Effect of Prop Antifouling on Prop Anode Wear?

[Dockhead]

Originally Posted by s/v Jedi

Surprised that nobody mentions the Gori 3-blade which has very little drag while sailing and has the "overdrive" setting for motorsailing; looks like a viable compromise between fixed, variable and feathering prop

I'm still happy with my Maxprop.

I spent a month on board a boat with a Gori. It's a very good prop, and if I couldn't have some kind of a variable pitch prop, that's definitely what I would have. A two speed transmission is definitely far better than a one-speed one.

Maxprop is also great, very efficient when feathered, very powerful, beautifully made. It's standard fit to Oysters. But fixed pitch -- so a one-speed transmission.

I will have a Hundested on my next boat. The only disadvantage it shares with the Autoprop is ridiculous cost; plus YOU control the pitch, it's not automatic. The platonic ideal of a boat propeller. Hundested Propeller A/S. Only those with 150 horsepower or more need apply; hence I can't fit it to my present boat, which only has 100.

"The Advantages of Controllable Pitch Propellers
A fixed propeller, designed for maximum speed, cannot give maximum power at low speed, while a fixed propeller designed for power, cannot achieve maximum speed.
With a controllable pitch propeller it is always possible to obtain full utilization of the engine, irrespective of the purpose of the vessel.

Maximum horsepower can be taken from the engine – without overloading – by changing the pitch.

Even if the engine drives a winch or a shaft generator, the number of revolutions can be kept constant – and the speed of the vessel can then be regulated by means of the propeller pitch.

At speeds lower than the maximum speed the engine’s fuel consumption can be reduced considerably by increasing the pitch and lowering the number of revolutions while maintaining the required speed. In this way the loading of the engine and the total efficiency of the unit is increased.

When using sail and engine power at the same time the correct pitch can always be obtained so that wind and engine together are utilized in the best possible way.
Prompt and inexpensive replacement of individual blades in case of damage to the propeller.

Engine idle speed on a fixed pitch propeller vessel often propels the vessel too fast for docking manoeuvres whereas a CP propeller offers superior low speed vessel control"

[Emmalina]

Gave up buying anodes a while ago so I make my own. Last at least 3 yrs which is not hard as we have a galvanic isolator and we don't stay in marinas ! Boat yards are a great source of old zinc ! Tried many types of paint but the most they last is 6 months so don't bother anymore

[Emmalina]

Originally Posted by Dockhead

Most people around here polish their props and leave them as bare metal. And I also do that. For some reason, the prop doesn't foul all that much.

But my prop anodes wear intensely, and are gone in 4 months, which is the limiting factor for me for a lift out.

For some reason, having a shaft anode on doesn't seem to make a lot of difference. I don't understand that.

I wonder if I were to paint my prop with antifoul, whether that would slow down anode wear by reducing contact with sea water?

Anyone have any experience?

Haul out to change a prop anode ??????? really

[Dockhead]

Originally Posted by Emmalina

Haul out to change a prop anode ??????? really

Obviously not just to change a prop anode.

We scrub off every two months in the summer; maximum every four months.

Grease the prop; change the other anodes. Inspect the cutless bearing. Lubricate the through hulls.

And we don't always haul out -- sometimes we dry out.

[savoir]

The wiring diagram in post 74 doesn't show the boat's minor 12v (perhaps 24v) electrical components all of which will be earthed to somewhere. On top of that, a wiring diagram only shows things as they should be not as they actually are. Unless the boat has only ever been serviced by whoever prepared the diagram some things will have changed over the years.

Next time you are on board check for green wires on the engine, gearbox and engine mounts.

[Dockhead]

Originally Posted by savoir

The wiring diagram in post 74 doesn't show the boat's minor 12v (perhaps 24v) electrical components all of which will be earthed to somewhere. On top of that, a wiring diagram only shows things as they should be not as they actually are. Unless the boat has only ever been serviced by whoever prepared the diagram some things will have changed over the years.

Next time you are on board check for green wires on the engine, gearbox and engine mounts.

That's not a general wiring diagram -- it's "Cathodic Protection and Bonding Scheme". Just that. The electric components are earthed to two master negative buses which are connected to the negative side of the battery bank.

Nothing about this section of the boat's wiring has changed. When I bought the boat, she was almost new and the PO had not installed a single piece of electrical equipment. I have kept the original system as intact as possible as it is very well designed and executed and practically trouble free.

However, this "Cathodic Protection and Bonding Scheme" is a mystery to me -- this is already beyond my electrical knowledge. Which is why I was asking.


Maybe there's nothing to worry about. I use anodes at a fairly rapid rate, but not really faster than I would need to scrub off anyway. And the anodes are wasted at a very consistent rate, and there has never been any damage to anything. Maybe it's all working the way it's supposed to.

[UNCIVILIZED]

Originally Posted by a64pilot

I don't think you "get" the whole prop thing, it is not which makes us the most efficient motorboat, I can tell you the answer to that is a fixed two or maybe three blade, and a whole LOT cheaper too. Efficiency in that regard is sort of irrelevant to me, and I think Dockhead as well.
The idea is to have a variable pitch prop, one that will provide thrust at low engine RPM, even if the boat is making way under sail.
You can't do that with ANY fixed pitch prop unless your way over propped when not under sail, reason is today I am pure motoring, tomorrow I may be sailing at three kts, but wish to go faster, then I can crank the engine and run it at 1000 RPM and make seven kts.
With a fixed pitch prop it would take probably 1400 RPM to make any significant thrust, and 1800 to put me at seven Kts, this isn't theory, that is the way it was on my boat, before the Autoprop, and I was over propped.
Ideally I'd like a controllable pitch prop that I was in charge of setting pitch, I' d install a pyrometer and set prop pitch by exhaust temp, but alas that doesn't exist for a 40 HP engine, or if it does, I don't know of one.
This state of affairs, I'm familiar with. And as I'd stated earlier, I'd LOVE it if someone would come out with a range of such props for engines between 20-25hp & 50-75hp or so. Because the setup which you're describing is exactly what, ideally, I'd have in a boat.
Though, unfortunately, such beasts don't seem to exist to my knowledge either.

So I settled with an auto pitching prop, which as all things are, is a compromise.
Autoprop is expensive, complicated and does not give much thrust when the boat speed is zero, but like I said in 6 kts of apparent wind on a reach, I can motor sail at seven kts, with the engine at 1000 RPM, which I like, fuel burn is low, but to me more importantly, engine noise is a lot less. 1000 RPM isn't nearly as obnoxious as 1800.

Sent from my iPad Pro using Cruisers Sailing Forum

What you (& Dockhead) are saying with regards to your prop choices, & motoring/sailing styles makes sense/has sank in. Although I'll admit, it's not an area which I've much considered, nor looked into. As such isn't my style. And there's NO judgement in that. It's simply that I prefer vessels to/be set up, so that she sails at wind speed, or, minimally, 2/3 there of, down to 5kts of wind or less. Thus, my focus has been on sailing when it's light, not motor sailing. And consequently, on how to set up boats to perform well in such conditions.

[a64pilot]

It seems I spend a lot of time out sailing in 6 kts of wind, or less.
I'm to blame for that as only get one real vacation once a year, and I take it in Summer as the kids are out of school and the wife off of work, and Summer is when it gets HOT and the wind dies.
If you can't wait for the forecast to change, then you need to be able to motor sail.
The really odd thing is my IP is not all that much of a pig, I've been out numerous times in light wind and not been left behind by lighter, and supposedly much better light wind boats.

In a year when I retire and we leave, then I can wait til the forecast changes and not have to motorsail so much.

From a pure financial / performance perspective, on my IP, I don't think you could beat a fixed two blade prop, index the shaft and fit a brake so that you could align the prop with the deadwood of the keel (keel is probably 6" thick), lock the brake and have very little more drag than a feathering prop would, and what is cheaper and less maintenance than a fixed two blade prop?

Now I'm not a cruiser yet, but from what little I have done, there is value in having a boat that can motor, motorsail and sail well. You need all three I think, but then it is my nature to over prepare.

[Dockhead]

Originally Posted by a64pilot

It seems I spend a lot of time out sailing in 6 kts of wind, or less.
I'm to blame for that as only get one real vacation once a year, and I take it in Summer as the kids are out of school and the wife off of work, and Summer is when it gets HOT and the wind dies.
If you can't wait for the forecast to change, then you need to be able to motor sail.
The really odd thing is my IP is not all that much of a pig, I've been out numerous times in light wind and not been left behind by lighter, and supposedly much better light wind boats.

In a year when I retire and we leave, then I can wait til the forecast changes and not have to motorsail so much.

From a pure financial / performance perspective, on my IP, I don't think you could beat a fixed two blade prop, index the shaft and fit a brake so that you could align the prop with the deadwood of the keel (keel is probably 6" thick), lock the brake and have very little more drag than a feathering prop would, and what is cheaper and less maintenance than a fixed two blade prop?

Now I'm not a cruiser yet, but from what little I have done, there is value in having a boat that can motor, motorsail and sail well. You need all three I think, but then it is my nature to over prepare.

You're not to blame for it -- it's your latitude

[Dockhead]

Originally Posted by UNCIVILIZED

What you (& Dockhead) are saying with regards to your prop choices, & motoring/sailing styles makes sense/has sank in. Although I'll admit, it's not an area which I've much considered, nor looked into. As such isn't my style. And there's NO judgement in that. It's simply that I prefer vessels to/be set up, so that she sails at wind speed, or, minimally, 2/3 there of, down to 5kts of wind or less. Thus, my focus has been on sailing when it's light, not motor sailing. And consequently, on how to set up boats to perform well in such conditions.

Yep.

For many cruisers, the motor is a substitute for light air sails. And there's nothing wrong with that I guess.

I love to sail (not all cruisers do), and I have worked really hard trying to get my boat to sail better, and the result is that now with the new larger headsail (I now have two different carbon headsails) I can make 2/3 of wind speed over a fairly wide range of conditions. This allows me to sail more than previously, in conditions where previously I would need the motor.

The other goal was to be able to make 5 knots VMG to windward in 15 - 20 knots of wind. I didn't quite achieve that (only in absolutely perfect conditions), but my ability to get dead upwind has been enormously improved, especially in stronger conditions where my blade jib comes into its own. This also allows me to sail more than previously.

But despite all that my motor is working for a significant percentage of miles I make, and the variable pitch prop is genius for this.

I'll need it less when I eventually set up a Code 0 for light conditions, but at the moment, motorsailing is my substitute for light air sails.


For a boat set up like you like -- a light racer/cruiser, or a catamaran, for example, with a good sail inventory, the Autoprop is no good because of drag, and you can't buy a Hundested in that size. So variable pitch is just not an option. In that case, I think I would go to Gori with the overdrive.

[savoir]

Originally Posted by Dockhead

That's not a general wiring diagram -- it's "Cathodic Protection and Bonding Scheme". Just that. The electric components are earthed to two master negative buses which are connected to the negative side of the battery bank.

Nothing about this section of the boat's wiring has changed. When I bought the boat, she was almost new and the PO had not installed a single piece of electrical equipment. I have kept the original system as intact as possible as it is very well designed and executed and practically trouble free.

However, this "Cathodic Protection and Bonding Scheme" is a mystery to me -- this is already beyond my electrical knowledge. Which is why I was asking.


Maybe there's nothing to worry about. I use anodes at a fairly rapid rate, but not really faster than I would need to scrub off anyway. And the anodes are wasted at a very consistent rate, and there has never been any damage to anything. Maybe it's all working the way it's supposed to.

Oh well, I can't add any more then. My gearbox has several green wires bolted to it and I'm still not sure what they all do. One day I'll trace them to see what they are earthing. FWIW I have two shaft zincs which last two summers. The prop is a Max and its zinc only lasts one year but I put that down to bad design. Max put their mounting screws way out near the rim of the zinc and that is where they always corrode first leaving the center almost new. The prop is painted with Pettit zinc paint and despite being 6 years old looks like new with zero pitting. The paint is only medium at killing barnacles.

[Rustic Charm]

Originally Posted by savoir

Oh well, I can't add any more then. My gearbox has several green wires bolted to it and I'm still not sure what they all do. One day I'll trace them to see what they are earthing. FWIW I have two shaft zincs which last two summers. The prop is a Max and its zinc only lasts one year but I put that down to bad design. Max put their mounting screws way out near the rim of the zinc and that is where they always corrode first leaving the center almost new. The prop is painted with Pettit zinc paint and despite being 6 years old looks like new with zero pitting. The paint is only medium at killing barnacles.

All this talk of earthing and zinc's and gearbox's and green wires has got me thinking about mine. My whole system is earthed directly to the motor and of course that one comes from the Neg battery terminal. There are no wires to my gear box or anywhere else? Everything that requires earthing goes back to the Neg on battery terminals. ???

Tonight I'll be wiring up a new chart plotter and I know it has the usual 'earth' wire and an AF wire. A small black wire which is meant to go to my 'earth'. But that's the same as where I'll be wiring up the main black earth wire.

[four winds]

Rustic, I believe your boat is setup like mine. Green bonding bus wires to the engine/trans and 12v negative bus and battery negative cable to the engine/trans as well. All this finds its way to seawater thru the propshaft. This is common practice I think on US made boats. Yours isn't US made possibly but still the same maybe. I suppose a flex coupling on the shaft may differ though.

European boats separate the bonding from 12v negative and is considered a better choice by many. Though if the bonding finds water via a hull anode and the dc negative finds it via negative battery cable to the engine and then the shaft I'm not sure just how much difference that really is.

Scrubbed the hull today and my shaft anode shows little lost zinc after five months. Original through hulls and twenty year old prop still like new.

Interesting topic to try to understand as it impacts both maintenance costs, performance and safety concerns.

[Rustic Charm]

Originally Posted by four winds

Rustic, I believe your boat is setup like mine. Green bonding bus wires to the engine/trans and 12v negative bus and battery negative cable to the engine/trans as well. All this finds its way to seawater thru the propshaft. This is common practice I think on US made boats. Yours isn't US made possibly but still the same maybe. I suppose a flex coupling on the shaft may differ though.

European boats separate the bonding from 12v negative and is considered a better choice by many. Though if the bonding finds water via a hull anode and the dc negative finds it via negative battery cable to the engine and then the shaft I'm not sure just how much difference that really is.

Scrubbed the hull today and my shaft anode shows little lost zinc after five months. Original through hulls and twenty year old prop still like new.

Interesting topic to try to understand as it impacts both maintenance costs, performance and safety concerns.

Mine is a French boat, but not with the origional engine so who knows how it was origionally set up.

Do you know if I'm correct in joinging the AF thin black wire of the chart plotter to earth? I can't think of anywhere else to send it

[four winds]

Hey Rustic, sorry, had to go do some laundry.

When I read your post mentioning "AF" wire it stumped me. Which of course bugged me since having a reasonably good grasp of electrical gadgets. My simple Garmin 441s has only a hot and ground, tranducer, plus the tiny wires for DSC to the vhf.

What plotter do you have? For the life of me I can't cipher what AF stands for. Bugs me.

Edit,.... oh, and the NMEA data wires. If it is that then there is a data negative wire, which definitely doesn't go to ground. Rather at least not the earth ground.