5 blade propellor

Mrdeli · 06 April 2006, 20:22

Whilst surfing the net today i came across a firm selling a 5 blade prop. I've seen lots of 4 blades advertised, but this is the first 5 blader I've seen. Are they a gimick.... ot are there real benefits???

Thanks

MArk

example...

http://www.steeldevelopments.com/erol.html#731x750

Petrov · 06 April 2006, 20:29

The Quicksilver high five has 5 blades.

Petrov · 06 April 2006, 20:30

Sorry didnt check the link before.

simmons0 · 06 April 2006, 20:31

As it says on the webpage:
"Ultimate accleration for sking and towing. Extremly smoth running propeller from its 5 blade design 4.3/4" Gearcase."

Usually see them on boats that need the extra acceleration, waterskiing boats or heavy cruisers proped to get them up on the plane.
Good for hole shot, not so much for top speed.

Harry.

Mrdeli · 06 April 2006, 20:33

Thanks, so a 3 blade prop is best for top end then.

Cheers

Mark

CJL · 06 April 2006, 20:54

More blades = more drag.

Therefore you get slower top end but better aceleration.

CJL

Hightower · 06 April 2006, 20:56

A one bladed prop is the most efficient

ian parkes · 06 April 2006, 22:55

Does engine size and the number of propellor blades etc have any standard .

I have noticed most bigger engines I see have a 3 blade prop but my little Honda 20 has a 4 blade .
Is it worth changing props , i presume Honda have just fitted a good alround prop for the 20 engine . Is there a way to get any advantage with a different prop considering the engine is pushing a small SIB .

codprawn · 06 April 2006, 23:12

Quote:

Originally Posted by ian parkes

Does engine size and the number of propellor blades etc have any standard .

I have noticed most bigger engines I see have a 3 blade prop but my little Honda 20 has a 4 blade .
Is it worth changing props , i presume Honda have just fitted a good alround prop for the 20 engine . Is there a way to get any advantage with a different prop considering the engine is pushing a small SIB .

They tend to put 4 blade props on small engines to get more thrust at slow speeds - for example when using the engine as an aux on a yacht.

A 3 blade will give you a higher top speed(or should).

My 15hp suzuki has a 3 blade prop which pushes my 3.1m at about 20 - 25mph. When I use the engine on my rib I may get a 4 blade for more low down thrust.

ian parkes · 06 April 2006, 23:23

Thanks for the info . I have nothing to compare my Honda with , it sounds like changing props can be a bit experimental and expensive . What sort of money is a decent prop for the smaller engines like mine .

I am going to have to Pull a donut and take the family out a lot so the boat will often be loaded , is it best to stick with the standard 4 blade for general pupose use like this .
I did try it out with just me in at the weekend and it felt pretty quick downwind with a good tide running on the tamar . It was very windy and when I turned back into the wind the boat felt like it was trying to take off as it bounced in the chop . I had to slow down as I just couldn't hang on , quite scary .

codprawn · 06 April 2006, 23:32

Quote:

Originally Posted by ian parkes

Thanks for the info . I have nothing to compare my Honda with , it sounds like changing props can be a bit experimental and expensive . What sort of money is a decent prop for the smaller engines like mine .

I am going to have to Pull a donut and take the family out a lot so the boat will often be loaded , is it best to stick with the standard 4 blade for general pupose use like this .
I did try it out with just me in at the weekend and it felt pretty quick downwind with a good tide running on the tamar . It was very windy and when I turned back into the wind the boat felt like it was trying to take off as it bounced in the chop . I had to slow down as I just couldn't hang on , quite scary .

If your boat is going to be loaded all the time and you are getting reasonable speed stick with what you have - keep your eye open for a spare prop though - aluminium ones are cheap enough!!!

ian parkes · 07 April 2006, 16:05

I guess my prop must be pretty well matched considering Honda offer the engine and sib as a package deal .
In their brochure honda offer a High torque version for big slow boats that has different gearing and prop .
Its a new science to me I understand engines very well but props etc

Under the Thumb · 07 April 2006, 16:13

Quote:

Originally Posted by Hightower

A one bladed prop is the most efficient

A single-blade propellerwould be the most efficient - if the vibration could be tolerated. So, to get an acceptable level of balance with much less vibration, a two-bladed propeller, practically speaking, is the most efficient.

As blades are added, efficiency decreases, but so does the vibration level.

Most propellers are made with three blades as a compromise for vibration, convenient size, efficiency, and cost. The efficiency difference between a two- and a three-bladed propeller is considered less significant than the vibrational difference.

Four and five bladed propellors suppress the higher level of vibration and improve acceleration by putting more blade area into the water. They can also help to make the rake more effective in lifting the bow of the boat for added speed.

IMHO
Will