Autoprop

[Celestialsailor]

Originally Posted by EWOL Props

Well... it is one of the possible solutions, however keeping a fixed prop you would have to renounce to higher speed and have that tedious noise of rotating shaft and prop under sail, you would still have lower maneuverability. All this can be solved easily with a good and solid feathering prop

...and a few extra thousand dollars.

[Pete7]

Originally Posted by larsake

I am in Newlyn, Cornwall and we have lost one of the blades in our 3 blade Gori-propeller.

We hope to have it fixed on Monday, but I am not sure which new propeller to choose. Theoretically I think Autoprop sounds like the best alternative, but is there someone out there having experience of Bruntons Autoprop??

We have a fixed two blade prop, but two years ago chartered a sister yacht out of Oban with a Bruntons. As we came into Tobermory, I dropped into neutral expecting the yacht to slow down and stop alongside the pontoon. Only it didn't it just kept gliding along, shocked and running out of space a sharp burst of reverse was needed. The difference in drag was huge and really quite impressed the way we just seemed faster my own identical yacht. If only the budget would allow, but a full cockpit cover is first.

Pete

[fourlyons]

Originally Posted by Pete7

We have a fixed two blade prop, but two years ago chartered a sister yacht out of Oban with a Bruntons. As we came into Tobermory, I dropped into neutral expecting the yacht to slow down and stop alongside the pontoon. Only it didn't it just kept gliding along, shocked and running out of space a sharp burst of reverse was needed. The difference in drag was huge and really quite impressed the way we just seemed faster my own identical yacht. If only the budget would allow, but a full cockpit cover is first.



Pete

Yep. If you care about sailing performance and really like to sail, you care about the drag. I get it that for some just getting out on the water is enough, nothing wrong with that. And of course there are always budget constraints and trade offs to make.

You can often buy a used Autoprop for less than a new fixed prop. But any feathering or folding prop is better than a fixed prop from a sailing perspective.

[Jamme]

I swapped a fixed 3-blade prop with an Autoprop 3-blade prop a couple of years ago. I experienced noticeable results in this order: motorsailing (really a game changer; allows to use the engine at low RPMs while still putting an actual load on it; decent speed improvement, and some gains in fuel consumption), reverse (better traction), and just sailing (more silence and minor speed improvements).
No affiliation whatsoever with Autoprop or any other brand; just my personal experience from an actual purchase. YMMV.

[fourlyons]

Originally Posted by Jamme

I swapped a fixed 3-blade prop with an Autoprop 3-blade prop a couple of years ago. I experienced noticeable results in this order: motorsailing (really a game changer; allows to use the engine at low RPMs while still putting an actual load on it; decent speed improvement, and some gains in fuel consumption), reverse (better traction), and just sailing (more silence and minor speed improvements).
No affiliation whatsoever with Autoprop or any other brand; just my personal experience from an actual purchase. YMMV.

Good point about the motor sailing. It's hard to describe without experiencing it, but it's nothing like doing the same with a fixed prop.

[ItDepends]

I have had the rare experience to have sailed the same hull design and the same engine with a fixed prop, a MaxProp feathering Prop, and an AutoProp. Which is best? It Depends....

I almost never "motorsail" so that doesn't matter to me. If it is something important to you, then the Autoprop might be the way to go. But there is a caveat that seems to go unmentioned. The Autoprop is MUCH more sensitive to fouling than any of the other choices. Even a slight difference between the blades destroys the performance, even to the point of making it vibrate tot he point of uselessness if the three blades can not take the same pitch. One owner claimed that "a single barnacle" on one blade was enough. I think that is an exaggeration, but not much of one. If you are not going to dive on the prop and keep it REALLY clean, it might be problematic for you.

In normal motoring, I couldn't really see the difference between those choices. MAYBE the Autoprop was a BIT slower off the mark than the others, and took more throttle in close quarters to get moving and then to stop, but it was just a difference, not a problem. Certainly speed vs RPM wasn't noticeably different on any of these boats, and top speed not at all.

Feathering props are SUPPOSED to be much better performaters in reverse than fixed blade props, but again, I can't say the difference was worth anything.

Sailing, there is no competition. The fixed blade unit is like dragging a BIG bucket behind the boat. Better of course if you can let it spin, but that comes with it's own cost. Theoretically, the Autoprop carries a bit more drag than the Maxprop, but it is not obvious in normal sailing.

On my boat I have a MaxProp, with a fixed blade as a spare. I'd not swap out to the Autoprop if it was free. But that's just me. People who motorsail a lot might think differently.

[fstbttms]

Originally Posted by ItDepends

On my boat I have a MaxProp, with a fixed blade as a spare.

What builder & model boat do you have? What model Max Prop?

[torrmundi]

Here's an informative comparison test of folding props.
https://www.yachtingmonthly.com/gear...ler-test-29807

It shows the drag reduction achieved by a folding prop, which is remarkable: "In the graph above, you can see that at 5 knots, a fixed three-blade prop with its shaft locked creates almost half as much drag as the entire hull."

Then it shows the forward and reverse pull of each prop. Lots of difference!

[GreenWave]

Originally Posted by torrmundi

Here's an informative comparison test of folding props.
https://www.yachtingmonthly.com/gear...ler-test-29807

It shows the drag reduction achieved by a folding prop, which is remarkable: "In the graph above, you can see that at 5 knots, a fixed three-blade prop with its shaft locked creates almost half as much drag as the entire hull."

Then it shows the forward and reverse pull of each prop. Lots of difference!

While I am sure many put their boat in gear to lock the prop if you have a Yanmar mated with their standard transmission choice you won't want to lock it.

[Noisykate]

We have an autoprop, and are fans. We've had the boat 8 years, and it was fitted by a previous owner.

For:
No propwalk in fwd or rev.
Power in reverse.
Self-adjusting, self-feathering.

Against:
Has to be dismantled and greased annually (more recent ones have grease points on and can be left longer)
Expensive to replace

We have never fouled it, although that is more to do with our long-fin keel, I suspect.
Have never heard of them dropping blades.
We did have a problem with one blade getting stiff, because the previous owner had not realised they need servicing each year. Water had got in (not a problem, within reason) but left over a long period it was enough to rust a bearing to the point where one blade got a bit stiff.
Servicing is easy enough; dismantle each blade, clean, regrease, reassemble. Takes about an hour per blade. Worse in the contemplation.
Happy to answer any other questions.

[Celestialsailor]

I really can't see how locking the prop creates less drag when a free-wheeling prop seems like it is "giving" to the resistance, transferring the energy through rotation.

[j.g.evans]

I have had 4 props on a 36' sailboat. 1) fixed, 2) Martec folding, 3 Autoprop, 4) Autostream feathering.
I replaced the fixed prop with the Martec to reduce drag sailing. It was good in forward and lacked bite in reverse. My Autoprop lost a blade and I could not find anyone who cared, neither dealer nor manufacturer. Early on I ran boat speed versus engine RPM tests and was surprised the curve was linear before flattening out. It was very similar to the three other props. I did find that the Autoprop picked up weeds and I often had to dive to clear them. I now have the Autostream feathering prop which I like for low drag and the ability to adjust it in the water and being able to have a high pitch in reverse. It is also SS on a SS shaft and I expect less corrosion and even less barnacle growth. I will leave off the zinc when my last one is gone to confirm my theory on barnacle growth. On another boat I had a bronze prop on a bronze shaft with no zinc and I had no barnacles.

[nmuir]

We have autoprops as we are a motorsailer, and they do seem the best for motorsailing due to their infinitely variable pitch.

If we either just sailed or just motored alone, then I would have gone with a less expensive folding / self feathering prop. Autoprops are expensive.

Been very happy with the performance of them, though we are benchmarking against the old fixed blade props - and any folding prop will be better than a fixed blade.

[Greatest Lakes]

I have been pleased with my flexofold. I figured it was good for .9 knots with a 10 knot breeze.

[Pete7]

Originally Posted by Celestialsailor

I really can't see how locking the prop creates less drag when a free-wheeling prop seems like it is "giving" to the resistance, transferring the energy through rotation.

A locked propeller doesn't have less drag. Peter MacKensie from Strathclyde University did a lot of work on this subject and worth a read:


https://strathprints.strath.ac.uk/5670/