Glastron V178 stringers

Discussion in 'Boatbuilding' started by redfury, Apr 19, 2006.

  1. redfury
    Joined: Apr 2006
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    Location: Minnesota

    redfury Junior Member

    Hi, after spending an hour reading various posts in this forum, I have a couple of questions, and hopefully will prevent myself from doing something stupid in the near future :eek:

    I've pulled out the rotten wood of my 3 stringers ( tri hull ) and have started to work on replacing them. However, after reading some of the thoughts here, I would like some advice.

    The original stringers were solid wood, right down to the bottom of the hull ( to be specific, it looks as if some resin may have been dripped along the bottom and they didn't contact the floor perfectly, but they were right down against it. )

    I've seen comments about the stringers needing to be put on a layer of foam, so they don't create "pressure" points and let the fiberglass shell over them take the stress.

    I've also read about some boats having foam stringers...which has me curious.

    I cannot get all of the wood out of the boat because it's either too deep into the rest of the hull, or I can't get a saw in to cut the top of the stringer cap off to pry it out.

    What's my best bet to repair my stringers? Use wood, repair the fiberglass caps, or maybe even be so lucky as to use an expandable foam right in the stringer openings, trim and then fiberglass over the caps? Boy, that would be much easier! Of course, I want this to last, but I'm limited in my space to work ( it's all being done outside as I have no garage :eek: )

    Here's where I'm at currently.

    [​IMG]
     
  2. redfury
    Joined: Apr 2006
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    Location: Minnesota

    redfury Junior Member

    Anyone want to take a stab at an answer? If you can't tell by the picture, when they glassed the original stringers in, they didn't "wet" the chopped glass very well as I've got a lot of loose fiber in there.

    Another thought that I had...I'm planing on replacing the floor in 3 sections and have a 4x8 sheet of 3/8th's KEVLAR that I can use. I was thinking of using it either for the middle sheet, or for the rear section, or possibly using it for the front and whatever I have left for wherever it will fit, as I have a metal gas tank that goes right up the middle there.

    Anyway, what my thought was, was to use a minimal expansion spray foam and seal off the underside of the deckplates using it with the thinking that if I block the water from getting down by the stringers in the first place, I won't have to worry about any rot down there. I did plan on using some pvc pipe cut in half to lay along the bottom stringer as a channel for any water that may make its way to the bottom- back to the bilge area.

    Anyone have a thought as to the practicality/troubles I may have with this idea? My thought is that I get my foam floatation, it helps support the floor and the stringers, and I keep the boat a bit more "water" friendly if it ever decides to rain on the boat when I've forgotten to cover it outside ( with the drainplug out of course ).
     
  3. dereksireci
    Joined: Jun 2004
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    Location: South Carolina

    dereksireci Senior Member

    Stringers

    Maybe we should have a separate forum dedicated to transom and stringer replacement. The picture is easy to understand but the next post I didn't follow. I always thought of kevlar as a yellow looking fabric.

    What I would do:
    Support the hull so that it does not change shape when the bits holding it together are removed.
    Cut out those strips of old fiberglass stringer as close to the hull as possible. (Save them.)
    Use the strips as a templates for the new stringer bottoms. Cut and fit new stringers to the hull bottom. (There are several choices of material to use. See previous threads for discussions on this topic.)
    Grind the surface of the entire inside of the hull. Get the dust out and wipe with acetone when ready to do the glass work.
    Build a fixture to hold the new stringers in place.
    Tab the new stringers in with some fiberglass tape. Just enough to hold them.
    Use some putty to fillet the stringer-hull intersection, especially on the outboard sides where it creates a sharp angle. (A more sophisticated way would be to put a trapazoidal shaped piece under the stringer)
    Remove fixture.
    Cover stringers with fiberglass and overlap onto the hull. Stagger edges and all that.
    Install fuel tank.
    Fill void areas with A-B urethane foam.
    Put the deck back on and anything else that was removed.
    Fill fuel tank with gas.
    Fill cooler with the beverage of your choice.
    Purchase expensive inflatable PFD.
    Wear expensive PFD in case the boat breaks in half but tell everybody it's new and you just wanted to try it out.
    Go boating.

    djs
     
  4. redfury
    Joined: Apr 2006
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    Location: Minnesota

    redfury Junior Member

    Well, the Kevlar I have is a pre-made sheet that is 3/8ths or so thick. I was thinking of using it because of its strength and weight.

    So, what I'm gathering is that you wouldn't suggest that I re-use the fiberglass that makes up the stringers I have in there, but cut them out and build brand new ones?

    I guess I've been confused as to what actually made up a stringer. I was under the impression that the core material was the strength of the stringer.
     
  5. dereksireci
    Joined: Jun 2004
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    Location: South Carolina

    dereksireci Senior Member

    Stringer strength

    In the (bad) old days, they might have tabbed some wood to the hull for a stringer. In this case the wood provided the strength. The strength of wood varies with species, moisture content and the quality of the lumber. Each piece is a bit different. If the wood is entirely covered by fiberglass, it is protected from water and the glass contributes to the strength.

    Take the case of a much larger vessel. The stringers would normally be made of fiberglass and built in their own mold, then attached to the hull somehow. They could be hollow and be just as strong as they would be if filled with foam or something else. Filling with foam helps dampen vibration and noise but does not contribute to the strength.

    Another method is to build the stringers in the hull out of foam, which is easy to shape. The foam is covered by fiberglass. The strength of the fiberglass is much more consistant than wood. We can also control the direction of the strength by choosing different types of fabric. For example a +45° fabric is used on the vertical surface of the stringer which resists the buckling loads. A uni-directional fabric (carbon fiber in high performance boats) is used on top of the stringer to resist compressive loads. Try that with wood.

    Kevlar's unique properties are more with impact resistance and tensile strength. (resistance to stretching)

    djs
     
  6. redfury
    Joined: Apr 2006
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    Location: Minnesota

    redfury Junior Member

    Okay, so if I'm understanding this correctly, The fiberglass that I opened up to remove the rotten wood is actually the stringer, the wood was just something for the boat builder to build it around ( I thought the wood was the bigger issue because of the openings every few feet to allow water to drain to the bilge ).

    So, then the very important question would be this then...can I take what I have of my stringers and foam the inside where I removed the wood ( keeping the shape in place with braces, and then layer fiberglass over the top and down the sides to "rebuild" the stringers? The stringers are still quite strong even just as single lengths side by side ( I've stood on them ).

    Boy, it sure would make this first timer happy if I could do that! I don't think I could tackle the project of building new stringers straight off the original hull and not distort the hull ( potentially )...that and I don't have that kind of environment to do it in as all my work is being done in Minnesota, in my yard ( read:no garage or shop to work in ).

    I can put new wood in, and I know I need to have at least 2 pieces going across the width of the boat. I guess after reading all the advice here, I'm getting jumpy about what to do. I want to do it right, but I want to do it in my skill level ( novice ) without ruining my boat in the process.
     
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  7. dereksireci
    Joined: Jun 2004
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    Location: South Carolina

    dereksireci Senior Member

    Sounds good to me. You have to match the amount of time and money you put into a project with the value of the boat when it's complete. That's an easy thing to say and easier rule to break.

    Make sure the finished height of your stringers matches what used to be there. Also make sure those limber holes that allow water to drain to the bilge are stilll there when you finish. You need to rough up the old fiberglass with a grinder or course sandpaper for the new resin to stick to it. Use the foam on the inside and a couple of layers of glass over each and you should have a boat you can be proud of that will be stronger than new.

    Once I bought a sorry, leaking, potentially beautiful 16' wood runabout built in the late 1960's I think. Paid $62.50 for her. It was an early cold molded hull with no bulkheads or frames. From the outside the hull looked like a lapstrake Thompson. All mahogany and white oak besides the hull. I cut 6" off the stern to get to solid wood and installed a new transom made of two sheets of ¾" marine ply glassed together. I used all silicon bronze fasteners and the latest caulks.

    My friend and I took her on a sea trial when it was done. As we got into some chop he turned to me and said, "You must be worried about that transom?"

    My answer was, "Hell no, that's the only part I'm not worried about." The boat ran great.

    Trust your hands and finish your project.
     

  8. redfury
    Joined: Apr 2006
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    Location: Minnesota

    redfury Junior Member

    Thanks for the input derek, it's well appreciated. It's funny what a person can assume about something they know nothing about, especially when they know a little about something else and try to translate it to what they don't know about.

    Make sense? :D

    I'm more concerned about the transom being able to take the motor than anything else, since it's the most difficult part of the boat to access and repair.

    I can't believe that Glastron didn't encapsulate the wood with fiberglass when they originally built the boat, but that will have to change. I guess it'll just be a matter of drilling a few holes in it, CPES'ing it real good, and then running a few layers of 'glass over it for strength, and I'll probably get some diamond plate for the inside and out and then bolt the motor on. We'll see when we get to that part of the project. First things first, I gotta get the stringers and floor done so I can actually work in this boat without chewing myself up on those open stringers!
     
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