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Thread: Wave speed

  1. #1
    Join Date
    Dec 2011
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    Western Puerto Rico
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    Wave speed

    Question about wave speed. Boating uses the term SOG, for speed over ground, to discount currents that affect speed (or knots) instruments. This question deals more with wave speed in the area that we surf in, as from takeoff, to shore, not open ocean.
    I'm curious whether wave speed is similar or different, and if so , how much, in regards to coastal areas or island reefs. Around here, our bottom is mostly flat rock and bottom depths are similar but not exactly the same. There are breaks that are deeper water and some are relatively shallow.
    I haven't surfed a coastal area in years, but it would seem from past experience that the wave speed toward shore would be slower than that of an island...because the wave is coming out of much shallower water, the coastal shelf ....?
    (no, I didn't google wave speed, I'd rather see experts thoughts here )

  2. #2
    Join Date
    Oct 2013
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    continental slope = friction = braking action = smaller/slower.
    for this reason when c-21 takes an add out about how good the surf is in labrador don't buy in.

  3. #3
    Join Date
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    The deep water wave speed, is where there is no action between the swells and the ocean bottom. This is any depth greater then half of the wavelength.

    So, when the wave goes from the deep water depth to shallower water, it will start to interaction with the ocean bottom and slow down.

    Also, wave speed increases as the wavelength (or wave period) increases.

    To answer your question of comparing island waves to mainland waves, yes in generally you are correct, because there is a lack of continental shelf to slow down the swells. But, often times we are not comparing apples to apples, as swells on the East Coast are generally smaller wavelengths (period), then many island locations. So, consider both factors - ocean bottom drag, and the overall wavelength (period).
    Last edited by SI_Admin; Mar 31, 2014 at 02:05 PM.

  4. #4
    I'm speechless.....

    The only way I judge wave speed is if I hear my leash humming in the water and my board start skipping, I know I'm going about 160mph! Give or take 10mph!

    Hell I've gone so fast all the wax melted off my board and my fins had burn marks on them!

  5. #5
    Join Date
    Nov 2009
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    in the grace of the most holy FSM
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    Quote Originally Posted by wavehog1 View Post

    Hell I've gone so fast all the wax melted off my board and my fins had burn marks on them!
    slowpoke. this is me on the regular:



    it's the real reason i don't use the stock plastic fins on my boards. they melt.

  6. #6
    Ya, you'll have to invest in a nice set of Al Merrick titanium, nickel plated Dane Reynolds series fins. They actually have little intake ports and a nano series of turbines and props mounted inside that suck in water and then jet it out adding 80% more thrust to your thruster! The two side fins pivot on macro titanium nickel plated kanootin pins! This allows for turns up to 3g's!

    That's all actually last weeks technology!!! There's a new set of fins just now hitting the market endorsed by Taj Burrow and though the technology is still secret and has been broken down yet its rumored to be that these new fins are going to be electronically retractable and there will be an app on your phone in which you can control them while you surf!!!