three blade fixed vs. three blade feathering

[Dave Humphreys]

For the past year I have sailed and lightly raced my Beneteau 331. I have the deep keel and a "traditional" battened main. I have a three blade fixed prop that drives the boat nicely when motoring. However I suspect it serves as a wonderful sea anchor when sailing. The boat's performance in 10 knots and above air is good and above 15 knots exhilerating. In PHRF racing we are able to do well at 15 knots true and above. As the wind deminishes (below 12 kts.) we become uncompetitive. We sail the Chesapeake around Annapolis so light winds prevail for our summer nights races. Our PHRF rating of 171 includes a 9 second/mile allowance for the fixed blade prop. If I install a three blade Maxi-prop, my rating will drop to 162. It is my opinion that the feathering prop is well worth the rating change especially in the low wind range where drag seems to be more of a factor. Can anyone supply supporting numerical date or at least personal experience that demonstrates the merits of this changeout?Regards,Dave HumphreysBeneteau 331 PatriotAnnapolis. MD

 

[Ed Allen]

you are correct.

I have looked at this many times. the ratings don,t give you anywhere enough time to compensate for a 3 blades drag. If you ask your fellow racers, the winners will have folders. your are doing the equivlent of dragging a bucket behind when racing with a 3 blade. a two blade is better but it has to be aligned vertically in line with the keel when you shut down the enginge. that helps by getting it is the slip stream behind a keel, of course that depends on the shapes.If you want to race. change the prop. it will be a faster setup even with the rating change.

 

[Joe Barrett]

3 Blade

Ed is correct, do the math! You should average about 1/2 kt better sail speed on average but 9 sec per mile is a rather large penalty. Here in SW Florida the penalty is 6 seconds per mile. You might want to check with your PHRF fleet on that.

 

[Claude Labrecque]

Propeller

Hello Dave,I had the same question. From my research on PHRF rating for our hunter 35.5 (we have a fixed 3 blade and are slower in light air than other 35.5 with folding or feathering props) here is what I found concerning propeller in the PHRF North East web site. It seems that the penality does not reflect the actual speed loss in light air. Please read on:What is the propeller credit? The base handicap assumes that the boat is rigged for racing with a folding or feathering prop if the boat has an exposed prop shaft. If there is a 2 blade solid prop there is a 6 second credit and a 9 second credit for a three blade solid prop. This credit is not intended to fully account for the speed loss under sail resulting from solid props. In light air this underestimate could be as high as 50 seconds per mile.As you can see, light air and fixed 2 or 3 blades do not mix very well.  We can follow nearly any 35.5 with our fix 3 blade in more than 15 knots of wind.Good sailing