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Stringer repair

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  • Stringer repair

    Hi to everyone
    Have project boat, which is 21' ski boat, which previous had out board, and then someone cut it for inboard setup. I'm looking to out Chev BB and surface drive.
    Therefore filling holes and cut out in transom which appears to be in good condition, 2.75" thick
    Have drilled some holes from top of outer stringers which are 10x2" and they seem to be in reasonable condition judging from the colour of the timber
    However started to cut out of section of centre stringer which is 5.5x2" as this needs to be removed from back of transom as this is where the surface drive will come through, and found it completely rotted out
    Drilled down from top to check how far rot extends back, and looks to be 6' which leaves only 3' fro remainder of centre stringer to bulk head
    I phoned local boat builder and explained situation on phone, who advised that they would cut the top of the stringer off, dig out rotten wood and fill with resin/talc mix. Basically cast new stringer. Im assuming this is what they would do to save time
    However Im not sure to do this or replace the stringer with sandwich marine ply 0.7" thick (18mm) x 3 strips. I measured the glass skin on existing centre stringer and looks to be 3mm (0.120")
    I have 900oz and 600oz Biaxial fibreglass cloth here, and was going to use West resin 105

    Can I ask the experts is it better to cast new centre stringer, or cut out and replace new stringer with sandwich marine ply or PVC/Bamboo composite called corelight which appears to be water proof (just concerned whether fibreglass will take to it, although description indicates good gluing properties)

    I was going to look at reinforcing back of stringers and transom with additional 900oz cloth

    cheers

  • #2
    here are some attachments of design, and more important inside stringer layout, one picture looking down the stringer showing rot, and the 8" section of stringer I cut out
    actually not sure name of boat have tried to find out, this will be a bay boat, so it needs to take a descent wave
    Attached Files

    Comment


    • #3
      I wouldn't have it filled with the resin/talc combo they suggested, talc has little in the way of physical properties, you would need other products and fibers to make it strong enough, and then use a special catalyst for it to be done right.

      I don't know what the PVC/Bamboo combo is, but plywood is strong, easy to work with, and relatively cheap.

      When you say 900oz cloth, do you mean 9oz? cloth typically max'’s out at 10oz, Biax is something different and is normally 12oz or more, ranging to 32oz, there are custom made products though, so anything's possible.

      Comment


      • #4
        I will agree with ondarvr plywood is cheap and easy. There is some pour in stuff but sealed ply should last for years. As far as the transom just cut it out and rebuild it, beats a patch anyday. Are you using poly or epoxy resin?

        Comment


        • #5
          Ondarvr, sorry about that looks like I stuffed up the cloth weights, I meant
          600gsm which must be close to 24oz
          930gsm which must be close to 36oz

          Comment


          • #6
            Originally posted by bjf66 View Post
            Ondarvr, sorry about that looks like I stuffed up the cloth weights, I meant
            600gsm which must be close to 24oz
            930gsm which must be close to 36oz

            I had checked for your location because I thought it may have been in grams, but it wasn't listed.

            Comment


            • #7
              Would that be a pretty good candidate for seacast?? Archbuilder used it in a build and it turned out pretty sweet. Might be worth a look.
              1986 Bayliner 16' Capri, 90 hp Johnson (sold)
              1990 Chaparral 2000 SL Sport, 4.3L LX, Mercruiser Alpha I, Gen I

              Link to Chaparral restoration- https://forums.iboats.com/forum/boat-repair-and-restoration/boat-restoration-building-and-hull-repair/10286641-chaparral-2000-sl-sport-floor-and-more

              Comment


              • #8
                Originally posted by Baylinerchuck View Post
                Would that be a pretty good candidate for seacast?? Archbuilder used it in a build and it turned out pretty sweet. Might be worth a look.


                It would work.

                Comment


                • #9
                  Proshadetree
                  Thanks
                  The surface drive will be mounted below the cut out on transom, as drive bottom will sit approx. 1" above transom base, so strength should not be compromised with filling the previous hole where inboard was
                  I've previously used West System 105 epoxy so was going to stay with this as feel a little more confident with it
                  Was hoping to get the stringer and transom sorted over our christmas period holidays, then can look at mechanical issues in new year
                  although I know I what I want to do with twin turbo BBC, Daytona crash gearbox, feeding into parallel drop gearbox then into arneson surface drive
                  Fortunately have all the mechanical ready to go
                  Just want to make sure I get the hull nice and strong as dont want it turning into submarine

                  cheers

                  Comment


                  • #10
                    I would use new plywood. I wouldnt even deal with the existing stringer. I would put on a tyvek suit, fire up the saw, cut out the remainder of your hollow stringer, then fire up the grinder with 24 grit discs and grind the inside of the hull to where I would layout the new stringers and bulkheads. Then I would use poly and tab and glass everything in place.

                    I would also replace the entire transom as it looks like it was worked on at one point as well.
                    Last edited by Scott Danforth; December 7th, 2016, 03:31 AM.
                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                    Past Boats
                    1970 Wooster Hellion - Merc 9.8
                    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                    What’s behind you doesn’t matter.Enzo Ferrari

                    Comment


                    • #11
                      took the liberty to make your pics visiable without someone clicking on them









                      Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                      1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                      Past Boats
                      1970 Wooster Hellion - Merc 9.8
                      2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                      1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                      What’s behind you doesn’t matter.Enzo Ferrari

                      Comment


                      • #12
                        Do you know who modded the boat to start with? Did they use poly or epoxy? Don't really matter if you use epoxy. I will assume you will paint the repair and not gelcoat. When using epoxy you dont have to use as thick a cloth at least. If you rebuild the transom rather than patch it will save quite a bit of weight on the back of the boat as well. Seems like a cool build either way. Going to keep an eye on this.

                        Comment


                        • #13
                          Dear All

                          had a poke around the centre stringer last night, dug out timber which was 140x45mm timber, so now have over 5 of 9 ft stringer cleaned, timber was toast
                          placed a heater in the channel for approx. 90 min all dry now,
                          The fibreglass skin on stringer is 3mm (1/8"), and looks to be adhered well to floor, the stringer needs to be cut down to make room for the arneson drive, dropbox and driveshaft on inside, so not sure how much of the stringer height I should leave

                          Original boat transom came with another small pod (attached picture) which I took off hence the exposed wood, as I wanted to have a quick look at what was getting myself into first, as need flat surface for surface drive to bolt so it had to be removed

                          the transom is 2.75" thick
                          Unsure what /whom built boat, someone had advised the boat was a cut down 26' boat, however still trying to reach out to people in race ski scene here to find out some details
                          Gelcoat is in good condition, boat had been sitting fro 8 yrs before I picked it up
                          There is a water ballast tank in front of the centre stringer, I'm wondering whether there is some issue going on up front with water tank/or perhaps its just fibre glassed lined, which had been leaking

                          Not sure whether I need the ballast tank and could better use the area

                          Comment


                          • #14
                            You will be further ahead to not try to save the fiberglass that once covered the wood in the keel stringer
                            Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                            Past Boats
                            1970 Wooster Hellion - Merc 9.8
                            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                            What’s behind you doesn’t matter.Enzo Ferrari

                            Comment


                            • #15
                              Sign up today
                              I totally agree. Cut and grind out the old stringer channels and start fresh!!!
                              1961 Lonestar Flamingo - SPLASHED...Kinda!!
                              Fabricating Decks, Stringers, and Transoms
                              Paint Your Boat with Tractor Paint...Say What!!!

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