# Transducer Positioning



## Davey G (Jan 15, 2006)

Ive had my Fishfinder (Garmin FF120) for a few months now and have had a love hate relationship with it so far. I love it when its working properly (sometimes)  and hate it when its not (a lot of the time)... 

Anyway my main problem is that the readout seems to be picking up the hull thickness and giving a false depth reading of 0.1 or 0.2 metres instead of actual depth (see attached pic). The bottom shows clearly on the screen, but the problem lies when I go into depths more than 5 metres, the screen does not change to a deeper level (as the correct depth is not registering). It's wierd becasue approx 50% of the time on the water the readout is fine, but then it will go back to 0.1 metres again. Very frustrating! :evil:

Apparently the Tarpon kayaks are made of thicker plastic than other yaks, and with the keel of the yak also being slightly thicker plastic I thought this may be throwing off the reading somehow?? I'm wondering whether moving the transducer off to the side a little bit (the ducer currently is stuck centre hull of yak) might give a better readout?

I thought that putting it off to the side a bit would mean that its shooting through thinner plastic and not picking up the huill as easily???

Has anyone experienced any problems with mounting the transducer slightly offcentre? Or has anyone had a similar problem that they have overcome?

Note - I really want to keep the sikaflex setup and dont want to go the 'pipe and water' approach... Help!


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## Peril (Sep 5, 2005)

The recommended way to mount through-the-hull on a fibreglass boat is to cut a hole in the inner glass layer and the ply to fix the transducer to the outer glass layer. Maybe by a judicious thinning of the hull where you are mounter your transducer you can remove this unwanted detection of the hull.

Also, how much sikaflex did you use? Is the transducer pressed against the hull, with a thin layer of sikaflex, or is it sitting in a big gob of the stuff? Maybe less is more!

Before making any serious mods, perhaps you should try one of the in-hull removable steups, such as some pipe filled with water or vaseline to verify that it is the thick hull that is the problem.


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## Guest (Aug 2, 2006)

Heya Davey,

I have not had this problem with either of my Tarpon 120 sounder installs.
My Tarpons are fairly thick hulled as well but thats not to say that yours might be thicker again?.

I glued the transducers directly to the hull using Selleys Clear Araldite.

Is it possible that the sikaflex is too thick between the surface of the transducer and the plastic of the hull? This might make the transducer think the sikaflex is the body of water and the hull is the bottom?.


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## Davey G (Jan 15, 2006)

I originally had a big glob of sikaflex and thought that this was the problem so I removed it, re applied and thinned it out. The reading is better so it's 'sort of' working but not 100% of the time.

All I can think is that the transducer is picking up the hull as the bottom and I thought that the hull thickness may have been the problem.???

Dallas, is your transducer mounted in the centre of the hull or off to one side?

Pic attached of it 'working properly'


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## fisher (Aug 30, 2005)

Gday DaveyG - I've just come back from a marine shop where I was looking at a range of sounders for my kayak - to my surprise the salesman said that in hull transducers are not recommended for plastic - only fibreglass - maybe there is something in that?? it dented my enthusiasm a bit - hopefully you will get a good result - keep us informed. good luck


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## Peril (Sep 5, 2005)

fisher said:


> Gday DaveyG - I've just come back from a marine shop where I was looking at a range of sounders for my kayak - to my surprise the salesman said that in hull transducers are not recommended for plastic - only fibreglass - maybe there is something in that?? it dented my enthusiasm a bit - hopefully you will get a good result - keep us informed. good luck


Many of us are successfully using standard transducers in-hull in our yaks. Few salesmen would know of this. As far as I know, Dave is the only one having this sort of problem


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## Guest (Aug 2, 2006)

A plastic hull probably dulls the 'ping' a little I would say, but Davey is the first person I have encountered who has experienced a problem shooting thru their plastic hull.

If the problem is lessened since you reduced the amount of sikaflex then this might lend itself to my first theory......

My transducers are both mounted in the centre of the hull, they are placed inside the 6" centre hatch and forward as much as I could to keep them out of the way of the hatch bag.

This area of the hull is relatively flat so there isnt really a 'keel' where the plastic would be thicker. If you have placed your transducer more to the front or rear then there might be some thicker plastic in those areas perhaps.


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## Dodge (Oct 12, 2005)

Years ago I had a Furuno in a well of glycerine, sent the signal through a fibreglass hull, and have never seen one prepared as Dave suggested; glass and ply all got the glycerine method with all my mates.

The kayak is inside hull through silicone OK.

In my old cruiser the sounder was on the bottom of the boat, and being 500mm under the surface you added that to any depth reading.

In all through hull methods to get exact depth, if critical; add transducer to water level dimension to the reading


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## Sunhobie (Jun 22, 2006)

I've been siliconing transducers in plastic kayaks for years. The only time I have had trouble was when I used opaque silicon. Clear is definitely necessary. If the bond starts to deteriorate the readings go haywire also.
I doubt that the thickness of plastic is a problem. If you want to test that, remove the transducer and all silicon, place it in a plastic bag with a little water and seal it as best you can. Place the bag in the hull and give it a go. This is a good method to temporarily test transducer locations.


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## Sunhobie (Jun 22, 2006)

Forgot to mention that air in fibreglass sandwich layups makes in-hull installation unsuitable but plastic should not have a trapped air problem. The bag test should solve the problem


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## PhilipL (Apr 15, 2006)

Interesting post DaveyG. You may want to go wide on this one to see if anyone in the global community has an answer.

Sunhobie, I like your idea of a tranny in the bag. What's with the clear silicone over opaque?


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## Dodge (Oct 12, 2005)

PhilipL said:


> What's with the clear silicone over opaque?


I'm puzzled as well as other posts have mentioned white as well as black with success.

On the Cuda instal they only referred to a specific brand which is possibly USA as I've not seen it here


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## Peril (Sep 5, 2005)

Sound is colour blind. Its possible that opaque silicone carries sound differently to clear silicone. But it is highly unlikely. I used white sikaflex without problem.


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## Sunhobie (Jun 22, 2006)

I agree that sound should not differentiate, but having fitted many transducers, I have only struck a problem once with that particular type of opaque silicon. Perhaps the problem was due to some property other than the clarity of the goo! Maybe it had more trapped air in the mix? Epoxy glue is recommended, but it is difficult to mix it without introducing air bubbles and its non-flexibility could lead to separation when the plastic hull flexes.


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## Chillihilli (Sep 10, 2005)

I recently stuck my cuda tranny to the hull of the swing using sikaflex (white). It took 2 goes to get it right. The second time - I used 3 times the silicone compared to the first attempt. The first attempt resulted in no depth reading (actually it said 50M when I was launching in 2 ft of water) and continual screen recalibrating to try and get the depth. This presented itself as a series of vertical lines running across the screen about 1 inch apart.

The second time (see DIY section) I squished the transducer down as hard as I could. The sikaflex is really sticky so I just let it sit there and cure for a 1 week. It worked a treat.

To get a big wad of sikaflex I had to use a cartridge & caulking gun, as I couldn't squish out of the tube with my hands. It also comes out like mr. whippy, so I actually piled it up on a paint scraper about 3 inches high then trowelled it on the hull. I ended up with a blob about 4 inches in diameter and about 1.5 inches thick.

Good luck.


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## Davey G (Jan 15, 2006)

UPDATE....

Looks as though there's a problem with the FF itself. I went out again on Sunday arvo for a paddle. Had re-stuck the transducer again hoping for a better result, but same old shit..... raeding was telling me that the water was 0.1 metres when in fact it wasn't. AAAARRRGGGGH.

anyway, pulled up at the beach and ripped the transducer out from the sikaflex. paddled off and dropped the transducer over the side to see if that would make any difference, and it didn't. reading showed bottom contours etc as clear as day, but that bloody depth reading was still showing 0.1 metres... :x

oh well, at least I now know that it wasn't a problem with the way the transducer was stuck to the hull.

so, I've contacted Whitworths who I bought it from and the guy there was very helpful, has advised me to bring it in and they'll get Garmin to check it out and (hopefully) replace with a new (working) one or alternatively fix the bugger up!

will update on how this goes...could take a couple of weeks though.


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## JT (May 25, 2006)

Gidday Dave,

This is interesting indeed. I to have a Garmin FF120 and have experienced some issues with it that relate to sikaflex.

My first attempt was grossly over engineered and the transducer didn't work due to the fact that I had air bubbles between the hull and tranny despite ramming the thing down. The issue was that I had surrounded the transducer with a piece of shaped pool noodle.

I then got on the blower to Garmin and spoke to a chap named Ian (I think from memory). He was not only very knowledgeable but also incredibly helpful. He explained to me that the bulk of in hull transducers in stink boats are actually not placed into the hull but shoot through the hull. Most hulls in stinkies are double thickness I think with a layer or air in between. He explained that despite the need to shoot through multiple layers does not pose a problem in practice. I was very suprised to learn this as every salesman I had ever spoken to had never heard of placing a tranny in a yak let alone shooting through the hull of a stinky.

I then pulled it all out and used a blob of sikaflex which worked perfectly. Last weekend whilst fishing with Kraley my FF120 started to fail. The reading would fail to present the bottom or depth when I got past 6.7 meters. When I returned to a depth below that the reading would reappear. When I got in I found that the sikaflex and come unstuck and that the transducer was shooting through the sikaflex, a thin layer of air and still finding readings to 7 meters or so. It has since been re-sikaflexed and will be tested in anger this weekend.

My suggestion is that you call Garmin Marine Electronics and ask to speak to Ian or someone else knowledgable. Explain the symptoms and they will be able to tell you wether or not it is the fault of installation or you have a transducer problem. I had to work pretty hard to get past the gate keeper receptionist but once through I was given the opinion of a Garmin veteran.

The tranny in a plastic bag also sounds like a great idea but you might want to speak to Garmin first to see if the symptoms aren't representative of an occasionally found problem.

Hope it works out for you.

John


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## Davey G (Jan 15, 2006)

yeah thanks John.. I did actually send the transducer over the side of the yak directly into the water to check if it was a problem with the installation or the unit itself.

when the transducer was in the water the readings were still up the sh1t, so i can only assume that its an issue with the unit. Anyway, i took it down to whitworths yesterday, showed them some photos of the problem, explained the situation etc. It's now been sent off to Garmin for testing and hopefully a quick solution.

in the meantime, I'm without my 'underwater eyes' . Its amazing how you find out how much you rely on a FF once you don't have one!


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## JT (May 25, 2006)

Glad it's working out Dave. Whitworths must be just up the road from you. My post looks sort of illogical given your prior post. It came about as we were writing them at exactly the same time, so by the time I posted mine I discovered yours.

FF sure makes a huge difference.

JT


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## Davey G (Jan 15, 2006)

UPDATE... well after 3 weeks and 3 calls to Whitworths to ask 'Whats going on" I was starting to get a bit annoyed. Anyway today they have told me that Garmin are going to replace the unit and will be sending a new one out to Whitworths for me to collect - hopefully Friday...

So hopefully the replacement one will have no problems and i'll be back in action asap...fingers crossed!


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## YakAtak (Mar 13, 2006)

Great outcome Davey, some great praise of Garmin here, I think they'll get my dollars when it comes to buying.


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