B&G forward scan

[a64pilot]

I thought Canbus was way faster than NMEA 2000?

[Saltyhog]

Originally Posted by a64pilot

I thought Canbus was way faster than NMEA 2000?

CAN data rates can be from 125 kbps to 1 Mbps. NMEA is an implementation of CAN where the data rate was chosen to be 250 kbps. The data rate is chosen based on the expected max length of the bus. Shorter bus's support faster data rates. I guess the folks at NMEA figured 250 kbps was fast enough and would provide robust communication.

[mbullock]

Originally Posted by Sputnik

The only thing my B&G FS is consistent in is being inconsistent.
IS IT JUST ME
Neil

Pleased its not just me then! Has anyone solved these problems? I've just installed a Vulcan 7FS and a Forward Scan transducer. It's output is totally random, sometimes the depth shown is 'about right' compared to my Raymarine transducer but then within a minute (whilst the boat is stationary at dock or anchor) it will change the depth up to +120% then back again! The forward scan bottom profile will also change in an erratic way - sometimes it looks great then other times its way off.

I am just starting down the road with Navico Uk support but they don't seem to have too many ideas, are 'swamped' with calls from our Easter weekend (is their stuff so bad!?), and can't offer help. Meanwhile, we leave on a circumnavigation next week so time to get this sorted whilst 'static' is ticking away!

I'm not at all happy with this kit at the moment. Hopefully, the dump file they have asked me to send will help... but I'm thinking I wasted close to GBP1000 at the moment

Any more recent experiences appreciated.

[Frankly]

I have no experience with the subject sonar, but I do have quite a bit of experience with sophisticated US Navy forward looking sonars. You may indeed have some hardware issues. Might also try to get into some different water conditions. Projecting a acoustic beam straight down through a water column with varying temperature and salinity usually works pretty well. When you try to do this at an angle then all bets are off. Depending on the water column conditions, I have seen the beam bent down into the bottom or reflected on forward to never return.

Back in the days of Vietnam when the Navy was trying to evaluate sonars to detect swimmers that might be approaching a Navy asset we often observed what we named the "afternoon effect". We would use a standard reference sonar target. On a morning run we could typically detect the target at 400 to 500 yards, by afternoon that range would be down to 40 yards. This happened day after day in a bay environment.

That mfg glossy brochure that shows this nice illuminating fwd looking beam is far from the real world. Sadly the time when you really might need a fwd looking sonar you will often be operating in these types of conditions.

[mbullock]

@Frankly - thanks for taking the time to share that. It's helpful - although I did 'buy' the marketing version

One thing they seem pretty keen on is making sure the transducer is at the correct angle to the hull. Reading your comments I guess that is very critical? The boatbuilders who installed the transducer assure me that it's perpendicular but who knows it could be a degree or so out. My issue is knowing how far out and which way... I could dive down with a protractor (I would if that's what it takes!). Any thoughts on that issue?

many thanks, Malc

[Sputnik]

The angle of the transducer to the hull should not matter within sensible limits, as it is possible to "adjust" the angle electronically in the settings.

Neil

[Frankly]

I did a quick search of the WEB site and they are not very forthcoming with any specs. When I look at the size of the transducer and guess a frequency of 300 to 400 KHZ then that thing is going to have a pretty broad beamwidth (30 to maybe 50 degrees both horizontal and vertical). A few degrees off vertical is going to be NBD.

When we (Navy) got sophisticated enough to calculate the actual direction of the beam travel based on a vertical sound velocity profile, some small changes in salinity/ temperature makes for some large variation in the path the sonar signal. Then what we had observed in those tests years earlier all started to make sense.

Assuming you are not experiencing a hardware problem, then get out and play/practice a little bit. What you and others are trying to do is not an easy nut to crack. Even with expensive and sophisticated sonar equipment, results will be heavily influenced by the water column conditions.

One secret I have learned over the years in difficult/ unknown navigation situations, "slow speed is your very good friend".

[JPA Cate]

One secret I have learned over the years in difficult/ unknown navigation situations, "slow speed is your very good friend".

Good one, Frankly. Also agree about getting out and using it to look at "stuff". Our old Interphase sees other boats' keels across the dock from us. After a while, you learn to relate what you see on the screen to what the chart shows, like, "oh, yeah, there's only a boatlength between me and the edge of the sandbank." Nice to know when it's dark and you can't see the edge.

In the Solomon is, ours kept us off a reef we couldn't see through muddy water. I think one's need for a forward looking depth sounder depends on where you're going to be sailing. There may already be enough data that you don't need the instrument. If you like to explore [slowly] in unfamiliar areas, it can definitely be a handy tool.

Ann

[Jim Cate]

Originally Posted by Ann T. Cate

Good one, Frankly. Also agree about getting out and using it to look at "stuff". Our old Interphase sees other boats' keels across the dock from us. After a while, you learn to relate what you see on the screen to what the chart shows, like, "oh, yeah, there's only a boatlength between me and the edge of the sandbank." Nice to know when it's dark and you can't see the edge.

In the Solomon is, ours kept us off a reef we couldn't see through muddy water. I think one's need for a forward looking depth sounder depends on where you're going to be sailing. There may already be enough data that you don't need the instrument. If you like to explore [slowly] in unfamiliar areas, it can definitely be a handy tool.

Ann

Adding to Ann's comments:

The Probe that we still use involves a design from more than twenty years ago. It still works! It is surprising to me that B&G (or others) have not yet come up with a working improvement on this. Hell, it seems like perhaps that should read just "working" and not require "improvement"!

We've posted several times on our positive experience with the old Probe!

Jim

[Sputnik]

In order to try to fault find my useless FS I have replaced the transducer, sonarhub, and chartplotter. All have made no difference. Tried all the different settings.
The transducer is vertical in the hull in-between the keels. I have tried switching all other equipment off in the boat in case it's an interference issue. It makes no difference if we motor slowly, sail slowly, or even on a mooring.
I think that this issue is a geometry problem, when the angle becomes so shallow the sonar pulses are not returned but glance off of the bottom. Having said that the unit looses bottom lock randomly, but usually at shallow depths.
I am now at the point of sending the FS back for refund, as B&G have still not come up with an answer.
Shame, lovely kit otherwise.
Neil

[Fluer de Mer]

FYI: This is a photo of a new Beneteau with the factory installed B&G forward scan sensor.

[Dave_S]

Hi all

I just bought a Zeus 3 but decided against the FS because it protrudes through the hull and while it should stop me from running aground if I do it may tear out and leave a big hole.

A lot of talk questioning the reliability and that it only protects one hull from bommies made me decide against.

Still not sure if my reasoning is sound. Happy to hear any thoughts, I've still a couple of weeks before the boat comes out.

[Neptune's Gear]

Nope, not sound. The fwd scan transducer has a stainless steel through hull, as the plastic could cause an issue in an impact. The transducer itself is designed to shear off at hull level if hit sufficiently hard, without damaging the through hull, or compromising water tightness.
The fwd scan dos not "protect" you from anything, it's simply another tool. IMO it's a great device, especially for approaching new anchorages and shallow channels etc.

[Dave_S]

Originally Posted by Neptune's Gear

Nope, not sound. The fwd scan transducer has a stainless steel through hull, as the plastic could cause an issue in an impact. The transducer itself is designed to shear off at hull level if hit sufficiently hard, without damaging the through hull, or compromising water tightness.
The fwd scan dos not "protect" you from anything, it's simply another tool. IMO it's a great device, especially for approaching new anchorages and shallow channels etc.

Thanks for that. You would have thought someone would have mentioned that at the show.

By protect I meant when looking at the display you only see what's in front of one hull, and you may hit something with the other.

[JPA Cate]

Originally Posted by Dave_S

Thanks for that. You would have thought someone would have mentioned that at the show.

By protect I meant when looking at the display you only see what's in front of one hull, and you may hit something with the other.

Dave, with a 20-25 ft. beam, maybe you want one for each hull?

To evaluate if you need one, ask yourself if you will be needing to "see" into murky water, one thing they really shine at. Or, are you expecting to travel coral-laden lagoons? The way bommies and reef structure shows is also excellent. Our old Probe is not too sure where soft mud starts, but gives a good return on hard mud, sand, and rock. Mostly Qld water is clear enough for it not to be a worry. You might be happier with a depth sounder (just a simple one) for each hull. Or, ask some of the catamaran folks, if it is a problem for them, and why, or why not?

Ann