[Public-list] hull thickness/transducers

[The Rochets]

Thank you for your comments, Mike, Glenn and Don.

  It sounds like usually the thickness of the hull may not be a big  
problem for in-hull transducers, beyond a certain amount of signal  
loss. Mike's setup confirms the under-the-berth as a location that  
works. I am intrigued by Don's setup--a transducer aiming forward at  
a low angle is definitely a good idea; it's nice to know how much  
water there is AHEAD of the boat. I am just not sure how much room  
there is under my V-berth, aft of the water tank, but I am definitely  
going to check it out. I am wondering whether your oil bath attempt  
did not work because the hull is thicker at that location, Don. From  
the hull plans, it looks like that would be right on top of the  
beginning of the keel, and quite a bit thicker.

Bernard  #608

> Mine is mounted on the port side, under the berth, in a box, and it  
> works
> fine. I forget the brand that I have, but it has never been a problem.
>
> Mike Lehman
> ~~~_/)_/)~~_/)~~~
>
> ******
>
> The inside tranducer I have on board works well out to 200 fathoms.  
> The ones I've had before all worked well in thicker hulls--even up  
> to 1" fishing boat--the only restriction in shooting thru a thicker  
> hull  is  a bit of signal loss--instead of reading the bottom at  
> 1200', maybe it will only read to 1000'.  Shouldn't be any problem  
> at shoal depths. 10 fathoms and beyond
>
> regards
>
> Glenn Brooks
> S/V Dolce
>
**********
> Depending on the size and placement of the forward water tank, there
> might be room in front of the panel under the vee-birth and aft of the
> tank. I have mounted a depth sounder there on the centre line. It  
> is not
> quite vertical, but about 11?  off,  aiming forward. That gives a  
> bit of
> distortion but not much and is equal for both tacks. I tried this
> sounder  in an oil bath first and it would not read through the  
> hull. I
> think it depends on who was working the day your hull was laid up  
> as to
> how thick it is and hulls tend to be at least 1/2" in most places.
> Epoxy and fairing the installation on the forward edge has made this
> just fine for water flow around it and it is waterproof. I have not  
> had
> a problem with slings catching the transducer on liftout with this and
> we do lift the boat every year. We do tie the straps though.
>     I used a 1/4 inch drill from the inside as a locator and drilled
> with a hole saw from the outside for the final position. It is a
> compromise between vertical and easily faired into the hull line.
>     Don't forget to calibrate the new instrument after installation to
> know how deep things really are when the bottom gets to be close to  
> the
> surface of the water! If you are off centre, then any heel will affect
> the reading for actual depth.
>     Having the transducer in a bath means that you need to have the
> fluid level in that box such that the transducer is always under the
> surface. This means there can be no leaks and that the "through hull"
> fitting has to be installed in the lid before the lid of the box is
> affixed. If you ever need to get the fitting out, it is a total
> deconstruction project that will leak fluid everywhere, and from what
> research I have done, oil, or at least fluids with viscosities greater
> than water are a better medium than water to transmit the signal. Your
> call though.
> Don # 528
>
> The Rochets wrote:
>> I  am interested in the Raymarine ST40 depth sounder. It comes as a
>> package with a thru-hull transducer, but I want to install it in a
>> waterbox, in-hull. Raymarine has assured me it's OK to use the
>> supplied thru-hull transducer as an in-hull as as long as the hull is
>> no thicker than 1/2". Do we know what the thickness of the hull is
>> under the cabin settees about 6" away from the center line (that's
>> where I am thinking of installing the transducer)?
>>
>> ...
>>
>> Thank you.
>>
>> Bernard
>> Sunswept #608
>>