How to make a hull in epoxy and fiberglass only from a mold — no vacuum

Discussion in 'Fiberglass and Composite Boat Building' started by Space, Mar 28, 2024.

  1. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    Hi,

    I have a good female mold I can use to make a 19 feet long hull (mono-hull).
    This mold is normally used to make fiberglass and polyester resin only hulls.
    To make it stronger and durable I want to make it in epoxy and fiberglass only.

    Believe it or not I can’t find any resources to help me doing it this way!
    I can find only resources about how to build with polyester or wood covered with epoxy and fiberglass.
    Any help is therefore much appreciated on this project.

    The boat must be strong enough to survive any storm, hurricane, rogue waves, capsizings…
    It will be a sailboat that will sails all oceans. Of course a deck will be add also in fiberglass & epoxy and the shape & ballasts will make it self-righting.

    I will build it the simple way: no sandwich construction, no vacuum infusion technique.
    I just want to lay down sheets of fiberglass and laminate epoxy with a paint / metal roller on it.
    The boat hull may just be a layer for the hull and reinforcements beams also in fiberglass & epoxy in square shapes.
    This beams shape are named «hat stiffener with hollow former» on this page: Fishing boat construction: 2 Building a fibreglass fishing boat https://www.fao.org/3/t0530e/T0530E08.htm

    This is all I know!

    Therefore I have several questions. Such as:
    — How many layers of fiber glass should I use? I heard only 3 is enough is it correct?
    — Advice about how to lay them down? I heard that I should lay down first a layer of bi-axial in X then on in +), but I guess there may be need for patches on some places to reinforce the hull…
    — Advice about reinforcements of the hull such as kevlar bands? Where and what size?
    — What kind of fiberglass can I use (so far I can’t find the 1708 & 1808 bi-axial + mat here in Asia).
    — What epoxy can I use? I can’t find an epoxy for such simple use. I only find fancy modified ones (such as one that can cure in cold climates), for smalls repairs (I need at least 350kg of epoxy), vacuum, or oven curing, with not enough details for be convinced in the product.
    If someone could tell me a «normal» epoxy name, or with what it is made of I guess it will be easier to find the h product.
    By the way I heard that all brand actually use the same base epoxy from china coming in batches; then they sell it with a curing agent that is their own formulae. Is it true?

    Thanks.
     
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  2. Blueknarr
    Joined: Aug 2017
    Posts: 1,451
    Likes: 414, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    Welcome to the forum

    I hate to burst your bubble
    BUT
    No 19ft vessel is appropriate for "all oceans ". It may survive a hurricane in tack but it's occupants won't.

    If you proceed
    Simply replace poly with epoxy. Use the same scheme of fg cloth. There is very little difference in application techniques. It will be more expensive but slightly stronger.

    Some epoxy brands are relabels from the same manufacturer. BUT not all are! The base and hardener MUST be chemically compatible. Look up "marine epoxy " to see common brands and formulations appropriate for boat building.
     
  3. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    Thank you for your answer.

    By the way what hull size is fit for all oceans?
    Where do you think a 19 feet hull is not enough?
     
    Last edited: Mar 28, 2024
  4. bajansailor
    Joined: Oct 2007
    Posts: 3,609
    Likes: 1,571, Points: 113, Legacy Rep: 37
    Location: Barbados

    bajansailor Marine Surveyor

    @Space Blueknarr has summed it up very well for you above.

    Do you have any photos that you can post of your mould?
    Have you drawn any sketches showing what your sailboat will look like?
    If you have, can you post copies of them here as well please?

    Be aware that for the cost of the basic materials (epoxy, fibreglass mat, timber, rig and sails, outfit items etc) it will be much cheaper and easier to buy a second-hand sailing boat of a proven design that is 'ready to go'.
    And you can probably buy a nice sailing boat that is much bigger than 19' long - giving you more space and comfort, and more speed (as the longer a boat is generally, the faster the average cruising speed).
     
  5. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    I know I’m also looking for second hand boats.
    I see lots of them in Europe but I can’t find in Asia a cheap one.

    About the design of my sailboat I have no questions.
    This hull mold make boats that goes on the sea.
    And anyway recently a French guy made a round the world trip with a 4m long scow bow.
    As i read: «any sailboat can make a round the world trip as long as there is a cabin on it ».
    I just have technical questions.

    Let’s add one more:
    Epoxy need to be covered on with a paint that protect it from UV.
    It seems that there is only 2 kind of paints for this job: polyurethane either in one components or in 2 components.
    I read that it is hard to renew the paint of a 2 components polyurethane paint: what’s actually the problem? This is not clear.

    Actually I wish I can get answer anyway for the questions i already ask because for example fiberglass is not the same if you work with epoxy or polyethylene resin. Lasts one have a product I don’t remember its name that make it unsuitable for being used with epoxy… but still I find online shops that look serious who say that their fiberglass can be use for polyester or epoxy…
    How to trust them then!

    Thanks.
     
  6. wet feet
    Joined: Nov 2004
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    Location: East Anglia,England

    wet feet Senior Member

    I suggest you buy a plane ticket to Europe with 5-6 thousand dollars or equivalent and look around for a few days.You will almost certainly find a boat that will be adequate and you will be a lot of money and time ahead of where you might be should you decide to try building something.How does your sailing experience compare to your boatbuilding experience?
     
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  7. Blueknarr
    Joined: Aug 2017
    Posts: 1,451
    Likes: 414, Points: 83
    Location: Colorado

    Blueknarr Senior Member

    In my estimation
    1
    Anyone asking about minimum length to safely use on any ocean does not have sufficient experience to operate a vessel on any ocean.
    2
    If you can't afford a used boat then you can't afford to build one.

    Epoxy usually has longer working pot lives than poly. Wetting out and laying cloth is essential the same for epoxy and poly. Exotic cloth (carbon/Kevlar) is epoxy only. Standard woven s and e glass is epoxy/ poly. Most Matt is epoxy compatible but some is poly only.
     
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  8. kapnD
    Joined: Jan 2003
    Posts: 1,301
    Likes: 414, Points: 83, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    You might consider vinylester resin.
    It performs much like polyester, but is much stronger, while significantly cheaper than epoxy.
    If you are contemplating long sea voyages, 19’ will be a painfully minimal length for a seagoing vessel.
    Certainly it has been done, but not comfortably, as you will be tossed about by each and every chop, and launched off every swell! Increasing Waterline length smoothes out the ocean considerably.
    IMO Real comfort at sea will not happen until waterline is in the mid 70’s!
     
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  9. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    I’m not sure to follow you when you say (~22m) «waterline length». Do you speak about the length of the boat from stern to bow or the part of the hull under the waterline?
    In both case indeed then there is no need to speak about comfort for most cruisers at all then, and I’m good with my 19 feet long hull!

    But here is an interesting idea: how high should be the hull to sails the seas? (for an same length bow to stern & same width port to starboard).

    Anyway I wasn’t concern about comfort.
    My concern here is to make a boat that won’t break apart in the middle of the sea.
    Therefore epoxy & fiberglass.

    It seems that the beams I plan to use are enough: actually I wish to hear someone who can confirm it.
    If I have to make it stronger than that I will. If not I won’t and save useful area inside the boat.

    About the 19 feet being too small as I said where in the world do it make a problem?
    Atlantic: no problem.
    Pacific: no problem.
    Cap Horn: I would go on the strait of Magellan instead.
    Indian ocean: where is it a problem? and why?
    North and south pole: where is it a problem? and why?
    Other places?

    Now to be constructive I also have this question:
    Obviously the standard length of boats depend on the average spacing between waves for each oceans.
    I couldn’t find this data: what is the average spacing between waves for each oceans?

    Thanks.
     
  10. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    @Space a polite suggestion for your own future safety and sanity - after reading your last post above, please do not think about building a boat.

    Go and find yourself a little sailing boat somewhere - there are bound to be some in Asia (whereabouts in Asia are you?) - and learn how to sail it.
    Or (even better) - go on a 1 week sailing course first at a school somewhere before buying a boat - you will learn a heck of a lot in that week, including about what not to do when it comes to making plans to cross oceans in little boats with no experience.
     
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  11. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    Also between two layers of epoxy it is not clear what to do.
    Some says we can laminate more fiberglass as long as the first layer is not set yet.
    Some says it is better to wait for the first layer to set before laying a new one of top of it.

    On the other hand some says we have to sand the layer of epoxy before laying a new layer of fiberglass and epoxy.
    But they don’t say how to clean it before laying a new layer on it.
    And some seems to say we can use a product — I think it is acetone which sound doubtful to me — instead of sanding or in addition to sending for the new layer of epoxy to adhere to the previous one.

    What is the right procedure with epoxy to laminate many layers?
     
  12. C. Dog
    Joined: May 2022
    Posts: 98
    Likes: 34, Points: 18
    Location: Coffs Harbour NSW Australia

    C. Dog Junior Member

    @Space please listen to industry experts, you clearly have no experience of offshore boating and it is no place for an inexperienced person with grandiose schemes. The Kiwi designer John Welsford specialises in producing plans for minimalist sailboats for coastal and offshore voyaging. It is far more than length that makes a boat fit for purpose.
    Home - JW Boat Designs https://jwboatdesigns.co.nz
     
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  13. Space
    Joined: Mar 2024
    Posts: 6
    Likes: 1, Points: 3
    Location: Asia

    Space Junior Member

    Any rational person here who can stick to what I say instead of raving in their own delirium?
     
  14. C. Dog
    Joined: May 2022
    Posts: 98
    Likes: 34, Points: 18
    Location: Coffs Harbour NSW Australia

    C. Dog Junior Member

    This is where I disengage, not willing to listen to reason, becoming abusive.
     

  15. seasquirt
    Joined: Dec 2015
    Posts: 122
    Likes: 55, Points: 28, Legacy Rep: 10
    Location: South Australia

    seasquirt Senior Member

    Hi Space, so you've got yourself a mold for a "19 foot long boat". May we see photos of the mold, or of one of the boats it has produced please. Does that boat/mold model have a name, or model number, so we can search for photos ?
    Your questions reveal you know very little about boats and the sea. Have you been inspired by a movie, or story, to 'go to sea' ? Or you got the mold cheap and just want to use it ?

    You said: " I’m not sure to follow you when you say (~22m) «waterline length». Do you speak about the length of the boat from stern to bow or the part of the hull under the waterline?"

    You need to understand about waterline length, it's one of the absolute basics. Read some books, or at least look up boat terminology. Get some practical training from a course.

    You said: "In both case indeed then there is no need to speak about comfort for most cruisers at all then, and I’m good with my 19 feet long hull!"

    In tropical heat, icy winds, and rough conditions, or if injured, sick, or fatigued you will really appreciate comfort. Bigger means more room for more contingency supplies, just in case.

    You said: "But here is an interesting idea: how high should be the hull to sails the seas? (for an same length bow to stern & same width port to starboard)."

    Not exactly sure what you're saying there. Does the mold have two halves which bolt together, or a one piece, forming a bottom and two sides, with a certain height from the chines to the gunnels ? Look up those words.

    You said: "My concern here is to make a boat that won’t break apart in the middle of the sea."

    The boat may end up good and "sea worthy", but you yourself may break up while making it if you don't listen to experts in the various fields. There are many unfinished boats and broken marriages resulting from lack of knowledge and finances when boat building.

    The more information you can give to us, and comprehension of what people are telling you, the more we can help you. Use the search feature on this site to look up other people's questions already answered. If an engineer or marine surveyor or naval architect or any other expert tells you some information, you'd better believe them, and disregard knowledge at your peril. Building a hull is the first and cheapest part, and bigger problems will come in time as the build progresses. That's why it's cheaper to buy a going concern already built.
    Think about engaging a boatyard to use your mold to make your hull for you, while you concentrate on the following stages of fit out, decking, rigging, and the many other components.
    Try being a deck crew on a commercial boat; you may be cured of boat fever forever and sell the mold. Maybe study for a coxswain's certificate, to gain some relevant skills.

    Best of luck Space, I hope all goes well and you succeed in your endeavor.
     
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