Transducer fix?

limeydal · 06 August 2006, 23:58

Getting really tired of the transom mount transducer on my RIB.

I had the bottom alarm set at 5ft to give me warning in the Bay if I was getting too shallow. Started churning mud the other day and the alarm hadnt even gone off

Seems no matter what I do, it either gets too much turbulance or "kicks up"the first time I jump a wave.
So read all the "extensive" posts on this subject and seems the only way to go is fix it inside the hull.
Problem is my sump has a void underneath it.
So pulled the bung and collar this afternoon and threw a lightstick with a string attached to it inside the hull.

Have about 16" from the transom to the first bulkhead.
So thinking about using a 4"hole saw to cut a hole in the bottom of the sump,to access the hull and fix the transducer in place.
I can seal the hole with a ABS deck plate with O ring seal to make it watertight.
Only tricky part I see is sealing the transducer wire in to avoid leaks;but silicone should cure that.
So has anyone done similar and if so did yiou hit any snags or do you see any issues in doing that ??
Getting frustrating having nice electronics and not being able to rely on it.
cheers Dal

Limey Linda · 07 August 2006, 00:58

Hi Dal.
Watch out. Trying to cut a 4 inch hole in GRP with a hand held drill is nigh on impossible and you could end up hurting yourself if you use a big enough power tool. Basically it cannot be done. Also consider that a decent 4 inch hole saw is going to cost you about 100 bucks. However you could use a jigsaw but ???? Is there any other place on your boat that you can easily access the outer hull? It does not have to be at the stern, and running a wire is easier than what you have planned.
regards, T.

limeydal · 07 August 2006, 01:50

Hi Limey,
unfortunately this is about the only place feasible

Deck pretty well sealed up and didnt want to risk hitting the wiring looms further forward. Also not sure of the bulkeads and strengthening ribs further forward, that I may hit.
Have a good set of hole saws(spent 15yrs in engineering Maint) and know what you mean about the difficulties (and torque) involved

Extremely slow speed and dead square to the workpiece

Have put this off for ages as couldnt see an easier option.( Might consider using a rototool with a round template to guide it smooth instead then.)
I was more concerned with making the wiring penetration waterproof.Any good methods?
cheers Limey

Limey Linda · 07 August 2006, 02:49

Roto tool sounds better . Sorry about the safety advice etc. you obviously know what you are doing. Silicone does not stick to GRP well. Suggest epoxy putty ( but that is kinda permanent) or poly adhesive such as one of the Liguid Nails products from Home depot. Make sure you provide a service loop in the cable below the plate. Maybe you can find a small enough gland fitting for the cable size ?????

Best of luck. Tony

CAH · 07 August 2006, 04:44

You are welcome to borrow my RotoZip tool, cheaper to borrow than purchase.

limeydal · 08 August 2006, 06:14

Thanks CAH,
but have one. Think I should own shares in Home Depot or so my wife says.
Cut the hole in today with the hole saw and went fine.Just took it nice and slow and frequently cleaned the teeth on the hole saw.Sealed the ply with epoxy resin and will leave to dry overnight before installing the trim ring.
The hull flattens at the transom and forms a nice surface to atach the transducer to.
Now ;silicone or Epoxy?? That is the question

cheers Dal

marknj · 08 August 2006, 13:49

Use a normal deck gland for the cable. You should have no problem with the hole saw, do it all the time

codprawn · 08 August 2006, 13:59

Too late to be of any use now but maybe it would have been easier to use a through hull transducer? You could have drilled a hole right through the hull from the outside to install it although you would still have to get at the inside of course. Through hull gives you better performance than a shoot through.

antiqueboy · 08 August 2006, 19:28

silicone now try it out it is the removeable. Epoxy if you are happy with position and results?

limeydal · 09 August 2006, 05:49

Antiqueboy,
agree with your logic

Cut the hole, and bought a through deck cable fitting for the wire.
However was going to be a pain to pull the wire back and get it through the gland.
So opted for the easy way out and cut a slot to the outside of the flange.Siliconed it in and then once the flange is in,will apply another build up around the wire of more silicone.
Transducer set in a thin layer of silicone and flange just placed on until everything sets up.
Flange takes a 4" screw in deck plate with O ring seal, so should be pretty watertight.
cheers Dal

jyasaki · 10 August 2006, 17:59

Sorry, picked this thread up late.

Rather than silicone, I'd go with something like 3M 4200. Better-lasting stuff than most silicones.

jky

limeydal · 11 August 2006, 00:27

Thanks, was looking at that stuff at Home depot and wasnt sure as hadn't used it before. If the transducer works well in this location will use that if and when the silicone fails.
cheers dal

limeydal · 11 August 2006, 03:59

All finished. Will try her out tommorow and see how it reads,
cheers Dal

limeydal · 13 August 2006, 18:13

works great

Think I will just stick with the silicone for now.
Thanks for all the tips,
cheers Dal