Fibreglass Hull Thickness

Discussion in 'Boat Design' started by LaMar Griffiths, Mar 18, 2020.

  1. LaMar Griffiths
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    LaMar Griffiths Junior Member

    So i am planning on building a 30foot fibreglass canoe. i plan to use woven and chopped strand in the laminate. how thick should the bottom of the hull be? is there like a standard relative to the length of the vessel? im thinking about 15mm should be fine for the bottom and around 9mm for the sides. do i need to use foam or is the raw laminate good enough. i am kinda new to this
     
  2. jehardiman
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    jehardiman Senior Member

  3. LaMar Griffiths
    Joined: Mar 2020
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    LaMar Griffiths Junior Member

    thanks alot ive had a look at this book already. just wanted to know if my thinkness was too much or too little
     
  4. LaMar Griffiths
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    LaMar Griffiths Junior Member

    not seeing a specific section with that info
     
  5. rwatson
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    rwatson Senior Member

    Just from the limited range of fibreglass boats I am familiar with, 15 mm seem to be on the heavy side..
    The thicknesses you are looking at are what Plywood would be, and Fibreglass is heavier as well as "stronger".

    Having some sort of "core", ( be it Plywood or Foam) is going to add a huge amount of "stiffness", without making it overly heavy or sacrificing "strength"

    The closest boat to a 30ft canoe from a professional designer in Polyester Resin, would probably be those done by Derek Kelsall or Rob Denney ( HarryProa)

    Personally, if you have the funds, investing in some professional help would be a great start, and may not be too expensive considering the overall cost of the project

    Edit:
    https://www.amazon.com/Elements-Boat-Strength-Builders-Designers-ebook/dp/B009SADJCY
    and
    McNaughtons Scantlings - fibreglass weight sheathed strip construction https://www.boatdesign.net/threads/mcnaughtons-scantlings-fibreglass-weight-sheathed-strip-construction.26181/
    may be of interest
     
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  6. bajansailor
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    bajansailor Marine Surveyor

    LaMar, are you designing this boat yourself, or have you purchased some plans?
    If it is your own design, can you post any pictures of your drawings or sketches so far?
    If it is a stock plan, can you tell us please which one it is?

    What are you planning on using this canoe for?
    How did you decide that it has to be 30' in length?
    Have you written up a Statement of Requirements regarding what you want this boat to be capable of doing?
     
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  7. gonzo
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    gonzo Senior Member

    It will depend on the shape, but we were building 30' canoes and the hull was about 4mm
     
  8. LaMar Griffiths
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    LaMar Griffiths Junior Member

    its actually a 28 foot fishing canoe my bad. my grand father has one and i wanted to replicate it by making the existing boat into a plug and making a mold out of it then use that mold to produce replica canoes. I am in Jamaica, thats an image of how the canoe looks. i just want an idea of how thick in terms of mm the bottom should be
     

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  9. TANSL
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    TANSL Senior Member

    4 mm seems little but, in any case, it is not serious to talk about thickness without taking into account the distribution, number and spacing of the reinforcements.
    LaMar, be careful with the tips that are given cheerfully. If your ship sinks, it will be your ship not the one of the "adviser".
     
  10. gonzo
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    gonzo Senior Member

    That's a Panga not a canoe. Also, what you are talking about is splashing (stealing someone's design). That is really badly seen in this forum.
     
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  11. bajansailor
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    bajansailor Marine Surveyor

    LaMar, is the vessel in your photo constructed of wood or fibreglass?
    Assuming that you do make a plug and mould from this vessel (but do take heed of the very relevant advice given by Gonzo above re 'splashing') , who / what is your intended market?
    Is this type of vessel very popular for fishing in Jamaica?
    Are you intending for sports or commercial fishermen to buy the boats that you build?
    Have you done any market research to see if local fishermen will actually want to buy one of your boats?
    This is an old traditional design - have you considered that there might now be other types of vessel that will be much more suitable / more efficient for the type of fishing that your customers will be doing?
    Be aware that this panga type of hull form (it looks like it might have a bit of Trinidadian pirogue influence as well) needs a big engine to perform properly (they are invariably pretty heavy beasts, unless you go really high tech on the consstruction re saving weight) - they were ideal in the days when petrol was cheap, but now it is very expensive (at least here it is - approx US$ 6 a gallon - is it less in Jamaica?)

    Oh, and it would be wise to remember this old joke -
    How do you make a small fortune from boatbuilding?
    You start off with a large fortune.
    Of course this does not apply to ALL boatbuilders, but many do seem to find out about it the hard way.

    PS - BY the way, there are a LOT of very similar boats to this impounded at our Coastguard station here (last I heard about 70 in total last year) - they were apprehended while doing drug smuggling sorties - and they will eventually be auctioned off in the not too distant future. Many will be virtually given away.
     
    Last edited: Mar 20, 2020
  12. ondarvr
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    ondarvr Senior Member

    The keel near the bow is frequently very thick on this type of boat because it’s being beached every day.

    The rest of the hull doesn’t need to be nearly as thick. But there’s no way to give an estimate on laminate thickness without a bit more info.
     
  13. bajansailor
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    bajansailor Marine Surveyor

    Lamar, did you see the questions which I asked in my last post above?
    The more info that you supply about your project, the better advice will be given to you in return.
    It sounds like you want to build these pangas more for sentimental reasons - however if pure practicality over rules the heart, then there are much better designs available now for fishing.
     
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  14. LaMar Griffiths
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    LaMar Griffiths Junior Member

    @bajansailor
    Is this type of vessel very popular for fishing in Jamaica? yes very they dominate the local fisheries apart from the big marina boats and tourist boats
    Are you intending for sports or commercial fishermen to buy the boats that you build? small scale Jamaican fisher man for their living
    Have you done any market research to see if local fishermen will actually want to buy one of your boats? yes they will definitely buy the,
    This is an old traditional design - have you considered that there might now be other types of vessel that will be much more suitable / more efficient for the type of fishing that your customers will be doing? yes but i belive they panga is what is in demand here
     
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  15. LaMar Griffiths
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    LaMar Griffiths Junior Member

    Pangas arent trademarked or anything here in jamaica. panga splashing is everywhere and i think with the right knowledge i can make better pangas. the designs are the ones that are available to the public. no one owns it per say so im not like taking anyone's design.
     
    rwatson likes this.
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