Echo Sounders and mud

[Durcott]

Hi Folks,

I've just moved my boat to a river mooring near Weston super Mare.

The echo sounder was never 'great' in the Bristol Channel once we get to the liquid mud East of Cardiff, but around the Avon / Axe - might as well switch it off and save the battery . (Works perfectly in the lock at Cardiff )

Generally speaking - are there any types / makes of echo sounder that work well on really soft mud and through mud filled waters, or are at least better suited to this sort of abuse?

(I once had an ancient sounder which had a little amber neon light that whizzed around in a circle. That worked really well through the mud - you could almost estimate how thick the mud was...)

Cheers

Jeff

 

[BarryH]

I find the Gain control really useful.......

 

[alexrunic]

I've got a Nasa Clipper and use it in the Wash and Humber and always found it accurate and reliable, both places have very brown muddy / silty water.

 

[johnalison]

I think that my 10 yr old Raytheon is fairly typical of modern sounders in that the gain is automatic. It works fine in East Coast mud.

 

[Durcott]

Hmmmm - interesting. I'm fairly sure the gain is up on my unit.

These 3 replies suggest it really ought to be working regardless of the mud, so I'll assume it needs a bit of TLC.

Cheers

Jeff

 

[prv]

(I once had an ancient sounder which had a little amber neon light that whizzed around in a circle. That worked really well through the mud - you could almost estimate how thick the mud was...)

I believe NASA still sell a whirly sounder if that's what you prefer.

Pete

 

[BarryH]

I think that my 10 yr old Raytheon is fairly typical of modern sounders in that the gain is automatic. It works fine in East Coast mud.

Nasas' gain control is in the "SET ENG" menu. Bit fiddly to get to, but easy enough once you've done it once or twice

 

[theoldsalt]

Durcott (Jeff),

Maybe you are thinking of the Seafarer. I had one many years ago.

http://www.ebay.co.uk/sch/Vehicle-Parts-Accessories-/131090/i.html?_nkw=seafarer+echo+sounder

 

[Seajet]

NASA do make an old style whirly sounder; I too find the lack of an accessible gain control can be a pain; if I was somewhere like the Bristol Channel I'd have an LCD job for normal sailing, and a whirly job with gain control ( transducer in not through hull ) when in brown soup.

The whirly jobs do of course use a lot more electrical power, and remember their old trick of going right round the scale so '61 feet' becomes a heart-stopping '1 foot' !

 

[Durcott]

Ha happy days

Yes - very similar to that piccie, but 'simpler'. Ebay for 99p eh? Hmmmmmm...

I remember the first time it rolled around to 1 foot. I probably did a crash stop - followed by a change of underwear.

Jeff

 

[AntarcticPilot]

I am considering the geophysics of echo-sounders, and am thinking as follows:

Mud (especially soft mud) is readily penetrated by sound waves.

The strength of the reflection from the water/mud interface depends on the contrast in velocity of sound waves between the two media. The bigger the difference in the speed of sound, the stronger the reflection.

Very wet mud might not present a lot of contrast between water and mud, giving a very weak reflection.

The interface between very wet mud and underlying consolidated sediment or rock might give a much stronger return.

Therefore, you COULD get returns from whatever is under the mud rather than from the top of the mud - not a good situation!

Changing the gain isn't likely to make much odds - yes, you'll get a stronger return from the water/mud interface, but you'll also get a stronger return from the mud/substrate interface. I guess modern echo-sounders use a tracking system to follow the echoes, and will tend to follow the strongest return. Note I said "guess"; they might follow the shallowest return. Drawbacks to either system; the former might follow the bottom of soft mud; the latter might follow a thermal boundary in the water-column.

It strikes me that the only kind of sounder that will give enough information to allow intelligent interpretation of the situation would be either a fish-finder that would present a profile allowing the different interfaces to be seen, or the spinning kind, where multiple interfaces can be seen. The fish-finder would be clearer to use, as it presents an along-track profile of the reflections.

Not an issue where I sail - hard rock or firm sand mostly!

 

[Cantata]

I sail in the centre of the Mud Universe, and my ST60 seems to work just fine.

 

[Durcott]

I sail in the centre of the Mud Universe, and my ST60 seems to work just fine.

Ahh - funny you should mention that one. There's one of these fitted on a boat I get to sail now and again in Milford Haven. I was impressed with how this gave 'solid' and accurate readings on the river mud. Good enough to pilot up the river on contours. I wouldn't attempt that on others I've used.

The depth reading, reduced to soundings, matched the chart ALMOST without fail.

So - that gets me to the root of the issue. Why is this particular device seemingly 'better' than others? Does it have some particular trick up its sleeve?

(I believe other depth sounders are available )

Jeff

 

[AntarcticPilot]

I sail in the centre of the Mud Universe, and my ST60 seems to work just fine.

Ahh - funny you should mention that one. There's one of these fitted on a boat I get to sail now and again in Milford Haven. I was impressed with how this gave 'solid' and accurate readings on the river mud. Good enough to pilot up the river on contours. I wouldn't attempt that on others I've used.

The depth reading, reduced to soundings, matched the chart ALMOST without fail.

So - that gets me to the root of the issue. Why is this particular device seemingly 'better' than others? Does it have some particular trick up its sleeve?

(I believe other depth sounders are available )

Jeff

Not all mud is the same. The OP mentioned specifically very soft, wet mud. Most mud elsewhere is actually quite solid; it depends entirely on the water content, and the mineralogy of the mud. Humber mud (which is the kind I knew when I were a lad) is actually quite hard; hard enough to sustain near vertical banks at the edge of channels. What we yotties call mud actually covers a wide range of possibilities, with variations in the particle size, and the types of mineral present (basically, the ratio between quartz and clay minerals).

 

[Kurrawong_Kid]

Mud readings.

Just a thought. Have you antifouled the transducer? Affects the sensibility I believe.

 

[DanTribe]

My favourite echo sounder was the Seafarer dual display. It had a digital read out which saved power, an "asdic" type audio alarm which got more frantic as depth dropped, and a spinning wheel display if you needed it.
Unfortunately a lightning strike did for it and I wasn't able to find a similar replacement.
I used to think that the whizzy wheel display gave an idea of what the bottom was like, depending on the fuzziness of the echo.

 

[johnalison]

I used to think that the whizzy wheel display gave an idea of what the bottom was like, depending on the fuzziness of the echo.

That's certainly true. It was a lot quicker than all that messing around with tallow on the lead.

 

[Dave_Seager]

If anybody really wants the rotating light type, they are still available in the Nasa Stingray range.

They are an improvement over the old Seafarers as they use LEDs instead of neon and have high and low depth alarms. You should be able to find them for sale for less than £100.

 

[alahol2]

I'd go for a fishfinder. The display shows up weeds over the bottom as a dual trace so I would expect it to also show sloppy type mud. Ours also has a manual (or automatic) gain control albeit in a menu rather than a dedicated knob. Often cheaper than an echosounder and much more fun to play with.

 

[Lakesailor]

I've just started using a fishfinder that came with a boat.
It really is excellent. I passed astern of the car ferry the other day and not only did it show each cable but also how deep they were (18ft over a 24ft bottom).