Autopilots
Larry
jet-powered runabout that I added an autopilot to, but while it did work
at higher speeds, it failed miserably for trolling and fishing in
general. Last year I sold it and bought a center console Cobia, a 21'
with a 150 hp Yamaha outboard. I added a 15 hp (smallest I could get
without ordering) Suzuki outboard to use as a trolling motor. It is
tied, mechanically, to the larger Yamaha and sips fuel from the same
large tank. It works pretty well, and steers a straight course with no
hands on the wheel.
Still, I'd like to add an autopilot IF (and only if) it can operate at
trolling speeds (about 1 knot or 1.5 mph). ComNav makes a few units
which look like they'd work, but I'd like to hear that from someone
other than the manufacturer or salesman, preferably someone who owns
one. The boat is equipped with a Garmin 540 combination fishfinder/GPS
chartplotter which issues NMEA sentences.
--
Larry
rapp at lmr dot com
Edgar
"Larry" <inv...@invalid.com> wrote in message
news:Wp6dnQkPs6ACp47V...@giganews.com...
You need an autopilot where you can alter the amount of response to a given
course deviation.
At trolling speeds you need much more rudder angle to correct a deviation
than you would at higher speed.
However, if you are trolling rather than maintaining course to a destination
you ought to be able to accept a greater amount of yawing about the set
course anyway.
Gregory Hall
as to how to safely operate a boat blasting around the water becoming a big
nuisance and even larger menace to all concerned.
Take your autopilot, and overgrown Jetski for that matter, and shove it up
your ass!
--
Gregory Hall
"Larry" <inv...@invalid.com> wrote in message
news:Wp6dnQkPs6ACp47V...@giganews.com...
Bigfoote
Raymarine Sportpilot. It is a wheel mount unit and may not fit but I have
had one on an old Slickcraft for 13 years and it is still doing the job
trolling for salmon on lake Michigan about 200 hours a year. Did have to
replace the electronic compass module once but at a very reasonable price.
Even accepts waypoint data from my old Garmin GPS/Plotter. Biggest problem
if it fits the wheel is where to mount the compass at lest 3 feet from any
large metal mass (i.e. engine). Ideal is low and to the rear to minimize
roll and pitch effects on compass but not easy in a small boat.
Larry
news:Wp6dnQkPs6ACp47V...@giganews.com:
> Still, I'd like to add an autopilot IF (and only if) it can operate at
> trolling speeds (about 1 knot or 1.5 mph). ComNav makes a few units
> which look like they'd work, but I'd like to hear that from someone
> other than the manufacturer or salesman, preferably someone who owns
> one. The boat is equipped with a Garmin 540 combination
fishfinder/GPS
> chartplotter which issues NMEA sentences.
> --
>
>
If this is the only electronics in your system, I think your GPS, not
your autopilot, is your problem.
GPS only CALCULATES your direction of travel. The GPS signal only
allows its electronics to figure out your position every second. That
display that says your boat is pointed 085 degrees is only a guesstimate
of the GPS electronics because it looked at the last few seconds of
where you've been and where you are....a little 085 from where you were
a second ago.
At low speed, a GPS is damned near USELESS as a compass input for the
autopilot to follow and shouldn't be used. Too many sailboats try to
autopilot in poor wind conditions with the same wandering results
because the GPS' idea of direction of travel over ground is wandering,
too.
What you need for the autopilot is a COMPASS SENSOR. Some are also
called Fluxgate Sensors because they use a solid state magnetic field
sensor, not a real compass. This device will tell your autopilot which
direction the boat is pointed in EVEN AT ZERO MPH, always telling the
autopilot to follow a MAGNETIC COURSE from its information, not a
wandering GPS course from lack of information.
Under 3-4 knots, the GPS is useless as a directional compass sense
device because of its calculated guess. Use a real Compass Sensor.
Most good autopilots have at least a Fluxgate magnetic sensor as part of
their package. Unfortunately, most installations pay way too little
attention to the fluxgate's mounting position way too close to magnetic
objects mounted "out of sight" in lockers full of magnetic junk and
CURRENT CARRYING DC POWER WIRING, which always radiates a strong
magnetic field, which drags off the fluxgate or compass sensor's
calibration in some odd fashion.
The magnetic sensor, whether fluxgate or real compass, needs to be near
the CG of the boat's axii, all 3 of them. It needs to be away from all
power wiring carrying any kind of appreciable DC CURRENT and away from
ALL MAGNETIC OBJECTS, anything made of steel or brass. That's a pretty
tall order in a small boat, but very necessary to maintain compass
course accuracy at very low speeds.
On a rolling pitching boat, the solid state compass sensors are much
better than the mechanical ones, which get moving around from the motion
and give false readings. It's also best to get one that's "self
compensating", one that you simply turn in a circle a few times, slowly,
and it makes its own compensation chart which it stores to make more
accurate fixes.
http://www.maretron.com/products/ssc200.php
just as an example.....
n...@here.com
<greg...@home.fake> wrote:
>Just what the world needs - another autopilot jetboat jerk who hasn't a clue
>as to how to safely operate a boat blasting around the water becoming a big
>nuisance and even larger menace to all concerned.
>
>Take your autopilot, and overgrown Jetski for that matter, and shove it up
>your ass!
C'mon Gregory, Why don't you tell him how you REALLY feel?
--
Calling an Illegal Alien an "Undocumented Worker" is like calling a
Crack Dealer an "Unlicensed Pharmacist"
Richard Casady
>away from
>ALL MAGNETIC OBJECTS, anything made of steel or brass.
Since when is brass magnetic?
Casady
Larry
> You need an autopilot where you can alter the amount of response to a given
> course deviation.
> At trolling speeds you need much more rudder angle to correct a deviation
> than you would at higher speed.
> However, if you are trolling rather than maintaining course to a destination
> you ought to be able to accept a greater amount of yawing about the set
> course anyway.
Frankly, I knew that - can you suggest one? Thanks.
Larry
> Just what the world needs - another autopilot jetboat jerk who hasn't a clue
> as to how to safely operate a boat blasting around the water becoming a big
> nuisance and even larger menace to all concerned.
>
> Take your autopilot, and overgrown Jetski for that matter, and shove it up
> your ass!
>
> --
> Gregory Hall
Gregory,
Why don't you come tell me that personally. I live at 1 Indian Trail,
Colebrook, New Hampshire and we can talk about this face to face.
Lets see if your courage extends that far.
Larry
the result of incorrect response. It would overcompensate at low speeds
because of the amount of time it took between issuing a command (it
turned the wheel which directed the jet) and the boat moving. There was
no rudder feedback nor could it have been added easily. While there
were multiple levels of sensitivity which could be set, none of them
worked at low speed with the result that the craft overcompensated. I
think the unit was a Raymarine Sportpilot.
Normally, one mounts the fluxgate compass as close to the bow as
possible, but (naturally) away from anything ferrous like an anchor.
The only purpose of a GPS might be to plot a long course, but, as I
said, the main reason for adding an autopilot would be for trolling
single-handed.
I've been boating for over 50 years, and have sailed all around the
Carribean, so I'm not a novice. I've owned boats from 14 to 38 ft.
and am an EE so don't be afraid to get technical.
Capt. JG
You're joking. He and his companions are cowards and liar. Maybe you're just
being mean, since I'm sure that it's obvious who and what they are. Shame on
you Larry!
--
"j" ganz @@
www.sailnow.com
mister b
<snip>
LOL
what a putz!
would you please just get over yourself
Edgar
Sorry, Larry-I did hesitate a bit before posting that in view of your
electrical
expertise.
Cannot suggest a make of pilot that would assist you as my last one was a
wind vane.
Now however I have got a Simrad wheel pilot which was very good when I used
it last season to steer compass courses.
However I am now on the point of hooking it into the output from the chart
plotter so it can steer me to a waypoint but have just seen your later post
about the uselessness of GPS based pilots at low speeds and since I have a
sailboat it looks as if this will not help me in light winds, so maybe I
will leave things as they are. It has a good fluxgate compass which you
calibrate by steering in slow circles a couple of times and, best of all,.no
belts or control lines across the cockpit. You can control the sensitivity
to yawing to minimise battery drain.
Larry
news:487b7d3d....@news.east.earthlink.net:
> Since when is brass magnetic?
>
> Casady
>
>
http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_6.html
Brian Whatcott
>richar...@earthlink.net (Richard Casady) wrote in
>news:487b7d3d....@news.east.earthlink.net:
>
>> Since when is brass magnetic?
>>
>> Casady
*****
>http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_6.html
This helpful table compilation from NPL confirms that brass is
essentially non magnetic, as it happens.
Brian W
Roger Long
> Sorry, Larry-I did hesitate a bit before posting that in view of your
> electrical expertise.
I think this is a different "Larry" than our regular poster from Charleston
SC.
Larry (#2), it would help avoid confusion if you added an initial or
something to you posting name.
--
Roger Long
Richard Casady
I tried to follow the link and got the runaround. Thank you for
getting there and giving us a report. Maybe there is somthing wrong
with the SSSW [SuckShitSoftWare].
Casady
Larry
rec.boats.electronics. I am not him! Hows's this?
I know I'm going to forget. I've been using this name since 1985 - yes,
I'm older than dirt! I'm from NH, btw, originally from Long Island, New
York.
--
Larry R
Larry
You're right, Cap'n. Normally, I just ignore children going through
puberty, but this morning he just pushed the right buttons and I felt he
needed to be taught a physical lesson if he had the stomach for it. As
you surmised, he didn't. I'll go back to ignoring!
--
Larry R
Larry
a background in electronics.
The autopilot I used had no sensor for speed. Does any? It would seem
to me that there needs to be one because response to the wheel is
proportional to your speed underway.
Larry
Wow, that is really interesting. I think that is what I used on the
Utopia. Perhaps it was because it was a jet boat and very slow to
respond at trolling speeds. Interesting. Btw, the reason for getting a
jet boat was to eliminate the propeller. It could navigate in very
shallow water (so long as there were no weeds and not a lot of mud) but
it made an awful boat for fishing.
Did you have any kind of rudder sensor? I realize you probably have an
outboard, but trolling is really slow - the fact that it works is really
significant to me. Also, you put the compass in the rear - I tried it
up by the bow and amidships, I could not have put it in the stern as
that's where the engine was.
--
Larry R
Richard Casady
That website has nothing to say. It lists magnetism in a table of
contents but when you click on it, it goes back to a previous table of
contents. There seems to be nothing there.
Casady
cavelamb himself
No, I think they just use the old double-angle-off rule of thumb.
--
(remove the X to email)
Now just why the HELL do I have to press 1 for English?
John Wayne
cavelamb himself
It showed magnetic susceptibility of brass as 1, steel as 150.
Less than 1% as magnetic as steel?
Richard
Brian Whatcott
<cave...@Xearthlink.net> wrote:
>>>
>>>http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_6.html
/snip/
>It showed magnetic susceptibility of brass as 1, steel as 150.
>
>Less than 1% as magnetic as steel?
>
>
>Richard
Well, THAT was an interesting reading of the data!
How would you respond if I said both copper and zinc were less
magnetic in terms of susceptibility than for example the transparent
plastics?
Ah, yes but there might be minor iron inclusions in a brass
casting? Yeppers!
Or in a bronze casting.
Or a cxopper casting.
Or in an aluminum casting....
:-)
Regards
Brian W
Roger Long
circuits. I've never heard of a speed input but do know that "rate based"
autopilots are considered better than "heading based" units on aircraft. I
would imagine from the name that they adjust their respons according to the
speed of the heading change which should produce similar results to a speed
input.
You might be interested in this bit of electronics tinkering I did last
fall:
http://home.maine.rr.com/rlma/ST1000mods.htm
--
Roger Long
Roger Long
>>
> Sorry. There is another Larry who posts fairly regularly in
> rec.boats.electronics. I am not him! Hows's this?
>
Great. Now if you would just stick the R into your name so it shows up in
the header we'll know who we're reading before getting to the bottom
> I know I'm going to forget. I've been using this name since 1985 - yes,
> I'm older than dirt! I'm from NH, btw, originally from Long Island, New
> York.
LOL Older than dirt? I've been using my name since 1950. I must be older
than the hills.
--
Roger Long
Wayne.B
<str...@maine.rr.com> wrote:
>I
>would imagine from the name that they adjust their response according to the
>speed of the heading change which should produce similar results to a speed
>input.
Yes, no speed input, just rate of change.
Goofball_star_dot_etal
Give it a rudder so it can become the happy little second-order system
it was born to be.
Larry
Very clever, Roger. My unit, I believe it was a Sportpilot, used a
motor to drive the wheel. It must have been fitted with limit switches
as the motor didn't seem to overheat, but the rate of response was, as I
said, too slow when trolling.
I thought about going into the controller and adjusting it, probably
through software, but it probably use a surface mount processor and it
was just too much work. I called Raymarine or whoever made the thing
and they weren't interested in helping. As I said earlier, I sold the
boat and got something a lot better (at least in my judgment).
I could live without an autopilot now (and I may), especially since this
boat tracks well, but I can never leave well enough alone...
Larry
Then they cannot differentiate between a massive craft which isn't all
that maneuverable to start with, and something handier that is just
moving slowly. Oh well...
--
Larry R
Larry
> Give it a rudder so it can become the happy little second-order system
> it was born to be.
Well, you can't add a rudder to a jet boat. I could have connected the
sensor to the tube used to steer the craft, but since the the entire
coupling was underwater, it would have been quite a production and I
still don't know that it would have worked correctly.
--
Larry R
Goofball_star_dot_etal
>Goofball_star_dot_etal wrote:
>
>> Give it a rudder so it can become the happy little second-order system
>> it was born to be.
>
>Well, you can't add a rudder to a jet boat.
Try to remember that you sold that boat last year and want to control
a boat with a 15 hp Yamaha outboard at "trolling speeds (about 1 knot
or 1.5 mph)"!! with an autopilot which expects a certain (range of)
yaw rate proportional to the control input, not a pig dominated by
small forces and relatively large moment of inertia.
Larry
Yes, I understand, but how would you add a rudder to an outboard? Or do
you mean use the steering mechanism as a rudder? (actually, the big
engine is a Yamaha, the 15 hp is a Suzuki)
I would assume that any autopilot would net out yaw, but I don't know
and don't want to pay all outdoors to find out. Are you saying it's a
large factor?
I fish northern New England lakes - yaw isn't a big factor. Also, I am
not a commercial fisherman - I fish for fun. If the weather goes south,
I generally head in.
Goofball_star_dot_etal
>Goofball_star_dot_etal wrote:
>> On Tue, 29 Apr 2008 10:53:50 -0400, Larry <inv...@invalid.com> wrote:
>>
>>> Goofball_star_dot_etal wrote:
>>>
>>>> Give it a rudder so it can become the happy little second-order system
>>>> it was born to be.
>>> Well, you can't add a rudder to a jet boat.
>>
>> Try to remember that you sold that boat last year and want to control
>> a boat with a 15 hp Yamaha outboard at "trolling speeds (about 1 knot
>> or 1.5 mph)"!! with an autopilot which expects a certain (range of)
>> yaw rate proportional to the control input, not a pig dominated by
>> small forces and relatively large moment of inertia.
>
>Yes, I understand, but how would you add a rudder to an outboard? Or do
>you mean use the steering mechanism as a rudder? (actually, the big
>engine is a Yamaha, the 15 hp is a Suzuki)
I can see two options.
The first is to attach a foil to the 'small' outboard
eg. http://www.freepatentsonline.com/3991700.html
This would be steered through your existing arrangement with or
without an autopilot. I assume that this small outboard can be raised
when not in use, removing the rudder from the water, but if it is
robust enough could be left in the water at speed.. The disadvantage
of this scheme is the large load on the autopilot of having to control
both motors though the steering mechanism.
The second option would be an auxiliary rudder similar to a typical
sailing dinghy rudder with a lifting blade to be used only when
trolling. This could be large enough to do the required job but quite
light and weak. If the rudder/boat response is good enough the
cheapest autopilot could be attached and used just for low speeds,
with a remote control if required. This arrangement would be a
nuisance and likely be damaged at speed so needs to be retracted then.
>
>I would assume that any autopilot would net out yaw, but I don't know
>and don't want to pay all outdoors to find out. Are you saying it's a
>large factor?
No, I mean that most boats at normal speed turn more or less like a
car, with a turning circle radius that reduces with helm movement. The
assumption is that autopilots are designed for typical boats behaving
in this way. Observing autopilot behaviour, they seem to move the helm
in proportion to the error, although there is also a dead-band, some
integration of error and some damping involved. It seems they would
assume a rate of turn proportional to the error signal and actuator
movement whereas a jet or outboard at low speed produces a very small
transverse thrust in response to the angular error signal, causing
angular acceleration that increases the rate of turn with time.
It seems a better plan to try to fix the boat's low speed steering
than to expect a control system to cope with this. You need the gain
of the factors that relate angular heading error to the boat's rate of
turn (yaw rate) to be more or less constant and within the bounds of
the autopilot design, then all should be well. You don't want the
error integating up because nothing has happened yet!
>
>I fish northern New England lakes - yaw isn't a big factor. Also, I am
>not a commercial fisherman - I fish for fun. If the weather goes south,
>I generally head in.
I don't bother to go out sailing unless there is some decent wind and
waves..
Jere Lull
> The autopilot I used had no sensor for speed. Does any? It would seem
> to me that there needs to be one because response to the wheel is
> proportional to your speed underway.
Haven't been paying attention to this thread, but my tiller AP will
"read" some NMEA speed sentence and the swing can be adjusted.
--
Jere Lull
Xan-à-Deux -- Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/
Larry
> Raymarine Sportpilot. It is a wheel mount unit and may not fit but I have
> had one on an old Slickcraft for 13 years and it is still doing the job
> trolling for salmon on lake Michigan about 200 hours a year. Did have to
> replace the electronic compass module once but at a very reasonable price.
> Even accepts waypoint data from my old Garmin GPS/Plotter. Biggest problem
> if it fits the wheel is where to mount the compass at lest 3 feet from any
> large metal mass (i.e. engine). Ideal is low and to the rear to minimize
> roll and pitch effects on compass but not easy in a small boat.
Would you please describe your Slickcraft? I think I had a Raymarine
Sportpilot, it may have changed, but perhaps it can be made to work.
Thanks!
Larry
> I can see two options.
> The first is to attach a foil to the 'small' outboard
> eg. http://www.freepatentsonline.com/3991700.html
> This would be steered through your existing arrangement with or
> without an autopilot. I assume that this small outboard can be raised
> when not in use, removing the rudder from the water, but if it is
> robust enough could be left in the water at speed.. The disadvantage
> of this scheme is the large load on the autopilot of having to control
> both motors though the steering mechanism.
The steering is hydraulic. I haven't done any testing, but it doesn't
seem like much of a load. I can disconnect the arm which connects the
two motors - the force required to turn the wheel doesn't change very
much.
In the case above, if I read the link correctly, the "rudder" is nothing
but a flat plate behind the propellor. And, yes, the motor can be
raised. I don't understand how the "rudder" adds anything as steering
is still accomplished by moving the motor. The only thing added here is
direct feedback from motor pointing (via steering). That must be
important for the system to function as it was suggested by the
Sportpilot (if that's what it was). I don't see what it adds as all it
would do is provide an indication of potential slack or "play" in
steerage.
My understanding of yaw differs from yours. You're probably correct.
My understanding of yaw is coupled with pitch and nets out but does
provide considerable movement. I _thought_ a fluxgate compass enclosed
a gimballed affair with sufficient time constants to do that (net out
pitch and yaw).
With the Sportpilot, it seemed as though if the time constant of the
response curve could have been lengthened, the system would have worked.
What I perhaps should have done was to measure the amount of time the
boat took to go from one compass point to another (say 45 degrees apart)
and compare that with what the current boat does, both at the same
speed. Actually, that sounds like a plan and I can still do that as I
will be seeing the owner of the Utopia in early July and will have my
boat with me. At trolling speeds, if the boat turns substantially
faster, then the old system might work - without a rudder!
Your explanation makes sense to me, but unless the control electronics
are very "smart" that gain has to be variable and it wasn't. Well,
there were, as I recall, three steps, but the longest response time
wasn't long enough and horrible overcorrection occurred at low speeds.
In fact, the longest response was what I had to use at higher speeds.
"Bigfoote" seems to indicate that a Sportpilot would work and, as I
recall, that was nowhere near as expensive as other units. Of course,
you get what you pay for, yada, yada, yada...
Thanks!
Larry
> On 2008-04-27 20:46:09 -0400, Larry <inv...@invalid.com> said:
>
>> The autopilot I used had no sensor for speed. Does any? It would
>> seem to me that there needs to be one because response to the wheel is
>> proportional to your speed underway.
>
> Haven't been paying attention to this thread, but my tiller AP will
> "read" some NMEA speed sentence and the swing can be adjusted.
Do you know if reading the NMEA sentences replaces the fluxgate compass
or is used for longer range navigation (plotting a course with
waypoints). Thanks
--
Larry R
Jere Lull
I think I should have said "phrase" instead of sentence.
I'm a little confused as the speed phrase I'm talking about from the
knotlog wouldn't be affected by the direction the boat was pointing.
The AP can adjust rudder sensitivity and calculate current set from
that speed phrase, as I recall.
The input from the fluxgate would have a different phrase (If our AP
can take an external one).
Our AP calculates a specific-width "lane" between two waypoints,
adjusting its heading (against internal or external fluxgate) vs GPS
heading depending partially with heading to the next mark, but it's
more concerned with getting back into the lane.