PaulRainbow
Well-Known Member
How is that relevant to fitting a transom mount Garmin fishfinder transducer in hull ?
what silicone to use for fixing a transducer in hull??
- Thread starter lenten
- Start date
How is that relevant to fitting a transom mount Garmin fishfinder transducer in hull ?
salar
Well-Known Member
Simple mistake I expect. Some people mix up the definition thinking Through Hull means shoot the signal Through the hull, rather than sticking the transducer through the hull with a hole (which is what the NASA speed sensor is).
PaulRainbow
Well-Known Member
Quite possibly.
As you say, through hull means the transducer is mounted through the hull and it's OK to use a suitable silicone here.
In hull means the transducer is mounted inside the hull, although not all transducers can be mounted in hull. Those that can should not be stuck in with a bed of silicon, as some people here have described.
This subject comes up from time to time and i'm always told by a few people that i'm wrong and using silicone is fine. Airmar, the company that makes Garmin transducers, and just about every other companies transducers too, clearly state that silicone should not be used as it absorbs sound waves.
The article on your website that you inked to is perfectly OK, it's a variation on the age old method of fitting transducers in pieces of 4" drain pipe, but neater, IMO. Your older article that says using silicone s OK, is against Airmars explicit instruction not to use silicone.
Before Airmar started selling the in hull P79 style transducers their instructions were:
Clean hull.
Make a dam with plasticine.
Fill the dam with slow drying epoxy, deep enough for the epoxy to level out any hull deadrise.
When the epoxy is dry, but not cured, add a small amount of epoxy, fit the transducer with a twisting motion, to exclude air.
Allow to cure.
That wasn't necessarily a permanent fit, because the transducer face is smooth and flat it's possible to remove it by giving it a sharp knock (the transducer might not survive the knock, but the mounting pad can be re-used).
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kieron riley
Active Member
i really do not think that silicone has any use on a boat at tall and personally i would not use it in any circumstance EVER
salar
Well-Known Member
That's almost the exact method I previously published in my book (cross-referenced in the article). I have used that several times in previous boats. Epoxy does work but it is stuck forever and if you ever have to move the transducer you would probably either damage the transducer or the flocoat. Silicone may not be their preferred option but it does work, and there is a chance of getting it off afterwards. I have also had an Airmar P79 but it isn't a great transducer. My new method was inspired by seeing a mount sold for kayaks which is simply a piece of shaped, self-adhesive closed-cell foam - for £20!
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lenten
Well-Known Member
hi salar ---i originally copied your box method-----used florists foam and filled with baby oil------ was off colour for a couple of years and when i went to use it -----no oil-----when i removed box the 291 seemed to have a good seal to the hull----to the box and round the gland----but the rubber seal round the lid was slightly deformed-----could it have evaporated?-----any way the box is now removed and i am starting again -------silicone seems the quickest although i am intrigued by the vaseline method which seems even easier
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salar
Well-Known Member
I tend to agree. It is almost impossible to get anything to stick to something that has previously had silicone on it. In most cases there are better alternatives now, thanks to developments in sealant technology.
salar
Well-Known Member
How did you get on with florists foam? That isn’t so flexible and grippy as upholstery foam, but I guess it would do the job and easier to carve. I have always used water and antifreeze in all my mounts over the years with no problems, so I cant comment on baby oil. If the lid was on I would suspect a micro leak rather than evaporation but that is a guess. Baby oil is transparent so difficult to spot. Antifreeze has a dye so easy to spot spills or leaks. I I had a choice again I would still go for a box as preferred option, expoxy glue as second option and probably not silicone unless I was sure it would not interfere with the signal. Transducer technology has moved on a lot and may be a lot more sensitive now than it was.
Norman_E
Well-Known Member
Do a test first by sticking it down with Blu Tack. Use as thin a layer as possible and see if it works. I stuck a Navman fish finder transducer inside my hull with Blu Tack, to see if it worked. It did, and its still stuck with Blu Tack. If it works with BluTack you can clean it off and stick it with epoxy later.
Solent Sailor
Well-Known Member
I agonised for a while about delaying the relaunch of my boat (2 years back now) whilst I fitted a through hull transducer, or get it launched on schedule and go for a "bodged" in-hull fixing of a Raymarine CPT-S transducer (simple CHIRP). In the end, I opted for the latter (although I have since had it out again and fitted twin Raymarine RV-220 transducers (3D, downvision etc).
I simply bedded it down initially in sika 291i- squeeze a big blob onto the bilge floor and some onto the transducer - making sure no air bubbles, then push and twist it together (again, ensuring no air). Worked like a dream. I would have used silicone (because this is not a water barrier situation, so perfectly safe and reliable) but Sika is what I had to hand. Sika will be harder to remove should I ever want to remove the transducer.
In my research, AIRMAR (who make most transducers out there) noted that the thicker the hull, the better the signal. Counterintuitive, but notable for my boat which is quite heavily laid up.
There is no benefit to having one of the serious 1KW+ in-hull transducers in UK waters. They are only for when there is serious depth (1000m+).
I simply bedded it down initially in sika 291i- squeeze a big blob onto the bilge floor and some onto the transducer - making sure no air bubbles, then push and twist it together (again, ensuring no air). Worked like a dream. I would have used silicone (because this is not a water barrier situation, so perfectly safe and reliable) but Sika is what I had to hand. Sika will be harder to remove should I ever want to remove the transducer.
In my research, AIRMAR (who make most transducers out there) noted that the thicker the hull, the better the signal. Counterintuitive, but notable for my boat which is quite heavily laid up.
There is no benefit to having one of the serious 1KW+ in-hull transducers in UK waters. They are only for when there is serious depth (1000m+).
ghostlymoron
Well-Known Member
On my first boat I fitted all the deck fittings, solar panels etc with an unknown brand of silicone sealant. When I sold it 5yrs later all were watertight and intact. When I joined this forum, I learned the error if my ways.
Refueler
Well-Known Member
True ... but to me logic indicates that OP is asking to fix a sounder transducer inside hull ...
"what silicone to use for fixing a transducer in hull??"
To me the IN hull says it all ... ??
I don't think anyones daft enough to just fix a THROUGH hull with silicon without a secure physical method ??
There are various ways to fix a transducer in hull ... other than the tube method I prefer ..
Bathroom silicon
Sikaflex
Epoxy resin
Polyester resin
Thin double sided Car mirror repair tape
Refueler
Well-Known Member
Very neat ...
My way is to take the in-hull mount tube ... grind away one end to make it sit vertical on the surface.
Oven Cleaner sprayed to mount area .. leave for it to foam and get all that hard on crud and grime lifted ...
Wipe all cleaner away ... then fresh water wash the area to remove all traces of the cleaner.
Let it dry out ..
Apply epoxy to tube end you angled .... and press down in place .. (I use 5 min epoxy). Once set - I then mix up further epoxy and build up a fillet wall round the tube end to create a stronger joint. This not only strengthens the mount - but also seals the joint.
I am of old school and still use Castor Oil in my tubes ... but some people use water or even cooking oil.
Never had a tube leak or break away from that in many years use. I do not advise use of silicon or similar caulking 'gunk' as the water / oil in tube may cause it to fail ... Epoxy is basically resistant.
salar
Well-Known Member
The "Silicone or not" debate is because the transducer requires a medium to transmit signals between its face and the water. GRP and rotomoulded plastic with no voids is fine. GRP with a foam or hollow core is obviously not fine. Silicone, tape and anything else that could potentially reduce or obstruct the signal going through it will probably impede performance to some extent. Silicone will stick and create the physical bond, but I am no longer conviced it won't interfere with the signals of more sensitive modern devices.
Boathook
Well-Known Member
My airmar in hull transducer has antifreeze in the tube as per airmar instructions. Seems to work very well as far as I'm concerned.
Refueler
Well-Known Member
Rarely will a yottie require the soundings as in large vessels ... it was common practice in for example Palawan Passage to use soundings to indicate point of course change ... in the days before GPS .. watch for a contour change ...
Average yottie is interested in the range 0 to 50m I would suggest ... depths greater than that ? Only Blue Water totties maybe.
Less transmission due to mount ? Given that the form of signal hasn't really changed in decades since the E/S was first devised ... modern gear - is it that different ? I doubt it.
Refueler
Well-Known Member
Anti-freeze is a mix based on Glycol ..... and is a recc'd fluid to avoid freezing in the tube ...
salar
Well-Known Member
I agree, my first depth sounder was a Seafarer rotating LED and the principle of sending a ping and receiving an echo hasn’t changed. However, what is interpreted from that echo now is incredible so the nuances of the echo must be important and the variations so tiny that they are more likely to be muffled by an imperfect transmission medium like silicone. Silicone bedding will still give depth readings but you may no longer be able to pick up your string of mackerel feathers like you can from a water mounted transducer. If that matters!
Solent Sailor
Well-Known Member
I agonised about this myself for quite a while. In practice, the signal from my CPT-S was just as good bedded in Sikaflex as it would have been through-hull. I also know someone who siliconed their RV-200 to the inside of their hull and they have flawless performance. These are about as high tech as a transducer gets, so I think we are overthinking the problem somewhat.
lenten
Well-Known Member
i am going to try salars box method again -----when i prised the old box off i realised the 291 seal to the hull was perfect----the florist foam was intact but fell apart as i removed it ----i won t be using baby oil again
