Hi everyone old question new twist

Discussion in 'Boat Design' started by todzippy, Feb 3, 2016.

  1. todzippy
    Joined: Jan 2016
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    Location: cornwall UK

    todzippy New Member

    Hi all firstly nice to be part of the forums and hope I find lots of good reading and tips on here.

    I have been buying old 70's 80's Yachts 20 - 26 foot and converting them into pleasure boats /weekend House boats for 8 years. Re-designing the internal cabin layouts and raised the roofs on 2 to give more head room.

    Now I have x2 24 foot Trident Yachts exactly the same and was wondering if it would be possible to connect some type of steel struts across the decks that I could reinforce to connect them together to make a Catamaran.

    Now before I get replies telling me this would be unsafe and the stress loads would not cope and would cause the hull to split down the side'

    This boat would not be used at sea only on a tidal estuary with a maximum spring tide depth of raising the boat from the bottom of the keel aprox 6 foot.

    The water state at worst in a storm is about 2 foot choppy.

    I was thinking that as the masts take such a force in winds and the weight of them , If i remove them and not use them then the deck should be still strong enough to take an equal force spanned across the topside with additional struts to the inside and additional timber heads around just before the gunnel's with struts inside projecting any stress onto the keels.

    The one obvious strong fixing point it the bracket that the tabernacle sits on.
    Then I was thinking about creating a second strong fixing point somewhere around the stern.

    What do you think of my idea?

    Cheers Tod
  2. todzippy
    Joined: Jan 2016
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    todzippy New Member

    Trident 24

    This is one of the Yachts a Trident 24
    Very strong old boats and solid thick GRP construction

    I would keep the roof on the cabin intact for strength but would lower the existing to match and level up with the fore cabin above the V birth, then would build my design around all this hiding and integrating the existing design.

    Attached Files:

  3. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    With structures you can do almost everything. Another thing is that, by weight or appearance, worthwhile or not.
    In addition to the stiffness and strength of the webs, you must consider how to join them to hulls, how to create the necessary embedding of the transversal beams with the hull, on the inside and the outside of the wet deck.
  4. gonzo
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    gonzo Senior Member

    The strong points are the tabernacle and chainplates on the mid-section. At the bow and stern, the chainplates. Usually there is also major reinforcement at the jib tracks and winches.
  5. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Yes, you can do this, but these particular boats would make really lousy catamaran hulls. To make them anywhere close to efficient, you'd have to separate the hulls by a huge amount, just to clear each's bow wave.

    What might be more interesting would be to cut both hulls in half and bond the bows, end to end. In this same vein, you could cut each hull down the centerline, then bond over the cut with a flat plate, making two asymmetric hulls. This arrangement would sail better, though the hulls will still be quite fat, at least the inside bow waves, will be modest and you can get the hulls fairly close together.
  6. todzippy
    Joined: Jan 2016
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    todzippy New Member

    Yes but don't forget I will not be sailing or going anywhere in this cat is will only ever move 500 meters from where i build to a permanent place of mooring. Basically I want to create a houseboat cat that sits at the top of a tidal estuary.


  7. todzippy
    Joined: Jan 2016
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    todzippy New Member

    Ok so I have had a think about this for the past week and have come up with a solution for anyone that wants to make a Catamaran for non-sailing use only with 2 Yachts. To strengthen up the structures I have thought of building 3 steel frames inside the hull that directs any forces down onto the keels. They will be fastened to connecting steels horizontally across the decks.

    Ive knocked up some rough drawings last night not professional but you can get my general idea.

    Dont think of the boat as a structure only as a shell
    You can build a structure on the inside and then create anything you want

    :NOTE The stern frame and steel connection obviously will not be resting on any keels but will only be there for stability purposes and restriction of movement in the main structure and for a open deck. As they are 2 Hulls all weight built above would be halved and shared between them.

    Attached Files:

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