Ferocement crack - fixable or the boat trash?

[kurtis king]

i have repaired a ferro cement Collin Archer 35' Cutter but it was no where near as bad as that. Sand blasted the hull down to the cement, then mixed a hot batch of epoxy. The leak was over the diesel tank and i remember using a propane torch to burn the leaking fuel before applying the epoxy mix. The repair lasted several years with no issues.

[fatherchronica]

Just a comment on the evolution of ferrocement construction techniques. About 45 years ago my mother was getting ready to sail south on a nice little wooden cutter from Marina del Rey, in Southern California. She showed me pictures she took when some friends she met launched a ferrocement boat they built in Venice, Cal. Very nice boat I thought. About a year or two later that same boat was on the cover of Cruising World anchored in a French Polynesian lagoon and every piece of metal in the hull could plainly be traced, like an Xray, by the orange rust flashing through the paint job. On a side note, about the same time, a painting contractor on a job I was doing bought a Frank Lloyd Wright hillside home in the Los Angeles area for a song because the rebar in the foundation had completely rusted out and the concrete was crumbling away.

[chris95040]

I've always wondered what prompts someone to build a boat in ferrocement.

Is it simply a mix of cost pressure and backyard build logistics, or is there a real benefit with respect to the finished boat?

[fatherchronica]

I am no fan, but I have met several people over the years who said that they never could have afforded to take off cruising for several years in their youth without the affordability of ferro cement boats, and one guy named Jack who sailed one he built around the Horn. And if memory serves I think I once read that the first private boat to circumnavigate Antarctica, anchoring and going ashore and such, was a ferrocement boat. So I do not poo poo them to fans.

[samfreeland]

I'm a great fan of ferro cement boats. The damage doesn't look very bad to me. A bit of keel chattering and a torsion crack. It looks very well built. I doubt it's taking on any water through those. If left the armature aka the reo bar will grow and make it worse but tackled know the repairs will last year's. . Knock any loose cement out clean it up with a wire brush mix up a two to one mix of cement rub a smear coat of cement on the repair so it bonds fill it with the cement. Fair it with a wooden trowel wood doesn't suck the water out the cement. Always start repairs from the bottom up or the water in the cement will come out of the leading edge. A bit like standing in the shower with your arms out the water hangs along the bottom edge of your arms. When fair get a damp sponge and gently rub the wet cement it stands up on its end. When it's started to set get a garden sprinkler to keep it damp as it dries or it may crack as it goes off. Some people may lightly paint the reo with a rust inhibitor before the repair but it's not critical they let these boats rust a bit before they plaster as the cement won't stick to clean reo. When dry sand with a stone or paper and paint.They are a very forgiving user friendly boat.

[samfreeland]

Any repair on concrete get a heat gun and make sure the cement is nice and dry before you repair. As for the torsion crack I would get the heat gun on it and paint it with a two pot aquapoxy. The cracks don't go all the way through the boat only about two mm down to the reo bar.

[Steve Bean]

Joining new plaster to old should be done wet. Quoting from Colin Brookes' book "Ferrocement Boats:" Page 124. "To join new plaster to old keep the edges wet with water and using a brush paint regularly with your bonding agent (PVA) right up to just before applying the new mix to it, so that it joins in conjunction with the wet agent. On small jobs I also add bonding agent to the plaster mix."
If I'm looking at the same pictures of the OP boat I can't believe the damage is only "2mm" deep. Some of the damage looks to me like failed previous repairs. I think it needs a substantial amount of damaged cement and steel replaced. Absolutely repairable.

[samfreeland]

I agree . I would still dry it out before hand though.especially if you are using epoxy around the edge of the piece to be repaired or using a rust retarder like blackguard on the reo bar. I like to have every thing dry and clean before I start. I've tried epoxy around the edge of the break and a wet mixture of straight cement and water both worked well. I've also used just the two too one mix on its own and you would wet the edges when you start the job. On the tortion cracks he could use the thin edge of a grinder blade to follow the crack about a millimeter deep and fill it. These look like pretty minor repairs on this boat . Although as one chap mentioned you have to chase them back to good reo bar and chicken wire to splice in to if the damage is that bad. Admittedly some ferro boats are good some are bad depending on the builder's experience. I have never built one but have done the labouring work on a few for someone who did build. and repair for insurance company's. But I agree once itd nice and dry slash the dry cement with water before you start. On a side note as another poster pointed out a lot of these old boats have had diesel spilt in the bilge and as you heat it right up the diesel burns off nothing will stick otherwise.

[samfreeland]

An interesting phenomenon apparently caused by quilting when doing the wire ties. Instead of doing a star pattern they do small squares. And it shows through the concrete and paint. Why ? I have no idea. But it does seem to work like an xray. I have seen it on repairs where the rest of the boat looks fine except the repair it's self.

[StumpLifter]

Here is what I've been told by my brother who use to build ferro-cement hulls for a living in San Diego- once the steel armature is built the cement MUST be applied all in one continuous operation to prevent "cold joints". Because cold joints will allow water to intrude and attack the steel armature. Once attacked the steel armature will rust and swell destroying the surrounding concrete. Then - you sink. To his recollection - some boats constructed without regard to this principle lasted as long as 5 years before catastrophic hull failure took them to the bottom. A repair by it's very nature is a "cold joint". In my opinion this boat is beyond salvage.

[captlloyd]

Originally Posted by StumpLifter

Here is what I've been told by my brother who use to build ferro-cement hulls for a living in San Diego- once the steel armature is built the cement MUST be applied all in one continuous operation to prevent "cold joints". Because cold joints will allow water to intrude and attack the steel armature. Once attacked the steel armature will rust and swell destroying the surrounding concrete. Then - you sink. To his recollection - some boats constructed without regard to this principle lasted as long as 5 years before catastrophic hull failure took them to the bottom. A repair by it's very nature is a "cold joint". In my opinion this boat is beyond salvage.

Have to disagree, ferro- cement boats can be repaired just like fiberglass boats can be repaired. Ferro can last many, many decades.

[Snowpetrel]

Yes the modern epoxy grouts make a big difference to the secondary bonds.

[clockwork orange]

Originally Posted by StumpLifter

Here is what I've been told by my brother who use to build ferro-cement hulls for a living in San Diego- once the steel armature is built the cement MUST be applied all in one continuous operation to prevent "cold joints". Because cold joints will allow water to intrude and attack the steel armature. Once attacked the steel armature will rust and swell destroying the surrounding concrete. Then - you sink. To his recollection - some boats constructed without regard to this principle lasted as long as 5 years before catastrophic hull failure took them to the bottom. A repair by it's very nature is a "cold joint". In my opinion this boat is beyond salvage.

Back in the day there were proponents of the one shot method, such as your brother and there were proponents of the two shot method as originated by Ev Sayer in New Zealand. Its really no different than in the fiberglass world where there are those who insist that solid glass is superior to cored construction and visa versa. The 2 shot method is as well proven in the ferro world as cored construction in the fiberglass world.

[DumnMad]

Originally Posted by StumpLifter

Here is what I've been told by my brother who use to build ferro-cement hulls for a living in San Diego- once the steel armature is built the cement MUST be applied all in one continuous operation to prevent "cold joints". Because cold joints will allow water to intrude and attack the steel armature. Once attacked the steel armature will rust and swell destroying the surrounding concrete. Then - you sink. To his recollection - some boats constructed without regard to this principle lasted as long as 5 years before catastrophic hull failure took them to the bottom. A repair by it's very nature is a "cold joint". In my opinion this boat is beyond salvage.

I think this is boat looks well built but has hit something. We hit a container and received similar crack but no rust after 2 years. Did an epoxy repair on it before we crossed the Tasman and no sign of the repair after hauling 3 years later.
Ferro is the best!
Friends boat got dragged by another boat during a storm and got pounded on the beach. When hauled a year later it had minor non rusty cracks. Repaired with epoxy paint
Ferro is the best, just labour intensive and too expensive these days..

[chris95040]

Originally Posted by clockwork orange

Its really no different than in the fiberglass world where there are those who insist that solid glass is superior to cored construction and visa versa.

How are cold joints in ferro and cored construction in fiberglass analogous?