Interesting or Bizarre New Propeller Concept?

[Steve Helmick]

http://www.sharrowengineering.com/the-propeller/#about-propeller-section

Looks interesting, in that they have plans for quadrotor propellers. It would look weird on most stunt ships, but maybe not on all of 'em.

I figure these guys are probably funded by US Government grant money. Since I used to work on parts for such a group, I am always skeptical. I would like to know what their funding source is. Since they're in Philly, I thought maybe Philly Skip could look them up and volunteer his R&D services for stunt props?    Steve

[Tim Wescott]

Looks like loop wings (or whatever they're called).  I recall some UAV designs that used that for wings around two decades ago, with the "main" wings looping back to the tail.  It's supposed to do the same thing as winglets, only way better -- that's why every airliner today has them the story, anyway.

Usually the induced drag reduction schemes suffer from more skin drag, or only working well in one set of operating conditions.  If they're still around in ten years -- then we'll talk.

[peabody]

The boat place around the corner has them on a pontoon boat...say it works....

[John Rist]

What works in water may not work in air.  One is non-compressible.

[Steve Helmick]

My gut reaction to it is that there's a lot of surface area that creates drag but doesn't create thrust, which is pretty much what Tim wrote.

As a boat propeller, it might create more stern lift, which can be a good thing for some hulls and setups. I'm a fan of 4 & 5 blade props on boats. I run a 5 blade on mine...stays on plane at lower speed and holeshot is better than anything else I've seen, with same top speed as the 3 blade it came with. On the good side, the Sharrow propeller may be less likely to get damaged by hitting submerged objects. Or, it may be much more difficult to repair! I'm having a tough time figuring out how they could manufacture them in a cost effective way, but maybe 3D printing in Cres would work?

Akkkk...gotta go mow the yard, now that the yard waste bin has been finally emptied.  Steve 

[Tim Wescott]

What works in water may not work in air.  One is non-compressible.

If the flow is below the speed of sound then air is effectively non-compressible.  In aerodynamics "supersonic" and "compressible flow" pretty much mean the same thing.

[Howard Rush]

"Specifically, tip cavitation and vortices have been eliminated or significantly reduced..."

It's interesting that somebody who could figure out how to shape this prop would believe this statement, or, more mysteriously, would start this prop business, rather than get a real job.  Could be more than one person, I guess.

[frank williams]

He probably spent too much time as a kid playing with mom's egg mixer.

However it does lead to a nice "contra rotating design"

[Gerald Arana]

Do you think it'll work in a ducted fan?

Jerry

[Steve Helmick]

I still think they are or were funded by Government Grants. Now, they've probably gone public and selling stock.

The outfit I referred to earlier was supposed to be working on developing a Ram Jet that they thought would be quiet and fuel efficient. Yes, they got Government Grant money. Every month or so, they'd come in with some new tweek they wanted done to the nozzles. The disgusting thing was that all they did was blow air through it...no fuel, no combustion, no thrust. Total hogwash, IMO.  Steve

[Tim Wescott]

"Specifically, tip cavitation and vortices have been eliminated or significantly reduced..."

It's interesting that somebody who could figure out how to shape this prop would believe this statement, or, more mysteriously, would start this prop business, rather than get a real job.  Could be more than one person, I guess.

It should lead to reduced vortexes -- the loop wing concept is basically what happens when you teach an optimizer about winglets but not about structural issues or skin drag.  Induced drag is caused by tip vortexes, so a properly-designed prop that looks more or less like this should do well in that regard.  Saying it'll eliminate tip vortexes is pure BS, but saying it'll reduced them is entirely believable.

I dunno about cavitation -- I believe that's more about too much lift causing a low enough pressure in front of the prop that the water boils.  But I could be wrong on that -- I'm an airplane geek, not a boat geek.

[Fredvon4]

gotta scratch head on MFG the new shape vs this traditional method