another stringer & bulkhead build up

Discussion in 'Boat Design' started by aboyd, Jul 19, 2009.

  1. aboyd
    Joined: Jul 2009
    Posts: 23
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    Location: Fenwick,Ont

    aboyd Junior Member

    Just want to say hello to all, and am amazed at the wealth of knowledge that is floating around here. I am a new one to posting so i hope i'm getting it right. there is a couple questions I seek answers to on converting my rotted out Grew 250 which is a 25' from a hardtop to a centre console.
    1- When removing the hard top, cutting about 4" inches or so from rub rail on deck, will this be enough support for the sides when boat is complete or will i need bulk head extensions coming up to the underside of deck/hull joint.
    2- how much support should be under a 25' boat while pulling stringers and bulkheads out. I read one post were it was suggested to support on either side of transom and 1 support where bow and bottom side tappered together.
    3-when tabbing new stringers and heads in place can any material work---rubber,plastic. i read that someone used popsickle sticks would that not create air gaps condesation problems???
    4-the original stringers are made from mohogany is this or another type of board wood (ash, white oak) need to be used or will marine ply be sufficient.
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It would be easier to keep track of what you're doing, if all the questions were kept in one spot, rather then in various sub directories.

    Second, without pictures, it would be difficult to make structural recommendations, though I'd think you'll need some athwartship stiffness left intact or accommodated for.

    You need enough support under the boat to prevent the hull from distorting when structural elements are removed. How much depends on each boat and the amount of work it needs.

    Stringers come in two types, one has the core material (originally mahogany in your case) as a structural element, the other; the core is just a form that the laminate is shaped over and the laminate is the structural element. In the case of the laminate being the load bearing element, you can use stiff mashed potatoes as a core material, so long as it hold the 'glass in shape until it's cured.

    If your stringers were mahogany, it's very likely they also served as a load bearing element. You need to use a similar density lumber (not plywood, which is much weaker in this application) and the same laminate schedule. If you increase the laminate thickness you can change the stringer material.

    The other questions about wax coatings and butyl stringer bedding are not going to work as well as other materials.

    In short, if the stringers are tabbed well, using epoxy, then you'll be dead by the time this becomes a problem again. On the other hand, if you do a half assed job, like the manufacture, then it'll last about as long.
  3. aboyd
    Joined: Jul 2009
    Posts: 23
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Fenwick,Ont

    aboyd Junior Member


    thanks for the info PAR. sorry about the subs I thought I was in the wrong category in the first place but I guess with such a mundane type of question that has probably been posted countless times. I thought no one was answering. just ordered Dave Gerrs elements book should be very helpfull in my buildup.
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