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Old 18-04-2016, 13:01   #61
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Re: 21th Century Ferrocement Yacht Hull Technology

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The ones that were successful built a rebar and wire skeleton and hired someone to Gunite the cement on and a bunch of good masons to trowel the surface. A one shot deal so the cement all goes off at the same time. As I recall it has something to do with the crystalene properties of cement.
Basically cement doesn't have good adhesive qualities.
- If you cast it all at once, the water and cement chemically react creating a new material that is one solid piece..
- If you let the first part set then try to cast more concrete against it, you are left primarily with adhesion. Any place this happens it will try to come apart once you start applying loads.
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Old 18-04-2016, 15:12   #62
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Re: 21th Century Ferrocement Yacht Hull Technology

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Basically cement doesn't have good adhesive qualities.
- If you cast it all at once, the water and cement chemically react creating a new material that is one solid piece..
- If you let the first part set then try to cast more concrete against it, you are left primarily with adhesion. Any place this happens it will try to come apart once you start applying loads.
I believe I said all at one time. I saw a 65' Gunited and troweled I believe they labored form O dark thirty one morning to O dark thirty the next with a crew, of 5 or6, brought to SC from Fla. because they had the knowhow to do it correctly. A previous poster who apparently knew what he was talking about mentioned keeping it wet for 30 days. 30 days give a 90% something cure and apparently keeping it wet is the secret to a correct cure. I opted for GRP which turned out great. Long story short buy a boat.
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Old 18-04-2016, 22:50   #63
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Re: 21th Century Ferrocement Yacht Hull Technology

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I believe I said all at one time. I saw a 65' Gunited and troweled I believe they labored form O dark thirty one morning to O dark thirty the next with a crew, of 5 or6, brought to SC from Fla. because they had the knowhow to do it correctly. A previous poster who apparently knew what he was talking about mentioned keeping it wet for 30 days. 30 days give a 90% something cure and apparently keeping it wet is the secret to a correct cure. I opted for GRP which turned out great. Long story short buy a boat.
28 days is typically considered 100% strength. Technically, it can still gain strength but by that time any gains are negligible. Depending on the mix it could peak as early as 7 days.

Particularly for a thin casting like a hull, keeping it damp is critical. Concrete doesn't dry...it cures and that cure requires the correct proportion of water to cement. Too much leaves voids that weaken the cement but too little will leave uncured cement. This is complicated as the ideal mix would be very stiff and hard to work with. With pieces small enough to move, what is typically done is once the concrete sets (so you don't mess with the proportions) you cure by putting the piece in a misting room or submerging it in water. If the surface dries (no cures), it can shrink creating stress cracks.

GRP is far easier to work with for an armature and there are techniques if you do have to take a brake in the work...though it s still better to do the entire hull in on shot.
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Old 18-04-2016, 23:33   #64
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Re: 21th Century Ferrocement Yacht Hull Technology

I've seen and know of several FC commercial hulls. Some home built and a few built by no long in business yards. Most had the steel parts coated in epoxy. Some even in proper epoxy for steel. All now all are operating as unplanned anchors. Some still have their builders with them. How fast does a brick sink?
When salt water gets to the steel (and it will eventually get there) the steel will rust. Rusting steel expands. Putting cracks in the cement and making it easier for the salt water. At some time in the future you have a big hollow brick.
If you're determined to create a underwater archaeological site for some future generation, why not spend less money and buy one of the boats that can't get insurance. Sail that for awhile and deal with the maintenance of FC boats.
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Old 19-04-2016, 14:00   #65
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Re: 21th Century Ferrocement Yacht Hull Technology

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Hello there,

This is my first post to the Forum and I want to present my best. My name is Umut , an archaeologist from Istanbul and want to build myself a ferrocement danish double ender yacht to myself.
You cannot be serious!

If you are, this is, in my opinion, perhaps the worst idea since Hitler invaded Poland.

Paul
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Old 19-04-2016, 14:49   #66
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Re: 21th Century Ferrocement Yacht Hull Technology

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You cannot be serious!

If you are, this is, in my opinion, perhaps the worst idea since Hitler invaded Poland.

Paul
Is this as if you meant an archeologist from Istanbul cannot build a boat?

Then this is as as if you said that a painter from Casablanca could not sail around the world.

Which part exactly does not fit your coherent vision of the world: Istanbul, archeology or boat building?

Odd.

I do not get your apparent parallel.

b.
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Old 19-04-2016, 15:24   #67
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Re: 21th Century Ferrocement Yacht Hull Technology

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Originally Posted by barnakiel View Post
Is this as if you meant an archeologist from Istanbul cannot build a boat?

Then this is as as if you said that a painter from Casablanca could not sail around the world.

Which part exactly does not fit your coherent vision of the world: Istanbul, archeology or boat building?

Odd.

I do not get your apparent parallel.

b.
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Naysayers never accomplish anything of note.
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Old 19-04-2016, 15:32   #68
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Re: 21th Century Ferrocement Yacht Hull Technology

I can't see naysaying? From the OP I have no idea. Gluing precast together, have at it.

Not in my world, I hope it works for him.
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Old 19-04-2016, 15:35   #69
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Re: 21th Century Ferrocement Yacht Hull Technology

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If you are, this is, in my opinion, perhaps the worst idea since Hitler invaded Poland.
Seriously, guys, Hitler?!
Ridiculous comparison too, by the way, and insensitive too.

We're talking about boats, for Pete's sake. Would be so nice to just have a friendly topic

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Originally Posted by CdS2 Roland View Post
An other thing, in Europe no company are doing insurance for FC boats. It will probably be the same in other countries...
Either the Netherlands has been sneakily moving off and away from the European continent or this statement isn't very accurate
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Old 19-04-2016, 15:49   #70
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Re: 21th Century Ferrocement Yacht Hull Technology

One of my favourite ferro boats is Quais Quais. Home-built in the 70's left Vancouver 1980 and returned 2013. One leg from Durban to Nelson with no stops took 4 months at sea. I think they averaged around 3 knots. They were reported lost but turned up at Port Nelson one night a bit lean but otherwise fine.
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Old 19-04-2016, 16:22   #71
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Re: 21th Century Ferrocement Yacht Hull Technology

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Is this as if you meant an archeologist from Istanbul cannot build a boat?

b.
Oh, of course not. It has nothing to do with profession or nationality (but, my, how quick we are to jump...) but..

To build:
1) singlehandedly
2) a 38' boat
3) by an apparent novice sailor
4) with apparently no experience in boatbuilding
5) judging from his profession and brief description, similar to a Viking ship
6) out of ferrocement but wait, there's more!
7) panel construction, stuck together who knows how!

A proposition so ridiculous, so wasteful, so fruitless, it could only be rivalled by a government program.

And the hilarity continues: page after page of earnest commentary, thoughtful, knowing,..and no one to stand up and say to the original question, "Are you completely NUTS?"

Paul

(As for the Hitler reference, I knew it was touchy because of his overwhelming identification with Ultimate Evil, but I couldn't think of a worse idea than starting World War II and I was running out of time--lunch! Sorry.)
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Old 19-04-2016, 16:26   #72
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Re: 21th Century Ferrocement Yacht Hull Technology

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Originally Posted by Lizzy Belle View Post
Seriously, guys, Hitler?!
Ridiculous comparison too, by the way, and insensitive too.

We're talking about boats, for Pete's sake. Would be so nice to just have a friendly topic

Either the Netherlands has been sneakily moving off and away from the European continent or this statement isn't very accurate
I don't think he was making a reference to the evilness of Hitler Lizzy as much as the stupidity of Hitler's move on Poland. A bit insensitive I give you. But I don't think he meant it as such.
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Old 19-04-2016, 16:38   #73
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Re: 21th Century Ferrocement Yacht Hull Technology

To the OP

I'm all for FC boats. There are some true, tried and tested models still sailing the world after 40 years. Well after both wooden and glass boats have disintegrated away.

To build a boat, any boat, a boat that you can then sail the world on, requires some skill, a lot of knowledge and learning. As well as the finances and time to do it.

To build one out of concrete that will last is a particular skill, particular knowledge, particular learning. Do it right and you can have a boat that will last you decades. Do it wrong, like a lot of back yarders did in the 80's and you will end up with a boat only suitable as a play pen and at worst one that's sucked up all your savings.

To build an experimental concrete boat with the intention of sailing it as a future dream is not well conceived. 100% encouragement to you to build a small experimental and put it through some testing. I'd be very interested to hear of the results. But to build a larger experimental, with untested technologies, by a builder that I'm suspecting has no particular boat building skills or knowledge is just a big mistake.

Don't be suckered into being encouraged on here to go ahead if your in this second category. There are lots and lots of threads on CF that almost appear to be dedicated to laughing and knocking the fool hardy. Some deserved, plenty are not. Don't be one of those subjects.
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Old 19-04-2016, 16:40   #74
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Re: 21th Century Ferrocement Yacht Hull Technology

Quote:
Originally Posted by Paul J. Nolan View Post
Oh, of course not. It has nothing to do with profession or nationality (but, my, how quick we are to jump...) but..

To build:
1) singlehandedly
2) a 38' boat
3) by an apparent novice sailor
4) with apparently no experience in boatbuilding
5) judging from his profession and brief description, similar to a Viking ship
6) out of ferrocement but wait, there's more!
7) panel construction, stuck together who knows how!

A proposition so ridiculous, so wasteful, so fruitless, it could only be rivalled by a government program.

And the hilarity continues: page after page of earnest commentary, thoughtful, knowing,..and no one to stand up and say to the original question, "Are you completely NUTS?"

Paul
y.)
my thoughts too.
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Old 19-04-2016, 17:29   #75
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Re: 21th Century Ferrocement Yacht Hull Technology

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Originally Posted by Rustic Charm View Post
my thoughts too.
Ditto on that. I'm not sure a FC boat done right is that bad? Gluing panels together seems over the top. I hate to think of someone is entertaining such an idea.
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