Optimizing a Tri for Light air

Discussion in 'Multihulls' started by Vincent DePilli, Mar 9, 2011.

  1. Samnz
    Joined: Nov 2008
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    Samnz Senior Member

    Phil your so wrong on this one sorry. If we compare our Orma 60 Vodafone with Limit a full on 60 ft racing mono the orma 60 wins everytime any breeze any angle!

    Vincent the answer is so simple, your boat is too heavy and has not enough sail area. fix one or the other or even better, both...

    Of course a tri with same weight and sail area will be slower than a mono in light breeze! more drag! the whole point of a multihull is its light and can carry more sail
     
  2. Samnz
    Joined: Nov 2008
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    Location: Auckland

    Samnz Senior Member

  3. Vincent DePilli
    Joined: Apr 2006
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    Vincent DePilli Junior Member

    "Vincent the answer is so simple, your boat is too heavy and has not enough sail area. fix one or the other or even better, both..."

    This seems right. Weight is the key.

    But I am not interested in a tri that designed to fly the main hull, like an Orma 60 or (closer to home) the Seacart. Too scary, not right for cruising. And no lifting foils—expensive and complicated and heavier. I want a 2 foil boat that does what that the F31 does (excluding fold), but that weighs much less, and can be built with New zealand style backyard med tech.

    I suspect that this conservative dream boat would want to have water ballast for when I get scared, which is often.

    This is probably a dream unless the economy improves significantly. Purely entertainment’s sake, I am putting together a spreadsheet that compares what I could get from selling my boat ($80,000 -??), with the cost of building a new hull/beam package, and using the rig and all the bits from the existing boat.
     
  4. Gary Baigent
    Joined: Jul 2005
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    Gary Baigent Senior Member

    Vincent, it is easy to improve on stock multihull designs ... but you have to accept tradeoffs/sacrifices - meaning a determined, not half assed, attack on weight, which means gutted accommodation, no junk and clutter aboard, no motor, fuel tanks and so on. If you want to sail cheaply, you have to be somewhat Spartan in your approach. Remember what Dick Newick said regarding speed and luxury, you can't have them both. Also by dumping junk, your boat immediately gains power plus becoming lighter in weight - which allows you the luxury of speed to run away from dangerous situations, more buoyancy, more righting moment ... and most importantly, less sail area horsepower to gain this speed. Lightweight means safety.
    Anyway, all this is obvious stuff ... but surprisingly few people will adhere to it. Conformity and class conscious nonsense takes over - "no way are we going to squat on our boat like a Polynesian on an outrigger." Misses the point; the greatest luxury is effortless speed.
    Anyway, I'll post soon the latest images of Seditious Sid - a crazy boat that has the above philosophy. You could downsize the rig and still have a very fast boat .... but the accommodation is not salubrious.
     
  5. oldsailor7
    Joined: May 2008
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    Location: Sydney Australia

    oldsailor7 Senior Member

    Phil hit it on the head.
    Light weight, low wetted surface, for light winds.
    Thats what makes the Buccaneer 24 so good. It is light. Has a moderate L/B ratio & near semi-circular bottom---(low wetted surface), dihedral on the crossarms for fast tacking and keeping the floats out of the water in light airs.
    Coupled with a high Bruce number it leaves other boats for dead in light wind flat water conditions. :D
     

  6. luckystrike
    Joined: Feb 2010
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    Location: Germany

    luckystrike Power Kraut

    Dear Phil,

    I find it difficult to discuss such a theme without any visualization. In general we have all the same opinion: "A light boat with a good sized sailarea and a mainhull that has a shape that is designed for that wheight (not a fat hull with a light wheight) shall be faster allround than the F31 (even a light one) and be able to beat the melges 32, without sacrifising seaworthyness and small drawbacks in the question in the interior space.

    Have a look at this:

    http://www.multihulldesigns.com/designs_stock/d30tri.html

    and this

    http://www.multihulldesigns.com/designs_other/31slidingarmtri.htm

    Fine mainhulls with a 10.5 to 1 ratio, light wheight, reasonable interior, good stability, built from wood or sandwich. Swinging-, folding-, sliding- or fixed demontable beams, just as you like it to have.

    Its all there, no need to reinvent the wheel.

    Grreeetings from the North Sea Coast, Michel
     

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