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  1. #85
    Junior Member
    Join Date
    Mar 2018
    Posts
    3
    You are right about the importance of this angle but I didn't mesure. I was on vacation there ) From the pictures you can see that the bottom was flat . I add a picture when installed on the board, there is an angle....
    .Click image for larger version. 

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  2. #86
    Member
    Join Date
    Mar 2018
    Location
    Kitchener, Ont.
    Posts
    50
    So look at this fin and imagine it without the bottom wing. Would you seriously buy a fin that looked like that - a trapezoid 22 cm. wide and 31 cm. deep? With the back edge slanting forward?

    Let's take just one function of a fin on a freeride 130 l. modern board. The fin crabs into the wind thus making a foil shape out of its symmetrical shape and providing sideways LIFT on the windward side. This lift helps with early planing and more importantly it allows the sailor to stand on the windward edge of the wide board, in the footstraps, hiked out over the water, allowing the sail to be there also, and allowing his body weight to hold down the sail.

    The fin as constructed above has a 22 cm. chord instead of an optimal maybe 10 cm. chord. Remember, a low aspect ratio has the best lift to drag. The lift provided at the bottom of the board does not have as much leverage to tilt/lift the board as sideways lift say 50 cm down on a long fin. The flex and twist necessary will not happen on the above shape. And finally, the long chord leads to spin-out,not prevents it. I have a HUGE weed fin that I use a lot and it spins out when I get overpowered, BUT after fitting and overlapping the tuttle box, it quickly reduces to 12 to 13 cm. chord.

    I keep saying the same thing: "Sticking a wing on a fin does not allow that fin to magically abdicate all its fin responsibilities or physics!"
    Last edited by RazeR69; 2nd May 2018 at 04:15 PM.
    There's no ox so dumb as the orthodox.

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