Proa design

Discussion in 'Multihulls' started by Tcubed, Sep 13, 2008.

  1. Tcubed
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    Tcubed Boat Designer

    Looking for people that have experience designing, sailing or building Proas to discuss the topic. I am planning on building a 54 foot proa to my own design, and would appreciate any extra pearls of wisdom on the subject. I also want this discussion to restrict itself to real shunting Proas, not asymmetrical catamarans.
     
  2. Alik
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    Alik Senior Member

    54' foot is a big boat, but why proa? What will be the re-sale value of this boat?

    Try to get Norwood's book on sailing multihulls, some aspects of proa design are covered.
     
  3. rwatson
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    rwatson Senior Member

    Of all Proa designs in the world, the one detailed at

    www.harryproa.com/concept.htm

    Makes the most sense to me. I have been following the design for a long time, and it ticks all the proa concepts for carrying capacity, ease of use, tested design etc

    There is still plenty of optimising to do, but the basic concept has is very advanced.
     
  4. Tcubed
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    Tcubed Boat Designer

    Alik, to me one of the primary advantages of a multihull is its great speed. however for this to work it must be a real multihull with a displacement/length ratio of 50 or less and a fineness ratio of 10 or higher. Therefore for it to be a liveaboard it must be long, otherwise it becomes extremely cramped. Also the way i look at it the "size" or "amount" of a boat is bettter measured by displacement rather than just length. I'm aiming for about 3500 kilograms displacement which is not very much boat at all.
    Rwatson, yes i have looked at harryproa and actually was pleasantly surprised that he has arrived at a lot of the same conclusion as i have. I discovered his site having already pretty much created my design. However it's not too late to give it some tweaks if this thread gives me reason to...
     
  5. Tcubed
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    Tcubed Boat Designer

    Alik, i'm not too concerned about resale value as it will be for me. However if the design as good as i hope it will be and i can get some worldwide visibility for it it might actually have a surprising resale value..?
    Why proa? Ok here is my thinking;
    1*Out of the three multihulls it is the quickest easiest build,
    A tri is a hull plus a simple catamaran, A catamaran is two hulls, a proa is one hull and a float, I would estimate about 75% the work of building a tri
    2*I only live in one hull
    The same as a tri. This is something i do not like about cats , that the living space is split into two. And before you say 'bridgedeck' let me say there are few things that make me cringe as much as those charter cats with the massive platforms. I want performance, not a floating condo.
    3*It is potentially the fastest type of multihull
    I know this is bound to get some people worked up. But i'm sticking to it, and will explain my analysis in later posts so everyone can pick it apart.
     
  6. rwatson
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    rwatson Senior Member

    I dunno TC, the resale value depends on popularity, and these boats arent mainstream. But, if you get it right, maybe you will want to keep it.

    All the reasons you give are the same as on most Proa sites, and yet, there are very few out there on the water.

    The thing that will make these boats popular is making them usable as well as efficient. So many are built with egos, and not effective design principles.

    Better put some concrete ideas down on paper, and lets see if we can give you heaps of criticism :=)
     
  7. Tcubed
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    Tcubed Boat Designer

    Rwatson, resale value is not really my interest.
    There are very few out there, yes, but does that mean they're not good?
    Most people buy boats that resemble whatever gets raced without realizing that the race boats are completely warped by race rules. This is what i call the commercialization of the industry. After all boats get mass produced to appeal to the lowest common denominator to make a profit. This is why most boats are so 'standard' looking. People take it for granted that these designs are modern and therefore 'good' when in fact most production boats nowadays have grave performance and seaworthiness issues...nuf said.
    One of the reasons there are not more proa's out there is that the vast majority of people are put off by the whole shunting business, I think, amongst other things.
    Yes i will post a drawing further on so you can all tear it apart. I just hope the criticism will come from well thought out logic or experience not prejudice.
     
    Last edited: Sep 13, 2008
  8. BWD
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    BWD Senior Member

    can you upload a .jpg file?
    Easier to see...
     
  9. Tcubed
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    Tcubed Boat Designer

    trying to upload image and having a bit of trouble converting the maxsurf file into a jpg..
     
  10. Tcubed
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    Tcubed Boat Designer

    second attempt. I Just took a photograph of the screen. If this works i'll just do it like this from now on until i find a better way. The design is not finished by the way..
     

    Attached Files:

  11. garydierking
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    garydierking Senior Member

  12. Tcubed
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    Tcubed Boat Designer

    Woah.. Thanks for those links. In all my proa googling had never come across any of them.
     
  13. Tcubed
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    Tcubed Boat Designer

    Here is another angle of it with the aka's sketched in
     

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  14. rwatson
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    rwatson Senior Member

    Its going to be ******* to shunt. Is that some type of turntable thingo under the mast ?
     

  15. Tcubed
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    Tcubed Boat Designer

    Yeah i'm under no illusions about the effort required to maneuver the thing.
    And yes, the sponson's upper edge is a section of circle centered on the mast step. Along that edge, is a track for the mainsheet which gives good twist control. The whole sponson offers a excellent base for sheeting the jib too. It ends up being like Russ Brown's method. The mainsheet (or really the traveller control) is freed, the jib dumped, the up board lowered, the down board raised, the main sheeted in and finally up with the other jib (by this stage the boat is already well on it's way on the new board. Short tacks would be done without the jib of course, and the central daggerboard would be partially raised to balance. I toyed with a number of different ideas, before eventually deciding Russ's system was probably as good as it's going to get.

    I'm not worried about this for a couple reasons. One is i will mostly be doing longer passages where shunting is not very frequent. Another reason is that i was brought up on an engineless fifty foot gaffer, with no electricity. So believe me, i'm used to flexing a couple of muscles when it comes to sailing! In fact, most of the time, we had two jibs and running backstays so that would be six things to deal with the same as above. Well sort of...

    From experience, the hardest thing is raising and lowering the endboards. To make it at least possible, i plan on making them hollow with generous (but carefully faired) holes for the water to flood them and fall out of them. Also there will be some sort of rollers that they press against. Otherwise, i know that as soon as they are under pressure they are basically impossible to move. The rest is piece of cake.
     
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