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post #11 of 20 Old 02-23-2018 Thread Starter
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Re: coppercaot on saildrive

@boatpoker

"electrolysis and galvanic corrosion" Sorry I did not use the right term. I should have said "galvanic corrosion" It was my mistake.
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post #12 of 20 Old 02-23-2018
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Re: coppercaot on saildrive

P435

I have used different coatings on the leg but from a galvanic corrosion standpoint, it doesn't need anything as the fibreglass is the barrier. I have used the white anti-fouling made for aluminum but it is expensive and did not work particularly well. I have used regular anti-fouling (against good practice recommendation) because I have faith in the barrier coat. As often as not, I just paint it with regular enamel such as Rustoleum or Tremclad and these work okay...I do this as much to make it look pretty in the boat yard as anything else.
Personally, I think that really good anode protection is most important, in addition to the leg anodes I hang a large grounded zinc over the transom while at my home dock, which of course is most of the time.
It should be noted that I haul my boat annually and so the leg does not get out of control marine growth.
I have not used Coppercoat.
You obviously have some pricey equipment, if it were mine I would apply the resin or epoxy barrier coat and cover it with anti-fouling made for aluminum outdrives.
I do not give this advice as a professional, it is common sense that works for me.
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Re: coppercaot on saildrive

@paulinnanaimo

Thanks for your interesting post.
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Re: coppercaot on saildrive

I'm think the mechanical problems associated with epoxy coating the sail drive are referring to mechanical bonding of pieces. You will need to remove the lower unit for various maintenance functions. Coating the entire unit in epoxy may make it difficult to separate the parts because they have been glued together, thus greatly complicating routine maintenance.
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Re: coppercaot on saildrive

I can't comment on the routine maintenance required for a Volvo, mine only needs regular gear oil changes. There are 2 screws that need to be removed. Using a suitable tool, I chip the resin from the slot; and then using a large bladed screwdriver simply torque the screw out. There isn't enough resin contact for a strong bond, the screws come loose very easily.
It is necessary to protect these areas, it is precisely where corrosion often gets a foothold.
Perhaps P435 would care to comment on Volvo routine maintenance.
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Re: coppercaot on saildrive

Quote:
Originally Posted by lillia28 View Post
I'm think the mechanical problems associated with epoxy coating the sail drive are referring to mechanical bonding of pieces. You will need to remove the lower unit for various maintenance functions. Coating the entire unit in epoxy may make it difficult to separate the parts because they have been glued together, thus greatly complicating routine maintenance.
The point at which a saildrive leg detaches from the gearbox is inside the boat and wouldn't be coated with epoxy. Even if it was, the joint is a flange with gasket, so epoxy coating wouldn't interfere.

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Re: coppercaot on saildrive

Bringing a bit more reality into the discussion. I took the proposal of @paulinnanaimo and took pictures of the already sandblasted saildrive and propeller.

In respect to coppercoating saildrive and propelle the critical area are:
1 - Cooling water openings in the leg of the saildrive
2 - Screw at bottom of saildrive (to change oil and do pressure test)
3 - Srew at the end of the propeller spinner
4 - Through-hole at the spinner
5 - Small metal pieces to not allow the spinner to rotate free against the axis by inertia

See also attached pictures.

There are 2 more screws to remove the lower horizontal shaft of the saildrive but these screws are covered by the anodes.

Assuming you would want to coppercoat saildrive and propeller. What would you do with these areas?
Attached Thumbnails
SDrive_BottomScrew_SandBlasted.jpg   SDrive_AnodesScrews.jpg   PropellerSpinner_ThroughHole.jpg   PropellerSpinner_RotationalFixingElements_SandBlasted.JPG   Propeller_EndScrew_02.jpg  

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Re: coppercaot on saildrive

Upload volume was too big, thus saildrive picture here
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Re: coppercaot on saildrive

Quote:
Originally Posted by P435 View Post
Bringing a bit more reality into the discussion. I took the proposal of @paulinnanaimo and took pictures of the already sandblasted saildrive and propeller.

In respect to coppercoating saildrive and propelle the critical area are:
1 - Cooling water openings in the leg of the saildrive
2 - Screw at bottom of saildrive (to change oil and do pressure test)
3 - Srew at the end of the propeller spinner
4 - Through-hole at the spinner
5 - Small metal pieces to not allow the spinner to rotate free against the axis by inertia

See also attached pictures.

There are 2 more screws to remove the lower horizontal shaft of the saildrive but these screws are covered by the anodes.

Assuming you would want to coppercoat saildrive and propeller. What would you do with these areas?
None of those have any bearing on the coating, and most of them only have to do with the propeller itself. The cooling water passages you wouldn't plug up (easy), and the oil change bolt sits on a flat flange with a o-ring seal. You wouldn't be coating the flange or the bolt, and even if you coated the bolt, it wouldn't prevent it from being removed.

I wouldn't put copper coat on my saildrives, but that is just my preference. I definitely would not coat the propeller with it. The reason is that the build thickness will change the foil shape, and there is no way the epoxy will stay on it. Soon, you will get a lot of pits and failure points, and once the edge is lost, it will start peeling. This, I say from experience.

Since your drives are blasted back to aluminum, you will not have good luck simply coating them with anything because they have oxidized by now and nothing will stick well without some more prep. You will either need to etch them with a suitable aluminum etcher solution and follow that with a chromate primer, or you can sand them back to white aluminum and immediately apply epoxy while sanding. This epoxy wet sanding will get the epoxy to good aluminum.

After that, you proceed as you like with antifoul of choice. Personally, I would not put copper on the drive regardless of what form it is in. If this was necessary, I would put a thick barrier coat of epoxy on it before the copper coat. I would not trust the copper coat epoxy solution to be the only barrier between the copper and the aluminum.

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Re: coppercaot on saildrive

@colemj - Thank you so much for your opinion.

I will report what I will do - after it is done, and next in about a year when I see results of my decision.
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