Echo sounder - improve or replace?

[rogerroger]

Running aground twice on Saturday confirmed the fact that I need to do something with the echo sounder over the winter.

It's a NASA Target with an in-hull mounted kit. The problems are

1. oil drains out of the in-hull kit so it stops working - OK, so I can seal this better
2. It's to port of the keel so stops reading when heeled a fair bit to starboard.
3. It does not read anything below 1 meter - this is a nonsense as there's a huge difference between 10 cm and 90 cm when working in shallows.

Should I ...

Chuck everything out and start again ?

Sort out the in-hull kit and add a new display - if so, can I add a different make unit onto the existing coax ?

Are there advantages to a through-hull unit and is this a big job ? (don't like the sound of another hole in the hull!)

Many thanks

Roger Holden
www.first-magnitude.co.uk

 

[Guest]

Get rid of the echo sounder and replace it with a decent Fishfinder, Raythoren. L365. reads speed, water temp and depth plus shows seabed. It is much better to use a through hole and it does not cause any problems...

 

[rogerroger]

Interesting. How does it read speed ?

Roger Holden
www.first-magnitude.co.uk

 

[RobertMartin]

I would assume the transducer has a paddle wheel on it. I am just about to buy one for my yacht. A friend has one and swears by it... It helps out with anchouring to as you can see the seabed contour...

Bobby aka Seawolf..
Sail as if your free

 

[Guest]

To sort out the in-hull leak is easy .....
Break away the tube from the hull, carefully so as not to split the tube.
Remove all the glue / resin whatever held it in place.
Take Mr. Muscle oven cleaner and spray the area to foam up and clean the area.
Wipe away the gunge. Spray again. Leave for about 10 minutes.
Wipe away and then wash with fresh water.
Dry it of.
Now clean the end of the transducer tube and dry.

Now that you've cleaned both, you can decide if you want it back in the original spot or somewhere else ! I would suggest somewhere else ... as you already say you have a heeling problem. So clean that spot same way with the oven cleaner ! It gets the best and cleanest surface you could imagine - ready to resin up.

Now shape the end of the tube to stand veryical of the hull and fix in place with a few drops of quick set epoxy. Take liberal amounts of glass resin and filler mixed and glass the tube in place, making a good fillet rising up the tube for about an inch, and out to the hull for about an inch. Make sure it is absolutely all round. Leave to set.

Now fill with 250ml of castor oil from the chemist and insert the transducer till its about 1mm of the hull surface. QED.

As to readings .... I had a Nasa target and it worked into decimal depths .... so yours should as well if mounted well.

Yes you can fit a different head, just compare frequency of the transducer etc. between makes, and you'll find most are similar. NEVER cut the cable - that must remain a function of transmission time and calibration. But really you shouldn't have to change the head.

Changing to through-hull shouldn't make much difference .... yes a little more sensitive, but in practical terms if fitted well .. only small difference.

Chuck it away and start again ??????? No - many others use same and have good results .... there must be a problem in your instalation.

As to changing to a Fish Finder / Contour job ..... excellent machines and reccomended for various reasons ..... but if its depth only you need and you sort out the position of the transducer / readings then why spend a heap of cash ?

I have a Echopilot mini duo display and many told me - forget it, cheap and nasty .... It works very well and below 1 m as well .... same as my old Nasa did on previous boat..

Finally I advise - sort out your fitting before wasting money .... especially if you say the tube is leaking !!!!

 

[gary_yank]

transducer placement

The method I have used to find the best location for the transducer inside a GRP boat is to use a plastic bag filled with water. Place the transducer in the water filled bag and shift the bag around until you find a good location, the outside of the bag may have to be wetted. Mark the location with a pencil, not a grease type marker, sand the paint off, clean and glue the transducer down with epoxy.
Often depth sounding accuracy problems occure if there are small air bubbles trapped in the original glassfibre laminate. The bag method will help find the places to 'shoot through.' I have used this method on about seven boats over about six years and no problems
The above method will not work on sandwich contruction hulls as the core material will insulate the transducer pulse.

 

[rogerroger]

I must admit a fish finder has been on my wish list for a while.

If they weren't called "fish finders" I'm sure they'd sell a lot more. "Graphic echo sounder" would make more sense.

Does the transducer not need to be mounted aft ? or can it be in the same place as a conventional one ?


Roger Holden
www.first-magnitude.co.uk

 

[rogerroger]

thanks for that lengthy reply - extremely handy.

I've got a feeling the coax has been cut and then put together again with insulation tape - I guess this doesn't help.

The spec for the Target says it reads from 0.8m to 180m - surely people want something that'll read down to 0.1 m ?



Roger Holden
www.first-magnitude.co.uk

 

[Twister_Ken]

Down to 10 cm? Only if you've got the transducer mounted on the bottom of the keel!

Mine doesn't need to read to less than 1.2m, after that I'm ploughing.

Bearing in mind the principles of an echo sounder, presumably the duration of the sound pulse sets the mimimum depth it will read. It's no good the propogated sound getting there and back before the 'ping' has finished.

 

[davidphillips]

I had lots of problems with the Target (featured in PBO's July edition) including silly readings in shallow water etc. I traded it in for a Clipper (extra cost about £80) and have had no problems since.

 

[peterg]

Re: Echo sounder

My Autohelm ST30 has an 'offset' setting so that you can ask it to measure from the bottom of the hull, the surface of the water or the level of the transducer by entering a positive or negative offset so if I configure it with an offset of 50cm it then reads a depth from below the lowest part of my boat (yes, it's a motorboat) - it suits me as I know exactly how close the bottom is to hitting something but it gave an instructor a fright as he thought it was the total depth of water!

 

[Guest]

Re: Echo sounder

Virtually all digitals give this facility and the Target that I had was able to be offset .....

As to the spec of 0.8 - 180m, I regularly had readings below 0.8m .....

Actually thinking about the original posting ..... its says that the transducer fails when the boat heels .... alos that it is to one side of the keel ..... that implies that the keel extends below the transducer ... normal. So why the need to read to 0.1m or less ? Surely if the heel of the boat upsets the sounding, then it means its way above the base of the keel and probably not deep enough.

Finally if the coax has been cut .... then I wouldn't trust it at all .... has a length been taken out of it to remove slack cable ?, has it been joined properly to resume proper shielding etc. etc. etc. Iwould suggest that you borrow fropm a friend an uncut cable and transducer and try that before forking out any money !!!!!!

 

[Guest]

Re: transducer placement

Blue tack and chewing gum are other methods of temporarily fixing to check placement. Once best spot found ...... clean with the Oven Cleaner / fresh water regime and then glass the 'tube' in.

 

[rogerroger]

Sorry - I've always preferred echo sounders to read depth below the keel - so this is what I'm referring to, not actual water depth.

Roger Holden
www.first-magnitude.co.uk

 

[rogerroger]

Re: Echo sounder

Sorry - I should have stated that I'm talking about depth readings below the keel - I've set an offset on it so when I say it won't read below a meter I mean it won't read if there's 90cm below the keel for example.

Will I get a more accurate reading if I don't have an offset and always keep the keel in mind ?

The coax may or may not be the intended length - this is how I bought the boat - I'm sure the fix is not that good though.

Roger Holden
www.first-magnitude.co.uk

 

[rogerroger]

Re: transducer placement

I suppose the irony is that I should have done this when she was in the water !! She's just come out for winter lay-up!

Roger Holden
www.first-magnitude.co.uk

 

[ean_p]

Transducers in steel hulls....

Do any of the through hull transducers work on steel hulls, or is it necessary to cut a hole.......