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[welshdragon]

      I 'm new to this, and geting very confused by the letters on propellers.
   Is there anyone out there that can tell me what the letters stand for ?
  On one post, it says that the difference between an an "X" and an "S", is that it's in the shape.
  IE,  the "X" looks like an X, and the "S" looks like an S. Another says that an "X"breaks the surface.
 As far as I can see, any propeller that breaks the surface must be losing power,  and an "S" is standard.
  I understand the difference is in the pitch, but what is it?, and how many more are there?
  Iput it middly, I am confuse dot com !!!!!!!!!

[Neil]

Don't know what your letters stand for, but the "pitch" is the amount of slope on the propellor blade, and the defitition of pitch is the distance of forward motion generated by one revolution of the propellor.
The greater the pitch ( or slope) on the propellor the further the vessel will be propelled.
 
It's usual that steam driven boats and ships have a greater pitch than motor ( or in the case of models) electric, and this is usually because steam driven ships' propellors revolve slower that electric and so need more thrust.
 
If you stick a high pitched prop on a high revving electric motor, you'll either burn the motor out or it will cavitate, giving no thrust or forward motion. A bit like an egg wisk motion......all froth and no punch!!
  
hope this helps.

[inertia]

My guess would be Standard and eXtra (pitch).
DM

[roycv]

Hi Welshdragon, The letters refer to the pitch multiplier.

S = pitch is 1.4 times the diameter of the propeller.

X = pitch is 1.7 times the diameter of the prop.

If you have props of both types you should be able to see the difference.
regards Roy

[Mad_Mike]

it think it depends on the brand. there k and p ones too. according to this thread the x and s is the propeller shape.
http://www.modelboatmayhem.co.uk/forum/index.php?topic=29446.0

[w3bby]

What make of propeller is it? The X and S can mean different things depending on the manufacturer. For Octura the X designates a low lift prop, an X4** (where ** is the diameter), has a pitch ratio of 1.4 x the diameter **, an X6 - 1.6 x diameter **. Their M-series has a modified tongue and the Y series is like the X but with 10% more pitch.

As regards a prop running half out of the water, this is known as surface drive and is used on high speed boats and generally faster than a submerged prop. Less blade in the water = less drag and allows higher pitches to be run.

[roycv]

Hi all, I think I meant p not s for the smaller pitch ratio.  These are the stock props that have been around for years Graupner etc. Not specialist products.
I believe though that props designed for surface piercing are very efficient.

I had a boat with a fast driven but small 2 bladed 30 mm dia prop shear a blade off and it worked just as well, I suppose the small mass of the blade did not unduly unbalance it, speed was about the same.
regards Roy

[malcolmfrary]

As far as I can see, any propeller that breaks the surface must be losing power

Apart from surface piercing props.  Boats designed to use them tend to go very fast.

[red181]

most common props are black plastic, either x or s, then the size of the prop, x55 would be x pitch 55mm across the blades, and so on.
 
x having more pitch will be used on faster boats, however as there is more pitch, and more blade surface, these will use more amps, and drain the batteries faster, speed is the play off. then you have the shaft size, usually metric, m4, m5 etc, thats the thread inside the prop.
 
Most boat accessory shops have them, they are quite cheap, usually approx £2 each, then there are left and right handed, as viewed from the back of the boat!

[roycv]

I seem to remember that the Richard Branson's fast  Atlantic boat had surface piercing props.

red181,
 You might be interested to know that I have many red and a few blue props in my collection and I have seen on rare occasions yellow ones!
I have many brass ones, also looking for work, which manage without any numbers at all.
The sometimes frustrating part is finding the right propeller but with the wrong thread!
regards Roy

[red181]

hi roy, yes I have some red ones, I think they are much better quality, but couldnt remember who made them, so didnt recommend, the blades are better quality, and they dont flex as much, not seen blue or yellow, the black ones are the readily available ones
 
After testing is over on my boats, and I know what set up I want,  I then move to propshop brass, usually cleaver, 3 or 4 blade, I give them the readings I have (speed, amps etc) so they can then make one specifically for me, which usually gives better performance,(and looks better) but as they are expensive you cant test with them, it would break the bank!

[welshdragon]

red181.  HI there, I have found a red propeller, which came from "radio active",. When I spoke to them, they said they only make two propeller, being the "S"and the "X".