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Old 02-14-2011, 09:16 PM   #1
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Lead, galv steel and ss together in seawater??

I need to combine these metals in an anchor rode rig and think that probably some corrosive action or worse may result. What think guys?
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Old 02-14-2011, 09:34 PM   #2
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RE: Lead, galv steel and ss together in seawater??

Eric, if so, many of us are in trouble.* There are lots of stainless anchors on galvanized chain, galvanized anchors on stainless chain and stainless swivels on galvainzed chain out there.* I doubt it would be a problem...where does the lead come in?* Kellet?
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Old 02-14-2011, 09:38 PM   #3
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Lead, galv steel and ss together in seawater??

Look on the galvanic chart and see how far apart your metals are. Lead is higher on the chart that some stainless alloys. And both of them are WAY higher on the chart than zinc which I believe is usually what's used in galvanizing.

Based on the three metals you describe, I would think the first thing that will happen is the galvanizing on the steel will go away, which is kind of what it's there for, to protect the steel underneath it. Once the galvanizing is gone, the steel will start to rust in short order. The lead and stainless will remain uncompromised.* All this will happen much faster if the components are in water than if they are not, although the galvanizing will eventually go away at the point of contact between the stainless (or lead) and the galvanized steel and open the door to rust.

We experienced this last year when the chain of a mooring buoy broke while we were on it. Turned out the upper chain was stainless, the lower chain was galvanized. The galvanizing had erroded off the steel chain, the chain was badly rusted, and the link that was held by the stainless shackle finally snapped.

As an example of the considerations that have to be made, stainless steel is never used in floatplanes, particularly the float and float strut assemblies. This is because stainless is so far above aluminum on the chart. Instead, the fasteners in a float system are usually cadmium plated steel. The cad plating very slowly goes away because it is very close to aluminum on the chart. Once the cad plating is gone, however, the galvanic separation between the steel fastener and the aluminum the fastener is fastening is much greater and the aluminum is put at risk. So the fasteners are replaced with new cad plated fasteners before that can happen.

-- Edited by Marin on Monday 14th of February 2011 10:41:59 PM
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Old 02-14-2011, 09:41 PM   #4
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RE: Lead, galv steel and ss together in seawater??

Marin, I can see that happening on a mooring chain permanently in the water but do you think it is an issue when anchoring?* I understand the theory, but having used stainless steel siezing wire on shackles for 20 years without sign of degradation I wonder if this is a real concern.
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Old 02-14-2011, 09:48 PM   #5
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Lead, galv steel and ss together in seawater??

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Delfin wrote:

Marin, I can see that happening on a mooring chain permanently in the water but do you think it is an issue when anchoring?* I understand the theory, but having used stainless steel siezing wire on shackles for 20 years without sign of degradation I wonder if this is a real concern.
The above-water concern would be much less as you say--- I went back and added that to my previous post.* But it will all depend on the environment.* If the components are getting dowsed with water regularly*and have salt buildups on them--- which is the issue with floatplanes--- the problem can be accelerated.

For some years until I learned better we had a stainless swivel on our galvanized Bruce.* The galvanizing around where the swivel contacted the anchor is gone and the steel underneath has rust on it.* Today that anchor holds a shop door open so it doesn't matter, but even if we were still using it the thickness of the steel in the anchor shank is such that it would probably take a long, long, long*time for the rust to become a strength problem, although it could have caused a visual problem.

We use stainless seizing wire on our shackles, too, and while I have not examined them minutely I have not been aware of any obvious*galvanizing and rusting problem on the galvanized shackles either.

*


-- Edited by Marin on Monday 14th of February 2011 10:52:38 PM
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Old 02-15-2011, 10:01 AM   #6
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RE: Lead, galv steel and ss together in seawater??

What I've got in mind to rig up is a weight much like a Kellett but fixed. I bought 12 lb lead weights that are used on com fish gear. Sorta half shells a bit hollow in the middle. The halves are bolted together w zinc plated steel 1/4" bolts. The bolts will go through the chain links to keep things secure. I plan to substitute SS bolts and run the anchor chain through the center (chain's a bit too big) so as to be a fixed weight about 4" up the rode from the anchor shank to insure the anchor shank stays low so the anchor can set more easily at shorter scope. I would think this would cause a maximum catenary effect to enhance anchor performance. Didn't want to explain all that but there you have it. I'm guessing the dissimilar metals shouldn't be a problem. But perhaps I should keep the zinc-steel screws.
Just another kinky idea.
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Old 02-15-2011, 10:21 AM   #7
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Lead, galv steel and ss together in seawater??

Eric, You probably have an all chain rode, but I had great success with a 15lb lead weight shackled to a snatch block*and fitted to a light nylon retriever line.

I had a CQR and 20 feet of chain attached to a nylon rode.

After I set the anchor, I opened the snatch block and let the lead weight ride down to the bottom.

In a tight anchorage I could almost have the rode straight down and the anchor out on the 20' of chain accross the bottom.

Came in handy, in some crowded spots even if I did not reduce the scope to that extreme.

I did not remember to take it off my last boat when it sold, but I think it was really an awesome setup.

You are correct that adding weight before the anchor makes a big difference in its performance.

JohnP

-- Edited by JohnP on Tuesday 15th of February 2011 11:22:18 AM
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Old 02-15-2011, 11:10 AM   #8
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RE: Lead, galv steel and ss together in seawater??

Eric,
With those weights attached to the anchor chain would it not make letting out and retrival a pita or are they easily attached and detached.
Benn
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Old 02-15-2011, 01:05 PM   #9
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RE: Lead, galv steel and ss together in seawater??

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nomadwilly wrote:

I would think this would cause a maximum catenary effect to enhance anchor performance.
Eric--- I believe for catenary to be significantly effective in an anchor rode, the whole rode needs to sag, thus lowering the angle of pull.* All-chain rode does this automatically.* But while putting a weight just a few inches away from an anchor shank should help hold the end of the anchor shank down, I don't think it will affect the catenary in the rode very much or at all.* What you're doing is adding weight to the anchor itself (albeit a few inches away from the anchor).* If you actually want to increase the catenary and lower the angle of pull on the anchor, I think the weight needs to be somewhere in the middle of the rode beween the anchor and the boat.

That's not to say your weight at the end of the anchor shank won't help--- I would think that it would.* But it won't be changing the angle the rode comes in to the anchor because your rode--- which I assume will be nylon--- won't have any weight on it along its length to cause it develop any signifcant catenary.

In my super-crude drawing the black ball is your fishing weight.

*
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Old 02-15-2011, 09:27 PM   #10
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RE: Lead, galv steel and ss together in seawater??

We established a long time ago that chain catenary does little or nothing to enhance ultimate holding power but that's not my goal. Setting is the main reason for the weight. And we've always disagreed about this Marin but I think the closer the weight is to the end of the anchor shank the more good it will do and keeping the shank down low keeps the flukes or fluke pointed down. The idea of the weight is that if it's put where it will do the most good less of it will be required. Perhaps I can substitute 12lbs of lead at the shank to replace 30' of chain. Thirty feet of even 1/4" chain is about 25lbs. The whole rode would only require 2' of chain and the anchor, lead and chain would weigh about 33lbs. I can lift that handily over the rail and stow the parts as I see fit. The lead is about 2" in dia and 8" long. Benn, it should come up over the bow roller anyway. I'd prolly just detach the anchor only and put the chain and lead in the anchor box together. This is assuming the XYZ anchor works as it will have enough holding power and it weighs 18lbs. If the XYZ fails I'll prolly go to a bow roller stowed anchor like the rest of you. I have the Supreme, will be using it and that experience will say a lot about what ultimate anchor to get for the main anchor of the future.
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Old 02-15-2011, 09:43 PM   #11
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RE: Lead, galv steel and ss together in seawater??

Quote:
nomadwilly wrote:

*And we've always disagreed about this Marin but I think the closer the weight is to the end of the anchor shank the more good it will do and keeping the shank down low keeps the flukes or fluke pointed down.
No, I don't disagree with that at all.* Which is why I think your weight right next to the end of the anchor shank will help it assume a better position to dig in and set.

What I question is the subsequent angle of pull on the anchor.* Without any weight in the rode itself, either with all-chain or a kellet partway along the length of the rode, the angle the rode takes to the anchor will be more toward the surface and will exert more of an upward pull on the shank than if weight was curving the rode down so the direction of pull was closer to being parallel with*the seabed.

We know that a strong enough wind will take the catenary out of anything, be it all-chain or nylon.* But nylon will lose its catenary way sooner than all-chain, so you will be pulling up on your anchor to some degree with*nylon*(or brait)*even in a mild blow.

And*I believe that the strongest resistance an anchor can provide is achieved with the angle of pull parallel to the seabed.* That's why those anchor tests we all argue about*are all done on beaches, wet or dry, because everybody's anchor does the best in both setting and holding when it's pulled by a chain or cable that's parallel to the sand.* If you pulled up at a 30 degree angle or whatever on the rode, I bet most of the anchors would be much more reluctant to set and prone to pulling out if they did set.

So it would be interesting to know which would be more effective in getting an anchor to set solidly--- putting more weight at the end of the shank, which is what you're proposing to do,*or getting the rode's angle of pull as low and close to the seabed as possible.

*
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Old 02-16-2011, 09:55 AM   #12
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RE: Lead, galv steel and ss together in seawater??

Marin,
I just learned a neat thing. When one responds to the first post on a page you can't see the post you're responding to. Gotta remember what was said. Right now I copied and pasted your message at the bottom here and I'll get rid of it when I'm through. I'm still an idiot on this computer but I AM learning.
You're right there would be considerable catenary benefit w the chain while setting but I feel I would be MUCH better off w the weight. The biggest benefit from all chain would be (for me) a much reduced swinging radius but only in very low winds. BUT most of the time we have practically no wind at all.
Marin said:
"getting the rode's angle of pull as low and close to the seabed as possible." I think the fixed kellett I'm talking about next to the shank would (pound for pound) would do better. Think of your all chain (say 250lbs) replaced by a kellett next to the shank would keep the shank lower than all chain.

*
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Old 02-16-2011, 10:23 AM   #13
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Lead, galv steel and ss together in seawater??

One reason for having a length of chain between a nylon rode and the anchor is to keep the rode from damage from the bottom.* But another is help keep the rode closer to parallel near the anchor.* Why not use a heavier/larger chain to increase the effect?

-- Edited by markpierce on Wednesday 16th of February 2011 11:26:40 AM
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Old 02-16-2011, 10:59 AM   #14
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RE: Lead, galv steel and ss together in seawater??

Mark,
Then I'd need to get a winch for chain AND line and I don't like the system of running line on a gypsy. Or I'd need to go all chain. Also I don't think nylon line suffers on the bottom up here. Now days people may be more concerned about the rode damaging the bottom.
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Old 02-16-2011, 02:15 PM   #15
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RE: Lead, galv steel and ss together in seawater??

Quote:
nomadwilly wrote:I think the fixed kellett I'm talking about next to the shank would (pound for pound) would do better. Think of your all chain (say 250lbs) replaced by a kellett next to the shank would keep the shank lower than all chain.
What I would be concerned about is the effect of pulling up on the anchor and extra weight at a steeper angle than if the pull itself were kept low.* An interesting factoid to find out would be which is the more efficient--- putting a lot of weight on the end of the anchor itself, enough weight to resist the greater angle of pull from the rode, or putting some weight on the rode so that the angle of pull on the set anchor is much lower.

Would you need the same amount of weight midway along the rode to lower the angle of pull as the amount of weight you have to put on the anchor to resist the higher angle of pull?

How much will lowering the angle of pull on the anchor alone improve the holding as opposed to how much weight has to be added to the shank of the anchor to get that same improvement in holding with a higher angle of pull?

It's proabably a job for a computer
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Old 02-16-2011, 04:21 PM   #16
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RE: Lead, galv steel and ss together in seawater??

Probably a job for Marin. All you would need is some string and some weights. You could prove me wrong easily***** ...if I am wrong. If you could do this w a computer you could do the whole anchor test w a computer. I seriously doubt it. Some say it's best to put the weight in the anchor. With that philosophy fully employed I'd have a 125lb anchor on an all line rode. Actually if I had an all chain rode and cashed in most of that weight I could have even a heavier anchor than that AND* have a lighter rode. Hmmmmm.
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Old 02-16-2011, 05:55 PM   #17
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Lead, galv steel and ss together in seawater??

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nomadwilly wrote:

you could do this w a computer you could do the whole anchor test w a computer.
I suspect that doing so would be pretty easy for an engineer schooled in the use of the appropriate computer application.* Ever see what they can do with Computational Fluid Dynamics?* I have, and it's pretty staggering.

In essence, CFD can be used to determine virtually everything there is to know about the flow of a fluid (air, water, mud, wet sand, etc.) around an object.* Pressures, drag, temperatures, flow patterns, you name it.* And today, it's all displayed as 3D imagery that makes what's happening immediately clear.*

Years ago when Boeing was first getting into using CFD we were hired to design the keel on one of the America Cup defenders (the one that subsequently won).* No tank testing, trial and error mockups, etc. were needed.* CFD showed exactly what the design would do, and any changes to the design were illustrated immediately.* And that was with the "rude and crude" CFD.* I did some filming with some of our current CFD engineers the other week and what the system does today is truly mind boggling.

So I suspect that predicting what an anchor would do under such-and-such conditions would be pretty easy for these people.* And there may be better applications to use*than CFD.* However--- you'd have to mathematically define every single*aspect of the anchor, the sea bed, the pull on the anchor, etc.* It's worthwhile to do this sort of thing for an airplane, but I*suspect doing this for an anchor, particularly since there are so many different scenarios that would require their own definitions and calculations, it would be cost prohibitive to say nothing of the fact the engineers would view testing anchors as a major "who cares?" excercise.* So I doubt it will ever happen, particularly since the cost of the research would have to be covered in the price of the anchors that were sold. So instead of costing a few hundred dollars an anchor could cost many thousands.

*


-- Edited by Marin on Wednesday 16th of February 2011 06:56:38 PM
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Old 02-16-2011, 09:12 PM   #18
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RE: Lead, galv steel and ss together in seawater??

Well Marin since you won't belly up to the bar and buy some string and It's still winter I may appoint myself chief rode tester. Ha Ha***** ...If I don't go on a trip looking at a boat.
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