Autostream Propellers - feedback?

[Pete the Cat]

After 15 years and 25K miles, I am totally sold on the AutoStream feathering three blade. It is rugged (I picked up a 1" line that sheared my coupling and ripped out my cutless bearing and did nothing to my Autostream), easily adjustable in foward and reverse (I have no idea how folks actually get props matched to their engines and boats without this feature on all props) , and it added a bit more than half a knot to my sailing over the prop it replaced. No corrosion and fast and competent advice from Martec who sold it to me and advised on my self installation (easy). The company provides replacement delrin bearings with the prop, but I have never needed anything more than greasing it and putting on a new zinc. On my Central American cruise, I met two folks with problems with Max Props being bent and looking for repair parts and help--not sure that says anything bad as it is a small number. But it qualifies as one of the best investments in my boat after all these years. I have no business affiliation with Martec or AutoStream--I am just a customer.

[Schapera]

Thanks for the update, very helpful....!

[Jim Cate]

We had a bronze Autostream 3 blade on our previous boat. After a couple of thousand hours and lots of miles, it was in like new condition when we sold the boat in 2005. Performance was typical for a feathering prop: good static thrust in forward and reverse, feathered easily under sail, easy to adjust pitch free-diving. No complaints.

But, as with ALL feathering props, there is a loss of efficiency compared to either fixed or folding props due to the necessity for flat blades with no twist to their shape. In our case, moving from a Martec Elliptic two blade folder to the Autostream cost us about 25% in fuel economy. YMMV (literally!).

Cheers,

Jim

[Stumble]

I just added one to a Beneteau 381. It made a world of difference, though the boat was massively under propped from the last owner. We went from a 12" fixed to a 16" (auto stream actually recommended a 18"), so I don't really have a comparison. Though it does have a lot less prop walk than my old Max-prop.

Take a look at the Yachting Monthly article where they tested about 15 different props all on the same boat. http://www.flexofold.com/upload_dir/...onthly_low.pdf based upon that Test we really wanted a Flex-o-fold, but couldn't find a North American distributor, and when I contacted the factory directly never got an answer on size (I'm still waiting 4 onths later). Auto-stream had a recomendation in two days.

[Dockhead]

Originally Posted by Jim Cate

But, as with ALL feathering props, there is a loss of efficiency compared to either fixed or folding props due to the necessity for flat blades with no twist to their shape. In our case, moving from a Martec Elliptic two blade folder to the Autostream cost us about 25% in fuel economy. YMMV (literally!).

Cheers,

Jim

I've never heard this about either Autostream or MaxProp. If there is a difference in efficiency compared to fixed or folding props, I bet you can more than compensate for it by adjusting the pitch exactly to your boat -- something quite hard to do with a fixed or folding prop.

For sure you don't have this problem with the Autoprop, which does have twist in the blades. Besides that, the Autoprop self-pitches, which usually allows you to run at lower revs than even a perfectly adjusted Max-Prop or Autostream. You definitely will get an increase in fuel economy with an Autoprop, and besides that less noise and engine wear (at the expense of some sailing efficiency, however).

But I've never heard a single bad word about either Autostream or MaxProp. I think you can't go wrong whatever you choose. In any case, it will be a huge leap from a fixed prop.

[Stumble]

Dockhead,

There is no question that a properly sized and pitched fixed prop will be more efficient than a folding or feathering prop. That being said finding a boat that has a properly pitched, and sized prop is pretty rare. Most people aren't willing to spend the money to swap out prop after prop to get exacally the right size. So they put on something that's good enough, and keep going (this is particularly true of sailboats).

So you are right that in practice a feathering/folding prop is likely to be as efficient as a fixed, just because it is so much easier to play with getting the right pitch than with a fixed.

But getting into a whole prop sizing discussion is I think beyond this thread, and defiantly beyond y ability. Though I have seen engineers try and work it out, though it still is likely to require at least a few swaps to get right.

[Dockhead]

Originally Posted by Stumble

Dockhead,

There is no question that a properly sized and pitched fixed prop will be more efficient than a folding or feathering prop. That being said finding a boat that has a properly pitched, and sized prop is pretty rare. Most people aren't willing to spend the money to swap out prop after prop to get exacally the right size. So they put on something that's good enough, and keep going (this is particularly true of sailboats).

So you are right that in practice a feathering/folding prop is likely to be as efficient as a fixed, just because it is so much easier to play with getting the right pitch than with a fixed.

But getting into a whole prop sizing discussion is I think beyond this thread, and defiantly beyond y ability. Though I have seen engineers try and work it out, though it still is likely to require at least a few swaps to get right.

I think we are in agreement.

Feathering props can be adjusted (I don't know about folders), so one is much more likely to go to the trouble to get the pitch right. But even then the pitch will only be just right for one set of condition.

A self-pitching prop doesn't need to be adjusted, and will have the right pitch for a great variety of conditions. This is a really huge advantage, especially for motor-sailing.

The Autoprop has a disadvantage in that it droops one blade when feathered, which gives it the worst sailing performance of any variable geometry prop (still vastly better than a fixed prop, however).

The new MaxProp "Ecowind" self-pitching prop apparently solves this problem with springs in the blades. Whether its flattish blades are inherently less efficient, I don't know. The Autoprop has properly curved, twisted blades like a good fixed prop.

[Stumble]

Dockhead,

I think so as well.

I would point out that the drag from a folding prop was measured, and they really couldn't get any readings. In practice the drag was so low the measuring rig wasn't accurate enough to tell the difference between types.

Yachting Monthly also combined the drag reports for all the feathering props as well. I don't know if that was because the difference was so minimal, or measuring problems. But the study's findings basically said that a feathering prop will have 5% (if I am remembering correctly) the drag of a fixed prop.

For sailors it seems the single best investment for increasing sailing performance is to get rid of a fixed prop, almost without regard to which you switch too.

[Jim Cate]

Originally Posted by Dockhead

I've never heard this about either Autostream or MaxProp. If there is a difference in efficiency compared to fixed or folding props, I bet you can more than compensate for it by adjusting the pitch exactly to your boat -- something quite hard to do with a fixed or folding prop.
********
Well, I guess we will have to disagree on this, Dockhead. In our case, the folding Martec and the (after some in the water adjustment) Autostream both allowed the engine to reach the redline at hull speed which is one of the accepted ways to pitch a prop. The difference in fuel burn/mile was repeatable and significant. Discussions with prop professionals attributed it to the untwisted blade shape on the Autostream (which is common to all feathering props because of the way they achieve reverse thrust).
*******

For sure you don't have this problem with the Autoprop, which does have twist in the blades. Besides that, the Autoprop self-pitches, which usually allows you to run at lower revs than even a perfectly adjusted Max-Prop or Autostream. You definitely will get an increase in fuel economy with an Autoprop, and besides that less noise and engine wear (at the expense of some sailing efficiency, however).
*****
I agree that the Autoprop does not suffer from this basic inefficiency. However, there are a lot of negative experiences with Autoprop to go along with the positive. Not an efficiency issue, but vibration, bearing life and general performance. There have been long threads on this subject here on CF and other fora, and two of our close friends have eventually given up on their Autoprops and gone back to feathering. When they work right they seem quite remarkable, especially (as you say) when motorsailing.
***
But I've never heard a single bad word about either Autostream or MaxProp. I think you can't go wrong whatever you choose. In any case, it will be a huge leap from a fixed prop.

While I have indeed heard folks who didn't like their Maxprop, I agree that either one of those props will, if adjusted correctly, make a big improvement in the performance of ones boat.

Cheers,

Jim

[Captain Bill]

I have autostream props on my boat and am relatively happy with them. I do give up some efficiency because of the flat blades. My boat is a full knot slower at cruise speed than the factory says it is with the standard folding props. The blades are pretty tough, but I hit a mast on an uncharted wreck and slightly bent one of the blades which resulted in some vibration. The hub protected the saildrive though it did stall the engine. Fortunately I was at idle at the time. I've had no corrosion issues at all.

[Dockhead]

Originally Posted by Jim Cate

Originally Posted by Dockhead
I've never heard this about either Autostream or MaxProp. If there is a difference in efficiency compared to fixed or folding props, I bet you can more than compensate for it by adjusting the pitch exactly to your boat -- something quite hard to do with a fixed or folding prop.
********
Well, I guess we will have to disagree on this, Dockhead. In our case, the folding Martec and the (after some in the water adjustment) Autostream both allowed the engine to reach the redline at hull speed which is one of the accepted ways to pitch a prop. The difference in fuel burn/mile was repeatable and significant. Discussions with prop professionals attributed it to the untwisted blade shape on the Autostream (which is common to all feathering props because of the way they achieve reverse thrust).
*******

For sure you don't have this problem with the Autoprop, which does have twist in the blades. Besides that, the Autoprop self-pitches, which usually allows you to run at lower revs than even a perfectly adjusted Max-Prop or Autostream. You definitely will get an increase in fuel economy with an Autoprop, and besides that less noise and engine wear (at the expense of some sailing efficiency, however).
*****
I agree that the Autoprop does not suffer from this basic inefficiency. However, there are a lot of negative experiences with Autoprop to go along with the positive. Not an efficiency issue, but vibration, bearing life and general performance. There have been long threads on this subject here on CF and other fora, and two of our close friends have eventually given up on their Autoprops and gone back to feathering. When they work right they seem quite remarkable, especially (as you say) when motorsailing.

While I have indeed heard folks who didn't like their Maxprop, I agree that either one of those props will, if adjusted correctly, make a big improvement in the performance of ones boat.

Cheers,

Jim

I've been lucky with mine, I guess. I've had Autoprops on two different boats going back 15 years, and nary any problem. The motorsailing is amazing. The biggest problem, actually, is that my boat makes over 4 knots at idle -- the blades pitch up. It does cause some problems docking -- I have to shift in and out of gear to get the speed down to a manageable level. Otherwise, the prop is a sheer joy.

Someone said that if the boat pulls redline in gear, it's propped correctly. Well, not really -- you can only say that it's not overpropped, at least not at redline. It might well be underpropped, and at less than full load or full revs, God knows what is going on with it. If you motor at redline and at hull speed all the time, then you don't need a self-pitching prop. Otherwise, it is a truly great thing.

Over the last year I have cut my cruise speed under motor down from 8.5 to 9 knots to 7.5 to 8 knots and I'm burning half the fuel with the help of the Autoprop. 2500 to 2800 rpm has become 2000 to 2200. The difference is amazing -- in noise as well as fuel consumption.

[mikefossl]

I've had mine on for the last few years. Very easy to keep clean as I can happily hack away with a old knife without worrying about gouging the prop. I hadn't considered the efficiency aspect but I guess being able to fine tune the pitch is some compensation.

[cwyckham]

Originally Posted by Dockhead

Someone said that if the boat pulls redline in gear, it's propped correctly. Well, not really -- you can only say that it's not overpropped, at least not at redline. It might well be underpropped, and at less than full load or full revs, God knows what is going on with it. If you motor at redline and at hull speed all the time, then you don't need a self-pitching prop. Otherwise, it is a truly great thing.

.

I have an autostream and was planning on adjusting it by using the "redline in gear" test. Can you explain your comments on why this doesn't work?

I was planning to set the max rpms at 3300 in neutral and then adjust propeller pitch until full throttle in gear gives me 3000 (my max operating rpm). This won't work?

[haidan]

I was given an autostream prop that has a metalurgical problem with the blades or something, serious pitting throughout all three blades, one blade broken due to pitting right through another one well on it's way. I haven't looked into what a set of replacement blades costs and I'd be curious as to whether they've used a different grade of stainless. Their site says they use 2507 and 316 stainless.

[Captain Bill]

Originally Posted by haidan

I was given an autostream prop that has a metalurgical problem with the blades or something, serious pitting throughout all three blades, one blade broken due to pitting right through another one well on it's way. I haven't looked into what a set of replacement blades costs and I'd be curious as to whether they've used a different grade of stainless. Their site says they use 2507 and 316 stainless.

Mine are now 11 years old and don't have a mark on them. I replace my prop zinc about every 9 months as they go pretty fast. The saildrive zinc lasts about 2 years. I guess if the prop zinc was gone it might get eaten up fairly rapidly.