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sponson fins

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  • sponson fins

    just wondering thoughts on the fins on the inner sponsons coming up on the deck at the front of a c stock hydroplane. what do they do, would i lose any performance if i cut them down level with the deck?

  • #2
    It would be helpful if you also had pictures.

    Dean F. Hobart


    • #3
      Keeps the front end of the boat tracking straight down the straights because they direct the air straight back over the deck of the boat. You can cut them off and test and see how the boat reacts. You may have to mount new ones again or not or decide to experiment with one, usually on the right side if the right sponson is coming up going into the turns, it helps deflect air going into a turn to help prevent blowovers. Not that common on outboards of our size and speed. It helps to round off as many edges of the boat as possible to get smooth laminar airflow over the boat. Pointed, sharp edge surfaces create turbulent airflow at subsonic speeds. So rounding off the leading edge of the ramwing (start of the airtrap), sponson edges, etc. helps to prevent blowovers.
      Last edited by deeougee; 11-26-2017, 06:02 AM.


      • #4
        Do not cut them off. Tried it once, boat handled horrible.
        "Ask anyone, I have no friends. I do have some people that put up with me and mostly because they like the rest of my family"

        Don Allen


        • #5
          The only reason for me to cut them off is because there in bad shape. Here's a pic,


          • #6
            You could fab new wood ones and epoxy them on in the same location or make new ones out of plexiglass or any other material and attach them to the inside of the sponson if you have enough space to fasten them on.