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Old 23-11-2022, 23:16   #31
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Re: New Prop Opinions - folding/feathering

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Originally Posted by Jammer View Post
I have a Maxprop and find it to be a good compromise. Little drag under sail, good reverse performance, sufficient forward performance. If it were to fall off the shaft I would probably replace it with a Flexofold for somewhat better forward performance, somewhat less drag while sailing, less maintenance, and somewhat less of a propensity to catch lines while sailing -- at the cost of poor reverse.



No. My boat performs to the performance curve in the book. Hull speed is hull speed.

The very best prop at normal cruising speed is a properly chosen fixed pitch prop. The idea that this can be improved upon is pure bunkum, and any analysis is complicated by the fact that minor changes in pitch can lead to minor changes in performance. If you get a big improvement at cruise out of switching to a feathering prop then the prop you had before was the wrong prop for your boat.

The whole point behind fancy props is that you can sail faster in light winds. With a feathering prop you give up a little forward for this but pick up improved reverse performance. With a folding prop your forward is the same and your reverse is worse.

I have experimented with different fixed props on other boats and am skeptical of Autoprop's claims of improved performance through variable pitch. Small changes in pitch don't make large differences in fuel economy. You can get somewhat lower RPMs and noise but I don't believe there is any way for specific fuel consumption to be notably different.


Bottom line, the folding and feathering props out there are more the same performance wise than they are different: You get way better performance sailing in a light breeze with various other tradeoffs.


Unhappy with performance? Empty all the heavy crap out of the lockers, have the bottom scrubbed, and get an asymmetric.
Jammer, hull speed and cruise speed are not the same thing, you used them interchangeably here. For most boats cruise speed is lower than full speed, which is hopefully hull speed. With a fixed prop sized for full rated engine rpm, the prop is going to be less efficient at cruise speed/rpm (and any other rpm short of full rpm). The most efficient drivetrain allows the pitch to be changed to match the rpm/load/speed conditions.
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Old 23-11-2022, 23:17   #32
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Re: New Prop Opinions - folding/feathering

Nothing mentioned here but I am going to switch from a fixed to a Gori……
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Old 23-11-2022, 23:27   #33
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Re: New Prop Opinions - folding/feathering

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More so, Iíve seen people with my same boat have different performances under power. Granted, there are multiple variables but I do believe that the Autoprop may have higher speeds at a given RPM range due to the variable pitch. With my current configuration, my boat can barely hit hull speed flat out. The sail performance will be substantial with any of the options which is why I havenít been as focused on that. Currently leaning towards the flexofold or the maxprop, though.
The boat speed you get at a certain rpm is mostly determined by the diameter and pitch of the prop. Even with a fixed prop you can get a higher boat speed at equal rpm by changing to a larger prop or more pitch.

But doing so may limit your maximum rpm and maximum speed. Some props have a motorsail setting which sounds like what you want.
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Old 24-11-2022, 00:23   #34
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Re: New Prop Opinions - folding/feathering

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The boat speed you get at a certain rpm is mostly determined by the diameter and pitch of the prop. Even with a fixed prop you can get a higher boat speed at equal rpm by changing to a larger prop or more pitch.

But doing so may limit your maximum rpm and maximum speed. Some props have a motorsail setting which sounds like what you want.
Thats whee the Autoprop likely shines. Main things that Iím still contemplating learning more about itís reliability/maintenance procedures and feathering props in general pickup up more kelp. We have a lot of that here in SD thatís already an annoyance with dual rudders but can fairly easily pull that off from the swim platform. Heard another local here hate it and switch to a flexofold after a couple months from a maxprop.
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Old 24-11-2022, 01:29   #35
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Re: New Prop Opinions - folding/feathering

I can not document (precisely) the fuel consumption numbers because I write down for every fill up liters and engine hours. Then I calculate the liters per hour accordignly. Every fill up done to full which means until I can see the fuel in the hose. I left this documentation to the new owner/on the boat when I sold it. However, the average fuel consumption @ 8Kn went from 7.7L per hour with the Maxprop to 5.3 with the Autoprop. Data collection, 3 years with the maxprop, 7 years with the Autoprop. That was on a Jeanneau SO 49 with a 100 Hp Yanmar. Of course, the fuel savings alone do not justify the investment in a new prop but the increased cruise range sure does for me. Let's not forget the less noise thingy due to the decreased Rpm's with the Autoprop.

Drag..., another one I did forget to discuss...
Let's say that going from a fixed prop to the maxprop the speed gain under sails is 3/4 of a knot (Of course light winds, way below hull speed...). The Autoprop will gain only half a knot. Furthermore, with the Autoprop you HAVE to prevent it from turning. I tried this a couple times, put the gear box into neutral while sailing, once the prop turns the boat comes to an almost complete stop within seconds. That's how high the drag of the Autoprop is when left turning. With a hydraulic gear box a shaft brake becomes mandatory. Is the Autoprop perfect? Nothing is! Listening to the hype though it seems like the Maxprop is... Nope! I've had Maxprop's on three different boats for over 20 years. I know them well and I've had my share of problems with them too. Let's just mention the play that develops in the blades which then causes vibrations in the shaft which in turn then makes for play in the cutless...



Another PERSONAL data collection point Max Vs Auto.
With the Max I had never been able to reach hull speed. With the Auto instead it was possible. Furthemore, it was entirely possible to reach max Rpm with the Auto. Not that reaching hull speed would've been of any importance but when you get a new toy you want to test everything, right?
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Old 24-11-2022, 07:06   #36
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Re: New Prop Opinions - folding/feathering

A while back I got really interested in prop differences, etc.

I was given a book..."The Propellor Handbook" authored by Dave Gerr. It's a very technical read, but very interesting and informative. The book delves into every aspect of prop design, engine, transmission, propellor location, slippage, blade design and countless other titbits of information.

It's a complex topic, and certainly the one size fits all doesn't work here, but boat and engine manufacturers are not able to satisfy everyone individually, so they must find some common ground here that gives the best average performance.

One would think that some kind of feathering prop would be a mandatory factory installation on a sailboat, but it isn't. Boat manufacturers invariable fit a big 'ole 3 blade prop, probably, the very worst prop for a sailboat, but recognize, that many sailors motor a lot more than sail and a fixed prop is invariably the best prop for that.

It's up to the individual then to try and improve sailing performance and here one has to run the gamut of advertising, various test programs, etc. with the ultimate end game to find better sailing performance, rather than better motoring performance.

In short, a feathering/folding prop tries to give you a bit of both. Better sail performance at the cost of slightly less motoring performance. You can't have both.
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Old 24-11-2022, 07:52   #37
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Re: New Prop Opinions - folding/feathering

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Thats whee the Autoprop likely shines. Main things that Iím still contemplating learning more about itís reliability/maintenance procedures and feathering props in general pickup up more kelp. We have a lot of that here in SD thatís already an annoyance with dual rudders but can fairly easily pull that off from the swim platform. Heard another local here hate it and switch to a flexofold after a couple months from a maxprop.
I actually think it was Gori who features this motorsailing setting.

For reliability I think the Autoprop is down last on the list. I posted about the enormous cost of maintenance and repair before. You can add problems with kelp to that.

In your shoes it sounds like you should get the FlexOFold.

On fuel savings: anecdotal evidence canít stand up against professional testing as published in magazines linked before. I would focus on those rather than on what we post here.
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Old 24-11-2022, 08:08   #38
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Re: New Prop Opinions - folding/feathering

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Jammer, hull speed and cruise speed are not the same thing, you used them interchangeably here. For most boats cruise speed is lower than full speed, which is hopefully hull speed. With a fixed prop sized for full rated engine rpm, the prop is going to be less efficient at cruise speed/rpm (and any other rpm short of full rpm). The most efficient drivetrain allows the pitch to be changed to match the rpm/load/speed conditions.

Well, sure, my prose was imprecise.


But on a typical sailboat with a hull speed of, say, 7 knots and a cruising speed of 6 knots, I don't believe that there's much prop efficiency to be gained from a tweak in propeller pitch specifically for each of these speeds, and I don't think that running a taller pitch and lower RPMs will produce a meaningful improvement in engine/transmission efficiency.
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Old 24-11-2022, 08:21   #39
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Re: New Prop Opinions - folding/feathering

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Have you noticed or otherwise seen an increase in cruise speed with the maxprop?

I pulled up the specs on your boat:


https://sailboatdata.com/sailboat/su...y-349-jeanneau


If what is on sailboatdata.com matches your boat (often sailboatdata is wrong and often individual boats differ somewhat) then you have a 21 HP auxiliary pushing a 12,000 pound boat with 30 feet of waterline.


That's not a great deal of power for a boat that size, and is probably the main reason you aren't getting the performance under power you expect. I don't think you'll be able to fix it by tweaking the prop.
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Old 24-11-2022, 09:30   #40
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Re: New Prop Opinions - folding/feathering

I switched from a 3 blade fixed prop to a 3 blade Max Prop.

Both props are the same diameter.

Both props were pitched same/perfectly. Meaning that both had a (flat water, no wind) maximum engine rpm that was JUST under the maximum rated rpm for the engine.

The fixed blade propeller was 0.2 knots faster than the Max Prop at maximum speed (7.7 vs 7.5).

The fixed blade propeller was 0.1 knots faster than the Max Prop at same cruising RPM (6.2 kts vs 6.1 kts).

Steve
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Old 24-11-2022, 11:11   #41
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Re: New Prop Opinions - folding/feathering

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I actually think it was Gori who features this motorsailing setting.

For reliability I think the Autoprop is down last on the list. I posted about the enormous cost of maintenance and repair before. You can add problems with kelp to that.

In your shoes it sounds like you should get the FlexOFold.

On fuel savings: anecdotal evidence canít stand up against professional testing as published in magazines linked before. I would focus on those rather than on what we post here.
With the kelp pickup, itís the one I am considering and that it is the factory folding prop option so there is a decent amount of data out there. Unfortunately though, they are the only one that hasnít responded to my quote inquiry yet which is a knock in my books.

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Well, sure, my prose was imprecise.


But on a typical sailboat with a hull speed of, say, 7 knots and a cruising speed of 6 knots, I don't believe that there's much prop efficiency to be gained from a tweak in propeller pitch specifically for each of these speeds, and I don't think that running a taller pitch and lower RPMs will produce a meaningful improvement in engine/transmission efficiency.
Iíve seen a person with the same boat as me see cruising speed pickup with the Autoprop but still somewhat hesitant given some of the other aforementioned factors. My boat is underpowered unfortunately and would be better off with the 28hp option that they are offering on the nearly identical Beneteau 34.1.
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Old 24-11-2022, 11:44   #42
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Re: New Prop Opinions - folding/feathering

Lots of case specific information and observations in this thread and the thousands of other threads on this specific topic but I would refer upthread to the YM article it’s the closest thing to objective comparative data I have found. If someone has found other helpful published comparative data It would great to add to this discussion.

My own water cooler opinion is that I loved our 2 blade FOF. It was robust, great under sail, motored well in forward and reverse utilizing a Yanmar 3ym30 wth SD In our previous j109. We liked it so much we have specified a 3 blade FOF for our new boat. Should push boat forward and back and fold up when sailing. Other more useful data can be found in upthread YM article. Jm2c.
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Old 24-11-2022, 22:23   #43
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Re: New Prop Opinions - folding/feathering

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Fuel efficiency isn’t a concern. It’s more so being able to have a higher cruise speed (e.g 6-6.5 knots instead of 5.5-6). It’s beneficial when doing overnights beating into the wind and current. Wish I could sail without a timeline but I cannot.
I 100% understand your desires and questions as we sail the same waters. That “upwind/uphill” run to Catalina that everyone motorsails… or just flat motors overnight makes you want to eek out every knot we can. I went down the rabbit hole of prop research, and ended up in the same position. The Flexifold is probably the best option. Though I’m not sure if the MaxProp would really add much more to our existing kelp woes between the keel, Saildrive, and those two dang rudders!

But I keep coming back to the Autoprop. Would it provide a bit more speed… at cruising RPM? Unfortunately, the fairly well done prop study we all reference did not fully explore that feature. The study does make a statement that “ …Brunton claims, improves performance and fuel economy, with reduced rpm for a given cruising speed. We can confirm the latter: our tests show the Autoprop achieved 6 knots at 2,100rpm, compared to 2,500rpm for our standard prop and most of the others on test. “ So, my first question is, what speed did they actually reach if they ran at 2,500 rpm? They didn’t document that. On my boat, 400 rpm is between .75 - 1 kt of increased speed. Also, 400 less rpm for a given speed is a noticeable reduction in sound and vibration. (Speaking about 2400 - 2800 rpm on my boat.). So… it’s a very valid question. And in all my internet searches, I can’t find a single well documented in-depth 3rd party test of Brunton’s Autoprop. Only a handful of undocumented anecdotal claims of “yes it works”. I am concerned about all the reports of dropping blades off the Autoprop.

I haven’t pulled the pin on a prop purchase, as It’s not a huge priority with my current usage. I’m hoping to decide and procure before my next haulout. I’m leaning towards the Flexifold. But since I’m able to make 200 rpm above max rated rpm with my current prop, I think there’s room for a bit more bite (pitch) from whatever prop I choose.

Also, I was quoted $2,326 incl. shipping a year ago for a 3 blade 16x13 Flexifold. Unknown what inflation and supply issues have done in a year!
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Old 25-11-2022, 00:46   #44
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Re: New Prop Opinions - folding/feathering

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I 100% understand your desires and questions as we sail the same waters. That ďupwind/uphillĒ run to Catalina that everyone motorsailsÖ or just flat motors overnight makes you want to eek out every knot we can. I went down the rabbit hole of prop research, and ended up in the same position. The Flexifold is probably the best option. Though Iím not sure if the MaxProp would really add much more to our existing kelp woes between the keel, Saildrive, and those two dang rudders!

But I keep coming back to the Autoprop. Would it provide a bit more speedÖ at cruising RPM? Unfortunately, the fairly well done prop study we all reference did not fully explore that feature. The study does make a statement that ď ÖBrunton claims, improves performance and fuel economy, with reduced rpm for a given cruising speed. We can confirm the latter: our tests show the Autoprop achieved 6 knots at 2,100rpm, compared to 2,500rpm for our standard prop and most of the others on test. ď So, my first question is, what speed did they actually reach if they ran at 2,500 rpm? They didnít document that. On my boat, 400 rpm is between .75 - 1 kt of increased speed. Also, 400 less rpm for a given speed is a noticeable reduction in sound and vibration. (Speaking about 2400 - 2800 rpm on my boat.). SoÖ itís a very valid question. And in all my internet searches, I canít find a single well documented in-depth 3rd party test of Bruntonís Autoprop. Only a handful of undocumented anecdotal claims of ďyes it worksĒ. I am concerned about all the reports of dropping blades off the Autoprop.

I havenít pulled the pin on a prop purchase, as Itís not a huge priority with my current usage. Iím hoping to decide and procure before my next haulout. Iím leaning towards the Flexifold. But since Iím able to make 200 rpm above max rated rpm with my current prop, I think thereís room for a bit more bite (pitch) from whatever prop I choose.

Also, I was quoted $2,326 incl. shipping a year ago for a 3 blade 16x13 Flexifold. Unknown what inflation and supply issues have done in a year!
$2,150 is the quote I just got. All roughly the same with the maxprop being the most. Leaning towards the flexofold but Iíll past some days below that a couple others have posted that own the same boat as myself. Makes me consider the Autoprop but, on the other hand, that review stated a smaller pickup from the flexofold but still a pickup, a bit donít want to deal with extra maintenance, and lastly, tired of the kelp problem. Heard from those that have the maxprop and a 349 that they struggle to pull the kelp off and are switching to a flexofold.
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Old 25-11-2022, 02:14   #45
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Re: New Prop Opinions - folding/feathering

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$2,150 is the quote I just got. All roughly the same with the maxprop being the most. Leaning towards the flexofold but Iíll past some days below that a couple others have posted that own the same boat as myself. Makes me consider the Autoprop but, on the other hand, that review stated a smaller pickup from the flexofold but still a pickup, a bit donít want to deal with extra maintenance, and lastly, tired of the kelp problem. Heard from those that have the maxprop and a 349 that they struggle to pull the kelp off and are switching to a flexofold.


Clearly you didnít get a Kiwiprop quote. They are a lot cheaper.
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