epoxy to ferro

[hooked on water]

Hi all
wondering if anyone has any ideas on lining the inside of my ferro yacht with epoxy and a few layers of glass for added protection. Also looking at making my inbuilt water tanks using this

Any help would be good thanks

[Boracay]

I'm thinking that a thick layer of epoxy/fibreglass would pull the cement covering the reinforcing away from the steel.

In engineering terms you want the coating to be weaker than the cement so that the coating fails first.

In this case it could be that thinner is better.

[hooked on water]

so you are thinking to just do a thin coat of epoxy to seal and protect, and maybe a thinner layer of glass for a bit of strength, or no glass at all

[cooper]

Hi across bass straight!
No problems at all with straight epoxy on ferro. A lot (including mine have an epoxy coat on the outside of the hull as a moisture barrier.The lining of tanks is fine. Expansion differences between the two type of material (glass matt epoxy/ reo cement)can delamenate the fiberglass. The concrete is tough stuff. If epoxy pulls off concrete, it only pulls surface material . It is very unlikely to remove a chunk to the armature. Do you really need to skin the inside ? If it is in a "danger" area like an anchor locker then I would be inclined to line it with epoxy coated ply that you can remove for inspection. Else where, I wouldnt worry about it. I have reasonable quality house enamel on the inside of mine and it holds up very well. If you are worried about the structural integrity of the hull, thats a different thing.

[Wotname]

OK, I know bugger all about ferro but I do know a bit about epoxy and a bit about wood. Very simply put, if you cover one side of the hull with epoxy, you really should cover the other side if you want to get any advantage of the epoxy. In the situation you are describing, you should encapsulate the hull or not bother i.e. do both sides or none at all (unless you need some local mechanical coating of part of the hull) . IMHO - I am not a structual engineer.

[Alan Wheeler]

OK firstly, Epoxy and cement have two completely different expansion rates. So anything more than a "painted" layer on the hull is not a good choice. If you intend to actually Glass/Epoxy reinforce the inside of the hull, bad idea, don't do it, nor does it add any strength or added protection, only weight.
FC does not need waterproofing. It works by reverse Osmosis. An epoxy coating is applied to the outside of the hull so as further applications of a paint system has something to adhere to. An Epoxy coat is not required for a moisture barrier, even though many believe that is what it is for.
A FC hull can benefit greatly with Epoxy barrier coats being applied internally in the area's of the engine room. The one and only major problem with FC is that Diesel and Oil can leach through the cement and create major issues. So coating area's like the engine room and Bilges, especially under any fuel tankage area's will protect the cement from petroleum contaminations and leaching.

[Wotname]

That seems to make sense; looks like I am right about something -

Originally Posted by Wotname

OK, I know bugger all about ferro ...... - I am not a structual engineer.

[hooked on water]

thanks for all the help
I am doing the outside of the hull totally in epoxy, and was going to coat inside with glass for added strength and protecting the concrete. I will do as you say Alan, and just give a coat to the inside, and use it for forming my water tanks . The tanks I am using the hull and ply to build, epoxy coated, inside and out. All with an inspection opening
I was going to use the epoxy coating for all the inside of hull to make a smoother finish inside cupboards also.

Cheers
Greg

[Alan Wheeler]

A cheap commonly used coating for bilges and engine compartments is Epoxy Tar. Slap it on good and thick. Probably not the best for fresh water tanks. It may taint. But it is impervious to oil. Some just leave the water tanks bare cement. But you need to be sure that the tank was made really well. I have hairline cracks in my tank and it leaks out into the adjacent bilge. I can't get at the tank now to be able to seal it from the inside, so I have to work from the outside. I have nearly got is solved. One leak(I hope) to go.

[cooper]

Allan my hull was formed over a timber blank. It is only 3/8th inch thick. It has 5 layers of mesh in that thickness, that where pulled down very hard (hydraulic) so that it took the shape well. Regardless I have armeture very close to the surface and by virtue a epoxy barrier coat helps top stop any surface rust. The boat was built forty years ago. Not a very good "sailing" photo but it shows the hull. It has since been repainted in a lighter aqua blue. The use of an epoxy barrier coat works well to stop any fissures or minute cracks allowing water to get to the steel. And as you have said gives a good bond coat for most paint finishes. Being a ferro nut I have to agree and stress that they are water proof without anything else, take concrete water tanks as a water proof poor cousin !!

[MidLandOne]

Originally Posted by Alan Wheeler

A cheap commonly used coating for bilges and engine compartments is Epoxy Tar. Slap it on good and thick. Probably not the best for fresh water tanks. It may taint.

It is also supposed to be a carcinogen and I suspect it is one of the things where that risk is not over stated. In fact I thought it was now either banned or difficult to get but that may just because it has been over 20 years since I have used it that got that into my head (Altex do an epoxy they call Altra-Tar but it is actually not a tar epoxy).

For Hooked On Water, Altex (who are also in Australia) do epoxy coatings for steel, cement, masonry, etc approved for potable water storage and which are widely used in the meat and food processing industries eg from the Altra Shield range. The same coatings are also ok for general epoxy coating which is useful as some are only available in around 4 litre minimum quantities and I don't recall them being significantly different in price to the not approved for potable use ones that one would normally splash around. We use their coatings in our own steel tanks.

[Wotname]

Hooked, IIRC, you have access to the Jotun range; if so, they do an approved food / potable water standard two pack epoxy paint that is used (among other things) in the wine industry. Can't recall the name off hand but have it somewhere in a file at home.
Sounds good to have a wine product lining the water tanks!!!

[MidLandOne]

Originally Posted by Wotname

Hooked, IIRC, you have access to the Jotun range; if so...

I have used Jotun in Tasmania and that and good advice is easily available as they have an office in Launceston. I have met one of their reps in Hobart but can't remember now if he was based in Hobart or travelled down from Launceston. Most paint reps are very happy to have a look at what you are doing and give advice, even for a smallish job if not too far out of their way.

[hooked on water]

Thanks guys
I have the epoxies and am using all Jotun range
they are in Derwent park here in Hobart and have dealt with the rep for some time
good products and good price
Thanks all for you assistance, am not going to use any glass other than for bonding of ply to the hull as additional bonding only.
but am coating the whole internal hull for protection
a bit of internal mesh has surface rust from being exposed and 12 years of sitting exposed during construction, so needs protection anyway
Hope to have it in for christmas, wish me luck

[MidLandOne]

Originally Posted by hooked on water

...and 12 years of sitting exposed during construction, so needs protection anyway

Long shot this question, but it wasn't the one that was sitting out at Margate down at NW Bay by any chance with seemingly little happening a few years back?

John