Ackerman angle

[Mark Hamill]

Ihave a Tangaroa 4 and want to add the ackerman angle feature on the rudders--could somebody give me the formula or a place to look?? Thanks, MarkH

[andy solywoda]

     The problem is that the turning radius dictates where the rudders should be, and in my case, it's such a large radius that large rudder angles are detrimental, they act as brakes if you go too far.  If you have Ackermann built into your rudders, the rudder on the inside of the turn will be at a greater angle and stall before the outboard rudder will.  This acts as a brake and the boat will actually turn faster as a result.  It is not efficient, though.

 

     One thing I did, that seemed to make sense, is to articulate the outboard engine (I have only one) to the tiller, so that turning also turns the engine.  It was not that big of a project to run a couple of lines and mount a few blocks.  The end result was not what I expected.  These boats want to run straight ahead, whether in forward or reverse (run straight astern).  The way I had been coping with this was to give the engine a burst, and the boat leans back as it jumps forward, and the rudder is hard over.  The engine is given only that burst and the boat gets maximum turning from the immersed rudder.  The boat glides along a bit while turning, then begins to settle into its prefered straingt line, then give it another burst.  This seems to work well to get the boat around in a tight area.

 

     My brother, who is a ship's master and harbor pilot, says to get steerage on a single screw craft in reverse, first rudder amidships, then build up some way, then carefully add rudder but don't stall it.  In my case we generally back down in a straight line, and any turning has to be done with the bursting forward technique.

 

     I will be removing my articulated engine rig from the tiller.  A dual engine arrangement makes a lot of sense.  You have redundancy and you have more control when you need it most.