propeller theory question..

[1950]

why does my sailboat go to starboard in reverse gear .It is a Volvo sterndrive and right hand rotating propeller. What is the theory on that? I know it has to do with pitch, but how exactelly?

 

[lenny2113]

Re: propeller theory question..

When you say it goes to starboard, do you mean the transom pulls to starboard? If that is the case, have you ever noticed a slight pull to port while shifting into forward?<br />I think you're talking about an isssue called "tourque steering". This issue does not occur on counter rotating twin engine boats.<br />I hope it answers your concern.<br />Happy boating,<br />Lenny

 

[Boatist]

Re: propeller theory question..

Alex<br />I really do not understand that. With a power boat with a right hand pitch prop the stern will kick to starboard in foward and to port in reverse. A real good book on this was single screw boat handleing. Most of the side kick will be with the boat stopped when you first put it in gear or when you reverse directions. The cause is water pushed off the top of the prop in foward with a right hand prop will hit the boat and outdrive. When it hits the outdrive two things happen the water pushes the outdrive to starboard and also the water is deflected back to port. Both these things tend to move the stern to starboard when you put a right hand prop in foward. Now off the bottom of the prop the water pushes to port but since nothing to hit water continues to port which also makes stern go to starboard.<br /><br />The effect can be used to your advantage to turn in a very whort distance. The effect is greatest when dead in the water and apply power or when reverse dirrections. As the boat speed pick up the effect gets less. <br /><br />Now your boat goes the other way. I will be the first to admit I know very little about sailboats. Learn a little in three coast guard classed I took and one power squadron class and some watching the America's Cup races but that is it. All that I can think of is if water is comming off the bottom of the prop and hitting the rutter or if the engine is off center. If you figure it out would love to learn why different than a power boat. Are you sure it is a right hand pitch?

 

[1950]

Re: propeller theory question..

Many thank for your helpfull reply. Alex