Prop Kick

[Jamesuk]

Hi Very quickly,

Prop kick : in reverse stern goes to stbd in forward stern continues to go to Stbd? is that right ? Forget the rudder on this question keep it simple.

cheers James

 

[Twister_Ken]

Hi Very quickly,

Prop kick : in reverse stern goes to stbd in forward stern continues to go to Stbd? is that right ? Forget the rudder on this question keep it simple.

cheers James

It all depends.

In theory, stbd kick in reverse should mean port kick ahead but much depends on the individual boat's underwater shape and the wind and current at the time.

My old boat - in theory and some of the time, kicked to port going astern. Other times it kicked to stbd, and once or twice it even went straight backwards.

 

[Talulah]

Hi Very quickly,

Prop kick : in reverse stern goes to stbd in forward stern continues to go to Stbd? is that right ? Forget the rudder on this question keep it simple.

cheers James

Not right. Think of boat rotation rather forward/backwards.
In our case boat always wants to turn clockwise.
So in forward bow goes to starboard and stern to port.
In reverse stern goes to port and bow to starboard.
By using this we can turn on the spot but only in a clockwise direction.

 

[ChrisE]

Erm, I bit lost here. In reverse, if kicking to starboard this is a prop wash effect, independant of the rudder position. When you go forward the prop wash then goes over the rudder and the stern will go in the direction you choose because of the position of the rudder.

I guess if the boat didn't have a rudder then your question might make sense but then the boat wouldn't go too far.

Or am I missing something ???

 

[snowleopard]

That would make sense with a variable pitch prop but there aren't many of those about these days.

 

[Talulah]

Erm, I bit lost here. In reverse, if kicking to starboard this is a prop wash effect, independant of the rudder position. When you go forward the prop wash then goes over the rudder and the stern will go in the direction you choose because of the position of the rudder.

I guess if the boat didn't have a rudder then your question might make sense but then the boat wouldn't go too far.

Or am I missing something ???

In our case it is possible to leave the rudder centred and pretty well turn the boat on the spot using forward and reverse. It's more about inertia and getting a boat moving forward whilst your prop is pushing water out sideways as well as backwards/forwards.

 

[Twister_Ken]

Hi Very quickly,

Prop kick : in reverse stern goes to stbd in forward stern continues to go to Stbd? is that right ? Forget the rudder on this question keep it simple.

cheers James

Keeping it simple, ignore the rudder and think of it not as a prop but as paddle wheel, like on an old paddle steamer. In reverse the paddle wheel will go one way, and propel you (or your stern) in that direction. Change into ahead, and the paddle wheel changes direction and moves your stern the other way.

 

[Ubergeekian]

On Jumblie (26', long keel) forward causes the stern to swing slightly to starboard and astern causes the stern to swing hard to port. Oh the fun I had before working out always to go port side to in Crinan Canal locks.

 

[Jamesuk]

Your missing something Talulah!! )

I spoke to a guy on board the yacht I am on and he said the boat kicks to STBD but because it such a heavy yacht and the prop is a bit special he says you have to be careful because in forward the stern again wants to go to STBD.

I always was of the belief - If a left handed prop kicks the stern to STBD then in Forward it would kick to port? If this is not correct I need to hunt down the Instructor who told me.

Cheers

 

[Jamesuk]

In reverse the paddle wheel will go one way, and propel you (or your stern) in that direction. Change into ahead, and the paddle wheel changes direction and moves your stern the other way.

Thanks for clearing that up for me I am on board a 77 ft modern Classic that apparantly walks to Stbd in FWD & Reverse. Humm I thought, but just so I have the Principle re-learned. I will be happy to sit there nodding away when he says look its kicking to STBD referring to the prop kick - Must be something else affecting the reason it kicks to STBD in Forward - I have not seen the underside of the keel yet but will know more when I do Cheers Ken.

 

[Talulah]

Your missing something Talulah!! )

I spoke to a guy on board the yacht I am on and he said the boat kicks to STBD but because it such a heavy yacht and the prop is a bit special he says you have to be careful because in forward the stern again wants to go to STBD.

I always was of the belief - If a left handed prop kicks the stern to STBD then in Forward it would kick to port? If this is not correct I need to hunt down the Instructor who told me.

Cheers

I agree with your belief. However, as you are now on something special you may have to look in the engine bay. See if the prop comes out of the stern off centre. If it does that will explain the stbd/stbd syndrome.
Off centre props are quite common on classic boats.

 

[dt4134]

I always was of the belief - If a left handed prop kicks the stern to STBD then in Forward it would kick to port? If this is not correct I need to hunt down the Instructor who told me.

That's the basic theory, maybe you've just found one of the exceptions that prove the rule.

The other thing to consider is what the wind was doing on the bow at the time. Do you get different results depending upon where the wind is?

 

[Clyde_Wanderer]

When doing the DS practical I was asked to bring her along side in quite a tight space, I first asked which way the prop pushed the stern in reverse, then I made a perfect landing.
My stern swings to port (RH prop) when in reverse which is why I always come along side on the port side if possible.
While making way forward under power if I let go of the tiller she always arcs off to sb defying the theory that the stern should swing to sb.
Using this knowledge I can also turn a tight circle to sb but do need to use the helm too.

 

[JayBee]

Keeping it simple, ignore the rudder and think of it not as a prop but as paddle wheel, like on an old paddle steamer. In reverse the paddle wheel will go one way, and propel you (or your stern) in that direction. Change into ahead, and the paddle wheel changes direction and moves your stern the other way.

Twister Ken has it right, except in the case of a variable pitch prop which always rotates in the same direction.

There is an unbelievable amount of confusion surrounding prop "kick" or "walk", or as it is more grandly known in big ships, "transverse thrust".

In the YM Christmas quiz they got this one wrong. In the answers to the same quiz they stated that a yacht under sail OR power in fog should sound one long and two short blasts.

Don't believe everything the experts tell you.

I should say that the way individual yachts respond depends on hull form, prop location and other factors which may override or amplify the side thrust effects of prop rotation.

 

[Magnum]

Isn't it "prop walk"?