I was looking at the prop shaft on Hanalei (CD-30)last weekend. The prop nut seems to have a cage attached to it with a threaded hole in the end that I think is used to attach a zinc. First question is: Is this a good place to attach the zinc, or would I be better off using a standard 1" donut zinc between the prop and the cutless bearing (less of a vibration moment arm)? Second question: If I use the original end of shaft zinc, where can I buy one, is it a special CD zinc?
When Hanalei was launched lst spring, it did have an end of shaft zinc. It seemed to work OK, but it is completely gone now. I don't know if it fell off or just erroded away. There was no bolt left in the end of the cage!
Any thoughts would be appreciated.......
Dave Stump
Captain Commanding
s/v Hanalei (CD-30)
stumpdg@gwsmtp.nu.com
Shaft zincs
Moderator: Jim Walsh
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TOM
Re: Shaft zincs
If the 1/4 x 20 round head bolt is missing I would say it came unscrewed. If just the zinc eats away usually you are left with the bolt. I posted about this a little while back and caused a lot of confusion so let me carefully go over it again. The zinc you will need to go on the prop nut is a size "c" (for 7/8 or 1 inch shafts). The zinc comes with a star type lock washer, but if you've lost the bolt you'll have to buy that separately. It's about an inch long but to check you can look at one of the complete units on the shelf at your local chandlery. You can buy the entire unit with the zinc or you can buy the zinc separately for yearly replacement. When you put the zinc on put a dab of 5200 or Sikaflex on the threads of the quarter twenty bolt that holds it on. This will keep it from unscrewing itself and doing this again, but it's easy for you to screw it out next year. Underwater the 5200 gets sort of gummy like old window glazing putty which is gooey enough to hold the screw from getting loose but soft enough to unscrew the bolt through it.D. Stump, Hanalei wrote: I was looking at the prop shaft on Hanalei (CD-30)last weekend. The prop nut seems to have a cage attached to it with a threaded hole in the end that I think is used to attach a zinc. First question is: Is this a good place to attach the zinc, or would I be better off using a standard 1" donut zinc between the prop and the cutless bearing (less of a vibration moment arm)? Second question: If I use the original end of shaft zinc, where can I buy one, is it a special CD zinc?
When Hanalei was launched lst spring, it did have an end of shaft zinc. It seemed to work OK, but it is completely gone now. I don't know if it fell off or just erroded away. There was no bolt left in the end of the cage!
Any thoughts would be appreciated.......
Dave Stump
Captain Commanding
s/v Hanalei (CD-30)
As to whether to use a collar zinc or a prop nut zinc (called a Perry nut BTW, I use both on mine because I'm in a pretty "hot" marina. I'd start with the Perry nut because you're trying to protect the edge of the prop blade from electrolysis and that is as close as you can get. Once you have the zinc fixed so it can't unscrewed check it the next year. If most of your zinc is left that's all you'll need. If the zinc is mostly eaten away then you might want to add a collar zinc as well. It looks out of balance sticking way out there behind the prop, but the vibration is negligible and is the standard way to do it.
You'll find both the complete unit and the replacement zincs on page 421 (upper right picture) of the West Catalog. The zinc is $ 8.79. I believe West stills stocks the ones made by Electro Guard. I don't believe that Cape Dory has/had their own version. It's possible (but probably unlikely) that you might have the original Perry Nut made by the Perry Boatyard in Calif. If so, their address and phone is in a prior posting on this board several months ago.
A final after thought. Star type lock washers depend upon tension between the head of the bolt and the object they are holding on. When the zinc eats away as they are designed to do, the tension is lost and a lock washer is useless. If you have a bad electrolysis problem you could conceivably lose both the zinc and the bolt. You can also be over zinced so you don't want to add it unless necessary. It's not as complicated as this makes it sound, but I'm trying to cover everything for you here.
TacCambria@thegrid.net
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Mike Thorpe
Re: Shaft zincs
Dave,
There was a long discussion about this very subject in the spring. Use the message board search engine and search under the the word beckman (an east coast supplier) and then follow the thread back. You will get all the words of wisdom and both an East & West coast supplier for the original CD "Perrynut" zincs.
Also, I seem to recall some discussion (this board??) about a doughnut type zinc between the prop and the deadwood impeading the water flow to the cutless bearing. How good this information is in anyones guess.
I do know that there was a Perynut zinc on my CD27 when I bought it and that I replaced it last spring with the West Marine zinc that Tom mentions (couldn't find a Perrynut supplier at the time). I had to grind it down quite a bit to clear the rudder and it worked OK. However, I still don't like the cap screw in the end to hold it on. I much prefer the simple cotter pin in the perrynut design and will use a perrynut next spring.
Good luck
Mike Thorpe
CD27 Lady Jane
mthorpe@capecod.net
There was a long discussion about this very subject in the spring. Use the message board search engine and search under the the word beckman (an east coast supplier) and then follow the thread back. You will get all the words of wisdom and both an East & West coast supplier for the original CD "Perrynut" zincs.
Also, I seem to recall some discussion (this board??) about a doughnut type zinc between the prop and the deadwood impeading the water flow to the cutless bearing. How good this information is in anyones guess.
I do know that there was a Perynut zinc on my CD27 when I bought it and that I replaced it last spring with the West Marine zinc that Tom mentions (couldn't find a Perrynut supplier at the time). I had to grind it down quite a bit to clear the rudder and it worked OK. However, I still don't like the cap screw in the end to hold it on. I much prefer the simple cotter pin in the perrynut design and will use a perrynut next spring.
Good luck
Mike Thorpe
CD27 Lady Jane
mthorpe@capecod.net
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TOM (again)
Re: Shaft zincs
If the authentic Perry nut uses a cotter pin and the electro guard uses a bolt to hold the zinc on, that's probably a way to tell which one you have.Mike Thorpe wrote: Dave,
There was a long discussion about this very subject in the spring. Use the message board search engine and search under the the word beckman (an east coast supplier) and then follow the thread back. You will get all the words of wisdom and both an East & West coast supplier for the original CD "Perrynut" zincs.
Also, I seem to recall some discussion (this board??) about a doughnut type zinc between the prop and the deadwood impeading the water flow to the cutless bearing. How good this information is in anyones guess.
I do know that there was a Perynut zinc on my CD27 when I bought it and that I replaced it last spring with the West Marine zinc that Tom mentions (couldn't find a Perrynut supplier at the time). I had to grind it down quite a bit to clear the rudder and it worked OK. However, I still don't like the cap screw in the end to hold it on. I much prefer the simple cotter pin in the perrynut design and will use a perrynut next spring.
Good luck
Mike Thorpe
CD27 Lady Jane
TacCambria@thegrid.net
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Steve Alarcon
Re: Shaft zincs
Dave,
What you have left is the remnant of your prop-nut zinc. It was erroded away as the result of electricity moving between the salt water and your electrical system. If you don't replace it right away, the electricity will continue to eat away other "less noble" (i.e., less likely to errode) metals, like your prop and your through-hulls. Don't delay, as this errosion can eat away metal at amazing rates.
I'm not sure about your CD30, but mine doesn't have room on the shaft for a zinc. So, in addition to the prop nut zinc, I use a "grouper" (a big zinc, attached to a wire that you can clip to your grounding system and let over the side to provide additional protection). They are available from most marine stores (I think about $50) or you can make one with a shaft zinc clamped to a wire that you have installed your own clip on for about $15.
Good luck, and don't delay with replacing that zinc!
Steve Alarcon
CD30 Temerity
Seattle
stee.alarcon@attws.com
What you have left is the remnant of your prop-nut zinc. It was erroded away as the result of electricity moving between the salt water and your electrical system. If you don't replace it right away, the electricity will continue to eat away other "less noble" (i.e., less likely to errode) metals, like your prop and your through-hulls. Don't delay, as this errosion can eat away metal at amazing rates.
I'm not sure about your CD30, but mine doesn't have room on the shaft for a zinc. So, in addition to the prop nut zinc, I use a "grouper" (a big zinc, attached to a wire that you can clip to your grounding system and let over the side to provide additional protection). They are available from most marine stores (I think about $50) or you can make one with a shaft zinc clamped to a wire that you have installed your own clip on for about $15.
Good luck, and don't delay with replacing that zinc!
Steve Alarcon
CD30 Temerity
Seattle
stee.alarcon@attws.com