Lew I did not mean to imply that you needed an explanation about screws and I know that you are very knowable about propellers. it was an error on my part in the way I started my reply as I should not put your name on it. It was meant to help others.
Len

And they don't actually screw their way through the water, but let's not go there! 😀

Len1... "Screws" comment was a joke. No explanation on how the "screws" work was needed, at least for me. I have 3D designed and printed several "screws" in the last few years.

Lew
Florida ⛱️, USA

Lew, props are called screws as you stated because they screw their way thru the water as they turn. So if you think of them this way than as they screw their way thru the water as they turn and since they are fixed in position in the boat then they will drag the boat in the direction they are screwing into.
Think of what happens when you screw a screw (propeller) into a piece of wood (water) with a screw driver, the screwdriver (boat) moves forward with the screw as it moves forward into the wood.
Len

That hand thing is pretty neat.

I guess that identifying the direction of a prop boils down to this: Knowing which side of the prop is connected to the shaft, put the prop shaft side on a flat surface and the edge of the blade that is closest to the surface is the direction to forward. Or, just simply like s screw. Wait a minute! Aren't props often called "screws"?

Lew
Florida ⛱️, USA

Great information lew thanks it all helps understand how props work the diagram is really useful to all regards peter l 3 👍👍

I was always taught that, if you roll your hand into a fist, with your thumb straight out, your fingers point in the direction of rotation and your thumb is the direction of movement. Thus RH works with the right hand and LH works with the left hand.

Very useful Lew. Thanks.

Chris

(This is a carry-over from the Sea Rover Cabin Cruiser subject. I thought that there was enough unique conversation on propellers that this deserves its own subject.)

There might be some confusion in identifying a propeller's rotation for forward (and reverse) boat movement. Perhaps this might help explain this for most ordinary propellers.

Of course one way to identify which way a propeller fits on the boat is the hub and which side is usually threaded. Some have a through hole (and cross pin slot) where nuts are applied.

Many, like the Graupner shape being discussed, has the leading edge is curved and the trailing edge is straighter as identified in the photo. I'm sure that most experienced boat modelers know this, but it might help newbies understand how to identify propeller rotation if they were looking at an unpackaged propeller. (There are so many different propeller designs that I would not call this a general rule, but as a guide.)

Lew
Florida, USA