ONE BLADE PROP!!!!

[3DBatixkid]

	Quote: Originally Posted by adrian

And those would work well as oars...

[copycat]

MA December 2006 has some photos of the planes that use these.
They are different.

[yaks]

what the hell is 1 blade prop

[adrian]

	Quote: Originally Posted by yaks
	what the hell is 1 blade prop

lol - read back!!!

[hillmanr2]

I would imagine they would be insanely loud

[Troy P]

One bladers do have an interesting/weird sound. Louder, maybe.
Here's a clip of me running a 1-bladed SuperCool racing prop in F5D: http://media.putfile.com/Troys-D-99
This is not nitro, it is electric at about 35,000 RPM.

The issue you run into with 1-bladed props is static vs dynamic balancing. The Heli guys are more familiar with this than the typical airplane guy. You need the blades to weigh the same and the center of mass has to be equal. If two blades weight the same and the center of mass is different, the prop will balance statically on your balancer... but once you run it up it can still vibrate. Sometimes there is a sweet spot a prop will run at but higher or lower and it runs rough. That may be a dynamic balance issue. With a 1-blader the counter balance needs to match the center of mass as well as a normal static balance. The other thing you run into is the unbalanced force of thrust/lift the blade makes as it rotates. That can put stress on your bearings since the thrust is asymmetric. Some of the really techie tricks I've seen for one bladers is to have the counter balance bent back behind the spinner back plate so centrifugal force tries to fling it forward counter acting the blades thrust.

Long story short, 1-bladers require a bit of work to work right but they do work well. I have not used the Bolly 1-blade props but I've used several of the Super Cool racing props. He has a really cool machined key-lock counter balance that you just snap the replaceable carbon blade into.


http://www.supercoolprops.com/

[GremlinX]

Cool stuff.

[Troy P]

And here is a self-launching sailplane that uses a single blade prop for another reason altogether; Storage! Pretty great use of it if you ask me.

[wells]

Less blades is not more efficient. That is myth from the 1920s or so. It was disproven in the 40s. The reason propellers become less efficient with more blades is because of the reduced diameter.

If the diameter is kept constant, more blades is more efficient, but only by 1 or 2% at high advance ratios. The problem is, the chord of each blade must get smaller to absorb the same power and keep RPM the same. This is why single blade props are used. A two blade prop would be too narrow and not have the structural stiffness required.

Look at NACA report 698 from 1939 and also report 640 from 1938.

http://naca.larc.nasa.gov/search.jsp