Meindert Sprang wrote:
"Glenn Ashmore" wrote in message
news:ufQDb.5545$JD6.4631@lakeread04...

At this point I am kind of lost myself. Steering rams are rated for
operating more or less perpindicular to a tiller arm off the pivot
point. Alternately they are mounted off the transom at an angle as with
an outdrive.

What I think Garry is talking about is mounting the rams off the stern
parallel to the 7.5 sq.ft. rudder to brackets extending about 8" off
either side of the rudder. To me that seems to be a very odd
configuration that can't be calculated using the normal vendor supplied
formulas.


Say you have a bracket extending 8" off either side, and this extension is
mounted, say 8" off from the pivot point of the rudder. Then the mounting
point of the ram om this bracket is at the same point as if you would have
two tillers of 11.3" (pythagoras), each at an angle of 45 degrees from the
rudder. If you mount the each ram perpendicular to this 'virtual' tiller,
wouldn't that create the same setup as one tiller and two rams parallel to
the 'transom' (which he doesn't have)?

Meindert



That makes sense but he wants to mount the rams parallel to the rudder
which, if the setup is roughly 200mm square will set them at about 45º
to the "virtual tiller" in the center position. That arangement will
reduce the effective ram force by about 1/3. To complicate matters, the
Vetus MTC72 is 487mm long in the center position so the ram pivot has to
be mounted 287mm forward of the pintle. The geometry becomes a trapezoid
rather than a parallelogram and puts the action out of balance. A quick
Autocad sketch indicates 99 mm out and 140 mm in. He would have to use
two rams or the rudder would turn one way faster than the other.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com