Another way to design & build in Aluminium boats

Discussion in 'Metal Boat Building' started by monomad, May 17, 2014.

  1. rustybarge
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    rustybarge Cheetah 25' Powercat.

    Steel is a wonderful material, anywhere in the world you'll get somebody to fix it. Of course it can get complex with heat treated tempered metals and stuff like special welding techniques, but it is rarely relevant to boats; but it's heavy!

    I've built a small sailing dinghy in ply/epoxy; the finish is not very strong and it doesn't take much to crack the surface and let water penetrate the ply. And as for its resale value, zero.

    I now know that I don't know a lot about alloy; better than before, but 'little knowledge' is dangerous as they say! One for the pro's.......

    That leaves GRP as a lightweight build material...yuck! All that horrid guey stuff.
    Although at the moment there seems to be a move towards flat panel construction in foam sandwich or balsa sandwich...which opens another can of worms.

    Of course if you are building a small boat none of these things bother you!


    PS: forgot about strip plank construction. Anyone got any experience?
     
  2. TANSL
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    TANSL Senior Member

    When a boat builder started its first aluminum boat, probably did not know much about this stuff, but was surrounded, he got advice from people who really knew and now he builts quality aluminum boats.
    If you believe that aluminum is the material that your boat needs, learn to work with it, do not limit yourself.
    I do not want to simplify the subject, aluminum work is not easy, just say, almost everyone here, have learned to do things we did not know before and many of us have bought and continue to buy, what we are not able to do, calculate,....
     
  3. Webbey64
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    Webbey64 New Member

    Thanks Manomad,
    Ideally i want something that is safe and smooth riding in the sea. The boat in the youtube link i posted would be exactly the hull i am after just in 6m not 7 with a nice cuddy cab. Just having a hard time finding that hull design the guy in that youtube vid lives in my neighbourhood im just trying to track him down.
     
  4. monomad
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    monomad Junior Member

    The 5.8m fishing boat that I posted earlier, here are two more photos showing you someone the framework and the size ofthe kill tank. There are 4 x 20 litre plastic buckets in the kill tank.
     

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  5. monomad
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    monomad Junior Member

    Kevin Morin
    Here is the bottom of that aerated hull.
     

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  6. Ad Hoc
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    Ad Hoc Naval Architect

    :eek::eek::eek: Looks like a fatigue crack just waiting to propagate!!
     
  7. monomad
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    monomad Junior Member

    Ad Hoc
    I gather you have no idea how it was built.
    It's not built the way you would build a standard aluminium boat and there is not as much work in it as you might think.
     
  8. Ad Hoc
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    Ad Hoc Naval Architect

    monomad

    I don't need to know how it was built. Reason is that there are endless sharp discontinuities and recesses in the plate and the chine/rubbing strakes have sharp "cuts" or "notches" etc. It looks very beautifully done, but it shall be prone to fatigue cracking. The high SCF factors even if the welding is 100% will reduce the life of the structure. It is simple geometry and load paths.
     
  9. monomad
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    monomad Junior Member

    Ad Hoc
    You mentioned, Plate, there is on plate in the bottom of this hull.
     
  10. Ad Hoc
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    Ad Hoc Naval Architect

    I assumed you meant to type "no plate" not "on plate (sic)".

    Well, whatever YOU are calling the structure that keeps the water out between the chines. It is riddled with stress concentrations....not ideal bedfellows in aluminium, regardless how it is put together.
     
  11. monomad
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    monomad Junior Member

    Ad Hoc
    There are ways around problems when one designs and builds in aluminium.
    We did a lot of on the water testing and there where no signs of cracking.
     
  12. yofish

    yofish Previous Member

    monomad, you seem to be a punching bag here at times with your unique ideas and derived methods thereof. I'd really like to know more about the last hull you showed with phantasmagorical bottom. Are those louvers vented or static? Is air injected into the slotted strakes? You really must give more! So many questions. Ad Hoc has a ardhon about stress risers but who cares if the concept proves? Design and material selection could obviate that.
     
  13. Kevin Morin
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    Kevin Morin Junior Member

    WOW boat bottom!

    monomad,
    I think there may be more mystery in your photo than resolution? I think I see two types of 'steps' one deeper and every other one shallower, and it appears that the wider/deeper ones are vented outside the chine angle along the topsides?

    But then, I can't tell and I did spend more than a few minutes with the largest blow up my system would give, and when the image became pixelated to distortion I still had countless questions.

    I will say its the most interesting build I've seen regarding the concept of drag reduction by ventilation.

    Of course if you're not going to bucket-list build her again, in a new updated version; anyone whose built a few welded aluminum boats would be seriously interested in seeing the design's 'secrets' of construction.

    Not being clear on the surfaces' relative spacial arrangements I can see a couple of ways to approximate what I think I see. But some of those are, in fact, prone to built-in problems. One I think might work to avoid notches is to have an inner hull with this complex skin 'outside' so the integrity of the bottom is not dependent on the many openings resilience.

    But I do confess this is harder on my thinking than a wooden block puzzle that requires key slides taken while the entire block is held at some obscure angle to unlock the puzzle.

    It's fortunate for you; that you are the entire length of the Pacific away from me finding your house or you'd be forced to tell me to get and quit nagging.

    IF this is the hull you sent to the scrappers (?) then you're a harder man than I. I'd have kept it just to look at the work. She's a milestone, regardless if she worked like you wanted, she tells more about your ideas than not- and she'd still be in my back yard.

    Cheers,
    Kevin Morin
    Kenai, Ak
     
  14. TANSL
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    TANSL Senior Member

    I'm not sure what they want to achieve with this bottom but I wonder the effect it can have that configuration in the front half of the hull.
     

  15. monomad
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    monomad Junior Member

    Yofish I don't mind been a punching bag. One has to think out side the circle at times otherwise things don't change. There is no air injected under the hull.
    Kevin Morin I can't give to much away on my hull design as I would like to build the new version. Yes it is the hull I sent to the scrapyard.
    Tansl if one is to reduce the drag on a hull then one has to aerat the hole hull.
     
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