best prop for optimum cruise

[BrendAn]

what is the best prop for cruise and top speed.

i always believed 2 blades to be more efficent than 3 and 4 blades. 

i am talking fixed pitch or ground adjustable.

[FlyBoy1960]

Single blade with counter ballance.

[BrendAn]

1 hour ago, FlyBoy1960 said:

Single blade with counter ballance.

always one smartarse. usually its me but you can have this one.😁

[facthunter]

It WAS done but more of a curiosity than a good PROP position. Nev

[BrendAn]

Just now, facthunter said:

It WAS done but more of a curiosity than a good PROP position. Nev

Yes , also used on motorgliders

[facthunter]

With a folding blade?  It's a cycling Off centre thrust Proposition . Has to impose unwanted Loads. Simply balancing with a counterweight  doesn't take account of the Problem.  2 Blades are the simplest and strongest You won't get interference till you fine the Pitch right off like when taxing with a RR Dart .  If you've been on one you will remember the Noise and the Kerosene smell in the cabin. Nev

[BrendAn]

23 minutes ago, facthunter said:

With a folding blade?  It's a cycling Off centre thrust Proposition . Has to impose unwanted Loads. Simply balancing with a counterweight  doesn't take account of the Problem.  2 Blades are the simplest and strongest You won't get interference till you fine the Pitch right off like when taxing with a RR Dart .  If you've been on one you will remember the Noise and the Kerosene smell in the cabin. Nev

The one I saw a photo of was on a pod mounted electric motor that folded away behind the cockpit. 

Might have been a giant scale model too. 

[BrendAn]

these photos are off an old thread on this site

[skippydiesel]

"what is the best prop for cruise and top speed.

i always believed 2 blades to be more efficent than 3 and 4 blades. 

i am talking fixed pitch or ground adjustable."

 

Like you I have been told, over the years, where clearance, tip speed and power can be accommodated, two blades are the most efficient = converting given power into forward/flight speed.

 

I believe the type of airframe (draggy / slippery) and the intended mission objectives (STOL / high speed cruise) are likly to need to be considered in the prop selection process.

 

I would always go for ground adjustable over a fixed pitch, as it seem to me that even within a known airframe/engine combination, there will be variants in operational conditions, that the pilot/maintainer can fine tune the prop for eg advantage take-off,  for short or compromised strips.

 

In resents times the E-prop would seem to be gaining a strong following. I still find it astonishing that the "toothpick" blades that characterise this prop, can deliver the reported performance improvements over  more conventional shaped  prop blades. 😈

[tillmanr]

I f 2 blades are more efficient why are the jet props running up to 5 blades?

[BrendAn]

2 minutes ago, tillmanr said:

I f 2 blades are more efficient why are the jet props running up to 5 blades?

Probably the only way to get enough blade area to absorb the power.

Imagine the size of a 2 blade on. 2000 HP turbo prop

[BrendAn]

5 hours ago, FlyBoy1960 said:

Single blade with counter ballance.

Hope I didn't offend you. I was joking

[Moneybox]

7 hours ago, FlyBoy1960 said:

Single blade with counter ballance.

Single blade propellers are often used in our constant air dryblowers. Bellows type dryblowers create fluctuating airflow but constant air flow needs vibration. The single blade produces quite violent vibration separating the gold from soil. It would probably separate your aircraft components in a similar manner.

[BrendAn]

3 hours ago, Moneybox said:

Single blade propellers are often used in our constant air dryblowers. Bellows type dryblowers create fluctuating airflow but constant air flow needs vibration. The single blade produces quite violent vibration separating the gold from soil. It would probably separate your aircraft components in a similar manner.

The aircraft version is smoothed out by the counterweight 

[pmccarthy]

Still on the gold mining theme, a super sucker can lift big lumps of broken rock up to 120 meters from a shaft. That’s why your prop can lift bits of gravel half a metre or so from a taxiway if you don’t keep moving.