How do I add strakes

Discussion in 'Boat Design' started by c4carpetcare, Jun 14, 2013.

  1. c4carpetcare
    Joined: Jun 2013
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    Location: Ocala fl

    c4carpetcare New Member

    I am in central Florida. I want to install lifting strakes on my boat. I have been searching threads and the Internet for a source. Where do I buy them and who installs them.

    I have a 20' sylvan pontoon with a four stroke 60 Yamaha. I am doing around 18 mph. The dealer told me strakes can raise my max speed by 5 to 7 mph
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    I'm in central Florida too, just south of you. Your dealer is the last person to take hydrodynamic advice from. They just don't have a clue, unless it comes to selling you a new part for something.

    Pontoon boats are very poor performing things and strakes will improve you "launch" speed, in regard to when you'll get on plane, but top speed, nope. Simply put, strakes (if well arranged) will permit your boat to "level out" sooner then without them, but that's about it on a pontoon boat. The only thing that improves pontoon boat speed is more power.

    If you increase to a 75 HP outboard, you'll just barely break into the low 20 MPH range. This assumes a pretty low constant, on a 1.5 ton full up load and 10% slip. A 100 HP outboard will get you into the low mid 20's, but pontoon boats are quite restricted in this regard. For example, if you double the current HP (120) you'll only see 26 - 27 MPH.

    This said, there are things you can do to improve speed with these puppies, but it usually entails considerable modification to the back half of both tubes. This essentially makes them flat or V bottom, instead of round tubes. If your a good welder and can source quality aluminum fairly reasonably, then great, but this is a daunting project for a novice.
     
  3. c4carpetcare
    Joined: Jun 2013
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    Location: Ocala fl

    c4carpetcare New Member

    Thanks for the info Par. I know some great welders & I am up for trying anything on the boat. Unless it costs so much I should just replace it. I am in the market for a larger motor too.
     
  4. PAR
    Joined: Nov 2003
    Posts: 19,133
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Again, if you double the HP over what you currently have, you'll get another 5 - 6 MPH.
     
  5. c4carpetcare
    Joined: Jun 2013
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    Location: Ocala fl

    c4carpetcare New Member

    Par, any advice for the tube modifications you mentioned?
     

  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 474, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Yes, have it done by a designer that has a clue. You could probably get a "yard guy" that says he does it all the time, to weld up some sort of contrivance on your tubes, but I'll bet 90% of the time, you'll actually lose speed from drag than gain anything. The bottom line is, you'll need both tube modifications and a bigger engine, if you want to overcome the inefficiencies of pontoons and get more speed. The engine size increase alone will produce a little more speed, but coupled with appropriately placed and sized changes, you can get a little bit more.
     
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