Scaling laws and foiling

Discussion in 'Hydrodynamics and Aerodynamics' started by tlouth7, May 14, 2021.

  1. tlouth7
    Joined: Jun 2013
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    Location: Cambridge, UK

    tlouth7 Senior Member

    Can they? If the foil top speed is fixed at ~50kt then the question becomes: is it an equal challenge for small and large boats to reach that limit? The smaller boat's foils and rig will be operating at higher speed/length (chord or span) ratio, is this a good or bad thing for the lift/drag ratio?

    Are we better at building large or small rigs with extremely high lift/drag ratio?
    CocoonCruisers likes this.

  2. Skyak
    Joined: Jul 2012
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    Location: United States

    Skyak Senior Member

    If you look at it from a wind over water speed record point of view there is no value in going bigger, only greater cost. But this case is unique in that it allows cherry picking of venue and conditions ie extremely high winds coming offshore with too little fetch for any wave development.

    If you are considering a craft that has useable speed in common venues then size comes back in play -not from theoretical advantage but from practical maters like waves changing the boundary limits of your optimization. In the real world you can't expect high winds without big waves. For a boat that is small relative to waves there are added complexities of ventilation and wave wind shadowing to say nothing of the potential energy change from gravity. It's a much more difficult and interesting problem.
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