Building a racing monohull

Discussion in 'Sailboats' started by crossfire266, Mar 24, 2014.

  1. crossfire266
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    crossfire266 New Member

    Hello,

    I was wondering if I could get some assistance. After some research i've found out that in general that many racing monohulls achieve a L/B ratio of 4-6.

    I was wondering if anyone could help me out in achieving this by designing a hull that meet these design constraints...

    Maximum hull size of500mm (long) x 300mm (wide)
    x 200mm (deep).

    Any help will be much appreciated!

    Thanks in advance!
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Half a metre long ? A radio control model boat obviously ! Maybe you meant 1500mm long ? That tallies better with L/B ratio of 4 to 6.
     
  3. crossfire266
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    crossfire266 New Member

    It's a radio control model boat!, im restricted to those constraints according to the race rules unfortunately :(
     
  4. crossfire266
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    crossfire266 New Member

    Any idea where can I acquire good information in obtaining an 'optimal' dimension hull within those constrains?
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    You are possibly better off asking people who are more knowledgeable about RC racing boats, than full size. Maybe on a specialist forum dealing with the subject. The two things are very different, as Aleksandr Orlov would say. Simples ! :D
     
  6. crossfire266
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    crossfire266 New Member

    Oh I see! Well thanks anyway :)
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    I'm not saying there isn't commonality in some aspects of design, but when the need to consider the welfare of passengers is removed, the options widen somewhat. I'd "guess" that you could go (relatively) lighter and slimmer than "real" boats, for starters. But I am pretty sure the afficiandos of your sport would have jerried to the possibilities that actually work best, long ago, and it is just fine tuning from there.
     
  8. Munter
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    Munter Amateur

    The parameters you outline don't really allow the development of a serious answer. There are too many unknowns that could completely change the "right" answer.
     
  9. Skyak
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    Skyak Senior Member

    This is a model boat with class restrictions? Please post the rest of the restrictions -particularly draft. Length and beam do not scale down linearly, and RC models don't have the ballast shifting of crews.
     
  10. messabout
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    messabout Senior Member

    Crossfire; there are several other factors to be considered beyond L/B ratio. Height of the mast, sail area, ballast ratio and more.

    I suggest that you dig into the American Model Yachting Association (AMYA) web site. You can find many classes of boats, some of which have lines drawings. Those line drawings will make a good starting point. After that there are many other decisions to make. Also go down to the hobby shop and look at some of the boats that are sold in kit form or ready to sail form.
     
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  11. Doug Lord
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    Doug Lord Flight Ready

    RC Models

    ==================
    In classes such as the Marblehead it has been found that approaching a 10/1 length/beam ratio at the waterline is fastest. Look at the classes sailed in the US here: http://www.theamya.org/ What class will your design be part of? One good source of info is other members of the class-lot's of time the guys in development classes are real helpful.

    Some one offs have used movable ballast and/or spinnakers:
     

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  12. UNCIVILIZED
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    UNCIVILIZED DIY Junkyard MadScientist

    There are a HUGE number of factors which play into how "fast" a racing yacht is. And more often than not, "rules" & class constraints get in the way of what makes for the fastest boat of any given size. Such is an historical FACT.

    That said, I'm not sure under what kind of constraints you're design is operating under. But in terms of designs to perhaps consider. For semi well-rounded speed, in terms of varied wind angles anyway, look at the Volvo Ocean Race boats - both current, & past generations. Especially the old gen VOR 60's, as they were fixed keels. For more optimization for offwind, the Open/ORMA 60's & shorthanded round the world racers.

    Though in both of these design types, especially the latter, the L/B ratio is more like 3:1. And if you're curious about design, The Amateur Yacht Research Society's website www.AYRS.org & or their publications have a LOT of interesting info.

    Also, it might pay to take a look at the winning design types in your fleet, & compare them to similar/related crewed, full sized, one-design vessels. They tend to be fairly innovative, especially when the class is new/young. And or small in size physically/inexpensive to build & experiment in/on. Kind of like say International 14's, the Little America's Cup cats, & or A & C class cats. Boats/fleets where one or two guys of reasonable means, that are handy with tools & are creative + intelligent, can build-n-mod' their own boats.

    Andy


    EDIT: I just ran across this old posting, but didn't have the time to check the links there in. Perhaps it'll help. http://www.boatdesign.net/forums/all-things-boats-and-boating/super-slender-racing-yachts-5726.html
     
    Last edited: Jul 14, 2014

  13. PAR
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    PAR Yacht Designer/Builder

    Instead of attempting to "design" a boat around a very limited and singular restraint, it's always best (with all racing craft, regardless of scale or type) to design around the rules. Simply put, you're not designing an RC pond yacht, but actually a rule beater, possibly with ideas not employed by the other competitors. The rules package is intended to limit your options, in an effort to level the playing field, but the clever designer uses the rules to their advantage, whenever possible and beats the rest of the fleet over the head with these "rule stretchers". If I was designing an RC yacht, I wouldn't look at real boats, just the fastest of the RC fleet and of course, a very close study of the rules package, for avenues of pursuit I might take advantage of.
     
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