Speed difference between propellers

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therobesons's picture
therobesons
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Joined: 6/7/09
Posts: 114
Speed difference between propellers

I know that a good folding prop will give you the least drag there for the most speed and a 3 or 4 blade the most drag with less speed (while sailing)

My question is:

Under normal sailing conditions, wind 10-15, how much of a difference is there?

Are we talking 2 knots, 1 knot or is it hardly noticeable.

I did one nice sail to Catalina Island and back, my boat has a 3 blade fixed prop and we were over 6 knots most the time and saw 7 a few times in 12-15 knot winds.

I know that drag goes up expotincially so I would think we would hit hull speed limits before we saw much difference in drag at around 6-7 knots.

Any thoughts?

Thanks

Bob

Bob, LaRainne and McKenzie Robeson

1985 Std Rig C-36, Hull #374

San Pedro, Cal

Sailing the So Cal Islands and coastal ports from San Pedro south to San Diego.

cillman
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Joined: 12/22/07
Posts: 30

[QUOTE=therobesons;2204]I know that a good folding prop will give you the least drag there for the most speed and a 3 or 4 blade the most drag with less speed (while sailing)

My question is:

Under normal sailing conditions, wind 10-15, how much of a difference is there?

Are we talking 2 knots, 1 knot or is it hardly noticeable.

I did one nice sail to Catalina Island and back, my boat has a 3 blade fixed prop and we were over 6 knots most the time and saw 7 a few times in 12-15 knot winds.

I know that drag goes up expotincially so I would think we would hit hull speed limits before we saw much difference in drag at around 6-7 knots.

Any thoughts?

Thanks

Bob[/QUOTE]

Bob - based on eleven months with a Kiwi feathering prop, I see about a half knot extra boat speed in five knots of wind and the improvement diminishes as you approach hull speed.

Craig

Craig Illman, Seattle
S/V Espresso C34 #1150 1991

therobesons's picture
therobesons
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Joined: 6/7/09
Posts: 114

I had a folding prop on my last c36 (1986) and we have a 3 blade on this one.

Since we can sail at 6plus even into the 7's as is, I think we will stay with our 3 blade prop as I do like the smooth motoring perforance we have.

Bob

Bob, LaRainne and McKenzie Robeson

1985 Std Rig C-36, Hull #374

San Pedro, Cal

Sailing the So Cal Islands and coastal ports from San Pedro south to San Diego.

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