# Folding vs Feathering Prop - views requested



## dantaden (Mar 11, 2009)

I am looking for your views, pros/cons, experiences and recommendations for selecting a type and model of prop.

My Celestial 48' is powered by a 72hp Merecedes Diesel with a fixed 3 blade 18" 18RH12 prop.

I am considering changeing this to either a folding or feathering prop -leaning more towards Gori's 3 blade at this point.

It would be much appreciated as well if you could include your sales and service experience with the dealer who sold you the prop.

Thanks and look forward to views.


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## svsirius (Jan 14, 2007)

47 ft Moody 3 blade max prop sold by PYI bought two of them over the years for different boats. Not cheap but well worth it, ours have been bullet proof.


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## klem (Oct 16, 2009)

Why are you looking at a prop change? Are you racing and want to get maximum performance or are you cruising and want a good compromise of sailing and powering?

For all out racing, a folding prop is best generally. However, the propeller will not do a very good job trying to power into rough weather and will make the boat hard to control in reverse. The units do also have wear parts which means they will need rebuilding from time to time.

For cruising, a compromise prop would be a feathering one. They have significantly less drag than a conventional fixed blade unit but still provide good motoring performance. One drawback that I have run into is that they cost a lot and need to be rebuilt from time to time. The max props seem to hold up for a while before needing rebuilding but my experience with a luke prop was that it needed rebuilding quite often. The luke wheel is not a common unit but it did actually fail a couple of times (it is a 32X20 so the smaller ones might be better). These feathering units also have the tendency to hook on lines so if you sail in places like Maine, you have to be careful.

Another option if you are looking for improved cruising performance is the campbell sailor. I have no experience with this propeller but it gets good reviews and may fit your circumstances well.


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## MC1 (Jan 6, 2008)

I'll also vouch for the Max Prop; you should be able to find a lot of information on it and the Auto Prop by searching older posts here at Sailnet (I find doing a Google search with " site:www.sailnet.com/forums" appended works well --- eg. http://www.sailnet.com/forums/gear-maintenance/51249-maxprop-autoprop.html ).

One thing I like about the Max Prop is that it's quite effective when backing the boat out of the slip (its blades reverse direction so it has a good bite on the water) and has significantly reduced prop walk compared to the same boat with fixed 2 or 3 blade props. This can be very helpful if there's a good crosswind at your slip or for other tricky situations. I've read that folding props are poor in this regard.


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## windward54 (Apr 12, 2000)

I changed out to an Autostream 3-blade feathering prop and have been very happy with it. Prop walk is almost completly gone; I have just a split second of it when I put the engine into reverse.


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## PCP (Dec 1, 2004)

Some months ago I have read a very complete test on sailboat propellers. I believe it was a French magazine (Voile or Voile et voilliers). Autoprop come as one of the best, if not the best.

Autoprop

I have used for 5 years an autoprop on my sailboat with excellent results.

Regards

Paulo


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## LazylighningII (Nov 8, 2006)

I have an autostream on the Lazy Lightning II a Kauffman 47 for 5 years. It is stainless one less dissimilar metal to worry about. Then it digs in when you put in rev. I did do a fair amount of research at the time, great product and a good price. I have been happy with it.


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## dantaden (Mar 11, 2009)

Thanks for your experience. I'd like to keep discussion open for more advise on these and other models.

Autostream - first I have never heard of these guys but there product looks interesting. The folding props looks very similar to Gori's. What was your experinece dealing these guys during the sale and delivery and have you experience there service yet - is it global.

Autoprop - always been curious about this prop. Can you advise your experience with fwd/reverse prop walk and if you found the blades move and noisey under sail. As well, any trouble with blades not opening under fwd/rev. And as above your sales & service experience, how was it ?

Please forgive the interogating questions, but I'm a little more cautious with this than normal boat stuff since it is far more costly to change a second time.

Can you advise if the your new prop was sized right the first time ?

Thanks for your comments and I look forward to more.


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## windward54 (Apr 12, 2000)

I bought my Autostream prop directly from the USA distributor, which is Martec. Gary, who I believe is the son of the original Martec designer, spent about two hours going over both the Martec folding and the Autosteam feathering. Customer service was outstanding. 

Autostream is made to order in Australia by Skyhawk Ltd. They have a really good website which goes over their product. I like mine.


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## genieskip (Jan 1, 2008)

I have had good experience with Maxprop. I had a two blade design on my previous boat and have a three bladed for my current boat. In both cases the boat is was easy to control in reverse while giving good performance overall. The folding props, as someone mentioned earlier, are really only of interest to racers.


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## PCP (Dec 1, 2004)

dantaden said:


> Thanks for your experience. I'd like to keep discussion open for more advise on these and other models.
> 
> Autoprop - always been curious about this prop. Can you advise your experience with fwd/reverse prop walk and if you found the blades move and noisey under sail. As well, any trouble with blades not opening under fwd/rev. And as above your sales & service experience, how was it ?


Very little prop walk, the efficiency is the same, backwards or forward, you don't hear nothing and no problem at all. I had never need any exterior service. the maintenance is very simple and I have done it myself (5 minutes).

This is not just a folding propeller, but an automatically adjustable pinch propeller. It´s biggest advantage it's the cut on fuel consumption and the increased autonomy.

It is especially efficient while motorsailing. Suppose I have wind to make 3.5 knots and I want to make 6 knots. With the standard propeller I would have to put the motor at 2000rpm. With an Autoprop, to do the same, I only need 1000rpm. There is almost no noise and the autonomy increases almost twice, not to mention costs and motor life. The only problem is that when the wind picks up and you don't need that extra push to sail at more than 6K, sometimes you forget to turn the engine of, because you cannot hear it.

It is also very efficient if you have flat seas, or just small waves. In those conditions I could make the same speed with less 800rpm, comparing with the standard propeller.

Minus:

Price

In stormy or very agitated seas probably this propeller is marginaly less efficient than the standard one. On those rare conditions were the speed of the boat varies constantly because big waves are stooping the boat I believe that there is some loss in efficiency (because the pinch is changing all the time), but I am not sure.

The other only propeller I would consider to replace an Autoprop would be a Gori with and overdrive. They were also impressive on that test that I had mentioned.

Regards

Paulo


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## padean (Jul 5, 2001)

*VariProp*

Got a Variprop for my CS34 last year to improve the sailing performance and help with a little local racing. I have been very impressed with this prop.

Pros: 

Easy to install
Very easy to adjust pitch, both forward and reverse
Excellent power in reverse, better than my old 2-blade fixed with less propwalk
Good power through rough seas (3-blade model)
Cons:

Expensive (consistent with other feathering props)
Defective screws detected by manufacturer, but they changed out the entire prop-head for a new one at no cost - even offered to pay the haul-out fee
Not quite as efficient as a fixed prop
I went with feathering over folding because I have to reverse our of a slip in a narrow channel. Folding definitely has lower drag, but not as much thrust effeciency.


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## christyleigh (Dec 17, 2001)

PCP said:


> In stormy or very agitated seas probably this propeller is marginaly less efficient than the standard one. On those rare conditions were the speed of the boat varies constantly because big waves are stooping the boat I believe that there is some loss in efficiency (because the pinch is changing all the time), but I am not sure.


 My understanding of what is going on and why differs with that assumption of "less effciency". The "Auto" in AutoProp gives a fantastic Bite when needed and 'de-pitches' when not.... such as when you have sail up to aid in propelling the boat by its unique design. So I carry that forward to assume that when "big waves are stopping the boat" it goes to max pitch and bites hard - just like when you are starting from a stop - in either direction (the blades switch around to always face the same way into the resisting water). I have had AutoProps on 2 different boats and although I can't claim any perfectly scientific A to B tests if price is not an issue AutoProp has done all it claims to do for me.


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## tommays (Sep 9, 2008)

In this neck of the woods the folders even when geared require a LOT of sea life maintenance OR they tend to stay closed partially


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## RichH (Jul 10, 2000)

Most of the feathering props are 'pitch adjustable' .... some can either have their pitch adjusted while the prop is still installed and the boat is IN the water. With most feathering props, you can OPTIMIZE the prop's pitch to optimized engine rpm for best power/efficiency,etc. 

Folders while having much better drag characteristics, cant be easily pitch adjusted.


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## jrd22 (Nov 14, 2000)

We had an Autoprop on our Northsea 34 for 15 years and never had a problem with it. No prop walk and lot's of thrust in forward and reverse made close quarters maneuvers easy. You do need to use more throttle from a stop compared to a fixed blade, but you get used to it. Our sailing speed in light winds increased at least 1/2 knot compared to the three blade fixed and our motoring speed increased almost 3/4 knot at the same rpm so we reduced the rpm to cut down on engine noise and still maintained a higher speed. The only contact with the dealer was to order the little zincs, which we received promptly. Wish I could afford one for the current boat.


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## PCP (Dec 1, 2004)

christyleigh said:


> My understanding of what is going on and why differs with that assumption of "less effciency". The "Auto" in AutoProp gives a fantastic Bite when needed and 'de-pitches' when not.... such as when you have sail up to aid in propelling the boat by its unique design. So I carry that forward to assume that when "big waves are stopping the boat" it goes to max pitch and bites hard - just like when you are starting from a stop - in either direction (the blades switch around to always face the same way into the resisting water)..


No, the specific situation that I was talking about happened at Fournells in Mallorca. Furnells is a large cove with a small entrance. It is a very good shelter. Me and lot's of boats were inside while the Mistral was blowing outside at more than 40 k. It take almost a week for the wind to lower to about 25K. The seas raised by that storm were hudge (for the med) with very steep 5 or 6 meters waves that come (as usual in the med) with a very short period.

The wind was just blowing dead on the passage and we atempted to sail out knowing that if he could motor out of that narrow passage we could turn the boat and sail fast out of that hole.

Everything went find except that we take 3/4 of an hour to clear that small passage, making less than a knot with the engine at 3/4 of max Rpm.

The boat took a steep big wave and the autoproop ajusted for power, the boat went down the same wave and the propeller adjusted for speed. Almost imediately it started to climb another one and the propeller tried to ajust for bite, but with so much fast changes in pitch, de overall bite was not good.

As jrd22 as said: "You do need to use more throttle from a stop compared to a fixed blade" and as the boat was always trying to gain speed, just to be stoped by the next have, I believe that in these conditions a fixed prop woud have been more efficient.


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## Valiente (Jun 16, 2006)

RichH said:


> Most of the feathering props are 'pitch adjustable' .... some can either have their pitch adjusted while the prop is still installed and the boat is IN the water. With most feathering props, you can OPTIMIZE the prop's pitch to optimized engine rpm for best power/efficiency,etc.
> 
> Folders while having much better drag characteristics, cant be easily pitch adjusted.


This is precisely why I chose a four-blade feathering VariProp for the steel cruiser (I want a far more torque-y bite in reverse) and a Gori folder for the racer.

I have yet to install the VariProp as I am repowering this year, but the Gori's been on a number of seasons and you can read my positive remarks (and a few reservations) using "Valiente" and "Gori" in the search function.


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## christyleigh (Dec 17, 2001)

PCP said:


> The boat took a steep big wave and the autoproop ajusted for power, the boat went down the same wave and the propeller adjusted for speed. Almost imediately it started to climb another one and the propeller tried to ajust for bite, but with so much fast changes in pitch, de overall bite was not good.
> 
> As jrd22 as said: "You do need to use more throttle from a stop compared to a fixed blade" and as the boat was always trying to gain speed, just to be stoped by the next have, I believe that in these conditions a fixed prop woud have been more efficient.


 Thinking overnight I may have the auto-pitch adjustment bass ackwards in my head but I have never been without all the power I needed. The waves you are speaking of are 2-3 times more than I have ever seen..... and I plan to keep it that way. The only 'test' I have ever given my AutoProp was straight into a 20kt wind with an opposing tide in L.I Sound creating very steep, short period 5-6 footers (not meters ). There was salt water raining from the rigging but I was holding 5-6kts easily with only a slight increase in throttle. Maybe unlike your experience my Auto was always in Power mode and never coasting down your much higher waves so it just kept pulling like a tractor ignoring the waves completely.


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## MJBrown (Apr 1, 2009)

Had an Autoprop on a 36'er and loved it. The pitch was perfect from the beginning but the boat did prop walk something terrible but I'm not sure if it was the boat or the prop. I got used to it and used to my advantage when approaching or leaving docks. Picked up apx 3/4 kt of speed under sail alone and suspect an equal amount under power. Always drove the boat consistently strong. The worst conditions were 30kts on the nose, 5-6' chop for 6hrs and never a problem. You do need to make sure you grease the hubs when you haul the boat for painting, etc. Otherwise a blade can hang up and cause vibration at low speeds. The only real issue was longevity. Seems the prop we had experienced some corrosion to some internal portion of the bearing race. As it was not a replaceable part it's expected that prop at some time will have to be replaced. Not sure if this was an issue with this particular prop or not. Traded the boat so will never know.


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## roline (Apr 7, 2000)

*folding martec prop*

I've had the Martec 14Dx12P on a 30ft Cal 9.2 since purchased. The only complaint with folding props is a weak reverse. Fuel consumption is good and I included a RPM to hull speed graph.


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## dantaden (Mar 11, 2009)

Thanks again everyone for your comments.

I have read on other threads that most featuring props require periodical maintenance, Variprop, Maxprop etc.. I have also heard the same with Autoprop, but requireing annual maintenance (bearing replacement) and overhaul. Some owners had experienced losing Autoprop blades.

and other owners have experienced no or very little problems or maintenance with their feathering or Autoprop.

I suspect these are extreme cases and/or perhaps some impact from salt water. 

Is the above a valid concern - can anyone share further experiences ???


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## MC1 (Jan 6, 2008)

Dan - Your summary seems about right from the reading I've done as well. One other item I can add about the MaxProp . . . 

The MaxProp on my boat was corroded because the zinc was allowed to be completely consumed. In addition, the prop was a little oversized for the boat and was not allowing the engine to reach its proper full RPM (this was observed in the survey when I purchased the boat). Adjusting the pitch was not sufficient to overcome the problem in my case. The prop was sent back to PYI for refurbishing, and they were able to reduce the prop diameter, polish it back to like-new condition, lube it, etc.. PYI was very knowledgeable about the use of their product in a wide range of circumstances, and was very customer focused. It was nice experiencing such competent and truly helpful support from the vendor.

Here are the before - after pic's . . .


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## Faster (Sep 13, 2005)

MC1 said:


> Dan - Your summary seems about right from the reading I've done as well. One other item I can add about the MaxProp . . . .


MC - can you expand on the annual maintenance required on the Max if you've had it long enough?

I have an opportunity for a pretty good deal on a used Max - so I'm curious as to what's involved on an on-going basis...


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## MC1 (Jan 6, 2008)

Faster - From reading other threads, I believe annual maintenance may be required for the AutoProp. Regarding MaxProp maintenance, re-lubing is recommend every 2 years, as per the following from the PYI web site . . . 

PROPELLER MAINTENANCE 
The Max-prop needs to be degreased a minimum of once every two years. We recommend Lubraplate “130 AA” grease.

There are two holes in the spinner of the propeller to grease. Remove the set screw from the forward holes with a #3 metric Allen wrench and screw in the zerc tower, attach your grease gun and fill the propeller with grease until the grease starts to come out between the hub (1) and the spinner (7). Replace the set screw and remove the set screw from the more aft hole. Reinstall the zerc tower and attach your grease gun and fill the propeller with grease until the grease starts to come out between the blades and the spinners. Remove the zerc tower and reinsert the set screw into the propeller. Do not leave the zerc tower in the propeller.
• With each pump of the grease gun rotate the propeller from forward to reverse to allow the grease to work through the propeller.
• The numbers above are from Figure 2 at the beginning of this Max-prop Manual
• Make sure that you always keep the zinc anodes in good condition. They must be replaced at least once a year. The propeller must be protected by a lot of zinc, so also use a zinc on the shaft when possible. When replacing it make sure that you clean the contact point between the zinc and propeller. Use a wire brush or fine sandpaper to clean the aft of the end cap and the forward face of the zinc to give the zinc good contact with the propeller.


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## Faster (Sep 13, 2005)

Thanks for that... had found it myself just this morning and have printed it. Seems straightforward enough.

I take it you've not done this yourself yet.


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## MC1 (Jan 6, 2008)

Correct, I'll be doing it myself for the first time this coming spring. I'm wondering if the recommended grease (Lubraplate 130 AA) is available generally (e.g., at WM), since they make a point of stating not to use Teflon grease as it will wash out easily.


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## Faster (Sep 13, 2005)

MC1 said:


> Correct, I'll be doing it myself for the first time this coming spring. I'm wondering if the recommended grease (Lubraplate 130 AA) is available generally (e.g., at WM), since they make a point of stating not to use Teflon grease as it will wash out easily.


Let's hope so.. esp since one of the reasons for recommending it was lower cost!


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## FlyinNOE (Nov 28, 2008)

I installed a Flexofold on my 40' Beneteau Oceanis 2 months ago. Since then we have sailed 300 miles with the new prop.

I ordered straight from the US distributor here:
Flexofold Low Drag Folding Sailboat Propellers for Racers and Cruisers

Beautiful prop (I had it on my desk for a few weeks at work before the install!).

Performance wise there is a .5 to .6 knot difference between it folded and not folded. If I am sailing VERY slowly and I slowly motor down to neutral I can trick the prop into "windmilling" like my fixed prop used to with the sails driving the boat. I can be sailing 2.5 knots in light wind and hear it turning (if I managed to motor down correctly). Once I go down and grab the prop shaft and slow it slightly you can hear the blades fold and the boat accelerates .5 to .6 knots. I have done this a few times to verify the results and to prove the difference to friends.

Motoring is more efficient (same hull speed with 300-400 RPM less engine speed) and backing is identical to my old fixed prop.

Customer service was excellent.

The anode covers the working parts and pieces thereby reducing the likely hood of the prop being fixed by marine life.

Hope this helps.

Brian-


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## Valiente (Jun 16, 2006)

I too noticed such an improvement in sailing qualities with my Gori folder in terms of acceleration in a puff that I had to revise at what apparent wind speeds I would change my sails (I have hank ons).

Basically, I got the better part of a knot for "free" and while I haven't noticed much change in "top speeds" for a given sail area, set and similar apparent wind speed, I get there quicker and the whole motion of the boat is "sprightlier" if that makes sense.

I can't necessarily attribute this to the folder, but my hull speed is, in theory, 6.9 knots on a 26 foot LWL. My GPS in current-free water once recorded 7.3kn on a close reach on a day with 25 knots, a No. 3 and a single reef set. Last Sept. 28th, with 25-28 knots, a No. 3 and a full main set, we hit 8.9 knots SOG on a beam to broad reach. I've never surfed for so long in this boat, and while I can't credit having a folding prop, my gut says that taking that resistance out of the equation allowed us to get surfing sooner.


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## dantaden (Mar 11, 2009)

As most think folding props are designed for racers - this is not necessarily true. Now, with more cruising in mind, I see the benefit of a folder, getting to destination quicker under sail, leaving less mileage for motoring.

Valiente, just curious why you decided on a 4 blade feathering and not a 3 or 4 blade folder ?

Back from the Toronto boat show and still the Gori 3 blade folder w/overdrive is top of mind for my 48' Celestial (34,000lbs).

Please advise and share comments.


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## FlyinNOE (Nov 28, 2008)

*Folders*

Many previous designs of folders allowed marine life to foul the working of the simple (and fairly open) folder. This meant that they were only really a viable choice for guys who were very maintenance conscious or didn't keep their boat in the water (like racers).

The Flexofold's design significantly reduces that likelihood (as does many of the newer other brands).

I bought the folder because of the lack of maintenance required, greater reduction in drag and the great reviews it had been given along with some very good customer service.

The benefit had been our ability to sail when previously I would have motored. The Puget Sound had very weak winds in the summer months.

Brian-


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## PCP (Dec 1, 2004)

I believe that the Gori with overdrive and the Autoprop have some advantages over the others in what concerns cruising...if their prices are not a problem.

I failed to mention an useful feature on the Autoprop propeller. If you see a rope too late to stop or change direction and run over it, if you have time to shift to neutral, probably you don't get stuck (the blades move freely and avoid getting caught). It seems a small thing, but saved my day at least three times in the last 5 years.


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## jrd22 (Nov 14, 2000)

The Autoprop doesn't have any yearly maintenance except to change the zinc on the end as far as I know. Ours is pretty old, maybe the new ones require something, we haven't had to do anything other than the zinc in over 15 years.


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## MJBrown (Apr 1, 2009)

PCP, I only wish the Autoprop would release a line wrapped around it as easy as you stated. Only had it happen once, and it was my own fault, but it took 2-3hours in a swift current to cut it all off.

jrd22 As for annual service ours had to be greased at haul out as well as a new zinc. There were two small screws on each hub that you removed. I one you inserted the grease fitting, the other was the exit hole. I'm amazed that you've gone 15 yrs without a service on it. But hey if it's not broken don't fix it.


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## PCP (Dec 1, 2004)

MJBrown said:


> PCP, I only wish the Autoprop would release a line wrapped around it as easy as you stated. Only had it happen once, and it was my own fault, but it took 2-3hours in a swift current to cut it all off.


I think you have misunderstood me, or perhaps I was not clear. I had also got caught by a cable... once...in a marina one of those in the med that have cables everywhere and no space to steer (they use big inflatable boats to put the boats on the spot).

I was not talking of getting lose after being tangled up, but about avoiding being caught, putting the engine in neutral. If you do that, before hitting the rope, with an autoprop you got a good chance of getting away free.... or I am a very lucky guy


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## christyleigh (Dec 17, 2001)

jrd22 said:


> The Autoprop doesn't have any yearly maintenance except to change the zinc on the end as far as I know. Ours is pretty old, maybe the new ones require something, we haven't had to anything other than the zinc in over 15 years.


 I don't know what year they changed from water lube ? to grease lube but I do know that my first one purchased around 2002 or 2003 required grease. My current one that came with my used boat also requires grease and I think that was installed in the early 2000's also.
A friend of mine had one from back in '96 or so and I believe it did not require grease. 15 years is a longggg..... time...... I would consider pulling it and having the bearings checked if I were you. You don't want to become one of those "blades falling off" harpies because you expected too much of a bearing race  Edit.... I don't remember Exactly how long or how bad the issue was but that friend with the 96ish non-greased had 'extra' play develop in a 'few' years and had it adjusted for that 'slop'. Not scientific I know..... but I hope you understand my concern.


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## MJBrown (Apr 1, 2009)

PCP yes I did misunderstand your comment  Now that you have clarified I totally agree the technique works quite well. I have done the same thing many times when moving through all the crab pots on Cheasapeake Bay.


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## MC1 (Jan 6, 2008)

For cruising, if one is concerned about performance in reverse and/or prop-walk issues, wouldn't a feathering prop be preferred over a folder? When reversing out of a slip, I've read the folders are worse than 2-blade fixed props even, is this the case?

Concerning drag, I don't see why a folder would be much better (if any) than a feathered prop; is there independent data to suggest otherwise? I can't imagine any difference in drag between a good feathering prop and a good folding prop being significant for anything but the most light displacement racing boats being driven at the very top of their performance curve. This doesn't seem relevant to medium / heavy displacement cruisers. Thoughts?


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## FlyinNOE (Nov 28, 2008)

MC1 said:


> For cruising, if one is concerned about performance in reverse and/or prop-walk issues, wouldn't a feathering prop be preferred over a folder? When reversing out of a slip, I've read the folders are worse than 2-blade fixed props even, is this the case?


As far as prop walk is concerned my folder has less than the fixed three blade prop that was on the boat.

As for drag it's probably a minimul difference for anyone cruising, I agree. There is independant data out there if you search for it. Truth is a .1 of a knot is not noticable by most cruisers.

Brian-


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## Valiente (Jun 16, 2006)

dantaden said:


> Valiente, just curious why you decided on a 4 blade feathering and not a 3 or 4 blade folder ?


My boat's a steel motorsailer with a full keel, and I am going to a slightly larger engine (from 52 to 60 HP). The full keel "blankets" the stern somewhat in a way a cutlass bearing aft of a fin keel does not. My shaft angle is near zero degrees.

When I shut off the engine, the four blades will feather to a very small frontal area, and I can rotate the prop shaft to "top center up" to orient the blades for the most minimal of drags. Seems fussy, perhaps, but we are going well offshore and every mile made good will be in part about reducing drag.

The VariProp will allow different pitches in forward and reverse, and I want a relatively shallow pitch for forward that matches the new engine's power curve for economy. In reverse, I want full-on torque for stopping and maneuvering ability. This meant, perhaps ironically, that I wanted a lot of prop blade area for low speeds.

I'll let you know how it all turns out...


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## jrd22 (Nov 14, 2000)

I would have to check the record book, but I think we put the Autoprop on in the mid nineties. No grease required. We have the boat hauled every couple of years and we check to make sure all three blades are still there  . Seriously, it still seems as tight as when new, all the bearings look and feel great and it works just like the day we put it on.


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## PCP (Dec 1, 2004)

MC1 said:


> For cruising, if one is concerned about performance in reverse and/or prop-walk issues, wouldn't a feathering prop be preferred over a folder?


Yes, some feathering props work as well in forward or in reverse.



MC1 said:


> Concerning drag, I don't see why a folder would be much better (if any) than a feathered prop; is there independent data to suggest otherwise? I can't imagine any difference in drag between a good feathering prop and a good folding prop being significant for anything but the most light displacement racing boats being driven at the very top of their performance curve. This doesn't seem relevant to medium / heavy displacement cruisers. Thoughts?


If I remember correctly, the autoprop had made some studies about it. Their
propeller takes way 80% of the drag of a fixed propeller.

Even a folder propeller will ad some drag, so you will probably have a 10 or 15% difference in drag. Not relevant for a cruising boat, but relevant on a racing boat.

Regards

Paulo


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## dantaden (Mar 11, 2009)

From a performance perspective here's how I look at it, theoretically.

> 3 blade fixed - 6 knot/hr average in 24 hours = 144nm/day or 1,008nm/wk
> 3 blade featuring - .5 knot in added performance = 12nm/day or 84nm/wk
> 3 blade folder - .75 knot in added performance = 18nm/day or 126nm/wk

A folder over a feather still gives me the advantage of 6nm/day or 48nm/week. By looking at these numbers, on a long passage (w/folder) I can potentially save time on the engine, make up 3/4 day/wk, and less wear and maintenance on the engine. 

And on occassion, on the race course, being the spoiler is kinda fun.

+ If I can get an efficient blade while motoring, overdrive or other, there's further savings.

As mentioned earlier I've narrowed the field down to Gori 3 Blade Folder or Autoprop, if they fit. I found I have an additional limitation where the shaft is exposed by only 7 1/2 inches to support both zinc and prop.

Still waiting for sizing and costs.


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## PCP (Dec 1, 2004)

dantaden said:


> From a performance perspective here's how I look at it, theoretically.
> 
> > 3 blade fixed - 6 knot/hr average in 24 hours = 144nm/day or 1,008nm/wk
> > 3 blade featuring - .5 knot in added performance = 12nm/day or 84nm/wk
> ...


I don't think you will have such a difference in speed on an heavy boat.

If 0.75 represents the gain in speed that you obtain reducing in 90% the drag of a fixed blade how do you expect that 10% of the total prop. drag represents 0.25 in speed? It seems to me that the difference will be less than 0,1K.

Regards

Paulo


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## BELLATRIX1965 (Jan 2, 2007)

*Variprop - Rugged and Reliable!*

We're cruisers, not racers. 41 foot full-keel sloop with the prop in an aperature. After doing lots of homework, we chose the VariProp 3-blade feathering. This thing is a German-made piece of fine engineering. Two things that the VariProp does that MaxProp can not: 1) You can adjust Ahead and 
Astern pitch easily, with the boat in the water if necessary - the MaxProp must be disassembled to change pitch 2)The VariProp has a built-in brake mechanism that dampens the shift Ahead-Astern or Astern-Ahead. Many props of this type will "clunk" when you shift and they hit the opposite stop - sometimes with a great deal of force. Performance under power Ahead is fabulous, as is reduced drag under sail. Astern is not as good as we had hoped, but much better than the original 2-blade fixed propeller.

Also, regarding maintenance - re-grease EVERY year to displace any seawater that inevitably gets into the hub - cheap insurance!


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## dantaden (Mar 11, 2009)

As mentioned this is just theory, as I have only had the boat for a year and haven't found another owner with a like boat that can give me the difference.

However, based on my hull speed (8.5 knots) a 5-10% (conservative) performance increase would give pretty close to the additional as above. This is assumption since I don't know the drag coefficient of the current prop in my hull design.

Based on other comments and experiences on this thread I think I'm pretty close but won't really know until I fit it - unless I can get further direction and calcs from the community.


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## svsirius (Jan 14, 2007)

Dan

Couple of things having had a Martec folder on my race boat before converting to a 2 blade max prop on that one.

1] delta in speed between the two was less than 0.1 knots in light air which is where the difference in drag will make the most difference. boat was a Frers 36 with a PHRF rating of 90.

2] Since then have installed a 3 blade max prop on the Moody and would never consider another solution. there is a reason everyone compares to the Max Prop. With regard to adjusting pitch without disassembly they do offer a version that allows that [costs more]. We elected not to go with that model and to this day not sure whether that was correct choice or not. We have the prop slightly over pitched on purpose [higher speed/lower RPM] but our engine is oversized for the boat so this is not an issue. It would be nice at times to be able to jump in and either reduce or increase pitch depending on whether we are passage-making or just local sailing where less pitch would give us less prop walk.

There is no perfect solution, however the service / support we have always received from PYI was great.


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## GeorgeB (Dec 30, 2004)

Back when I was Measurer for the C34IA owners association, the folder vs. fixed propeller was a raging controversy in our one-design rule. Fortunately, I had over 20 years of one-design racing results involving hundreds of boats. Our research showed that there was a 30-40 second per mile speed advantage of a 3 bladed folder/feathering prop over a three blade fixed propeller. A much greater advantage for a 2 bladed folding prop. The data didn't show much of a difference between folding and feathering props. Working the numbers, I surmise that the 3 blade folder/feather's offer a 5% advantage which doesn't sound much until you start crunching the 8 and 24 hour numbers. My personal experience is my boat sails much faster in lighter airs and is easier to get to hull speed under sail than motoring which I like as I only have a 25 gal fuel tank.

I have a 3 bladed 15 inch flex-o-fold prop which I am generally pleased with, but I am a little disappointed insomuch it is hard to get the boat up to hull speed (not a problem with the old Michigan prop). I am curious to know the experience of others on this board. Can you tell me your engine displacement, prop diameter and pitch, and, length and type of boat and what kind of motoring economy you are experiencing.<O


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## lancelot9898 (Dec 30, 2008)

svsirius said:


> 1] delta in speed between the two was less than 0.1 knots in light air which is where the difference in drag will make the most difference. boat was a Frers 36 with a PHRF rating of 90.
> 
> 2] Since then have installed a 3 blade max prop on the Moody and would never consider another solution. there is a reason everyone compares to the Max Prop. With regard to adjusting pitch without disassembly they do offer a version that allows that [costs more]. We elected not to go with that model and to this day not sure whether that was correct choice or not. We have the prop slightly over pitched on purpose [higher speed/lower RPM] but our engine is oversized for the boat so this is not an issue. It would be nice at times to be able to jump in and either reduce or increase pitch depending on whether we are passage-making or just local sailing where less pitch would give us less prop walk.
> 
> There is no perfect solution, however the service / support we have always received from PYI was great.


I also have the max prop on my Tayana 37 and have experienced no problems for over 20 years. I haul out every 3 years and repack the hub and recoat the prop. Takes about a full day doing that and while max prop offers a zirc fitting for relubbing the hub, the disassembly allows me to remove all the old grease and repack with new. It's a hassle, but every three years is something I can live with. The major time consumtion is recoating the prop which has held up well with proper underwater primer and hard bottom paint even though using a copper botttom paint is not recommended by max prop. I think the key is proper priming. As far as performance, I don't think there is much difference unless in light air. And that is certainly an advantage. The motoring effenciency is less with a max prop vs a fixed due to the flat vs a curved blade. The max prop also allows setting to a different pitch although once set it remains constant unlike I believe the auto prop changes with speed which is more efficient. I've got the prop set at a pitch of around 14 inches(17 inch diameter) and my WOT setting is less than the Perkins is cabable of achieving in neutral. There has been much discussion on this on other threads. One last comment is that the WOT rpm varies depending on whether the boat is in a current or not, but I've yet to really test that assertion. Passing under a draw bridge with high currents is not the time to be experimenting.  Oh...One other thing is that I'm not sure about the best way to "lock" the shaft with the max prop. For years I just shut down the engine and left the tranny in neutral, but now I'm shutting down when in forward and then putting it in reverse thinking that maybe there is more friction on the shaft allowing the max prop to feather better. (borg warner velvet drive) ??


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## Zanshin (Aug 27, 2006)

I like the Gori on my boat and there is no noticeable prop walk and the "overdrive" setting makes motorsailing or motoring in calm seas a lot more efficient, at 2000rpm I hit 6-7 knots and very little diesel usage.
On the downside, I have had 2 run-ins with lines in the water, once a thick fishing trap and another time last month I ran over my own dinghy painter. In both cases the rope cutter did an admirable job of cutting away the rope remnants but in both cases the Gori was partially fouled and unbalanced and wasn't fully functional until I dove on it and removed the blockage.


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## svsirius (Jan 14, 2007)

lancelot9898 said:


> Oh...One other thing is that I'm not sure about the best way to "lock" the shaft with the max prop. For years I just shut down the engine and left the tranny in neutral, but now I'm shutting down when in forward and then putting it in reverse thinking that maybe there is more friction on the shaft allowing the max prop to feather better. (borg warner velvet drive) ??


We have been using the zirc fittings to re-grease [even underwater] and they work great.

Also regarding feathering the prop, the best practice to my knowledge is to stop the engine with the trans in neutral and then once the engine is stopped move the trans to reverse. Once the prop is feathered we put ours back in neutral. The shaft should not be spinning at all at this point.


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## Gene T (May 23, 2006)

I'm jumping into this discussion a little late but thought I would add some pictures of a Martec. This came with my new (to me) boat. It powers well, reverse is OK but I don't have much experience with it yet. It looks too complicated to me. Service under water looks to be impossible with lots of pins, shims and set screws. Gears will be prone to getting jammed up with marine growth requiring frequent diver attention. Time will tell but I would rather have a Max.


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## Fstbttms (Feb 25, 2003)

Gene T said:


> Service under water looks to be impossible with lots of pins, shims and set screws. Gears will be prone to getting jammed up with marine growth requiring frequent diver attention. Time will tell but I would rather have a Max.


Not true, Gene. There is almost no service to *any* prop, folding, feathering or fixed, that cannot be done underwater by a knowlegable diver with the right tools. Including installation or removal.


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## Gene T (May 23, 2006)

Fstbttms said:


> Not true, Gene. There is almost no service to *any* prop, folding, feathering or fixed, that cannot be done underwater by a knowlegable diver with the right tools. Including installation or removal.


I will probably test you someday when I bring the boat back to SF Bay. You used to service my old boat in Alameda and I have a lot of respect for your work.

However, I watched the this prop come apart and go back together. I would like to know how you can properly lubricate all the different pieces while under water.


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## Fstbttms (Feb 25, 2003)

Gene T said:


> However, I watched the this prop come apart and go back together. I would like to know how you can properly lubricate all the different pieces while under water.


That particular prop requires no lubrication.


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## Nelsoncw (Dec 6, 2006)

I have an Autoprop on my Catalina 42. AB Marine had rebuilt the prop in 2007. In May of 2009 and 225 hours later a blade came off. Buntons Marine replaced the blade for $1500. I had it lubricated every six months. I am always in deep water. It never touched anything but saltwater. I only go to Catalina and back. Other than the lost blade there was not any evidence of damage or distress.

At the time Steve Armitage of AB Marine told me that losing a blade was a rare occurrence and that he did not have an explanation for why the blade fell off. David Sheppard of Brunton's Propellers Ltd, told me losing a blade is an “an exceptional case”. Contrary to their comments the prop has been subject to a recall for lost blades. If you search other support groups and blogs you will find many others that have lost Autoprop blades. It demeans their credibility to say otherwise. 

Although I enjoy the performance of my Autoprop my experience with AB Marine and Brunton's Propellers has been extremely disappointing. They are unwilling to stand behind their product. In all their replies I feel like I am hearing from a politician trying not to give a straight answer.


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## DwayneSpeer (Oct 12, 2003)

*folding*

I have a folding prop. It works well. What can I say!


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## dantaden (Mar 11, 2009)

Thanks everyone for your experience and advise. In the end I decided to on a GORI 3 blade folding prop from AB Marine and after a season in service I am very happy with the additional speed under sail. Under power, the over drive feature is great getting around 6-6.2 knots @ 1500 RPM on my 72hp Mercedes Diesel.

Have emailed AB Marine on a couple of accassions to enquire about blade size but no response - perhaps an indicator for future service performance ?

All in all, very happy with my GORI prop.


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