Forward Sounder Tranducer

[joyce_boat]

Hello All, I am considering fitting a Forward Looking Sounder to my boat .The only minus is that the transucer has to be fitted through the boat hull. My boat has a double skin with buoyancy foam sandwiched between so I am reluctand to drill any holes.I have exchanged e-mails witha lady called Susan at Echomarine but she said that they do not supply a transome mount transducer. She also said that a few of their customers have fabricated the own brackets.Has anyone fitted this type of transducer to their boat transom? Many thanks.David

 

[DaveS]

You don't give the make of your boat, but all ETAPs and some Sadlers have the double skin / buoyant foam construction you describe. Is it one of those? On the face of it this would make the job a bit more involved, with scraping out 10 mm or so of foam from the sides of the hole and replacing with epoxy probably the easiest option. However...

You may well find that much of the hull underside is in fact solid layup and not foam sandwitch at all! I installed one of these last winter on my Etap 30 through what proved to be reassuringly solid 20 mm thick laminate. I wasn't certain what I'd find, so I drilled a small pilot hole first - to check the construction, and also as about the only way to get an accurate measurement of the hull thickness. The latter is important, since it quickly became obvious that after adding "wedges" to bring the hole's axis vertical the overall hole depth was quite a bit bigger than the length of the "Standard" skin fitting supplied. I therefore had to exchange this (and the transducer) for the considerably bigger "Professional" transducer and fitting - costing another £80 or so from memory.

I can see difficulties with the transom bracket idea. I tried to use the original transducer last summer on a temporary basis by tying it to a stick lowered over the side. This gave reasonable results with the boat stationary, but not under way: only 50 mm or so was immersed, but the force required to hold this in place at any speed above 1 knot or so was remarkably high. To "see" under the keel a transom bracket would have to be deep. The resulting drag force at hull speed would be large and would require substantial attachment arrangements: have a look at self steering gear systems and you'll see what I mean. The drag won't help performance either!

If you decide to go the conventional route (hole through the bottom, tan 10 deg X keel depth away from the side of the keel and aft of its leading edge) it will pay to be scrupulous about getting the boat levelled both fore / aft and sideways. Having a true plane to work from makes working out the angles for construction of the outside fairing far simpler. Having to compensate for significant offsets in both directions caused me much bad language!

Good luck ... it's a handy gadget once its in.

 

[FWB]

I think there is another minus......the forward txdr interferes with the depth txdr. So you have to switch off your depth sounder in order to use the forward thingy...or have they fixed this ??

 

[jfkal]

It depends on the frequency. Echo is using 200KHz. any existing sounder using the same frequency may interfere. On my boat they don't ))).

 

[jfkal]

Interphase makes Foward Looking Sonars with Transom transducer. However they are reasonably good as fishfinders only. Besides don't forget transom transducers are mainly for powerboats (bow comes out of the water and no keel obstructing the view).
If you want proper performance you need a throughhull transducer mounted at the recommended position. I agree that you may find the hull to be solid anyway at that position. If not, scrape the foam and fill with Epoxy. I recommend the professional transducer unless your hull is totally flat at the transducer location. Otherwise you may run out of thread on the standard whilst aligning the transducer.

 

[FlyingDutchman]

Excuse me, but what is a forward looking transducer used for?
The only thing I can think of is to detect underwater obstacles, but I would think that by the time it is detected you don't have time to stop the boat?

 

[AndyL]

It is to detect underwater obstacles - in sufficient time to stop! That's why it looks forward.

 

[FlyingDutchman]

Thanks Andy!

 

[DaveS]

In my case switching on the forward looking sonar mucks up the normal sounder, but the forward looker is unaffected by whether or not the normal sounder is switched on or not. I've put a switch beside the forward looking display and only use it for the small (but important!) periods when it is useful.