Choosing Props for High Performance Cruising Catamaran

Discussion in 'Props' started by CatBuilder, Sep 4, 2010.

  1. CatBuilder

    CatBuilder Previous Member

    I'm building a high performance catamaran with the following statistics:

    Length overall: 44'-10" (13.67 m)
    Beam: 25'-0" (7.62 m)
    Hull L/B: 10.8:1
    Draft: 1'-9"/6'-3" (0.53/1/90 m)
    Weight: 11.900 lb (5.398 kg)
    Displacement: 18.292 lb (8.315 kg)
    Bridgedeck: 2'-11" (0.89m) full load
    Sails - main : 495 sqft (46 sq m)
    -blade: 232 sqft (21.55 sq m)
    -genoa: 368 sqft (34.2 sq m)
    -spinn: 755 sqft (70.14 sq m)

    The numbers aren't all that far off from the Gunboats if you were to scale a 48 down to my size. This is a lightweight, fairly high performance cruising cat.

    Given that it can do some pretty high speeds, I'm at a loss how to choose props for this boat. I was going with outboards, but am undecided on that again. To figure out what kind of engine configuration I am going to go with, I'd like to start at the end that matters: The props.

    So what is the ideal set of props for a boat with these statistics?

    How do I know what speed the hull should be driven at?
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    FAST FRED Senior Member

    I would suggest you get a copy of Dave Geer's propeller handbook.

    There you will be able to play with the trade off between speed and fuel burn.

    Cat , tri or lead sled, SPEED COSTS MONEY!!

    If you think you want speed, the formulas are there , you can just plug in the fuel burn you can afford , 10GPH? 20GPH? 40GPH?and see how fast you can go.

    MY guess is you will run out of fuel bucks at under 12K for dashes and about 8K for LRC (long range cruise).

  3. sabahcat
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    sabahcat Senior Member

    What does the designer say?
    What have other boats of this design done?

    Obviously they will need to be feathering/folding if legs arent being lifted clear of the water.

  4. CatBuilder

    CatBuilder Previous Member

    Those are good questions... I don't know the answer to these questions and will check on them. Thank you for the responses. I will gather some more facts.
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