What's wrong with a bit of prop walk?

[Stu Jackson]

One thing I've found that is lacking in many discussions about prop walk is:

Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice

Most don't and also don't use enough throttle to get the water moving.

 

[capnsensible]

One thing I've found that is lacking in many discussions about prop walk is:

Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice

Most don't and also don't use enough throttle to get the water moving.

Spot on. Searush, this was my point, should have explained it a bit differently.

 

[Wansworth]

I agree,lotas of throttle to activate prop walking.I remember coming in across the tide in front of the bows of two yachts so we could moor up in our berth,from what seemed like certain catastrophy turned into a perfect landing with the boat spinning to port against the tide and coming to rest against the pontoon...unfortunatly it was early in the morning and no one noticed!!!

 

[Frankie-H]

One thing I've found that is lacking in many discussions about prop walk is:

Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice

Most don't and also don't use enough throttle to get the water moving.

Oh sh*t, thats why. I only did it 15 times last week.

 

[Searush]

Spot on. Searush, this was my point, should have explained it a bit differently.

Thank you kindly sir, but I think you should be thanking Stu J!

 

[Sybaris]

One thing I've found that is lacking in many discussions about prop walk is:

Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice

Most don't and also don't use enough throttle to get the water moving.

You have just pointed out a very good reason for preferring less or no prop walk wouldn't you say?, it is more consistent i.e. you know what the boat will do and requires far less of all that practice.

 

[Deleted member 36384]

Give Me Less Prop Walk

One of the most manoeuvrable yachts under poet that I have sailed was the Contessa 34. The prop walk was hardly noticeable and it could do anything that a yacht with strong prop walk could do. The Contessa 34 had a very deep spade rudder and 180 degrees of travel (which has its own issues in heavy weather). However, what a joy to berth in any tight situation and fantastic manoeuvrability in astern.

My own yacht, a Rival 41C, has an encapsulated keel, deep forefoot, high bow, large 3 bladed prop (she is in fact over propped), short rudder on a skeg and about 80 degrees travel. In prop walk is a powerful kick to port. The encapsulate keel, about 6" thick on the aft side, along with the pitch of the prop diverts all wash down the starboard side of the keel. The effect of this and the design of the rudder makes her stern go to port in reverse. Only at speed in reveres and on calm days can I get her to astern straight. The high bow will ensure that the wind is the dominant force in making the stern point upwind when going in reverse.

I have many years experience with the Rival 41C and as such I can berth her fairly confidently in most circumstances. However, given the choice I would much prefer the delights of the Contessa 34's steering capabilities although the Rival can be made to go sideways with her excessive prop walk.

 

[wolf]

Not heard that theory, how does that explain the transverse thrust on say a ship, where the prop shaft is pretty close to being parallel to the keel plate.
Here's a simple explanation

http://www.free-marine.com/i3prop.htm

Never used a sail drive,but my initial thought is that if transverse effect is less than for a normal prop, it may be due to the fact that the prop on a sail drive is closer to the center of rotation of the vessel

Just quoting those that know,
http://www.cruisingschool.co.uk/advanced/advanced.htm
http://www.castlemarine.co.uk/your.htm

I can see it being different on ships in ballast but not loaded.

 

[nigel1]

Just quoting those that know,
http://www.cruisingschool.co.uk/advanced/advanced.htm
http://www.castlemarine.co.uk/your.htm

I can see it being different on ships in ballast but not loaded.

Cheers Wolf, thanks for the references, did some googling, and found a complicated paper about this, nice to learn something new . Its limited to high speed props, which is what ours are, but for larger props such as I have a work, its the hydrostatic head on the blades which causes the side thrust.
On some designs of twin screw tugs, its fairly easy to walk the boat sideways due to the huge amount of side force generated by the props, the turning effect is counterbalanced by the rudders. Only works on inward turning props without kort nozzles.
Cheers

 

[Cruiser2B]

Cheers Wolf, thanks for the references, did some googling, and found a complicated paper about this, nice to learn something new . Its limited to high speed props, which is what ours are, but for larger props such as I have a work, its the hydrostatic head on the blades which causes the side thrust.

That cruisingschool explanation seemed to overcomplicate it - obviously if the prop is canted then the pitch of the blade relative to its motion through the water is affected - with the usual downward-canted prop having less pitch on the downward-moving blade than the upward-moving blade in reverse. As you've pointed out there are a number of other factors also at play.

 

[nigelmercier]

The trick is to really know about your prop walk and then use it to your advantage.

Quite.