Propeller performance change - feathering

[paulmcquillan]

Anyone else have experience with a feathering prop like this?

I just installed a Kiwi Feathering Prop on Tuesday.

In really light winds Wednesday we gained between 0.4 and 0.9 knots. Wind speeds started at 5 knots and dropped quickly to 2 knots. On other nights we would have quit long ago.

Any guess as to what we should expect for differential in 6 to 8 kt winds?

At night we were also able to see the phosporescent trail of the rudder and offset prop with the old fixed prop. With the feathering prop we could see the trail disapear as the blades feather.

Real world motoring speed added .4 to .7 over most of the range. Top cruising speed climbed both from a reduction in vibration and increased power (5.4 to 6.7). Reverse is much better.

Prop has un-geared composite blades on bronze hub. Boat is 41 ft fin keel, spade rudder, about 21,000 lbs.

[paulmcquillan]

First report on sailing performance (still w smaller 112% jib):
old new prop TWangle TWS
4.1 4.9 106 deg 8.0
-- 5.12 134 deg 9.8 puff
-- 5.2 043 deg 11
4.0 4.46 078 deg 9.0

I have some better old prop data at slightly higher wind speeds.

[paulmcquillan]

On three separate days, we took notes on actual sailing performance after changing the prop. When we had some prior info from other racing days, we compared it. So far all the sailing days have had lighter and less consistent winds than usual. All info is with our 110% jib.

TWAngle__ TWSpeed __ New boat speed __ Old speed-fixed prop
047_______3.08_______ 2.10_______ -- would be under power
055_______ 8.00_______ 5.65_______ 4.3
060_______ 8.50_______ 5.80_______ 5.0
064 _______ 5.00_______ 3.04_______ 2.0
075_______ 8.90_______ 6.60_______ 5.6
080_______ 5.00 _______ 3.40 _______ 2.3
080_______ 7.10 _______ 5.32 _______ 4.0
106_______ 8.00 _______ 4.90 _______ -- no comparable info
134_______ 9.80_______ 5.12_______ -- no comparable info
180_______ 1.75 _______ 1.70_______ -- first day, we’ll check this