Six-bladed props

[XXavier]

In some European countries, in France in particular, these six-bladed propellers with slender blades are seen in growing numbers. Their users say that they are getting superior results, much better than with conventional two- or three-bladed props, specially in gyros and other slow-flying aircraft...
Any opinions here...?

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[Jean Claude]

The manufacturer relies on the static thrust and the feeling of its customers. The customer watchs on the low engine rpm instead of watchs on fuel consumption or rate of climb.
With no any relevant measure, how to avoid the placebo effect?

 

[EdL]

Dayton Dabbs (Lone Star Magni Gyro) said one of his customers who has one on an M-16 with a 914 was consistently consuming a gallon per refill less than the rest of the group when they flew to Amarillo to see Palo Duro Canyon (with gyrotrips.com).

I saw that gyro in the pattern at OSH, along with Dayton and his M-16 with a 912. The six-bladed prop didn’t seem necessarily louder - just “different” in its sound.

/Ed

 

[Abid]

Yes. My opinion and actually testing shows that its a whole lot of hogwash.
We are using 3-blade Kiev prop and this model 6 bladed prop is actually louder than it and its performance is absolutely not any better when you consider manifold pressure and power. The supposed ESR effect is also a bunch of marketing crap. We didn't see it. Many customers compare it to the stock props from the factory on their gyroplanes like AutoGyro stock prop. Those kind of are worst but a good purpose made prop like Kiev and many many others perform the same or better for a whole lot less money. The best thing you can do is to get the longest prop (diameter) that you can get away with on your gyroplane. We use a 70.25 inch diameter prop
Or if you legally can do it, an in-flight adjustable prop is the best

 

[Doug Riley]

As Chuck Beaty so succinctly put it, you don't scale the air up or down when you scale an airfoil up or down. The boundary layer stays the same thickness. (Among other things, this makes the aerodynamics of insects qualitatively different from that of human-scale aircraft. "On paper, the bumblebee can't fly" is nonsense.)

One larger-chord airfoil should be more efficient than two smaller-chord ones with the same span and total area.

This is a gross over-simplification, but it shows us the larger trend. If something in this particular case successfully bucks the trend, the burden is on the promoter to demonstrate how.

 

[eddie]

Your right I have flown with a 5 bladed Warpdrive prop for 800 hrs on my 230 HP RAF,its 68" in diameter, I had to use the 5th blade because

of the extra HP I had the 4 bladed prop set at max pitch and it still would go through red line and there wasn't any way to use a longer prop blade.

which would be the best solution the longer the blade the more efficient the prop.

I burn 7-8 gph which is about right for the amount of HP I am using,I cruise @ 3,900-4,000 rpm, the lower HP 2.5 will cruise @ about 4,300-4,500

and the same speed and probably burn less fuel or about the same, my low rpm cruise is because of the HP and not the prop.

The 5 blades prop makes a different kind of noise,everyone says it sounds like my Gyro is angry about something.

By using a 5-6 bladed prop on a low HP engine your not really going to get any extra push out of it,but it really looks cool.

I really don't know but I would think at the slow speeds that gyro's fly the prop is running through dirty air thats caused by the number

of blades and is causing the different noise we hear.

I am running my prop blades set at 14-14.5 degrees.