Why are 4 blades better than 3?

[PCUK]

So, to summarise. Four blades run more smoothly. Three blades are more efficient and a single blade is best. The single blade is how surface piercing propellers work by only immersing one blade at a time! Only useful on racing mobos though

 

[Nigel_Ward]

I suspect the choice of 4 blades is due to the constraints of the number of blade types the manufacturer uses. To keep the number down they have to use more blades to get the required surface area to prevent cavitation.

For large ships the number of blades is chosen to reduce the likelihood of vibration due to stern shape, engine cylinder numbers and gearbox ratio.

 

[FullCircle]

I suspect the choice of 4 blades is due to the constraints of the number of blade types the manufacturer uses. To keep the number down they have to use more blades to get the required surface area to prevent cavitation.

For large ships the number of blades is chosen to reduce the likelihood of vibration due to stern shape, engine cylinder numbers and gearbox ratio.

There is only one blade type on Kiwiprop. It is cut down for pitch diameter to suit boat, and the angle is controlled by a grub screw at the base of the prop spigot.

 

[cliff]

Why not have one of these
http://www.darglow.co.uk/Propellers/FeatherStream/index.html

I would rather have one of these
http://www.steeldevelopments.net/sailing-boat-propellers-2.html

 

[sailorman]

I would rather have one of these
http://www.steeldevelopments.net/sailing-boat-propellers-2.html

Are those American made, i think i have seen one on a visiting yacht to our marina

 

[Tranona]

Australia I believe.