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

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

  1. Doug Lord
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    Doug Lord Flight Ready

    See the detailed specs of this proposed boat in the MPX-11 thread. They are being updated and refined almost every day. Note too, included is the first preliminary weight calculation in detail. Enjoy!
     
    Last edited: Jul 13, 2010
  2. Chris Ostlind

    Chris Ostlind Previous Member


    That's where the DESIGN PROCESS comes in, SA. In spite of your well-meaning question, you've simply failed to apply the long accepted, Cube Rule for Vanishing Dead Weight (CRVDW), to the clever realities of this inspired genius concept. This is the closely guarded designer tool in which the artist continues to apply the CRVDW coefficient until the offending weight simply goes poof!... never to bother the visionary again.

    Go back and look at how many times the massaged data has been listed. Take note of the intriguing use of color in the presentation and the number of times that the exact same post has been put forth as new material. If you are really reading this thread, then you'll know... but then, you already knew that.
     
  3. science abuse
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    science abuse Junior Member

    I really don't care enough to spend my days pouring over data for the simple purpose of arguing on the internet. ;) The question was a question because their might actually be a reason for the hull to be there, thus not being dead weight, I'm interested in hearing the fellow out. In my case, the dead weight isn't dead weight because I'd have all my stuff stored there. If I'm taking multi-day excursions, I'll need more than just a pocket-flask of booze. ;)

    Additionally, if you're overpowering the boat, you'll need a very stout mast step, which will be easier to come up with if you've got a central hull to sink it into. I'd imagine that a 19ft spar with a dude or two hanging off of it will appriciate all the help it can get.

    Also, if this is going to be a foiler, the central hull gives you a place for a third foil, affording you tri-pod stability.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    ===================
    SA, the righting moment is calculated based on the center of gravity of the boat and based on the CG of the crew. So on an 18 footer, for example, the CG of the hull when flying the main and windward hull would be approx.8.75' from the center of buoyancy of the lee hull. The CG of the crew is 8.75 + 9 + 3' from the center of buoyancy of the lee hull.
    So, assuming very small amas and a weight of 400lb and two crew at 175lb each the RM is:
    8.75 X 400 = 3500ft.lb.
    20.75 X 350= 7262ft.lb.
    TOTAL RM= 11,062ft.lb.

    An 18' cat about the same weight:
    2 175lb crew at 7.5+3'= 3675ft.lb
    397 at 3.5' from center of buoyancy of lee hull-1389.5 ft.lb.
    Total Cat RM,two crew on trapezes= 5064ft.lb
    ----------
    So the square tri with two on the trapeze has about twice the RM of a cat the same length. Check out the F18 vs 18' tri thread for more detail
    and a comparison of an F18 with a tri using only part of this power.
    The key to the 18 and this little boat is the use of "foil assist" hydrofoils and very small ama's....Hope this helps....
    PS- as you supposed the main hull allows the amas to be very small while supporting the foils and large rig.
     
  5. Chris Ostlind

    Chris Ostlind Previous Member

    Well, I hope that there's a reason, though it looks like the same end purposes could be accomplished with a central, structural pod on a cat, rather than a full hull. Heck, it could even be designed like the boat over in Thailand and have the pod slide back and forth as desired.


    True, but an immersed hull seems to be a good bit of weight for that purpose alone.



    Actually, SA, I think that this boat is destined to be a four foiler design from all the hastily prepared drawings we have seen. I'm not sure of the precise thinking behind all of this when the noted foil guru Dr. Sam B, has already proven many times that a three foil boat is pretty darn cool. In fact, his newest hotrod foiler, The Osprey, is once again, going to have three foils. http://sites.google.com/site/hydrosail/ But, hey... why do with three when you can just put on another and take it to new places of complexity and expense?
     
  6. Doug Lord
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    Doug Lord Flight Ready

    =====================
    I don't blame you-it can get tedious. The problem is that for a small boat like this, using a concept never before tried, it is essential to have numbers that add up to the viability of the concept. No numbers=no concept. It is absolutely essential, in an exploration such as this, to be damn sure it all adds up and I think I have proved that. But at the "cost" of a lot of detail and a lot of numbers....
    ---
    Note this boat uses a main hull that is over twice as large as its ama's. Very small planing amas are a key to this concept and the larger main hull facillitates that.
    Also, the MPX-11 uses only two hydrofoils-one on the daggerboard and one on the rudder. The foils give a great deal of pitch stability and, in conjunction with the wand connected to a flap on the main foil, control the angle of heel of the boat. The wand altitude control system is adjustable and will keep the boat sailing at a preset angle-regardless of actual crew weight within the range of 120-to around 240lbs. crew weight. It also allows the boat to fly the main hull much earlier than it would otherwise.
     
  7. science abuse
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    science abuse Junior Member

    Ahh, so your static bouyancy comes from the main hull, as the Amas would not be large enough to do it on their own? Provided everything gets up out of the water and you're left with the foils/single narrow ama, the logic is sound.

    You spec'd out 2ft wide Amas, though. Wouldn't 10" or 12" with another foot or two of length lower your drag significantly, whilst still provinding the force you need? I'd also think that 57" would be much wider than needed for the main, if all you're hauling is bodies. ;) 11 x 48 are the dimensions of my stubby little Snark, which is a mono capable of hauling 400lb worth of adults (very slowly). If your crew are indeed 175 pounds, why not narrow the beam down to 36"?

    I would disagree, only in that a prototype out on the water mutes critisism much more effectively. ;) Being an engineer myself, I've seen a great many things that look great on paper fail in real life (6 Stroke Engine), while things that look utterly rediculous in-the-math have had great success (Rotary engine). You really never know until testing is complete and nothing is on fire. ;)
     
  8. Doug Lord
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    Doug Lord Flight Ready

    -------------------------------

    Right.
    The ama/ mainhull beam is directly related to the fact that they are both planing hulls. In most trimaran designs high L/B displacement hulls are used because, generally, they have less resistance at a given weight.
    That can't be done at this size because skinny hulls would not support the weight at a high enough L(length)/B(beam) ratio. That is why the other tri's in this size range are slow and use very small sail areas. This is another area where studying the numbers/ratios might help. See post# 22, page 2 of this thread.
    This boat is designed to be sailed with both amas clear of the water until a boat speed around 6-7 knots. After that the ama can plane easily and take much more load.And the foils kick in around this same speed... It is a unique concept that I think will work well.
    ---
    See the second post(#47) on this page. Max crew weight about 240lb...
     
  9. Chris Ostlind

    Chris Ostlind Previous Member


    So, let's get this right... You're going to stick an absolutely huge rig on a tiny, form stability deprived boat and expect the skipper to sail it with the amas clear until it gets to 6-7 knots? A boat, mind you that is outrageously sensitive to crew positioning, where even the smallest of movement is going to be a huge shift in ballast location?

    Good luck with that.

    I think this boat is going to be crashed a lot by even the better sailors on this planet and for the everyday guy... pretty much impossible. That does not make for a recipe that compels folks to come back over and again for the promised thrill.


    As to the seemingly endless lists thing...

    What would be good, Doug, is for you to cook-up your numbers, as best you can and post them once and not over and over. Keep in mind the audience to whom you are speaking. Not everyone is a numbers goof and for the most part, that is your biggest audience share. For the guys who just have to have their daily meal of numerical data, suggest that they write you off-list.

    Go back and look at how many times you have posted the same stuff and merely made tiny, incidental changes that are difficult to spot even when you get all colorful. That stuff gets old, my friend. Why not speak to your latest epiphany with words, save up the repetitive postings for when you have five, or more, significant changes and keep the flow of the conversation clean and to the point?

    Pretend that you are making this presentation within a corporate environment where you are going to get the whole gang together for one session of having changed one tiny thing. I say one session, because nobody is going to come back for another meeting of that sort with their busy project schedules. Ask our guy, SA, if he enjoyed laborious meetings for what amounts to zip.

    Beyond that, SA has told it to you as succinctly as it can be without getting rude. Go build it if you think it can do what it's purported to do. The numbers are merely symbols on a piece of paper until you do.
     
  10. Paul B

    Paul B Previous Member

    No, it isn't.

    Even Lord this time admits this is not something he ever expects to design or build.

    So this whole thread is about a jumble of numbers that the origninal poster has no intent of ever going forward with. The jumble of numbers represent something that no one seems to be asking for: a solution in search of a problem.

    What is really represents is Lord's frustration with finally feeling fully exposed after once again being unable to produce a design for, or build, "the most important boat" of his "career".
     
  11. Doug Lord
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    Doug Lord Flight Ready

    Comfort, Ease of Sailing, Blistering Speed

    I believe that the only way progress is going to be made is to think -to use the old cliche-"outside the box". Progress in high power trimaran design has been woefully inadequte for boats 18' and under. New thinking and new technology applied in new ways can change that.
    As proven in very detailed comparisons in the F 18 thread a "beach trimaran" can offer , more power, more comfort and an easier to sail high speed boat than can a cat. Applying some of the things learned in researching that thread-carefully- to the 10-14' boats in this thread is an interesting challenge given that -like in the 18 footer- there is nothing, absolutely nothing available now that uses the full range of state of the art modern technology on a trimaran design in this size range. I will propose some solutions that take full advantage of this technology as I did in the F 18 thread....See the detailed specs for one version of an 11 footer(MPX-11) that fits the thread concept to a tee posts 46 & 47
    The basic theme of the 18' tri is summed up like this:
    More Comfort- More Speed- Wide crew range(singlehanded or doublehanded with MAX power)
    I want to see if that theme can be applied to boats within the range specified in this thread-and to what extent it may or may not be possible.

    This is certainly worth reading for anyone not familiar with it:

    While this is about catamarans from an interveiw with Martin Fischer, I think it applies to ALL multihulls-most particularly a trimaran that could accomplish the challenge of this thread:

    CS - Is possible to see in the future a stablished racing class of foiling beachcats ?
    MF: Yes, I am absolutely convinced that foiling multihulls are the next step. The challenge is to make them reliable and easy to handle. I am currently working on putting an A-Class on foils. First tests are very promising. I start flying the boat, also it is not very stable yet, but I think we will get there.

    CS- I've heard from Landy in the A-Class, from M20 pics and reports and from Macca in the Nacra F20 how they are flying with curved boards, so slowly we are going in that direction, not full hydrofoils of course, but is the future in your view (flying beachcats Moth style)?
    MF: Yes, I have here in New Caledonia an A-Class with curved foils. The boat works nicely but it is not yet fully air-borne. If everything works according to plans I’ll have a flying A-Cat before the end of the year.


    The full interview is here: http://catsailingnews.blogspot.com/2010/05/cs-interview-martin-fischer.html
    ----------------
    6/29/10 PS- take a look at at the paragraph I added to the first post of this thread.....
     
  12. Doug Lord
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    Doug Lord Flight Ready

    =================
    Is that right? Another twist of the truth from our resident non-designer and non-boatbuilder.
    I said this in a fit of reality-but it is not what you said I said:

    Well, I guess we know what you WON'T be doing:

     
  13. Gary Baigent
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    Gary Baigent Senior Member

    Doug, you're down to 10 feet or so now, why not go further, there will be a proverbial gold mine of development hidden away down there, why not 6 feet, (why not, the aussies used to have 3 man 6 foot hull skiffs, with long bowsprits and main boom overhangs, you could also do that) or hey, maybe you could make a 3 foot model. Here we've run the whole gamut, the complete circle, from paper to mountains of postings and yet more figures to model, then to 60 foot postings and then down, down to 20, then 14 to 10 - one more step and back to model. There is a satisfying completeness there, kumbaya.
     
  14. Doug Lord
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    Doug Lord Flight Ready

    ===============
    Thanks ,Gary-I've already done 6' & 5'-and it was great sitting under a tree sailing them ,too! Or showing them to Dr. Sam.
    Speaking of "the complete circle" hows the Roto-Tri doing?


    Flyer cubed-Upper left corner of the picture on the doc: Dr. Sam....
    And the inimitable F3-the Worlds First Production RC Sailing Foiler:
     

    Attached Files:


  15. Paul B

    Paul B Previous Member

    Gary, this is all your fault. Just as the brass plaque capped the "build" of the last project you had the nerve to show photos of an actual build in process.

    That fried the wires and this next jumble of numbers feverishly appeared.

    This too will run it's course and soon it will be on to the next jumble of numbers. No design will ever be done, no "world beater" will ever be built.

    We should start a thread compiling all the self-over-hyped "designs" from this "designer". It is easily in the double digits now...
     
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