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Old 21-07-2010, 11:25   #481
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Originally Posted by ConradG View Post
I can't see any reason to keep your rudder electrically isolated except for the electric potential difference that might cause galvanic corrosion between dissimilar metals. The plastic or nylon bushings, in addition to being non galvanic, are usually to provide less friction than using the same material that the post is made from and also to provide a noncorrosive material that will wear instead of the post itself...The zincs added to metal on rudders are there because they are isolated electrically from the zincs on the hull and therefore not protected by them.
I think you're spot on here.

If your rudder gudgon is standard size you can get UHMW Polyethylene or Polypropylene in round stock and drill a hole in it for the pintle or cut out a few circles out of sheets of it with a hole saw and use that, I use a plastic hose barb for my rudder, fits like a glove and the price is right. Some people pay others to machine them little plastic tubes but generally if you've got a pair of calibers and access to a hardware store you can find some nice bushings in the plumbing department, of course this is made easier if all your gear is built out of standard sch 40 or 20 pipe.
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Old 21-07-2010, 11:58   #482
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Good information here, thanks again. I think I will leave the zink on the rudder and replace the bushings.
Thanks All
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Old 21-07-2010, 11:59   #483
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Nylon wears well for low tech solutions. Many plumbing fittings can be had in nylon. These bushings aren't ussually very complicated..a drill press and a file can do a pretty good job of truning down and/or boring out...
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Old 21-07-2010, 12:19   #484
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The keel weighs 200 pounds, the pin is 1 inch in diameter and it sticks out an inch. I was a little worried about the bushing in heavy weather. But I guess since it has worked for the last 20 years, it should be ok. Right?
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Old 21-07-2010, 12:51   #485
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Originally Posted by SaltyMonkey View Post
Chalk another one up for steel boats.

News - General: Whale lands on yacht*(Page 1 of 2)

Originally brought to us through thread:

http://www.cruisersforum.com/forums/...cht-43971.html
I thought this was a hoax. But look on MSN.com. The after pictures show the wrecked boat.
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Old 21-07-2010, 14:06   #486
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Conrad, are you sure about that? I would never claim to be an expert on this subject, but your answer doesn't "feel" right. After all, there are normally multiple zincs on a steel hull, yet the entire hull is one unit, so it has to do with more than multiple zincs, multiple units idea. I still don't see why you'd want to isolate the rudder, that seems to me to be adding unnecessary complications to what end? Isolated or not, you still have zincs on your rudder, right?

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Thomas
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Old 21-07-2010, 20:48   #487
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Conrad, are you sure about that? I would never claim to be an expert on this subject, but your answer doesn't "feel" right. After all, there are normally multiple zincs on a steel hull, yet the entire hull is one unit, so it has to do with more than multiple zincs, multiple units idea. I still don't see why you'd want to isolate the rudder, that seems to me to be adding unnecessary complications to what end? Isolated or not, you still have zincs on your rudder, right?

Regards,

Thomas
Oh that's not that strange, unless it looks like the builder went to great length to isolate the rudder? Mine might be fully isolated by the hose barbs in the pintle it would depend on whether the bottom pintle rides on the bottom of the gudgon or resting on the top of the hose barb, can't remember now. But either way I have two zincs on my rudder one on either side, it's a bit of a barn door type of thing, and I have one on the shaft as well.
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Old 21-07-2010, 22:57   #488
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it does swell in water so make sure you have sufficient clearance around the pins, otherwise it may grab.
Regards, Richard.
Delrin is not supposed to swell, I use a mix of Delrin and Duramax bearings.
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Old 22-07-2010, 08:19   #489
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nylon, delrin, other stuff

Those in-water bearings nylon OK only if pre-bore to a bigger dia, and only if the bigger dia does not make extra problems. Delrin has its pitfalls too.

Have a look at what goes into well build boats in the same area and follow suit. Do not re-invent the wheel ;-))

b.
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Old 23-07-2010, 06:49   #490
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Conrad, are you sure about that? I would never claim to be an expert on this subject, but your answer doesn't "feel" right. After all, there are normally multiple zincs on a steel hull, yet the entire hull is one unit, so it has to do with more than multiple zincs, multiple units idea. I still don't see why you'd want to isolate the rudder, that seems to me to be adding unnecessary complications to what end? Isolated or not, you still have zincs on your rudder, right?

Regards,

Thomas
Not quite sure what you are saying..
The "plastic" bushings are to reduce friction ussually and to keep any corrossion from occuring between any dissimilar metals ( galvanic corrossion from electronic potential differences) as well as to prevent the rudder post or socket metals from wearing. Alot easier to replace a bushing than rudder post metal.

Frequency of zincs depends on many factors but if your rudder is isolated by plastic bushings it has no protection unless it has it's own. There are some who believe that so long as there are no dissimilar metals in contact with your hull, zincs aren't needed. I've been in touch with one naval architect quite a bit recently (with my Colvin Gazelle project) who "didn't use" zincs on his metal boats, steel or aluminum, engine or no, electrical system or not, but instead kept the hull isolated from dissimilar metals and the electrical system.
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Old 23-07-2010, 11:37   #491
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Not quite sure what you are saying..
The "plastic" bushings are to reduce friction ussually and to keep any corrossion from occuring between any dissimilar metals ( galvanic corrossion from electronic potential differences) as well as to prevent the rudder post or socket metals from wearing. Alot easier to replace a bushing than rudder post metal.

Frequency of zincs depends on many factors but if your rudder is isolated by plastic bushings it has no protection unless it has it's own. There are some who believe that so long as there are no dissimilar metals in contact with your hull, zincs aren't needed. I've been in touch with one naval architect quite a bit recently (with my Colvin Gazelle project) who "didn't use" zincs on his metal boats, steel or aluminum, engine or no, electrical system or not, but instead kept the hull isolated from dissimilar metals and the electrical system.
I don't know if I'd go that far, I've been counseled against over zincing but no zincs at all is just looking for disaster, what about the boat anchored next to you's electrical system? I keep my engine ground disconnected unless I'm running the engine and the rest of the electrical system is isolated from the hull, there are some places under water that are welded stainless (rudder pintle and gudgon for one) no aluminium under water but there's always something going on down there I'm sure, transferring electrons back and forth, the zincs i have are those nice big ones, 18"x4" bolt on zincs and I have 6 on the boat none of which are wearing down at any alarming rate but are worn just enough to let me know that they're working.
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Old 23-07-2010, 11:58   #492
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It is my understanding that zincs will help in galvanic situations where your hull's electrons would otherwise be given up due to the material being less noble. Where there is electrical potential difference in two physically connected pieces of metal in an electrolite. Where your hull material is acting as a metal in a battery situation and giving up it's electrons instead of the more noble metal's. The zinc is less noble and gives it's upinstead. If there is no more noble metat connected to your hull you don't have to worry about galvanic loss of electrons. If your hull isn't in contact with a more noble metal there isn't a need for a sacrificial metal or zinc.

With steel zinc coating or galvanising is a form of barier coating like paint to keep it from oxidizing. But steel won't not rust if a zinc is attatched.

Electroplating, the loss or gain of electrons with the addition of electricity as happens with stray current is entirely different again and zincs won't help (unless the current decides to leave your hull at that point. Two coating breaches and electrical current will chose to travel through your hull istead of through the water because it is more conductive...period. Unpainted (as they should be) zincs theoretically provide a way for that current to get in (or out) and therefore any scratch in your coating underwater provides the potential for rapid electron loss with the addition of electrical current. (Stay away from marinas!)
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Old 23-07-2010, 12:23   #493
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God I love this thread. I'm learning a ton of new stuff.
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Old 23-07-2010, 13:43   #494
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... But steel won't not rust if a zinc is attatched ...
Or maybe not.
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Old 27-07-2010, 11:48   #495
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I talked with ( I think his name is Adam) at West system epoxy. He reccomended when working with old steel, to apply the epoxy with a brush, then go over it with a hand held wire brush and work it in really well. Then, go over it with another coat using just a paint brush. Has anybody done this? how did you like the results?
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