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Epoxying my ferro hull

ferro epoxy

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#1 Seasick sheamus

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Posted 17 November 2015 - 06:21 AM

Hi Everyone.

 

I have just completed scraping my 50 ft tahitian back to the bare ferro hull. It has never been epoxied. I'm not sure what was under the anti-foul. Maybe a rubber paint? The hull was professionally built and is very smooth.

I will post a vid next weekend so everyone can see....

 

Here's my question............

 

I would like to protect the hull below the water line. I want to give it a protective coating that will last for years. I am leaning towards a modern high build coal tar epoxy. 

 

is there a better way or what has everybody else done...

 

thanks....

 

 


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#2 wheels

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Posted 17 November 2015 - 04:49 PM

Epoxy Tar will work, or  even Ordinary clear Epoxy resin can be used. There are some really good Epoxy paints now. Have you heard of Hempels Paints? they have an Epoxy Mastic coating which is great on Concrete.
The only issue with Epoxy, is that once the stuff has fully cured, very little will stick to the stuff, because it is so hard. Although I have never had a problem with the AF not staying put.


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#3 haiqu

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Posted 17 November 2015 - 05:57 PM

While we're on the subject of bottom coatings, does anyone have a suggestion as to the right antifoul? Colin Brookes of Hartley & Brookes states that copper based stuff shouldn't be used due to electrolysis issues, and TDTs have been banned. So, what's left that works effectively?


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#4 wheels

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Posted 18 November 2015 - 06:04 AM

Copper based AF's on FC Hulls is perfectly OK. You cannot use copper based AF's on Aluminium Hulls. Not sure where you got that info from. I have never read anything like that from Hartley/Brooks.


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#5 Seasick sheamus

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Posted 18 November 2015 - 06:57 AM

Spoke to Hempel...they don't make their coal tar epoxy mastic anymore (due to difficulty in getting raw materials), but they do a similar product called Hempadur mastic 45880 £50 for 5 litres. They recommend diluting the first coat by 20% into bare ferro!!!

I'm going to pester them again tomorrow for a bit more tech detail!!!!


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#6 paulajayne

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Posted 18 November 2015 - 08:36 AM

Spoke to Hempel...they don't make their coal tar epoxy mastic anymore (due to difficulty in getting raw materials), but they do a similar product called Hempadur mastic 45880 £50 for 5 litres. They recommend diluting the first coat by 20% into bare ferro!!!

I'm going to pester them again tomorrow for a bit more tech detail!!!!

I would dilute down to  a 50/50 and spray the first coats on - Having  seen your hull that should give a very good base.


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#7 haiqu

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Posted 18 November 2015 - 02:32 PM

Copper based AF's on FC Hulls is perfectly OK. You cannot use copper based AF's on Aluminium Hulls. Not sure where you got that info from. I have never read anything like that from Hartley/Brooks.

 

"The main point to remember is that on no account should you use any copper based paints on a ferro-cement hull, it is not electrically compatible. The basic rule of thumb for antifouling a ferro-cement hull, is treat it the same as if it were a steel hull." - Brookes, "Ferroboats", p76 (CD edition)

 

He also discourages the use of coal tar epoxy because it can't be removed.


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#8 wheels

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Posted 18 November 2015 - 04:18 PM

Spoke to Hempel...they don't make their coal tar epoxy mastic anymore (due to difficulty in getting raw materials), but they do a similar product called Hempadur mastic 45880 £50 for 5 litres. They recommend diluting the first coat by 20% into bare ferro!!!

I'm going to pester them again tomorrow for a bit more tech detail!!!!

That's the one I was referring to. I did say Epoxy Mastic, not Epoxy Tar. I could remember it had two or three 8's in the number, but couldn't remember the actual number. It's a good product.


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#9 wheels

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Posted 18 November 2015 - 04:27 PM

"The main point to remember is that on no account should you use any copper based paints on a ferro-cement hull, it is not electrically compatible. The basic rule of thumb for antifouling a ferro-cement hull, is treat it the same as if it were a steel hull." - Brookes, "Ferroboats", p76 (CD edition)

 

He also discourages the use of coal tar epoxy because it can't be removed.

 Copper is fine on steel and most certainly OK to use on Ferro Cemment. Trust me. It is Aluminium that you have to keep Copper away from.
Remember that Steel has an Epoxy barrier coat and some paint systems have three different types of coatings to form the protection barrier. The Cement plaster does exactly the same.
I have been using copper based AF for 15yrs now on my boat and have no problems.

Now re the comment Brookes made about treating FC as if it were a steel vessel, was not referring to AF. His comment was actually in reference to Magnetism and swinging a compass.


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#10 haiqu

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Posted 18 November 2015 - 04:43 PM

 Copper is fine on steel and most certainly OK to use on Ferro Cemment. Trust me. It is Aluminium that you have to keep Copper away from.
Remember that Steel has an Epoxy barrier coat and some paint systems have three different types of coatings to form the protection barrier. The Cement plaster does exactly the same.
I have been using copper based AF for 15yrs now on my boat and have no problems.

 

OK. None that you know of anyhow.

 

 

Now re the comment Brookes made about treating FC as if it were a steel vessel, was not referring to AF. His comment was actually in reference to Magnetism and swinging a compass.

Now you're just making sh*t up. Read the quote from Brookes again. He's talking specifically about antifouling and it being electrically incompatible with the steel armature. i.e. galvanic action. Nothing to do with compasses.

 

The effect on aluminium would be more drastic, it's more anodic than steel, but using either one with copper antifoul is a bad idea.


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