You don’t say what research you’ve done, or why you have decided to go to a 3-blade fixed propeller. Granted the Campbell Sailer is probably the best of the fixed-pitch ones if you get it sized correctly, but all the comparative studies show that you will get a least a 20% reduction of sailing speed (i.e. a loss of 1 to 1.5 knots) from a fixed-pitch prop versus a folding or feathering prop.
Between folding and feathering, the choice is easy because only the folding prop will virtually eliminate the chance of snagging lines, nets, lobster pots, or other floating plastic junk that you will inevitably snag with either a fixed prop or a feathering one.
Of all the folding props, the Flexofold from Denmark has the best overall efficiency and reliability with very low need for maintenance. Admittedly, they are expensive, but the extra speed and efficiency will make it worth the added cost.
Interestingly, Flexofold has recently introduced a model made of carbon fiber which apparently eliminates the need for a prop zinc, although I haven’t seen any reports yet on longer-term blade wear.
Here are the two best review articles on the subject:
That half to knot and a half can better expressed as… on a 50 mile sail an extra hour or more of travel time.
I had a Gori 2 blade and two summers ago had a 3 blade fixed prop in it’s place. Smoother under motor but not quite as much power in wind and waves as the Gori. The boat sailed like a slug in light wind, drove me nuts, the admiral got tired of my complaining and hid the scotch till I stopped.
Thor,
Sounds like cruel and unusual punishment. I will let you decide if it is the complaining or the hiding of the Scotch is the punishment and which is unusual.
The above article only compares folding to a three blade fixed propeller which it says has a blade area ratio of 60%. No comparison is made to slimmer two blade props with a BAR more like 20% - 25%. It would be nice to have the comparison. Maybe I’m just not looking closely enough but most of the (non-racing) sailboats I see out of the water here in B.C. have fixed two blade props.
Just speaking from personal experience, I would think that the most significant difference would be realized when powering into a big sea. My previous boat had a fixed 2 blade and when under these conditions the boat speed would drop with each crest encounter, but the engine RPMs remained pretty constant. That tells me that the engine has the power but the prop is not transferring all that to the water. My 22 has a 3 blade fixed, but I have yet to get her in the water so the outcome is not yet determined. Of note is the blades used on high torque outboard motors such as Yamaha 9.9 and even the old British Seagull if you remember that one. They have excellent torque, but then can be withdrawn from the water to solve the problem of drag. Like everything else in sailing, there is always a trade off so we get to pick whatever suits our needs the best.
The fixed prop was a standard prop but correctly sized to the drive train. 14x11 3 blade vs 12x15 twin gori. Other issue is reverse. My 26 walks and backs to port like a tango dancer. Backing to starboard is an art. A little power, to get her moving then slip into N … not for windy days or currents . I just back off to port and there is plenty of power to push off dock walls and such. As far as using reverse to stop, not an issue. Motoring we do 5.6 at 80% of rated rpm.
That said where we sail, we sail. On the calm days under 6 knots we rarely move unless there is a schedule issue or it’s a anchorage change due to weather. We have sail-able wind on average 8 out of 10 days. So we wait.
Like sails and anchors its a personal thing as much as anything. But I do love those large 3 blade fixed props Bena-slow supplies on all their boats, we smile at them as we sail by…
Our NS26U came with a spare propeller, a Gori 2 blade 15 x 10 RH. We have yet to try out the Gori, maybe the next time we have her hauled. Does anyone have experience with this propeller? Thor you say that yours is a 12x15, is that right or is it a 15x12?
Thanks to everyone for sharing your thoughts and opinions… it helped me come to a decision. This year, I’m going with the Campbell, and I will see how it performs. If it doesn’t work out…I will go back to the Gori.
15 inch 12 pitch which is what is spec’d for the W21 / Hurth. The fixed 3 blade was 14x11. The 15x10 may work, depends on the engine rpm and transmission ratio.
If you install the Gori get the installation instructions and follow them to the letter.
FWIW - I was discussing a re-power with Beta Marine and even though they sell the own folding prop (J Prop), they recommended a fixed three-blade as the best combination with the Beta 25 and ZF15 transmission for our displacement - now I’m not a racer and I can’t remember the specific rationale but it made sense to me at the time. Cost was a factor, maintenance was a factor, sail trim was a factor - handling under power was also a factor I wish I could remember the complete argument but as I said, it sounded like a good, balanced option to me.
I’ve said this before – I have nothing but nice things to say about switching to my Gori two blade. I’ve gained a significant amount of speed under sail. I’ve not seen any big loss of powering through waves with the engine and backing into my slip seems fine to me.
Joe Valinoti
S/V iL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
Joe, I replaced my prop with a Max Prop and it’s the best thing I have done to my boat you are able to Change the pitch it is three blade aNd it has the same thrust in reverse as it does in forward. Besides that it feathers out under sail. Jim N33-41# Arawak
Paul,that was not the article I was referring to. I originally found the article on the Kiwi Prop site. I can’t find it now and I can’t get the link to work. I have managed to copy and paste two of the charts from the article.
Mark Powers
La Reina 26C
Vancouver, B.C.
Here are the results of a test conducted by Yachting Monthly, July 2012 (another British Magazine). The test compared the drag of a fixed 3 blade prop when the prop shaft was locked vs when it was allowed to spin. They attached the prop to an outboard leg on a dinghy and then used an electric motor to propel the dinghy so that they could measure the energy required. The speed differences may not be applicable to a Nonsuch. They felt that the outboard leg would be similar to a sail drive leg.The prop had a 12’ dia and 12" of pitch. The blades were wider than those on a Campbell Sailor. They also tested a 10" bucket. They concluded that at 6 knots the difference in speed between a locked vs a spinning 3 blade was .75 knots and that a 10" bucked only caused 10% more drag than a locked fixed 3 blade prop. At 5 knots the folding prop produced less than 1 kg of drag, the spinning fixed 5 kg of drag, the locked fixed 12 kg of drag and the bucket 12.5 kg.
I tried attaching the results page of the test but the file was too big.
I did a rough test a week or so ago and found that (GPS speed) the difference between locked in reverse and freewheeling was 5.8 Kn vs. 5.9 Kn. I have a fixed two blade prop.
Unless I’m trying to catch La Reina I’ll suffer the .1 Kn for the sake of the peace and quiet of sailing.
