propeller rotation

[abohamza]

Hi,

Sorry for this principle information!!!!
How is the propeller rotating direction affecting its shape?. I mean could the right hand propeller be used with left hand engine?

[ldigas]

No.
The rotation is one of the things that is taken into account when designing the propeller.

The propeller for right and for "left rotating engine", all other things being equal, is similar, only the "other way around".

If you were to drive a right rotating propeller, with a left rotating engine, so to speak, it would be like driving astern. In a way ...

[Petros]

the prop would work but not be very efficient driven backwards. The prop blade is designed as a foil moving in a circle, the pressure distribution over the surface, and the very critical leading edge are optimized for the speed, size, pitch, etc of the prop. If it is driven backwards, it would still work, but the shape would be all wrong for a blade optimized to be driven the other way. It will not produce as much thrust and will consume more fuel at any given speed.

It might be possible to compromise the design and develop a shape designed to be more efficient in both directions, but there no much call for a prop designed like that.

[ldigas]

Originally Posted by Petros

the prop would work but not be very efficient driven backwards.

Of course. I was just trying to make up an analogy.
There are numerous factors not mentioned.

[abohamza]

how can I know the propeller rotation direction when looking from its hub (aft.) side?

[gonzo]

The forward edge of the blades indicates the direction of rotation. Also, the propeller turned backwards makes the boat go aft. There is no way to make a propeller go forward turning it in the oposite rotation.

[daiquiri]

Originally Posted by abohamza

how can I know the propeller rotation direction when looking from its hub (aft.) side?

Keep the prop in front of you, with one of blades pointing upwards:

- if the mean line of the blade root is inclined to the right then it is a right-hand prop
- if it is inclined (points to) the left, then it is a left-hand prop.

It doesn't matter if you look at it from either the front or the aft - the blade will always point to the same side.
For example, this is a right-hand prop:



Cheers

[abohamza]

Originally Posted by daiquiri

Keep the prop in front of you, with one of blades pointing upwards:

- if the mean line of the blade root is inclined to the right then it is a right-hand prop
- if it is inclined (points to) the left, then it is a left-hand prop.

It doesn't matter if you look at it from either the front or the aft - the blade will always point to the same side.
For example, this is a right-hand prop:

Attachment 62585

Cheers

Thanks Daiquiri,
The photo is more than clear.
The problem is ;I have an Airboat Prop without any indication for its for'd or aft faces, I mean a solid hub, so I need to drill the bolts & hub holes.
I appreciate if you can explain that on the photo or ,kindly, on a wooden prop if possible.

Regards

[daiquiri]

It works the same way with air props. You don't have a hub to take as a reference? No problem, look at some middle radial part of the blade. If it points to the right (like in the above picture), it is a right-hand prop. Otherwise it is a left-hand one.

[ldigas]

Originally Posted by abohamza

Thanks Daiquiri,
The photo is more than clear.
The problem is ;I have an Airboat Prop without any indication for its for'd or aft faces, I mean a solid hub, so I need to drill the bolts & hub holes.
I appreciate if you can explain that on the photo or ,kindly, on a wooden prop if possible.

Regards

It would probably be best if you could post a few pictures here.

[abohamza]

The attached photo for the first Egyptian AirBoat (my design), we've fabricated a local propeller but the boat speed was not enough, so I got confused and I'm thinking that prop may be re-installed on the other face.....may be.
Thanks for your cooperation.

[daiquiri]

Compliments for the job done so far.

The propeller in the picture is a right-hand prop and requires a right-hand (RH) engine.

But that can't be the issue here, because you airboat would move backwards if the engine was LH. As about top speed - how did you calculate the required engine power and the prop? Or did you use some existing plans for the fabrication? It doesn't look like a new engine from here - are you sure it delivers the rated power?

Cheers

[Submarine Tom]

Nice job!

I am surprised you can build this but can't figure out the propeller...?

You need a pusher prop. Very uncommon.

Have you considered turning the motor around?

-Tom

[daiquiri]

Hey Tom,
but that IS a pusher prop!

[abohamza]

Originally Posted by daiquiri

Compliments for the job done so far.

The propeller in the picture is a right-hand prop and requires a right-hand (RH) engine.

But that can't be the issue here, because you airboat would move backwards if the engine was LH. As about top speed - how did you calculate the required engine power and the prop? Or did you use some existing plans for the fabrication? It doesn't look like a new engine from here - are you sure it delivers the rated power?

Cheers

I used the info of exsist Airboats have similar dimensions and the same VW engine but I doubt it delivers the rated power!.As well as prop isn't fabricated effeciently; So that I asked about the prop and its rotaion direction