[Public-List] Internal mounting of depth sounder??

[Gordon Laco]

Good morning Jonathan.

Mounting the transducer in an inside oil bath is a good idea.  That will resolve the turbulence issue the block may be causing, and will also relieve you of worry about the block being knocked off and a leak being created.  (I worry about that one myself).

Motor boat guides will tell you that you must position the transducer forward in order that it gives forewarning of running aground… but this is of course a lubbers tale and has no practical value.  What mounting forward WILL do is help ensure that the transducer impulses are sent out and received back through smoothly flowing water.  My transducer is mounted beneath the portside settee just because that was a convenient place to put it and running the coaxial cable was easy.  But when the yacht is on port tack, with the transducer on the windward side of the keel, it is possible that the impulses are sometimes in turbulence due to turbulence coming off the keel as the yacht makes leeway.  But in practical terms, I don’t worry about that because the boat would have to be making a heck of a lot of leeway for turbulence to affect the transducer there.   

The books will also say that the presence of the keel beside the transducer theoretically limits the cone of reception on that side, due to angles of heel swinging the keel in the way of the cone of the impulses… but in practical terms this has never been a problem in my own boat, whose transducer might be considered in the worst possible location with regard to the keel and turbulence.

So, by the book, the best place for an internally mounted transducer might be beneath the fore cabin floor board (if there’s enough clearance for it)  Practically, it works fine beneath the portside bunk, faired and blocked so it points straight down when the yacht is at rest.

The greatest real issue with regard to transducer placement is where you run the ‘ducers cable.  It must not be bundled with any wiring related to the engine or the electrical fields created by the ignition system (if it’s a gas engine) and the alternator will mess up the instrument’s performance.

How’s that for a short dissertation on transducers…   I sold marine electronics in my retail marine business days… 

Gordon Laco
426 Surprise





> On Feb 17, 2022, at 9:14 AM, Jonathan Bresler via Public-List <public-list at lists.alberg30.org> wrote:
> 
> Dear Albergers,
> 
> Currently the depth sounder on Constance is mounted through the hull on a
> fairing block.   A fairing block protrudes into the water steaming along
> the hull and causes turbulence.   Considering the idea of removing the
> fairing block and mounting the depth sounder inside the hull.
> 
> What are your thoughts on the internal mounting?    Pros?  Cons?
> 
> Second, the depth sounder is located to starboard in the under-settee area
> just aft the divider between the forward under-settee (there's a drawer
> forward) and aft under-settee areas.    Is that a good location?  Why not
> farther forward, perhaps and internal mounting in the hanging locker.
> 
> What are your thoughts on fore and aft relocation?
> 
> All the best,
> Jonathan
> -- 
> Jonathan M Bresler
> S/V Constance Alberg 30 #262
> Annapolis/Eastport MD
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