Gemini 105M and PDQ 36 -- Same Displacement?

Discussion in 'Multihulls' started by SPC, Dec 19, 2020.

  1. SPC
    Joined: Jul 2020
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    Location: Raleigh NC

    SPC Junior Member

    I'm having trouble understanding how the PDQ 36,which is 2ft longer and 4ft wider, managed the same 8000lbs displacement as the Gemini 105M. Is anyone here able to enlighten me?
     
  2. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

  3. SPC
    Joined: Jul 2020
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    Location: Raleigh NC

    SPC Junior Member

    It is rather hard to directly compare their drafts as per brochure, as the Gemini has centerboards and the PDQ has fixed keels: The Gemini has 1.5ft min and 5.5ft max: the PDQ has 2.82ft.
     
  4. TANSL
    Joined: Sep 2011
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    TANSL Senior Member

    The displacement depends on the length and beam in the waterline, the draft and the block coefficient. Therefore, if you do not consider all the variables, you cannot compare two different hulls or explain the differences or similarities between the two.
     
  5. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Agree with TANSL.

    Also what is the source of the displacements for the boats. Published displacement numbers can be intended as anything from bare boat weight to maximum displacement with fuel, water, stores, passengers, etc. Also published numbers can be based on anything from a somewhat generic estimate to what the designer calculated to the weight of actual boats.
     
  6. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    In the link below for the PDQ 36, they mention the displacement as being 10,000 lbs -
    PDQ 36 Catamarans For Sale By Owner – CatamaranSite https://www.catamaransite.com/brand/pdq-36/
    It looks like the PDQ builders went out of business some years ago.

    There are three PDQ 36's currently for sale on Yachtworld - here is a link to one of them - although Yachtworld do not usually include displacement in their adverts, and there is no mention of it here.
    1998 PDQ 36 Catamaran for sale - YachtWorld https://www.yachtworld.com/boats/1998/pdq-36-3705560/

    Gemini Catamarans are still in production, although the 105M model has been discontinued.
    Here is the specification for her on their web page - but they do not even mention the displacement here.
    Gemini Catamarans || Gemini 105Mc Design Touch Specifications https://www.geminicatamarans.com/Gemini-Models/Gemini105Mc-Specifications.html

    They do mention a 'weight displacement' of 9,800 lbs re this vessel for sale second hand -
    Gemini Catamarans Home https://www.geminicatamarans.com/GEMINI/catamaran-preview-basic-info?Vessel_id=614198

    SPC mentioned a displacement of 8,000 lbs in their opening post; my links above mention displacements around 10,000 lbs.
    It all depends on what is considered to be included in the 'standard' displacement.
     

  7. SPC
    Joined: Jul 2020
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    Location: Raleigh NC

    SPC Junior Member

    I was going off of Sailboatdata:
    Looking at a PDQ 36 manual, I see "Weight: 10000lbs", so maybe their data is off. That was closer to what I was expecting. I now understand just how imprecise those measurements are.

    I couldn't find the measurements in the Gemini's manual. The one linked above was a different design (the Legacy), though it has similar proportions so I guess that doesn't answer the question either.

    I will continue my research on how the hulls are different; I was just hoping people here might be familiar with these boats enough to already have the comparison.

    Thank you.
     
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