Fitting a depth-sounder transducer inside the hull

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MartinDreaming
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Fitting a depth-sounder transducer inside the hull

Post by MartinDreaming » Aug 4th, '18, 22:27

The day has finally come to replace my old Northstar fish finder. The LCD display will only light up for a few seconds, and then fade to nothing. I thought I could live without it, until I ran aground yesterday. Running aground on a trailer sailor is no big problem, because you can wind up the keel and continue or turn back. However, I thought I'd upgrade and keep the Admiral less worried about stories of groundings, and thought it would be nice to know if the bank ahead will keep rising or drop off. And a GPS (not phone) chart would be nice. So I bought a new Lowrance Hook 5.

Of course, the new gear cannot connect to the old speed wheel and transducer. It comes with its own transducer, which, so the bloke in the shop assured me, can be glued to the inside of the hull, just like my old 'puck' transducer. Incidentally, the new gear has no need of speed wheels, so the old speed wheel will get removed, and the hole filled.

Happily, my hull is solid GRP. So, there is no core to interfere with the sonics.

However, there are a couple of things I'd like to ask this forum, before committing to a 'permanent' fix. I've looked on-line, but have not got a clear answer yet.

* The bloke in the shop suggested using Sikaflex to glue the transducer to the hull. YouTube advises epoxy. One DIYer suggested silicon, but I like Ukuri's advice about never using silicon on a boat. I'd prefer a weaker bond, in case I ever need to get the thing off again. Something to hold it in place, but doesn't need a dentist drill and/or lump hammer to remove. The Sikaflex, or equivalent seems to be the way to go. The same shop sold me a tube of FixTech 190, so I'd prefer to use that. Checking on line, the most important thing is to ensure that there are no air bubbles between the transducer and hull. Getting the surfaces clean before fixing should improve performance and accuracy.

* The bilge in a sailing boat could be more of a vee than the motor boats most commonly seen on the YouTube videos. My current transducer is offset from the centre of the boat, on the port side about a foot from the keel. Does the transducer need to be horizontal port-starboard as well as bow-stern, like my old 'puck' transducer, which sits on its own wedge? If it does, I'd need to cast a new, small wedge of epoxy on the hull to get it level. However, that would mean that the hull would be thicker on the side nearer the keel, which might mess with the signal. Alternatively, I could mount it forward of the keel box, but if it is dead centre, it might have to shoot through whatever reinforcement has been buried where the two halves of the boat meet.
Austral 20 Mark 2 "Yakumin", Sail Number 108
http://theboattinkerer.blogspot.com.au/

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Tezza
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Re: Fitting a depth-sounder transducer inside the hull

Post by Tezza » Aug 4th, '18, 22:39

https://support.norcrossmarine.com/hc/e ... _v2916.pdf

I’ve purchased a glue in from Hawkeye and they sent me a through hull transducer in error .
Whilst waiting for the correct one I studied their manual above and I think it will answer your questions . Eg. Epoxy the transducer on ,if you want to take it out put a block of wood against it and give it a tap. . Sounds easy.
Sonata 6 Mango

INMA
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Re: Fitting a depth-sounder transducer inside the hull

Post by INMA » Aug 5th, '18, 09:57

I just used clear silicon.

I put a blob on the cleaned hull then set the transducer in the blob aimed forward of the keel.

Care making the blob in one go then checking the clear material for bubbles were the important things.
RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

Ukuri
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Re: Fitting a depth-sounder transducer inside the hull

Post by Ukuri » Aug 5th, '18, 11:15

Martin,
FixTech 190 is an excellent product. I used it to glue the rubber keel flaps onto Alyth and it worked spectacularly well. While retrieving during a strong Northerly the boat came up on the trailer at about a 30 deg heel and dragged the rubber up over the steel. Chunks of rubber and FixTech were ripped off but the bond remained intact.
First thing to remember when using FixTech is DON'T use any solvents like turps or thinners to clean the hull beforeapplying the FixTech. Use ONLY water or metho. Clean the hull with Metho, rough it up with 150 grit paper then clean it again with Metho and once the Metho has dried apply the FixTech and Bob's etc.
Secondly, as FixTech is a moisture cure product it is very slow to fully cure when applied as a thick bed. 2mm, 3mm,4mm is fine but once you start getting over about 6mm it takes an eternity to cure right through. 12mm, forget it! I thought I would make up some 19mm dia x 12mm bumpstops for the Landcruiser tailgate so I got a 100mm length of 19mm irrigation tube. I cut it lengthwise and filled it with FixTech and then taped it closed. It sat on the bench for a month and then I pulled off the tape hoping to remove a 19mm x 100mm length of "Rubber". It had cured in from the ends only about 10mm and all the rest was still soft (one of it's advantages over Sika products, it doesn't go off in the tube)!
You should be fine fixing it to the centreline of the hull. The hull would have been laid up in one piece, not two halves and joined down the centreline. If there is any timber stringers on the centreline they will have been glassed in afterwards and will be readily evident. If you cant see anything then it should be just solid glass.
You could put it behind the keel case. You don't really need to know the exact depth where you are but rather be able to tell if it's starting to shoal, and how quickly it's shoaling. Crab pot floats are always a sign that it is going to get shallower and hence a warning to be cautious. Note: Always give the area at the end of the pontoon at WMYC a wide berth. There is something there, reputedly a 1 cu mt concrete block that went astray during construction of the WMYC Marina.

Cheers etc.

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Pirate Pete
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Re: Fitting a depth-sounder transducer inside the hull

Post by Pirate Pete » Aug 5th, '18, 21:59

I just installed a Garmin EchoMAP 55DV unit last month and layed the transducer in a bed of sikaflex directly on the hull centreline, just in front of the keel housing. Works great.
Cheers,

Pete
Austral 24 - '250'

MartinDreaming
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Re: Fitting a depth-sounder transducer inside the hull

Post by MartinDreaming » Aug 6th, '18, 18:00

Ukuri, thanks for the advice.
Ukuri wrote:You could put it behind the keel case.
... but only if I could physically get there. My keel case runs all the way to a bulkhead under the cockpit sole. Behind the bulkhead is a sealed-in block of buoyancy foam. Behind that is another bulkhead, and behind that you'd need arms about 6 ft long to reach the hull from either of the aft berths. In front of the keelbox is much more accessible.

However, does the transducer need to be level? If it does, I could pour some epoxy onto the hull to form a level platform, and fix the transducer on top, after it has hardened.
Austral 20 Mark 2 "Yakumin", Sail Number 108
http://theboattinkerer.blogspot.com.au/

INMA
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Re: Fitting a depth-sounder transducer inside the hull

Post by INMA » Aug 6th, '18, 19:17

Just set it level in the dob of silicon aimed in front of the keel.
RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

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Slammin
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Re: Fitting a depth-sounder transducer inside the hull

Post by Slammin » Aug 7th, '18, 06:42

You can experiment with which spot or whatever with a big lump of blutack.

MartinDreaming
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Re: Fitting a depth-sounder transducer inside the hull

Post by MartinDreaming » Aug 15th, '18, 19:12

So, I decided to put the transducer the bilge in front of the keel. The GRP hull here is in a vee shape, but quite lumpy, so on Saturday I mixed up about 100ml of neat resin and poured it to form a "puddle" in the bilge. I'd heard that filler can interfere with the sonics, and the puddle would set to form a nice, flat, horizontal surface. Returned tSunday and the resin was mostly set, but still tacky, so I simply squished the flat bottom of depth sounder onto the flat surface to stick it down. This suites me as, hopefully, I won't need a dentist drill or a large hammer to loosen it in future, if I need to. Took the boat out today with some friends, and the thing appeared to work perfectly, giving me position, speed (over ground) and depth.

Incidentally, conditions in Moreton Bay were about as near perfect as you can get. Low swell, fresh, steady wind, warm but not hot. We were moving along nicely at about 5 to 5.5 knots. Nice sail in a well-behaved boat. Who could want more?
Austral 20 Mark 2 "Yakumin", Sail Number 108
http://theboattinkerer.blogspot.com.au/

Jaime
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Re: Fitting a depth-sounder transducer inside the hull

Post by Jaime » Aug 15th, '18, 21:00

Did the resin cure properly in the end? From memory it was quite cold last weekend and i wouldnt have thought it would have cured properly.

Last time i did some epoxying i have to have a bar heater running all night to get it to go off because the first lot i poured never did and i had to remove a lot of gooey resin to get to some hard stuff... not a fun job....
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Currently Slainte, soon to be....

rseydler
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Re: Fitting a depth-sounder transducer inside the hull

Post by rseydler » Aug 16th, '18, 08:52

I epoxy laminated a trimaran beam last weekend and it went off fine. I've never seen epoxy not go off unless the mix ratio was wrong, never eyeball your epoxy mix.

Jaime
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Re: Fitting a depth-sounder transducer inside the hull

Post by Jaime » Aug 16th, '18, 17:42

rseydler wrote:I epoxy laminated a trimaran beam last weekend and it went off fine. I've never seen epoxy not go off unless the mix ratio was wrong, never eyeball your epoxy mix.
I measure by weight, this was a couple months ago when it was pretty cold. Sat for a week or 2 before i gouged it out. Only about half set, im guessing it couldnt maintain the catalyzing temp needed to keep the reaction going. As soon as i heated it up it went off fine.

Going to let us in on pics of the new tri? Im guessing the mono sold pretty quickly. Only a week right?
Boomerang 20 DK #??
Currently Slainte, soon to be....

rseydler
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Re: Fitting a depth-sounder transducer inside the hull

Post by rseydler » Aug 16th, '18, 18:44

Another option if the object is portable is to throw a bunnings plastic drop sheet over it and stick it in the sun.

I'll start a thread about the tri when I have more to show than stem fittings and one beam.

Seabita sold, young guy living on it somewhere in brisbane on the water, keep and eye out for a seabita with pink trim :)

MartinDreaming
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Re: Fitting a depth-sounder transducer inside the hull

Post by MartinDreaming » Aug 25th, '18, 22:16

Depth sounder transducer fitted inside hull, below cabin sole. New 'bullet" style fitted on puddle of epoxy (now solid) in the centre of the boat, just forward of the keel box. Photo looking aft. Old, redundant "puck" style transducer to right, and a circle of epoxy for the previous transducer. Bilge pump hose on left.
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IMG_2879 (4).jpg
Austral 20 Mark 2 "Yakumin", Sail Number 108
http://theboattinkerer.blogspot.com.au/

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Tezza
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Re: Fitting a depth-sounder transducer inside the hull

Post by Tezza » Aug 25th, '18, 23:31

The glue in transducer finally arrived (same style as yours)last week together with a return label postage paid in US only for me to return the through hull they originally sent in error . Dammed if I’m going to pay post to the US .
I’ll have a go installing week after next.
Sonata 6 Mango

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