Need help with dimensions please.

Discussion in 'Boat Design' started by terry32506, Jan 28, 2010.

  1. terry32506
    Joined: Jun 2009
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    terry32506 Junior Member

    Hi all..I have been building an 8 foot pram and wanted to show one of the diagrams showing the positioning of the center seat.I dont know if its just me or not but it seems that the center seat positioning is not quite right. When I was building the boat the plans said to put a spreader across but didnt indicate exactly where so I assumed at the middle mark 48" ( dead center of the boat)..I hope that was right? So I then thought ok thats where the seat is suppose to go dead center in the middle at the 48" mark but when I looked at this diagram the center width of the seat is positioned at the 52 3/4" mark which is obviously not dead center..To me I would think the seat should be dead center , or is this the correct positioning shown in the diagram? Also wondering about the oarlocks being 12'' back from the center of the center seat , does that also look correct?

    Thanks for all of your help.


    Terry


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  2. Landlubber
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    Landlubber Senior Member

    terry,

    it sounds about right, the nboat is 96 inches oa, so the remainder aft is 38.5 inches, that is full length leg brace room, so any further aft would cause bending of the legs, not a good idea.
     
  3. terry32506
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    terry32506 Junior Member

    Hi Landlubber, I dont think I explained myself very well..Understandeably wouldnt want to bend the legs...What I am meaning is for the seat to be positioned more towards the bow allowing the even amount of room from either end of the boat...Am I making sense or no? I can take it lol

    What my thinking was was to measure from the bow back to the batten like shown in the diagram but to 43 1/4'' which would make the center seat in the middle. Is that making sense or not a good idea? Lots to learn thats for sure. :)

    Ideally what I am wanting is as much room as possible from the center seat to the stern for fly fishing and also because I plan to make a small bench at the back as well.


    Terry
     
  4. alan white
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    alan white Senior Member

    I think what you're missing is the greater bouyancy of the stern. Placing the rower further forward would upset the boat's trim, with the bow down a bit.
    While you're measuring inches, you should be measuring submerged volume.
     
  5. TeddyDiver
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    TeddyDiver Gollywobbler

    Like Alan and Landlubber said the main factors in this are the buoyancy and the length of you legs.. Most secure solution is to instal partial stringers with a little additional length for the seat to be attached to. Then you have the an option to move the seat some.. (few inches to stern me thinks)
     
  6. terry32506
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    terry32506 Junior Member

    Thanks guys I appreciate your input..Makes a lot of sense now. Thanks again.

    Terry
     
  7. Ike
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    Ike Senior Member

    Alan got it right. You want the boat to be balanced fore and aft. On my 12 foot rowboat the ballance is a little to far forward when one person is in the boat. With one on the middle seat and one on the aft seat (especially if it's my wife who is very small) the balance is about right. The smaller the boat, the more important this becomes. Years ago a saw a dinghy that you coulld move the seat fore and aft to get the right balance.
     
    Last edited: Jan 29, 2010
  8. terry32506
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    terry32506 Junior Member

    Hi IKe, makes perfect sense and for sure wouldnt want a boat like this to have the seat in the wrong place.

    I am at the stage now of putting on the outer gunwales which I plan to stain and varnish but cant decide if I want to have them on first before painting or later install them. Seating and corner knees will be varnished, outside I want to paint it white but on the inside not sure , maybe a light gray. I really want the boat to also look good. White will show the most contrast from the seat but too hard on the eyes in those bright days.

    Even though I like white for the outside I am not totally sold on that , perhaps another color is better.

    Have any suggestions?

    Terry
     
  9. TeddyDiver
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    TeddyDiver Gollywobbler

    A bit cream toned white is my favor white..
     
  10. terry32506
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    terry32506 Junior Member

    Hi TeddyDiver , would the cream color be hard on the eyes to look at on bright days?
     
  11. TeddyDiver
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    TeddyDiver Gollywobbler

    It's best you to take a colourchart outside in a bright daylight and make up your own mind. After all people do have somewhat variation in their sensitivity to light. I never need sunglases, not even out here..
     

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  12. terry32506
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    terry32506 Junior Member

    Very good, I will take your advice on the color charts and take it from there.


    Terry
     
  13. aranda1984
    Joined: Jan 2010
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    Location: Vancouver, B.C.

    aranda1984 aranda1984

    Hi Terry, fellow British Columbian...

    May I suggest something that would solve your dilemma.

    Under the seat there is a block where the seat is bolted to the boat.

    From the look at the sketch, I think that you should make that block longer. make it stick out about 4 to 6 inches towards the stern.

    Drill mounting holes about 1" apart.

    Now you have a seat that you can adjust to the weight of the rower to maintain proper trim.

    As far as the oarlocks are concerned, finish the boat, sit in it and temporarily clamp the oarlocks to find the best position.

    It is getting too complicated, but once you find the perfect position for the oarlocks, you can mount them (clamp them) also in an udjustable manner.

    Good luck,

    Stephen I. M.
     
  14. terry32506
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    terry32506 Junior Member

    Hi there Stephen, yes good ol BC land of mountains and water and lots of fishing :)

    Thats a great idea , I will definitely consider that option and also thanks on what to do with the oarlock situation.

    Terry
     

  15. alan white
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    alan white Senior Member

    The idea of lengthening the seat supports makes a lot of sense. Rather than making lots of holes, however, I'd suggest using clamps to home in on the sweet spot.
    Also, if possible, have someone who is accustomed to rowing and row boats row alongside (or walk the dock or shore) and tell you how the boat's trim looks fore and aft.
    Usually, the designer has already found the right row position. I think you'll discover the seat is correctly located. It is pretty vital though, the smaller the boat.
     
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