I’m thinking about replacing my folding prop to a fix prop. Should I get a two or three blade fixed prop. Its for a 26’ with a Westerbeke 21 horse diesel engine.
In general, the trade-off between two vs. three is less drag under sail vs. more thrust under power. My impression is that the decision for most people depends on how they use the boat and what conditions they use it in.
I’m really curious, though. Which folding prop do you currently have, and why do you want to replace it?
– Bob
Solar Wind, Nonsuch 26C #143
I changed from a 2 blade folder (Martec) to a 3 blade fixed (Campbell sailer). Three blade was much smoother, more power, especially in reverse. I have a westerbeke 13 / 2 cyl, so ‘smooth’ is all relative. I didn’t really notice much difference in drag when sailing, but I notice the lack of vibration and instant bite when I need it all the time.
http://www.westbynorth.com/campbell-sailer/
Jon
First Command
26C #10
I replaced my folding two blade prop with a Campbell Sailor. It is a far superior prop with more power, instant response in both forward and reverse, no prop walk that I can tell. It is very economical under power at 1800 revs and really moves the boat in heavy conditions when necessary.
I never regretted the change.
Katmando, NS30u, Westerbeke 33hp 4 cylinder.
Whitby, Ontario,
Cheers
Brian
The prop drag depends which folding prop the original poster has. If it is the factory Martec non geared folding, this prop always drags the lower blade when sailing. I replaced it with a fixed two blade , less vibration, no clunking noises, works in reverse, and no noticeable extra drag.
If you are worried about it in a race you could mark the shaft and then turn it after you shut down so that the two blades are lined up with the keel, shaft, and strut. In this area disturbed water is being dragged along with your hull already so a prop can’t hurt much. It was common practice before folding props.
Noticeable drag is caused by weed growing on the bottom or too much extra weight on the boat or towing a dinghy with an engine.
Tom
26C#28 North Star
W13
Penetang
For a very detailed look at folding props, see this British yachting magazine’s 2015 assessment of 15 different folding and feathering props: https://www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807
They didn’t evaluate the models most frequently mentioned in this discussion, Martec and Campbell Sailor. However, they did evaluate a two-bladed Varifold which looks similar to the Martec to my eye, as well as an Axiom fixed three-blade that looks similar to the Campbell.
They found things that validate all sides in this discussion (again, it comes back to what matters most for your needs). T
The Varifold gave highest top speed under sail, but worst stopping distance under power in reverse. The Axiom was middling for top sailing speed, but was FAR superior to anything else for stopping distance and minimization of prop walk.
Ignoring the petty little issue of cost, that article left me thinking that the best-sounding alternatives were Flexofold’s three-blade folding, and Autostream’s three-blade feathering.
The Axiom fixed looked promising enough that I’d seriously consider the Campbell fixed-prop if its price was sufficiently lower than those two.
IMHO, two-bladed props are only for people who value sailing performance above all else and don’t expect to be situations where you’re seriously dependent on the engine.
– Bob
Solar Wind
Nonsuch 26C #143
Well, all I can say, is that one day when I got caught in a situation with 40 kts of headwind that my Gory two blade gave me a good knot and a half forward speed. I think that’s a great trade off for gaining almost a knot under sail.
Joe Valinoti
S/V IL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
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Impressive.
– Bob
Solar Wind
Nonsuch 26C, #143
Having converted my Nonsuch 30U ten years ago to electric propulsion. I can tell you there is a good reason to use a fixed three blade prop. EP allows you to operate in ways you would not with a diesel. For example in light winds I can adjust the motor control to turn the prop just enough to eliminate all prop drag and since it is electric it is almost as quiet as being under sail. It uses minimal power and there is no need for a folding prop. The second reason is Regen. When the boat speed starts hitting around 6 knots the motor turns into a generator and starts to recharge the battery bank. It is a beautiful thing to see as the power shifts from the motor to sail and makes fuel (energy) too!
Mike
BIANKA
1986 30U
THE BIANKA LOG BLOG
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Impressive.
– Bob
Solar Wind
Nonsuch 26C, #143
Here is a copy of a test conducted on props that include the two and 3 blade Campbell props. The language used is more technical then the Yachting Monthly report but it gives some idea of how the Campbell props preform. The difference in drag between fixed and folding or feathering props is significant. A number of years ago at our summer rendezvous a small group went out for a race. Winds were in the 10-14 knot range mostly on a close or beam reach. The boats included a 36 (prop unknown) , a 324 - Kiwi Prop, 30 - 3 blade fixed prop and 26 - 2 blade Maxprop. The 324 and 36 were faster then the 26 but the 30 with the fixed prop was about a knot slower then the 26 until they let the prop freewheel. As soon as the rendezvous was over the owner of the 30 changed the prop.
My understanding is the some transmissions do not like spinning in reverse so before you decide to take such an approach with a fixed prop check with the transmission manufacturer.
The two prop tests seem to suggest that the better folding and feather props perform as well or better then the fixed props.
Mark Powers
La Reina 26C (with two blade Max Prop)
Vancouver B.C.
(attachments)
propeller test.pdf (269 KB)
Great document Mark with good information. Much better than the opinion on prop drag from the other article.
It also repeats what I said regarding the Martec, it is poor in reverse and “You must be sure, though, that a folding propeller like the Martec or the Trumbly is prevented from having one of its blades fall open, increasing the drag.” One of the heavy blades was always open in my experience but I don’t know if the force of the water at 5 knots would close/lift the blade.
Also the one time I checked my 2 blade fixed did not freewheel at any speed with the transmission in neutral. I think there is too much friction in the new cutlass bearing, stuffing box and transmission for it to start turning.
Based on 10 to 20 lb of drag at 5 or 6 knots for a fixed, and the forward thrust of the Martec, the Martec looks good until I remember the lack of reverse. But maybe that’s the compromise you have to accept.
Tom
26C #28 North Star
Penetang
Mark,
Great report, thanks for sharing, some interesting results in there.
Like all things it seems personal preference plays a major role in the decision. If I could have afforded it, I probably would have gone with a feathering prop, but after having the martec folder jam several times when I really needed it to open (wish the 2 parts were geared together) I opted for simplicity and robustness, at the cost of drag. It needs a rebuild and is still sitting in a box in my closet.
Jon
First Command
26C #10
Much appreciated data.
I forget which designer said it, but there’s a lot of truth to his saying that, “All boats are compromises.” The same goes for most decisions about their equipment.
It’s nice to have good information to use in making those compromise decisions.
It’s also useful to know the circumstances governing different folks’ preferences and recommendations. There is no best prop, only the best one for how you use your boat.
I, for example, sail solo and have a crosswind slip. I need to power into the slip to keep the boat straight without the bow blowing off to port, and then be able to stop it quickly without the stern walking to starboard. I care almost as deeply about sailing performance as, say, Joe – but consequently not so deeply that I don’t truly, deeply lust for stopping power.
Someone could probably combine the data in these articles with a weighting formula for each individual’s various needs and preferences, and turn that into a pretty good prop recommender app.
– Bob
Solar Wind
Nonsuch 26C, #143
For what It’s worth, my Gori is just fine and stops the boat nicely. I take advantage of the prop walk when docking. When backing down, just shift to neutral and the prop walk goes away and you still have way on to steer the boat..
Joe Valinoti
S/V IL Gatto NS30U #221
Sea Harbour YC
Oriental, NC USA
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Thanks for the article Mark.
Had a two blade fixed on our 354 and always had to deal with a pulsing rudder under sail or power (we let it freewheel). Would have loved to replace it with a three blade folding, but it wouldn’t fit forward of the rudder. Went with a three blade Autoprop and love it. We mostly use the boat for cruising and it’s great for motor-sailing. Probably a half knot or more better under sail.
Craig Stanley
S/V Matou NS354
Tampa, FL