High Power Very Small Tri(s)-10'-14'-why not?

Discussion in 'Multihulls' started by Doug Lord, Jun 27, 2010.

  1. Munter
    Joined: Jul 2007
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    Munter Amateur

    Fantasy, hype and a lack of substance!

    Doug - your last long post has just gone back to unsubstantiated hyperbole. You still haven't proven anything. Your one line response to my abbreviated history of the mass issue doesn't make it go away.

    I do give you credit for putting forward target masses for each of the components though - you seem to have understood that repeating the cube rule line isn't really substantiation. You even go so far as to provide a panel weight and claim it is based on the actual hull areas. If you have hull surface areas you must have a design right? Lets see it!

    Your continued reference to the Weta as having larger sail area and therefore heavy scantlings is just silly. The difference is that the Weta has a spinnaker and your mini-tri doesn't. Comparing upwind sail area (and this is where you get the biggest loads isn't it?) - your mini-tri has more sail than a Weta, therefore, in terms of taking rig loads it must have at least the same scantlings if not more! Please stop ignoring simple aspects like this to try to justify your previous numbers, its completely see through.

    The figures you do quote are universally too low

    12 kg for the hull? Maybe for a moth hull but the mini tri has 50% more sail area so will need to be built stronger. At best 25kg.
    6 kg for a float? Even a smaller sailboard weighs more than that and it doesn't have the reinforcements for rigid attachment to the rest of the vessel. Say 12 kg per side.
    Cross arms - 3.5 kg's worth of tube spanning over two meters doesn't sound anywhere near enough to support the rig load or the skipper load. Again, at least double it to 10kgs per side.

    Total so far 69 kg

    Foils + wand 8 kg
    Rig 10 kg
    Lounges 10 kg
    Folding system 10 kg
    Total ~110 kg

    Note - I don't think this mass makes your project impossible but I do think ignoring a realistic mass estimate completely undermines the validity of any claims as to performance and awesomness. Why not work with an achievable mass so that your boat actually has a chance?

    Having previously told me off for categorising this as a "project" (when it was apparently just a "concept"), you've now told off Paul for saying you'll never build it (maybe you will (or not!)). What is it going to be? Build it and prove yourself or just keep it as a wet(a) dream? (boom tish!)

    I predict you will build nothing but continue to make a lot of noise on the internet self congratulating yourself about the amazing designs and discoveries you have made and chastising other designers for making such poor progress until you came along to teach them a thing or two. The last three years have been like that - why move out of your comfort zone now? Physics and reality will prove harder to ignore than people on the internet but you will only learn this if you actually build something.

    btw - now that you have the a-skiff hull back, why not chuck it all back together and take a pic or two of that old beast foiling like you used to claim it did. Evidence of such would be an enormous boost to your otherwise low level of credibility.
     
  2. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ===================
    Absolutely, unequivocally absurd and ridiculous! You simply ignore the facts and prognosticate about stuff you obviously don't understand. My weight figures are absolutely accurate -and conservative. Your attempt at "weights" with no facts is preposterus! Give it up-you ignore the important facts and
    invent others----too bad....
     
  3. Paul B

    Paul B Previous Member

    Hilarious!
     
  4. Munter
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    Munter Amateur

    Doug's right - 10kgs for the lounges was a pure guess.

    I didn't know whether the design called for lightweight velour or heavy weight leather.
     
  5. Chris Ostlind

    Chris Ostlind Previous Member


    This from the guy who built the non-foiling Aero-thud and openly confessed that it wouldn't foil because it was overweight...?


    I'm thinking that this should be your epitaph, Douglas. How absolutely Freudian of you to suggest such a line.

    Is there no limit to the goofy stuff you will say?
     
  6. Paul B

    Paul B Previous Member

    Apparently not.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    -------------------------
    This is very interesting. So you think the compression loading and shroud loading due to carrying an asy with over TWO THIRDS more SA than the WETA's upwind SA doesn't affect the scantlings of the WETA?! And that with almost twice the designed max crew weight(upwind and downwind)of the MPX-11?!!
    Oh, and lets not forget that the Weta mast is 21'4" long and may be 24' above water(see url's below) while the MPX-11 mast is only 19 feet above water(lower CE). Not to mention that the WETA has almost twice the RM of the MXP-11!

    The MPX-11 has 130 sq.ft. upwind and down-with a lower CE than the Weta while the Weta has 123.9 upwind ,210 downwind , almost TWICE the RM and you think the WETA rig(with max crew) is less loaded than the MPX-11(with max crew)?? And you're an engineer?
    Just plain nonsense.


    ============================
    =================
    Weta specs:
    Sail area – main 8.3 m2 ~ 89.4 ft2
    Sail area – jib 3.2 m2 ~ 34.5 ft2
    Sail area – gennaker 8.0 m2 ~ 86.1 ft2
    Total SA= upwind 123.9
    upwind + downwind=210sqft =1.61 X MPX-11 (161.5% more)

    Crew capacity 200 kg ~ 440 lbs =1.83 X MPX-11( 183.3% more)

    WETA RM=4815ft.lb at max load.(corrected 7/12/10 based on measuring the actual Weta ama.
    MPX-11 RM = 2664ft.lb. at max load
    (may require a max windspeed limit(or reefing) over a 2.00lb.sq.ft wind pressure (like the RAVE). This is because the foil will generate downforce which could exceed structural limits if not managed correctly. (updated 7/10/10.))


    Mast length 21' 4" http://www.wetawest.com/weta_marine_trimaran_specs.php
    Mast Height above water 24' http://www.wetacanada.com/specs.html
    ================
    ================
     
    Last edited: Jul 12, 2010
  8. Munter
    Joined: Jul 2007
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    Munter Amateur

    Hi Doug.

    If you read my post carefully you'd see that I specifically addressed upwind sail area. Perhaps a spinnaker would add to the loads, but your original comparison was totally misleading because it made no reference to the different sailing modes being compared. This hardly provides and appropriate basis for comparing the two numbers to arrive at a ratio of sail areas.

    Does the absence of a kite actually allow you to build lighter? Well - perhaps you could get away with uppers, a bowsprit, some running rigging and a little weight in the hull but it wouldn't be enough to take you from a realistic 100+ kg down to your 55 kg target.

    On the other hand, I'll put forward a reason why I think your alternate basis (righting moment) for expecting lower loads is erroneous. You have repeatedly referred to the differences in righting moments and I agree that this is can give an indication of relative rigging loads. You quote figures for righting moment but I can't see what configurations you have assumed. Presumably you are assuming that the full craft weight is supported on the lee hull and the crew mass is either in the central hull or up on the weather float. If so, is this scenario actually appropriate? How many times have you seen a Weta flying the main hull (rather than just having it temporarily pop out of the water? I haven't seen one.) I suspect the volume of the float is insufficient to support the whole boat weight + max crew weight so the scenario that you appear to have based the Weta calculations on is unrealistic. If the main hull remains in the water then any mass it is supporting is not contributing to righting the craft. If this is correct then the Weta will overturn before it gets to the flying two hulls state. OK - so I believe your hasty Weta righting moment calculations to overstate the righting moment but I don't know how much by because I don't know the float volume.

    Next - the mini-tri. I think your calculation assumes the crew mass sitting in the middle with the full weight of boat + crew being borne by the lee float. Apart from the fact that I think you have grossly underspecified the materials required to actually get to this state I think this only works in a steady state and ignores the practical aspects that will result if far greater loads. You have previously stated that the foils control the ride height of the central hull and that they maintain the selected elevation by pushing up or pulling down as required. What happens then when the tri is overpowered by a sharp gust? It isn't possible to change the elevation of the main hull instantly because the foils take time to change height so you effectively have dynamic, temporary righting moment. I don't think this is included in your calcs but if the foils are capable of supporting say 100kg pushing up then I'd guess they could also generate a similar force pulling down (a wild *** plucked guess that is befitting of the situation). What is the righting moment now? Nearly double the previous quoted figure? Will the structure simply collapse because you cut out material because you only considered the steady state case? The failure to consider situations beyond the most simple, ideal state will result in the design failing when the vessel moves outside of this envelope.

    Yes Doug, I am an engineer, though I think you should note that I haven't introduced that qualification in any way to try to justify my critique of your proposed tri. I have used simple concepts, references and terms to build arguments that have, for the most part, appear to have been ignored as you jump to bitter rebuttal of every post, regardless of the comments. Your attempt to use my qualification in a mocking manner shows something of your character and judgement.
     
  9. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    ==================
    I believe you introduced the concept of "a mocking manner" in one of your first few posts directed at me-and ended any chance of a reasonable dialogue. I apologize for any attempt to use your "qualification" in a mocking manner but not for my characterization of the "facts" that you presented as nonsense.
    You continue along the same lines and it is a waste of time to go round and round.
    I have presented the facts as they apply to the WETA and to my boat accurately and I stand by them 100%.


     
  10. Chris Ostlind

    Chris Ostlind Previous Member

    A New, Fun, Fast Trimaran

    Later this weekend, I'll be posting a more comprehensive take on a new trimaran on which I've been working. This new design comfortably fits into this discussion. It will offer a departure to the ideas being pushed here that fun, fast multihulls need to be equipped with excessive gadgetry in order to make a significant statement.

    Until tomorrow... here's a couple of images to stir the pot a bit and put all this back to boats that can be built affordably and enjoyed by everyone.
     

    Attached Files:

  11. Doug Lord
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    Doug Lord Flight Ready

    =====================
    Look forward to it ostlind-but don't forget the DETAILS......
     
  12. Chris Ostlind

    Chris Ostlind Previous Member

    I'll post exactly what I feel is necessary.
     
  13. Doug Lord
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    Doug Lord Flight Ready

    Pretty Pictures

    Oh boy, this is going to be good! Thats a hot picture but not worth diddly if you can't back it up technically......
     
  14. Chris Ostlind

    Chris Ostlind Previous Member

    Well, it's kinda like this, Douglas.

    There's plenty of the mandatory design and engineering oriented number stuff that has been run as a component for the boat you see in the renderings. Truth is, however, that I'm not going to post the bulk of the material here as it is not necessary on this forum in order to discuss the sailing aspects of the design. I'll post what is needed to get an understanding of the boat's function and nothing more. It's very much my intent that the members be supplied with enough of the data based info, as well as nicely executed renderings, so that they can allow their own creative capabilities to imagine a fabulous story. Making that connection with one's imagination is key to absorbing the potential of a given design. Without that connection, you might as well be designing can openers.

    Perhaps you feel a need to shove all these repeat number lists in our faces because you overly complicate your efforts and need to reassure yourself that somehow it all makes sense? The boat I am showing has no overly complex operational aspects and the form and function have been well-understood for quite some time. Forcing the members of this forum to constantly look at your particular design needs as an exhaustive list, Doug, does not make them especially viable, or interesting.

    You're going to have to get your pencils sharpened if you feel like it's necessary to complain about not showing all the data you expect as there is a mighty long list of world class designers out there who provide similar, basic, data derived support for the designs they show on their own websites. I gave you a list of some of these well-regarded designers in another thread. You should avail yourself of the opportunity to click on the supplied links relative to each designer so that you can see what a standard in the industry is and how it is represented. I don't feel a need to satisfy your call for the showing of repetitive lists.

    Whine all you want, but it's gonna fall on deaf ears, as I'm speaking to a much different audience than your singular expectations.

    Pretty simple stuff.
     

  15. Doug Lord
    Joined: May 2009
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    Doug Lord Flight Ready

    Here are two small tri's that are great small boats:
    ---
    12 footer by Kurt hughes- http://www.multihulldesigns.com/designs_stock/daysail/12_tri.htm

    LOA 12'
    Beam 10'
    Upwind SA 68 sq.ft.
    Weight 160lb (crew for calc below 175lb)
    L/B main hull= 5.14/1
    L/B ama = 11/1
    SA/D= 22.5/1
    W/SA= 4.92
    SA/WS=1.9/1
    =====================
    Marples 3m (10') tri http://www.duckflatwoodenboats.com/mainpages/gallery?KID=52
    Beam 8'
    SA 64sq.ft
    weight 150lb
    ++++++++++++++++++++++++++
    ++++++++++++++++++++++++++
    One thing immediately noticeable is that the main hull of both boats is a displacement hull with a quite low L/B-5/1-in the first one. So that limits the speed potential right off the bat and explains the small SA. Why have more SA even though there is ample stability when the power couldn't be used. It's a good solution for two fun sailboats.
    But I'm looking at another idea-much more power by flying the main hull, increasing SA and by using relatively small amas. These boats probably would not be able to generate enough speed to fly the mainhull using either foils or a planing ama-just wouldn't work. The only way that I can see is by having a much larger ama that would then suffer from the same problem as the main hull-too low an L/B ratio and/or too much wetted surface.
    When I say "problem" I am not saying there is a problem with either of these boats-they are great,fun boats! The "problem" is only theoretical when considering modifying either to fly the main hull. And the solution is simple: don't do it.
    But I can assure you that doesn't mean a 10-12 footer couldn't be designed specifically to be fast enough to fly the main hull and offer more room and more speed-at least theoretically. More to come.....


    To understand the Design Ratio's used above and to find the numbers compared with other boats check out Eric Sponberg's
    PDF below: (does not include W/SA=all up sailing weight in pounds divided by sail area in sq.feet-mostly a foiler or low resistance boat quick and dirty comparative ratio. Literally "sail loading": how many pounds does each sq.ft. of SA have to move?)
    --------------------------


    Check this thread for the really cool Maora 10 foot tri: http://www.boatdesign.net/forums/multihulls/maora-10-cool-little-tri-33528.html#post379050

    --------------------------
    Great video of WETA West Coast championship: http://www.youtube.com/watch?v=LKpiVZvu-a8&feature=player_embedded excellent shots of main hull planing!


    Marples 3M under sail, Hughes 12 footer -pix from sites above:
     

    Attached Files:

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