is forward facing sonar worth it?

[oldgit]

I had an echopilot in an old slow mobo and I found it fairly pointless, it would show you what you are about to hit but not in time to do anything about it, .

Also fairly pointless on slighty faster MoBo, probably far to late to take avoiding action anyway.
Waste of space on muddy East coast where a fishfinder/ depth sounder gives all info you hould need.
Mine came with the boat, was stripped out and sold on Ebay.
Might be of some use if you boat in an area with sudden pointy hard rocks likely to ruin your day.

 

[omega2]

Pointless if you will pardon the pun.!

 

[maby]

Having kept a boat on the Exe for five years we have a local saying. There are people who have run aground and those who are lying. I am in the former group.

Our east coast version was "there are people that have run aground and people that haven't yet."

 

[jonic]

The smart arse answer to that would of course be to look at charts, haha.

Indeed, however in the Bahamas, parts of the Virgin Isles and other areas of the Caribean the charting was significantly out and the coral is contsantly growing. Moving through the narrow cuts in the reef can be very tricky and the charts can actualy lead you into danger if the coral has grown since the chart was published. We used to con our way through the gaps at 3-4 kts, sometimes with just feet to spare, but found the echopilot to be extremley accurate.

Likewise the charted inlets on the East Coast USA often had moving sandbars, especially if a Hurricane had just re-arranged the seabed, so again just following a chart could be dangerous.

 

[Salty John]

Interesting to hear of your experience with the Echopilot Bronze, John. I inherited one with a boat and, sailing the same areas as you, I found it totally useless!
I found that for it to be of any help in terms of advanced warning we needed to be in very shallow water, moving very slowly, and would already be eyeballing it.
Diff'rent strokes...etc.

 

[savageseadog]

Hi Pete.

I’m not sure any of your example situations are too sensible. “Feeling about” sounds risky and “18 inches under the keel” surely not ideal with a fixed displacement and tidal waters ?

I see what you are saying though.

It's standard stuff with a deep draft yacht

 

[pagoda]

It's standard stuff with a deep draft yacht

Not mentioned yet is the actual progress of your vessel at 5 Knots or so? It's not really fast?? if you consider the length of your boat in comparison (nominal 10m?) you will have covered that distance in about 4 seconds. What's your emergency stopping distance from 5Kts?? 2 or more boat lengths?.
We have B&G FLS. It is by no means perfect but it is helpful for identifying the bottom profile several boat-lengths ahead. It works best at low speeds and modest sea conditions. My best procedure is to slow right down with less than 2m under the keel and creep in beyond that. On the west coast of Scotland or Ireland (or Sweden) you can easily have outlying (and unsurveyed) well covered rocks. FLS will show them up. Providing you are <3Kts feeling your way around it is good to have some info beyond chart data. To get better resolution and range gets you into Commercial grade scan sonar equipment. Which might suit you or your pocket?

 

[GHA]

There is a cheap manual option, without the need for a special power supply or transducer.

Fishing rod, line, weight and a float.

Get a member of the crew to stand near the bow. Set the float for minimum depth required and cast forward. If the float stands upright you can carry on sailing.

Great tip for scoping out an anchorage from the dinghy, ta . :encouragement:

 

[longjohnsilver]

Interesting to hear of your experience with the Echopilot Bronze, John. I inherited one with a boat and, sailing the same areas as you, I found it totally useless!
I found that for it to be of any help in terms of advanced warning we needed to be in very shallow water, moving very slowly, and would already be eyeballing it.
Diff'rent strokes...etc.

I have one on our current boat. I honestly can’t remember the last time I turned it on, must be quite a few years ago. Maybe I should give it another go, but I have found it pretty useless.

 

[AntarcticPilot]

As with radar but in three dimension, not two, there are physical restrictions to what CAN be seen with these. Basically, the beam width of a sonar is quite wide - around 10 degrees if I remember rightly, and the return will be from the closest object within the beam. So the entrance to a narrow channel could be invisible quite easily - it wouldn't take a particularly unusual geometry for a 10m wide channel entrance with hard limits to be invisible at a range useful for entering it. The good news is that it will always see the danger closest to the boat; the bad news is that it won't see a safe passage under some likely circumstances.

The range of these things is such that it is unlikely to give enough warning for navigation under sail; without responsive speed control I don't see how it would be useful. Under motor I can see them being of limited use, but then there's going to be a conflict between going slowly enough to respond to what you see and maintaining steerage.

 

[Sgeir]

Pricey for what it is.

True, but having come off worse than the the rocks that I've accidentally steered into......

 

[maby]

As with radar but in three dimension, not two, there are physical restrictions to what CAN be seen with these. Basically, the beam width of a sonar is quite wide - around 10 degrees if I remember rightly, and the return will be from the closest object within the beam. So the entrance to a narrow channel could be invisible quite easily - it wouldn't take a particularly unusual geometry for a 10m wide channel entrance with hard limits to be invisible at a range useful for entering it. The good news is that it will always see the danger closest to the boat; the bad news is that it won't see a safe passage under some likely circumstances.

The range of these things is such that it is unlikely to give enough warning for navigation under sail; without responsive speed control I don't see how it would be useful. Under motor I can see them being of limited use, but then there's going to be a conflict between going slowly enough to respond to what you see and maintaining steerage.

All quite true, of course. I guess my answer would be that the use of charts and good seamanship should ensure that you never find yourself travelling at high speed towards an obstruction. There have been plenty of times sailing on the east coast or Solent when we have wanted to enter a shallow creek which we have known was at the shallow end of our safe range - we proceed at dead slow, with eyes glued to the depth gauge - but there is still a risk of touching bottom, albeit at a speed which is unlikely to damage the boat. I would certainly like to have forward facing sonar to help under those conditions, but thus far it has not been sufficiently high up on my list of priorities to justify the not inconsiderable cost.

 

[Buck Turgidson]

Point to note on a twister is where is he going to put it?
To get it close to vertical and away from the keel you need a fairing on the hull which is a bit of a job.

 

[jonic]

Interesting to hear of your experience with the Echopilot Bronze, John. I inherited one with a boat and, sailing the same areas as you, I found it totally useless!
I found that for it to be of any help in terms of advanced warning we needed to be in very shallow water, moving very slowly, and would already be eyeballing it.
Diff'rent strokes...etc.

It might be to do with the location? Ours are mounted just fwd of the keel and faired to keep them horizontal. Could even see anchor chains.

 

[maby]

Point to note on a twister is where is he going to put it?
To get it close to vertical and away from the keel you need a fairing on the hull which is a bit of a job.

That was the issue I faced when considering it - not easy to mount on most sailing boats. When this thread started, I took another look at the available options and I see that there are through-hull mounted sensors similar to the standard depth gauges but with the transducer protruding slightly and cut at an angle to face forwards - those may be easier to mount on a sailing boat.

 

[rogerthebodger]

That was the issue I faced when considering it - not easy to mount on most sailing boats. When this thread started, I took another look at the available options and I see that there are through-hull mounted sensors similar to the standard depth gauges but with the transducer protruding slightly and cut at an angle to face forwards - those may be easier to mount on a sailing boat.

I do have a forward looking sonar but not used in anger.

This is the transducer mounting with the fairing block supplied and cut to suit.

Mine looks both vertical and horizontal. so you can switch depending on what you are looking for.

Horizontal for looking for a narrow channel. Vertical for looking for a shelving shore.

this is my unit

http://halling.com/Interphase/TwinScope.htm

 

[Keith 66]

Our Sabre fin keel has a £105 lowrance fishfinder with its transducer mounted on the centreline about 18" forward of the ballast keel, I ground a little well for it in the hull & built up a small flat fairing block on the veed hull glassed over. Not sure how far forward it looks but you get a lovely trace of the bottom & an idea of what is coming.
We wouldnt be without it.

 

[steve yates]

Interesting feedback, thanks everyone. I'll pass your views on and wait and see what he decides.