Like most folks ..I initially fixed my transducer to the F-Rib attached to a pole and clamped to the transom. I guess it worked in a fashion but it kept loosing the depth when I went on the plane. It was a pain to clamp as it had to be in the “sweet spot” where there was no aerated water flowing from the boat. In fact..I got fed up with it being a little fickle .. so seldom fitted it.
However I do like a transducer to indicate depth or sea bed features where a fish might feed so I decided to mount the transducer inside the F –Rib . Its called an “In hull transducer fitting” not to be confused with a “Through the Hull Transducer”..which is totally different. Its a method I used in my hardshell boats so knew it worked well before I installed it in the F Rib.
My transducer is just the standard and cheapest Lowrance fishfinder affair from the Elite3X which cost around £100 for the whole set. It now holds bottom at full steam ahead and I never need to worry about fitting it to the transom again.. its a permanent fixture inside the boat and does not interfere with its folding for transport.
Here is how its done.
Materials required
Sikaflex .. electric socket box .. fibreglass and a bottle of Baby oil or castor oil...and of course ..the transducer.
Cut or break the bottom out the electric socket box ..I used a dremel cutting disk to remove it
Cover the bottom edge of the electric socket box with a thick gasket of sikaflex. This is to glue it to the fibreglass hull and it needs to be a watertight (baby oil tight) seal. Note.. this method only works on single skin fibreglass hulls. If there is an air space between floor and hull ..it doesn’t work. The F-Rib works perfectly well. Sadly..SIBs with PVC bottoms are obviously not suitable.
Once the box and sikaflex are secured and cured to the hull .. sikaflex the transducer into the box ..by attaching its front face and its mounting points only to the box. Keep the transducer bottom off the bottom of the hull and avoid sukaflex getting under the transducer. Make sure the transducer signal will be pointing to the seabed so angle it in the box to match the hull slope. Let it cure ..then fix the box lid with another sikaflex seal ..ensuring the wire coming out the box lid is well sealed too.
Because the electric socket box is quite brittle.. I then fibre glassed everything to give additional strength to the box and extra strength in its seals.
A dab of paint to tidy things up a little.. fill the hole that I drilled in the lid with the baby oil (or castor oil) then seal it all in with a small fibre glass plug. The job is done.
The transducer works because its signal is transmitted and received through the oil..the hull..and the sea. It wont work if it the signal meets air. The reason a light oil is used is because the transducer is now a permanent fixture and the baby oil wont rot the wire insulation on the plastic transducer cover the way engine oil may.
This is the fishfinder end and I power it from a 12 volt battery in the box that holds a Samsung Tab and GPS plotter app. Its all kept under my bow dodger and is shower proof . All works very well and I never have to fiddle with clamping transducers again.
Hope this method may be of interest to some. Its not my idea.. its been on the go for quite a few years.. Im only passing it on.
