Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 16-06-2006, 01:04   #1
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Stainless Anchors and Chain

Just out of interest, does anyone have any stainless anchoring gear on their boat? and why did you pick that over Galv.?
__________________

__________________
GMac is offline   Reply With Quote
Old 16-06-2006, 01:43   #2
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 would nhever ever use SST Chain. Never ever trust SST fittings underwater.
I have a SST anchor, but that is only becuase it was cheap for me to build. I can't easily nor cheaply get anything Galved here. It has to be sent away.
The anchor is meaty enough not to have issue that fittings like shackles and swivels do. Chain is natoriousely bad underwater. The welds will eventually fail and your chain will fail when you have greatest need.
__________________

__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 16-06-2006, 07:58   #3
Registered User

Join Date: Apr 2006
Posts: 4,413
Underwater?

Alan I am not sure what you really mean. Most anchor gear is set and retrieved and not used for permanent mooring. I can be inspected and SS chain is certified for a load why can't you trust this figure?

You boat has other stainless gear which is exposed to the elements including salt spray and stainless is used for rigging regularly.

There is the issue of using dissimilar metals and "galvanic" corrosion, but even this would be if the metals are continuously in close contact... as in stainless screws in aluminum masts.

The caution you not makes it sound like if you had a stainless anchor down one day, the wind would pipe up and the anchor would fall apart. I seriously doubt this.

Can you site any examples of catastrophic failures and the circumstances associated with use of stainless steel anchor gear?

Jef
sv Shiva
Contest 36s
__________________
Sandero is offline   Reply With Quote
Old 16-06-2006, 12:37   #4
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,076
Images: 6
Crevice and pitting corrosion in stainless steel

Hello Jef, I agree with Wheels in that stainless anchoring gear should be avoided whenever possible. Because this is a cruising forum we are dealing with cruisers who may anchor for several days to weeks in bottoms that are comrised of anything from pristine coral sand to clay polluted with chemicals from adjacent land runoff.

As Wheels points out, the welds on stainless chain have not been "relieved" or passivated from the welding process (it would be quite expensive on top of the already expensive material). These welds will develop crevice corrosion relatively quickly (days) under water and cannot easily be inspected (are you going to look at every link after raising anchor?).

The main point is that stainless is EASILY destroyed when buried in oxygen-starved bottoms. The people who have brightly shined stainless anchors just have not yet anchored in a nasty bottom for more than a day or so but if they do they are in for a nasty surprise.

I have dived for parts many times for people who lost them overboard. In some bottoms ONE WEEK caused sever pitting of the stainless steel which was embedded in the bottom. You could see a distinct line on the stainless above where the bottom contacted the metal. On one side (which I could first see when finding the part) it looked brand new, upon pulling out the part from the bottom you could not believe the destruction that can happen. Good quality anchors and chain do not suffer the same problem in the oxygen starved bottom materials and corrode much more slowly in contaminated bottoms.

In short, stainless steel does not belong below the waterline if another material is available to mechanically perform the function. What you see in terms of the advantages of stainless steel, especially 316L, is that in the presence of salt SPRAY they hold up very well because there is oxygen all around all of the time to allow a continuous surface oxide layer to exist protecting the alloy beneath. You can't see it but it is there.

Good bronze alloys and Marelon are superior to surviving in oxygen-starved water. Many people have been in "dead water" for sometime only to discover that their stainless steel prop shafts have pitted in the area of the cutlass bearings where the water could not get oxygen. This is not unusual.
__________________
Rick is offline   Reply With Quote
Old 16-06-2006, 14:38   #5
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 have searched, but can't find the photo anywhere. I am sure it was someone from here, that has a photo of SST chain that had failed at every single link, due to failure of the weld joint. The chain looked fine till it was put under a load and it failed. The most shocking was it wasn't just one link, it was all of them. Not that that would have made any difference to the possible conclusion.
After you see this photo, you would never want to rely on SST chain underwater again.
As for shackles and swivels, I have personaly seen these fail. The big danger with SST is that it looks great right up to the point of letting go.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 16-06-2006, 15:57   #6
Registered User

Join Date: May 2005
Location: Pennsylvania
Boat: Tayana 37, M-20/I-20 Scow
Posts: 250
Stainless, besides all the corrosion problems in seawater, is a BAD metal versus fatigue resistance. Fatigue begins whenever the stainless is brought to and over 1/3 of its ultimate tensile/yield strength. So, in that respect normal stainless needs to have 3 times the cross section (3 times the weight) to do the same job of what you want it to do. Stainless to avoid the fatigue problem should be designed to 30000 psi stress, well below it 90000 psi yeield/ultimate tensile strength.

BTW the fatigue sites / micro cracks are 'wonderful' sites for crevice corrosion to begin --- double whammy.

Of course if you want to spend the gross national product of Australia and New Zealand, you could consider to use annealed monel or nickle-aluminum-bronze chain and anchor.
__________________
Richhh is offline   Reply With Quote
Old 16-06-2006, 16:15   #7
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,596
Images: 240
Alan:
I believe the stainless failure photos were of a permanent mooring; which,
Notwithstanding RichH & Rick's accurate warnings - is not quite the same as an anchor assembly (per defjef).
How about a really big anchor, in relatively light Titanium?
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 16-06-2006, 16:21   #8
Moderator Emeritus
 
Pblais's Avatar

Join Date: Mar 2003
Location: Hayes, VA
Boat: Gozzard 36
Posts: 8,700
Images: 15
Send a message via Skype™ to Pblais
Quote:
How about a really big anchor, in relatively light Titanium?
Probably worth stealing. A fortrsss style anchor in TI might not be a bad idea. paying for it would be the problem.
__________________
Paul Blais
s/v Bright Eyes Gozzard 36
37 15.7 N 76 28.9 W
Pblais is offline   Reply With Quote
Old 16-06-2006, 16:53   #9
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,596
Images: 240
Using technology developed at MIT, 4-person startup, Avanti Metal Company, hopes to reduce the cost of producing Titanium from the current $40 per pound to a mere $3. They have already identified an aluminum smelter manufacturer who will design and mass produce Sadoway process titanium smelters, with a target production date of August 2008.
http://www.technologyreview.com/read....aspx?id=16963
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Old 16-06-2006, 17:37   #10
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
Interesting, because someone here in NZ has been looking into it as well. Titanium is in quite a high percentage in our Black Iron sands on the west coast.
I should add though, the cost is not just in the getting the stuff, it is the difficulty in making it and in working with it. It has a tremendousely high melting point, but till has to be kept safe from oxygen till it has cooled to below 800 C.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 16-06-2006, 19:34   #11
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
Gord was right, the chain Wheels is think of was on a permanent mooring, a bloody stupid thing to do. As were a lot of the shackle photos.

Not knowing SS qualities to well - on Stainless does this thoery stack up? If you have a high grade Duplex stainless chain the fatigue issues may not be there?, assuming no overloading is taking place.

Is, say, a SS 10mm G50 Duplex chain going to be an issue if replacing G30 steel (G50 being 50% stronger than G30), talking fatigue here. Extended submersion is a well known issue as is the $$'s involved.

There is masses of SS anchoring gear out there and we don't here of any more dramas than steel. 95% of SS shackles and the like are all Asian now so it is not quite compearing apples with apples with what many would have been used to i.e EU or USA made product.

You are scared of SS and want to use Titanium, Errr.... that does not stack up. I'd use SS over Titanium any day purely for safety reasons alone. Titanium failures in yachts is very common. More probably 'very very very' common when you take into account the very small number who use it.

So to date I'm the only one with SS anchor chain on to a Alloy anchor. Bet that has one or 2 getting a cold shiver down the spine . It is used purely because of the 'Bling factor' and 'because I can' . 31ft yacht with a 6mm anchor rope would have ya twitching as well, better not mention I have that either . Total anchor and rode weight combined is 7.2kg (16lb). It races often and the 'crusing anchor system' is a tad differant . One small bonus of having 10 tonnes of anchors and 50 odd of chains and 20 odd of ropes sitting next to me
__________________
GMac is offline   Reply With Quote
Old 16-06-2006, 20:37   #12
Registered User

Join Date: Jan 2005
Location: Seattle area (Bremerton)
Boat: C&C Landfall 39 center cockpit "Anahita"
Posts: 1,076
Images: 6
nickle-aluminum bronze question

Richhhh raises the question of a better alloy, nickle-aluminum-bronze. I am not famaliar with the properties would someone illuminate us?

The question of using titanium is fraught with the problem of the low specific gravity (not a good thing for anchors or chain) as well as the very tight corner of the stress-strain curve before yielding to failure (yes, it has an advantage of having a relatively good tensile strength as compared to stainless) as well as to the ability to easily weld or machine the material (not good).

Given a cruiser's budget I don't believe that this string is contributing any usefule info other than to stay with the usual galvanized steel, think about it!
__________________
Rick is offline   Reply With Quote
Old 16-06-2006, 23:35   #13
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
Nah what I was getting at wasn't that it was a fatigue issue. The welds had failed because of Galvanic corroison, NOT crevice corrosion. It's common in SST under water. Welds can not be totally 100% the same right through and certainly not 100% the same as the parent metal it is fused to. This is one main reason why 316L is used is marine applications. 316 has low carbon content. Carbon and chrome react with one another when heated in a weld and will cause chemical changes that make it different just enough to cause galvanic corrosion in the right situations. It doesn't really matter if the chain in the photo was mooring or anchor, as soon as it goes under the water, the action starts. Eventually the weld will fail. As a mooring chain, it just happend sooner.
Many mooring chains are just plain steel. No galv. Steel actually takes quite sometime to be corroded away under water. There is not enough oxygen. Galv would be no good for mooring as the galv will act like an anode and disappear quickly.
As for anchor chain, as Rick said, Galv is the most practicle for us crusiers and our budgets.
__________________
Wheels

For God so loved the world..........He didn't send a committee.
Alan Wheeler is offline   Reply With Quote
Old 16-06-2006, 23:59   #14
Marine Service Provider
 
GMac's Avatar

Join Date: Oct 2005
Location: North of the Bridge, thankfully
Boat: R930
Posts: 1,659
I know what happens to SS, I've seen lots of it. Only ever seen one nasty bit off an anchor chain though. 10mm to 2mm odd in 6 months, mind you it was stored in an carbon fibre locker lying right on the carbon. Did I hear someone say 'Battery'. Chain replaced, locker lined and 4 year later still going fine.

Galvanised chains used on mooring quite often won't last as long as plain old self-colour (black, naked, whatever). The galv starts to fizz as it is designed to do but the tiny current is still there when it runs out and it continues to chomp the steel.

Most crusiers have a budget so most use galv. Makes sense to me.

I was more just wondering if anyone here had any and why did they choose that over galv. Some crusiers do have it or bits of anyway. We are getting asked more and more for it. Seems 'keep the deck clean' is a common reason. Personaly I'm too tight and would only spring for a scrubbing brush :-), if I didn't have such a handy supply :-)
__________________
GMac is offline   Reply With Quote
Old 17-06-2006, 04:52   #15
Moderator Emeritus
 
GordMay's Avatar

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 31,596
Images: 240
Gmac:
I wonder if the high failure-rate of Titanium fittings might be due to the prevalence of Ti use on weight sensitive racing boats.
In these applications the Ti parts may be “lightly” engineered, in order to save weight; rather than for robust strength.
I too, have used a SS “leader” thimbles & shackles (on both Alum Fortress & Steel Delta) to keep my foredeck clean & “pretty”.
Rick:
Cruising a 28.5 footer, I’ve never had the luxury of all chain road (weight). A lighter than steel; but heavier (& more chafe-resistant) than rope compromise might be attractive.
__________________

__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"



GordMay is offline   Reply With Quote
Reply

Tags
anchor

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
Heavy weather anchoring, Stede General Sailing Forum 105 10-12-2008 11:11
how do you set up your anchor rode? Ram Anchoring & Mooring 48 01-05-2008 02:05
CQR Anchors ssullivan Anchoring & Mooring 79 12-12-2006 07:43
Anchors and Anchoring Sonosailor Anchoring & Mooring 3 17-03-2004 11:25



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 10:40.


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.