Help define process from concept-->build

Discussion in 'Boat Design' started by 1sailor, Apr 29, 2014.

  1. 1sailor
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    1sailor New Member

    I'm interested in a 20-24' project themed on the Wally 'nano' platform (36' techy modern pilot cutter) as a day sailor for my waterfront home and interested in a home build project (wood) as I have a large basement door and space to work.

    Questions:

    - the design already exists (but at 36')
    - is there a USA based CNC operator who I can hire to cut the panels and make this as easy as possible for me (first timer) so that it's basically an assembly project ? (I found one in australia online who claims to provide this)
    - how does one go from concept / idea what it looks like, to having someone with a CNC machine ready to hit the button ? Must I hire a yacht designer ? How detailed must the plans be ?

    I envision this having no motor, and a Melges 20 carbon mast and sails (which already exist in my basement) as it is light and stiff and available. Would need the project sized for this sail plan.

    Advice on direction from concept described above--->plans--->who can provide the build kit would be much appreciated !
     
  2. Skyak
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    Skyak Senior Member

    In the US there are many CNC gantries capable of cutting full size 4x8 sheets of plywood. Here is a site that helps locate them and 3D printing.

    http://www.100kgarages.com/profile.php?id=1333

    You seem to have an idea of what you want but no actual design yet -that might pose a bigger problem. There is plenty of good design help here if you can communicate what you want and need. For example, sail rigs are designed to righting moments. If you intend to use the Melges 20 rig your hull will need to be close to the righting moment of that boat. I suggest you start a thread on the sailboat forum "looking for a marine ply design for a melges 20 rig".
     
  3. Eric Sponberg
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    Eric Sponberg Senior Member

    1sailor--Welcome to the forum. What you want to do cannot be easily done with just merely scaling down the drawings. You may have to hire a naval architect to redesign the boat for you. Included in that would be the basic parts that would form the hull, deck, frames and bulkheads, and those all have to be resized to the smaller hull and smaller scantlings. You also have to be aware that while boat designs can scale up and down to some degree, human beings who use them do not scale, so you have to make sure that the new boat design is still comfortable and ergonomically fit to the human form. That's one of the things the designer does.

    In addition, the performance of the boat will depend on the new boat's displacement and sail plan, and as you suggest, a new sail plan will have to be drawn and matched to the hull and keel in the correct positions to guarantee performance. Note that as designs scale down, they lose stability--exponentially so--and that figures in to how the keel would be designed to the new form (you should not scale keels down the way the hull scales down, for the reason of the general loss of stability). So you need a new keel design as well as a new sail plan. That, too, requires the work of a naval architect or a skilled boat designer.

    As for cutting by CNC, there are any number of companies that can do that--a lot of lumber suppliers and woodworking shops have some CNC capability, so there might be some companies near you. One very well known company in the boat business is Chesapeake Light Craft in Annapolis, MD. John Harris, who owns the company, is generally pretty open about cutting other people's boat designs--you do have to pay him for the service.

    The patterns have to be designed and set up properly--you can't just give a CNC company a lines plan and expect to get patterns back. The designer has to create each individual pattern for every part to match the way the boat is going to be built--i.e. male or female, strip planked, plywood, fiberglass, etc. In male mold construction, for example, you have to know how thick the hull is going to be (and it may not be uniform thickness from keel to deck), and take that into account in the final shape of all the patterns. You also have to have a general plan, a drawing, of how to set the patterns up because they may not be equally spaced, nor are they necessarily set up to the same reference surface. So the designer has to provide you with that assembly drawing so that you can see how to do it.

    If you would like to see some examples of designing and making patterns, I have some stories about it on my website, which you can see here:

    http://www.sponbergyachtdesign.com/Patterns.htm

    I hope that helps.

    Eric
     
  4. 1sailor
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    1sailor New Member


    Loads of great advice here, thanks guys. Currently researching different build types. Based on the above criteria, what would be the easiest (least hours) for a home build project ? I've talked with a couple yacht designers now-- including the guy who designed the original 36' boat (Andre Hoek), but I have some sticker shock @ $15k (euro) to do this.... so I'm interested in ideas there as well....
     
  5. TANSL
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    TANSL Senior Member

    1sailor, I am not a designer of sailing boats (I designed pleasure motor boats and workboats) so, for the design part, but I have my opinion, I will not expose it. But the definition of parts, CNC, assembly drawings, all construction drawings of the hull and build strategy, can assure you that the price is very, very, below the amounts they are giving you.
     
  6. 1sailor
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    1sailor New Member

    Agreed. Mr. Hoek spends his day designing 60-200' luxury megayachts (sail) so this is probably looked at as a tedious 'heist' of one of his designs and probably not his biggest project of the year, and priced accordingly :)
     
  7. Eric Sponberg
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    Eric Sponberg Senior Member

    1sailor, Probably the quickest and cheapest method of construction is some form of plywood/wood-epoxy construction. I recommend that you download the Gougeon Brothers Book on Wood-Epoxy construction. It describes a number of different methods of plywood and wood-epoxy construction as well as gives advice on pricing out the build. You can download it from the Gougeon Brothers website, here--(it's great that this book is free, they used to charge for it):

    http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook 061205.pdf

    As for design prices, this would have to be a custom design, taking the elements of the Wally boat that you like and incorporating them into a design to your liking in the method of construction that you prefer. From a name designer you can expect to pay about $1000 per foot, so expect a design fee in the US$20,000-US$24,000 range. Mind you, you get a lot for that--a complete boat design that works--with complete patterns and details, no guesswork.

    Eric
     
  8. daiquiri
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    daiquiri Engineering and Design

    Yes, you can actually buy a new 22ft production sailboat for that price. But you are looking for a one-off, and that's where your pain comes from. It takes a lots of work to do all the math and scantlings and to create all the drawings and accompanying documentation. In case of production boats, manufactured in big numbers, the design cost per-boat is obviously much smaller. In case of one-offs, the design work and costs remain the same, and the whole burden lays on just one boat.
    However, the actual cost will vary depending on the designer you contact. Some have big design studios with big fixed costs, some have much smaller-sized studios and expenses, and some others are a one-man-show who work at a slower pace but also have much lower expenses. The fact that the latter two are much smaller doesn't mean that the quality of their work is lower. Quite the contrary is often true, actually. So, my advice is to ask for offers from different designers before taking your decision.
    Cheers
     
  9. Skyak
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    Skyak Senior Member

    I assumed you were asking about stitch and glue CNC cut marine ply which is the most cost effective IMHO. I think Eric was talking about strip plank which can cost about the same if you have a cheap supply of suitable wood and do your own milling -it's much more work but the finished product is no compromise (no chines). Cold molded wood is worth mentioning but it is not easy one-off. The mold takes too much work.

    Synthetic cores cost more and generally take more glass but they are easy to work and are compatible with cheaper resins. Some people value synthetic core over wood for resale but they cost more to build because wood takes more load than synthetic core.

    Looking at the Wally Nano, I would say that strip plank is your best bet. Looks are a large part of the function of that boat. Without the elegant curves you wouldn't love it. Be honest, isn't part of the attraction that it looks expensive?

    I have a concept for how to replicate wonderful old sail boat designs cheaply but it won't make a high performance 'neo-classic' like the Wally with all it's weight deep in the bulb.
     
  10. daiquiri
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    daiquiri Engineering and Design

    I agree with that. Just please change that transom gunnels of Wally Nano which makes it look like a halloween jack-o'-lantern from behind.
    [​IMG]
    And please, please don't paint it pink. :rolleyes:
     
  11. Skyak
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    Skyak Senior Member

    When I posted this the thread had been open on my PC quite a while and didn't have all the good posts from great sources. Sorry for the redundant comments.

    I have a question for the thread now they have all looked at the Wally Nano. The long overhang and angle of the overhang imply a waterline length related speed to me. My thought is that light weight high ballast ratio construction will not make this a speedy boat. This boat will hit the same wall of drag that limits the classic boats it mimics (just in lighter wind) and settle at a Fn a little higher than the classic. Am I way off here?

    Now the OP has a high performance rig from another boat he wants to use. That means that the righting moment is defined and limited by the rig. But righting moment was the only advantage of the neo-classic based on the logic above. Therefore if I can make the hull form of the classic, with it's center of gravity and buoyancy cheaply (lower cost/ton) it will match the performance of the classic (better with modern sails) and be very near the performance of the expensive neo-classic. And it will likely 'rate' better.

    http://www.wally.com/nano/
     
  12. Eric Sponberg
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    Eric Sponberg Senior Member

    Skyak, The Wally Nano has huge amounts of sail area for its weight (SA/Vol^2/3 = 40.32) which is more than twice most other conventional sailboats. It is also light for its length (Displ/(.01Lwl)^3 = 117.32) classifying her almost as an ultralight. Plus she has hardly any underbody with the blade keel, so wetted surface is at a minimum. This boat is a very fast light air sailer, and that is what she is meant to be, advertised as a daysailer. Like any displacement boat, she will behave according to Froude's law when it comes to the upper speeds, and for that she should do better than most because her length-beam ratio is generous, 4.35/1, whereas the vast majority of comparable boats are less than 4.0. As a result, she may easily exceed "hull speed" by a bit. She compromises waterline length for style, but I bet when she heels over, she picks up some waterline length to make up for it.

    By having a rig already, the trick of the designer will be to match the hull design to the rig as closely as possible. I would not say that the "righting moment is defined and limited by the rig." The righting moment will be what it will be, the rig is what it is, and the two will work in concert, the only other independent variable being the wind speed. The righting moment is not the only advantage of the neo-classic, as described above, there are those other factors that define performance.

    If you make a fully classic hull with a conventional keel (which is what I would expect of a fully classic design) to the same waterline length and beam, chances are your displacement and wetted surface are going to be greater on both counts, and so you'll be slower both in light air and possibly heavy air. To lower displacement and wetted area, you'll have to change the design to be more in line with the Wally Nano--shallow canoe body and skinny blade keel with a bulb. Then you'll have comparable performance.

    Eric
     
  13. Skyak
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    Skyak Senior Member

    Eric,
    that is pretty much what I expected. The big sail area advantage rules the light wind performance but the advantage dwindles as the boats run into hull speed wave drag. About the keel and rudder, what I had in mind was modern profile and high aspect like the Wally but sized in proportion to the smaller sail area. My concept would still match the beamier classic hull shape so still slightly more wetted area. My technique could exactly match the old keel designs but the idea here is a better priced neoclassic to compare to the Wally. No sense having old foils below the water if you are modern above.

    The thing that was squishy in your comments was the existing rig. If you are going to use it with the same safety factors it must have the same load limits, which to me means the righting will be the same if the distance to the roll center is the same (a pretty reasonable assumption). Am I missing something?

    The last question is a little tougher. How would my neoclassic boat rate vs the larger sail area and righting of the Wally? My thought is that mine would have an advantage on corrected time in all but very light wind conditions.
     
  14. Eric Sponberg
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    Eric Sponberg Senior Member

    Skyak, The OP said that he wants a 20'-24' boat for which he could use the Melges 20 rig. So you are already talking about two boats of similar length, probably displacement, perhaps righting moment, it's just that he is saving money by using an existing rig. So he has a good starting point for the new design--he doesn't like the Melges 20 look, he likes the Wally Nano look. The Melges 20 and the new boat may perform the same--it depends on all the design factors, including beam and placement of crew weight on such a small boat. It doesn't really matter where you start in the design--in this case with the rig--you'll end up with a boat of a certain performance for its size. A clever designer may make the boat faster than the Melges 20 by judicious choice of hull and appendage design and lightweight construction. But I think that is beside the point. I think the OP is going for a nifty look and low-cost construction and getting a reasonable ride.

    As for your other boat idea--First, what do you mean by a "classic design"--are you talking boats of the 1980s, 1960s, 1940s, 1920s, or earlier? What are the basic design parameters? Is this new boat going to be the same length and weight as the Wally Nano? Are the major differences going to be in sail area (if yours is less, you will be slower), or beam and wetted area (if yours are more, you will be slower). How will it rate? Who knows? What rating system would you use? For boats of the same length, sail area, and weight, they should rate the similarly. Those are the major design inputs that control performance. After that, everything else is garnishings, including crew talent--how good a sailor are you? A good sailor can make a bad boat go fast, and a lousy sailor can make a good boat go slow.

    Remember, too, that lots of boat races are sailed in light to moderate air where hull speed (waterline length) does not come into question per se when you are talking about boats of similar length to begin with--rather weight, stability, and wetted surface are dominant factors. With increasing wind comes increasing waves, and all boats slow down in waves. Again, hull speed does not enter into things for boats of similar length. Narrower boats fare better in waves than fatter boats.

    So, if you have a neo-classically styled boat that is similar in length and weight to the Wally Nano, and it has similar appendages, but the Wally Nano has more sail area, a narrower hull form, but more stability (less form stability but more weight stability), the Nano is going to beat you just based on those design parameters. Your boat will rate higher because it will be potentially slower.

    Eric
     

  15. TANSL
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    TANSL Senior Member

    At the risk of someone bite me in the jugular, I´d like to give my opinion: the amount of computation that takes a boat, between 12 and 25 m is almost the same. Most calculations do not depend on the length. So do not understand that the price of a project is directly proportional to its length. This would lead, exaggerating the issue, the designer try to do, for the same displacement, the vessel of greater length possible. I know it is absurd and I'm oversimplifying, but why not think badly from time to time?
    Seriously, do you really think the price is a direct ratio of the length???
    What people are saying out there?
    I may be totally wrong, therefore greatly appreciate clarification.
    Thanks
     
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