Deep water on the East Coast?

[TimfromMersea]

When coming out of the Colne the week before last, the 'B and G Network Nav Speed and Depth' sounder suddenly went to 76 metres, then to 100 metres, then to 132 metres.....turned it off and then on again, and it was fine for a few minutes, then when we were approaching the Molliette, there it went again - 124 metres, then back down to 62 metres. Switched it off and on again and it was fine.

Up the Blackwater last week, no problem with it all day.

Then yesterday, approaching the East Mersea Youth Camp and tucking in to the shallows on the East Mersea flats, getting out of the flood tide, off it went again - up to 140 metres this time. Off and on again, then turned up the Blackwater, anchored at Osea for lunch, and it was fine all day.

Has there been some clandestine dredging at East Mersea, to give deep ocean trenches, for disposal of the nuclear waste from Bradwell? Or is there some electronic interference, that we what not of, being transmitted from East Mersea by person or persons unknown?

Or is my sounder just faulty.........!? and if so, does anyone have any ideas as to what the problem might be?

 

[tillergirl]

I hope you won't regard this as selfish but I seriously hope your depth thing has reached the winter of its life. Otherwise we might be about to disappear into a sinkhole.....

 

[FullCircle]

Sounds like the wiring may be getting dodgy connections, causing a voltage drift.
Unplug each bit and check to see if there is any green verdigris or other corrosion in the plug/pins. Clean and reseal.

 

[jerrytug]

My sounder goes bananas when it picks up echoes from another boat's sounder, took me a while to work it out, I used to think it just went crazy now and again.

 

[Athene V30]

My sounder goes bananas when it picks up echoes from another boat's sounder, took me a while to work it out, I used to think it just went crazy now and again.

Was alongside another boat waiting to lock in at Heybridge and his depth was reading 100 meters plus which we put down to interference. At Low water no sink holes were spotted.

 

[pioneer]

Mine ES tells lies when the oil bath is low, although that has tended to be shallow readings rather than deep ones. Just a thought before taking the system apart/replacing kit.

 

[Leighb]

Mine tends not to like marinas with muddy bottoms, depth can go form normal to 75m then tick back down to the true reading and do it all over and over, very irritating, but easily cured by turning it off.

It never seems to happen when under way though.

 

[cookjwm]

surfing REALLY big waves?

 

[TimfromMersea]

Mine tends not to like marinas with muddy bottoms, depth can go form normal to 75m then tick back down to the true reading and do it all over and over, very irritating, but easily cured by turning it off.
.

That's interesting. I've only ever seen this from the sounder over the Molliette bank, both SW and NE of the beacon. I wonder if it's some peculiarity of the consistency of the mud there?

 

[johnalison]

It's not the mud it's them oyster shells. When they are crowded together they absorb sound, like the walls of an anechoic chamber, and this gives rise to spurious readings.

 

[Habebty]

Don't worry, it's official coz there's a sign

[/URL]

 

[ex-Gladys]

Tim, if your connections at the back of the instrument head are clean, it's more likely to be the head than the transducer in my experience... Oil bath check (if it's in hull) is very good advice.

In Ostende last year they were dredging as we made our way in, and that gave some very interesting readings...

 

[TimfromMersea]

It's not the mud it's them oyster shells. When they are crowded together they absorb sound, like the walls of an anechoic chamber, and this gives rise to spurious readings.

I'm afraid I don't have any knowledge of science of any kind and so have no way of telling whether this is (a) a very plausible explanation or (b) a rather late April fool...!

I have only seen this strange effect on the echo sounder in one place around here and so one has to admit that m'learned friend's explanation above has it's attractions, especially as I'm reluctant to start disturbing things that otherwise are working perfectly. Normally well intentioned people that start taking apart things that they don't understand do more damage - as in the words of the famous quote:-

"Lord Finchley tried to mend the electric light
It struck him dead - and serve him right
It is the business of the wealthy man
To give employment to the artisan"

(not that I'm in any sense wealthy!)

Fess up, Johnalison - did you simply make this oyster shell theory up, to have a joke at the expense of the credulous? Or is there some science behind it? I'd love to know

 

[johnalison]

Fess up, Johnalison - did you simply make this oyster shell theory up, to have a joke at the expense of the credulous? Or is there some science behind it? I'd love to know

I'm sorry. It never crossed my mind that anyone would take anything I wrote seriously. I just thought the thread was worth supporting.

 

[ex-Gladys]

On a serious note, disturbed water (watch your sounder when next in a lock) and soft mud can mess it up, if you have ONLY had the problem in one place, just keep your eye on it. Gladys sounder goes mad in Shotley, and on another note, when in St Katz last year, the Tacktick wind display stopped working as soon as we went into the basin, and only started working again once we left. My diagnosis was loads of Wifi signals in the area, rattling round all those tall buildings

 

[johnalison]

Disturbed water can certainly cause problems, usually a falsely shallow reading. There is a place in the Roompot channel where this tends to happen in a strong tide and shallow water.

Another problem can be weed. I last met this in Danish waters in a shallow channel charted as a guaranteed 2.1m but the sounder showing 1.2. A glance over the side showed why.

 

[AliM]

"
Another problem can be weed. I last met this in Danish waters in a shallow channel charted as a guaranteed 2.1m but the sounder showing 1.2. A glance over the side showed why.
"

That wasn't the channel between Lolland and Falster, was it? We had an almost constant depth alarm (set to 1.3m) sounding while sailing through there, a couple of years ago. It's a lovely route, but a real strain on the nerves!

 

[johnalison]

That wasn't the channel between Lolland and Falster, was it? We had an almost constant depth alarm (set to 1.3m) sounding while sailing through there, a couple of years ago. It's a lovely route, but a real strain on the nerves!

Yup. That's the one, though the channel south of Mon is similar. We heard that the charterBavs weren't allowed to cruise these channels.

Suggested remedy. Turn the alarm off.

 

[AliM]

Yes, did that! Then you just worry, seeing the depth oscillating wildly between 2.1 m and your draft! There are some lovely routes between the Danish islands - we did several of them, and hope to explore more.

We are heading Baltic-wards at present - now in Harlingen in order to do the next bit by canal until the weather settles. Are you coming to the Baltic this year?

 

[johnalison]

Take care in Harlingen. There is a bit of pavement that doesn't actually have any bumps, which is where my Ali fell and broke her wrist last year. On the other hand, the folks in the club are lovely.

If you are going back via Denmark, we haven't spent much time there but I have greatly enjoyed the Middle Ages Centre at Nykobing Falster a couple of times, especially if you get to watch the trebuchets being let off. Karrebaeksmunde (?) is a nice spot too. The HM spoke Australian.

Sadly, I have been ordered to take Mrs W to the Channel Isles this year, so will miss the long summer days up there. Have a good time.