A two-blade Maxprop is being installed on my NC26C with a Westerbeke
21 hp engine and 2:1 transmission reduction. I realize this is a long
shot question, but does anyone else have this configuration and, if
so, do you know what settings were used on your prop?
Thanks,
Jim
Morgan 26C #138
Annapolis, MD
Hi
The following calculation is useful as a relative measure of
propeller "Power"
Diameter X Diameter X Pitch, all measured in inches.
This is representative of the volume of "jello" removed by one revolution
of the shaft. As can be seen, diameter has more influence than pitch.
Diameter is limited by the clearance from blade tips from the hull.
Book says to keep this clearance to no less than 15% of the blade radius.
This works out to one inch for a 12 inch prop which is likely to about right
My guess the is about a pich of 10 to 11 inches.
What does MaxProp have to recommend. What was the old prop size.
Al
Barbcat NS 30 C # 170 W27
Thanks Al. It's a 15 inch MaxProp and is replacing a 15 inch Martec folding prop. I don't yet have the suggested settings from MaxProp.
I do not have your configuration, but have a 2 blade Maxprop on my 30U, Westerbeke 27A. The people at PYI, the us distributor were very helpful when I wanted to check my settings. They also do overhauls and upgraded mine to zerk fittings for lubrication. Talk to them. I love the Maxprop - great power in both directions.
Fred & Linda Rachwitz
NS 30 U #445
Concerto
Harbor Springs, Michigan USA
I had a 71 hp Westerbeke and Maxprop on my previous boats. I found a quick telephone consult between the two of them resulted in a pretty good first approximation.
Good luck,
Ken
N33 #60
Max-Prop says :
Dear Mr. Matthews,
Thank you for your interest in the Max-Prop feathering propeller for your
Nonsuch 30. From the information that you provided following is my
recommendation.
2 Blade 16” diameter by 12” pitch for a 1” shaft $1700.00
3 Blade 16" diameter by 10” pitch for a 1” shaft $2750.00
With regards to powering performance, both two and three blade propellers
will power the boat well in flat water. The three blade has a major
advantage when going against heavy winds and seas the three blade will keep
boat speed by up to 30% better than the two blade. Moreover, a three blade
propeller will run much smoother and reduce vibrations as it is balanced
around three points as opposed to two.
...
Hi
15 inch diameter seems large.
With this I would start with 8 inch pitch
Curious as to what MaxProp has to say.
Al
I just found in the Nonsuch manual the propeller recommendations:
2-blade sailer: 15" x 12"
2-blade folder: 15" x 12"
3 blade: 14" x 10"
The MaxProp recommendation is the same as above.
Many years ago when I was working for a Nonsuch dealer, we were fitting a Max-prop to a Nonsuch 36 with a number of prop and engine experts in attendance or on the other end of a phone. It took us 6 tries to get the pitch right – hauling and launching the boat for each adjustment. Perhaps the technology has changed since then, but I tend to think that it is still not an exact science and requires some “tweeking”.
Allen Ames