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Thread: 2 blade 3 blade whats the differance ????

  1. #31
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    ------------------------------------------------------------------------------------------------------------------------------------
    Last edited by Chris Harris; 08-29-2011 at 06:29 AM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  2. #32
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    Quote Originally Posted by Chris Harris View Post
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph
    wow

    what i am getting at is you would only ever use the v series in a saw run , never in a race setup . what i am trying to figure out now is what props to buy and what to stay away from . so far for a 1/8 hydro setup x are safe for all to use and are a good start point , 1600, 1700 and abc are more hydro props .

  3. #33
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    Quote Originally Posted by magnum500sw View Post
    wow

    what i am getting at is you would only ever use the v series in a saw run , never in a race setup . what i am trying to figure out now is what props to buy and what to stay away from . so far for a 1/8 hydro setup x are safe for all to use and are a good start point , 1600, 1700 and abc are more hydro props .
    I'm not saying that the V series can't be used in a race setup, I have certainly seen it done but in SAW setups is where they seem to do the best. When it comes to moving a big, heavy boat like an 1/8 the X series are a safe bet. The 1600 and 1700 series Octura props have high lift characteristics and will need some modding to make work.

    Chris
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  4. #34
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    So if find a x series that really works good and I wanted to try a 1700 or a v series would I go to the prop chart find a similar dia and pitch. Or would I add pitch and or dia. I would think you would add some pitch because of the added lift. to me it seems like the added lift would = more rpm.

  5. #35
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    -----------------------------------------------------------------------------------------------------
    Last edited by Chris Harris; 08-29-2011 at 06:28 AM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  6. #36
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    Changes in diameter change the prop load LOTS more than changes in pitch. One mm increase in diameter makes a huge difference compared to 1 mm increase in pitch. That's why people run cut down and/or pitched up props.

    Lohring Miller

  7. #37
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    If you take say a 45mm diam x 1.4 = 63mm pitch, If you cut the diam down to 40mm do you end up with a 40mm diam but pitch is still 63mm. Their for pitch ratio to diam is higher. Thanks Martin.

  8. #38
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    ------------------------------------------
    Last edited by Chris Harris; 08-23-2011 at 01:41 PM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  9. #39
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    "Like I said above keeping the same diameter and going up in pitch increases load exponentially."

    Propeller load is roughly directly proportional to pitch increases, but is proportional to around the 5th power of the diameter. See this for air propellers. The same factors hold for water operation.

    Lohring Miller

  10. #40
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    -----------------------------------------------------------------------------------------------------------------------
    Last edited by Chris Harris; 08-29-2011 at 06:28 AM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  11. #41
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    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

    This really speaks for itself. Don't abandon this thread. You've been a real help it's unfortunate that I really have no idea and experience to addequately determine the good and the bad. I'm not saying what's right and wrong with anyone's post. But your rep speaks volumes to a noob like myself and others that may pass thru this thread. I'm sure they don't shelf a rtr 139 mph hydro.

  12. #42
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    I'm a long way from a prop expert. However, I've been involved with attempts to scale model results to full size and have searched through a lot of information. I also race with one of the best prop men out there, Brian Buaas. We are all in learning mode with surface piercing props. Nothing beats a lot of trial and error. From this, I know you can add a lot of pitch before you need to take a tiny amount off the diameter to reduce the load. Eventually you have too high a pitch to diameter ratio and the efficiency goes down.

    By the way, the link above talks mostly about the difference between two and three blade props, the topic we were discussing.

    Lohring Miller

  13. #43
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    --------------------------------------------------------------------------------------------------------------------------------------------
    Last edited by Chris Harris; 08-29-2011 at 06:27 AM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  14. #44
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    Chris please continue ... Lohring please go away
    Last edited by jamie; 08-25-2011 at 08:02 AM.

  15. #45
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    Chris holds more records than just about anyone I know. His boat designs, setups, and obviously prop choices speak for themselves! He is the LAST person I would ever argue with but there always has to be someone of no particular fame that knows far more than the experts. Go figure.
    Mini Cat Racing USA
    www.minicatracingusa.com

  16. #46
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    I've been involved with these still standing straight line records:
    NAMBA GX1 hydro 109+ mph set in 2005
    NAMBA GX1 Sport Hydro 97+ mph
    UIM 144 volt hydro 98+ mph set in 2008
    NAMBA A Outboard Hydro 81+ mph
    And these recently passed records:
    NAMBA G1 Hydro 106+ mph
    NAMBA GX2 Hydro 103+ mph

    See UIM records and NAMBA records

    The details of the NAMBA gas records with my picture are here on page 12.

    I'm not trying to put anyone down. I'm trying to be educational from my experience of 25 years in model and full size boating.

    Lohring Miller

  17. #47
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    Quote Originally Posted by sailr View Post
    Chris holds more records than just about anyone I know. His boat designs, setups, and obviously prop choices speak for themselves! He is the LAST person I would ever argue with but



    there always has to be someone of no particular fame that knows far more than the experts. Go figure.
    Gee Jim, I guess the National Safety Director of NAMBA and a veteran racer with more records than you'll ever dream of is "someone of no particular fame "

    I'm sure Lohring wasn't trying to dispute Chris's knowledge and accomplishmemts but was just trying to add info from his own research.

    "Go Figure"
    2008 NAMBA P-Mono & P-Offshore Nat'l 2-Lap Record Holder; '15 P-Cat, P-Ltd Cat 2-Lap
    2009/2010 NAMBA P-Sport Hydro Nat'l 2-Lap Record Holder, '13 SCSTA P-Ltd Cat High Points
    '11 NAMBA [P-Ltd] : Mono, Offshore, OPC, Sport Hydro; '06 LSO, '12,'13,'14 P Ltd Cat /Mono

  18. #48
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    ------------------------------------------------------------------------------------------------------------------------------------------------------
    Last edited by Chris Harris; 08-29-2011 at 06:27 AM.
    I.M.P.B.A. Record Holder P-Hydro 111.001mph Q-Hydro 120.192mph S-Hydro 139.233mph

  19. #49
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    Mini Cat Racing USA
    www.minicatracingusa.com

  20. #50
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    Anyways.... I have no idea what the h@&! Just happened to my question on props. Remember 2 blade 3 blade ?

  21. #51
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    From the link in my post above:
    I had to attach it because the pictures and formula won't post. All this applies to water propellers.

    Lohring Miller

    Number of Blades.doc

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  23. #53
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    @ magnum500sw,
    Thanks for that link
    That is a really informative page for anyone to "grasp" prop terminology (like me), also there are links for rpm, sizing, installation, and FAQs.
    Daniel
    When you know it all.......you never will learn anything new

  24. #54
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    Be careful using internal combustion engine data for electric motors. Electric motors have a huge torque rise and don't loose rpm very quickly with increases in pitch or diameter. Heavy loads will stall an IC engine, but in electrics the current draw just goes up until things melt. There's a lot of data on propellers for model planes, but others experience seems to be the best for boats. Logging current draw is a big help.

    Lohring Miller

  25. #55
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    Cool thread!!

  26. #56
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    Quote Originally Posted by Chris Harris View Post
    ------------------------------------------------------------------------------------------------------------------------------------------------------
    I miss Chris ..............
    Wayne Schutte PhdCSE BaSE BaEE. Australian, & damn proud of it YOUTUBE
    @ 36" H&M Maritmo twin1512/1800 6S1P 88mph @ 40" drag hydro#1 twin 5692 12S1P .....always for fun @

  27. #57
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    Like you said: BJ26 - X642

    MG - Prather S220?[/QUOTE]
    I would have to say the x642 and the 445 are top notch MG props

  28. #58
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    All I get from Chris Harris' posts is a series of dashes all the way across the screen. Is there a link in there somewhere?

  29. #59
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    Looks like he edited all his posts for some reason

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