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Old 15-04-2016, 18:08   #1
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21th Century Ferrocement Yacht Hull Technology

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.

I researched the concrete technologies for a very long time , even since DUCTAL from Lafarge invented.

Long story , short , the highest strenght concrete is reactive powder concrete.

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

That concrete invented for bunkers , military facilities etc. Least 15 times stronger than ordinary concrete for hull construction. I dont know it makes 15 times thinner or lighter hulls also , get an technical advise.

I thought I can make a double flexible plywood sided shape changing mold for casting hull panels out of that concrete without using any traditional hand lay mesh,net or bar.

japanese and Italian Engineers invested lots of time and Canadian scientists to cast clean and basic out of textile flexible molds.

Than I want to epoxy or silicone fill each panel to other.

I want to get your opinions on that subject.

I found ISTON RPC or PRC is manufactured in Istanbul and next week I will get a technical analysis document plus price quote about that concrete
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Old 15-04-2016, 18:59   #2
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Re: 21th Century Ferrocement Yacht Hull Technology

I suspect that leaving the ferro out of a ferrocement boat is a very bad idea. Cement can indeed be very hard. But you need steel to provide tensile strength. Otherwise I think your boat might shatter, possibly even under just ordinary loads of heavy weather. Please don't spend any money on this with consulting a bona fide expert.
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Old 15-04-2016, 19:08   #3
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Re: 21th Century Ferrocement Yacht Hull Technology

Welcome to CF, MtUmutSarac

I know nothing about ferrocement boats, so I'll leave that to those that do
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Old 15-04-2016, 19:17   #4
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Re: 21th Century Ferrocement Yacht Hull Technology

Back in the 70's in Canada these boats were all the rage, lots of big holes dug in back yards when builders figured out that the hull only represented 20% of the total costs. That said I have seen some excellent examples of this type of construction and a couple as fair as a glass boat but these were exceptions. There were many different designs in Canada and I'm sure you could find them on the Web. Had a cruising friend and family that sailed from Alaska to Mexico and return without any big issues in their FC boat. Hope you plan on keeping it for a long time as the market is very skinny for these boats and insurance is almost impossible to get but maybe Turkey is different, good luck. PS Turkey builds some amazing wood boats, you might want to look into these
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Old 15-04-2016, 19:48   #5
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Re: 21th Century Ferrocement Yacht Hull Technology

First let me say welcome to the forum.
I had never heard of Reactive Powder Concrete (RPC) so I had to look it up. Interesting stuff.

If I understand you correctly, you plan to cast hull panels from RPC and then glue them together to form a hull. I don't know if the hull panels would be strong enough, they might be, but I would be concerned with the glue joints between the panels.

I'm thinking it might be a good idea to build a concrete dinghy first as a proof of concept.

Caribbeachbum, he's not leaving the ferro out, it's part of the aggregate. Two to three percent of the concrete is short pieces of steel wire.
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Old 15-04-2016, 19:59   #6
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Re: 21th Century Ferrocement Yacht Hull Technology

Thank you all for welcoming me.

Reactive Concrete is totally different animal. If the ordinary concrete is 3000 strenght and when american bunker busters works for 10000 , steel is 100000 and reactive concrete is 60000 - 80000 strenght. I mean that concrete is tough as steel. But lots of university research stuff goes from 25000 to 40000.

Trick is to hot compress the concrete for 3 days for max strenght.

I still have no idea about price ? It must be very expensive for concrete budget.

Steel wires are very cheap here also and lot goes in rpc.

Let me wait others comment.

thanks
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Old 16-04-2016, 00:16   #7
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Re: 21th Century Ferrocement Yacht Hull Technology

While I haven't worked on ferrocement boats, I do have a concrete design background from many years ago.

The problem with concrete is it' great in compression but in design we assume essentially zero strength in tension. It's britle, so any small crack will propogate.That's where reinforcing comes in. It holds the concrete together when it cracks.

Discussion of military bunkers is completely unrelated as the design requirments are completely different.

You seem to imply that because it's 15 times stronger, you can make the hull 15 times thinner. ABSOLUTELY NOT. If you don't understand why, I strongly suggest getting a set of premade plans and don't experiment with what you think you can change.

I will reiterate 2 points from previous posters:
- The hull is typically only a small percentage of the cost and labor for a large cruising boat.
- Try it with a dingy first to learn.
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Old 16-04-2016, 01:49   #8
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Re: 21th Century Ferrocement Yacht Hull Technology

As the owner of a Samson 32-foot double ended ferrocement sailboat, I too urge you to do some experimenting with your proposed technology. Make some test panels and try to destroy them. The idea of gluing panels together sounds very risky.
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Old 16-04-2016, 02:39   #9
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Re: 21th Century Ferrocement Yacht Hull Technology

Thank you for your comments.

I know 15 times stronger does not make 15 times thinner but I still dont know how much does it go thinner , lighter and cheaper. But I know thickness is the one of the most important barrier.

Steel reinforcement could be still built in panel molds. Get some net or mesh , cut it , make several layers and close the mold and inject high pressure concrete in to mold.

Gluing is risky , I thought I can make thicker edge per panel and some holes and rivet the panels , glue them and thick fiberglass the joints .Additionally I can add a concrete frame and kiss with panels.

Making panels and trying to destroy them is the best idea.

I have another idea is to make test panels , carry to concrete lab and lab instrument test.

As far , I can think for now. Let me wait what others say .

I am talking about precast technology and adhesives are the things keep cars together when during an accident without welding .
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Old 16-04-2016, 03:24   #10
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Re: 21th Century Ferrocement Yacht Hull Technology

With traditional ferro construction, when done properly, the outside 1st then the inside are plastered continuously with no stoppages or construction joints. Often using quite a large team of plasterers. The main objective is to avoid joints and porosity. The compatibility of steel mesh and 2 to 1 sand-cement is the winning formula for success.

I would expect serious issues for Glue and/or silicone joints where the component properties such as coefficent of expansion and stress/strain curves are not so homogeneous.
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Old 16-04-2016, 05:28   #11
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Re: 21th Century Ferrocement Yacht Hull Technology

sounds ideal for houseboat or floating pontoon construction!

this sounds like a Turkish alternative to the "Flying Hawaiian"...............
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Old 16-04-2016, 09:14   #12
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Re: 21th Century Ferrocement Yacht Hull Technology

You mentioned thicker edges. I was thinking along the same lines. Thicker edges would give you more surface for adhesive and you might be able to incorporate mechanical fasteners as well. I'm a glue and screw kind of guy.
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Old 16-04-2016, 09:16   #13
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Re: 21th Century Ferrocement Yacht Hull Technology

What is your rationale for considering this? Is it cost? Its new technology in the yottie world as far as I know. I doubt you shall save any money over buying a second hand similar boat. I would have concerns about being the first to use this, and have concerns also over lengevity, insurance and importantly what happens when you come to sell? You could well be over capitalising. Owing a totally unique boat is not always good.
I would give some serious thought to staying a little more conventional.

Good luck, though, with whatever you decide.


Quote:
Originally Posted by MtUmutSarac View Post
Thank you for your comments.

I know 15 times stronger does not make 15 times thinner but I still dont know how much does it go thinner , lighter and cheaper. But I know thickness is the one of the most important barrier.

Steel reinforcement could be still built in panel molds. Get some net or mesh , cut it , make several layers and close the mold and inject high pressure concrete in to mold.

Gluing is risky , I thought I can make thicker edge per panel and some holes and rivet the panels , glue them and thick fiberglass the joints .Additionally I can add a concrete frame and kiss with panels.

Making panels and trying to destroy them is the best idea.

I have another idea is to make test panels , carry to concrete lab and lab instrument test.

As far , I can think for now. Let me wait what others say .

I am talking about precast technology and adhesives are the things keep cars together when during an accident without welding .
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Old 16-04-2016, 09:26   #14
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Re: 21th Century Ferrocement Yacht Hull Technology

Welcome to CF

Do you have any experience in vessel design or building? If so, what is that experience?

If you have none, nc just toying with the concept then I'd suggest you leave it alone. Building any boat, out of anything, let alone new technologies is a highly skilled knowledgable task.
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Old 16-04-2016, 09:41   #15
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Re: 21th Century Ferrocement Yacht Hull Technology

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.

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