Determining dinghy seat location

Discussion in 'Boat Design' started by Riptide, May 3, 2011.

  1. Riptide
    Joined: Jun 2010
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    Riptide Junior Member

    I've recently laid up a dinghy hull and am ready to put seats in. The fore and aft seat will be molded in and filled with foam. I am undecided on how I'll make the centre seat. What factors determine how far below the gunwale my seats should be located? I want a good balance between legroom and stability. I dont think a high center of gravity is desirable.

    Also, has anyone got a number for the typical distance from the transom to the edge of the aft seat? I will be powering the craft with a 2hp outboard and would like to have enough room to properly operate the motor.

    It is a 9ft fiberglass dinghy with a 4ft beam. I can't remember the depth... I can measure that if it helps.

    I am completely new at this, and it has been a fun project so far (and more time consuming than I imagined). I'm really looking forward to all of your suggestions and getting this boat in the water!

    Attached Files:

  2. Frosty

    Frosty Previous Member

    Just done this same thing last week. I guessd at first and the oar locks were way out.

    The only way is to put the boat in water and sit in it. Take a box or something to sit on and shouffel about until its trimmed.

    Take some oars with you and hold them in a comfortable working position.

    Don't forget a felt tip pen to mark you findings
  3. tom28571
    Joined: Dec 2001
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    tom28571 Senior Member

    Probably the most useful answer you will get.
  4. anthony goodson
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    anthony goodson Senior Member

    How refreshing ,common sense.
  5. Riptide
    Joined: Jun 2010
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    Riptide Junior Member

    Thanks for the suggestion. I'm already planning to to this for the center rowing thwart and oarlocks. (it's the construction I am undecided on)

    But before I worry about that, I've got to determine a good seat height and install the fore and aft seats. I'm hoping someone will be able to give me some suggestions on that matter (height or distance from the gunwale.) Perhaps someone has a dinghy of a similar size they could measure?

    Thanks again.
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    BATAAN Senior Member

    Do the same with them. Dummy up with boxes or scrap wood and sit in the boat in the water. Glassed in rigid foam is not necessarily the best approach.
    For the center wood thwart, the best way is that adopted by Dyer for their famous Dyer Dinghy, a very early and durable F/G boat which just goes on and on it seems. I had one for 20 years and gave it to my son and he can't wear it out. The thwart stops a good inch from the glass, hanging in space by a pair of bronze knees each side. This makes an arrangement so when you tweak the flexible boat heavily by collision or squeeze the rigid thwart doesn't poke a hole in the side. Most F/G dinks suffer failure around the thwarts for this reason.
    The flotation in a Dyer is plastic coated foam blocks strapped to the forward and after thwarts. See second photo.

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  7. jarmo.hakkinen
    Joined: Jun 2007
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    jarmo.hakkinen Junior Member

    A good starting point for determining seat heights is 6 inches (150 mm) below gunwales. And for the oarlocs, they could be about 12" (300 mm) aft of seat.
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