Planing Trimarans

Discussion in 'Multihulls' started by Doug Lord, Sep 30, 2006.

  1. yipster
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    yipster designer

    could that be related to your interest in multi hulls? :p
     
  2. Leo Lazauskas
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    Leo Lazauskas Senior Member

    And I had just got to the bit where I was going to explain why the use of foils is a revolution according to Doug :p

    But seriously, I think we should be able to estimate when the dynamic forces and moments on a displacement monohull (or the main hull of a trimaran) are significant.

    All I need is the offsets of a hull we can all agree with as a starting point.

    Cheers,
    Leo.
     
  3. cavalier mk2
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    cavalier mk2 Senior Member

    I'm sure those guys could drive too, those boats are sensitive to sail placement and design and tend to work better with the stock plan. On a off wind course there isn't much side force transmitted and the hump is noticeable. Jim Brown warned me about the dangers of sailing machismo......so I'll have to tone down performance talk so we don't scare the school kids moms. Since we have to save the sails for cruising any test riders will have to bring (and leave!) a set of sails from a loft of our choice. A suit of sails-expensive. Contributing to the preservation of vintage performance multihulls and their performance curves, priceless !
     
  4. Chris Ostlind

    Chris Ostlind Previous Member

    So, now this has evolved to an Aladdin's Lamp exercise?

    Somebody call Disney to report a theft. ;-)
     
  5. Doug Lord
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    Doug Lord Flight Ready

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    Looking forward to this! I think.
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    Leo, I'm not sure using the offsets of ,say, a Farrier hull to " estimate when the dynamic forces and moments....are significant" would resolve anything here. Seems apparent to me that for some to grasp the concept it is irrelevant whether or not a certain hull will plane because these same people refuse to recognize that any hull can plane if the ama to which it is attached is in any way loaded. A way to illustrate that a hull CAN PLANE while attached to a loaded ama would get to the heart of the matter but is unlikely to "convert" the trully misguided-facts don't seem to seem to have any affect.....
     
  6. Chris Ostlind

    Chris Ostlind Previous Member

    Would this be the same failure to grasp that didn't allow the entire sailing world to "get it" when one of our members said, with an apparent straight face, that "Helium is one of the most significant developments in sailing over the last 50 years!!!".


    Since you are so enamored with the concept, then just do this... Ask Ian if one of his boats is not a complete, engineered structure. One that has all of its component elements acting as a unified structure.

    All of the rest of us know the answer to that one already, but it will be interesting to see if you have the temerity to first ask and then report, accurately, the response. I'll give you a clue. Ian has, on dozens of occasions, gone to great lengths to emphasize the fact that his entire boat is professionally engineered to behave as a cohesive unit. He further iterates the point when he speaks to the seriously powerful engineering of his aka and folding structure as a unified component of the entire boat.

    Ian Farrier - "The basic design philosophy has always been to provide safe, roomy, well engineered multihull cruisers with performance provided by design efficiency and good engineering, not at the expense of accommodation, structure, or safety."

    Now, Ian may surprise the sailing community and admit that his boats are not cohesively engineered structures, thereby allowing for individual identity of the component parts (such as the main hull planing while the ama is pressed to the max) and what they are doing without impact on the other parts of the boat... but I doubt it.

    So, if the boat is acting as a complete, engineered structure, then how is it that one can break out components and call them one thing while the rest of the boat is doing something entirely differently? Do we award isolated speed records to a vaka hull, or do we award them to an entire structure? Do we call them trimarans, or do we instead refer to them as planing main hulls with those unfortunate thinga-ma-jigs sticking out to the sides causing all sorts of spray? (don't answer that, you leadminers ;-) )

    Ian acknowledges the f-boat process of the so-called, planing state through heel, rather than dynamic hull lift, when he says on his website, "This is made possible by the center hull lifting as the boat heels, rapidly reducing hull width..." http://www.f-boat.com/pages/introduction/features.html one third down the page under the heading: Hull Lines

    Lastly Doug... When are you going to acknowledge and answer to the obvious discrepancy in the trimaran planing claims when it has been shown, visually, as well as through common knowledge, that even lowly beach cats can exhibit the same "planing" characteristics that you wish to ascribe to a trimaran? Yet, I have never heard a beach cat sailor ever describe their boats as planing craft when they lift and hold one of their hulls at the surface for an extended period. One would think that the cat community would be ready to jump all over this potential for marketing purposes, and yet, strangely, they never do. Could it be that the cat folks are simply using common sense by recognizing what forces actually got their windward hull to the surface?

    Nahhh, that would be much too easy of an answer.

    If you want to conclusively prove the point you wish to make, then simply do what Paul B and I suggested already; That being to strip away the amas from an F-boat, get it out on the water with full rig and get it on. If the boat, in that condition, can get up on plane and stay there under control, then you and Tom and Ian have your point made and I will gladly walk away from the discussion. These are real boats, not theoretical dream schemes. Prove it in the real world.

    Failing that, you've got bupkus.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    See what I mean, Leo.....
     
  8. Capn Mud
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    Capn Mud Junior Member

    Chris is right - it is so damn obvious I cant believe this has taken 20 pages of discussion.
     
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  9. Chris Ostlind

    Chris Ostlind Previous Member

    ... as he adjusts his ascot and silk paisley smoking jacket with the sateen lapels. ;-)
     
  10. Doug Lord
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    Doug Lord Flight Ready

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    Sorry, but Chris is dead wrong-it's so damn obvious I can't believe this has taken 20 pages of "discussion"......
     
  11. Chris Ostlind

    Chris Ostlind Previous Member

    Well, Douglas... the path to proof for your argument has been laid before you. All you have to do is go forth and perform the experiment. Your salvation awaits should you have the necessary equipment in your manly arsenal. It is you making the claims and it is incumbent upon you to produce said proofs.

    Failing that, perhaps a quick, cold shower will settle you down so that you can see the obvious. Best of luck, whatever you manage to slap together.

    The fact that there are 20 PAGES of responses here indicates, overwhelmingly, that the claims for planing trimarans are now and will probably continue to be... specious at best. You still have not indicated why, under identical conditions as specified by you, (e.g. heeling over on the leeward hull due to wind pressure on the rig) that the typical beach cat is also not a planing vessel. You have also not produced a catamaran sailor who claims to be on plane when he lifts the windward hull of his boat and skims it across the surface. In short, the claims regarding trimarans are pure bunk unless and until you can produce a boat in which all the immersed hulls are on plane, thereby satisfying any doubt as to the sailing condition of the example boat as a complete and unified structure.

    Perhaps a measure of silence on the topic would be in order until you can satisfy the need for proof?
     
  12. Richard Woods
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    Richard Woods Woods Designs

    This is too long a thread to read in its entirety, so what I say may have been said before. My apologies.

    I don't think any trimaran planes, at least not as a speedboat or a high performance dinghy does. But if any trimaran DID plane it would be a Farrier.

    A few weeks ago Catsketcher and I sailed together on a F27 on a breezy San Fransisco Bay. We touched 16 knots at times. However I think Catsketcher will agree with me that we still didn't plane like a dinghy. (Both of us have years of experience in planing dinghies so know what it feels like)

    Lots of spray and a lifting bow (because of a flat bottomed hull) doesn't a planing hull make.

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  13. Doug Lord
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    Doug Lord Flight Ready

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    Richard, both the 14 and 20' trimarans I built planed-no doubt about it. I think you could certainly define Bethwaites HSP as a planing tri! And the WETA sure does plane:

    http://www.youtube.com/watch?v=-LiZkmoSmhY&feature=player_embedded#!

    Click on two boat image and then again on resulting image for largest, clearest view:
     

    Attached Files:

  14. Chris Ostlind

    Chris Ostlind Previous Member

    So, now we are comparing a 14' Weta, sporting a very different hull form, to a 27' F-boat, are we?

    Desperation, Doug, does not make for a solid argument. The Weta has a very different vaka hull compared to any F-boat. I invite you to take a close look at the hull surface-to-transom juncture, along with the overall rocker of the hull.

    And your boats, er... trimarans, wherever they may be at present, did not plane either if they put their amas in the water to hold the boat upright while lifting the vaka to the surface.

    Real simple stuff.
     

  15. Richard Woods
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    Richard Woods Woods Designs

    Hopefully my final comment on this thread

    In simple, user, terms:

    A dinghy sailor knows when his boat starts to plane. He gets a gust and the boat accelerates very quickly and lifts up. Same with a speed boat when the operator opens the throttles.

    I haven't ever sailed a multihull that behaves like that, they all gradually increase speed with no obvious "semi displacement" boundary speed, just like the F27 that Catsketcher and I sailed.

    Probably this is all just sophistry

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
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