Ferro cement anti-foul

[jet_morgan2000]

What is the best way to anti-foul ferro cement ???
Is it possible to use VC Tar or similar first ?
Any advice from all the 'Ferro cementers' ?
Cheers,

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[jeanne]

If the hull is new, go over it with a carburundum stone to get rid of any sand on the surface. The perceived wisdom is to use epoxy primer(we originally put on 4 coats) and then put on hard racing before the last coat of epoxy fully cures. If you leave it you don't get a good bond.

In practice, we found that for the first few years we suffered from blisters which pushed off the overcoatings. These blisters got fewer every year. After quite a long time we decided that solvent entrapment from the epoxy was as much of a problem as the cement. We used to religiously primer any bare patches before a/f. If you take all paint off to the bare hull as I did once (using a chemical stripper used commercially for buildings) , it will (or should be) like marble and none of the blistering seems to have done any harm. We now just rub down whatever is left on the hull and apply hard racing, even onto the bare cement patches. Our sister ship prefers to pitch epoxy every other year after a good rub down, then a/f (but he has been shot blasted once). We prefer hard racing so that we can do a scrub off. We have used several makes over the years; Jotun tropical is good, now we use Blakes.

In the light of 20 years experience with the stuff, nowadays I'm not sure I would bother with the epoxy, just put the a/f straight onto the hull (after conventional undercoating perhaps). All the paint manufacturers do leaflets, but none of them agree!!

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[jet_morgan2000]

Many thanks for the reply Jeanne I will give it a lot of thought !!!
Have you any suggestions about self-surveying a Ferro boat ?
There seems to be a lot of 'technical' advice on the web but nothing really down to earth so to speak.
Regards !

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[jeanne]

Hi again

I don't know about self surveying a ferro boat - we built ours and had it surveyed throughout the building process. There are a lot of bad ones out there as well as some extremely good ones. Windboats were the professional builders in this country and had Lloyds A1 certificates for their hulls which were steam cured. I would go for a professional survey, but if you do it youself there are a couple of pointers.

When launched, there wasn't an ounce of filler on ours; an argument with a buoy put paid to that! When we claimed on the insurance for the damage, there was no-one who could/would do the repair, and the insurance company 'employed' us to do the repair. This entailed knocking out all the loose cement, thus making a rather large hole, then renewing the mesh, replastering, then fairing with epoxy filler. The point is this, when you tap a good ferro hull, it should ring slightly rather than knock. Where ours was damaged, it lost the ring and the extent was larger than the apparent damage. The surveyor oversaw our repair and was very happy with it. Too much filling shows a lack of care or preparation before plastering as the hull should be fair without it.

So, if you don't know the builder, knock the hull, especially at the turn of the bilge, and see if it rings rather than clunks. Ask around as well if you can and find out how the hull was plastered. A good 'one shot' is better than two shot. Look for evidence of rust, especially round deck fittings if the sidedeck is ferro as well. Any stray wire ties near the surface will rust and eventually push off the cement. This is easily dealt with early, but if left will cause the cement to crumble a bit around the defect. Also through hull/deck fittings should be isoalated from the armature with epoxy before using bolts etc. for the same reason to avoid the so called concrete cancer. Ask about the concrete mix, check that the correct sand/cement ratio was right, and how long the hull was cured (28days is usual unless steam cured) Find out who the professional plasterers were; some were artists and didn't leave an ounce more cement on the outside than they had to, others faired with too much with cement. Our hull is 5/8" thick with 1/8" on the outside on a 33ft hull. We used less mix than expected because we tied tight at short centres, so got a thinner hull and less weight with the steel/ cement ratio improved.

We have a foam sandwich coachroof/cockpit which is bonded to the ferro, but most have a plywood/timber deck and coachroof. Pay particular attention to the join. Look at the bilges - they should be clean, with few, or no rust streaks. Ours are painted with pitch epoxy. There is always the chance of some bare mesh/wire ties inside as the hull is usually brush finished. We have all the area under the saloon as water tanks which are bare ferro with ferro 'lids' and steel inspection hatches. Look in there if you can, it will show you the inside finish and you can check for evidence of rust. Ours have none, and the cement keeps water fresh.

We have a photographic record of our build showing stringers, vertical rods, good meshwork/wire tying etc and also some xrays of a few areas after plastering (I am a radiographer...!) which prove the good misalignment of the mesh in stressed areas i.e. the engine beds. Also we did a test panel on plastering day to test tensile strength later after curing. If your seller has a record, ask to see it, and any survey done before the boat was insured. You will probably have to have a survey anyway before an insurer will take on the boat. At one time, it was almost impossible to get insurance because "it was impossible to guarantee a repair" - now it is getting easier.

The used to be some good ferro 'bibles' out there, but most are out of print now; see if you can find one. Pete Greenfield wrote one, Hartley do one of their own, and there were others.

I could go on forever, but don't be put off, a good ferro boat is strong and represents terrific value as they don't have a high price because of the bad press caused by the not so good ones. Good ones are hard to tell from other materials from a very short distance away. If you want to chat, PM me and I'll give you my phone number - but be quick, I am off to Spain on 1st September to rejoin the boat!

Jeanne


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[jet_morgan2000]

Thanks again Jeanne for your answer and the time you took to explain to this novice.
Have a good trip !
Regards,
BWM
p.s. PM also sent.


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