Hi Charlie Yes I would tend to agree, I'll be swapping the prop out at a later date for a larger diameter and also ground adjustable so will be interesting to do a comparison,
On another note for those thinking of going turbo or p port for power, I must say I'd lean towards the p port as it's a very simple mod and inexpensive in comparison, and would say at this stage I'm quite impressed with the overall distance.
Cheers Christian
Sent from my iPad
Ice sails, desert sails, and now, even
unlimited class sailboats can sail faster than the wind. 'Negative
slippage'. :-)
A more significant point might be that pitch numbers are virtually
meaningless, unless you're comparing two props from the same prop
maker with the same blade plan form. Even then, it just tells you
which has a finer pitch than the other.
Variables can be: whether the pitch is measured on the back side
of the blade or through the chord line, where along the diameter
the pitch angle is measured (due to blade twist), and no doubt
others I'm not smart enough to think of at the moment.
Bottom line is that unless there's an identical airframe flying an
identical prop, the pitch number isn't a reliable indicator of
speed.
FWIW,
Charlie
On 7/23/2014 7:45 PM, James Osborn wrote:
I don't know jack about slippage, but I think it is
the percentage difference between actual distance traveled and
theoretical distance traveled if your propeller corkscrewed
through the air with no thrust. I found a prop slip calculator
online and for 86 inch pitch, 2.85 gear ratio, 7000 rpm, 180
mph, I get 10% slip. Granted the calculator was for boat
propellers, but I don't think it matters as long as the units
are correct. There has to be some slip because there would be
no thrust otherwise. So what is considered a reasonable or good
amount of slip? Using Bill's numbers 86 inch pitch, 2.85 gear
ratio, 7000 rpm, 200 mph, I get 0% slip. That can't be right!
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