About inclined underwater hull form

Discussion in 'Hydrodynamics and Aerodynamics' started by fredschmidt, Feb 18, 2012.

  1. fredschmidt
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    fredschmidt Naval Architect

    Daikiri

    We only saying statically, we do not speak in hull waves (dynamic form), but it's still a good start.
     
  2. Eric Sponberg
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    Eric Sponberg Senior Member

    This is exactly the wrong way to think. You cannot bring new knowledge to naval architecture if you don't speak the proper language and have the proper definitions. Otherwise all you have is supposition, inuendo, and conclusions that conflict. A person in Russia or Thailand or Japan would not be able to understand the results from someone in America or Britain or France. The language and the definitions have to make consistent mathematical sense.

    If you want to bring new knowledge to naval architecture, do it in the proper scientific way. Isolate the problem to its barest components and test each variation one step at a time. Collect the data in a consistent manner, and then you will have something useful to analyze, and that will lead to concrete solutions, conclusions, and the advancement of the science of sailing that anyone can understand. Anything less than this is useless.

    I am trying to help. It is an interesting hypothesis that is worthy of continuing research. And the reason I suggested that a Master's degree thesis is worthy of this is because all this testing is going to cost money--lots of money--and a good masters engineer generally has time and some university resources to devote to the problem. Personally, I could not do this research myself because I don't have the money to throw at it. If someone wanted to throw money my way, I would be happy to consult. But who has tens of thousands of dollars to throw at a pretty much purely academic question that likely would not lead to any economic return--that is, the money spent will not result in any kind of a payback. So, it is to the universities that would be a likely alternative. I dare say first, a good library search would probably reveal clues to prior art--we can't be the first people to think of this question on the effectiveness of chines--who has done this before and what can we glean from that.

    Bottom line, language has to be consistent and testing would have to follow a proper scientific method if you want to advance the art. Commercial interests are not going to pay for this, so it will mostly likely have to come from academia.

    Eric
     
  3. fredschmidt
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    fredschmidt Naval Architect

  4. daiquiri
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    daiquiri Engineering and Design

    Eric is saying that we need numerically-backed proofs of your theories, Fredschmidt.

    I personally think that there might be a small increase in lateral force due to the chine (and not due to the waterplane shape) effect, but that it is way smaller than you believe. And if that is correct, the question is - what is the viscous and induced drag penalty for this increase in lateral force? Is it bigger or smaller than the decrease in the induced drag of the keel, due to a consequent hypothetical reduction of the keel AoA?

    That's what should be investigated, in an orderly and scientific manner.

    Cheers
     
  5. fredschmidt
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    fredschmidt Naval Architect

    Eric

    I would not answer his claims not to create controversy about technical words, which completely escapes the theme of the thread , that from the beginning you rejected. But I think it is a response by the way you talk.

    Shipbuilding is not made ​​only of CFD, vector analysis, etc.. It is made with heart, with love, dedication.

    And with age (68) I learned that the naval art is also made of intuition, with excellent results, as seems to be the case Cheinz, by Jeff, an excellent RC sailboat.

    If I talk to people without Master Degree I try to speak as they speak, one would assume that people with Master Degree must understand, for their knowledge.

    I brought to this forum suspicions that deserves to be studied, and it has merits, the more you wrestle to discredit me criticizing my verbiage, the criticism is too small for the big fact. If proven will give a good indication for those who design boats.

    You speak in money, money, money. I love to speak about boats and boat design. I think you do not understand it.
     
  6. fredschmidt
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    fredschmidt Naval Architect

  7. daiquiri
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    daiquiri Engineering and Design

    Sorry if I defend Eric S. here. I swear I'm not payed for that, it's just that Eric imo is not the person you have depicted there. You say he talks money - well, he earns his living by designing boats and definitely knows the importance of money in the world of naval architecture.

    You have this idea about waterplane shape and chines. Ok, but at some point an idea either becomes an action or remain just words... You have exposed you idea several in this thread and, at least for me, it is pretty clear what you mean. Now it's time to back the ideas with stronger facts. A testing is required, if it wasn't already done by someone. It is time to try to demonstrate your idea, either by conducting proper and fair comparative tests between two or more models (like Eric has described in detail) or by handing it over to an institution which can perform the research, if interested.

    The remaining opton is to keep talking forever about shapes, foils, lift and faith, but for what purpose? I also have reasons to believe that red cars are faster than blue ones, but unless I present you some empirical proofs of my theory, will you trust me or waste your time trying to change my opinion? Or will you at some point just say - ok man, demonstrate me that red cars are faster than blue or yellow ones, or else we better change the topic... Sorry for this little pun, it serves to show a difference between beliefs and facts (which you surely already know well). ;)

    As I said previously, your theory about chines might have some merits, but until now it was all a matter of your belief vs. someone else's belief. It's time to find a way to check the beliefs against numbers, facts, articles, comparative races, etc. If you have some ties with persons from academic institutions, universities, etc, the time is right to make that phone call. ;) I personally would be interested to see the results of the tests.

    Cheers
     
  8. fredschmidt
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    fredschmidt Naval Architect

    Mr Daikiri

    "The remaining opton is to keep talking forever about shapes, foils, lift and faith, but for what purpose? I also have reasons to believe that red cars are faster than blue ones"

    Ok I understand Mr Daikiri its censorship and wants me shut up, okay, I'll do it. I'll find another place to talk about boats, exchange ideas, learn from those who do not have Master Degree and Master Degree who has, because many people do not have Master Degree, but has insights, they often speak louder than words techniques or color of car . I think now I realize the way that you and Mr Eric want to give to the Forum. I prefer the style of Mr. Doug Lord.
     
  9. daiquiri
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    daiquiri Engineering and Design

    Hey no, you have got it the wrong way! This is an interesting thread and I would really like to see the results of a sea trials. Like I said, there might be some merit into your idea about chine effect (if the chine forms a hard enough turn for the water flow, I will add). The point is - now it would be necessary to find a way to get beyond the plain idea, and to verify your suspects in a measurable way.
    There's no need or reason for you to feel offended.
    Doug Lord is a man of action, and sure has a lots of knowledge in his field (foils & co.). I think he would just make two model boats, one with chines and one without, and check out what happens. ;)

    Cheers
     
  10. Eric Sponberg
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    Eric Sponberg Senior Member

    Fred,

    First, I am sorry, I do not mean to offend. I do not mean to discredit you. I agree with you--your ideas do have merit, and I would love to know the truth about the matter. So, where do you go from here? I brought up the ideas about how to do proper research so that the questions and factors can be properly identified and analyzed, with the results to be understood, useful, and acceptable to anyone, universally. If you don't agree with that method, fine. Then what do you propose to do to answer your own questions?

    By the way, I talk to Doug Lord on the phone all the time. He is very intuitive and has some marvelous ideas. Yet, he always tries to get the terminology right and to isolate the problems and questions he raises for proper analysis. But like all of us, he and we have little money to devote to these kinds of research efforts. And, unfortunately, it takes money to do that.

    So, your hypothesis remains: Do sailboat hulls provide lift in and of themselves to windward, and do chined hulls do this better than round bottom hulls? How are you going to find out if that is true?

    Eric
     
  11. Earl Boebert
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    Earl Boebert Senior Member

    Well, here's a crackpot scheme I came up with to research such matters. Make a model yacht hull of the desired shape and mount on it one of the ducted fans the electric model airplane guys use. The idea of using a ducted fan is to avoid the effect of propwash on the hull, although this may not be an issue.

    Put the fan on a servo-controlled rotating base such that the center of the fan is at the geometric CE of the sail plan. I know this isn't ever the actual CE but you have to start somewhere :)

    By rotating the fan and varying its thrust under radio control you should be able to generate thrust, leeway, and heeling vectors that approximate the forces generated by the sailplan. Or not. But that's why we try things.

    Put a flashing light on the hull for a clock, go to an indoor swimming pool with a video camera dead astern, let 'er go and see what happens.

    I never went any further with the idea because every time I get the opportunity to build a model yacht hull I put a rig on it and go racing :) But it might make an interesting Science Fair project for some high school student.

    Cheers,

    Earl
     

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  12. fredschmidt
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    fredschmidt Naval Architect

    Jeff

    I can give you a great amount about hulls providing lif, and very good lift, but I will mention only one (it seems that many here do not know the boat) - Hobbie Cat - do not have keel.

    Naturally we not want to produce hulls like Hobbie Cat, that 'has two hulls because we (still) can not do hulls the that change form according to the tilt of the boat.

    The hobbie cat hull only produces good lift because the hull waterlines are foils (although great connoisseurs of naval architecture can not see it, the waterlines are foils). However, with the help of the chine or of a well designed hull we can turn normal waterlines on foils appropriate to do so (the case of Star) when the hull heeling.

    I want to thank you very much, because even though contrary to my opinion, your opinion led me to think more about it in order to bring you my thoughts more accurately. At my age I've found that casual conversation and not too technical (sometimes much better than master degrees opinions about car colors) but with insight and practical knowledge is excellent, because it opens the doors of curiosity and intelligence. Like brainstorm to create ideas. But persons with much hurry do not understand this.

    I wanted to tell you that I found your Cheinz a wonderful boat and would like to see their inclined waterlines :), I only do not bought one to use in IOM Brazilian championship because I do not have much money to do it, because for me, money is nothing.

    Venture to say that in the hand of an excellent skipper, like our Pedro Stier or Dennys Astbury, he would make a great job to Britpop! :)

    Cheers
     
  13. fredschmidt
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    fredschmidt Naval Architect

  14. daiquiri
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    daiquiri Engineering and Design

    It me it looks like your conclusions seem to take into account only opinions favorable to your conclusions. ;)

    Mikko's observation on the difference between VPP prediction of the Star-class upwind characteristics and actual upwind characteristics can be due to several factors. Two things which immediately come to my mind are the suitability of the used VPP for the particular shape of the Star hull and the difference in the shape of the keel assumed by the VPP and the one used on a sailed boat. Are the heeled hull shape and coefficients (apart the chines detail) modeled correctly in the VPP? What hull model data was the VPP based on and can it be used for analysis of Star-class boats? Things which have to be explicated before jumping to the conclusions.

    I believe that you have been given argumented opinions against your foil-like-shaped waterplane lift theory, but you have completely ignored all of them in your article and have cited just the opinion which fits favorably into your theory. That's an emotional and non-rational approach to the problem. It won't let you arrive to any really useful and physically coherent conclusion. I see the title "Naval Architect" under your nickname. That title (if it is your actual title) is a commitment to the scientific approach to boat design and analysis - not exactly how you've dealt with this interesting thematic so far, isn't it so? ;)

    Sorry for these critics, but there's really need for a more serious investigation and fact-based analysis before jumping to the conclusions - and that too has been said several times in this thread.

    Cheers
     

  15. Mikko Brummer
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    Mikko Brummer Senior Member

    Daiquiri,

    I agree - my Star example should not be taken as proof of the superiority of chines vs. no chines, or proof effect of asymmetrical waterplanes. It's just an observation. But I quote myself in an earlier post:

    "I tend to disagree - the hull is not insignificant as a lift producer. Look at my post #43 in the wing keel-bulb keel thread From winged keel to bulb keel. In the simulation, the hull produces one third of the side force, or half that of the keel (rudder lift excluded). It's mostly due to the keel/hull lift transfer, as can be seen from the numbers when the keel fin is omitted. As for the drag, look at the numbers with and without the fin, it only rises about 15% while the lift is doubled when the fin is under the hull. But of course, this is just a simulation, and not even very complete as such, since the free surface effects are neglected.

    Including the free surface effects could make the hull even more signicant, or at least more efficient... As the boat is heeled, the keel root gets close to the surface and makes a wave. So there is a lift induced wavemaking drag, both for the keel fin and the hull. Here, the hull is at a much better position than the keel fin: For wavemaking, the Froude number gets significant, and the long hull has a much, much smaller Fn than (especially a narrow) keel fin. Thus, the hull may not be at all that inefficient in its lift production. You may also want to read the post #76 in the same thread."

    I challenge you and Eric (and others) to read carefully the 2nd paragraph. Even this is pure speculation, but it could be a reason for the hull to be more important in the sideforce equation than for instance a simple airplane derived approach would suggest.

    What Fredschmidt writes about the effect of a chine above waterline at zero heel vs. under water when heeled makes sence to me. On the other hand, in the case of his model boat, which already has a huge keel in both depth and area, it would seem a little surprising the hull would be an important factor in sideforce generation. Unlike in the Star, for instance, or a more old fashioned, deep canoe body hull with rather a shallow keel.

    Then again, in certain dinghy classes like 505s and int'l 14s, the gybing centerboard re-surges from time to time... it aligns the hull with the direction of the motion of the boat, leaving the centerboard to take the sideforce alone. But it has never proven any faster than a conventional centerboard arrangement, I'm told.
     
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