T&T: Articulating Flap Rudders (Was Following Seas)

[Dave Cooper]

Ron wrote: ......He talked about the fast acting autopilot and said it is
achieved by using a pump similar to an automobile power steering pump
connected to the engine.>

Autopilot pumps tend to be undersized by the manufacturers...marketing
influence and perceived need to sell at a low price are the main reasons,
IMHO.

Next time you are out in your car take the steering wheel while in park and
turn it slowly....no problem if you have power steering. Now try to turn it
fast and it isn't as easy. Try it when your on ice and you really notice it
trying to turn the wheel back and forth. This is called "pump catch" and is
caused by having a pump to small. Same thing happens to the rudder on your
boat with to small a pump. The autopilot can be calling for more rudder but
the pump can't supply the fluid. By the time it has the boat needs opposite
rudder.

Very few boats that I have ever delivered or run have pumps big enough to
steer the boat under anything less than ideal conditions. A hard over to
hard over time of 5 seconds or better is what is really required. Many
"manufacturers or sales agents" spec 10, 12 or even 15 seconds as being OK!

Some autopilots can handle a bigger pump without a problem as long as the
drive circuits are capable of the current required. Other might need a relay
box to upgrade. The issue then becomes is the software up to it and can it
detect the heading change quickly enough and apply the needed rudder before
counter correction is required.  A big rudder helps this as do large
steering cylinders and robust mountings.

A square stern boat is tough to stop wandering about in a following sea but
a bigger rudder will help.

I had looked at these articulating rudders some time in the past and would
put one on Swan Song if the rudder we have ever failed. Our configuration is
such that it would be an easy conversion. Our current rudder is 3 1/2 ft
deep by 2 1/2 long so we don't have too much issue with turning but I expect
that the Deflecter Marine rudder would really tighten our turning circle
without backing and filling. Being able to make a short radius turn both to
Port and Stbd would be a real help sometimes in tight spots.

As always YMMV....

Dave & Nancy
Swan Song
Roughwater 58