dsw
Well-Known Member
What advantage would one get changing a 3 blade prop to a 4 blade the same diameter?
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prop
- Thread starter dsw
- Start date
PeterGibbs
Well-Known Member
Essentially a prop's delivery potential is reckoned in terms of its disc, ie as you view it from the rear how much of the circle it circumscribes is covered by the blades? With my 3 blader I guess it's 70-75%. Going to 4 would be worthwhile if the disc were raised radically, say to 90%. Moves more water.
Of course the offset is drag. That's the judgement. I stick with 3 blades 'cos when I want to tramp I can do it. With the usual skinny 2 blader, it's egg whisk time! I accept a little drag, but on free rotation under sail I don't lose that much holiday!
PWG
Of course the offset is drag. That's the judgement. I stick with 3 blades 'cos when I want to tramp I can do it. With the usual skinny 2 blader, it's egg whisk time! I accept a little drag, but on free rotation under sail I don't lose that much holiday!
PWG
dsw
Well-Known Member
sorry i should of said my boat is a 12 tonn fishing boat 36ft steel.
Sailfree
Well-Known Member
I had the option of a 3 or 4 blade Variprop. The 4 blade is a smaller diameter, hence less effect from the hull.
Also less noise and less vibration are always factors when the diameter is reduced but they might not be any problem in the firsty place!
Also less noise and less vibration are always factors when the diameter is reduced but they might not be any problem in the firsty place!