Fiber Glassing a Wooden boat

Discussion in 'Boat Design' started by Cmw505, Aug 12, 2019.

  1. Cmw505
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    Cmw505 Junior Member

    So to provide some context i'm adding fiberglass as part of the design to a wooden hull is there any way to safely do this? and by safe reduce the risk that this inherently causes as teredo worms are the bane of the sea thanks.
     
  2. rwatson
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    rwatson Senior Member

    You are going to need to be more specific.
    "Wooden" could be Plywood, Planked, Strip Planked or combination of these.

    In any event, bear in mind that with wood, you need to use Epoxy with the Fibreglass, and NOT another type of Resin.

    For Carvel or Clinker planked wooden boats, Epoxy Coatings on the wooden planks are unpopular, because they tend to make the hull retain moisture, which encourages rot - an even worse threat than Toredo Worms.

    The old method was to use Creasote, but that has been found to be Carcinogenic, as well as creating problems for anti-foul and paint systems. It is also illegal in many countries.

    There are many articles you can Google, that talk of using Dynel, or similar high tensile fabric instead of Fibreglass, to coat the underwater parts of wooden hulls.

    I found some comments about worm protection here
    "An improved method is provided for solving the age-old problem of wood-boring marine organisms. Wooden structures which are exposed to sea water can be protected from shipworm infestation by surrounding the structure with a nonwoven fabric having an effective pore size of less than 200 microns. Nonwoven fabrics of non-cellulosic organic or inorganic fibers are suitable. A self-bonded nonwoven fabric of polypropylene fibers is preferred."
    US4098955A - Prevention of shipworm infestation of wooden marine structures - Google Patents https://patents.google.com/patent/US4098955A/en

    Depending on your length of time in Toredo waters, and how often you "haul out", you may find a solution like two-part Primacom more than adequate for protection
    https://international-yachtpaint.com/en/au/boat-paint-products/primers/primocon
     
  3. Cmw505
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    Cmw505 Junior Member

    we'll i haven't decided as to the method i'm going to use i'm still throwing around options the main three things i'm looking for in my design is hull strength,stability, eco-friendly anti-fouling , open ocean capability. so blocking teredo's is my number one as i'll probably be in there territory a long while with it.
     
    Last edited: Aug 12, 2019
  4. upchurchmr
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    upchurchmr Senior Member

    Epoxy and glass will give strength (but we need to know the hull construction and thickness), stability - due to protecting the wood from moisture which causes shrink and swell, and will block teredos.
    It does need to be painted for the epoxy to survive in the sun.
    Google "Gougeon Brothers on Boat Construction" which is a free download from the guru's of epoxy boat construction.

    Watsons reference to non woven polypropylene is new to me but might be better - since it appears to be based on actual research. Didn't read the article yet so I don't understand how to bond it on.

    Dynel may be high tensile, but it has to stretch a lot to add strength to a hull. By that time the hull is busted. It has been credited with keeping water out after hitting a rock and breaking the hull structure - because it stretched without tearing.

    Good luck
     
  5. Cmw505
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    Cmw505 Junior Member

    thanks mate
     
  6. Ike
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    Ike Senior Member

    You have opened a can of worms. This topic has been cussed and discussed many times here on BoatDesign. There are strong opinions on both sides, to do or not to do. This method is often used to extend the life of an old boat when the owner doesn't want to go to the expense of fixing the problems with the hull. In my opinion it is not advisable on a new boat. Any flaw in the fiberglass sheathing allows water to get into the wood and then it is trapped. The result is rot. But, some well known designers have used this method on their designs, with success.

    As was said above, use epoxy. Then paint over the epoxy otherwise the sun will rapidly degrade the epoxy. I have done it both ways and the boat I painted looks like knew, and the one I didn't looks, not so good. I plan on painting it.
     
  7. upchurchmr
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    upchurchmr Senior Member

    Read the Gougeon book.
    There are a lot of opinions, but theirs is backed with scientific research and lots of years of experience.

    An epoxy/ glass coating only works if it is not broken.
    You have to be consistent with your maintenence and inspection, or limited areas can be damaged by rot.
    The best thing is the area is small instead of wide spread as in most traditional wood boats (assuming the damage area is small).

    Edit to tell you a little experience I had on the subject.

    I bought a used 20yo plywood Tornado, built of 4mm tortured plywood and epoxy/ glass. When I got it I stripped the outside glass epoxy so I could "improve" it.
    There was a small area about 3"x5" where there had been grounding damage, and the epoxy/ glass was not replaced. That area had a 2"x 3" area of rot, thru the first ply layer.
    3 ply plywood. I have no idea how long the damage existed.

    There was no other damage in the 2 - 20' hulls. I thought that was really good for plywood .160" thick.
     
    Last edited: Aug 13, 2019
  8. Cmw505
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    Cmw505 Junior Member

    lemme put this way i'm trying to apply an ecofriendly coating that stops teredo's on the wooden haul that is currently being built rot or not if it can't stop the boat from being eaten then it really does'nt matter so i'm trying to go at that angle eco-friendly and stops teredo's.
     
  9. Rumars
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    Rumars Senior Member

    The only "eco-friendly" teredo stopper is traditional coppering. That at least is partially recyclable unlike epoxy and fiberglass.
    Since you did not tell us how the hull is buildt (or going to be if it's just a design now) we can not tell you what is best.
    Today the normal procedure is to keep up on the antifouling, that also keeps the worms away. Is there a reason for you to do otherwise?

    Please tell us: carvel, clinker, what fastening type and material, or cold mold, strip plank, plywood, etc. Without this info no meaningfull answer is possible.
     
  10. Cmw505
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    Cmw505 Junior Member

    thank you rumar it will be most likely carvel built and i'm considering Douglas fir,silicon bronze fasteners and an almunium mast(x2).

    Some notable things
    -looking at a modified full keel
    -two mast gaff rig

    just listing anything i can cause i'm sure y'all might know something i don't.
     
  11. Rumars
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    Rumars Senior Member

    For a traditionally fastened boat (screws or rivets) your only option is coppering. There is no way to put a light sheating of glass over traditional carvel. A heavy sheating is possible but makes no sense in a new construction. It is much simpler to go to a glued construction method then apply a light sheating for worms.
    May I ask why you desire carvel? The cost of silicon bronze fasteners is likley to exceed the cost of epoxy for a simple strip plank build.
     
  12. Cmw505
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    Cmw505 Junior Member

    Hey Rumars seeing as it's smart to prepare for the unprepared carvel seems to provide decent haul strength from what i've read. And i'm accounting for quite a few things as the ocean isn't exactly a gentle creature. So to break it down 3 things i'm looking for in the hull design.
    -Durability
    -Stability
    -Strength in rough conditions(angry squalls, microbursts, etc).
    -56' from bow to stern
    If coppering is used how will this impact the oakum?.
     
    Last edited: Aug 14, 2019
  13. Rumars
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    Rumars Senior Member

    I don't know where you get your info's, but I am guessing your literature is at least 50 years old, probably older. Hull material does not count, the design goals do. Those determine ultimate scantlings and ideally the hull material and shape.
    Carvel is just one method of building and with non-ferrous fasteners and bottom coppering a very expensive one today. We don't live anymore in a time where lead for the ballast is basicly free and bronze screws are 50ct/lb. Today you think more like 1$/lb for scrap lead and 1$/screw. I leave it to you to discover the price of pure copper sheet for coppering.
    Today home boatbuilding is about building and not sailing. The used market offers anything you want at cents on the dollar.
    If you want to build don't get hung up on the hull material and building technique. Just buy a plan for a boat you like, or comission a new design to your specifications.
    Just to be clear: wood rots, steel rusts, plastics decomposes, aluminium desintegrates galvanically and ferrocement shatters. A boat can be buildt to Lloyds ice rating in any of those materials and have a reasonable lifetime.
     
  14. Cmw505
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    Cmw505 Junior Member

    I was referencing the design with carvel able to stand up to stress alittle more, but yes the book i have on this subject may is pretty old (1941)but that's why i'm on here to make a time investment for a decent outcome rather than rush and rely on one source and build something that will probably end in disaster as my knowledge is not as complete as others. What would you recommend instead of silicon bronze?
     

  15. Rumars
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    Rumars Senior Member

    Capable of "stand up to stress a little more" compared to what? Carvel is the least structurally efficient method to build a wooden boat. It's advantages were the scalability, ease of repair and relative form freedom, but that was compared to other contemporary build methods like lapstrake (clinker) and double planking.
    Any glued method is going to be a lot better structurally and give more strenght per pound of used material.
    What I would recommend instead of silicon bronze? Epoxy, that's what. Research "strip planking" and "cold molding".
    Depending on vessel size and intended use, metal (either steel or aluminium) and reinforced fiberglass could also be an option.
    How big should the desired vessel be, what displacement, and where should it be used? Different materials and building methods make more sense in certain ranges and for certain uses.
     
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