and started bouncing you up and down I bet you'd think a little differently as to what you think you need.
__________________
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
Strait Shooter is offline   Reply With Quote
Old 18-04-2012, 03:30   #236
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

One reason is I got the same advice from Olin Stephens when I asked him years ago and I trusted his expertise.

Another reason is I have used this technique in locations ranging from the Sea of Cortez to the Bahamas, Bermuda to Maine, Greece to Sweden, the Pacific Northwest and I have yet to have any problem. I've ridden out tropical storms with 8:1 using only 60 feet of chain and never dragged my anchor.

However it's worth noting that I own 5 different anchors and I usually have two on the boat most suited to the area I'm sailing in.

Typically I have a Bruce and a Danforth style (Fortress) for almost all areas. I have a small yachtsman I use as a lunch hook, and a larger one I rarely use (it may be the original anchor on the boat). Both collapse and I've used them with success.

I also have a CQR but I have not used it in ages. I plan to sell it and replace it with a Rocna at some point in the future as I'm inrtigued by the design. It could replace the Bruce, but we'll have to see.

The Bruce and the Fortress are larger than suggested (66 and 47 lbs.)

As others advised me, I put the weight into the anchor, not the rode.

The point of rode elasticity is to reduce peak loading on the anchor which may rip it from the bottom and to reduce loading on your deck hardware. It's a very different objective than you have when lifting things.
__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 03:33   #237
Registered User
 
Strait Shooter's Avatar

Join Date: Aug 2010
Location: Straits of Juan De Fuca
Boat: Ingrid
Posts: 786
Re: Chain Versus Rope Scope ?

Quote:
Originally Posted by JoeFish View Post
One reason is I got the same advice from Olin Stephens when I asked him years ago and I trusted his expertise.

Another reason is I have used this technique in locations ranging from the Sea of Cortez to the Bahamas, Bermuda to Maine, Greece to Sweden, the Pacific Northwest and I have yet to have any problem. I've ridden out tropical storms with 8:1 using only 60 feet of chain and never dragged my anchor.

However it's worth noting that I own 5 different anchors and I usually have two on the boat most suited to the area I'm sailing in.

Typically I have a Bruce and a Danforth style (Fortress) for almost all areas. I have a small yachtsman I use as a lunch hook, and a lager one I rarely use (it may be the original anchor on the boat). Both collapse and I've used them with success many times.

I also have a CQR but I have not used it in ages. I plan to sell it and replace it with a Rocna at some point in the future as I'm inrtigued by the design.

The Bruce and the Fortress are larger than suggested (66 and 47 lbs.)

As others advised me, I put the weight into the anchor, not the rode.

And again, my question is, why not both?
__________________
"Waste your money and you’re only out of money, but waste your time and you’ve lost a part of your life.” (Michael Leboeuf)
Strait Shooter is offline   Reply With Quote
Old 18-04-2012, 03:45   #238
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

1) simplicity
2) necessity

I see good reason for #1.

I do not see where #2 has greater importance than #1 when there is no evidence #2 will outperform #1. If you can produce a series of real world tests where both provide better performance than the simpler solution then you will have your answer.

Smarter people than I gave me this advice years ago. I listened to them and I have yet to have reason to doubt their advice. Until I have a reason to suspect their advice is flawed or see evidence that some other strategy yields better performance I can't see any reason to adopt new tactics.
__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 03:57   #239
Registered User

Join Date: Mar 2012
Posts: 153
Re: Chain Versus Rope Scope ?

I should add that no one has given any evidence beyond the subjective that all chain rode is in any way superior. In fact, there's plenty of data out there to contradict that assertion given proper set of the anchor (a poorly set anchor might be one case where all chain is superior, but that also has yet to be proven).

While there's plenty of historical precedent with larger craft and all chain rode, it's been pretty convincingly proven that smaller vessels have different dynamic requirements for their anchoring systems.

If there is a study that shows any more conclusively that all chain is better and offsets the obvious weight and stowage problems then I'm more than willing to consider it, but I don't see anything out there that meets any kind of reasonable evidentiary requirement at the moment.
__________________
JoeFish is offline   Reply With Quote
Old 18-04-2012, 05:03   #240
Don't ask if you can't handle it
 
sailorboy1's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: On the boat somewhere
Boat: Hunter 410
Posts: 12,311
Re: Chain Versus Rope Scope ?

I have an over-sized anchor and 340' of chain (with some rope to attached it to the boat), and 30' rope snubber. The weight of the anchor and all that chain to my boat isn't worth worrying about! If you have older sea-saw designs maybe you have to consider things different.

You can spin any story anyway you want. But you never are going to convince me that an over sized anchor, all chain rope, and good snubber setup is not the best way to go!


I've read these threads for years. And I've read other articles by "experts" being quoted here on the thread where they made the "don't use all chain" option. But in those articles they still normally recommend 3 times the boat length in chain, which for most anchorages in effect becomes all chain.

PS - just how long a snubber do you have to have before the all chain "downside" is gone.
__________________

__________________
jobless, houseless, clueless, living on a boat and cruising around somewhere
sailorboy1 is offline   Reply With Quote
Reply

Tags
scope

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
BBB vs High-Test Chain wind rose ll Anchoring & Mooring 75 27-06-2012 12:30
Getting Chain into the Bilge JonathanSail Anchoring & Mooring 32 15-01-2012 17:22
For Sale: 3/8" SS chain and gypsy for sale terry1 Classifieds Archive 0 14-12-2011 14:55
Windlass Chain Sleeve Cover sailorboy1 Anchoring & Mooring 3 20-09-2011 15:49
Galvanic Corrosion of Chain Galvanizing wsmurdoch Anchoring & Mooring 0 22-08-2011 12:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 20:03.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.