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Thread: From Wood Paddle Prop to ???

  1. #1
    New Member drdmsmith's Avatar
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    Sep 2010
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    Central FL
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    From Wood Paddle Prop to ???

    I am changing props.
    1600 VW (stock 40HP) with 2:1 Belt Drive
    Previous prop was a 68 x 32" FL Airboat Wideblade Prop.
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    Boat was plenty fast, yet a bit slow to get on a plane.
    Handled great, everything was great after you hit 10-15mph. But, if you get up on a grass or mud flat with less than say 2inches of water standing on it and stop = stuck. After you push and get it moving a little, it would get going, but I'm too old for the push part now. I want to be able to have the power to get going from a stop. I turn the big prop around 18-1900 when at a stop, just outa horsepower and that big prop really digs into the air.

    I want to put less prop on it, but not a lot less. I am thinking of a ground adjustable, but am not sure I want composite. I like the character wood, so, my questions are;

    If I drop back from a 68x32 Wideblade to a regular blade, will that be enough to get me the power I want from stopped?

    Should I drop to 68x30 or 66x32? Wideblade? Regular?

    I read about dropping an inch radius = 2-300RPM or a degree pitch=2-300RPM. So if I dropped to a 68x30 I could gain 600RPM when I'm stopped? (on the prop I guess, since I'm 2:1 that would redline my motor pretty close 4500rpm)

    Furthermore:

    I see ultralight props like the UltraProp and Ivo props pretty cheap, but compared to that big ole paddle, they sure do look whimpy... Can they really push like I want with that tiny blade width/thickness? My old prop was 8.5" wide with 6.5" tips= lots of area.

    I only turn the prop about 1800-1900 at cruise and 2250 or so at my little motor's top end. Those puny props look they want to turn more RPM? How do they possibly make up for the lesser blade area? (remember my frame of reference is a massive wood prop almost 4" thick with nicely airfoiled blades).

    Anyway, I appreciate you-all's input. You have way more experience than me, this is my only boat, and I want to try to at least make an educated guess. I get in a hurry, even when there's no reason. I want to build a new cage before I run her again, but I'm searchin' all night long for a decent priced prop I can buy right now! I need to be patient...
    Ok, enough patience, back to the classifieds...
    Don
    Greater love hath no man than this, that a man lay down his life for his friends.

  2. #2
    KWAZY old Southerner... Duane Scarborough's Avatar
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    Feb 2009
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    Wilson, NC
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    drdmsmith,

    There "IS" such a thing as a variable pitch wooden prop. I know this because I happen to have one of them in new condition hanging on my shop wall.

    Here's some old pictures of it's test fit on the boat:













    This is a 66" GSC Tech II. It sure looks wimpy compared to that paddle prop.

    I ain't really "trying" to sell it, or trade it. (I could be convinced though) I figure it'll make a nice ceiling fan one day...

    I just wanted you to know that there "IS" such a thing.

    Duane
    A KWAZY old Southerner... and darn PROUD of it.

    Airboat Pros MiniPro 116 / Frog Spit
    SS rigging - with side by side seating
    Teledyne 4A084-4 engine
    Solex H30/31 Carb
    Arrow Prop 1.73:1 reduction
    67" Whirlwind 2 blade Mini Prop

    under construction

  3. #3
    New Member drdmsmith's Avatar
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    Sep 2010
    Location
    Central FL
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    12
    Duane,
    I've admired your wood prop in the other thread, and wondered how it would perform.
    I think that GSG looks great on your boat... Classy! Bet it sounds good too.
    One thing I seem to run in to is my Hub size.
    It's SAE2 with 3/8" bolts on 4.75 Bolt Circle, and a 2.25" post and 6 drive lugs 5/8" diam sticking up 1/2" or so .
    I see a few used IVO and ULTRAprops at 68" but they all fit the rotax hub.
    I figured that since I seem to be able to get one used for $300ish, it may be worth trying.
    I'd just have to make an adapter to bolt the rotax style prop to my hub.
    IVOprop only makes the Magnum and Magnum Airboat in an SAE2 style, and they are a lot more money.
    Googling props has been interesting, I am trying to learn before I buy, and be patient...
    I need to concentrate on the design of the cage, and do my knee exercises....
    Don
    Greater love hath no man than this, that a man lay down his life for his friends.

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