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  1. #22
    Senior Member chrispavlo's Avatar
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    Quote Originally Posted by Navegante View Post
    Sun of a gun!!!!
    Murder!!!!!
    not in circles like the boardlady, but in nose to tail direction
    Click image for larger version. 

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    Last edited by chrispavlo; 20th April 2018 at 06:40 PM. Reason: pic

  2. #23
    Senior Member chrispavlo's Avatar
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    Quote Originally Posted by Wing 11 View Post
    Is it too much rough?
    I'm dry sanding both my fins and board bottom with 80 grid for more than decade now and I'm very happy with it

  3. #24
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    My guess is that shark skin, etc, has evolved to be efficient at lower speeds than a planing windsurfer.

  4. #25
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    The fastest sharks are measured at 50kph. Sharks are covered in hard shaped scales called dermal denticles. It is thought their careful alignment, chemical makeup and very specific shape help to reduce drag. The exact reasons are still not fully understood. One thing of importance to this thread is that the effect only works when the skin is allowed to flex and not if kept rigid. As the skin flexes and twists, the denticles bristle up 30-50 degrees which research is only just beginning to understand even on a basic level. Simply roughing up a surface can even have a negative effect. There are many highly knowledgeable teams at universities around the world studying this and utilising various super computers, running complex computational fluid dynamics calculations on a daily basis. Even with all this going on, they are only beginning to get a tiny percentage of an understanding into it all. So keep buffing your board in whatever way makes you happy, safe in the knowledge you really have no clue.
    Last edited by phill104; 19th April 2018 at 09:43 PM.

  5. #26
    Senior Member chrispavlo's Avatar
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    Quote Originally Posted by Wing 11 View Post
    some sources said that mako can swimm up to 60mph ..

    problem is that windsurfing community does not have money to search new stuff/tehnology like Formula 1,Nassa etc..if they have money they could test race sail in wind tunnel etc,develop wing/hard sail etc...
    but it doesnt metter,because friction drag in wsurf have so small impact..
    windsurf development is not rocket research - all you need is some experimentation with different bottom treatments - for me it was comparing wet sanding against dry sanding and various granularity.
    Click image for larger version. 

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    friction drag is maybe a bigger factor one might think..
    that's why foil boards are very efficient with much smaller sails or at very light winds.
    Last edited by chrispavlo; 20th April 2018 at 08:59 AM. Reason: pic

  6. #27
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    "some sources said that mako can swimm up to 60mph .."

    Yes, maybe, but animals are efficient at doing stuff they do 99% of the time. Sharks swim slowly, Cheaters sleep! ...Windsurf boards sit in sheds & vans, sadly.

  7. #28
    Senior Member Gorgesailor's Avatar
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    Quote Originally Posted by phill104 View Post
    The fastest sharks are measured at 50kph. Sharks are covered in hard shaped scales called dermal denticles. It is thought their careful alignment, chemical makeup and very specific shape help to reduce drag. The exact reasons are still not fully understood. One thing of importance to this thread is that the effect only works when the skin is allowed to flex and not if kept rigid. As the skin flexes and twists, the denticles bristle up 30-50 degrees which research is only just beginning to understand even on a basic level. Simply roughing up a surface can even have a negative effect. There are many highly knowledgeable teams at universities around the world studying this and utilising various super computers, running complex computational fluid dynamics calculations on a daily basis. Even with all this going on, they are only beginning to get a tiny percentage of an understanding into it all. So keep buffing your board in whatever way makes you happy, safe in the knowledge you really have no clue.

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