Prop balance

[welshhealey]

Does anyone know where I can my two blade bronze prop balanced or maybe get a more efficient 3 blade one supplied ?

[Alacrity]

Try Hamble Propellers, members have said good things about them re. balance etc.

[LaDauphine]

I have always used this lot, always appear well organised and effective. Richard

Steel Developments Propeller Repairs & Sales
240 Merton Road,
London,
SW18 5JQ
England

TEL: 020 8874 7059
Email: mail@steeldevelopments.co.uk

[welshhealey]

Sent my two blade original prop off to the company in Merton Road London, for: A to get it repaired/balanced and B to see if they can supply me with a new 3 blade one, unfortunately, due to the large blade area, they cannot supply me with a new one as they do not supply/make that type anymore so, they will have to repair and balance the existing old one only, ... as a matter of interest, they must have had an idea how old the boat was because they asked is it off an Albatross or Delta ! and after telling them what boat it is off, they made me smile by saying "looking at the prop it's a fast boat " So question is, would I be gaining anything if I had a 3 blade prop made (same pitch & diameter ) if so, is another prop supplier going to tell me the same thing ? ...I'm very much in the dark with props so please forgive my ignorance

Thank you for Reading !

[haventaclue]

I have no idea if this holds true for inboards,but a two blade prop of,say 19" pitch,will push an outboard faster than a three blade 19" pitch.I know this for sure as I run both types on "NO-KIT". Well until I spun the two blade prop that is .

[haventaclue]

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galamb
Post subject: Re: Trolling Motor 2 or 3 blade prop
PostPosted: Tue Jan 05, 2010 8:29 am
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Joined: Sat Jan 17, 2009 1:37 am
Posts: 715
Location: Inverary, Ontario - Cuddy Sport (modified)
Propellers, whether they are on an electric, gas or diesel motor are probably one of the most misunderstood factors on the boat.

Here is some "general" information on props -

For a given pitch the prop that would give you the MOST SPEED (all else being equal - horsepower or thrust of the motor, weight of the boat etc) would be a SINGLE blade prop.

You won't find one because it would run so unbalanced that it would potentially cause damage to the engine.

For each blade you add to the equasion, you create more drag, but create more forward thrust (and make the motor work harder to turn it), but you also reduce vibration which smooths out the ride.

So a 2 blade will give you more speed than a 3 blade, and the 3 more than a 4, or a 5 etc, again when all else is equal.

On the flip side of that, for each rotation of the prop, you get more forward thrust with a 4 blade than with a 3 or a 2 - but again, it is more difficult for the motor to turn a 4 blade than a 3 or a 2.

Likewise, if you increase the PITCH or DIAMETER of prop you are using, it is more difficult for the motor to turn it. Unless you are "underpropped" to start with, running more pitch will do little to increase your top speed and could in fact result in engine damage.

If the motor is working harder, you burn more fuel (unless you work it so hard that it stalls).

So in the case of your "electric" - you will use more electricity (draining your battery quicker) to turn a 3 blade at the "same" rpm as a 2 blade, but you will get more thrust (more forward motion) at that specific rpm compared to the two blade.

General "rules of thumb" for props -

If you want the MOST SPEED possible you run a 2 blade

Best all round "average" performance - 3 blade

Best "out of the hole", "lower rpm plaining" and "smoothest running" - 4 blade or 5 blade

Each boat/motor combo needs to be fitted with a prop that is best suited to how the owner or operator will use the boat.

An electric trolling motor was never designed to produce speed (as it's primary reason for existance), but if you use it to poke around on weedless flats a 3 blade prop would work well. However, as has been noted here, if you are in a very weedy environment a 2 blade will catch less grass and tends to "self clear" a little easier - and when you want to go fast, hoist out the electric and fire up the gas outboard

_________________
Graham

Yes, Plywood is "real" wood

A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it


This guy explains it better than I

[welshhealey]

Very interesting technical facts put in a language that even I can understand. (no sarcastic comments cos I'm Welsh either ! )
I have learned quite a bit from this info that has been forwarded on many thanks Haventaclue . So, with all this said and done, I wonder did that Ford Zodiac 6 cylinder in my Moonfleet did actually reach speeds in excess of 50MPH like the brochure categorically states nah, if it did, then in that case, I can knit fog

[haventaclue]

Now why would I have anything derogatory to say about the Welsh.... Oh yes the small matter of the Triple crown and Grand Slam Ah well the Championship will have to do.