MC for Stringers?

Discussion in 'Boatbuilding' started by James04, Feb 5, 2021.

  1. James04
    Joined: Feb 2021
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    Location: CT USA

    James04 Junior Member

    Hi All,
    I will be replacing the stringers and transom in my 20' fiberglass Columbian 2000c. I will be using rift sawn white oak for the stringers. What is the maximum moisture content required before cutting to final dimension and glassing in the stringers?
    James
     
  2. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    Less than 12%
     
  3. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    James, what type of boat is a Columbian 2000c?
    I tried googling it, but I could not find out anything.
    Could you post some photos of her for reference please?
    And a photo or two of the transom and stringers would be useful as well.
     
  4. James04
    Joined: Feb 2021
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    Location: CT USA

    James04 Junior Member

    Columbian was a small boat builder based in Meriden CT. This boat is a 1977 Columian 2000c. The previous owner told me that Columbian licensed the hull mold from Grady White. I have no idea if that is true or not. But it does have a strong resemblance to many Grady White lapstrake models of that era. I have been unable to find any info or photos of any Columbians other than the Fury and a tri hull model. If anyone has any info I would greatly appreciate it. Especially any photos of this models interior.

    Obviously this will be a full restoration. I do not have photos of the stringers at this time. The boat is on my friends farm so I am not able to take any at the moment.

    Wow! Below 12%MC. I am a little surprised since the stringers essentially live in the bilge (wet environment). I am glad I asked.

    While I am at it. Coosa is quite pricey stuff. If it where you doing this restoration. Would you consider marine ply or some other less costly than Coosa option for the transom?

    James
     

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  5. bajansailor
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    bajansailor Marine Surveyor

    Thank you for posting these photos James - I see what you mean re how you will doing a full restoration, but it should be well worth it, as she does look like she was a very nice boat originally. The simulated lapstrake 'planking' in the topsides have a benfit in that they make the hull much stiffer compared to a non lapstrake hull.

    It looks like you will have to replace the bulkheads at the forward end of the cockpit as well - and take up the cockpit sole to get to the stringers?
    I presume that the sole is fibreglass over plywood - what sort of condition is it in?

    Re weighing up the pros and cons of Coosa vs marine plywood for the transom - what would be the approximate difference in cost (for you to buy) between the two of them?
     
  6. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    Forget the white oak, it's not a good application for it. Buy some clear DF, AYC, SYP or similar, fiberglass them all around with epoxy and enjoy the lighter weight.
    Plywood is absolutely fine as a core, just seal all the holes with epoxy plugs. This is also valid for the stringers, no fasteners in contact with wood coring.
    Don't buy fir plywood, buy Hydrotek.
     
  7. James04
    Joined: Feb 2021
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    Location: CT USA

    James04 Junior Member

    Banjan,
    The Bulk head will be replaced. The stringers stop at the bulkhead. Everything from the bulkhead back is completely rotted. The deck was removed by the previous owner more than 8 years ago that is when i purchased it for the trailer it was on. Everything in the cabin has remained dry and therefore not rotted. I will have to look at the construction a bit more to see if any repairs are needed there.
    Rumars,
    I am a woodworker and I own my own sawmill. So I already have the white oak. DF and southern yellow don't grow where I am in CT and I do not believe I can get cedar logs In the required length and diameter either. I am a a very tight budget with this project. It does not have the wife's approval. She thinks I am insane(did you see the photos?ha ha). So it would be good to use what I already have. It looks like the four stringers are made from 2x10x11'. Do you really think the weight would be an issue?
    Thank you both for your input,
    James
     
  8. Rumars
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    Rumars Senior Member

    It's not primarily about the weight, it's about the fact that white oak is not a glue friendly wood. If you must use oak, please read all about epoxy and oak. Do you have any black locust or ash in your sawmill? Or maybe tamarack?
    Another option is to make fiberglass only stringers, over a foam or cardboard former.
     
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  9. ondarvr
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    ondarvr Senior Member

    A tight budget and rebuilding a boat don't fit into the same sentence, although that's everyone's idea in the beginning.

    Do you want a project that will take a few years and many thousands of dollars to complete, or do you want to go boating?

    There is no right or wrong answer, both are reasonable, but the route to each one is different.
     
  10. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    James, re the stringers, you could (as Rumars suggested) simply make up formers from foam or even cardboard - the strength is not in the core, but in the fibreglass 'top hat' section that is formed over the core.
    I was involved in the past in building fibreglass boats that had no wood at all in them - the longitudinal stringers and frames were all hollow top hat sections, and they worked very well.
    Take good note also of what Ondarvr says above - re-fitting a boat is a bit like gambling. It is easy to get immersed in it totally, and then when you realise that the costs are increasing dramatically, you can't stop - you have to keep going, so as to not lose your investment.
    Do a careful estimate of the cost of the materials you will need, and the time you will need to do the re-fit, and then double it, and you might be in the right ball park.
     
  11. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Dry down to below 12% to as low as 8%.

    Allow it to go back to no more than 12%.

    You can use wo on that old boat repair, but you don't need it to be 1.5". An inch of wo is plenty.

    too wet and the wood will rot if you encapsulate it

    you can use roseburg marine ply for the transom, but use epoxy then to make it watertight
     
  12. James04
    Joined: Feb 2021
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    James04 Junior Member

    I was thinking I wanted something rot resistant for the stringers. However I have now read an article (Thanks Rumars!) regarding the poor bonding characteristics of WO and the less dimensionally stable character. Does red oak share the same issues?
    The same article goes on to say that rot resistance is not important for stringers. Do the majority of you agree with that? I do have quarter sawn ash (terrible rot resistance in my experience) that is ready to go. However I think they are only about 8' in length. Can I spice them and still get good structural contribution? What kind of splice if so?
    I may be able to get black locust logs. But that will set me back as they will need to dry from totally green. It also does not behave well while drying.
    Four DF 2x10's would not break the bank either.

    Regarding using foam cores. Would that not be a most costly option. Since you will have to use extra layers of glass and resin to make up for the lack of the structural contribution of the stringers?

    Regarding cost. How many gallons of resin do you think I will need? Is polyester acceptable? The deck and stringer area would be roughly 8'x11'. What thickness of marine ply is appropriate for this deck with four stringers across an 8' beam width?
    How many gallons of gel coat do you think for this deck and exterior of this boat (20' length)?

    Thanks you all for your comments!
    James
     
  13. Rumars
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    Rumars Senior Member

    Red oak drinks epoxy like a sponge, don't use it. Ash is fine as long as it's encapsulated. You will need to scarf them, plain scarf, minimum 8:1 slope, epoxy glued. For all glueing and laminating that has to do with wood you need to use epoxy. The main reason why the former stringers rotted, is the use of polyester resin. All corners have to be rounded, fiberglass does not like to go over sharp corners.

    If you want to use polyester, you need to do top hat stringers. They are either over foam, or hollow, over cardboard or plastic formers. Only you can decide on cost, polyester is significantly cheaper then epoxy, and can offset the cost of more glass. Selling the wood and buying polyester and glass can potentially be more profitable, you have to do the math.

    For the deck you replicate the original thickness, it's the simplest way. Once you have a ply deck, you use epoxy, and the finish will be paint. Gelcoat does not bond to epoxy.
     
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  14. fallguy
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    fallguy Senior Member

    ro has not rot resistance at all

    I just used some wo two days ago for a shelf cleat on my build. It is never coming off.

    you can use wo for stringers or you can make all the sole and stringers and transom using Roseburg marine ply from Menards if all is encased in epoxy and glass

    be forewarned any eposure of Roseburg edges to water results in delam overtime..it just does
     

  15. ondarvr
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    ondarvr Senior Member

    This always comes up in a rebuild, and the subject can be very controversial.

    The common line of thought is that polyester is the reason the wood rotted away. This is a bit of a misunderstanding.

    Boats were built with wood and polyester because it was cheap, readily available, easy to work with, and will hold up for decades.

    The point of failure is that it was all too frequently built by someone making minimum wage with no training, no skills, no understanding of what they were doing, and didn't care to understand it.

    These things were built so poorly when it came to encapsulating the wood that using epoxy would have made no difference in the lifespan, they would have rotted away in the same amount of time. It was common to have no glass over areas of the wood, it may not have even been resin coated.

    On paper the design and intended build procedure may have been great, but the execution was miserable.

    If you fully encapsulate a wood stringer in the correct amount of glass it will stay dry and rot free. That is until someone drills a hole in it and doesn't seal it up correctly. If you drill a hole and don't seal it, the wood doesn't care what type of resin you used, it only knows it got wet.

    You have a couple of options.

    Use a very expensive core that will need a bit of extra glass because it doesn't provide any strength, like foam, or better yet, hollow.

    Or use wood, then encapsulate it and make sure you don't let water get to it.

    Or the this option, use wood, but don't rely on it for any added strength, only rely on the laminate for support. This method is cheap and fast, just slightly heavier, but will be extremely strong for decades until the wood finally rots. Then, when the wood eventually rots, you still have the full strength that was originally required.

    This also tends to reduce the likelihood of rot too. Adding a thicker laminate tends to result in better encapsulation of the wood, so less chance of it getting wet.

    As for the choice of resin, both polyester and epoxy work, polyester is cheaper and easier to work with. If you were making a wooden boat, epoxy is really the only option.

    When rebuilding an old glass boat, epoxy doesn't have the huge advantage that it may appear to have on paper.

    It does make some people feel better though, so sleeping at night may be easier.
     
    Last edited: Feb 6, 2021
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