Hull construction composition (where to stop grinding?)

Discussion in 'Fiberglass and Composite Boat Building' started by Bigtalljv, Jun 17, 2022.

  1. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Hi,

    I think I’ve touched in this in other threads but I’m getting more serious in taking things apart now so I wanted to see if I could get some help.

    I am certainly not experienced with the details of hull construction over the years. I’m trying to identify where to stop grinding/peeling in my hull. I’m removing stringers which were set on balsa pads. The stringers have several layers of csm and roving over them which often extended all the way over to the adjacent stringer, like a whole extra skin. once cut these free I can pretty much peel each layer up by hand, just pull…

    under the stringers are balsa pads covered by more roving.

    under the balsa there is a pink layer of CSM, a layer of roving, then more CSM. under that is a dark layer which I “think” is the molded hull?

    how far down do I want to go to bond new stringers?

    if I remove the pinkish CSM-roving-CSM layer it seems like that where the easy removal stops but the hull starts to get a bit more flexible, do I want to add layers back or do i NOT want to remove the pinkish layers? (I think I’ve been told I do want to remove them)

    oh, and just some pictures of lakes of plain resin poured in there to fill voids…
     

    Attached Files:

  2. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Is this still your Radon 24 boat, or is this a new project?

    In a nutshell, I think that you effectively have to keep going until you find solid material to laminate on to.
     
    fallguy likes this.
  3. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Only remove the bare minimum.
    If it pulls out by hand, it goes.
    Then grind to a smooth enough surface for bonding to.

    For a few decades of service-
    Rebuild as original.
    No need to re-engineer
     
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  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    What Bajan said...

    I don't see balsa core. But balsa pads make me nervous. If there is a rotten balsa core, the boat is probably beyond practial repair.

    Support the hull well. Once you get to only the external skin; the entire boat may collapse. Roller trailer not enough, for example.
     
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  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    This make me wonder if there was disintegrated balsa here because it looks like a thickness where the gray is 1/2" above the rest?

    7287B45E-74F9-463B-A031-F5B737AE1C79.jpeg
     
  6. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    fallguy,
    The stringers sit on balsa pads and you are seeing the edge of one I cut through to remove the tabbing/skin. The hull itself is not cored.

    I like the bare minimum answer from blueknarr…it just needs to last another 10 or 20 years ;-)

    and I’m planning on only removing one stringer at a time but it’s supported well anyway. Removing them all sounds dangerous but makes for great boat ****.
     
  7. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Here’s the forward tip of a stringer on the balsa pad.
     

    Attached Files:

    fallguy likes this.
  8. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    And here’s the state of my stringers. I believe the forward and rear section are original. They are now four different heights. All stringers and balsa pads are coming out.
     

    Attached Files:

  9. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Yes it’s the radon I have posted about before. Last boat I’m ever working on, hopefully it gets finished….
     
  10. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Well, I know what I would do with it...

    I'd keep gutting one side until I could gut no more. Then I'd sand or grind it fairly flat. Then I'd paint it all with epoxy and any rough areas, I'd bond up with 2:1 fumed silica to epoxy by volume. Then I'd consider that the open slate for whatever..

    Definitely ditch the balsa pads. You can replace those pads with some smaller ones from pvc marine core.

    I will probably get some flack for the epoxy, but I'd do that even if I was using ve for the rest..jist to seal it all up.
     
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  11. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Back when that boat was made, generous amounts of chopped fibers were sprayed in lieu of mat, and sometimes even left fluffy as filler. Some hulls were almost entirely chop, but I never saw a Radon like that.
    The resin ratio was sometimes hard to control resulting in dryish layers that looked ok when more resin was sprayed on top of it, or sometimes the chop spray got too far ahead of the rollers, or both, anyway, the product was poor, but state of the art back then.
    Your job is to get rid of that crap without damaging the denser hull layup under it.
    I see a powered chisel in your pics, this should be used cautiously, so as not to damage substrates!
    #16 grinding discs are your best friend (and enemy) in removing the layers of bad laminate.
     
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  12. comfisherman
    Joined: Apr 2009
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    comfisherman Senior Member

    Either of these... and go up until you find good base to adhere to. It can be surprising how many layers pic up with lousy adhesion.

    6 hp shop vac running near the grind spot and lament the fact so few tyvek coverall companies have never met a man over 6'2".... grind until it looks purty... then realize new boats are almost easier than old ones...
     

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  13. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    Thanks guys. So due to an unfortunate incident with the sawzall and the bottom of my boat I have a bit more insight into the layup of the hull. The reddish layer is crap, it was put down for the balsa pads to adhere to, it’s arranged like tabbing, and once started it comes up by hand. The greenish layer under that is the hull from the mold, 1/4” or so and looks pretty good. Everything that went on top of it is garbage but it been through several revisions so I just blame everyone.
    I’m being careful with the demo hammer. It’s great for getting the tabbing off. With thr balsa pads there is room to cut the tabbing there and remove the stringer. Then the chisel can go from the inside and pick up the tabbing.

    I’m 6’7”, not helpful working in a boat hull. I got some 4x tyvek suits and they do all right, you get a lot sweaty in them but not uncomfortable as I was expecting.
     

  14. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    I suggest you take a really close look at the outside of the hull where you used that power chisel.I fear you will find crazing and if so it will make it easier for water to get into the laminate.
     
    mc_rash likes this.
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