Zincs

[DavidL]

I have a question on zincs for my '69 Bristol 29. I have very little exposed shaft between the hull and the prop so the past two years since I've owned the boat, I have placed a prop nut zinc. Both times the zinc was gone when the boat was hauled, not sure if it was completely corroded or just came lose and fell off. So this year, I would like to add a zinc collar in addition to the prop zinc. Since I can't find a narrow enough 7/8 collar, I grinded the collar down to fit with about a 1/16 of a inch on both sides between the prop and the hull. Is that okay?

[Hirilondë]

Since I can't find a narrow enough 7/8 collar, I grinded the collar down to fit with about a 1/16 of a inch on both sides between the prop and the hull. Is that okay?

We do it all the time at the boatyard. One might think there would be standard applications for standard zincs, but in reality the word standard has little application at all. The biggest consideration (I am assuming you will do it safely) in grinding /cutting is assuring that the fastening mechanism isn't compromised.

[Figment]

Yep I did that for the first few years until it occurred to me to press the shaft out of the coupling 1/4" to make some space back there.

Cutting/grinding zinc SUCKS, eh? Too hard to shave like lead, too soft to cut like real metal.

[Rachel]

For a while we were "losing" prop nut zincs like crazy - they wouldn't be worn down, just GONE. Then someone suggested coating the little thin bit that's behind the fastener head; they felt that that bit ate away first which allowed the whole thing to drop off. We started coating that part with nail polish (in retrospect, duh, epoxy would have been better) prior to installation and it seemed to help.

I say it all a bit theoretically because since that part is behind the fastener anyway, I'm not sure if it can erode. There is one little section there that - once it's gone - completely renders the fastener useless.

[David]

I also have a B29 and use a 7/8" collar. I suppose my shaft protrudes a bit more than yours since I don't have to shave it down.

David

[Triton106]

Rachel wrote:

For a while we were "losing" prop nut zincs like crazy - they wouldn't be worn down, just GONE. Then someone suggested coating the little thin bit that's behind the fastener head; they felt that that bit ate away first which allowed the whole thing to drop off. We started coating that part with nail polish (in retrospect, duh, epoxy would have been better) prior to installation and it seemed to help.

I say it all a bit theoretically because since that part is behind the fastener anyway, I'm not sure if it can erode. There is one little section there that - once it's gone - completely renders the fastener useless.

I don't know why this keeps happening to me but I search all over internet to find a particular subject matter (eg. how good is Interlux Brightside for painting hull using roll and tip method) but could not find it but the minute after I complete the project (eg. bought 6 quarts of Brightside and primer) the subject comes to me without my asking.

What am I am talking about? Well I have been scratching my head with my prop nut zinc the last two haul outs (both cases gone). I just figure it was completely sacraficed. Now it all start to make sense to me. I also contemplated with adding a 7/8" collar zinc but there just was not enough space there. I never even thought of shaving it down. Well now Triton106 is back in the water it is too late until my next haul out two years from now. Thanks... sigh.

[Figment]

How cold is the water in Berkeley?

[Triton106]

Figment, I think I know where you are going with the question. I don't know but the divers here always wear wetsuit which I don't have. I suppose I can alway go buy one. Then there are those stingrays that like to cruise around the marina. Hmmm...

[bcooke]

You can rent wetsuits from any scuba shop relatively inexpensively.

Stingrays are harmless.

[LazyGuy]

Stingrays are harmless.

Tell that to the Croc Hunter. 8>)

[bcooke]

Okay, harmless to non-knuckleheads.

[Brett]

Okay, harmless to non-knuckleheads.

I can confirm that stingrays are not harmless here in Australia, knucklehead or not!! Along with the box jelly-fish, great white sharks, salt water crocs and blue-ringed octopus......

[bcooke]

Along with the box jelly-fish, great white sharks, salt water crocs and blue-ringed octopus......

Maybe, but this tangent is getting a little carried away from the topic of zincs and I really don't think the rays in San Francisco Bay compare with what I agree are certainly more dangerous Australian sea species. For the record I have dived with thousands of Australian rays when I lived there with no hint of danger or aggresion on the ray's part. Don't mess with them, they don't mess with you. What happened to the Croc Hunter was a truly freak accident which could probably have been avoided if he had left the damn thing alone in the first place. Makes for boring TV though. In my experience, real croc hunters despise the late TV personality and often redicule him.

Point being, if you can combat the cold using an inexpensive rented wetsuit, you can work on the zincs in the water.

[Brett]

Along with the box jelly-fish, great white sharks, salt water crocs and blue-ringed octopus......

Maybe, but this tangent is getting a little carried away from the topic of zincs and I really don't think the rays in San Francisco Bay compare with what I agree are certainly more dangerous Australian sea species. For the record I have dived with thousands of Australian rays when I lived there with no hint of danger or aggresion on the ray's part. Don't mess with them, they don't mess with you. What happened to the Croc Hunter was a truly freak accident which could probably have been avoided if he had left the damn thing alone in the first place.

Point taken. Back to the zincs falling off.... I've seen zinc collars fitted with two hose clips (worm gears on each side for balance I guess) in addition to the metal threads supplied with the collar. Sometimes the collars on my boat disappear within a few months, other times they are almost untouched after a year.