And the real numbers are:
size of drop bracket (2")
size of pedestal (2.5") -- still low enuf
size of pushrod extension (4 inches)
distance on tiller from the plane of the pintles to the rod
attachment pin (16.75")
location on the coaming of the pedestal (note that this is
determined by the preceding measurement since the
autopilot must be perpendicular to the tiller in
the neutral position): centered on coaming athwartships,
centerline 13" forward of the rolled down edge of
the deck molding, which equates to 1 3/8"
aft of rearmost point of cockpit rail
Note also that the mounting pin to bracket connection may be adjusted
through a vertical range of approx 3/4" to fine tune the leveling the
autopilot body.
The "crucial" dimension first mentioned is the 16.75" immediately above.
It directly determines the mechanical advantage and the range and speed
of corrective actions available to the autopilot. This distance, as
opposed to the recommended 18", gives the autopilot gretaer speed of
tiller movement and greater total tiller deflection at the expense of
less force available to move the tiller. With a boat as small as a P19,
full force is not needed and (because of the relative "twitchines" of
small vs large boats) faster speed of corection is very useful. Besides,
if one uses the recommended distance, the cockpit rail interferes with
the pedestal mount. :-)
I believe you should use a slightly shortened lever arm (p'haps 17")
rather than the nominal 18" even if you do not have a cockpit rail
conflict. It has worked very well for me, and I sense that I would not
always be happy with a slower rate of tiller correction.
BTW, I believe there is some rule about naming your autopilot. [For
example, I think the Pardeys once named one "Helmer." Cute, eh?]
Something about cutesy, anthropomorphic names apparently keeps the
gremlins away. Not being one prone to taking unecessary chances, mine are
named: Minder (full name Ursa Minder of course) for the ST1000 and
Dumbhead for the ST800 (cause it can't talk to the GPS).
Regards,
Bill Combs
WWP 19 #439 (August 1987)
"Ursa Minor"
Fort Walton Beach FL
ttursine@gnt.net