Curved beam?

Discussion in 'Fiberglass and Composite Boat Building' started by andysailor, Jan 10, 2018.

  1. andysailor
    Joined: May 2017
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    andysailor Junior Member

    Sorry, I can be bad at describing what I'm looking for and miss out on some things.

    The curve is in towards the aka. Well, I could do a straight beam from the hull to aka as well, but won't get as big trampoline then and it would look better with the curved one. One option for the attachment points is to have the beam resting on hull deck and on aka deck. It could be built as one huge beam, or two separate ones.
     
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  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Someone here must be capable of doing a wave load calculation. Some assumptions would be needed, like design wave height over the 3.5 m width beam. Beam height over water, for reference only. I'm not capable, but that loading calculation seems to be the largest likely load. Then, some assumptions would be possible in the x direction as well based upon the wave hitting the structure I suppose.

    I guess I still don't see the reason for the curve based on your drawings, unless aesthetics for the drone/crows nest? Take your picture and convert it to a paint picture and reupload it with a hand drawn line of what you want to do. It'll take you like 3 minutes. Sounds like paid work for a few of these guys, maybe you need to make an offer?
     
  3. andysailor
    Joined: May 2017
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    andysailor Junior Member

    Here is a pic of a trimaran with similar beam and trampoline we are looking to achieve[​IMG]
     
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  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    I'm sorry but that configuration is different from the one you are proposing. In yours (green cross beam), the efforts that act on the new beam are greater than in the photography.
     
  5. andysailor
    Joined: May 2017
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    andysailor Junior Member

    Sorry, but then I think you have misunderstood me

    To clarify...in my first pic I had drawn a couple of lines (this was like I said an old sketch with different kind of options, but only option #2 is the way to go. The last pic of the tri with the beam is more or less exactly how I want it. Hope it made it a lot clearer :)
     
  6. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    It is possible that I have misinterpreted you but the "green beam option 1" of your scheme is supported by the aka while in the last photo that you have shown in the new beam it is based on the original aft cross bean of the ship. These two solutions are totally different and, of course, I understand that you prefer the solution of the photo to what you drew.:)
     
  7. andysailor
    Joined: May 2017
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    andysailor Junior Member

    Well...

    It's only option #2 I have mentioned, the blue line, and that one is connected to aka. Option #1 is connected to ama. I want to connect aka and hull, just like the photo of the tri with the beam
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    You will need to detail the aka construction specifically for any engineer Andy. You gave a few snippets of ply, foam, glass, but not enough. I am not your guy, but I know enough about building to know the aka attachment is critical. The aka has some moment calculation somewhere, but it didn’t include a bearing point. You might need to make a base that spreads the load out wider than the new beam size?

    And I see why you want it done that way; very nice looking and level. Makes complete sense now.
     
  9. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    That picture looks like the dinghy and a couple passengers is the loading. Do waves crash over the akas where you run? Are you hanging a dinghy on it, too?
     

  10. andysailor
    Joined: May 2017
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    Location: Sweden

    andysailor Junior Member

    The aka is very stiff and strong. Inside the aka (the aft part of it) is a cross beam box, built out of wood and plywood. If it's going to be level with the aka (attach in the aft part of aka)then, I'm not sure how because it will affect the box beam. If I attach it by having it resting on the deck of the aka, I guess it's an easier way to go.

    I have not planned to hang a dinghy there, and waves shouldn't crash to often, but want it to handle it if in rough weather. Would be pretty good if I could hang some solar panels pointing aft.
     
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