I'm going to build my first boat(section)

Discussion in 'Boat Design' started by Lemans, Nov 5, 2012.

  1. Dave T
    Joined: Sep 2011
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    Location: Anamosa Iowa and North Buena Vista on the Mississi

    Dave T Senior Member

    I hope you actually do build this boat, it will be interesting to see if any of your ideas work and what problems you encounter. I knew very little about boat building when I built my boat but it worked out real well. With help from people on this forum and common sense you can accomplish a lot. Don't forget the golden rule of engineering which simply states [If there's any doubt build hell for stout]. Have you actually started construction on any of the sections yet? I wish you the best of luck and hope this thing actually does get built.

    Best of luck with your project.
    Keep us informed.

    Dave T
     
  2. Lemans
    Joined: Nov 2011
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    Lemans Lemans

    The Ferro in my ferro-cement test-panel.

    I plan to plaster a 1m² ferro-cement test-panel. I added a drawing and info of the 'ferro' material I'm going to use.
    A panel of one by one meter holds 4 layers thin 1mm mesh and 1 layer concrete mesh 5mm.
    The iron in the panel has a weight of 6,73 kg and represent a volume of 0,868 liter. The iron costs 10 to 15€/m² - prise vary on quantity and suplier (EU)
     

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  3. groper
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    groper Senior Member

    You do realize that a concrete bow as a counter weight to a heavy stern engine will create a very long radius of gyration and thus poor seakeeping motions? It will pitch more and be more uncomfortable in a seaway... you should keep as much weight AWAY from the ends of the boat, and more concentrated amidships for better motion response...
     
  4. Lemans
    Joined: Nov 2011
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    Lemans Lemans

    Dave T,

    It's nice to show interest and it's encouraging to hear that others have accomplished the building of their vessel with not that mush (or non) experience in boat building.
    I will definitely start building this boat, that's for sure. Time and work-space is available.
    I also will do my best to document this in detail so others can avoid my mistakes or pick up some idea's as the look promising. If in the future, the boat is doing well , this thread is all what you need to build one for your personal use.


    seadreamer6

    I think it's healthy to accept failure as possible outcome. Learning how not to do it is also a valuable lesson. However, with good preparation and common sense, I like to do it right from the start.

    “The greatest inventions in history were made by people that didn't know any better..”
    Never heard this before....it's a good one!
     
  5. Lemans
    Joined: Nov 2011
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    Lemans Lemans

    Groper,

    Your reply points out possible handling issues witch are new to me.
    How important are they? This boat will be used on rivers and canals.
    I like to understand why it would pitch more - if creates a high polar center of inertia – witch makes turning more difficult – but for the same reason it should pitch less too– I'm missing something but don't see what.
     
  6. Dave T
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    Dave T Senior Member

    Lemans

    I looked up ferrocement boats and it looks like a reasonable way to go, it looks like the hardest part is making sure air is completely removed from the structure to avoid rust and deterioration of the steel reinforcement. Have you worked with this method previously? I wonder if there is anyone else on this forum who has worked with ferrocement construction. I wonder how the strength and weight compares to marine plywood. If the hull is penetrated a steel, aluminum, or concrete boat will sink if not either foam filled or divided into water tight compartments a wood boat will float because the material will displace more water than its weight at least until it becomes water logged. For my boat I used all wood with some steel reinforcement filled the hulls and deck with closed cell sheet foam and four water tight compartments in the bows. It looks like your compartment type of structure would probably accomplish this and it seems most peoples concerns are the joining the different material sections together. I'm sure this can be worked out so good luck with your project only time will tell if its practical but you will never know unless you build it.

    Good Luck! :)

    Dave T
     
  7. beernd
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    beernd Junior Member

    I struggle with the idea of making the front end and the rear end of the boat in ferro cement, and the middle segment in a lightweight composite material.

    I just don't see how it could work.
    Building the mid section out of ferro cement and adding a light weight front and rear section, would make more sense to me.

    This said, I am a first time boatbuilder, who seriously adapted the original design, so I should be the last one to critisize, ;) and that is what I don't want to do.

    Just asking out of curiosity. :cool:

    Keep us posted
     
  8. michael pierzga
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    michael pierzga Senior Member

    On the practical side, ferro cement structures don't like to be bruised. bounce off the dock, Fracture the cement and the steel is vulnerable.

    A boat that will be manhandled would be better off naked alloy plate. Alloy is almost indestructible and a common choice for rugged work boats
     
  9. seadreamer6
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    seadreamer6 Junior Member

    After reading a bit on ferro cement I have a couple of thoughts for you. What michael said is a big concern. I've worked a lot with steel reinforced concrete in non marine situations. It is an extremely brittle substance. It doesn't take much of a bump to crack it. Once a crack develops it's nearly impossible to keep water from seeping in and destroying the steel. The combination of water and lime can eat away the steel in short order. Once the steel is gone most of the strength is gone.

    Also, if the concrete is subject to freezing temps any moisture in the concrete will expand and little fractures will develop.

    I'm also wondering about having all that weight on the ends of your boat. You will need a very robust structure to join them together. Kinda like having 2 fat guys on the end of a 10m teeter toder. I'm not an engineer but i bet the forces trying to tear the boat apart will be huge.

    Here is a thought. How about building the center section out of concrete instead of the bow and stern?
     
  10. seadreamer6
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    seadreamer6 Junior Member

    oops...I forgot one thing.

    You mentioned using wood to join the concrete sections. In a moist environment you should never put raw wood in direct contact with concrete. The moisture causes a reaction between the wood and concrete which rots the wood very quickly. I'm sorry I don't the scientific reason it happens, I just know it does.
     
  11. Lemans
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    Lemans Lemans

    Hi all,

    I completed my calculation on volume and total weight of the ferro-cement bow....…....slik...... that's dutch......
    The iron has a volume of just over 10 liter – meaning 78 kg ( 172 lbs)
    The cement has a total volume of 186 liters – nearly 400 kg ( 882 lbs) Total 478 kg.
    Although the cost of material is very attractive ; (10-15€/m² ) I'm less sure about using it.

    With all the advice and warnings I already received...well, polyester was the second choice for the bow. Let's see where that material takes us.
     
  12. michael pierzga
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    michael pierzga Senior Member

    The advantage of ferro is that its cheap and cheerful. Perhaps modern paint coatings can ruggedize it .

    I still like alloy. The material is not prohibitively expensive but unfortunately the tools to work with it are.

    Life just ain't fair !!!!!!!!!!!!!
     
  13. Lemans
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    Lemans Lemans

    I can't get the the ferro-cement idea out of my head - this is crossing my mind.

    To bring the weight down, I must bring the volume of ferro-cement down to a minimum.
    When I build only the difficult 3D shaped under-section witch goes up to 15 cm above the waterline it's possible to add a 2D shaped upper-section build out of panels.
    This could be wood, metal or polyester/epoxy based composite.
    As in my case I like the BBQ and the 'outdoor' kitchen to be installed under the hood, I probably will go for a metal upper section.
    I have ad other goals to the build...it must be doable to build the 10,5m x 3m boat in a 6m x2,5m garage and the elements must be transportable by a 'deregulated' EU trailer. (overall weight <750kg)
     

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  14. Steve W
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    Steve W Senior Member

    Dave T, i have actually built a 40ft ferro boat by myself and been involved in the construction of several others back in the early 70s. No its not comparable in weight to plywood at all,strength is not an issue at all, usually in discussions of any boatbuilding material or method there will be those who will claim its the strongest thing on the planet and others will claim its not as strong as......,truth is strong enough is all you need and any adequatly built ferro boat is strong enough, it lends itself best to medium to heavy displacement designs, plywood on the other hand lends itself to very light thru medium displacement, i love plywood. Oh, and ferro allows for building exquisite shapes relativly easily.

    Steve.
     

  15. Dave T
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    Dave T Senior Member

    Steve

    It's good to hear from someone who has actual experience with this type of construction. Is your boat still being used and did you have any issues with the problems that others on this site have mentioned. I can see that this type of construction would probably not be practical for a small boat because of the weight and other issues.

    Lemans

    I don't know if your idea of making the bow section with the bottom ferro and sides with panels would work. You would have to have a framework of some type to attach the panels to and I would be concerned with the expansion and contraction of the different materials. Your idea of building a boat in sections should work and has several advantages. You don't need near as much space for construction, the sections would be much easier to transport and it could be assembled at the place it would be launched. I would be surprised if this hasn't been done.

    Good luck and keep trying.

    Dave T :)
     
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