In hull transducers?

[Solent Sailor]

Anyone got experience of choosing and installing one of these (for a Raymarine network, although doubt it makes much difference).

In the short time that we've had Bootlegger ashore, I have found it difficult to find a solution to fitting a transducer to its unique hull shape. A single RV-200 won't work because there isn't a flat enough area which isn't too close to the keel. A twin RV-212 set up might, if forward of the keel - but time has run out and the boat is relaunched today.

So, rather than wait 12mths for our next lift out, I'm thinking about an in-hull transducer instead. At the moment, we have eS97 (possibly 98, need to check) MFDs installed, but may add an Axiom 12 into the system soon. 3D isn't so important to us - more keen on good CHIRP/downvision results.


Any thoughts?

 

[rgarside]

Try:-
http://www.airmar.com/productinfo.html?category=MT&name=Marine Transducers

The P79 / P79S type of housing adjusts for a variety of deadrise angles.

 

[Mike k]

I have the P79, easy to install and ok as a back up but at next lift out get a thru hull

 

[simonfraser]

As long as there is no air inbetween the transducer and the hull it should work ok.
Blob of silicone or i can sell you some ‘special’ oil

 

[Cockaigne]

I have a NASA Clipper depth sounder with the transducer inside the hull in a plastic tube containing 'special' oil (castor oil?). It works perfectly.

 

[Solent Sailor]

Thanks. I don't think the P79 is man enough for the job. I'm looking at things like the M265 and larger 1-3kw jobs. It's quite a thick hull (best part of an inch or possibly more).

I want it to run a decent fishfinder set up, not just simple depth info.

 

[stuartwineberg]

Had a Garmin fishfinder. Mounted the transducer in engine bay in a cardboard well filled with silicone sealant . Just make sure it is mounted parallel to the water surface. Worked fine. Boat was a Hardy Mariner so seriously thick layup

 

[omega2]

thickness has no effect, it has just got to be "solid" i.e no air in the layup. so if you have a sandwich hull your snookered. No such thing as a fishfinder, just fish the differences!!

 

[emmalina]

Yup if you have a cored hull you need to chop through the first lay up and expose the outer skin ! Its doable but hard work. We have a solid hull and I use a P79 and also resined in a Dragonfly chirp transducer both work fine ! Threw out all my through hulls as points of weakness.. But thats just me

 

[salar]

Any waterproof box sealed to the hull can be used to mount a transducer in, as long as it is sitting in liquid. I used a junction box with the bottom cut out, and used foam to mount the transducer in but you could screw the transducer to the wall of the box if you with. Easier to see than explain: http://harley25refit.blogspot.com/2018/05/a-fish-finder-for-cockpit.html

 

[Solent Sailor]

Thanks. It's not cored, just an inch thick of serious GRP. Very solidly built boat!

 

[omega2]

In that case put the trans overboard and note the return echo, it should be optimum, then put the trans in a bag of water and try various places inside the hull ideally 2/3 rds back from bow, avoiding any known turbulent places i.e. strakes and fittings under water line, note the return echo, get it as good as you saw from the first dip, when this sweet spot is found then "flatten" the hull and fix the trans to it, either by a well or just sikofix, if the latter is used then squirm the trans into the fixative to evacuate any air.

 

[Solent Sailor]

I have a keel, protruding around 1ft-18inches below the hull for much of its length, so two-thirds back won't work as it will blanket the signal.

I'm going to have to go fore in front of the keel which is an always-submerged area.

 

[omega2]

I am talking anti bubble maker, the signal from the trans goes straight down, narrow at the the start and widening the deeper it goes to hit the bottom, that "keel" will not blind the return. look here.

http://www.airmartechnology.com/productinfo.html?category=MT&name=Marine Transducers

 

[Solent Sailor]

I am talking anti bubble maker, the signal from the trans goes straight down, narrow at the the start and widening the deeper it goes to hit the bottom, that "keel" will not blind the return.

Not what Raymarine's technical guys say, and they have a reason. The angle of the beam is 60 degrees so from the centre of the transducer it needs to have a clear field of view of at least 30 degrees right and left. With my hull shape (keel, horizontal flat section, steep curve up and the flattens out again) there is nowhere to put the transducer which is either correct in terms of deadrise or far enough away from the keel to give it an open view of the seabed. Best I could find on the 0 degree section was 70 degrees - far more than the 30 required.

 

[omega2]

Hence the water in the bag trick!! if you want military spec sonar then follow the Raymarine way, if you want to go fishing then try the practical way, in any case they do not FIND fish, they only give you an indication of where to fish. consider this, you "see" a shoal of fish, you slow down and then stop "drift" fish still there? great get the feathers down, not there then find them again, and repeat, you could spend all day "looking at the finder" and get nothing.

 

[Solent Sailor]

Hence the water in the bag trick!! if you want military spec sonar then follow the Raymarine way, if you want to go fishing then try the practical way, in any case they do not FIND fish, they only give you an indication of where to fish. consider this, you "see" a shoal of fish, you slow down and then stop "drift" fish still there? great get the feathers down, not there then find them again, and repeat, you could spend all day "looking at the finder" and get nothing.

Thanks Omega2. I've got quite a lot of experience of what sonar can do, thank you kindly. I haven't asked anyone how I can find more fish, I can do that perfectly well, especially if I can see a clear picture of the water column. I could carry on with the Garmin 160 that is already fitted if I just wanted a vague idea of what the bottom looks like, but I'd rather be able to take full advantage of the other expensive electronic kit on board.

 

[omega2]

Sorry you did ask for this,Anyone got experience of choosing and installing one of these (for a Raymarine network, although doubt it makes much difference).
Read more at http://www.ybw.com/forums/showthread.php?502620-In-hull-transducers#1fSuuQMjQC70t01s.99 and my reply was what I had found. No wish to tell you how to suck eggs.