2 blade 3 blade whats the differance ????

[Chris Harris]

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[magnum500sw]

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 .

[Chris Harris]

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

[magnum500sw]

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.

[Chris Harris]

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[lohring]

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

[martin]

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.

[Chris Harris]

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[lohring]

"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

[Chris Harris]

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[magnum500sw]

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.

[lohring]

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

[Chris Harris]

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[jamie]

Chris please continue ... Lohring please go away

[sailr]

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.