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

[Loren Beach]

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!

The author seems to have some credibility but then he said something that was incorrect. One of the great things about the design of a feathering prop is that the blades reverse when going in reverse and do present the proper leading edge going in reverse.
His statement would be true, however, for a folding prop.
(I have ten years experience with a feathering prop, and it did display less prop walk than a fixed prop in reverse. Less... but not zero. )

 

[Pete the Cat]

The author seems to have some credibility but then he said something that was incorrect. One of the great things about the design of a feathering prop is that the blades reverse when going in reverse and do present the proper leading edge going in reverse.
His statement would be true, however, for a folding prop.
(I have ten years experience with a feathering prop, and it did display less prop walk than a fixed prop in reverse. Less... but not zero. )

I agree with Loren. I have an Autostream feathering three blade on my Tartan, and the blades are the same forward and backward. Less walk, but not zero.

 

[Vtonian]

I highly recommend his book and spending a quiet day in the marina to practice the exercises.

Jim Stewart's Boat Handling and Docking book received and skimmed. Nifty, short and sweet. I think doing these exercises will be fun and actually kind of therapeutic, in that he's put order to the chaos of all the random docking/handling 'knowledge' I've collected but not experienced, and put it in proper order to practice, along with great insights into more subtle aspects of where to focus one's awareness.

I've got a healthy fear of playing yacht billiards in marinas and I think this will go a long way to allaying that.

Good call, thanks.

 

[Christian Williams]

Heard from Fred Hutchinson at PYI:

Thank you for your interest in the Max-Prop feathering propeller for your Ericson 381. From the information that you provided, the following is my recommendation.

2 Blade Easy 16” diameter by 12” pitch for a 1” shaft $2850.00

3 Blade Easy 16” diameter by 11” pitch for a 1” shaft $3650.00

With regards to powering performance, both two and three blade propellers will power the boat well in flat water. The three blade has a major advantage when going against heavy winds and seas, the three blade will keep boat speed by up to 30% better than the two blade. Moreover, a three blade propeller will run much smoother and reduce vibrations as it is balanced around three points as opposed to two.

Under sail either propeller will increase the sailing speed by about 15% on average. The largest difference being noticed when sailing in light air. When with the fixed propeller the vessel struggles to get through a tack and you have to bear off to gain speed exiting the tack. With the Max-Prop you will be able to carry your speed through the tack much better as you are not dragging a bucket. This means you exit with much more speed and a higher line. Basically it makes it fun to sail in light air when the boat struggles with a fixed propeller.

One of the most important benefits of the Max-Prop is the reverse performance. As the blades rotate 180 degrees in ¾ turn of the shaft you get the same efficiency in reverse as in forward with the Max-Prop, about 80% better than a fixed propeller. This increase dramatically improves the stopping ability and the control in reverse, greatly reducing prop walk.

 

[Christian Williams]

Quotes, March 2024:

Autoprop: r H5-416 for $3669.40. We can take care of the shipping costs ($140) and the duty at 3% ($116.75) so this would be an actual landed price. (Also, Autoprop is offering 10 percent off that price, at the moment.)

Maxprop: 3 Blade Easy 16” diameter by 11” pitch for a 1” shaft $3650.00

Next consideration for me is maintenance. Both props require grease yearly, which in case of Maxprop can be done by a diver (also installation). Not so for Autoprop. My fixed three-blade requires no special treatment. I haul only every three years or so.

A related factor for Autoprop is its reported ability to reduce engine RPMs. One potential downside is that, several owners report, idle gives 3 knots! (the result of automatic pitch change according to rotation speed). The upside is that the Autoprop is said to produce the same boat speed at much lower RPMs. Testimonial here.

If so, that would greatly reduce engine noise from my 5432 diesel, which is much quieter at 2000 RPM than 2500.

Now, perspective: you can buy an engine for what these props cost.

 

[Dave G.]

Yes, initial cost and maintenance is why I stopped considering replacing my fixed prop and I haul her out every yar. If I were to spend that much money it would not be for a prop, probably a new sail or maybe new winches. The biggest benefit to a feathering/folding prop is less drag under sail which diminishes as wind and boat speed increases. Also with the Hurth gearbox you can leave it in neutral which reduces drag from the fixed prop dramatically. Lastly there isn't any prop that eliminates propwalk especially at low speed due to the paddlewheel effect from the blades. The higher the pitch the bigger the paddlewheel effect. Maybe feathering props are better at changing direction the folders but they still have to have a mechanical lag factor to some degree and I guess that's the $64k($3,600) question.

 

[Smixon75]

Quotes, March 2024:

Autoprop: r H5-416 for $3669.40. We can take care of the shipping costs ($140) and the duty at 3% ($116.75) so this would be an actual landed price. (Also, Autoprop is offering 10 percent off that price, at the moment.)

Maxprop: 3 Blade Easy 16” diameter by 11” pitch for a 1” shaft $3650.00

Next consideration for me is maintenance. Both props require grease yearly, which in case of Maxprop can be done by a diver (also installation). Not so for Autoprop. My fixed three-blade requires no special treatment. I haul only every three years or so.

A related factor for Autoprop is its reported ability to reduce engine RPMs. One potential downside is that, several owners report, idle gives 3 knots! (the result of automatic pitch change according to rotation speed). The upside is that the Autoprop is said to produce the same boat speed at much lower RPMs. Testimonial here.

If so, that would greatly reduce engine noise from my 5432 diesel, which is much quieter at 2000 RPM than 2500.

Now, perspective: you can buy an engine for what these props cost.

Good day Christian!

Astral was purchased equipped with a Maxprop 3 blade easy and a Westerbeke 44B4 which produces port prop walk. We do not have experience with any other prop or any other sailboat for that matter. We have no problem backing out of the slip as shown here with prevailing westerlies. We are hesitant to leave the dock in much over 10 knots just to limit the risk of touching a neighbor - 65' across the fairway. I do angle the boat slightly while Luisa backs us out of the slip to assist the maneuver.

We've also backed out of the slip and directly down the fairway from the opposite side of the helm, but with experience, we prefer backing and then pulling forward.

We are pleased with our Maxprop.

 

[bsangs]

My diver greases my Max-Prop (2-blade) in the water each year, which actually amazes me since there's a zerk fitting that has to be inserted and removed with a small Allen wrench each time.

I have no basis for comparison on "Radiance," since this is the prop that came with her, but I'd have to say he's not exaggerating about tacking in light air. We were constantly oversteering the first year, after learning on slower tacking boats for a couple years. And it works very well in reverse, though I've yet to deal with overpowering winds while doing so (knock wood).

 

[RedDog]

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

Would like to know if my 1973 E35 MkII has a prop shaft with splines or tapered with a key.

 

[Pete the Cat]

Some of the feathering props have separately, externally adjustable pitch settings for FWD and Reverse. My Autostream does and I think some of the newer Max props do. I think being externally adjustable (so you can tweak it to perfect without hauling the boat) and being able to set the reverse to a different pitch to suit you, is a plus if you are thinking of a folding or feathering prop.

 

[Smixon75]

My diver greases my Max-Prop (2-blade) in the water each year, which actually amazes me since there's a zerk fitting that has to be inserted and removed with a small Allen wrench each time.

I have no basis for comparison on "Radiance," since this is the prop that came with her, but I'd have to say he's not exaggerating about tacking in light air. We were constantly oversteering the first year, after learning on slower tacking boats for a couple years. And it works very well in reverse, though I've yet to deal with overpowering winds while doing so (knock wood).

Our dive also services the prop in the water every May. He says its very easy. We put together an ammo case with the tools / supplies as well as a canvas bag to take under with him. He didnt use the canvas bag... lol

 

[Dave G.]

Would like to know if my 1973 E35 MkII has a prop shaft with splines or tapered with a key.

Is it original configuration? If so I would expect the latter as I have not seen a direct drive sailboat with a splined shaft.

 

[RedDog]

Is it original configuration? If so I would expect the latter as I have not seen a direct drive sailboat with a splined shaft.

Thank you! I found a prop on eBay that I believe will work in my E35

Sailboat Propeller 12 x 10 2 blade Sailor RH RIGHT HAND 3/4" shaft 12RH 10 | eBay

Find many great new & used options and get the best deals for Sailboat Propeller 12 x 10 2 blade Sailor RH RIGHT HAND 3/4" shaft 12RH 10 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Christian Williams]

Seth, with my current prop I could never make that turn to starboard, backing up. Not even close!

 

[RedDog]

Seth, with my current prop I could never make that turn to starboard, backing up. Not even close!

View attachment 49440

Christian, this prop looks like it will work on my E35. What do you think?

Sailboat Propeller 12 x 10 2 blade Sailor RH RIGHT HAND 3/4" shaft 12RH 10 | eBay

Find many great new & used options and get the best deals for Sailboat Propeller 12 x 10 2 blade Sailor RH RIGHT HAND 3/4" shaft 12RH 10 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[Smixon75]

Seth, with my current prop I could never make that turn to starboard, backing up. Not even close!

View attachment 49440

Hi Christian,

We're just on the other side of the hill from you. If you'd like to swing by one weekend and run the boat to feel the Maxprop, say the word!

 

[Vtonian]

Hi Christian,

We're just on the other side of the hill from you. If you'd like to swing by one weekend and run the boat to feel the Maxprop, say the word!

Not sure what 'other side of the hill' means but this sounds like an offer that can't be refused, or maybe even bribed to sail around the 'hill' and do an actual test with the actual hull and actual prop in your actual slip, Christian.

I was going to say though, it seems like your situation puts the ability of backing to starboard above almost any other consideration. I'd also say to think, if you eventually replace that engine, it may be that being able to run at lower RPM's isn't a benefit, and only being able to slow to 3kn may not be either. Maybe something like an E381 version of a tug boat screw, with lots of responsive power and just enough top speed.

In my case, where my engine wants to run at 2500 RPM, I've been thinking of adjusting my EWOL prop so it can. If you recall, I do hull speed at ~1500 RPM and the engine runs too cool, I have to bury the hull a foot deeper in the ocean to warm the engine up periodically and clean it out. It's designed for improved emissions and running hot is part of how it does it, to the extent that if you don't clear it out regularly, engine damage can occur. This is my interpretation of the Yanmar docs anyway, I haven't had Yanmar or a professional marine diesel mechanic tell me that.

 

[Vtonian]

Just for the record, I saw one of these DockStar things today and although maybe a bit Rube Goldberg-esque, the owner said it'd done the job well for several years, doesn't require doing anything significant to the hull and can be stowed away all the time you aren't fighting a crosswind in a narrow fairway.

$3k-ish with mount

Although, after helping a friend with a challenging back-in docking of his big 30,000lb sailboat in a crossing tailwind (across the starboard bow) that had us blown across the ends of 3 other boats, I'm pretty sure that no bow thruster can solve every problem.