Slide Rule for Fluid Dynamics - Pressure Distribution on Wing Sail ?

Discussion in 'Boat Design' started by mustafaumu sarac, Oct 20, 2018.

  1. mustafaumu sarac
    Joined: May 2017
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    Location: Istanbul

    mustafaumu sarac Junior Member

    Its a hobby or advanced hobby for me. I want to build a rigid wing sail for my boat. I want to know pressure distribution on wing. But I want to learn can a slide rule calculate this and which slide rule and where to learn how to do this specific calculation ? I want to build a model of the boat and wings are no longer than 20 inches. Let me exercise on model. Please shed light , thank you,

    Umut
    istanbul
     
  2. messabout
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    Location: Lakeland Fl USA

    messabout Senior Member

    If you wish to do some test pressure experiments on a model, then use the largest model that you can accommodate. A 20 inch model is too small unless you have some ultra sensitive instrumentation.

    When you use the term slide rule, I presume that you mean to refer to some sort of application that can track Thrust,differences in angle of attack, wind velocity, sail twist characteristics, and scale features of dynamic similitude.

    In fact there are very well researched and available papers for tests such as the ones that I presume are of interest to you. Explore the internet to find pertinent information that is already in place.

    Then there is this ............A rigid wing sail is not an easy way to sail. It is a powerful piece of force generating hardware but it is very sensitive to delicate trim angles and would be best used with elaborate electronic monitoring and analytical systems such as those used on the incredibly expensive control mechanisms of Americas cup contenders.
     
  3. mustafaumu sarac
    Joined: May 2017
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    mustafaumu sarac Junior Member

    Hello there , thank you for answer. I want to compute the pressure distribution map on small model with precalculator , predigital , precomputer technology , I want to make it with slide rule , or say slide ruler analog mechanical computing aid. All with hand calculation . I think wright brothers were using that technology and technology used until the 60s.

    I dont want to make test but simulation with hand calculation. Not only for boats but for boomerangs also.
     
  4. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    A slide rule is not difficult to use, I learned in grade school.
    However, calculating pressure point values on a wing could prove challenging.
    Good luck.
     
  5. gonzo
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    gonzo Senior Member

    Slide rules work fine for calculations, but you need to keep track of the decimals. They make use of logarithms for some operations. For example, to divide x by z, you subtract the logarithm of z from x and then get the antilogarithm for the answer. It can be done with tables too if you want to go math-antique.
     
  6. messabout
    Joined: Jan 2006
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    messabout Senior Member

    Old guy that I am, I still have a K&E log-log decitrix slide rule. I love that old thing and I still know how to use it. It is strictly a nostalgia piece from engineering school back in the dark ages.. But why would I want to use an antiquated slide rule when my $12 Casio fx 300 can do so much more than the slide rule, do it instantly, and do it with far greater precision? To add to my nostalgic bent, I still have a perfectly usable copy of Smoleys Tables Of Slopes and Rises. How many people out there have ever even heard of such a book?

    That said, I will add that I respect people who do things with old fashioned tools. We got to this stage of modern development on the backs of those old timers who made do with what they had. Many of them did superb work with old tools.
     
  7. fredrosse
    Joined: Jan 2005
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    fredrosse USACE Steam

    Back in the 1960s I used my K&E for three years while working at Electric Boat - General Dynamics, doing fancy heat transfer calculations. A great and complex tool it is! One thing that a slide rule gives an engineer is the proper perspective on tolerances and sensitivity of a calculated value, while an electronic calculator spits out an answer to 13 decimal places, and an inexperienced engineer does not get any idea about how sensitive his answer is to the input values. A slide rule inherently does this while you set the slide & cursor.

    When electronic calculators started coming out back then, a decent scientific calculator cost was a few of weeks of an engineer's salary. When someone purchased one of the fancy electronics, we would play a trick on them. I would say "The new electronic is nice, but my K&E is faster and more accurate" This would immediately get the dander up on the guy that had just dropped $600 on a HP scientific calculator, and then I would challenge him to solve any function, picked at random from any engineer in the office. Of course, the nearby engineer was in on the trick, and he would state some question that had an exact answer, like "What is the cube root of 125?" I would slide the cursor to the answer, and state the answer before the poor guy with the electronic could enter numbers on his machine. A good joke back then.
     

  8. mustafaumu sarac
    Joined: May 2017
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    Location: Istanbul

    mustafaumu sarac Junior Member

    Lets take the boomerang.

    Two asymmetric wings and success depends on knowing the pressure distribution on wings. I am not engineer , I am writing the experts told me.
    My math teacher died at high school and no advanced math , may be the polynom graphic.

    Now I am selecting the oldest technology to calculate pressure distribution on wings and trajectory of the boomerang.

    I read

    euler
    runge kutta
    and navier stokes can calculate this distribution.

    I know navier stokes is the hardest and I read runge kutta small cfd simulation codes done for ship optimization.

    I dont know anything about euler.

    And I heard potential flow from 60 years ago. But I dont know anything.

    Now lets find which is more suitable for slide rule ?

    I will ask more but let me cross the first problem.

    thanks,

    umut
     
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