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Old 16-04-2016, 11:50   #16
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Re: 21th Century Ferrocement Yacht Hull Technology

That concrete consists lots of materials inside plus steel wires. These wires are few milimeters long. It uses only very fine powder materials .

That sounds like a disaster. The problems with ferro have been rusting of wires that have become exposed from getting dinged. Placing small length steel wire in the concrete? I doubt it adds anything but problems no tensile strength. Pre casing panels?
JMHO
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Old 16-04-2016, 12:20   #17
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Re: 21th Century Ferrocement Yacht Hull Technology

Quote:
Originally Posted by expatri8 View Post
I am absolutely not a marine expert but I have one minor experience to share.

I constructed a small power (ducted air prop) craft intended for light sprints.
In order to try out a stronger hull around the propellers
(handcrafted and prone to exploding [=detonating at high rpm])
I fabricated a bqtn roving/mat fabric over grc panels (app 6mm thick)
[grc = glass reinforced concrete] I drilled holes through the panels to increase
solidarity, but that was not obviously necessary.

This construction was insanely strong and survived some very impressive impacts.

The nicest thing was the GRC panels we just bought at the local building supply.

Sign me up for another thread with lots of photos, sounds fascinating.
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Old 16-04-2016, 14:25   #18
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Re: 21th Century Ferrocement Yacht Hull Technology

And her name will be....

Maid of Crete?
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Old 16-04-2016, 15:02   #19
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Re: 21th Century Ferrocement Yacht Hull Technology

I think your idea sounds great and I think you should prototype now and destroy it.

Think of how small a practical prototype you can build. A boat of less than 20ft should not be too expensive to build. You may want to build something similar to local fishing boats, if they are double ended in your country. Something less than 500 kg of weight. Then sail it, find the weak points and any pitfalls. Then build the big ship, using the knowledge from the prototype to avoid BIG and costly mistakes.

When you talk of a material being strong - make sure the strength is of the type required in your design. Some materials have good tensile strength but poor shear strength, etc. You want the right type of strength in every particular part of the hull. Make sure you do know what the forces are and in what direction(-s) they are applied. Many parts of the hull ask for more than one type of strength.

I am not sure how much regular ferrocement boat techniques will be of help to you. It sounds like you are more into chopped glass mat / resin territory.

This will be a most interesting thread to read if you go ahead with your vision.

PS What are the weaknesses of the material as you know it?

Best of luck,
b.
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Old 16-04-2016, 15:07   #20
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Re: 21th Century Ferrocement Yacht Hull Technology

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Building any boat, out of anything........ is a highly skilled knowledgable task.

It's really not, you know. Much as some "professionals" would like to keep that myth alive.
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Old 16-04-2016, 15:27   #21
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Re: 21th Century Ferrocement Yacht Hull Technology

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It's really not, you know. Much as some "professionals" would like to keep that myth alive.
I would suggest someone is well read and has a lot of time and effort. This does not sound at all that way. I have seen some very nice ferro boats. One from South Africa I thought was glass while on the hill in SC. I hope they made it the rest if the way around the world.

I am sorry, this sounds like a pipe dream. Not meaning to be crass. I just hope the OP takes it as positive criticism.
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Old 16-04-2016, 15:39   #22
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Re: 21th Century Ferrocement Yacht Hull Technology

Yes, it's a lot of work and takes a lot of hours. No arguing that.
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Old 16-04-2016, 15:42   #23
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Re: 21th Century Ferrocement Yacht Hull Technology

I guess the question for the OP is, what do you hope to gain from using ferrocement over steel or fibreglass? If it's purely a cost benefit, forget it. The savings, considered over the whole cost, would be minimal.
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Old 16-04-2016, 16:16   #24
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Re: 21th Century Ferrocement Yacht Hull Technology

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It's really not, you know. Much as some "professionals" would like to keep that myth alive.
Really , seriously

In what material can you build a boat that does not require some real skill and expertise?

I know a lot of people in the 80's tried their hand at building out of concrete, and many were unsuccessful. The really good ones are still afloat today. I seen one last year I was convinced was steel, till the owner confessed it was ferro. Back in the early 90's there was a big fan fare and media circus around some guy who had built this massive yacht hull in his back yard. It had to travel quite a distance to the Derwent River, with police escorts, power lines being moved, to get to the River where crowds and media gathered as a crane positioned it in the water. Down it went, to an inch of the waters lapping the gunnels. I believe he donated it to a children's playground.
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Old 16-04-2016, 16:23   #25
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Re: 21th Century Ferrocement Yacht Hull Technology

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Originally Posted by Rustic Charm View Post
Really , seriously

In what material can you build a boat that does not require some real skill and expertise?
http://www.freewebs.com/origamiboats/

You're welcome.

Though I do like your steel boat.

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Old 16-04-2016, 16:38   #26
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Re: 21th Century Ferrocement Yacht Hull Technology

Quote:
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http://www.freewebs.com/origamiboats/

You're welcome.

Though I do like your steel boat.

goat
Well, even 'origami' steel boat requires skilful welding, and as my welding looks like bird ****, it's too complicated for me

Thank you Goaty on the compliment. I'm currently sitting at a visitors Marina in Melbourne and I've had a number of people comment on the pretty green boat

It's amazing the difference a nice new sandblast and paint job does
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Old 16-04-2016, 16:42   #27
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Re: 21th Century Ferrocement Yacht Hull Technology

Quote:
Originally Posted by Rustic Charm View Post
Really , seriously

In what material can you build a boat that does not require some real skill and expertise?

I know a lot of people in the 80's tried their hand at building out of concrete, and many were unsuccessful. The really good ones are still afloat today. I seen one last year I was convinced was steel, till the owner confessed it was ferro. Back in the early 90's there was a big fan fare and media circus around some guy who had built this massive yacht hull in his back yard. It had to travel quite a distance to the Derwent River, with police escorts, power lines being moved, to get to the River where crowds and media gathered as a crane positioned it in the water. Down it went, to an inch of the waters lapping the gunnels. I believe he donated it to a children's playground.
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.
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Old 16-04-2016, 16:49   #28
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Re: 21th Century Ferrocement Yacht Hull Technology

Mr B talk hits the nail on the head. The op talks about strength as xxx, but doesn't specify if it's Tensile, Shear or Compressive strength .
Use of short steel sections will leave potential weak in sheer zones where tons of water hitting the hull will split it in two. Unless the steel is bent or has barbs then Tensile strength will be reduced.
Not such a big problem in buildings but boats never
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Old 16-04-2016, 17:03   #29
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Re: 21th Century Ferrocement Yacht Hull Technology

Here is a simple explanation on what this is.

Reactive Powder Concrete

I recall a local company here trialing a new building with the steel fibres in the cement for 'road ways' which was an attempt to do away with the usual but expensive steel rio. Within a relatively short period of time the fibres became exposed and became unsightly as they began to rust and cause unsightly stains. I think they were replaced with composites for building.

In any case. Using this technology for a boat, even if it has benefits, would be expensive.
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Old 16-04-2016, 17:44   #30
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Re: 21th Century Ferrocement Yacht Hull Technology

We use steel fibre reinforcement for precast panels. Traditionally, bored tunnels used plan, unreinforced segments to line them - no corrosion etc. Steel fibre reinforcement means we get a lot thinner panels, thus lighter and still no risk of stray current corrosion because there is no continuity sufficient. The panels are tested and the operators trained (and retrained for each project typically),, the panels are destroyed in the testing, then thousands are produced. Getting the SFR evenly distributed and not clumped in some of the mix is part of the trick. The mouldings are all steam cured
The important aspect of these panels is that they form a curved surface working under compression. Concrete / cement etc are good under compression, steel reinforcement lets the concrete perform under tension.
So I appreciate the intent, but you will still need the frame and stringers to hold the panels together and you will not get the benefits of the mass production. It may not work, so I suggest you speak to experienced designers of these segments before any more progress
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