Question about needed surface area to plane.

Discussion in 'Boat Design' started by Docta, Mar 5, 2008.

  1. Docta
    Joined: Mar 2008
    Posts: 3
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Florida

    Docta New Member

    Hey y'all.

    Ive been poking around in here for a few years, but never needed to post before now, so thanks in advance for any replies...

    Here is my question:

    I am going to build a totally flat bottom catamaran for the flats, that I want to be able to fish several guys in...

    The boat will be 20 feet long, 8.5 foot beam, boat will weigh around 2500-3000 pounds with engines and gas, want to be able to bring on another 1500# of people and cargo.

    Question 1: How wide will I need to make each flat bottom hull to plane between 12-16 MPH?

    Question 2: How many horsepower will I need to have to cruise 30mph at full load assuming 80% power at cruise (twin engines, most likely e-tecs)?
  2. Guest625101138

    Guest625101138 Previous Member

    It is a heavy boat for 20ft catamaran.

    You can use this link to get planing results:
    I have attached results for one hull.

    If you take 25kts then 30HP required for one hull. You need to double this to allow for prop losses and other drag unless you have a well designed set up. So that makes 60HP. You then need to double that to get two hulls for the cat. So 120HP all up.

    The lower speed is not really planing and you would probably get a better result using Michlet.

    Rick W.

    Attached Files:

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