I know it's been discussed in the past but now it's my turn...
I was in the water today cleaning slime and baby barnacles from Feather's bottom and prop. I was examining the prop and shaft, trying to figure out what I was seeing in the cloudy water. There is a colar with two allen screws furthest forward of the prop. Is that my zinc? If so, it appears in good shape since it's been painted over--which I assume it should not be. Behind the prop are two nuts (which makes it a boy I guess), and then a cotter pin. No zinc is on the end. Am I identifying things correctly? thanks
[img]http://www.geocities.com/travel-rn/propshaft.jpg[/img]
CD 30 Prop shaft zinc
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Scott MacCready
- Posts: 208
- Joined: Feb 5th, '05, 21:53
- Location: Previous Owner of CD30-ketch, CD26 #29, and CD25 #635 Hulls Cove,ME
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CD 30 Prop shaft zinc
Last edited by Scott MacCready on Jul 5th, '06, 16:22, edited 1 time in total.
Scott,
I use the same type of "donut" zinc on my shaft and replace it every year, they are not expensive. No , I wouldn't paint it. 2 nuts on the end ? could you perhaps have one of those zinc perry nuts ? (I think thats the name).If so search the archives for info as to where to obtain them. I don't have one on mine.
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I use the same type of "donut" zinc on my shaft and replace it every year, they are not expensive. No , I wouldn't paint it. 2 nuts on the end ? could you perhaps have one of those zinc perry nuts ? (I think thats the name).If so search the archives for info as to where to obtain them. I don't have one on mine.
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Rhode Island Marijuana Dispensaries
Last edited by Ron M. on Feb 11th, '11, 05:24, edited 1 time in total.
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Scott MacCready
- Posts: 208
- Joined: Feb 5th, '05, 21:53
- Location: Previous Owner of CD30-ketch, CD26 #29, and CD25 #635 Hulls Cove,ME
- Contact:
Thanks Ron,
Like I said, the water was pretty cloudy since I had been bottom cleaning, but it appeared as though there was a smaller locknut behind the first nut. Didn't appear to be anything too special. The donut was pretty well matched up to the hull. Until I noticed the allen head screws, I thought it was just the fairing of the hull where the shaft comes out.
Like I said, the water was pretty cloudy since I had been bottom cleaning, but it appeared as though there was a smaller locknut behind the first nut. Didn't appear to be anything too special. The donut was pretty well matched up to the hull. Until I noticed the allen head screws, I thought it was just the fairing of the hull where the shaft comes out.
Last edited by Ron M. on Feb 11th, '11, 05:24, edited 1 time in total.
I have the same setup...donut zinc forward of the prop...2 nuts with cotter pin aft of the prop.
The zinc should not be painted (they don't work very well that way, but they will last longer since they aren't working)...it should also not be up against the stern-tube/cutlass-bearing or it will restrict water flow into the bearing. If it were mine, I would replace it because it is painted.
The 2 nuts are used to lock against each other...the first one is tightened to secure the prop then held in place while the second one is tightened against it. The cotter pin is the safety net in case the nuts loose their torque. The second nut usually has grooves cut across it so that when the cotter pin is inserted thru the hole in the shaft it also passed thru the grooves to keep the nut from backing off. OK, that explanation is probably about as clear as the water you were diving in....
The zinc should not be painted (they don't work very well that way, but they will last longer since they aren't working)...it should also not be up against the stern-tube/cutlass-bearing or it will restrict water flow into the bearing. If it were mine, I would replace it because it is painted.
The 2 nuts are used to lock against each other...the first one is tightened to secure the prop then held in place while the second one is tightened against it. The cotter pin is the safety net in case the nuts loose their torque. The second nut usually has grooves cut across it so that when the cotter pin is inserted thru the hole in the shaft it also passed thru the grooves to keep the nut from backing off. OK, that explanation is probably about as clear as the water you were diving in....
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Oswego John
- Posts: 3535
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- Location: '66 Typhoon "Grace", Hull # 42, Schooner "Ontario", CD 85D Hull #1
Prop Shaft Nuts
Hi Glen,
You did quite well with your explanation. When two nuts are used, usually a thick nut holds the work in place and a second, thinner *JAM* nut locks the wide nut from loosening.
A nut with grooves cut around the outer perimeter is called a *Castellated* nut. This type nut is used rather than a regular nut with a hole drilled in it for a cotter key. When a regular type hex nut is socked up, you never know where the hole in the nut will line up in relation to the corresponding hole in the shaft. In order to line the holes up, you might have to back the nut off to insert the cotter key.
Using a castellated type nut and flat washers or the same metal, it is relatively easy to line the hole in the shaft with any of the castellation grooves.
Just a wild thought, do you think that paint remover would work on the zinc?
Best regards,
O J
You did quite well with your explanation. When two nuts are used, usually a thick nut holds the work in place and a second, thinner *JAM* nut locks the wide nut from loosening.
A nut with grooves cut around the outer perimeter is called a *Castellated* nut. This type nut is used rather than a regular nut with a hole drilled in it for a cotter key. When a regular type hex nut is socked up, you never know where the hole in the nut will line up in relation to the corresponding hole in the shaft. In order to line the holes up, you might have to back the nut off to insert the cotter key.
Using a castellated type nut and flat washers or the same metal, it is relatively easy to line the hole in the shaft with any of the castellation grooves.
Just a wild thought, do you think that paint remover would work on the zinc?
Best regards,
O J
OJ,
paint remover should definitely remove the paint and make all well...but I would think that applying it underwater would be the trick. Wire brushing it would also work and, hopefully, the uninformed person who painted it didn't put one coat of paint on the shaft before remembering to install the zinc and then painting it to make it match (which of course would render the zinc completely useless).
So, then, how do you keep the barnacles off of your zinc?
I quit painting my shaft and prop years ago...never seemed to work very well...I just scrape it regularly.
paint remover should definitely remove the paint and make all well...but I would think that applying it underwater would be the trick. Wire brushing it would also work and, hopefully, the uninformed person who painted it didn't put one coat of paint on the shaft before remembering to install the zinc and then painting it to make it match (which of course would render the zinc completely useless).
So, then, how do you keep the barnacles off of your zinc?
I quit painting my shaft and prop years ago...never seemed to work very well...I just scrape it regularly.
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Oswego John
- Posts: 3535
- Joined: Feb 5th, '05, 20:42
- Location: '66 Typhoon "Grace", Hull # 42, Schooner "Ontario", CD 85D Hull #1
Hi Glen,
We're talking about a zinc collar on a painted prop shaft.
#1 Does the sacrificial zinc actually have to make contact with the metal it is protecting?
#2 By just being in the area of the metal without actually making contact, does the zinc afford adequate protection?
#3 If there should be a coating of anti-fouling paint on the shaft, would the particles of copper in the paint constitute conductivity between the zinc and the shaft?
I havent a clue what the answers are, just supposition. Maybe some readers can shed some light on this.
FWIW, I have read of some boatowners in hot marinas that dangle zinc guppies (or minnows) in the water adjacent to their hulls. Other than that statement, I don't know if the zinc fish hangs on a cord or on a grounded metal wire. I feel that there is no physical contact between the fish and the metal being protected. It is just suspended in the water nearby other metal to be protected. What is the theory behind this practice?
All ideas and thoughts are welcomed.
O J
Your last statement brings up an interesting point that I don't have an answer for.Glen C wrote:OJ,
..."but I would think that applying it underwater would be the trick. "
Yes, applying paint remover underwater would be quite a trick.
"and, hopefully, the uninformed person who painted it didn't put one coat of paint on the shaft before remembering to install the zinc and then painting it to make it match (which of course would render the zinc completely useless).y.
We're talking about a zinc collar on a painted prop shaft.
#1 Does the sacrificial zinc actually have to make contact with the metal it is protecting?
#2 By just being in the area of the metal without actually making contact, does the zinc afford adequate protection?
#3 If there should be a coating of anti-fouling paint on the shaft, would the particles of copper in the paint constitute conductivity between the zinc and the shaft?
I havent a clue what the answers are, just supposition. Maybe some readers can shed some light on this.
FWIW, I have read of some boatowners in hot marinas that dangle zinc guppies (or minnows) in the water adjacent to their hulls. Other than that statement, I don't know if the zinc fish hangs on a cord or on a grounded metal wire. I feel that there is no physical contact between the fish and the metal being protected. It is just suspended in the water nearby other metal to be protected. What is the theory behind this practice?
All ideas and thoughts are welcomed.
O J
OJ,
from my understanding of what I've read and been told...
#1 the zinc must have good contact with the metals that it is protecting
#2 just being close provides no protection for any metals located nearby...if this were not true, then why would we ever go to the trouble of attaching a zinc to the shaft?
#3 the particles are surrounded by paint...they do not provide adequate connection between the zinc to the shaft...much like corrosion on a battery terminal
The zinc guppies have a stainless wire (like standing rigging) embedded with a stainless clamp on the other end that is to be attached to a shroud (in systems that are bonded) or to the prop shaft (inside the engine compartment). When attached and the guppy is dropped overboard, they provide more protection against galvanic corrosion to whatever system of metals that they are attached to.
We are looking at 2 destructive process here: electrolysis and galvanic corrosion. Galvanic corrosion is a relatively slow process that occurs between 2 dissimilar bonded metals (bronze prop and stainless shaft) when submerged in saltwater and is retarded with the use of zincs. Electrolysis occurs when electricity is introduced into the surrounding water and can be a very fast process that can cause thru hulls to dissolve in a matter of hours and sink a boat. The best protection against electrolysis is to not connect to shore power (which would provide a ground for the stray electrical current in the water)...or at least have a galvanic isolator installed on the boat in the shore power circuit. A zinc guppy might help in mild cases of electrolysis, but one would have to be connected to each system of metals exposed to saltwater submersion...not all boats have the lightening ground system (chainplates, thru hulls, stanchions) connected to the DC ground system (batteries, engine, shaft).
Generally it is not the marina that is "hot", it's a nearby boat with faulty wiring that is leaking DC current into the water. It is this electrical current that finds its way to ground on a nearby boat via a thru hull or shaft to the DC ground then the AC ground (which should be connected to the DC ground, but is not on all boats) out the shore power cord to the AC ground plate (usually located in earth outside the marina). This path can cause extremely rapid destruction of the underwater metals...bronze thru hulls can go rather quickly and it makes a good argument for marlon thru hulls.
Anyways, this is kind sort how I've come to understand it, but when it comes to the knowledge of molecular structures and electricity I claim no fame. In fact, if anyone can provide any enlightening insights.....
from my understanding of what I've read and been told...
#1 the zinc must have good contact with the metals that it is protecting
#2 just being close provides no protection for any metals located nearby...if this were not true, then why would we ever go to the trouble of attaching a zinc to the shaft?
#3 the particles are surrounded by paint...they do not provide adequate connection between the zinc to the shaft...much like corrosion on a battery terminal
The zinc guppies have a stainless wire (like standing rigging) embedded with a stainless clamp on the other end that is to be attached to a shroud (in systems that are bonded) or to the prop shaft (inside the engine compartment). When attached and the guppy is dropped overboard, they provide more protection against galvanic corrosion to whatever system of metals that they are attached to.
We are looking at 2 destructive process here: electrolysis and galvanic corrosion. Galvanic corrosion is a relatively slow process that occurs between 2 dissimilar bonded metals (bronze prop and stainless shaft) when submerged in saltwater and is retarded with the use of zincs. Electrolysis occurs when electricity is introduced into the surrounding water and can be a very fast process that can cause thru hulls to dissolve in a matter of hours and sink a boat. The best protection against electrolysis is to not connect to shore power (which would provide a ground for the stray electrical current in the water)...or at least have a galvanic isolator installed on the boat in the shore power circuit. A zinc guppy might help in mild cases of electrolysis, but one would have to be connected to each system of metals exposed to saltwater submersion...not all boats have the lightening ground system (chainplates, thru hulls, stanchions) connected to the DC ground system (batteries, engine, shaft).
Generally it is not the marina that is "hot", it's a nearby boat with faulty wiring that is leaking DC current into the water. It is this electrical current that finds its way to ground on a nearby boat via a thru hull or shaft to the DC ground then the AC ground (which should be connected to the DC ground, but is not on all boats) out the shore power cord to the AC ground plate (usually located in earth outside the marina). This path can cause extremely rapid destruction of the underwater metals...bronze thru hulls can go rather quickly and it makes a good argument for marlon thru hulls.
Anyways, this is kind sort how I've come to understand it, but when it comes to the knowledge of molecular structures and electricity I claim no fame. In fact, if anyone can provide any enlightening insights.....