Depth Sounder advice please.

Norman_E

Norman_E

Well-Known Member
Joined
15 Mar 2005
Messages
25,014
Location
East Sussex.
Visit site
Having suffered an instrument failure (due to the complexity of the all interfaced system on my yacht) I want to fit either a fish finder or a simple depth sounder, completely independent of the interfaced system. I need to be able to have one that uses a transducer fitted inside the hull as I don't want to lift out to fit a through hull. What does the panel of experts recommend as regards makes and types?
 
If you are looking for a cheap non-interfaced in-hull echo sounder. I recommand the Silva - you can even purchase an in-hull kit. I have one and am pretty happy with it. good value for money.
 
Most depth sounder transducers will work reasonably well inside the hull, provided there is a couplant present that will exclude an air gap between hull and transducer. The traditional way of doing this was to attach a tube full of oil inside the hull but sticking it on with Araldite will work about as well, with a lot less mess.
 
Did this easily on the last boat - Nasa target worked well. Inside a tube of plastic epoxied to the inside of the hull at a suitable spot. Transducer sat in a bath of olive oil from the galley.

Donald
 
It may be obvious, but in-hull transducer will only work if hull is solid glass - signal won't bounce through a cored hull, timber, or metal. I know it sounds simple, but one of our members couldn't get his new sounder to work, and he was trying to bounce it thru 10mm of PVC foam between glass skins ..... :-)
 
Sailing Today (May 06) have reviewed 12 fish finders and they reckoned as a budget buy the Eagle Cuba 128 (£89.95). Just checked and it can be mounted "on a bed of epoxy inside the hull"
 
just also bear in mind it need clear water.. ie not right behind the prop! Otherwise araldite seems fine. Some say dont use the quick set stuff, and dont whisk air into the glue when mixing it. But it is surprisingly runny, so its an idea to make a little ring of plastercine or something to stop it all running away. You dont need to bother with tubes full of castor oil etc... have a look though last years threads.. its a regular topic.
 
I would say it depends on the angle of the hull. If you have quite a steep angle then the tube and oil idea is good - you can cut the tube so it sits vertical. The 'more vertical' it is then the more accurate it will be in the long run.
 
I'd agree with nearly all the posts above.

Nearly all makes will do an "in-hull" fitting - it's the fitting you have to be wary of.

Angle as stated is a big concern. No turbulent water - even sitting right behind a keel can affect it. You need it to have about 3 foot of space away from an protuberances that are going to affect water flow and it needs to be as horizontal as is possible.

To close to a big keel and you can get echoing too.

Layering is also a problem, as stated above. It's the different densities of material that really screw it up.

Tony.
 
I used my Gosport Pund Shop's version of exterior No More Nails to mount my transponder in the corner of an under seat locker. It sits in a puddle of the goop, with another dollop holding it upright in the corner.

I can see three advantages to this. It's cheap, there's nothing to evaporate or leak away, and it's less final than araldite.

BTW, You can do everything right and find the transponder still doesn't work if you happen to have a tiny void in the layup in the wrong place. Put a blob of blue tack on the end of the transducer and try different places until you get a good signal.
 
Thanks to everyone. I fancy the cheap fish finder idea, to give more info than just depth. Hull is solid below water line and I have a good location as the through hull log and depth transducers sit on starboard side ahead of the keel, so I reckon that I could use mirror location on port side.
One further question. Will two depth sounders interfere with each other, particularly if on the same or close frequencies?
 
shouldn't interfere but I would avoid putting 2 the same frequency together. Most modern fishfinders you will be looking at are 200hz - older stuff was often 172hz I think.

I have run a 5 year old Lowrance at 172 (182?) mounted next to a DF unit running at both 50 and 200 simutaneously without any problems.

I have 3 transucers 'stuck' inside the hull, 1 araldite, 1 sikaflex and 1 plumbersmate epoxy - all give the same performance but as said search first (bluetack or a small ballon/plastic bag full of water) then avoid bubbles in the 'glue'.

The Eagle is a nice unit for the price.
 
I started from a similar position to yourself - I wanted an independent system and I used a cheap (Eagle) fishfinder with the transducer araldited to the inside of the hull on the centreline c. 0.3 m behind the keel and 0.6 m in front of the saildrive. Despite theoretical issues re. turbulance off keel etc. this in fact works very well - and it only loses the signal at a depth c. twice that of the original Stowe sounder with its through hull transducer! (I thought I might have problems given the Etap's "double hull" construction, but in fact the bit below the waterline is reassuringly thick solid laminate.)

On the subject of interference, the Eagle and the Stowe, both 200 kHz IIRC, seemed not to mind each other, but the transducers are mounted about 2 m apart. I have since fitted an Echopilot FLS (also 200 kHz) with its transducer mounted about 0.2 m from the Stowe's. With both of these switched on the FLS seems unaffected, but the Stowe display becomes meaningless. The Eagle and the FLS coexist happily. I would conclude from this that to avoid interference a sufficient separation distance between transducers is required, but I would not like to guess what the safe minimum should be. Applying simple geometry to the respective cone angles and water depth would suggest that my 2 m separation is inadequate - but reality says different!
 
Go for a fish-finder rather than sounder - gives you a much better picture of type of bottom and trends.
I recently chose a cheap Humminbird over an Eagle, as the screen was sharper - cost about £110 and is excellent. Checkout the internet stores and www.mesltd.co.uk in particular

Agree with all former comments re. fixing and having "clean" water to shoot into is vital.
 
You're probably right. In fact when I think about it properly my point about doing the geometry provides an argument against physical separation being the issue. Doh! /forums/images/graemlins/blush.gif

The Stowe unit's performance is really not at all impressive. Maybe it is down to modern equipment using more complex / advanced signal processing. The Stowe wind unit is a bit iffy too, and doesn't give NMEA or Seatalk output, so no easy way to generate a wind input to the Autohelm. I would almost* consider replacing with modern kit if I could only work out how to get in to the back of the bulkhead...

(* but not really - the thought of replacing bits that still work causes palpitations!)
 
You must log in or register to reply here.

Share this page

Top