NMEA and SeaTalk on same network

[Manlio]

I have on board devices from Raymarine, working under SeaTalk protocol
and also a Raystar plotter using a NMEA GPS signal. On the boat there
is a NMEA to SeaTalk Bridge Unit, so exists a "mixing" of all the
data. Upto now : no problems !

My question:
I would like to add a second GPS (Raystar 125) connecting its SeaTalk
output signal to the SeaTalk network. This would be meant to be a
reserve in case of failure of the first one. May I leave it in
operation, having GPS data coming from two devices, or it's better to
keep it off and disconnected while the first one is in operation ?

In theory there should not exist collisions on the talker side, but
what about same data flowing on the same network ?

Appreciated your comments

Manlio

 

[Manlio]

Followup to msg on Sun, 02 Mar 2008 06:11:56 -0600, Geoff Schultz
<geoff"at"@geoffschultz.org> :
(Original msg on bottom)

Thanks Geoff,
you contribution is much appreciated. It's about what I was
forecasting to happen.
Cheers
Manlio

 

[Larry]

I would like to add a second GPS (Raystar 125) connecting its SeaTalk
output signal to the SeaTalk network. This would be meant to be a
reserve in case of failure of the first one. May I leave it in
operation, having GPS data coming from two devices, or it's better to
keep it off and disconnected while the first one is in operation ?

You must NEVER have TWO GPS units talking to the network at the same time.
They will NEVER put out the same data. The results are that every plotter
on the boat goes crazy with the conflicting data streams, your position
jumping from A to B to A to B all the time.

If you want to have a backup GPS, that's fine as long as only ONE of them
are talking to the system at a time. We have two, one Raystar 120 and one
Garmin. There is a simple toggle switch to select which one of them is the
talker so noone can set both of them talking simultaneously.

 

[Manlio]

Followup to msg on Sun, 02 Mar 2008 18:08:06 +0000, Larry
<[email protected]> :
(Original msg on bottom)

Thanks to all of you. You have just confirmed all my presumed doubts
making them certainty.
BTW it's too much important to have a "spare" GPS ( I will keep it off
in the right way) as, despite my age (!!) I will have some trouble to
unbury my old sextant !! )

Manlio

 

[Larry]

I will have some trouble to
unbury my old sextant !! )

I keep my nice sextant with me. The dock usually doesn't move more than
a mile or so when I check it....(c

 

[Larry]

Is there a seatalk-only heading sensor? I've got a heading sensor but
it's attached to the autopilot, and thus only works what that's turned
on. I tend not to use the autopilot but would like a header
indicator.

-Bill Kearney

Sure. Raymarine calls it a "Smart Heading Sensor" and it also includes an
electronic gyro that feeds rate-of-turn data to the system.

http://www.raytechonline.com/productdetail.aspx?site=1&section=2&page=389
&product_id=699

Pay particular attention to the instructions on placement and orientation
of the big box with the gyro in it when you install it. The fluxgate is
installed elsewhere so they do not interact. Don't install them next to
each other.

"Lionheart" has this overpriced beast on it and it does work, I suppose.
But, the compass sensor for the B&G "Network" Pilot autopilot works so much
better we hardly ever use it. The B&G Pilot "learns" and corrects its
oversteering shortly after you install it, making its own chart of how to
make smooth turns and compensate for the boat's motion, so the SHS is just
overkill. The B&G self compensates its compass sensor, storing its offsets
very nicely. Compass data to the network comes out of the Pilot computer,
already nicely compensated. The SHS is the backup unit, after comparing
them for a while.

Just like anything else for the boat, bring your high-limit credit card...
(c;

 

[Larry]

This
also partially explains my waterline loss...

Fess up...How many tool boxes are there?

 

[Larry]

One of the key things that we've done is to place all of our stores
into an Access database that I designed. While it doesn't include the
daily use tools, it does include the ones that are rarely used. The
database contains over 1400 items and there are 66 storage locations
defined. We're very good at keeping the database up to date, so when
we need a tool, part, food item, etc, we can quickly lay our hands on
it. I can't imagine life without it.

Oh, you've taken all the fun out of it! There are a thousand little
cubby holes in any Amel Sharki to hide tools/parts/stuff. It can take
days to find that "special place" our Cap'n took real pains storing that
one little spanner you can't get it off without. The database would be
HUGE.

Our Cap'n loves his tools. You're right, it only GROWS, as does the
hardware stores. We were headed to some sleazy bar for lunch and
libation after working in our beloved bilge and happened upon one of the
neighbors trying to make a door fit in his galley with a typical
seaman's knife. "Wait a minute", Cap'n says, headed back to his boat.
3 minutes later, the neighbor was using a beautiful wood plane to shave
the wood perfectly off that door. WOOD PLANES ARE STANDARD CRUISING
EQUIPMENT! You just never know when you'll need to use the on-board
wood shop on a sticky cabinet door that's mission critical....(c;

We don't have an awl. We have a COLLECTION of awls. I never found an
anvil. That doesn't mean there's not one aboard! "What the hell are we
gonna do with this gear puller??" "What? We don't have a lathe?!"

You can tell when your tool collection is nearing "adequate" when the
boatyard workers are borrowing your special tools they don't have in the
biggest boatyard in town.....(c;

Seen that...first hand.

She isn't fast, but SHE'S FULLY EQUIPPED!
She needs a towed BARGE on a long line!

 

[Larry]

You bet. I carry a nice little bronze block plane made by Lie-Nielsen
in Maine:

http://www.lie-nielsen.com/catalog.php?sku=102

http://www.lie-nielsen.com/viewimage.php?grp=1221&layout=blank

It is razor sharp and a joy to work with.

Some sailors just can't lay out on a beanbag, soak up some sun, and do
ABSOLUTELY NOTHING for more than 10 minutes at a stretch.