Autopilots
 

Larry wrote:
Roger Long wrote:

"Edgar" wrote

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


Actually, Roger, I'm a retired electrical engineer so I do have a bit of
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.



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

Autopilots
 

Richard Casady wrote:

On Sun, 27 Apr 2008 21:44:36 +0000, Larry wrote:


(Richard Casady) wrote in
t:


Since when is brass magnetic?

Casady



http://www.kayelaby.npl.co.uk/genera...2_6/2_6_6.html


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


It showed magnetic susceptibility of brass as 1, steel as 150.

Less than 1% as magnetic as steel?


Richard

Autopilots
 

On Sun, 27 Apr 2008 21:13:31 -0500, cavelamb himself
wrote:



http://www.kayelaby.npl.co.uk/genera...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

Autopilots
 

On Mon, 28 Apr 2008 06:03:18 -0400, "Roger Long"
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.

Autopilots
 

On Sun, 27 Apr 2008 10:49:18 -0400, Larry wrote:

The autopilot I had used a fluxgate compass. The trolling problem was
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.

Give it a rudder so it can become the happy little second-order system
it was born to be.

Autopilots
 

Roger Long wrote:
I haven't given much thought to the innerworkings of autopilot control
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

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
rapp at lmr dot com

Autopilots
 

Wayne.B wrote:
On Mon, 28 Apr 2008 06:03:18 -0400, "Roger Long"
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.


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
rapp at lmr dot com

Autopilots
 

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. 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
rapp at lmr dot com

Autopilots
 

On Tue, 29 Apr 2008 10:53:50 -0400, Larry 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.

Autopilots
 

Goofball_star_dot_etal wrote:
On Tue, 29 Apr 2008 10:53:50 -0400, Larry 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 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.
--

Larry R
rapp at lmr dot com