Wood Choices for Cold Molding

Discussion in 'Boat Design' started by FastLearner?, Jul 16, 2006.

  1. FastLearner?
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    FastLearner? Junior Member

    Hello,

    I’m new to this forum and want to say hello and thank everyone for a very interesting and informative forum. I am new to boatbuilding (I’ve been thinking and reading about it for years but haven’t done anything about it yet) . I know I have a lot to learn yet but one day I would like to design and build a trailerable planing cabin cruiser for offshore fishing in so. cal. and Mexico waters, similar to a Blackman, Radon or Davis. In the mean time I have been reading a number of books about design, hydrostatics, stability, materials, etc. Anyway, recently I have been focusing on the materials/construction method I will use. I have been leaning toward cold molding, strip planking, or a combination of the two methods.

    Here’s my question: what woods are commonly used today for cold molding? Are thin marine plywoods used or are unlaminated (initially) veneers the preferred material? If the latter, where does one find veneers at a reasonable price? I have looked and have been unable to find any reasonably priced veneer thus far. Any help would be appreciated. Thanks in advance.
     
  2. frosh
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    frosh Senior Member

    Hi, first of all cold molding is rarely done now especially on anything bigger than a canoe. I have done a larger outrigger canoe by this method using 2 layers of 1.5mm marine ply and covering with one layer of carbon fabric and one layer of very light fibreglass fabric, all with epoxy.
    Having said that I would not recommend it generally for a first project (needs a fair amount of skill and experience), and for any project where you are only building one hull as the mold is quite a lot of work and cost. Also the whole process is very labour intensive hence slow going.
    If you want to go cold molding anyway, as strip planking requires a mold also, then use three layers of marine plywood, you decide the thickness depending on many factors. Then you won't need a structural sheething and can get away with a single layer of fibreglass to protect the timber and seal off the joins.
    Also if there are any concave sections (eg. in the bow region), cold molding is even more tricky than usual. :)
     
  3. FastLearner?
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    FastLearner? Junior Member

    Thanks for the reply, frosh. I'm surprised by your comment that cold molding is not used much anymore, as I thought I had read somewhere it is a popular method for one-off construction. Anyway, thanks again for the info.
     
  4. frosh
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    frosh Senior Member

    Fastlearner, If you want to use wood for boat construction, then you should decide first whether it will be round bilge or hard chine in shape. For a one off project, hard chine is easiest, cheapest and quickest, using sheet marine plywood.
    If you really want round bilge, then maybe sheet plywood for topsides and cedar strip for the bilges. Bottom could possibly be sheet ply as well.
    If you have any experience laminating with resin and fibreglass, you might consider using a core material such as divinycell, klegecell etc and fibreglass/ epoxy.
    It is well worth buying a plan, and following the designers exact instructions. There are very many traps for beginners, not only with material selection, and construction method, but also getting an efficient and safe hull shape that will work correctly. :)
    You will have enough challenge just following instructions and building, let alone designing as well. :cool:
     
  5. FastLearner?
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    FastLearner? Junior Member

    I don't need a rounded bilge but I do want flare in the bow portion of the top sides. For me, designing the boat myself is more than half the fun, so using stock plans isn’t an option. Thanks again for the feedback.
     
  6. Toot
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    Toot Senior Member

    I do a fair amount of custom composite work for cars and I've done a bit for planes, but none for boats. I'm sure I can answer your question to a degree, but first I need to know what the heck you all are talking about.

    What you mariners are calling "cold molding"... are you talking about wet layups around a reusable female mold with a foam or wood core in the middle? Or using a sacrificial mold (eg foam that you will later dissolve), or simply a "mold" which will later be included into the structure such as building with a foam core which will be glassed on both sides?
     
  7. Tad
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    Tad Boat Designer

    Cold-molding rarely done? Compared to what? I disagree.

    In North America and Western Europe cold-molding is generally seen as almost the highest quality building method. Because man hours are high, (fitting and bonding multiple layers of planking to supporting structure) it makes sense to use quality materials, thus creating high quality boats.

    Cold-molding generally refers to a hull skin made up of multiple (often diagonally opposing) layers of solid lumber/veneer or plywood, bonded with epoxy. This is usually sheathed outside and sometimes inside with fiberglass or dynel fabric. The combining of strip planking inner and cold-molded outer skins is often done in sailing yachts where the highest loads are longitudinal bending from the rig. All diagonal layers over a longitudinal structure is most popular for powerboat construction. This usually incorporates the engine beds as main longitudinal framing, with bulkheads as transverse members.

    A cold-molded structure can be light and stiff as all parts of the boat can be bonded together as structural members.

    Usual materials are Western Red Cedar, Atlantic White Cedar, Douglas Fir, and various mahoganies (African and Philippine). These woods all bond really well with epoxy. If you are building a cold-molded boat get a copy of the Gougeon Brothers Book, it's the best reference no matter who you buy epoxy from.

    All the best, Tad
     
  8. FastLearner?
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    FastLearner? Junior Member

    Tad, thank you for your reply. In your experience, for cold molding is plywood the most common choice these days, or is veneer still used a lot?

    I checked out your Web site and you have pictures of some beautiful boats!!!:!:
     
  9. wdnboatbuilder
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    wdnboatbuilder Senior Member

    Tad has put this subject to rest. very well said. in the boat that you see in my pics is 1/8" ply molded together. had to use to get the curve in the fwd end. light weight..........well maybe in bigger boats but not in small craft (12-21'). but sounds like these would be too small for what your looking for. Alot of your weight is going to be in the stringers not the skin. I can not say enough about the super structure that you have to contend with. the beefier the better for you and your crew. If it were me wood is the only way to go!
     
  10. frosh
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    frosh Senior Member

    Hi FastLearner, I don't mean to discourage you as boatbuilding is a fabulous enterprise, all the more so when constructed in wood BUT---
    If you are not about to embark right now on the design and then construction of the dream boat, then fine! You have a lot to learn first. The best way to learn is by reading, researching what others are doing, and then getting some experience by actually doing a project prior to the main one. Mistakes, poor quality due to inexperience and lack of skills are inevitable in the first try. Much better in the lead up project than in the real one!

    Tad is talking about very high end (read very expensive, deluxe boats by craftsmen) that are definitely not in a price range attainable by most of us, when saying that large boats are cold molded all the time.
    Wdnboatbuilder gives you a false sense of how easy it is by agreeing fully with Tad and also saying that you will be looking for a boat over 21ft, and implying that with due care to structural issues you should have no problems!

    My advice is simply, don't jump in too quickly as there is a lot of time and money involved, and without the requisite knowledge and experience it can all be easily wasted.
     
  11. Tad
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    Tad Boat Designer

    FL;

    Thanks for your kind comments.

    Most of the large cold-molded boats currently being built in the eastern US, lots of semi-custom sportfisherman, passenger catamarans, etc. are using plywood. Amateur builders and shops doing speedboats (Van Dam, etc) are using veneer or solid planks.

    The plywood covers area quickly, builds thickness quickly, and it's easily available at reasonable price. These guys use it in full sheets where they can, and cut it into wide (12-15") strips and layer it diagonally in areas of high or compound curvature. I'm not a cold-molded plywood fan, because you can't vacuum bag it unless you drill it full of holes. Also half the wood grain is running in the wrong direction and cut in little short pieces. These structural deficiencies are only obvious when you do panel testing of plywood vs solid wood.

    Veneer or solid wood cold-molding should be stronger, and properly engineered will be lighter for the same stiffness. People complain that veneers are hard to find currently, true, but they are available. Of course using 1/4" or 3/16" laminations means custom cutting which ups the cost.

    Properly engineered cold-molded construction can be light, and will be lighter than solid glass construction. But it won't be lighter than foam cored glass construction. But impact resistance will be much better.

    Frosh,

    I would always agree that building a dinghy first, then tackling a larger project would be recommended, but it's not absolutely necessary for someone who is methodical. If anyone comes to me and says " I want to design and build a boat", I'll say go to it.

    Arld is a retired gentleman living on the south coat of Norway, and he's building a boat. I'm sure he's built something before, (birdhouse, end table?) but never anything the size of a 28' heavy displacement double-ended motoryacht. She's built cold-molded using an inner layer of fore and aft strips on laminated ring frames covered with two diagonal layers of mahogany. He's about 5 years into the project, and just finishing the third layer of planking. I tried to convince him to build a simpler hull form, and I modified this one to take the reverse out of the garboard, but he insisted on building about the toughest, curviest shape imaginable. The workmanship is perfect in every detail. Go Arld!

    Tad
     
  12. FastLearner?
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    FastLearner? Junior Member

    Tad – thanks again for sharing the detailed information and your obviously very educated opinions about cold molding. You’ve answered my questions about ply vs. veneer/solid planking. Much appreciated!

    Frosh and others – thank you for your feedback as well. Your concern about me getting in too deep is a wise one. I do plan to build a couple of wooden boat projects (non-cold molded) before taking on the roughly 25’ fishing boat project I am just dreaming about now. I am reading a number of books on boat design and building, naval architecture, etc., including one devoted to the cold molding process. I also am reading the Gudgeon Bros book, which is excellent. I appreciate all your comments.

    Happy building.

    FL
     
  13. wdnboatbuilder
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    wdnboatbuilder Senior Member

    I'm not giving anyone hear any false assumptions on how easy anything in boatbuilding and designing a boat is. All I said is that the Gougeon Brothers Book is a good one and offers a hell of alot of information. If this guy does not pay close attention to the structure his boat ain't worth a **** in any kind of seas. I really don't apperciate you people putting words in my mouth. boatbuilding and design has a hell of alot more to do with than just super structures but where the f--k you going to put all the **** that you want in the boat and how it is going to handle that 7 or 12' wave your going to tske one day. if you feel i gave you a false sence then your stupid........frosh.
     
  14. frosh
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    frosh Senior Member

    Wdnboatbuilder, you are either having problems with the english language or being unjustly abusive, or both. Maybe a couple of courses at night school might help!:mad:
     

  15. FastLearner?
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    FastLearner? Junior Member

    I wanted some info on using ply versus veneer for cold molding. Tad answered my questions. Let's leave it at that. Thanks.
     
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