seat height ?

Discussion in 'Boat Design' started by valvebounce, Mar 15, 2023.

  1. valvebounce
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    valvebounce Senior Member

    Is there a set seat height for the front seats on a speedboat?
    I have a 14ft Broom speedboat (fibreglass)The swivel seats were mounted on timber boxes,and,with time they have rotted.The boxes were screwed to the deck using angle aluminium.I have filled the screw holes in the deck to keep it watertight.I have purchased 3" round metal pedestals with a 7" square foot.I suspect that won't be a secure enough fix.
    My easiest way to go would be to replicate the old seat support boxes and use angle.
    I didn't expect to need the height of the original seat support boxes,and didn't measure them.
    The space between the hull and the deck is quite shallow and airtight,which doesn't leave much room for deep fixings.The seats are on swivel plates.
    Is there an average height for the seats ?

    25hp with fins 003.jpg 25hp with fins 005.jpg 25hp with fins 003.jpg 25hp with fins 005.jpg
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    I think your best bet would be to build back some boxes for supporting the seats, similar to as shown in your photo above.
    Boxes would be capable of supporting and transferring the loads from the people sitting in the seats much better than any narrow pedestal could.
    Because you have such a wide base (relatively) with a box, screws would probably be sufficient to secure it.
    Whereas a 3" diameter pedestal on a 7" square base plate will have much higher loadings on it.

    From the photo I would guess that the seat is about 2' wide, and the base box maybe about 10" - 12" length and width?
    Re height, you could maybe experiment (using a beer crate perhaps, if not too tall) to see what would be the height that suits you best, rather than relying on anthropomorphic data to give you an 'average' height?
     
  3. jehardiman
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    jehardiman Senior Member

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  4. valvebounce
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    valvebounce Senior Member

    Thanks Bajansailor,I was thinking along the lines that you suggest.I would have had to add 3 or 4 layers of fibreglass on the deck,and make the base bigger to accomodate the 7" pedestal base.Seeing as the original boxes lasted for quite a while,I can't see why not just replace them.The seats are out of the boat,and the pedestals are temporarily attached,so I can offer them up to check the height.No doubt I will find a use for the tubuar pedestals elsewhere.
    many thanks for your reply. "V"
     
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  5. valvebounce
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    valvebounce Senior Member

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  6. jehardiman
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    jehardiman Senior Member

    FWIW, I have found the 70-80th male is "reasonable"....because you can't do it all.
     
  7. wet feet
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    wet feet Senior Member

    You could probably arrive at a good starting point by measuring how far you car seats are located above the floor.It won't be so different and if you err a little on the low side,it isn't so hard to add a packer beneath the seat cushion.
     
  8. Barry
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    Barry Senior Member

    Certainly the box method would provide a stable seat base as compared to a pedestal. It sounds like fastening a pedestal to the floor rigidly is doubtful.
    I see the space beneath the seats with either a pedestal or the current box size an inefficient waste of space. Ie you have quite a volume of space used only to hold the seat up.
    Starting from the center of seat for a reference point. ( and starting with the port side seat)
    From the center,
    1) I would extend the box out to the side of the boat so long as you do not need this space for paddles or fishing rods.
    2) extend the box closer to the front of the seat.
    3) leave the inside edge opposing the other seat the same as it will make it easier for people to walk
    4) extend the back of the box as far as the back of the seat.
    If you are not using the swivel and want seating for more people, the box could extend another 16 inches rearward to provide additional seating.

    For the Starboard side, you need to ensure that the box would not hinder control cables and the like.

    Build a rear access door to the boxes. Anchors, fenders, ropes, fishing tackle boxes, lunch kit, and any other gear that you normally carry can now have a waterproof out of the way storage place and provide a way to
    "clear the decks"
     
    Last edited: Mar 19, 2023
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  9. Ike
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    Ike Senior Member

    I have some diagrams that show human dimensions when seated. But the only one I could upload is a gif file. I have two others but they are in some strange format. If I can figure out how to convert them to jpeg or gif, I'll post them.
    [​IMG]
     
  10. wet feet
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    wet feet Senior Member

    I did a quick search for car seating diagrams and this very thorough version appeared.All(!) you have to do is determine which category is most applicable.

    [​IMG]
     
  11. DogCavalry
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    DogCavalry Senior Member

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  12. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Thx, been looking for something like that for general purposes. Saved.

    However, seems to be missing the various % of buttocks and beer belly girth of US populations, which would also be affected by at least age.

    As far as the seat height of the speed boat, I'd consider going the extra mile and installing a variable height and even shock absorbing seat. Impacts to the spine from "ridge" chopper style motorcycle or even cab-over truck with stiff springs and not enough load, might take 6 weeks to start hurting, then 6 months to figure out that is the cause of pain, then about 6 years for it to stop hurting.
    Lacking that, maybe go a bit low but with big thick soft flotation pillow.
     
  13. BlueBell
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    BlueBell . . . _ _ _ . . . _ _ _

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  14. fallguy
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    fallguy Senior Member


  15. valvebounce
    Joined: Dec 2010
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    valvebounce Senior Member

    Thanks for everyone's input,it has been quite valuable."V"
     
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