Proa Questions: Atlantic vs Pacific

Discussion in 'Multihulls' started by Inquisitor, Jun 22, 2010.

  1. Inquisitor
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Assume I am and future readers of this thread are fairly logical and have done the forum and Google searches. I have read quite a bit here and on the Internet. From where I stand now, its seems rather heated and nearly to religion status... like the Inquisition. :)

    This is what I think is the definition of the two standards. (Please correct or clarify if necessary)

    Pacific Proa - The traditional. Large leeward hull holding accommodations, very small windward hull. I'm guessing... but, it appears these run around 10% of the weight of the leeward hull.

    Atlantic Proa - Smaller, but heavier windward hull holding most (or all) accommodations. Larger, but lighter leeward hull. Weight seems to be around 60% in the windward hulls versus 40% in the leeward hull. Although more performance oriented versions seem to go quite a bit higher in the windward hulls... (70%, 80% ????)

    Here is what I gather are the strong points of each. Are these correct? Are there more issues to evaluate?

    1) Sailing in light winds. It seems that Pacific Proa would have a higher top speed (in light winds) by tending to lift the windward ama and thus reducing drag.

    2) Sailing in heavy winds - It seems the Atlantic Proa would have a higher top speed (in heavy winds). That as the weight is shifted off the heavier windward pod onto a far longer (more speed efficient) lee hull.

    3) Gusty winds - It seems the Atlantic Proa would be more tolerant of gusty conditions that might blow over a Pacific Proa. (I understand about the extra buoyancy leeward pod keeping from turning over, but I'm more concerned about my non-sailing guests (and the Admiral herself ;) ) staying at < 10 degrees heel.)

    4) Smoother ride - It seems that as the Atlantic Proa tends to lift the accommodations out of the water (and eventually flying) that the "ride" ought to be more comfortable. Using the beams as springs to absorb some of the shock.

    5) Dryer ride - Again the Atlantic Proa seems to keep dryer while all the spray is flying around the leeward and being blown away from the accommodations.

    6) Are there any other issues?

    SO... THE REAL QUESTION
    If I assume the above are all true... what keeps one from designing a Proa with (or has someone already built one like this):

    (a) configured more like an Atlantic. But say... it is closer to 85%-90% in the smaller accommodations (windward) hull.

    (b) The (far longer and lighter) is heavily optimized for ultimate top-end speed. Even to the point of using planing, stepped hulls.

    What keeps you from:

    1) Sailing it like a Pacific Proa in light winds. Thus lifting that light, long planing hull out of the water when you are at mere displacement hulls speeds... say ten knots or less?

    2) Sailing it like an Atlantic Proa when you are in a high wind speeds and/or running on the ragged edge of flying that 90% weight and upwards of twenty knots.

    3) And Sailing it like an Atlantic Proa when you on a long distance (autopilot) cruise, sail it as an Atlantic... comfortable, dry and conservative.

    ... or is that what people do with their Proa's anyway... and I'm just clueless.
     
  2. Alex.A
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    Alex.A Senior Member

    I too am fascinated by Proa's.
    It seems - Atlantic/wtw for cruising and Pacific for SPEED.
    Pacific people's created these amazing boats - and i often wonder where they'd have gone if they'd had modern materials.
    Just paged through the latest sail mag and lots of nasty big plastic condomarans.....AAAARGH!
     
  3. KSONeill
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    KSONeill Junior Member

    I don't know of any pacific proas that switch out between modes. You'd have to have two long hulls, might as well have a cat and have real transoms and simpler rudders and foils, more control over where the CE is, lots of advantages if you're going to alternate which hull is to lee.

    Maybe Atlantic boats do? Look at this page:

    http://wikiproa.pbworks.com/Images-from-the-Proa_file-archives-page-3

    Look at the last picture of Tahiti Douche. Two sets of sheets? Maybe they tack it in light air.

    I don't think Atlantic proas are slower, or at least I don't think that's been shown. I collected a bunch of pictures that had been posted to the proa_file archives by some French members:

    http://wikiproa.pbworks.com/Images from the Proa_file archives

    French racing boats and some Newick designs, almost all Atlantic proas (one is a tacking outrigger, Cormier at the top of P2).

    Rob Denney has done a lot of work on WTW proas (weight to windward like an Atlantic, rig to lee like a Pacific), that's sort of a third option.

    I'd take a Pacific proa for a small boat that's intended to be exciting to sail, but an Atlantic or a WTW for a cruising boat. Flying a hull in a cruiser is perhaps more excitement than I'm up for, usually.

    K O'N
     
  4. tspeer
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    tspeer Senior Member

    You're missing the third type - Rob Denny's Harry proa. Accommodation to windward like the Atlantic, sails to leeward like the Pacific.

    It has the weight to windward for the stability of the Atlantic, and the leeward hull can be optimized for sailing performance. No need to compromise the accommodations for the intrusion of the mast.
     
  5. Inquisitor
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Thank you for the links... I start surfing from there.

    I guess I didn't quite get my point across. I think the Atlantic would be faster all the time, except in light winds. In that one small case, the Pacific (appears to me) would more readily lift its light (10%) Ama and thus reduce friction, where the Atlantic would be dragging both. I'm guessing this point is probably down in the noise level. I guess I'm trying to figure out if there are ANY benefits to the Pacific design.
     
  6. Inquisitor
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    I've been digging into Rob's design and although distinctly different, for this current question, of just which way it tips and which hull tips, I kind of see it as the same as an Atlantic.

    However, you bring up another question I was planning on asking...

    Besides mast intrusion into living space, are there any other benefits of Rob's Harry Proa design of having the mast on the lee hull?
     
  7. KSONeill
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    KSONeill Junior Member

    I think your proposed 90/10 weight distribution would be hard to accomplish. The heavy hull, if it is to be to lee, has to be at least moderately long or you risk a diagonal capsize in a puff. The boat has to sail now in all four configurations; both ways with one hull to lee, both ways with the other. If you're planning to fly the light hull, which is normally to lee, I'm not clear on where the rudders are. So steering and sitting and so on have to be arranged for. Awkward, a lot of extra arrangement to carry around for minimal benefit. If you're planning to fly the light hull, which is normally to lee, I'm not clear on where the rudders are. Four rudders? Ugh.

    As far as the Pac proa having any advantages at all, as I said, a Pac proa seems to me to be pretty clearly the way to go for a daysailor. That's what my boat is, and I like it:

    http://wikiproa.pbworks.com/Kevin's boat

    Just by moving a bit on the tramp I can be barely flying a hull in anything from five knots to twenty without any reefing.

    Russ Brown's boats are Pac proas:

    http://www.wingo.com/proa/brown/zahnisers/index.html

    and they're well thought of. He can pump water into his windward hull to get the effect smaller proas do by moving the crew. That's a fast boat in the right hands.

    There's a French cruising boat called Des Jours Meilleurs:

    http://prao.guillard.free.fr/index2.htm

    http://www.google.com/#hl=en&safe=o...s meilleurs prao&gs_rfai=&fp=27f6527a3674d17d

    I really like that boat.

    If you look here:

    http://wikiproa.pbworks.com/external links

    one of the early sections is "Articles on proa design". There's a link to Rob Denney's article on Harryproa design, and to Joe Oster's article on Pac proa advantages. Those are pretty cogent summaries of the two points of view.

    Being able to keep the boat right on the edge of flying a hull through a wide range of wind strengths is a nice thing, right up to the point that you're just trying to go cruising and you go below to make a cuppa and the person steering the boat sends it over. So, it's really up to who's going to be sailing it. Russ Brown has been pretty non-evangelical about his proa designs for exactly this reason, I think. My boat certainly has that 'feature'. I've sailed it safely for a week's cruise, camp cruising two hundred miles up a pretty desolate coast in well over twenty knots of wind every day, and felt quite safe and had fun. But you can capsize it in five knots of wind if you're sitting on the lee hull and not paying attention.

    K O'N
     
  8. KSONeill
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    KSONeill Junior Member

    In case of capsize, it's much to your advantage to have the rig in the lee hull. The boat only goes to 90 degrees, much easier to recover. Better than in a cat, where the mast tip sinks, and much better than in an Atlantic proa.

    It also centralizes the part of the boat that has to take stresses; the rig, beams and rudders are all close together. The rest of the boat can be very light.

    And you can see the sails better if they're to lee of you. I don't like sitting right under the rig.

    K O'N
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    The theoretical advantage behind a pacific proa is that it is less prone to capsize if caught aback because of the smaller sail area carried. The atlantic proas finally got banned from the old O-STAR because they capsized when caught aback because of being able to carry more sail with the ama to leeward. The Harry proas are closer to a pacific in concept with the accommodation ama taking the place of the islanders hut on the deck. They should have enough buoyancy not to capsize when caught aback. Some of the pacific styles had the mast on the deck allowing the leeward hull to provide some righting moment while the ama provided the lever arm. The islanders sailed with a lot of crew so adjusting trim was pretty easy. Ballast cars on deck with water tanks might be faster to adjust than pumping water into the ama. Cruising they could carry the fresh water stores, and be refilled with rain water or sea water if necessary. I would think the hydrofoil guys would use a t-foil to adjust ama height using it to limit heel (down force) or provide lift depending on conditions. Such things can make carefree cruising more complicated though !
     
  10. KSONeill
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    KSONeill Junior Member

    Ah, sorry, I didn't realize that was an old message. I edited it without looking.

    You may be right about Atlantic proas. Take a look at the link I stuck in above, it looks like Tahiti Douche does sometimes tack. I would suppose that's just to be more maneuverable in tight quarters, but who knows.

    K O'N
     
  11. KSONeill
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    KSONeill Junior Member

    No. Pac proas are more prone to capsize when aback, not less.

    K O'N
     
  12. cavalier mk2
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    cavalier mk2 Senior Member

    Not if the ama is providing buoyancy! If you have a log out there I think you have to call it an outrigger. When an atlantic gets caught aback it is relying on the weight of the ama which usually is far less than what it needs to stay up. Check out Rory Nugent in the Ostar etc.... lots of great capsize info out there.
     
  13. Alex.A
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    Alex.A Senior Member

    In larger sized proa's - why not use the float for storage or even accomodations? Could charter - with crew in lee and guests in main hull?
    More work/costs but still cheaper/lighter than a cat?
    If the float was heavy enough you could have a cruising proa in either configuration?:D
     
  14. Inquisitor
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    I believe Rob's HarryProa does have (2) single births in the lee hull of his larger models. Sounds like a great idea to market it to the cruising industry... customers have the hull to themselves (most of the time) and the crew seperate.
     

  15. Inquisitor
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    Inquisitor BIG ENGINES: Silos today... Barn Door tomorrow!

    Cool boat! :cool:

    What do you think of the dual mast rig? Lower COE so you could probably carry more sail. But more to deal with. Have you found any disadvantages?
    Could you recommend it for a large cruising boat? (40+ feet, 6+ crew)

    Thanks for the links.
     
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