Stringer replacement

Discussion in 'Boat Design' started by 10571z, Jan 23, 2014.

  1. 10571z

    10571z Previous Member

    Hey Everyone

    Me and a friend just purchased a project boat which needs the stringers replaced. Me and my mate who is a carpenter are going to do most of the work.
    A few questions.

    1. Should the stringers be layed on the bottom of the boat or should we put something underneath so its not touching directly. We were thinking of using expansion joint foam undeneath if need be ... filler.jpg

    2. What type of timber is best? Is Kd Hardwood good for the job? Im located in Australia so local timbers would be easier to get

    3. How do we waterproof the timber?

    4. When attaching the stringers to the boat is in best to wrap fiber glass right over the stringers to do both sides with one piece or just use strips and do a right angle from the base about halfway up the timber on each side?

    5. How many layers of fiberglass?

    Anymore tips would be great.


    Here are some pictures
  2. boatbuilder41
    Joined: Feb 2013
    Posts: 163
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    Location: panama city florida

    boatbuilder41 Senior Member

    Before you go fitting ay kind of material, make sure everything is true, plumb and level. No hook in the bottom, .. im not familiar what kind of wood is available in your region.
  3. 10571z

    10571z Previous Member

  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Chopped strand mat is worthless, in regard to strength and stiffness. It's a bulking agent and only necessary in polyester/vinylester laminates. There are rare occasions it's used with epoxy, but for cosmetic reasons only.

    You want to use cloth or knitted fabrics and the schedule is dependent on the loads. These are determined by the boat, so what is the make, model and year of this puppy? How is it powered, etc.? Next you'll need to make a resin system choice - epoxy (the good stuff), polyester (the weakest and cheapest stuff) or vinylester (nearly as good as epoxy in both cost and strength). If you elect to use polyester or vinylester, you'll want to use a "combo" fabric, such as a 1208, which saves some time. Alternatively, you can use alternating layers of mat and fabric. With epoxy, you'll just use cloth.

    As previously mentioned, you should insure the boat hasn't developed any weird distortions, from the weakened longitudinal supports. This means jacking her up and supporting her on her centerline and along the chine (usually). The chine and centerline are typically dead straight in the last half of the boat, so if it isn't, you'll need to address these distortions (not unusual).

    Once braced so she's not going to move, distort as you walk around in her and do stuff, you can consider how to replace the stringers. By the looks of the photos, the wood used was way too thick to accept tabbing. If you want wood to stay in place, you have to use relatively skinny stuff, laminated together. 1x stock (1x4, 1x6, etc.) is the typical rule of thumb. So toss the 2x6's and glue together 1x6's to make the same dimension lumber.

    Once these are cut and shaped to fit the bottom, they are laid in a bed of moderately soft goo or over foam. This prevents hard points from developing in the hull shell. Once the stringers are standing up on their edges in a bed of goo (3M-5200 works good), you'll apply the tabbing. The amount (again) is dependent, but looking at the old tabbing will offer a clue, so try to match the thickness of this tabbing, with a little more not hurting anything.

    There are hundreds of previous threads about tabbing in replacement stringers, so you'd be best advised to do some reading through old threads about this process. Spend a few hours looking at the techniques others have taken and you'll be better armed for your project, with a bunch more question likely too.
  5. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Been some bush carpentry going on in this boat, even down to the gum leaves laying around !
  6. Poida
    Joined: Apr 2006
    Posts: 1,189
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    Location: Australia

    Poida Senior Member

    I thought my boat was bad and was considering making a new hull.

    It looks like some of the timbers are nailed into position.

    If that can be restored, makes me think that maybe I can redo mine.

    Gum leaves are sent by the devil. They get in everywhere. My boat is parked under 4 of them and you can't gum leaf proof your boat. They are always falling all year round and even get into the slots of the air vent of your car, eventually working their way down to the fan making it sound like a piece of cardboard in the spokes of a bike wheel.

    Good luck with the restoration. Have you fired up the engine yet? Probably raw cooled and maybe rusted out, best to try that before you start spending money on the hull.

  7. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,390
    Likes: 1,039, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    The real problems with gum trees comes when they drop limbs, good reason not to camp under them, or have them near a house. But, yes, the leaves play havoc as well. Otherwise a magnificent thing !

  8. 10571z

    10571z Previous Member

    Thanks for the replies everyone. Some really helpfull stuff. The gumleaves came with the boat under the deck i think but im sure the ones in my backyard added to it while we were working on it.

    The Wood work in the boat to support the floor was shocking and some horrible carpentry went on. The stringers were rotten badly in places and the other timber was barely held together by nails. This will be all redone.

    As for the hull its actually pretty good condition.The outside looks great and the inside is looking fine besides the rotten timber.

    The engine which a Holden 202 is also working fine when it was fired up and an extremely simple and cheap engine so any issues should be sorted fairly simply (hopefully)
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