Hull out of two semi-hulls

Discussion in 'Metal Boat Building' started by MrNewman, Oct 24, 2021.

  1. MrNewman
    Joined: May 2021
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    MrNewman Junior Member

    Hi all, ...and pardon me for this [probably] stupid question.
    I was drawing one pretty little thing, 26ft long and 2.45 meters wide, and one thought came into my perverted mind: why small, why not big?

    I'm limited (except my budget, he-he) mostly by a hangar size, and some logistics issues.
    But what if to weld two D-shaped semi-hulls (in dimensions that will allow to deliver them by any regular platform truck), and then glue + bolt/rivet them along the 'I' side closer to a shoreline, and certainly weld outer seam?

    Are there any known amateur/profi built hulls, made such way?
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Apologies Mr N, but I am not too sure what you mean here (and I am sure that many others do not understand either).
    Re your two D shaped semi-hulls, are these the ones that are 26' x 2.45 m wide?
    And do you want to join them together to make a 52' x 2.45 m. hull?
    Or will the hull stay 26' long, but twice as deep (with the two 'flats' of the D in contact) so that you end up with a O shaped hull?

    Can you post a copy of the sketch(es) you have made made?
    What do you intend to do with this hull once you build it?
     
  3. MrNewman
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    MrNewman Junior Member

    It's more like a rhetoric question/study, not an intention. Yet.
    sketch1635098974020.png
    I'm not near my laptop right now, so just a quick sketch based on respected Dehler38 layout, to clarify what I mean.

    It's definitely not an 8*5 meters overall (when clamped), but more close to some 11*4..4,5m (or, separately, 11*2..2,5 for each of two sections).

    PS I've probably used a wrong term. It's not about sectional shipbuilding in classic meaning when short sections attached next to each other, forming long hull.
    It's more about 'halves' building, or so. IDK the correct term for that
     
  4. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I think I understand now.
    If I was going to go down this route, I think that I would build an asymmetric catamaran in 3 sections instead - instead of bolting / welding two longitudinal halves together to form a monohull, I would build 2 asymmetric hulls and a bridgedeck section in between.

    Richard Woods uses this philosophy for his 28' Skoota -
    Sailing Catamarans - Skoota 28 transportable minimum live aboard cruiser https://www.sailingcatamarans.com/index.php/designs-2/6-powercats/264-skoota-28
     
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  5. MrNewman
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    MrNewman Junior Member

    Well, cat is cat, despite this Scoota 28 reduces the number of convex surfaces.
     
  6. gonzo
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    gonzo Senior Member

    This comes up time and time again in the forum. You need to make a cost analysis first, since the budget is an issue. It would be cheaper to fabricate all the interior as modules, cut all the metal parts and get them ready to weld, then assemble it at a bigger location.
     
  7. MrNewman
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    MrNewman Junior Member

    Basically, described is an example of pre-manufactured parts: two prepared, probably isolated [watertight] halves.

    Assembling smaller parts will take more time, will lead to fitting issues/construction weakness, and in fact it would be easier just to build 'normal way': I see no huge savings in this, in my circumstances.

    But actually renting - that's an issue.

    I have a hangar, but can't deliver too wide parts from it. And renting a big shop, with the direct access to the water, for a few years, is too expensive.

    So just in case, checking is it doable / are there any live examples of such a longitudinal sections builds.
     
  8. gonzo
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    gonzo Senior Member

    What you describe is not building it "normal way". Fabricating interior modules is a common method, which results in faster and cheaper construction. Fitting issues only happen when the workmanship is poor. It should not take several years to weld a hull and deck and install the interior modules. Anything is doable if you have enough time and money. However, there are more efficient ways of building a boat.
     
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  9. MrNewman
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    MrNewman Junior Member

    I don't want to argue, but probably we're talking about a little bit different things.
    I totally agree that it's easier e.g. to weld some chest outside the ship, and then simply to put it into its place, rather than make it in a limited space of the hull. And if building of small flat-bottom dinghy takes years - something goes wrong. 120%.

    But my question is about general possibility/allowance to build the hull such way: join two flat boards of semi-hulls, along, to form a centerboard, and a gross-hull, actually.
    I know a little bit about traditional sectional builds. But never met longitudinal joining.
     
  10. gonzo
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    gonzo Senior Member

    Morgan Yachts were built like that in fiberglass. If it takes you years to build a small flat bottom dinghy, this project is beyond your means.
     

  11. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Submarines are made somewhat similar to how the OP suggested.
    Not exactly, but.....
     
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