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-   -   "6-10" PITCH PROPELLERS (https://www.rcuniverse.com/forum/aerodynamics-76/3189507-%226-10%22-pitch-propellers.html)

EF 07-22-2005 05:39 AM

"6-10" PITCH PROPELLERS
 
I see some props have a pitch described as "6-10" and not one single number.
What does this mean and how does it work?
What is people's experience with such a pitch?

rmh 07-22-2005 05:57 AM

RE: "6-10" PITCH PROPELLERS
 
These are props cut from thinner blanks -
So-- the pitch is lower at root --than one would be if the pitch remained constant (10) from tip to root.
For some flyers these work just fine - they are generally faster revving than prop of same size and shape --which has a constant 10" pitch.
For my own use - they have too much blade flex -
Blade flex is fine on little plastic props for park flyers but not desireable on larger props .
Further, on high power setups, it can be downright unsafe.

WS 07-22-2005 04:13 PM

RE: "6-10" PITCH PROPELLERS
 
Zinger claims that the "variable" pitch is to counter the flex. In my experience, they are superior performing props. In two aircraft where power was marginal, these propellers made a noticeable difference (improvement).

http://www.zingerpropeller.com/Dual%20Pitch.htm

Rodney 07-23-2005 09:34 AM

RE: "6-10" PITCH PROPELLERS
 
I agree with WS, they are a better prop for some cases, especially the big gassers. My 38 to 41 cc gasoline engines seem to do better with the changing pitch and have proven to be just as strong and safe as any others.

rmh 07-23-2005 09:50 AM

RE: "6-10" PITCH PROPELLERS
 
If they fit your needs - they are the right ones --

khodges 07-29-2005 08:37 PM

RE: "6-10" PITCH PROPELLERS
 
Another reason for the dual pitch is they work well on large, round cowled engines like WACOs, WWI planes, etc, where the last 1/3 of the prop is really the only part contributing to forward motion, it's the only part that really needs the pitch, and the lower pitch inboard allows the engine to rev better.

I use a 22-6/10 on my old Bud Nosen trainer/US-41, and it works great. A 22-8 would hardly provide enough airspeed to stay airborne, and the engine did not rev as freely.

pimmnz 01-18-2006 06:02 AM

RE: "6-10" PITCH PROPELLERS
 
Careful about claiming that it is only the bit of the prop sticking outside the cowl that is working, once the air is behind the prop it has done its work, so the whole prop is still doing its job, no matter what is behind it, otherwise you would expect the prop revs to be different depending on the type of cowl is stuck back there. This does not happen. Your admission that the engine revs increased with the change of prop is the real answer, put simply, more revs, more power, more speed.

acrojack202 01-18-2006 11:47 PM

RE: "6-10" PITCH PROPELLERS
 
Pimmnz,

Not to be argumentative, but I suspect the real situation is somewhere in between - that portion of the prop within the diameter of the cowl ( I'm visualizing a big radial) does certainly push air through but you have to ask what happens to that air? The momentum imparted to that air by the prop is, in some part, tranferred back to the airplane as it impacts the cylinders, which is good for cooling, but reduces the net thrust produced by the prop. Not to say there is no thrust produced, but its certainly diminshed. Carried to the extreme, imagine a configuration where the cowl diameter equaled or exceeded the prop diameter - not much net thrust there.

But practically speaking, I wonder if you can see the effect in our models? They're usually so overpowered it doesn't matter.

Gremlin Castle 01-19-2006 05:36 PM

RE: "6-10" PITCH PROPELLERS
 
The prop disc area that is inside the cowl is the smaller percentage of the total disc area. That is why you can see 200+ mph unlimited racers with only about 1.3 of the prop sticking above the cowl.
As for the 6/10 pitch props, look at my gallery photos of the P-47. That is my YA P-47 flying on a Brison 2.4 swinging a 18X6?10 Zinger. All of the cowling is blocked off except the one cylinder which is cut away for an air inlet. If there was a 32X6/10 I would be using it on the Bearcat shown in the same pictures.

ORIGINAL: pimmnz

Careful about claiming that it is only the bit of the prop sticking outside the cowl that is working, once the air is behind the prop it has done its work, so the whole prop is still doing its job, no matter what is behind it, otherwise you would expect the prop revs to be different depending on the type of cowl is stuck back there. This does not happen. Your admission that the engine revs increased with the change of prop is the real answer, put simply, more revs, more power, more speed.

derferic 02-02-2006 03:58 PM

RE: "6-10" PITCH PROPELLERS
 
The 6-10 style prop has a flat blade that presents a variable pitch to the airflow along the blade. The idea is to ensure that some part of the blade is always working over a wide range of airspeeds. That is, some part of the blade will be stalled and some part will add braking. The part doing the work will vary depending on airspeed.

The more familiar constant pitch prop is designed to work best in a small speed range, determined by the pitch and the RPM, where the entire blade is working. It is most efficient within the design speed range and the efficiency drops off when outside of this range.

The flat pitch or paddle prop is widely used in ultra-lights because their speed varies quite a bit relative to their normal flight envelop [max speed relative to minimum speed ratios]. It guarantees that some part of the prop is working. Not very efficient but effective.


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