Thoughts/options for a 14’

Discussion in 'Boatbuilding' started by PROPGUNONE, Jun 19, 2018.

  1. PROPGUNONE
    Joined: Jun 2018
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    PROPGUNONE Junior Member

    Deep in the design process of what will become a pretty cool and unique 14’ skiff. Footprint will be somewhere around 14’ x 54”. I’m certain there’s at least a small market for this thing, and I’d like to produce a minimum of 5-10 of them. Built a couple of S&G boats in the past, but the build limitations of that method and the fact that I want a fully composite, uniquely designed boat that I own all the rights to prevents me from going that way again.

    So the question is this: Do I build a one-off, cold molded hull (and deck), then later use that hull as the plug for a mold, or am I better off going straight to the plug-making phase and getting a mold off of it? The plug could be a simple MDF/foam combo with whatever filler I decide to use and duracoated. At a bare minimum three of these will be produced. Max... who knows.

    Just looking for the opinions of the much more experienced here. Think HB Skate as a very rough, general idea of the look.
     
  2. Skyak
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    Skyak Senior Member

    The only reason I can think of for building a cold mold boat before making the plug is to see how it works as a cold mold boat. Building the boat is certain to bring lots of real world limitations and imperfections to your concept.

    Do you know exactly what you want? If you do then there are much better options for producing the molds. 4'X8' lightweight CNC machines are abundant these days -they would be happy to cut you plugs out of foam. If you are more comfortable hands-on you could shape half the hull and cut the other side with a mirroring mechanism.
     
  3. PROPGUNONE
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    PROPGUNONE Junior Member

    We’ll know exactly what it will be once the drafting is done. Still working on details of it. Is it pretty common practice to use smaller CNC units to break the hull into ‘sections’ and then dowel them back together to create the entire plug? That was my thinking on it but having not produced anything CNC before I wasn’t sure if that was a standard practice.
     
  4. Mr Efficiency
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    Mr Efficiency Senior Member

    You are better off building the prototype, as a working test bed, to establish that you have something that has an "edge" over other boats of the type. You may go to the triple trouble of making a plug, a mould, then a boat, only to find it disappoints in some way you did not anticipate. You might want to make a small alteration to the prototype, and re-test, but if you have already gone to a mould, alterations will be much more difficult.
     
  5. Skyak
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    Skyak Senior Member

    The blanks must fit together on a perfectly flat plane before cutting. The machinist will cut them so the sides you fit together go together after cutting. You should put some reference features out past the edge of your mold that get cut first and checked before running through. The cutting should be to some fraction of a millimeter but it's just foam. My comment was just about resources. You could find someone that can do the whole boat in one pass but I wouldn't expect any bargains.
     
  6. Skyak
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    Skyak Senior Member

    Building a boat would help you learn about performance and maybe the market, and give you lots of time to be talked out of investing in molds.
     
  7. PROPGUNONE
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    PROPGUNONE Junior Member

    The catch to all this is I have a boating cousin who happens to run CNC machines for a living. His primary machine is something like 2x2 but with the equipment distributors he goes through he can find companies that own bigger units which he’ll then run. Only real expense then would be foam and whatever the owner of the machine wants for the time, not paying actual machining costs.

    Something I’m confused on though... I hear people talk a lot about the cost of a mold, but materials-wise there doesn’t seem to be that much in it on a smaller boat like this. I understand why the mold for a 52’ sportfish could easily hit tens of thousands (or more), but why such a high price for smaller vessels?
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    For ease of use (being able to tilt easily, e.g.), durability, staying true to shape, not twisting etc, moulds (or molds, the USA spelling !) need to be properly made, and it only makes sense to make that investment if you are very confident you have a good product. It make sense to make a boat first, at least the hull, that way the grief will be less if it turns out not such a great boat.
     
  9. jorgepease
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    jorgepease Senior Member

    A plug that small can be cut with CNC hot-wire out of blocks of foam very fast and inexpensive but then you still have to do all that fairing ... I would just go direct to female cnc. Use thin bendy ply to create 1/2 the boat, the final surface can be cabinet laminate, no fairing!!! ... make both half sides so the keel is the seam which stands a little proud to make it easy fair after you infuse in one shot. I'd use in-mold primer as well.
     
  10. gonzo
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    gonzo Senior Member

    Building a mold for a boat that has not been prototyped is a bad idea. You won't have any idea of how it behaves. The cost of the molds is not just the hull, but the liner, deck cap, etc. The hull is often the cheaper mold because it is simpler.
     
  11. Tink
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    Tink Junior Member

    Don’t build a mould, fabricate a prototype anyway you can and test learn, start again until you get what you want. A prototype has to have very little value to be truly useful. You will invest so much time in the plug and mould even if you are only 50% happy with the design you will keep it. I have been down the mould route it is long, painful and of little real use.
     
  12. PROPGUNONE
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    PROPGUNONE Junior Member

    Seems like most people are on board with one-offing the boat and molding later. I do have very high confidence in the quality of the design, which is still being finished up. Any changes would likely be minor, but I get the point. Still waiting to talk it over with the guy drawing it up as he’s unreachable at the moment, but it’s looking like finished boat first, then molds.
     
  13. SamSam
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    SamSam Senior Member

    When I was buying materials a few feet and a few gallons at a time from a canoe mfg company, they had a designer that would start in the morning on a prototype and be on the water that afternoon to test it. He would start with spaced station forms of his theoretical shape, air nail wood strips to it, glass it over, let it set up, throw it in the water, forms and all, and paddle around. If it wasn't right, he would either modify what he had (if he could) and try that, or throw it away and do it again with his new ideas incorporated. Canoes are all complex compound curves so he put out very sophisticated shapes PFQ. Your boat isn't much bigger as far as expense of materials and all, the big difference is yours will be powered, so you have to account for the different loads on the boat from the motor itself and from the heavier loads of the water (slamming etc) from being driven faster.
    Is your 'designer' going to come up with your lamination schedule and all the required building methods and materials also? Your small boat will (should/can) rely on the inner liner to supply a lot of the strength and reinforcement of the hull, so 'designing' the boat adds up to more than only drawing the shape, it needs to be engineered too.
    You want the shape and approximate weight to test the shape of the hull and how it performs on the water, but things such as bait tanks, fuel, seats etc might have to be moved around for balance etc.
    Another thing is by building boats you will be creating legal and financial responsibilities and liabilities that could put everything you have at risk, so you might want to investigate that aspect.
    Also, molds and materials and construction take up a lot of work and storage space, more than you might think, so there is that.
     

  14. PROPGUNONE
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    PROPGUNONE Junior Member

    Space I have, and this guy has designed (and built) hundreds if not thousands of boats, so he knows his stuff way more than I do. Far more than just a drawing of a boat for sure. That I could do myself.
     
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