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MT-Propeller 11 blade propeller delivers 15% increase in static thrust

mt-propeller.com

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Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#81

Post by leeoniya »

post_break wrote: post #13
samwillis wrote: post #11

Somewhat related thread [0] from last month about the "tipless" Sharrow MX-1 prop [1] which achieves efficiency gains of between 9-15% over comparable 3-blade propeller designs. They started out working on an aircraft propeller but pivoted to a watercraft prop. 0: https://news.ycombinator.com/item?id=33949895 1: https://www.mby.com/gear/sharrow-mx-1-tipless-propeller-1101...

I immediately questioned cavitation and that link delivered. That's INCREDIBLE. The only issue is the price of course. That looks like a perfect candidate for 3D printing and then machining the final part vs billet.

> I immediately questioned cavitation and that link delivered.

of course, [super]cavitation can do incredible things for efficiency through water as well. maybe even more-so!

https://en.wikipedia.org/wiki/VA-111_Shkval

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#82

Post by davrosthedalek »

TylerE wrote: post #47
TaylorAlexander wrote: post #40

Earlier quoted context omitted.

> That looks like a perfect candidate for 3D printing and then machining the final part vs billet. Now you need two expensive machines, not just one. Billet is not that expensive. I've seen people suggest this before and I looked on their site. They show a multi axis CNC machine making the parts. You would need exactly the same machine to post machine the 3D printed part, but now you have a second expensive and slow…

That makes it a great candidate for near-net casting. That way you save the 80% of tre billet you'd be turning into chips, and your fancy CNC gets more parts per shift.

Came here to say the same, and want to add: And longer tool lifetime as well.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#83

Post by davrosthedalek »

WalterBright wrote: post #54
vasco wrote: post #52

Earlier quoted context omitted.

You don't add them up like this. I can make a car use 50% less fuel an infinite amount of times, not just twice.

Please rethink your statement. You cannot get more motive energy than the energy put into the propeller. > I can make a car use 50% less fuel an infinite amount of times No, you can't. Conservation of energy applies. P.S. I didn't "add" them, either. 90% x 115% => 103.5%

(Your original point is not affected by this nitpicking, but:) A car, traveling any distance, between two points of constant height (in the gravity field), and neglecting work through friction (which is zero in the zero speed limit, albeit the movement is quite slow then, but a pumped out tunnel and mag lev gets you very close), requires no work, so no fuel. Technically.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#84

Post by AdrianB1 »

stevehawk wrote: post #33
AmVess wrote: post #28

Earlier quoted context omitted.

The cost of this blade setup means no one will buy it. Very high cost to purchase and equally high cost to maintain for such a tiny benefit. I had a laugh at the noise reduction claim. Sure, it will reduce noise, but the open exhausts on planes are the loudest part unless some nitwit is screwing around with the pitch.

I can't say I have the numbers to dispute this. But the loudest thing on my Cessna is not the open, 1970s era exhaust. It is definitely the prop whipping through the wind.

Is it the external noise or the cabin noise? We changed the propeller on the plane I usually fly (Ikarus C42) a couple of years ago and the new one is extremely quiet as perceived from the ground, now the engine makes more noise than the propeller. In the cockpit the noise is lower overall, but I was never able to point to the engine or to the prop from that position.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#85

Post by AdrianB1 »

vlovich123 wrote: post #29
AmVess wrote: post #28

Earlier quoted context omitted.

The cost of this blade setup means no one will buy it. Very high cost to purchase and equally high cost to maintain for such a tiny benefit. I had a laugh at the noise reduction claim. Sure, it will reduce noise, but the open exhausts on planes are the loudest part unless some nitwit is screwing around with the pitch.

Would that change when using an electric motor?

To some extent, yes. Electric motors are not completely quiet, but there are some propellers that are relatively quiet, without hard numbers it is just informed guessing.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#86

Post by AdrianB1 »

rbanffy wrote: post #60
vlovich123 wrote: post #29

Earlier quoted context omitted.

Would that change when using an electric motor?

I'd say the most favorable arrangement for noise would be a pusher configuration, with the engines close to the back of the plane instead of a tractor config on the front. This is done on the Piaggio Avanti. Not sure how well it works, but it looks like a spaceship. Eviation electrical plane recently changed their pusher design to a tractor, but kept the engines on the back (IIRC, they started with a central big one…

This is for cabin noise, for overall noise tractor is still better. On some airports very close to the city the overall noise is the most concerning factor, in some places you cannot operate at night because of the noise, so in the end it depends what you are looking for.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#87

Post by AdrianB1 »

moloch-hai wrote: post #74
TylerE wrote: post #50

Earlier quoted context omitted.

No, because drag scales with v^2. Going 10% faster requires 21% more power (and thus fuel), but only reduces trip time by 9%.

AIUI, drag scales as v³, the reason doubling horsepower adds only a trivial amount of speed.

In the pilot books in my country the v2 is the most significant factor, v3 is not even mentioned in General Aviation.

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#88

Post by AdrianB1 »

WalterBright wrote: post #49

The Wright Bros achieved 90% efficiency with their propellers. Adding 15% to that gives 103.5% efficiency, which I'm not buying.

They did not compare with the Wright Bros, but with their 5 blade prop. The Wright Brothers propeller was extremely inefficient at the speeds the test plane is flying, so don't take the 90% number at one speed and compare it blindly with a very different speed and behavior. Did the Wrights have cavitation or supersonic tip of the blade speeds?

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#89

Post by adolph »

buildsjets wrote: post #46

I'm really not a big "fan" of MT's cheezy wooden propellers. They call them "Natural Composite" but it's really just densified/compressed wood with a thin fiberglass wrapping. Here's an example of what you can expect from in-service damage, a Jetstream 41 recently hit a bird, shed a blade, and it shot right through the passenger cabin. The hilarious thing is that the government investigation called it a "survivable a…

> The hilarious thing is that the government investigation called it a "survivable accident" because no one happened to be seated in the row that it shot through.

No, that’s not why. See FAA definition below.

Survivable Accident - an accident in which the cockpit and/or structure remains relatively intact and the forces experienced by the occupants did not exceed or should not have exceeded the survivable limits of human G-tolerance. Such an accident is classified as survivable even if some or all occupants were fatally injured. (NOTE: the investigator makes his or her greatest contribution to air safety by documenting the reasons why aircraft occupants were fatally or seriously injured in survivable accidents.)

https://www.faa.gov/documentlibrary/media/order/8020.11c_.pd...

Re: MT-Propeller 11 blade propeller delivers 15% increase in static thrust

#90

Post by buildsjets »

adolph wrote: post #89
buildsjets wrote: post #46

I'm really not a big "fan" of MT's cheezy wooden propellers. They call them "Natural Composite" but it's really just densified/compressed wood with a thin fiberglass wrapping. Here's an example of what you can expect from in-service damage, a Jetstream 41 recently hit a bird, shed a blade, and it shot right through the passenger cabin. The hilarious thing is that the government investigation called it a "survivable a…

> The hilarious thing is that the government investigation called it a "survivable accident" because no one happened to be seated in the row that it shot through. No, that’s not why. See FAA definition below. Survivable Accident - an accident in which the cockpit and/or structure remains relatively intact and the forces experienced by the occupants did not exceed or should not have exceeded the survivable limits of h…

Trust me, if that propeller had hit someone in the head, they would have experienced forces that would have exceeded the survivable limits of human G-tolerance.
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