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Cruising America's Great Loop and other inland routes
View all threadsRe: GL: Autopilots and Bridges
Hi Ray,
My autopilot has two operating modes: "heading hold" and "route follow" are the terms used in my unit's user guide. I use both, but for bridges and long canals and such, am usually in "route follow" mode. I have a Garmin GHP10 autopilot, and have never seen the Crazy Ivan behavior you describe. I'm not certain, but I wonder if the course computer uses XTD in "route follow" mode rather than the course heading for the route segment? That seems a reasonable conclusion based on the way my unit behaves. That is, if the unit is following a route, it holds to a track within a few feet in calm water, and to within a few yards in 4 foot seas on the Chesapeake. But in "heading hold" mode, it is subject to the vicissitudes of set and drift, and has no ground reference to calculate XTD. Of course, XTD also relies on the accuracy of the GPS fix. If I go under a bridge and the GPS looses signal, the autopilot drops into heading hold (dead reckoning) mode; it does not disengage. It beeps to tell the helmsman it changed mode. That doesn't seem to happen often at all.
If the route I'm running doesn't set me up to be directly mid-span, or if there are other boats around, I do disengage the route, but I know I have been under bridges with the autopilot in both modes. I was really careful to disengage the autopilot the first couple of years I had it, but the unit has proved itself completely reliable in operation over the years.
Jim
Peg and Jim Healy aboard Sanctuary, currently at Charlotte Harbor, Punta Gorda, FL
http://gilwellbear.wordpress.com http://gilwellbear.wordpress.com/
Monk 36 Hull #132
MMSI #367042570
AGLCA #3767
MTOA #3436
The crazy mouse was a function of the older windows PC operating system miss-identifying the gps input as that of a pointing device. Google "gps, crazy mouse" and you should find solutions.
You obviously should not be on autopilot through bridges because of the bridge structure induced fluxgate compass magnetic deviation and the potential of bridge structure obscuring other boat traffic that may be a collision risk. Fishermen, etc..
On the Ohio and other Rivers there are underwater remains of several old lock and dam structures that can cause the same autopilot deviation. The U S Army Corps charts show these underwater structure locations. These are deep so are not a navigational hazard but have sufficient metal/mass to effect the fluxgate. It is disconcerting to have the boat suddenly turn off heading preset but unless near another vessel not much of a hazard as at cruise speed of 7 knts a generally brief occurrence.
Personally, we never rely on the autopilot to follow a pre set route, but instead use it to maintain a heading. This relieves us from manually steering and the distraction it adds. More importantly, it helps me to maintain a much better 360 degree watch, cross reference other charting, plot course on paper if crossing the gulf and verify proper course against nav-aids(numbers, location) etc. I monitor the boat's position and manually adjust course heading for any cross track errors. Overall, using our autopilot in this manner keeps me actively engaged and in my opinion is a safety enhancement. YMMV.
Joe Pica
M/V Carolyn Ann GH N-37
http://carolynann-n37.blogspot.com/
MTOA#3813, AGLCA #5485
And yes, my mileage does vary a bit from Joe's because I unexpectedly found
myself fine with the route-following AP, at least the way I personally
employ it.
My history with APs extends back to 1986 when I bought CALYPSO in San Diego
where the boat came equipped with an old analog Benmar-Cetek AP which used a
floating-card compass with a 12-volt light bulb shining through slots to be
read by left and right light sensors. A couple of times the light bulb
burned out and away went the wheel all the way to the rudder stop. The AP's
binnacle was connected to the motor drive by a coaxial drive cable like
ancient automobile speedometers used to be and was unalterably mounted near
the generator such that the boat took a big turn whenever I started the
genny. Oh, and it also hated southwesterly courses - it steered a
pronounced sinusoidal track on these. It was untrustworthy near the power
lines running across my local bay and anywhere near a bridge. Nonetheless,
I used it all the time running around the bays here, once clear of my
bayou's channel. On long open ocean transits we did as Joe recommends
(well, there was actually no other alternative with this old dog!) and set
the AP to steer a course which seemed to keep it relatively near track. I
would just touch it left or right once we got over a quarter mile off route
to cause the boat to slowly reverse the drift over to a quarter mile on the
opposite side of the route before reversing the procedure. In the ICW I used
it on the longer tracks in much the same way, but constantly had to adjust
it to the detriment of other things I could be doing like looking around
outside the boat more.
Then last year (luckily for the next owner, before I finally got the urge to
switch boats) I copied my brother's GB42's installation and put a modern
digital SITEX SP70 AP into the boat interfaced to both my Garmin 4208
chartplotter and my Coastal Explorer laptop (I have a toggle switch to
change the input to the SITEX from one source to the other).
I know in the past I have mentioned with disdain the practice of running an
AP in route-follow mode while potentially ignoring what the boat is actually
doing, but in practice, I have found that I (note the word "I" because this
is just MY impression) like to challenge the AP to follow chartplotter
routes, and that even on a long day of transiting a complex route with many
turns I find myself intently watching it thread narrow buoyed channels.
When I find it nearing a side of a channel or just taking a heading I want
to alter, I adjust the route on the chartplotter. When I return on this
"proofed" route, I find the AP does a wonderful job of taking the boat just
where I want it with the two chartplotters beeping away at waypoints or
whenever the boat drifts off the narrowly set cross-track error alarm. I
have even adopted the practice of pulling the boat out from under its shed,
heading it fair down the narrow twisting channel to the bay and immediately
setting the AP to route-following mode just to watch the miracle unfold. I
run it in "slow boat" mode until I get to the bay a mile distant and then
switch to "fast boat" mode as I throttle up from 5 to a roaring 8.6 knots.
Instead of having to constantly mind the helm, I am now more free to watch
all around as well as keep track of other navigation instrumentation like
radar and sounder and AIS. No doubt about it, there is potential for abuse
of the route-following AP, and you cannot legislate its use to govern the
idiots who would run one in order to leave off prudent nautical practices
like an adequate lookout, but for ME in my boat, the route-following seems
to increase the safety margins.
Rich Gano
Calypso (GB-42)
Panama City, FL
https://sites.google.com/site/grandbanks42sale/
Personally, we never rely on the autopilot to follow a pre set route, but
instead use it to maintain a heading. This relieves us from manually
steering
and the distraction it adds. More importantly, it helps me to maintain a
much
better 360 degree watch, cross reference other charting, plot course on
paper if crossing the gulf and verify proper course against
nav-aids(numbers,
location) etc. I monitor the boat's position and manually adjust course
heading for any cross track errors. Overall, using our autopilot in this
manner
keeps me actively engaged and in my opinion is a safety enhancement.
YMMV.
On 05/31/2015 08:55 AM, joseph.pica@gmail.com wrote:
The crazy mouse was a function of the older windows PC operating system miss-identifying the gps input as that of a pointing device. Google "gps, crazy mouse" and you should find solutions.
With four separate NMEA-0183 inputs feeding into our PC via a USB port
(on four separate virtual serial ports), we had this problem in spades.
It's a bug in Windows, which detects certain NMEA-0183 character
sequences as a Microsoft Ballpoint Serial Mouse.
Microsoft released a utility to fix it, which you must run (once) on a
port-by-port basis to disable Ballboint detection on each COM port to
which you've connected an NMEA-0183 device (such as a GPS). It's called,
perhaps uncreatively, the COMDisable tool. Find it here:
https://support2.microsoft.com/default.aspx?scid=kb;en-us;819036
-Sean
m/y Vector
lying South Bimini, BS
http://OurOdyssey.BlogSpot.com
Hummm,
Rich, you've gone to the electronics dark side! I must team with Rudy to host your intervention and save your nauti(cal) soul.
Joe Pica
M/V Carolyn Ann GH N-37
http://carolynann-n37.blogspot.com/
MTOA#3813, AGLCA #5485
On May 31, 2015, at 10:22 AM, Rich Gano richgano@gmail.com wrote:
And yes, my mileage does vary a bit from Joe's because I unexpectedly found
myself fine with the route-following AP, at least the way I personally
employ it.
My history with APs extends back to 1986 when I bought CALYPSO in San Diego
where the boat came equipped with an old analog Benmar-Cetek AP which used a
floating-card compass with a 12-volt light bulb shining through slots to be
read by left and right light sensors. A couple of times the light bulb
burned out and away went the wheel all the way to the rudder stop. The AP's
binnacle was connected to the motor drive by a coaxial drive cable like
ancient automobile speedometers used to be and was unalterably mounted near
the generator such that the boat took a big turn whenever I started the
genny. Oh, and it also hated southwesterly courses - it steered a
pronounced sinusoidal track on these. It was untrustworthy near the power
lines running across my local bay and anywhere near a bridge. Nonetheless,
I used it all the time running around the bays here, once clear of my
bayou's channel. On long open ocean transits we did as Joe recommends
(well, there was actually no other alternative with this old dog!) and set
the AP to steer a course which seemed to keep it relatively near track. I
would just touch it left or right once we got over a quarter mile off route
to cause the boat to slowly reverse the drift over to a quarter mile on the
opposite side of the route before reversing the procedure. In the ICW I used
it on the longer tracks in much the same way, but constantly had to adjust
it to the detriment of other things I could be doing like looking around
outside the boat more.
Then last year (luckily for the next owner, before I finally got the urge to
switch boats) I copied my brother's GB42's installation and put a modern
digital SITEX SP70 AP into the boat interfaced to both my Garmin 4208
chartplotter and my Coastal Explorer laptop (I have a toggle switch to
change the input to the SITEX from one source to the other).
I know in the past I have mentioned with disdain the practice of running an
AP in route-follow mode while potentially ignoring what the boat is actually
doing, but in practice, I have found that I (note the word "I" because this
is just MY impression) like to challenge the AP to follow chartplotter
routes, and that even on a long day of transiting a complex route with many
turns I find myself intently watching it thread narrow buoyed channels.
When I find it nearing a side of a channel or just taking a heading I want
to alter, I adjust the route on the chartplotter. When I return on this
"proofed" route, I find the AP does a wonderful job of taking the boat just
where I want it with the two chartplotters beeping away at waypoints or
whenever the boat drifts off the narrowly set cross-track error alarm. I
have even adopted the practice of pulling the boat out from under its shed,
heading it fair down the narrow twisting channel to the bay and immediately
setting the AP to route-following mode just to watch the miracle unfold. I
run it in "slow boat" mode until I get to the bay a mile distant and then
switch to "fast boat" mode as I throttle up from 5 to a roaring 8.6 knots.
Instead of having to constantly mind the helm, I am now more free to watch
all around as well as keep track of other navigation instrumentation like
radar and sounder and AIS. No doubt about it, there is potential for abuse
of the route-following AP, and you cannot legislate its use to govern the
idiots who would run one in order to leave off prudent nautical practices
like an adequate lookout, but for ME in my boat, the route-following seems
to increase the safety margins.
Rich Gano
Calypso (GB-42)
Panama City, FL
https://sites.google.com/site/grandbanks42sale/
Personally, we never rely on the autopilot to follow a pre set route, but
instead use it to maintain a heading. This relieves us from manually
steering
and the distraction it adds. More importantly, it helps me to maintain a
much
better 360 degree watch, cross reference other charting, plot course on
paper if crossing the gulf and verify proper course against
nav-aids(numbers,
location) etc. I monitor the boat's position and manually adjust course
heading for any cross track errors. Overall, using our autopilot in this
manner
keeps me actively engaged and in my opinion is a safety enhancement.
YMMV.
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You know, Joe, I am afraid you are a little bit right! I never thought I'd
do that, but the fact is if a piece of electronics is supposed to do
something, I am danged well gonna make it demonstrate the capability.
Anyway, as soon as I sell this boat, I can go back to the "light" because I
a sure the next boat will not have the extensive equipment Calypso has;
however, NO kerosene nav lights for me - that's just too dark.....
Rich Gano
Calypso (GB-42)
Panama City, FL
https://sites.google.com/site/grandbanks42sale/
Hummm,
Rich, you've gone to the electronics dark side! I must team with Rudy to
host
your intervention and save your nauti(cal) soul.
Like Rich, I too am guilty of using the AP to to navigate routes. Until
retirement in two years I am time limited to cruising Kentucky & Barkley
lakes along with a annual trip to the Chattanooga area (my boat is
trailerable). Over the years I have established routes from marina to
marina (ones with restaurants!) and use them frequently. Because of my
shallow draft (about 20") many of these are out of channel and closer to
the shoreline where we can better enjoy viewing the habitats of those
poor folks that have made the mistake of thinking looking at the water
is better than being on the water. My cruise speed is usually between
5.5 and 6 knots and normally nothing too exciting happens at that pace
so I am comfortable sitting at the helm and letting the AP do the work.
But now it looks like I will need to be more aware of of objects I
fairly well ignored before as metal both fixed and afloat demand my
attention. I guess I will actually have to steer the boat using that
round thing in front of me I normally use as a foot rest.
On 5/31/2015 3:11 PM, Rich Gano wrote:
You know, Joe, I am afraid you are a little bit right! I never thought I'd
do that, but the fact is if a piece of electronics is supposed to do
something, I am danged well gonna make it demonstrate the capability.
Anyway, as soon as I sell this boat, I can go back to the "light" because I
a sure the next boat will not have the extensive equipment Calypso has;
however, NO kerosene nav lights for me - that's just too dark.....
Rich Gano
Calypso (GB-42)
Panama City, FL
https://sites.google.com/site/grandbanks42sale/
Hummm,
Rich, you've gone to the electronics dark side! I must team with Rudy to
host
your intervention and save your nauti(cal) soul.
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