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Old 05-11-2011, 07:01   #16
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Re: Suggtestions for removing Barnacles from a Bronze Propeller

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Originally Posted by minaret View Post
...Wonder why they are so worried about scratching, ....
Hydrodynamics. A propellor blade is a foil operating in a fluid. Unless you are acquainted with Reynolds Numbers, Bernoullie's Equation, Laminaer verses Turbulent Flow and the effect the Roughness Coefficient of a foil has on the point of flow separation across the foil, and the consequences, a detailed discussion would be quite pointless. Leave it be said that one wants/needs a blade to be as smooth and fine as possible if the blade is to function property and to it's maximum capability and without cavitation that errodes the blade surfaces/edges.

Minimizing the Roughness Coefficient is the objective of eliminating the lime circles left by Barnacles. An effective material for these is a product known as RydLyme. A thin towel saturated with a RydLyme solution and wrapped around the prop blades will dissolve the deposits. A compound known as CLR (see Home Depot) might also serve the same function. A follow up with fresh water rinse and then a polish will produce a remarkable difference in the performance of the Prop. FWIW we have been using a product known as "PropSpeed" that seems to prevent growth on the prop.

FWIW...
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Old 05-11-2011, 07:21   #17
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pirate Re: Suggestions for Removing Barnacles from a Bronze Propeller

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Originally Posted by GordMay View Post
NEVER mix bleach and vinegar!
In fact, you really shouldn’t mix bleach with anything (except water).
Mixing bleach and vinegar, or any acid, releases toxic chlorine gas.
True... but a 50/50 mix is a great deck cleaner... there it was green... GONE...
And the fumes really clear the crap outa your chest...
don't even have to breathe...
like amonia it just seeps in...
glue sniffers would love it...

(My contribution to population control...)
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Old 05-11-2011, 07:35   #18
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Re: Suggtestions for removing Barnacles from a Bronze Propeller

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Originally Posted by svHyLyte View Post
Hydrodynamics. A propeller blade is a foil operating in a fluid. Unless you are acquainted with Reynolds Numbers, Bernoullie's Equation, Laminaer verses Turbulent Flow and the effect the Roughness Coefficient of a foil has on the point of flow separation across the foil, and the consequences, a detailed discussion would be quite pointless. Leave it be said that one wants/needs a blade to be as smooth and fine as possible if the blade is to function property and to it's maximum capability and without cavitation that errodes the blade surfaces/edges.

Minimizing the Roughness Coefficient is the objective of eliminating the lime circles left by Barnacles. An effective material for these is a product known as RydLyme. A thin towel saturated with a RydLyme solution and wrapped around the prop blades will dissolve the deposits. A compound known as CLR (see Home Depot) might also serve the same function. A follow up with fresh water rinse and then a polish will produce a remarkable difference in the performance of the Prop. FWIW we have been using a product known as "PropSpeed" that seems to prevent growth on the prop.

FWIW...
All relevant issues but in the practical world of a sail boat prop the theoretical implications of laminar flow, separation, cavitation, etc are not that critical (in my opinion) for several reasons.

1. Prop speed on a displacement hull are much slower than high speed boats, airplane props etc so less sensitive to these effects.

2. After a fairly short period of use a boat prop is going to have lots of little nicks and dings on the leading edge of the prop anyway, negating the benefits of keeping a perfectly polished blade surface.

3. Have not examined the finish produced by PropSpeed but other prop treatments I have seen in the past were not mirror smooth and I felt I could achieve as good or better finish on the blade surface by polishing with very fine sand paper.

I would wager a cheap beer or a gift certificate for a Happy Meal, that there would be no measurable difference in performance on a sailboat with a brand new, perfectly polished prop vs an older, slightly scratched but cleaned prop. More important would insuring that the prop blades are not bent or warped in any way and repairing dings in the leading edge of the blades.
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Old 05-11-2011, 08:05   #19
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

Do it as the first job after haul out - that way they are still squidgy

Apart from that, a scraper and some elbow grease.
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Old 05-11-2011, 08:05   #20
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

Have scraped barnacles off my flex o fold with metal scraper for
last 4 years...try to keep scraper flat (and do most of the time
to avoid gouging) have to use fine sand paper for stubborn
barnacle rings...then polish. Prop seems to hold up just fine...
but water flow surely not smooth as could be.
Will look into using some Rydlyme this year.
Any success with the paint products other than prop seal which
I know is very good and very expensive?
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Old 05-11-2011, 08:51   #21
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Re: Suggestions for removing Barnacles from a Bronze Propeller

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All relevant issues but in the practical world of a sail boat prop the theoretical implications of laminar flow, separation, cavitation, etc are not that critical (in my opinion) for several reasons.

1. Prop speed on a displacement hull are much slower than high speed boats, airplane props etc so less sensitive to these effects.

2. After a fairly short period of use a boat prop is going to have lots of little nicks and dings on the leading edge of the prop anyway, negating the benefits of keeping a perfectly polished blade surface.

3. Have not examined the finish produced by PropSpeed but other prop treatments I have seen in the past were not mirror smooth and I felt I could achieve as good or better finish on the blade surface by polishing with very fine sand paper.

I would wager a cheap beer or a gift certificate for a Happy Meal, that there would be no measurable difference in performance on a sailboat with a brand new, perfectly polished prop vs an older, slightly scratched but cleaned prop. More important would insuring that the prop blades are not bent or warped in any way and repairing dings in the leading edge of the blades.
Perhaps the foregoing is entirely true on your yacht but I can assure you that on ours, a newly cleaned prop has an easily discernible difference with our 2-blade 20" Gori folder. It is also measurable--and material--in terms of our fuel burn rate which drops to a tad over .5 gal/hour from .9 gal/hr to average 6 knots through the water under power. The difference may not be meaningful on your yacht but whereas we only carry 47 usable gallons, it is to us.

As for ProSpeed, it certainly does not leave a mirror surface but, at least where we are moored, it does an excellent job of keeping growth off the Prop tho' at some cost. For me, the cost is worth it as when I need power out of that Prop, I need it, as we maneuver in very tight circumstances in our mooring.

For a thorough discussion of the matter, I refer you to CA ("Tony") Marchaj's text, "Sailing Theory and Practice", (c) 1964, pages 239-242.

Hugosalt--There are times when one must scrape. If so, however, it is wise to scrape across the blade, in the direction of flow, rather than length-wise. Believe it or not, one can also "sand" under water by using a pad of cheese-cloth liberally rolled in very fine sand such as we have here on the beaches of southwest Florida (nearly powdery), again across the blade.

As of an alternative to PropSpeed, I have not found anything effective for very long as cavitation across the blades quickly wears away the coating. When I was young, we were able to buy Whale Oil and, believe it or not, that did inhibit the growth of barnacles etc on the running gear (Eric Hiscock told us that trick). Of course one had to re coat the works often. Then, I could endure the cold water in Sausalito Yacht Harbor with an oily sponge, now, not-so-much (which is why we're here in Florida!). Believe it or not, I have found that Neosporin Ointment will inhibit growth on a prop and the impeller blades of a knot-meter, but of course, that stuff is costly and washes away quickly. Another old--makes me look young--friend, swears by a mix of Lanacote and Red Chili Pepper that he glops on his Prop...

N'any case...I am informed that it is time for chores.
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Old 05-11-2011, 09:47   #22
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

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Originally Posted by Cormorant View Post
I'm guessing they're just taking theory to a logical extreme. Scratches and burrs on your prop cause mini-turbulence and mini-cavitation, and eventually loss of prop efficiency. In the case of barnacle scrubbing, probably nothing you could measure. But they just want to steer you away from the possibility. . . .
That's my guess, plus a little CYA as another post speculated.
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Old 05-11-2011, 10:12   #23
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Re: Suggestions for removing Barnacles from a Bronze Propeller

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Originally Posted by svHyLyte View Post
Perhaps the foregoing is entirely true on your yacht but I can assure you that on ours, a newly cleaned prop has an easily discernible difference with our 2-blade 20" Gori folder. It is also measurable--and material--in terms of our fuel burn rate which drops to a tad over .5 gal/hour from .9 gal/hr to average 6 knots through the water under power. The difference may not be meaningful on your yacht but whereas we only carry 47 usable gallons, it is to us.
I think you are misunderstanding my point and I am in agreement with you but we seem to be comparing apples and grapefruit here. I did not say or mean to imply in any way that there is no measureable difference between a clean prop and a dirty or fouled prop. I also see the differences you claim comparing a clean prop to one with even a little bit of fouling. However, I have never seen that magnitude of difference between a brand new, shiny prop and a clean and smooth but not polished, buffed, shiny older prop in any boat I've ever owned, sail or power (I've only owned boats, never been rich enough to own a yacht ).

The point I'm trying to make is that using a scraper on a prop, as long as one doesn't leave gouges and nicks, will not result in a measureable difference in performance compared to one cleaned only with acid, plastic or other means.

Plus, unless you buy a new prop every couple of years, it is inevitable, at least every where I have ever motored, that your prop will end up with minor nicks and dings from flotsam and jetsam, old fishing lines, crab pot lines and what ever other garbage you inevitably encounter on the water. In real world terms, a banged up leading edge on the prop will have a greater effect on the efficiency than the very minor difference in
smoothness on the blade surface.





Quote:
Originally Posted by svHyLyte View Post
As for ProSpeed, it certainly does not leave a mirror surface but, at least where we are moored, it does an excellent job of keeping growth off the Prop tho' at some cost. For me, the cost is worth it as when I need power out of that Prop, I need it, as we maneuver in very tight circumstances in our mooring..
I am also not disputing the benefits of Propspeed and it will be on my prop when I launch. I have also had to maneuver in some tight spots and my old Westerbeke is not exactly over powering my boat.


Quote:
Originally Posted by svHyLyte View Post
For a thorough discussion of the matter, I refer you to CA ("Tony") Marchaj's text, "Sailing Theory and Practice", (c) 1964, pages 239-242.

N'any case...I am informed that it is time for chores.
Would find that of interest I'm sure. Will look for a copy.


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N'any case...I am informed that it is time for chores.
Chores on a Saturday? Saturday is for boating.
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Old 05-11-2011, 11:34   #24
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Re: Suggestions for removing Barnacles from a Bronze Propeller

Coffee break..

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Originally Posted by skipmac View Post
...

Chores on a Saturday? Saturday is for boating.
Regretably, the yacht's on the hard having a bottom job and insurance survery so there's no escape...

The two most intrusive calls one ever gets (at least at our house) seem to be: (a) the Call of Nature; and, (B) the "Have you fixed xyz yet and if not, will you PLEASE!!!" (insert your own whatever for xyz), both with similar urgency.
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Old 05-11-2011, 11:35   #25
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Talking Re: Suggtestions for removing Barnacles from a Bronze Propeller

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I think that you should either swim faster, or take your jewelry off before entering the water.
Gord,
I had to read that twice.
Pretty subtle.
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Old 07-04-2014, 17:43   #26
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

I'll be giving my prop its annual service sometime in the next few days by first soaking it in vinegar, then scraping off whatever remains using a windshield snow-scraper, and then polishing it on my buffing wheel. That's because when I bought it, the guy who sold it to me said "nothing harder than a windshield scraper, ever."

Why not? This is for a sailboat with a fairly slow-turning prop. Surely micro-scratches can't hurt!

Or can they?

Here are two reasons they might.

1. Barnacles need to grab something to grow (as does weed). The fewer micro-scratches, the better. After years of messing with my prop, I can say with confidence that I get less growth in years where I've polished than in years where I've scraped (which I did with my former 2-blade prop).

2. Cavitation. That's those little bubbles that form on the front side of the prop when it's under load. Basically, the water is boiling there, not due to heat, but due to reduced pressure (the same way water boils at a lower temp in the Rockies). (That reduced pressure is part of what draws the prop ahead through the water. All "Bernoulli is a crock" crackpots start ranting here, please.) Now think back to high-school chemistry: when you wanted to boil stuff in the test tube, you always had to put these little limestone "boiling chips" in there. Why? Because the tiny cracks and rocky shape on the surface provided "nucleation" points for the boiling -- they helped the water start to boil. What do microscratches on your prop do? I'll bet that they provide the same sort of nucleation site to start cavitation earlier. I've got no proof (except for understanding the geometry and physics of the situation). But it might be fun to set up an experiment in a tank and see whether we can induce cavitation sooner in a scratched prop than a smooth one. Is cavitation bad? You bet. Because when those little bubbles collapse back down, they do it with a WHAM, and you can get pitting on the prop from that.

This is all just conjecture...but I believe it enough to pop the prop off each winter, remove the barnacles, and spend half an hour polishing it.

--John
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Old 07-04-2014, 18:05   #27
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

Preferably dont gouge it, scrape with a small spatula with rounded corners and bronze wool if you wish. The rest is bunk for your use.
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Old 07-04-2014, 18:40   #28
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

Wow. Thanks, Cheechako, for that insightful analysis. Maybe it is all bunk.
But as for smooth-versus-rough/barnacle growth, the science says you're wrong: See this paper.

See you on the water.

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Old 07-04-2014, 19:35   #29
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

I've had some luck with Lanocote Prop and Bottom. It seems to last about 6 months when applied on the hard and leaves a quite smooth surface. You heat the prop witha heatgun and the stuff lows on in a thin self leveling layer. It can be repplied in the water but we have found that the metal needs to be extremely clean when doing so. A good scrubbing with a scotchbrite pad seems to be enough. If the metals not clean the stuff will not adhere. In the water does not give you the nice smooth cloating that you get applying it on the hard. For people who pull their boat every season one treatment in the spring might get you through the whole summer.
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Old 07-04-2014, 19:41   #30
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Re: Suggestions for Removing Barnacles from a Bronze Propeller

I don't think the small gouges and scraps cause a decrease in performance but they will create a weak spot in the blade. Small gouges will concentrate forces to a small area of the blade, sanding the nick or gouge smooth will help prevent breakage.

I have owned aircraft for many years and it is very dangerous to fly around with even very small nicks or gouges in the prop with out dressing them. This is done with file and sand paper to smooth and radius the nick and polish out any scratches or gouges.
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