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[cassf1]

Hi all,

Just wondering if anyone can tell me the difference performance wise between propellers 2,3,4 bladed or is there none are some for speed and some torque and do they affect the power drain from battery

Thanks Craig

[nhp651]

you'll usually find 4 blade propellors on the older steam and diesel trawlers and steam tugs.for plenty of low speed grunt and towing power.
i will let others explain where and when 2 and 3 bladers are used,

[cassf1]

Hi nhp651

So would you use these with slow motors, thanks for your last reply

[DickyD]

Rough guide is

4 blade for tugs and the like.

3 Blade for medium speed models.

2 blade for fast electric (MTB etc)

Now wait for other opinions. 

[das boot]

So what about the seven blade scimitar prop on U-33?



Rich

[ian kennedy]

Hi Rich,

Your 7 bladed scimitar prop was designed as a high efficency low cavitation thruster to hopefully cut down on detectable noise when anti sub sonar sweeps are being made.......i think

Ian

[nhp651]

cassf1.yes would be the answer to that, set with a course pitch to the blades.

[cassf1]

Hi all

Another question is right handed looking from back of motor towards shaft or looking directly at motor shaft

Thanks

[ian kennedy]

Hi,

Right handed viewed from the stern- rotating clockwise  in both cases the leading edge of the prop is angled towards the bow

Left handed viewed from the stern- rotating ant-clockwise

Ceers

Ian

[cassf1]

Hi

so looking from the back of the boat shaft spins anticlockwise this is left handed does a left handed propeller have a left handed thread and need a propshaft with left handed thread

Thanks

[das boot]

Hi Rich,

Your 7 bladed scimitar prop was designed as a high efficency low cavitation thruster to hopefully cut down on detectable noise when anti sub sonar sweeps are being made.......i think

Ian

Ian...you are quite correct, sir! Take a house point and move to the top of the  class!

Rich

[fullboat]

This link was usefull to me,
if you open the Pdf file scroll down to see explanation on Props

http://www.floataboat.com.au/Ship%20Fittings%20Cat.pdf

[red181]

Cas, its a very difficult question to answer, I am certainly no expert, but have just done extensive testing with different props. The hull is an aerokits Firetender, its rather narrow and 3 feet long (1/16th), so it tends to be a little unstable if going too fast. We settled on  a 9.6v Graupner bb turbo, running on 2 4600 9.6v nimh packs, so its way over volts, but with a custom made water cooling system runs stone cold.

I started with a 2 blade 40mm x prop, then used a high quality aluminium 2 blade x prop., thinking that would be the answer, but whilst it performed well, just wasnt hitting the spot, I wanted faster. I moved on to a 45mm 3 blade brass standard prop, and it was better, the motor was handling it fine. I then borrowed (again!) a 3 blade cleaver type brass prop, and the boat flew!. As the motor was stone cold, I knew I could go a bit more, so had a 4 blade cleaver prop made by propshop. The boat is marginally faster than the 3 blade, motor only gets a tiny bit warm, so its not straining, and with a gps in the boat, it measures just under 15mph, for a heavy ply boat thats quite fast

I suppose it depends on the hull, weight, and the performance you want, its certainly not as black and white as people think, testing is the only answer. I was very lucky to have a good friend with me who was far more experienced than me, and had a bag full of quality props to try!

[nhp651]

I would say that most ships, when fitted with single propellors, and looking TOWARDS the stern of the ship from behind, rotated CLOCKWISE.
With a twin screw ship the starboard prop from behind rotated clockwise and the port prop rotated anti clockwise.( there are few exceptions)
All props that you buy from model outlets have RIGHT HAND THREAD, be they left or right handed propellor.
The terminology of left hand and right hand props means which way the upper tip of a prop blade rotates from stand still.
Left hand= anti clock wise(port prop)
right hand = clockwise( starboard prop.
simples, in the word of Alexander the meercat/ lol

[funtimefrankie]

Hi

so looking from the back of the boat shaft spins anticlockwise this is left handed does a left handed propeller have a left handed thread and need a propshaft with left handed thread

Thanks

Normal right hand thread on both, just make sure the props are tight.

[malcolmfrary]

About left and right handed props - continental manufacturers use logic looking the opposite way so a right hander from, say Graupner might well be rather different to the equivalent from Prop Shop.  We look at the back of the boat from behind - they look at it from inside.
As others have said, the threads are right hand in all cases, just make sure the locknut is tight or the pond bottom will gain yet another prop.

[Bryan Young]

The easiest way to tell if a prop is L or R handed is to look at the prop. Imagine it turning. The leading or "cutting" edge (the bit that bites into the water first) should immediately tell you what "hand" it is. In this respect it matters not one jot that the "continentals" look at a prop from the bows to aft, while us Brits (who probably invented the thing) look at it from aft to bows. It does matter though when you come to buy / order one. Most Model Shops buy from continental manufacturers, and I have learned from experience to "reverse" my order. (ie, I order a LH prop if I really want a RH one!).
As far as the number of blades is concerned I really don't think that on a full hulled medium speed model having either a 3 blade or a 4 blade will make much difference. I tend to fit 4 bladers because they look nicer. Cheers. BY.