I just posted this to the Morgan groups, addressing Charley Morgan,:
rbc/b has had some opinion on the subject points so I duplicate them
he

Hi, Charley,

Repairs are coming along on Flying Pig, which appear to promise full
restoration. We're already applying bottom paint, and are rounding
third on the rudder rebuild.

Meanwhile, one of the guys working with me in the rudder restoration
suggests using a "ducktail" on the rudder to improve the autopilot
stability (it hunts busily, now, and has since we have owned the
boat). I'm assuming that if that were efficient, today's high-priced
yachts would have them. To me it seems counterintuitive - even the
lowest-slowest airplanes don't have such a configuration to the rudder
or elevators, and anything which creates drag (as I assume a blunt
end, particularly one increased in size from the exit, to perhaps the
width of a foot into the chord from the aft, would do) isn't a good
thing, either.

Back to the repairs, despite the pounding and associated flexing
suffered in our grounding, we have found that the bulkheads have
largely remained in the exact same position, despite much delamination
of the vertical tabbing (nearly all of the hull-side tabbing has not
been disturbed) on the bulkheads from forward galley to aft head. I
have two questions:

Pete Brown (QC and service Manager(s) 1978-1984) has suggested using a
thin wedge to expand the gap between bulkhead and tab slightly,
flowing expoxy into the crack, removing the shims, then screwing
copiously (maybe on a 4" grid) to both pull it in and make a
mechanical as well as chemical bond. I'm thinking using boards to
spread the load, and jacks, to compress, would be both as effective
(mechanical aside), probably much faster, and would not leave a bunch
of screw heads out which would have to be dealt with in some fashion
later. Your thoughts?

Second, and related: on our return to Salt Creek, with only either a
staysail or a spinnaker, our two primary sails having been removed as
damaged, in one of our staysail periods, we were swinging through a
40-45* arc with the large waves and following seas. Much creaking
below the cockpit was noted. Going below, I discovered that even in
the largest, most severe, hull-bulkhead delamination areas (in the
ER), there was no movement, vibration or noise coming from those
joints. Instead, I could feel movement (slight, of course) and
vibration at the bulkhead-ceiling liner joint. Those were not tabbed,
originally, but also didn't move (or, at least, didn't creak). How
was that secured originally, and how would you suggest resecuring,
presuming that no motion would be better both from a peace of mind (no
noises) and security (less hull flexing) perspective?

Related, the tabbing delamination, even in the worst case, doesn't
extend beyond the area where it was being pounded. Thus, higher up on
the hull, the tabbing is still attached to the bulkhead - and thus the
bulkhead is in its original position there. From that I presume the
hull/bulkhead shape configuration is likely pretty much the same as
was before, with some potential for, particularly in light of the wood
rot seen elsewhere in the boat as we've exposed stuff, some beating-up/
compression of the bulkhead in the impact areas (at the hull-bulkhead
contact points), but only at that low point next to the hull. It's my
presumption that with new expoxy and compression to secure the
existing tabbing to the bulkhead, once cured, those bulkheads would be
functionally as the original. Do you concur?

Thanks for any wisdom - this is new territory for me...

L8R

Skip and Lydia

Morgan 461 #2 Disaster link: http://ipphotos.com/FlyingPig.asp
SV Flying Pig KI4MPC
See our galleries at www.justpickone.org/skip/gallery !
Follow us at http://groups.google.com/group/flyingpiglog and/or
http://groups.yahoo.com/group/TheFlyingPigLog

There is no such thing as a problem without a gift for you in its
hands.

You seek problems because you need their gifts.

"Skip Gundlach" wrote:
snip

Meanwhile, one of the guys working with me in the rudder restoration
suggests using a "ducktail" on the rudder to improve the autopilot
stability (it hunts busily, now, and has since we have owned the
boat). I'm assuming that if that were efficient, today's high-priced
yachts would have them. To me it seems counterintuitive - even the
lowest-slowest airplanes don't have such a configuration to the rudder
or elevators, and anything which creates drag (as I assume a blunt
end, particularly one increased in size from the exit, to perhaps the
width of a foot into the chord from the aft, would do) isn't a good
thing, either.


Focusing only on the autopilot issue presented, I would suggest that the
hunting issue is not likely related to rudder shape. The autopilot is just
a servocontrol loop, with PID configuration (Proportional, Integral, and
Derivative). Feedback comes from the fluxgate compass or wind direction
transducer. Your percieved hunting behavior is typical of servoloops
adjusted with too little forward, or proportional gain. They cannot react
fast enough to changing conditions, and are forever correcting for the
situation of a few seconds ago. Under certain circumstances, a servoloop
with too much forward gain can exhibit instability in a way that resembles
hunting, even though the mechanism is different.

Some servocontrollers also allow adjusment of the integral and derivative
parameters. The integral feature (sometimes called "reset") improves the
accuracy of response when conditions don't change much. This is often
automatic and not adjustable. The derivative adjusment stabilizes the
control loop, allowing more forward gain and hence quicker response by
introducing the rate-of-change of the feedback

The short version is; experiment with the adjustments available in the
autopilot and on its control panel, and note whether increasing/decreasing
each parameter improves the response of the system or not. If it makes
things worse, go the other way.

I know this is a little obtuse, but I hope it might lead you to another
possible cure for your control problem.

John Hart

--
-------------------- http://NewsReader.Com/ --------------------
Usenet Newsgroup Service $9.95/Month 30GB

The ducktail will probably cure the hunting problem but it's a crude
treatment of the symptom rather than the cause. It's a terrible thing to do
to a sailboat, you'll be dragging that thing 24 hours a day.

Does it hunt under sail or just under power?

See the other post for better solutions.

--
Roger Long

Thanks for any wisdom - this is new territory for me...

L8R

Skip and Lydia

Morgan 461 #2 Disaster link:http://ipphotos.com/FlyingPig.asp
SV Flying Pig KI4MPC
See our galleries atwww.justpickone.org/skip/gallery!
Follow us athttp://groups.google.com/group/flyingpiglogand/orhttp://groups.yahoo.com/group/TheFlyingPigLog

There is no such thing as a problem without a gift for you in its
hands.

You seek problems because you need their gifts.

Several things, the wedge and screw is a good idea but its going to
make work later, a fillet and strip would work to provide a chem and
phys bond.

second if she is seaking really bad and you are in the yards have her
tanks drained (yes everything drained) set her in the water and see
how she sits. I'd be willing to bet she will not sit fair and you will
need to adjust her perminant ballest. third, rudder size, shape, and
how it's fit to the boat might also need some looking into.

Ive built a couple big wood fishing boats that have cought a rock or
two and had them come back for repair.
most times it's not a big deal but i always check a boats set and
check her rudder and fittings if she is off.
most times ballest is a problem.

2MT

I doubt that the duck tail would help with the autopilot hunting and
it will make the boat slower. If the pilot is hydraulic I would check
the pilot's rudder angle sensor to make sure it is operating correctly
and is properly centered. Fiddling with the gain controls may help
and the manual should have some set-up procedures to follow. A
gyroscopic rate change sensor can be added to many autopilots these
days. They can reduce autopilot induced oscillation and also help
with radar targeting.

-- Tom.

In article om,
"Skip Gundlach" wrote:

Meanwhile, one of the guys working with me in the rudder restoration
suggests using a "ducktail" on the rudder to improve the autopilot
stability (it hunts busily, now, and has since we have owned the
boat).


Check how much play/flex is in the autopilot system. I found that a very
small amount of play translated into a whole lot of wandering. After
that, playing with the gain & damping settings was more consistent.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's NEW Pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

wrote in news:20070314163424.069
:

-------------------- http://NewsReader.Com/ --------------------
Usenet Newsgroup Service $9.95/Month 30GB



John, for less than $4 more, on a 3-month payment at a time, you can
download 24/7/365 with unlimited GB and 100 days retention at 99.9%
completeness on www.usenetserver.com, which is FAR greater than any other
news server I ever encountered.....works great!

I download about 15GB/day...(c;

Larry
--
How much price inflation is caused by illegal
aliens gobbling up goods and services, creating
shortages for the natives? I heard 40%!

inscribed in red ink for all to know:
"Skip Gundlach" wrote:

snip


Meanwhile, one of the guys working with me in the rudder restoration
suggests using a "ducktail" on the rudder to improve the autopilot
stability (it hunts busily, now, and has since we have owned the
boat). I'm assuming that if that were efficient, today's high-priced
yachts would have them. To me it seems counterintuitive - even the
lowest-slowest airplanes don't have such a configuration to the rudder
or elevators, and anything which creates drag (as I assume a blunt
end, particularly one increased in size from the exit, to perhaps the
width of a foot into the chord from the aft, would do) isn't a good
thing, either.



Focusing only on the autopilot issue presented, I would suggest that the
hunting issue is not likely related to rudder shape. The autopilot is just
a servocontrol loop, with PID configuration (Proportional, Integral, and
Derivative). Feedback comes from the fluxgate compass or wind direction
transducer. Your percieved hunting behavior is typical of servoloops
adjusted with too little forward, or proportional gain. They cannot react
fast enough to changing conditions, and are forever correcting for the
situation of a few seconds ago. Under certain circumstances, a servoloop
with too much forward gain can exhibit instability in a way that resembles
hunting, even though the mechanism is different.

Some servocontrollers also allow adjusment of the integral and derivative
parameters. The integral feature (sometimes called "reset") improves the
accuracy of response when conditions don't change much. This is often
automatic and not adjustable. The derivative adjusment stabilizes the
control loop, allowing more forward gain and hence quicker response by
introducing the rate-of-change of the feedback

The short version is; experiment with the adjustments available in the
autopilot and on its control panel, and note whether increasing/decreasing
each parameter improves the response of the system or not. If it makes
things worse, go the other way.

I know this is a little obtuse, but I hope it might lead you to another
possible cure for your control problem.

John Hart


Very well said, John.

Another cause of failing to settle at the setpoint is too much lag in
the system. So, too much gain, or too much lag, or both will give an
unstable system. Adding rudder area will have the effect of increasing
the gain. It is unlikely that this will improve the system.

Another big cause of hunting: deadband. If there is slop either
between the actuator and the rudder panel, or between the rudder sensor
and the rudder panel, this is a big no no.

In all, I'd remove any slop, and then follow John's excellent advice above.


bob
s/v Eolian
Seattle