Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 24-04-2008, 00:50   #16
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Nope you're both wrong, sort of.

It is extremely exceptionally unlikely a rode with rope in it will be able to turn an anchor. But an all chain rode could. Again it is exceptionally unlikely especially in a boat of Nimbles size, actually I'd say it has a complete zero chance but Murphy's Law would undoubtedly prove that wrong.

On a bigger boat with an already existing twist in the chain and real nasty weather I could see chain being able to twist an anchor but you'd probably never notice it and it would only turn a couple of times max before stopping. Again highly unlikely but possible. It doesn't take that many rotations to lock a chain up and once it's there you pretty much have a solid rod.

Chain makes no difference to how an anchor will set? We fancy that, all these years of actually adding chain and getting both vastly improved setting and holding of anchors must just have been pure flukes. We better stop guessing then and all the owners we have sorted better stop lying by saying the problems went away, naughty naughty all of us.

Swivel with only 6mts of chain and generally shallow water = I wouldn't bother myself either.

Coastguard That the same one that has had to rescue some of their own boats for what? Running out of fuel Saw one 3 weeks ago towing another one home, it lives next door to one of my boats. I'm sorry but even as they are great people with great intentions any good knowledgeable boatie doesn't run out of fuel especially when they are supposed to be the rescuer. They should take their flags down when doing that, such a poor look.
__________________

__________________
GMac is offline   Reply With Quote
Old 24-04-2008, 01:38   #17
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
Twisting is certainly an issue with 3 core rope. Tie a length of say 50 to 100m between two 4WD and pull and you will see it spin. Can it lock up chain? Absolutely. I learn't this in other situations outside of boating. Mainly pulling big Trees on the Farm. A Taught three core rope will twist up a chain and turn an entire trunk over. Waaay more resistance than any anchor can give.
But OK, your the experts in this feild. So I won't argue the point, I'll concede.
__________________

__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 24-04-2008, 14:39   #18
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Nothing to concede, you're right but I very much doubt any boat could put those loads on a rope even in real extreme stuff as they are unlikely to chain as well.
__________________
GMac is offline   Reply With Quote
Old 24-04-2008, 14:51   #19
Registered User
 
Nimble1's Avatar

Join Date: Feb 2007
Boat: Nimble Nomad Trawler
Posts: 41
Images: 4
Wow!!

This got a little more technical and heated than I ever thought it would.Seriously thanks for all the replies and thought that went into your answers. There is obviously a great wealth of knowledge contained on these forums.
Thanks,
__________________
Tom Nowling
Nimble Nomad Trawler
"Sweet Pea" Hull #1
Nimble1 is offline   Reply With Quote
Old 24-04-2008, 14:55   #20
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Not heated, more just vigorous
It's something to do with anchors, it always happens but hopefully everyone learns a little more each time.
__________________
GMac is offline   Reply With Quote
Old 24-04-2008, 15:53   #21
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Posts: 1,594
I believe that the 'experts' recommend 1 foot of chain for every foot of boat. Maybe WL. More can't hurt, except maybe your back. It helps to keep the rode from rubbing though on bottom debris and helps by increasing the catenary.

[edit]Anchoring of marine vessels
The catenary form given by gravity is made advantage of in its presence in heavy anchor rodes which usually consist mostly of chain or cable as used by ships, oilrigs, docks, and other marine assets which must be anchored to the seabed.
Particularly with larger vessels, the catenary curve given by the weight of the rode presents a lower angle of pull on the anchor or mooring device. This assists the performance of the anchor and raises the level of force it will resist before dragging. With smaller vessels it is less effective[8].
The catenary curve in this context is only fully present in the anchoring system when the rode has been lifted clear of the seabed by the vessel's pull, as the seabed obviously affects its shape while it supports the chain or cable. There is also typically a section of rode above the water and thus unaffected by buoyancy, creating a slightly more complicated curve.
__________________
Randy

Cape Dory 25D Seraph
rtbates is offline   Reply With Quote
Old 25-04-2008, 14:10   #22
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
We tend to run a minimum of 1.5 times the length of the boat down here. But then we do tend to anchor in places a bit more demanding than many.

Yeap, the more chain your boat has to move the less work your anchor has to do and the smoother the ride.
__________________
GMac is offline   Reply With Quote
Old 25-04-2008, 14:31   #23
Senior Cruiser
 
44'cruisingcat's Avatar

Cruisers Forum Supporter

Join Date: Sep 2006
Posts: 7,454
Images: 69
Quote:
Originally Posted by craigsmith View Post
Chain makes little or no difference to the setting of an anchor, and setting is certainly not its raison d'etre.
I find this very surprising. Is this the result of testing? Intuitively, chain would seem to deliver a more horizontal pull to the anchor, which you would think, would make it set faster and easier.

We added a swivel to our anchor when we were anchoring in areas where the tidal flow was strong, and changed direction with the tide. Without the swivel we found the chain was getting very twisted after a few days.
__________________
44'cruisingcat is offline   Reply With Quote
Old 25-04-2008, 18:43   #24
Senior Cruiser
 
Therapy's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: W Florida
Boat: The Jon boat still, plus a 2007 SeaCat.
Posts: 6,894
Images: 4
Quote:
Originally Posted by 44'cruisingcat View Post
I
.

We added a swivel to our anchor when we were anchoring in areas where the tidal flow was strong, and changed direction with the tide. Without the swivel we found the chain was getting very twisted after a few days.

Amazing!!

I never really thought of that.

I am like most (all) here and had "my" best setup for all my needs.

Duh!

Just have one and use if needed.

That is what I will do - have one and use when needed.

Thanks!
__________________
Therapy is offline   Reply With Quote
Old 26-04-2008, 01:22   #25
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
Quote:
Chain makes little or no difference to the setting of an anchor, and setting is certainly not its raison d'etre.
That has got to be one of the most silliest statements I think I have ever seen here. Tell me Craig, did you make that comment just because it was me you were replying to?? :-0
Of course chain has a bearing on the setting of an anchor and i certainly has a bearing on how well the anchor continues to hold.
In regards to the how much chain discussion, when I was selling chandlery, we were always told by the anchoring manufacturers that you have a 1.5x the boat length of chain before the rope rode.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 26-04-2008, 08:57   #26
Registered User

Join Date: Nov 2007
Location: Miami Shores
Boat: Endeavour E40
Posts: 261
Quote:
Chain makes little or no difference to the setting of an anchor, and setting is certainly not its raison d'etre.


WHAT ?!?

I think I'm missing something here...........

CRAIG, could you explain the purpose of CHAIN ?????

(and please don't use BIG words with us SOUTHERN BOYS !)
__________________
[SIGPIC][/SIGPIC]____________________________________________
S/V High Cotton
"Had I known I would live this long, I would have taken better care of myself !!!
AUTHOR: My dear ole MOM
High Cotton is offline   Reply With Quote
Old 26-04-2008, 19:41   #27
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Quote:
Raison d'Ítre is a phrase borrowed from French where it means simply "reason for being"; in English use it also comes to suggest a degree of rationalization, as "The claimed reason for the existence of something or someone". A raison in nature may also symbolize wisdom or knowledge.
For those like me and when reading that Craig is sort of right, chain isn't there just to help the anchor set.

Don't know about the last sentence though. I though a raison in nature was a shrivelled grape, live and learn I suppose. I must admit Craig has done wonders for my word knowledge, he's taught me lots of good ones.

Could be relatively easy to test the differences between chain only and rope only during setting. Deploy anchor and reverse at a 'set load' for both. Load would be relative to boat anchor sizing combo. Load wouldn't be that high so quite easily doable I'd say. I'll add that to the list for part 3. I'd be very surprised if chain only didn't clean up though.
__________________
GMac is offline   Reply With Quote
Old 26-04-2008, 20:33   #28
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
I could believe that rope only would be fine on a beach test. When the angle of pull is horizontal/level with the anchor. But raise the pull point to 30ft and higher(boat floating on surface) and the way the anchor sets into the bottom is completely different. Catenery action may be a big aid in shock absorbtion, but that same action is what translates the pull form above to pull down below. Also the reson why the ratios of depth to rode is used. Again, not just for shcok absorbtion, but so the actual pull comes on at a more horizontal pull to the anchor. Otherwise the anchor would pull straight up and out of the bottom.
Testing anchors on a beach from a Horizontal pull is one of my biggest bug bears. It just does not happen that way in real life. I think any anchor producer that is making a video about how well there product sets and holds, should be taking the pull point from a crane.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 26-04-2008, 21:22   #29
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Ahh but by doing a horizontal or close to test would defeat the whole idea in this case. The question is 'does rope or chain aid the setting of an anchor?' So it would need to be a real use test to get a good result.

What I would expect to happen with all rope is that it will just straighten out and put an upward pull on the anchor. How much that would affect the setting depends on the anchor and load applied. A lower load would obviously be better for the anchor. Also the rope type would have some baring I'd be thinking. A stretchy rope may see an anchor starting to set and then the 'stretched out stretch' in the rope suddenly reach a level where it pulls the anchor out again. This could be very easily doable I'd suggest in firm sandy bottoms that have the {can't think of the bloody word but the one that sort of means ripples} many do.

With all chain you first have to straighten that out before you get the same amount of upward pull angle. Some would be thinking that straightening the chain is easy and doesn't require much load, in some cases it wouldn't but in many it would take more than many think. We have done tests to see what loads it does actually take to straighten a bit of chain and they can be large. All depends on lengths and scope i.e. longer lengths of more scope the harder it becomes, which shouldn't surprise many.

So when using all chain the forces to get that 'upward pull angle' the rope got, very easily would need to be higher and in some systems that would be 'a lot' higher hence a lower attack angle for the anchor and superior setting performance.

That's the theory but as we all know anchoring theory and anchoring in real life often don't come together well at all. So lets play and see, it would be quite easy to do this one

Beach tests - yes flawed as all most every single test I've seen has been. Take the Sail one, which was one of the better but a lot of people and the odd manufacturer is basing a lot on what was just a couple of pulls, hardly representative of what most boaties do actually have to contend with. Sure they gave some indication of how the differing anchors go in that bottom type with that one specific rode but I'd sure as hell not be basing my entire decision of those and I'd suggest anyone who does is plainly crazy and new to boating. I'd go as far to say that if that test was replicated today by a differing group of people we would see differing results.

The only real test is the the fleet actually using them. But saying that beach tests and most tests can be good for finding out certain aspects of the whole subject. The Rocna tests, for example, did have about a 8:1 scope which is more than most use but by using so much that did actually give an advantage to some of the older designs and even then some didn't do well. And with such a large scope it was giving 'what is possible' numbers rather than the lower numbers people are actually getting in everyday use with lower scopes. One of those 'you're using only XX% but YYYkg is there if required', sort of things. As FYI - Manson do use a big crane but then that is what Lloyds wants and over a certain size they use a big red tugboat. We use a little green one but then aren't towing 2000kg anchors.
__________________
GMac is offline   Reply With Quote
Old 27-04-2008, 03:30   #30
Senior Cruiser
 
Alan Wheeler's Avatar

Cruisers Forum Supporter

Join Date: Dec 2003
Location: Marlborough Sounds. New Zealand
Boat: Hartley Tahitian 45ft. Leisure Lady
Posts: 8,038
Images: 102
Green is OK. Remember that Red is only for gaining speed, not pulling power.
__________________

__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Reply

Tags
anchor, anchoring

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
advise appreciated andreavanduyn Monohull Sailboats 19 01-01-2009 12:29
Need Some Advise bobe531 Monohull Sailboats 14 21-04-2008 13:33
product advise bill good Marine Electronics 0 02-12-2007 02:24
NEED Advise Hector Meets & Greets 6 05-06-2006 03:53
aDVISE oceaneyestoo Meets & Greets 2 24-03-2005 11:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:48.


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.