B and G double sonar and the way around?

[CraigandHan]

Hi guys,

happy new year.

I am currently trying to work a way around installing a sonar for my B and G. At the moment i have a transducer for the autohelm (i believe, new boat) that powers all the old ST50 raymarine instruments and autohelm on our sailboat.....all these instruments go through a miniplexer to the b and G to convert to NMEA200.

This all works perfectly (thanks to a miniplexer update).

Now one thing i would like is a sonar attached to the B and G. Me and the misses do a lot of anchoring around jersey and like to know the bottom make up before we drop, Yes i get the whole line and lead weight etc etc but lets be realistic, i want to know what's underneath if i can have access to it.

The problem is i now take it i have a sonar on board already and dont want anything to interfere with it, especially the aurtohelm. What this sonar is I'm not 100% yet but think it will be a P79.

One option is the very expensive forward scan from B and G but i was wondering what other people have done, surely other people have the same problem?

Can i just put another P79 on the other side of the boat i.e to port when the other trasnducer is on the starboard. I take it i must have a transducer for the depth etc, Can this instrument be accessed/ rerouted up to show sonar?.

Thanks once again

Craig

 

[tillergirl]

Not sure what you mean by a 'sonar'. An Airmar P79 is a standard in-hull 50/200 transducer. No point have a pair of those either side of the hull. 2020 Bottom Coverage Calculator | AIRMAR

Could well interfere with the Autohelm transducer which will be an Airmar transducer and probably also 50/200 depending on the model.

 

[CraigandHan]

Sorry tiller I wrote the wrong word, I mean transducer so basically I have an autohelm transducer and want a sonar transducer as well if that makes sense,

 

[tillergirl]

That's fine. Sonar can be used in diffferent ways. But effectively you are planning to use very similar transducers.

1. If you plan to use one x P79 and the 'old' Autohelm it would be worth experimenting first. So you could rig up the P79 temporarily with the B & G but you would need to disconnect the autohelm to the multiplexer and see if you get each system working ok independently while the two are working. I have done that with two systems and it worked fine BUT one was a 50/200kHz 'ducer, the other had 83/200kHz. Separating the two transducers - e.g. one forward, one aft might eliminate conflict if any occurs.
2. Using a pair of P79, i.e. one either side of the 'V': I would suggest there would be no benefit. The footprints are going to be very similar (note the link I provided before). Some manufacturers do provide a facility for twin transducers where a pair of side scan transducers are used (because the keel prevents a single 'ducer to see both sides). Humminbird do and I think Lowrance do.
3. I would suggest a Fishfinder would be better for the purpose. A DI Display (Down Image), say Humminbird for example, would provide a 455/800kHz transducer - set to 800kHz is sharpest in shallow water. The point of that kit is for fishermen but nevertheless would allow you to do a tight circle to see if the ground is flat. There are issues about whether a standard transom transducer would work (possible but...) or whether you would need to pay for a thro-hull 'ducer.

The possibilities are wide. It might help you if you do a bit of reading. If you pm me an email I will send you a copy of the latest Humminbird Helix manual (330 pages!). It has some very useful explanations of the effect of different transducers of theirs and what images could be displayed, e.g. Split Sonar Views, Down Imaging, Side Imaging. Their business is about selling kit to fishermen but it would work for you.

 

[Ningaloo]

I'm not sure what you are looking for or exactly what you mean by autohelm - presumably an autopilot however this won't use/require depth.
If you have a depth transducer with nmea0183 output converted to N2K then you should already have depth PNG available to the B&G.
If you have a large vessel I could see benefit in a 2nd stern depth transducer if mooring stern to in the med but this would be of limited benefit in CI.

 

[CraigandHan]

Sorry I really haven’t explained myself well, I have a transducer for depth and boat speed, for the old NMEA. I want to also be able to have a transducer for sonar to go into the back of my B and G port, however I’m worried that the current transducers i have on the boat will be interfered with with the sonar one that I want to get, does this make better sense??

 

[CraigandHan]

As in I want sonar, not just depth... but if I put a sonar transducer in I have been told it will interfere with the ST50 instrument transducers I already have I.e for the autohelm...

 

[Ningaloo]

Ok understand you want something like the B&G forwardscan. I think you will find that this can work in conjunction with a simple depth transducer. I believe the install manual specifies the minimum separation distance required between the two.

 

[Ningaloo]

The ForwardScan® transducer operates at 180 kHz to reduce interference from traditional 200 kHz echosounders, and provides:

• Maximum forward view of 8X your current depth e.g. at 3 m (10 ft) depth, see up to 24 m (80 ft) ahead.

• Nominal forward view of 4-5X your current depth e.g. At 3 m (10 ft) depth, see 12-15 m (40-50 ft) ahead.

 

[CraigandHan]

Yep this is great Ninga the only question was is there any other transducers out there as the forward scan is very expensive!

 

[CraigandHan]

Yep this is great Ninga the only question was is there any other transducers out there as the forward scan is very expensive!

“With mixed reviews of how well it works”

 

[Ningaloo]

As far as I know radar and sonar are not covered by N2K as they carry too much data. As such I believe you will need to stick with B&G (or at least Simrad) kit as the data is of a proprietary format.
Personally I can't see any benefit in sonar in a well charted area like the CI. With a plotter at the helm station you know exactly where you are.

 

[CraigandHan]

Totally understand ninga,

but the plans for the boat are far wider than the Channel Islands and, being a local myself, shifting sand bars at the minqs and ecrehose,the East coast gutters are extremely dangerous, as well as some areas of the south coast,

as said before I spend most of my time at anchor, and generally don’t like crowds of other boats around which means I am able to find places other people would potentially not want to go, not to mention the occasional good fishing spot for lunch... sonar to me on a sailboat is invaluable, but I think I may have a different view than some people