USCG Stability Test for Power Trimaran

Discussion in 'Stability' started by mike w. schultz, Feb 10, 2020.

  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I like everything, but it looks like the front will slam coming down in any heavy stuff. Time will tell and the fix is easy. And I could be wrong as it is hard to see exactly what you have at that hard chine for'd. It just looks like a hard horizonta step, but maybe it isn't even done there yet?

    curious about why it was done in that fashion, was it just to get some wider foredeck?

    I am building a wet bag catamaran. So kinda fun to see yours.
    5AF9EAFB-5B25-4A4C-A277-DA27F0655C49.jpeg
     
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  2. mike w. schultz
    Joined: Dec 2018
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    Location: South Mississippi

    mike w. schultz Junior Member

    I filled the ama with water calculated the gallons and converted it to buoyancy.
    The foredeck "hard chime" was part of the build this is where the mainhull (which came out of a mold) meets with the side (built on table) join together on a knuckle that was generated from the mold, thoughts were that this 4" with "hard chime" would reduce the possibility of the hull getting stuffed. In the event that it creates slamming that is deemed undesirable it is easily fared out with fumed silica and resin and made slick smooth in 2 days. A lot of the construction ideas were deployed on Jon Coats last Build "Valhalla" a 70' power cat that currently in in charter in Jamaica renamed Loose Cannon, the boat can be located on YOUTUBE/Loose Cannon tours. In regard to your build, I assume you are building in BARBADOS, must be a night mare to source materials!!!!!
     
  3. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    You should deduct the weight of the ama, have you taken it into account?
     
  4. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    I watched the videos.
    Party central.
    My only concern is crowd control.
    It's going to be rather tender in it's initial stability
    which means it's going to easily roll when "12" people start moving toward one side.
    It doesn't look like this is likely to happen, but it easily could (whale sighting).
    Yes, it will have good roll resistance once a fair heel is on,
    but that's going to be a scary event for passengers.

    So what mold did the Valka come from, custom?
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    E9AD9836-E006-4D59-A34D-2EA373EA7F46.jpeg Hey Mike-Thanks for explaining the knuckle. I think I would have made that more of a 45 or a reverse curve the way Malcolm Tennant does. That way you can't bury or slam, but I am mostly just a boat lover Mike.

    Hope my boat doesn't hog in! I just have knife shaped bows. No knuckle or any way to stop burying it other than the operator..

    My build is in Minnesota. Quite a bit smaller demountable 10m powercat. Gonna run 90hpx2.
     
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  6. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    How much buoyancy did you calculate for each ama Mike, and at what draft?
    I am just asking questions from warm Barbados - Fallguy is building his amazing Woods Skoota cat up in the high latitudes.

    Please do post some more photos - a photo of the engine well especially would be nice, and down below in the main hull.
     
  7. mike w. schultz
    Joined: Dec 2018
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    Location: South Mississippi

    mike w. schultz Junior Member

    Custom made Valhalla mold,
     
  8. mike w. schultz
    Joined: Dec 2018
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    Location: South Mississippi

    mike w. schultz Junior Member

    Minnesota? I spent 6 months working at "Valley Fair" and Apple Valley Zoo those people know how to drink!!! Your boat will be a 10 once the snow melts off, take it down the Mississippi River, You can dock at my house, you do know how to use a grinder right? What brand of O/B? is she a planning hull?
     
  9. mike w. schultz
    Joined: Dec 2018
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    Location: South Mississippi

    mike w. schultz Junior Member

    No photos of motor well, guess it is a dark area that one cannot acquire a decent photo, finished the 2 other half(s) of the transom today, will pour transom in AM, working on final floor panels/sole, included photo looking forward into the main hull to the bow, numerous bulkheads and storage below floor, one will be freshwater, other diesel for Genset. Photo of hull thickness as well, will try to get photos of motor well shortly. interior.jpeg bow forward.jpeg
     
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  10. mike w. schultz
    Joined: Dec 2018
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    Location: South Mississippi

    mike w. schultz Junior Member

    Was difficult to get final weight on the ama as it still has not been fully reinforced from the inside, so total boat weight was calculated to estimate displacement/buoyancy of said ama...
     
  11. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Thanks.

    You're not concerned about initial stability being tender with all those people aboard?
     
  12. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    What was your calculated displacement / buoyancy of said ama (I presume at 10" draft)?

    I would also be worried about initial stability - these amas do not look like they will provide much buoyancy to resist any heeling force (eg from people walking out on them). She could be rather 'tippy' initially until she 'stiffens up'.
     
  13. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    maybe an 8; thanks

    I am about 5 miles from the Apple Valley Zoo.

    semi-planing or semi-displacement

    vmax 90 each side

    I run 40 grit on my Festool. Never grind much.
     
  14. fallguy
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    fallguy Senior Member

    can you explain the rationale and reasoning here?

    this is gonna sound silly, but couldn't you load water ballast to deal with the issue

    and how is it an issue for certain? Is it an ama displacement to main hull ratio?

    <removed>
     
    Last edited: Feb 14, 2020

  15. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Give Mike a little more credit.
    He built this boat, I strongly suspect he knows what I'm talking about.
    I'd like to give him the benefit of the doubt.
    I'm building my 3'rd boat of very similar design and was trying to be helpful.
     
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