Newby questions on sailboat design

Discussion in 'Boat Design' started by Kent Multer, May 25, 2010.

  1. Kent Multer
    Joined: May 2010
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    Kent Multer Junior Member

    Hi folks --

    I'm brand-new here. I've been toying with ideas for a sailboat design, and now I'm looking for basic resources.

    I currently sail a Beachcomber 25 which had no rig at all when I bought her. I designed and built my own, and I'm very happy with the result. I do have odd preferences, but I'm good with tools, and with numbers. So I'm looking into designing and building a hull.

    Right now I'm looking for good books and/or software to help me answer the tough questions, mostly about stability and ballast. I've done some browsing around these forums, and I did find a link to Gerr's "The Nature of Boats," which I'll be ordering. I know there are some free or inexpensive software packages for boat design, but I could use some advice on which ones to get.

    Some more about my boat ideas:

    The Beachcomber floats in 15 inches of water with her centerboard and rudder up. I like shallow draft -- yes, another sharpie fan here! -- and I like the Chinese rig with no jibs. I've been reading about Phil Bolger's "box" boats, and I'm thinking of something along the lines of his "Loose Moose," with curves only at the ends, and the midsection all straight lines and 90-degree angles. I need a design that's easy to build; plywood stitch-and-glue suits me fine.

    One constraint -- maybe the thing that's driving me to try designing my own -- is that I'm tall, 6'3" (187cm). I want to see how far I can push the limits of high-sidedness, in order to maximize headroom, while still having decent performance in "normal" sailing conditions. I have no plans to win races or cross oceans, so I can tolerate some loss of upwind ability in high winds.

    I've even sketched a 32-foot "sailing houseboat" with almost 7ft. of headroom in a 16ft. cabin. Re-using my sail design from the Beachcomber, I can get almost 400 sq. ft. of sail on her with masts only 26ft. tall. So it seems feasible; but I need to know for sure.

    Where do I go from here? Be gentle, it's my first time :^) . Thanks --
     
  2. messabout
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    messabout Senior Member

    Bolger had a design called Big and Tall. specifically designed for tall folks.
     
  3. Kent Multer
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    Kent Multer Junior Member

    I've read several of Bolger's books, but I've never heard of that design, unless you're thinking of "Whalewatcher" which was sort of an expanded version of his "Birdwatcher," created specifically for a tall client. Can you give me a link, title of a book, etc.?

    Thanks --
     
  4. messabout
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    messabout Senior Member

    Big and Tall was one of his drawings that he called "cartoons". The cartoon appeared in the now defunct Small Boat Journal magazine. That particular boat was a design he did for a very tall man and his equally tall son.

    Bolger reckoned that a small boat has limits for cabin height. He just split the cabin down the middle with an opening wide enough for a tall person to walk, unimpeded, from transom to stem head. The mast was offset at the front of the cabin and housed in a tabernacle. Some of his ideas were out of the mainstream, of course, but most of them worked and worked well.

    I first got aquainted with the Bolger concepts back in the 80s. I chartered a Black Skimmer, sight unseen, out of the Florida Keys. The Skimmer had flooded compartments fore and aft. I thought that feature to be a patent absurdity until I lived with it a few days. Instead of absurd it turned out to be brilliant. So much for my pre-concieved notions. That boat at first glance, with its sprit boomed yawl rig, seemed primitive. Not the stuff of a hot shot racer type like me. It soon became apparent that the old fashioned rig had much to recommend it. It turned out that I fell in love with what, at first, appeared to be a cornpone boat.. Attitudes change.
     
  5. Kent Multer
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    Kent Multer Junior Member

    Hi, thanks for the info. The split-cabin design is what Bolger used on the Birdwatcher and Whalewatcher designs, so I'm familiar with that. It's a very clever idea, but I'm looking for a design with long-term-cruise or liveaboard potential. I want to be able to stand up even when the hatches are closed in bad weather, or to keep out the bugs at night.

    I do like Bolger's unconventional approach. I agree that older types of boats have a lot of great qualities. Modern recreational sailboats are all built and rigged like racers, because that's what sells; most Americans want to sail something that looks like an America's Cup winner. Boxy workboat designs with low-aspect sails are often more comfortable and easier to sail. And moving a mast a bit off the centerline can be a tremendous help with interior layout. (All that IMHO, of course ...)

    I found the forum page on low-cost software. I looked at a few packages, and Boat Express looks like it will do what I need. Other than that, and "The Nature of Boats," are there any other resources you'd recommend?

    Thanks --
     
  6. marshmat
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    marshmat Senior Member

    Hi Kent,

    For additional inspiration, given what you've said so far, I'd suggest taking a look at George Buehler's designs.

    From what you've said so far, it sounds like you might be the type who would enjoy the design process and would be willing to put in the time and effort to learn how to do it properly. This is key: learning an engineering discipline is a long, tedious process that calls for determination and clear-mindedness.

    You will need at least a few technical references; "The Nature of Boats" is a good book, but it's not a design manual. Larsson/Eliasson "Principles of Yacht Design" does a nice job of covering the engineering that goes into a sailboat design. Gerr's "Elements of Boat Strength" covers construction methods and presents a rough, conservative way of estimating appropriate scantlings. You'll find many more suggestions as you go.

    Be very, very careful on the CAD software issue. A computer is a tool, nothing more. Its job is to automate certain parts of the design process that would otherwise be tedious, and it can do that very well, but it is equally capable of spitting out pretty pictures and data tables that describe a dangerous, ungainly pig of a boat. The computer is only as good as the data you put into it; you have to know what you're doing and what all those numbers mean BEFORE you start messing around with CAD.

    I think your junk-rigged Beachcomber is quite clever, and actually a rather elegant rig....
     
  7. Kent Multer
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    Kent Multer Junior Member

    Hi Matt --thanks for all the info & advice.

    I did have a look at Buehler's site, and a couple of his designs are similar to what I have in mind. I wrote to him, and he was kind enough to answer some questions. I'll be getting a copy of his book.

    I do have an engineering background, and boat design is something I've been reading and thinking about for years, just for fun; now I'm getting more serious. I expect to use software, not just to draw pictures, but also to do the math on stability and performance, and maybe scantlings, to make sure that I end up with a boat that's safe and fun to sail.

    Glad you like my rig! It does work quite well, and was easy to make; I spent more money at Home Depot than the boat shop :^) .
     
  8. stubby
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    stubby Junior Member

    I would say stay away from the boxy design. If you look at John Welsfords designs they have very nice lines and are designed for the amateur builder. So take the time to design a boat with nice curves ect and then take the time to build it and you will get a great result. It also means you will get more people come to talk to you. My dad built a Penobscot 14 very classic looking boat but easy to build but the launching time is extended by 30minutes because of all the people who come to ask about it.
     
  9. Kent Multer
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    Kent Multer Junior Member

    Thanks for the tip; I had a look at Welsford's site. I'm not averse to building a boat with some nice curves, but "easy to build" is not the same as "quick to build," and those complex shapes look pretty labor-intensive. My design does have some curve in the ends, and I can modify it later; but the boxy shape seems like a good starting point.
     
  10. stubby
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    stubby Junior Member

    Ahh ok, if you want quick to build then by all means go for s boxy shape, some of those curves may look hard but in all reality they are not to bad, just read the study notes there is an active jw boatbuilders forum where John Eelsford can help, but I'm the long run a boat with nice lines will always attract a crowd, and if you take the time to build a boat the end result is always that much better.

    But just so others can help with ideas what length do you want, do you want easily single handed and able to do long adventures in it ect? Answering these questions always gets you a much better response.
     
  11. stubby
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    stubby Junior Member

    Ahh just read a bit more it would seem you want to single hand and adventure. I would definatly consider taking the time to design a nice boat, have a look at John Welsford's Sweet Pea or Penguin, Glen L also has some nice designs that you could get ideas from, for a first design i would go and almost copy the lines of a boat you like. And even make s small 1m model, just to get a good look at the shape of your boat, and a model only costs $80 max and if your real keen chuck some r/c gear in it.
     
  12. stubby
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    stubby Junior Member

    Also for books look at Aero-Hydrodynamics, and the performance of sailing yachts, by Fabio Fossati. Dad just got it for me for me bday, it will help you with boat design, and it speaks in English(as opposed to some weird boat design language), and if you can be bothered with it, it does go a bit more in depth and uses that weird boat design language. But for me, wanting to do Naval Architecture in uni, it is great. But it has also helped me understand a bit more on how the boat actually works.
     
  13. Kent Multer
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    Kent Multer Junior Member

    I've just spent a rather unpleasant hour trying to use Boat Express. It seems to have all the features I need; too bad none of them work, and least on a Vista machine. Would it be less frustrating on XP, or should I look for something better?

    Thanks --
     
  14. apex1

    apex1 Guest

    Kent,

    a software (I assume Boat Express is one) does not help you designing a boat!

    That is just a tool in need for a skilled user to produce a drawing that makes sense.

    Go for a proven design before you spent hours and $$ on a software which is senseless.

    The "instant boatdesign tutorial" isĀ“nt on the market, one has to learn or study that.

    Regards
    Richard
     

  15. marshmat
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    marshmat Senior Member

    Kent,

    You might have better luck with Delftship / Freeship+ (two different forks of the original Free!ship- the former with a professional bent, the latter a bit less refined but with more free features), both of which run on Windows 5.x and 6.x (this includes W2K, XP, Server 03/08/08b, Vista and Win7) as well as some WINE setups.

    The software can make it easier to visualize things in 3D, and when it comes time to get the final numbers, it can help with that too. Before you can create a useful model, though, you have to know what parameters (length, beam, draught, displacement, Cp, Cm, desired righting arm curve, etc.) you want the boat to have- in other words, translating your end goals into the mathematical language of hull design needs to be done before you can start defining a hull. Then you need to know how those parameters will affect various trade-offs, and how to balance it all in a shape and structure appropriate for the task.

    I'm one of the new generation engineers who grew up with CAD and is used to doing everything on the computer. But I've come to believe that the machine is just a tool- it'll speed up things you know how to do, but if something doesn't make sense on paper, it won't suddenly get better when you do it in 3D. Have fun with the 3D models, but keep the overall design process in perspective. Knowing what you're trying to design, and how to design it, comes first- the computer just helps to speed up some of the tedious parts of the calculations.
     
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