The Awkwardness of Prop Walk, Illustrated [and Propeller Choices]

[Loren Beach]

We have a folding MaxProp, two-blade, and haven’t experienced any trouble with response from forward to reverse, and vice versa.

I thought that a "max prop" referred to a feathering prop. Am I mistaken?
(I did use a two blade feathering prop for a decade, and finally set it aside for the advantages of a fixed prop. We have a lot of light or no wind days in the NW and speed under power is a good thing.)

 

[bsangs]

I thought that a "max prop" referred to a feathering prop. Am I mistaken?
(I did use a two blade feathering prop for a decade, and finally set it aside for the advantages of a fixed prop. We have a lot of light or no wind days in the NW and speed under power is a good thing.)

If I’m using the wrong terminology, my apologies. Was told it was a “folding” prop. Not necessarily certain I know the difference between folding and feathering. I know it closes up and works very well.

 

[Dave G.]

Here is a test that shows a somewhat scientific comparison.....

Folding and feathering propeller test

Which is the best folding or feathering propeller for you? Emrhys Barrell compares 15 props in a test of speed, thrust, drag, stopping speed and propwalk

www.yachtingmonthly.com

 

[Neil Gallagher]

Christian, i actually commented earlier in this thread regarding setting the pitch going from foward to reverse (and vice versa). It does take a few seconds for the pitch to set with the Autoprop, but I usually "goose" the rpms (approx 2500) momemtarily until it bites then back down the rpm for the situation. The fairway of the marina I am in is maybe 70' wide so I've got a little more room. This propulsion responsiveness caveat has not been an issue for me in any siituation including dockimg in multiple marinas. I think its really just gettimg use to the performance characteristics of the prop. Hope this helps.

 

[Vtonian]

My $0.02 on props: mine came with an EWOL E3 Orion, which they say needs to be handled carefully between forward and reverse to not damage its internal gears. That makes me a little concerned thinking about if I ever have to jockey it hard in a tight marina with the wind up.
That said, if I *want* to walk the stern to port, it can do that exceedingly well, as I learned with my very first docking attempt, at a fuel dock. The attendant turned politely away...

 

[David Grimm]

Christian! YIKES! Gets me all full of nerves just reading about your situation there. My past marina was a NIGHTMARE! Looks like I had s bit more room to maneuver but not much. I have the 3 blade, I assume stock prop and I get a decent amout of propwalk. The old salt grumpy dockmaster had to YELL commands and foul insults at me when I lost the walk into my slip many times. In the beginning I would just call him on the radio so he would be ready. He was a miserable bastard however he knew how to drive a boat. Once you put down your pride and were willing to take the barrage of screaming commands and insults you knew he would get you out of trouble. "HARD OVER STARBOARD...COME ON I SAID HARD OVER....FASTER... NOW GIVE ME TWO BUMPD FORWARD.... NEUTRAL. HARD OVER PORT SPINN THAT WHEEL FASTER ... REVERSE... GIVE ME TWO BUMPS... WAIT FOR IT. WAIT FOR IT. DO NOTHING. NOW HARD OVER STARBOARD ... and so forth. Lol.

We typically always had strong current in one direction or the other (blue). The wind (light blue) always came from the north west pushing me toward the rocks (orange x)

The red is my slip. Stern in. I would have to walk the boat out sideways using the current being careful not to loose the bow to the wind. When clear of the last slip I would back down and do the same walk till I got to exit.

As time went on I learned to cheat a little and would walk the boat out with my hands to the end of the finger and aim her and jump on and gas it hard and drive out forward. It was risky. Coming in at night in high wind was always fun too. This is part of the reason I left. Just too stressful. I love the marina I'm at now. Easy cheesey. Lol.

 

[Bolo]

Nice! I'm going to have to try that. I go forward down the fairway then use prop walk/wash to turn the boat and back into my slip. Great video

To be honest I’m not that smart of a sailor to have come up the “stern first” maneuver and did see an old salt do it many years ago docking his boat quietly and easily like I mentioned in my previous post. But I do have some dock neighbors that do come down the fairway bow first, stop the boat and then try and back in. It’s a 50/50 deal as far as I’ve observed. Sometimes they’re successful, sometimes not and when it’s not there is the usual gnashing of teeth, swearing, shouting and banging into pilings. Even solo I can bring the boat in, stop it at about 75% into the slip, grab a spring line (that has a loop tied into it at just the right spot), off the outermost piling, which is in reach and throw it over the mid-cleat. The in reverse with zero throttle and the boat settles back into the slip while I take my time to tie off the other lines.

 

[Mr. Scarlett]

My worst nightmare, and they want to move me further down the slipway to do repairs in my slip! My slip and prop walk are similar to yours, but I leave in the other direction. A healthy dose of throttle usually gets things going enough to make it out no problem. Only had to do the fore and aft shimmy once. I've thought of a line going around a cleat at the end of the dock and back to the starboard quarter or midships but there's the very unseamanlike risk of leaving a line in the water attached to the dock. When the wind is up I will walk the boat all the way out and turn it 90 degrees since my neighbor is shorter. Too bad, looks like yours isn't.

 

[Vtonian]

First, I assume everyone else is smarter and more experienced than me but my friend is locked in a slip with similar woes, so I've been studying up on line handling for singlehanded docking and my *theory*, based on book/video learning, is something like this should work (ignoring the fear factor):

When trapped at the end of the fairway, using lines looped around dock cleats so they can be released and retrieved from the boat, set a line from an aft port cleat ahead to a dock cleat, and another line from a starboard midship cleat astern to another dock cleat.

Then put the boat in reverse to spring the bow off the dock.


The boat will rotate, bringing the bow out towards the fairway.


Put the boat in forward to move away from the dock and when the stern is clear, hold the starboard line to start the turn into the fairway.


Once the boat is pointed well enough down the fairway, release the starboard line and boogie.


I would assume there would be a point where the wind coming up the fairway might require more power to overcome with the starboard line attached astern, so maybe an alternative would be to run a starboard line to the end of the first finger pier and pivot off that.
For that matter, if it's possible to run a line to that first finger pier, it might work to run it to a starboard bow cleat and pull or winch the bow out.

Obvious things to me would be:
- scary, lots of money to be lost banging around on yours and other people's boats if something goes wrong
- scary, lots of line handling for a singlehander, and just a little carelessness with multiple lines could put one around the prop
- wind and current could shift so not sure what the plan B would be, much less plan C or D

Still, what if conditions were such that you *had* to do it? In theory, wouldn't this work?

FWIW, I have been able to do just a little experimenting with my singlehanding dock line theories at our empty park marina and so far have only been marginally successful, tapping a piling once, scraping the dock a little once, and always having to adjust my lines in real time when my napkin geometry isn't close enough.

That said, I'm convinced that there should almost always be a way to control a boat with engine and spring lines when leaving a dock and I'll keep experimenting to find out. Should I abandon that concept?

OTOH, arriving is a whole nother matter...

 

[southofvictor]

If the wind is blowing hard down the fairway it can be tough to get the bow past its position in your third sketch because you don’t yet have enough speed to track well and keep it from blowing off. If that’s the case you may be able to reverse your operation and spring the stern off then back down the fairway. That way the wind can help you get lined up with the fairway rather than fighting you as it pushed the bow faster than the stern. As long as you can get enough way on to overcome prop walk before it becomes a problem the boat should track well backing stern to the wind down the fairway because the wind will keep the lighter bow downwind of the heavier stern.

 

[G Kiba]

It is easy to forget that you may be able to just stay were you are until the wind relents or you can get more folks around to help. I think as humans, there is a compulsion to get back home to where it is safe. Sometimes it is better to stay put and come back the next day. I have done this on trips up and down the delta and to the bay. Why stress out if you don't have to?

 

[Vtonian]

If the wind is blowing hard down the fairway it can be tough to get the bow past its position in your third sketch because you don’t yet have enough speed to track well and keep it from blowing off. If that’s the case you may be able to reverse your operation and spring the stern off then back down the fairway. That way the wind can help you get lined up with the fairway rather than fighting you as it pushed the bow faster than the stern. As long as you can get enough way on to overcome prop walk before it becomes a problem the boat should track well backing stern to the wind down the fairway because the wind will keep the lighter bow downwind of the heavier stern.

I see, if the wind is really up, backing into it is pretty much your only choice for the reasons you explain. I was thinking the 10kn would be manageable but now I visualize doing it myself, I can imagine where the slightest miscalculation or wind shift would, if you were lucky enough not to plough into someone's beloved yacht, put you back on the zigzag path to point of origin.

 

[driftless]

I feel very fortunate to have had an ASA 101 instructor who literally wrote a book on docking. It was my first experience on a large auxiliary powered sailboat. The entire first day we didn't leave the marina and never set the sails. We just maneuvered under power and practiced docking in all different configurations. Jim was an excellent instructor. That day was an amazing learning experience and confidence builder. I highly recommend his book and spending a quiet day in the marina to practice the exercises.



Our slip is configured similarly to Christian's, but we've got an extra 15 feet of width in the fairway. Also a wider slip - just a pelican pole in between us and the next boat over instead of another finger pier. This allows us to severely cock the boat in the slip with bow in and stern out from the port side tie before casting off. That makes a huge difference. As others have mentioned aggressive reverse throttle to get underway and steerage on, coupled with the extra space to allow for the initial (though very manageable) prop walk, makes it a very straightforward (straightreverse?) maneuver. If the wind pushes the bow down to starboard so I can't make the reverse turn to starboard, I just turn port instead and back out the fairway.



We've got what I believe is the original 2-blade michigan prop and find it to be efficient forward and reverse. The walk is mostly useful and rarely problematic. Anticipated reverse prop walk can be used for maneuvering if applied correctly and coupled with forward prop wash. It often takes more throttle than I expect, but short bursts of power keep speed manageable.

 

[Martin King]

I've got a similar situation to Christians with a narrow fairway, crosswind, and a fixed 3 blade for a prop. The E31 does not like to back up like most Ericsons, and the outboard rudder seems to exacerbate the problem. To leave my slip, a crew member is stationed on the dock pulling the bow over hard to port as we back out, and if we don't come out at about 45 degrees, we are screwed if there is any breeze blowing. The bow will just blow off downwind and trying to pirouette around in the narrow channel is futile. There just isn't room to get enough way on to bring the bow around. Backing out the long fairway isn't an option as the boat refuses to back up straight even with way on and the transmission in neutral. The best solution to the heavy prop walk problem I have found is the max prop or equivalent feathering propeller. I had installed one on my previous boat, an E39 and while the boat still did not like backing up, the prop walk issue was greatly mitigated.

 

[Vtonian]

I feel very fortunate to have had an ASA 101 instructor who literally wrote a book on docking. It was my first experience on a large auxiliary powered sailboat. The entire first day we didn't leave the marina and never set the sails. We just maneuvered under power and practiced docking in all different configurations. Jim was an excellent instructor. That day was an amazing learning experience and confidence builder. I highly recommend his book and spending a quiet day in the marina to practice the exercises.

ordered...

 

[Vtonian]

I've got a similar situation to Christians with a narrow fairway, crosswind, and a fixed 3 blade for a prop. The E31 does not like to back up like most Ericsons, and the outboard rudder seems to exacerbate the problem. To leave my slip, a crew member is stationed on the dock pulling the bow over hard to port as we back out, and if we don't come out at about 45 degrees, we are screwed if there is any breeze blowing. The bow will just blow off downwind and trying to pirouette around in the narrow channel is futile. There just isn't room to get enough way on to bring the bow around. Backing out the long fairway isn't an option as the boat refuses to back up straight even with way on and the transmission in neutral. The best solution to the heavy prop walk problem I have found is the max prop or equivalent feathering propeller. I had installed one on my previous boat, an E39 and while the boat still did not like backing up, the prop walk issue was greatly mitigated.

I know, a Minkota trolling motor mounted on the bow, with a remote, like a bass boat...

 

[Martin King]

I know, a Minkota trolling motor mounted on the bow, with a remote, like a bass boat...

Ha! You'd be better off installing a Lewmar bow thruster.

 

[nquigley]

Regarding Autoprop:

Neil, as an owner, can you speak to this? I would require near-instant response when shifting forward to reverse at very low RPMs. and perhaps as Dave suggests that might be a factor with a folding/reversing propeller in my particular situation.

(I currently have a three-blade 15" Michigan prop pitched 12. Creates big prop walk)

I don't have a folding prop - just the original 2-blade fixed prop - probably OEM.

 

[Christian Williams]

I heard from Rod Sampson of Autoprop in response to this thread:

Interesting read on the blog.

You have very different propulsion systems on the boats mentioned. Each has benefits and limits, there really is no right choice, just right for the environment you sail in as one contributor mentioned. I have attached a PDF of a prop walk description. It is fairly decent and gives a fitting analogy without having to delve into hydrodynamic pitch angles or vectors! Remember the prop walk is caused by shaft inclination causing an asymmetric loading which is sensitive to prop diameter, rpm and propeller pitch. Autoprop with self pitching blades means that the blades generate lift at a lower pitch and hence rpm which is the biggest contributor to reducing prop walk. Also the blades are bi-directional and flip over so the leading edge always leads forward. With every other prop you have the trailing edge going forward in reverse, which needs… a lot of pitch and rpm to move - causing prop walk!

Maxprop or a folder may slightly edge Autoprop out on sailing speed by a tenth of a knot, but if you use the engine and sail, it really does make sense to consider Autoprop.

Please also have a look at the Selgen test.* The Yachting Monthly report is not scientific, but a bunch of journalists having a go. Once you do uncertainty analysis on the results it merely becomes a report on how good companies size their propellers and less about the comparisons because you are not comparing apples to apples. More crab apples to cooking apples etc.. I ran a propeller cavitation tunnel for 10 years and have a PhD in propeller cavitation, the Selgen report is Scientific and a real benchmark, something I would have written when running those type of open water tests.

Finally a note on service. Any of the sailboat props need service. If you choose to own an Autoprop, you will need to take care of it. Comes with a 3 year warranty. You grease every 1-2 years, swap anodes as normal and every 750 engine hours replace the bearings. ALL the wearing parts are replaceable so if you keep the bronze protected with the anodes Autoprop will not wear out like every other geared sailboat propeller.

*The Segeln Magazine test is a tech report translated from the German, a PDF I cannot attach.

 

[Sam Vickery]

It is wise to develop boat handling skills and to know how your boat responds. If possible could your friend request to be moved to a different slip where it would be a little easier to dock?

Sam
North Star 1986 32-3
Universal 25
Dana Point, California