Does water temperature affect fin performance?

Discussion in 'Surfboards and Surfboard Design' started by Roy Stuart, Oct 12, 2015.

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  1. Oct 12, 2015 #21
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    If the fin has a constand chord then it could be retracted into a slot.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  3. Oct 12, 2015 #22
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    um... math supporting laws of physics that govern the structural behavior of any polymer material molecular matrix says you're wrong.
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015

  5. Oct 12, 2015 #23
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014

    why? if you can make guider rails with coiled springs over them?
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  6. Oct 12, 2015 #24
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    besides, dude... aren't you asking about water temps? and smart money is that those 50 deg F of "extremes" you get between cold and warm ocean water don't make that big of a difference for structural integrity, aka torsion and shear stresses inflicted upon the above mentioned structure. hence the propositions of my designs, addressing those forces. fock.
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  7. Oct 12, 2015 #25
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    Sorry but we are talking about flow conditions not fin flexibility... and the maths supporting that doesn't lie either.

    What you have responded with is essentially a red herring.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  8. Oct 12, 2015 #26
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    Yeah dude, but this analysis has nothing to do with structural integrity or flex.

    It's about changes in flow behaviiour due to viscosity of the liquid.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  9. Oct 12, 2015 #27
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    Why?... in order to reduce wetted surface area as speed increases.

    Perhaps you meant 'how?'. In that case one answer is that a simple motorised mechanism (without springs) could be used to lower and raise the fin.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  10. Oct 12, 2015 #28
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    DUDE!

    salt water :

    Dynamic viscosity . . . . . . . . . .


    1.88 × 10^−3 Pa s @ 0 C

    1.08 × 10^−3 Pa s @ 20 C

    Kinematic viscosity, ν . . . . . . . . .


    1.83 × (10^−6)(m^2)(s^−1) @ 0 C

    1.05 × (10^−6)(m^2)(s^−1) @ 20 C

    what are we even talking about here?
    if you're gonna say "oh thats almost twice the viscosity) i'll assume you've gone full retard because, yes, that's 10 to -3 and 10 to -6
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  11. Oct 12, 2015 #29
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    if surfers wanted anything motorized to do with waves they'd be riding jet skis.
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  12. Oct 12, 2015 #30
    DonQ

    DonQ Well-Known Member

    1,685
    Oct 23, 2014
    Oh, man I need a heated towel...
     
    DonQ, Oct 12, 2015
    DonQ, Oct 12, 2015
  13. Oct 12, 2015 #31
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    I haven't said anything of the sort.

    The point is that the change in water viscosity over that temperature range causes a significant change in the Reynolds number for any fin, and that the resulting differences in foil behaviour are also significant and well researched.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  14. Oct 12, 2015 #32
    DonQ

    DonQ Well-Known Member

    1,685
    Oct 23, 2014
    Interested to see what develops Roy. Please keep us posted!
     
    DonQ, Oct 12, 2015
    DonQ, Oct 12, 2015
  15. Oct 12, 2015 #33
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    Here's the example which I used in the original post ( http://www.roystuart.biz/2015/10/does-water-temperature-affect-your.html) for a fairly typical single fin foil:


    RAF 27 AIRFOIL

    [​IMG]

    Water temperature 20 degrees C
    Velocity 12 m/s 26.843 mph 43.2 kph
    Chord width 0.06 m 0.19685 ft 2.3622 in
    Kinematic Viscosity 9.7937E-7m2/s 1.054e-5 ft2/s
    Reynolds Number 735,166 (Red line on graph)

    Water temperature 1 degree C
    Velocity 12 m/s 26.843 mph 43.2 kph
    Chord width 0.06 m 0.19685 ft 2.3622 in
    Kinematic Viscosity 1.6438E-6m2/s 1.769e-5 ft2/s
    Reynolds Number 438,009 (purple line on graph)

    [​IMG]

    [​IMG]

    Thanks to airfoiltools.com.
     
    Last edited: Oct 12, 2015
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  16. Oct 12, 2015 #34
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    why do you have different number for kinematic viscosity?
    you need salt water.
     
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  17. Oct 12, 2015 #35
    EMazzSpicoli

    EMazzSpicoli Well-Known Member

    182
    Jul 1, 2015
    How many people here or anywhere surf good enough where the variable of water temp's effects on fins even matter? C'mon Ruoy. You're just tryna rip people off now and capitalize on them being willing to buy something that makes them surf better.

    At what water temp does your sheep's ballz retract into its stomach?
     
    EMazzSpicoli, Oct 12, 2015
    EMazzSpicoli, Oct 12, 2015
  18. Oct 12, 2015 #36
    Towelie

    Towelie Well-Known Member

    2,864
    Nov 27, 2014
    Towelie, Oct 12, 2015
    Towelie, Oct 12, 2015
  19. Oct 12, 2015 #37
    JTS

    JTS Well-Known Member

    231
    Feb 21, 2010
    Are you going to spam all the surf forums with this sh1t Roy ?
     
    JTS, Oct 12, 2015
    JTS, Oct 12, 2015
  20. Oct 12, 2015 #38
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    BS to you, I'm not selling anything on the basis of this analysis.

    My take on on it in the first instance is that if one is inclined to reduce fin size as much as possible, one will be able to do so (at least with regard to the fin chord) more so in warm water. If for example one has fins which are just big enough to do the job without stalling inconveniently in warm water, they might not do the job in much colder water and an increase in chord length or 'fin base' might be required.

    The magnitude of the difference over a large range of water temperature is similar to that which occurs over the normal range of surfing speeds... and it's already common knowledge that smaller fins can be used at higher speeds so i think that the application of this theory is valid.


    .

    .
     
    Last edited: Oct 12, 2015
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  21. Oct 12, 2015 #39
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    It's neither sh8t nor spam, it's research which is being shared for anyone who is interested... this group doesn't have to include you.
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
  22. Oct 12, 2015 #40
    Roy Stuart

    Roy Stuart Well-Known Member

    1,514
    Jan 27, 2013
    The relative difference is the same for salt water.


    .
     
    Roy Stuart, Oct 12, 2015
    Roy Stuart, Oct 12, 2015
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