Best way to turn 19m cold molded epoxy boat

Discussion in 'Wooden Boat Building and Restoration' started by Ambitious, Jan 11, 2009.

  1. Ambitious
    Joined: Jan 2009
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    Location: Serbia, Belgrade

    Ambitious Naval Architect

    Hello to all. I am Naval Architect working in little company based in Belgrade, Serbia. Currently, we are working at 19m mahogany cold molded powerboat. It will be a waterjet power boat with triple engine installation (3x800hp). As we all know the easiest way to build a hull is to build it upside down. These days we are about to turn the hull and start with system installation. I am not sure about the best way to do the turning. At this moment I am thinking about two cranes (one at port and the other at starboard) as a solution. My idea is to do the turning together with steel construction which is support for hull. Hull is about 6 tonnes weight and steel construction is about 2.5 tonnes. Any ideas? Suggestions? If someone have some pictures? Thanks
     

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  2. Ambitious
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    Ambitious Naval Architect

    Something like this
     

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  3. apex1

    apex1 Guest

  4. Ambitious
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    Ambitious Naval Architect

    Thanks for reply, but this a little different way. I must get the whole construction up and then do the turning in the air. I must watch for shear and chine to stay undamaged.
     
  5. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    We have lifted and turned the 44ft steel hull from the structure uprights only with 6 chainblocks of 3 tons capacity each.
    The roof trusses/beams could not be used as the were of a very flimsy construction. The hull was lifted and turned and halfway over, then lowered on tires to re-adjust the chainblocks for the final half turn.

    Your setup looks very similar to what we had and if you like, I can send you a complete range of photos of how the chain blocks were attached etc and a sketch of the setup.
     
  6. apex1

    apex1 Guest

    Ahhh.............

    So look here:

    http://www.mp-marine.com/photos1.html

    And I am sure Wynand knows much more than I do, I never turned a hull.
    Send him a PM!

    edited:
    ooops.......hello Wynand.........:) hope you did´nt mind that I referred to your knowledge?:rolleyes:

    And btw:
    As we all know the easiest way to build a hull is to build it upside down.

    I disagree.................
    Here in Istanbul, Turkey (where I am at present) are about 200 to 250 Yards and boatshops doing Wood Epoxy jobs they ALL, ALL..... build right side up! Some of them like "Vicem" are very, very experienced and know how to save a penny. So I am sure it is more a sort of personal preference rather than common sense how you do it.
    Metal is a bit different, of course.

    Regards
    Richard
     
  7. Ambitious
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    Ambitious Naval Architect

    For Apex1: I am hard to imagine how to do a vacuum bag of final layer of veneer if the boat isn`t upside down. It is possible but much more harder to do.

    Btw thanks for link it is very useful.
     
  8. Ambitious
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    Ambitious Naval Architect

    Dear Wynand,

    I would really appreciate if you could send me some photos.
     
  9. apex1

    apex1 Guest

    I´m sure it´ is close to impossible.;)
    Nobody does here. The final layer is just the last one to be layed and all of them have to be layed very, very exact and grind down then. Workforce is not the issue here, so if one cannot manage the job himself, well .. employ some "one armed monkey´s" to assist. By far not all of them end up with acceptable results, but say 30% or so are as good as the best elsewhere.

    I would not argue with your way, just point out that it is´nt a written law!;)
    And you´re welcome:D for most of the forum members it´s a pleasure to assist, naturally. You know the game is give and take.
    Regards
    Richard
     
  10. Ambitious
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    Ambitious Naval Architect

    I would like to show you couple of photos of our first boat so you can see what kind of surface quality we want to achieve.
     
  11. Ambitious
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    Ambitious Naval Architect

    Here they are. The pictures were taken at Croatia coast and at river Sava in Serbia
     

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  12. Ambitious
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    Ambitious Naval Architect

    One more
     

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  13. apex1

    apex1 Guest

    Nice..............:)

    Thats how it go´s.
    I have a little lobsterboat here under construction 28ft only.
    The boatshop applies 3 layers Epoxy and then 24 layers of varnish, all sanded down between the spray. Endless job

    Regards
    Richard
     
  14. Ambitious
    Joined: Jan 2009
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    Ambitious Naval Architect

    At our first boat, we had 4 layers of epoxy and then 15 layers of varnish. But the problem was that when the guys do sanding between layers of epoxy they don`t know how much epoxy is left. So after 4 layers of epoxy we had actually thickness of only one epoxy layer at some spots. At current project we try do do one layer and then wait couple of hours (depending of temperature) and then do the second layer "on wet". This way we get double thickness in one day. We already apply 6 layers, 3x2 layers in three days. Your opinion?

    Kind regards
     

  15. apex1

    apex1 Guest

    We apply all 3 layers on green! Bull.....:eek:

    We apply the following layers (after the first:idea: ) on the not cured...green... and do NOT sand the first two!!!! The first almost only saturates the wood, even the second is slightly more than filling the craters. If you apply the second coat too soon on WET you may stop the first to soak the material in deep. The third has, you know, to cure completely, than is more or less completely sanded down. The remaining coat is about the same thickness as a single layer on a hard surface, as steel, would have.
    The following first layer of varnish is NOT grind, that helps to prevent coming through to the beef again. Then you work down to the first time for a even surface (in varnish) then every spray is followed by a gentle sanding.

    qoute: This way we get double thickness in one day. We already apply 6 layers, 3x2 layers in three days.

    Imho more than 4 is overkill, less than that for skilled pro´s only. But more important is that you should apply all the Epoxy coating in one go!!! Which can easily make a 36 hrs day depending on temperature etc. But you save time cos you must not grind between layers and have a far stronger film layed. Try on small peace of scrap with three layers, works fine.
    Regards
    Richard
     
    Last edited by a moderator: Jan 13, 2009
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