Are these stringers??

Discussion in 'Boatbuilding' started by steury73, Apr 26, 2018.

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  1. steury73
    Joined: Apr 2018
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    steury73 Junior Member

    So, I recently acquired a boat - it was free and I know the saying that free boats are the most expensive, etc, etc. Anyways, got the boat - a 14' 1973 Steury, motor - 1980 35 hp OB Evinrude, and trailer for free so it was hard to pass up. Just got the motor up and running this morning (for less than $150), now I'm moving onto see if it'll be worth my effort to rebuild the stringers/floor. The floor was already partially torn out allowing easy viewing to the horribly rotten stringer/s.

    My question is regarding the red circled in the picture in this link - Imgur https://imgur.com/w4rVYsJ. There is a middle stringer, but are those boards laid horizontal on either side stringers? They're wood cored but I've never seen a stringer laid horizontally like that. I'm assuming either way they'll need to come out as they're rotted as well. Also why the bubbling? I took a sample and it's hollow where it's bubbling out. Was this done when the boat was built or a very sloppy re-build?

    Any advice/information is much appreciated!!
     
  2. rwatson
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    rwatson Senior Member

    I cant tell if you have circled the wetted out bit of the hull, or that funny pillow shaped blob that looks like it has almost raw Chopped Strand Matting wrapped around it.

    In any case, wood wrapped in Polyester resin is assuring the wood will rot.

    Ideally, the rotten wood wouldn't matter structurally, as it is just a filler to layer glass around. Of course the extra weight of the absorbed water is a negative.
     
  3. steury73
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    steury73 Junior Member

    Mainly the blob and what is beneath it. The blob is hollow but the wood within does run the length of the hull. So is the horizontal wood technically a stringer or any idea of its purpose? The wetted hull was just from sitting out in the elements prior to drying out. Maybe this will paint a better picture. https://i.imgur.com/CvcbSnn.jpg
     
  4. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    It's likely the wooden internal elements are just used as "molds" as they lay fabrics in the mold. It's not a structural element, though the condition the nearly naked mat shows, isn't contributing to the structure either. Saturate the exposed mat as best as you can and apply several layers of biax over it to insure it fulfills its role as a longitudinal element. I'd throw some biax over the centerline piece as well, insuring it has at least few inches of overlap on the hull shell, as the origional build method was certainly shy on techniques, resin and likely fabrics too.
     
  5. rwatson
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    rwatson Senior Member

    That's a lot better.

    When I said "wetted hull", I didn't mean wet from rain, but thoroughly soaked from polyester resin when built. See how the proper hull looks semi-transparent, but the "pillows" are very opaque and "stringy".

    Par has a good handle on it. Those "pillows" were just a cheap and nasty way of supporting the edges of the decks, giving them something to be attached to.
    You could just clean the timber out, cut holes in the right position to allow any moisture to drain into the bilges, and just leave it, and it would be structural enough.

    But, from a safety point of view, I would suggest cutting the tops off the "pillows", filling it with expanding foam, sanding the foam off level, and then coating the whole pillow in epoxy and cloth before putting the deck back on.

    The foam is to provide positive buoyancy if the hull gets swamped. The epoxy is to make the "pillows" really watertight, so the foam doesn't absorb water - which hand mixed expanding foam tends to do.
     
  6. steury73
    Joined: Apr 2018
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    steury73 Junior Member

    Got it. So they're not actually stringers (which I was leaning towards) and not really for structural support, but more a template or mold for the glass to become the structural strength of the vessel. I've got a lot of biax on order but judging from your responses, might need to order a bit more just to ensure it's strength and safety.

    Really appreciate you both taking the time to help me get a better grasp on what I'm dealing with!! Thanks rwatson and PAR!!
     
  7. PAR
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    PAR Yacht Designer/Builder

  8. steury73
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    steury73 Junior Member

    Just a few miles south of Dover.
     
  9. steury73
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    steury73 Junior Member

    Hey just wanted to give a quick update in case anyone was interested. I've cut out and removed the middle stringer and the 2 side support rails. Also think I'm done grinding as well - I know it's not perfect but I think it's good enough for my purposes. As I've said, I'm not doing a complete resto, just want it good enough to get a few years of fun out of her - she's already 45 years old after all. Plus as many know, grinding really sucks and I don't want to do it anymore honestly - but I'm always open to thoughts/suggestions from anyone on here!!

    I'm ready to get started on the fun stuff now! I've got 20 yds of 1708, 10 yds of 7 oz glass, 5 yds of chop strand mat, and a few gallons of epoxy (plus all the little stuff like 1/4" chop, cabosil, etc). I'm hoping this will all be enough! Now I just need to get the wood for the stringers and floor.

    I'm still undecided on what to do with those 2 side areas - thinking of getting some 4x8 foam boards from Lowes and just glass them in. Thoughts??

    Here's some pics of where I'm at now: Imgur https://imgur.com/qiQsdOo , Imgur https://imgur.com/6XcXgSi
     
  10. PAR
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    PAR Yacht Designer/Builder

    If you'd like to use as much of the epoxy as you have, lose the CSM and combo fabrics (1708). These will just suck up resin like crazy and add no appreciable strength to the laminate. Using foam is a good idea, though most of the stuff from Lowe's/Depot isn't sufficiently dense to use in sandwich construction, plus your "goo factor" (epoxy use) will rise dramatically with cored construction methods.
     
  11. steury73
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    steury73 Junior Member

    What about using poly? That's what I was going to originally use until rwatson said "In any case, wood wrapped in Polyester resin is assuring the wood will rot." That kinda pushed me away from it but didn't question his comment as I should have as I know it's quite common to use poly in fiberglass boats. I have access to poly fairly quickly and I'm pretty keen on using the 1708 since that's what I have the most of and feel like that'll give me the best strength. What about the foam boards with poly as well? Will they goo as much with poly as they would with epoxy?
     
  12. PAR
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    PAR Yacht Designer/Builder

    Polyurethane will likely melt the foam, unless they're coated with something to prevent this. 1708 is fine, though the mat will suck up an unusual amount of resin, where as straight 17 ounce biax fabric will not.
     
  13. rwatson
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    rwatson Senior Member

    The other advantage of Epoxy is that you can use much cheaper timber for the "shape" of the stringers, as the foam will be quite dear.

    It would be much cheaper than foam, and a lot more resilient and stronger.
     
  14. gonzo
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    gonzo Senior Member

    You can make stringers with polyester and a non-structural core. Chris Craft use to make them with cardboard tubes.
     

  15. fallguy
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    fallguy Senior Member

    The upside to using resin thirsty 1708 is it holds its shape well. No mat fabrics need to be wetted in place. If you already have 1708; I'd stay with it.

    Forget the polyester.

    Buy some marinepoxy from bateau.com. You'll need a little more than the estimated glass weight. And probably some cabosil for any filleting.
     
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