Toilet Bowl Wax... In-Hull Transducer Mounting

[FlyboyTR]

Below is a short article I wrote for our local boating page regarding mounting transducers inside the hull. Just thought I would share.
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The installation of a transducer to the outside hull of a boat can bring on certain concerns. If your boat is in the water full-time, then hauling your boat becomes quite an expense to mount a transducer to the stern. There is another option...inside mounting!

I use a Garmin chart-plotter with XM Weather on all my boats. I have purchased 4 transducers, power cables and mounts so that our four boats can all enjoy the benefits of the single Garmin unit. I was ready to add number four to our Macgregor 26-S (classic) sailboat...but did not want to do an external mount of the TXD (transducer); there is basically no good place to mount it on the hull! So, now enters the internal mounting option!

I have mounted a number of TXD’s inside various boats, all with success. For me...since I don’t do DEEP water fishing... a depth sounder is sort of a misnomer... I need a shallow sounder! There is a bit of signal loss when shooting through a fiberglass hull, but for most units, this is not a problem unless you are fishing deep waters and need excellent bottom tracking of reefs, etc. ...again, in DEEP water! Different bottom machines have different power outputs for the TXD...the greater the output strength, the deeper it will read (accurately). For our type of fishing and pleasure boating...I’m not concerned about a structure in 100’ of water. I am, however, more concerned about how shallow the water is! ...just me...your expectations may be different.

I recently built a platform in the bottom of our Macgregor’s lazarette. This is so I would have a flat floor in that area, making it more usable. The platform left a protected void underneath between the platform and the hull. That is where I decided to mounted my transducer. Since I planned to use toilet bowl wax for mounting, which is soft...this protected area would be perfect!

Air gaps, bubbles, etc are the enemy. I have used silicone, conduit sealant, epoxy, 5200, wax and other things for mounting...all are okay to use. Some are just harder to work with and become permanent! Since my proposed mounting area is now protected (with the laz floor), I wanted something easier and since we may sell the What-Wind?...didn't want a permanent mount (like 5200, silicone or epoxy). Toilet bowl wax, while it may sound strange...actually works well, a little soft but easy to work with.

First...never operate a TXD if it is not in the water or properly mounted/bedded internally. This can cause a failure of the TXD. Some will fail quickly...some are not as sensitive. Even though we are mounting the TXC internally, do not operate it unless the boat is in the water! For initial testing to find the best mounting location you will need the boat in the water. Place the TXD in a zip lock bag filled with water (now you can turn the unit on!). Lay the bag against the inside of the hull (positioning the TXD as needed) until you find the best signal readout. If you have several location options this is a good thing to try. In my case I only had the one location...so no testing was done. Plus, our Mac was on the trailer...so I couldn’t test it.

The white finish coating in my laz was starting to flake off the hull so I basically scraped it all off in the mounting area so I had a nice place to work; free of potential air pockets. I cut the toilet bowl wax ring into four pieces and gently starting applying the first one to the bottom edge of the TXD, making sure there were no trapped air pockets. I added the second piece next to the first, slowly pushing the two together...again no trapped air. Finally the last piece was added and I then had a solid puck of wax on the bottom, about 5/8” thick; that also overhung on all sides. While it would be possible to slowly fuse the four pieces into one ball, rolling it in your hands and then applying it to the TXD...the possibility of air entrapment may be greater.

I had a little excess wax and I applied it to the fiberglass with a putty knife to press it into the existing weave...again, eliminating any possible air bubbles in the surface. The TXD is then put into place, starting on one side, pressing down and slowly rolling it into position...this is to prevent air entrapment. Once down, I made final adjustments so it was at the correct angle. You can't lift it...only press to adjust...keep this in mind when applying the wax thicker or thinner as needed. Since I was mounting it just slightly off center (to starboard), the port side of the TXD was slightly further away from the hull; so it required a little more wax. Once in place, use your fingers to smooth things out around the sides (which do not have to be completely covered...but make sure the lower 1/3 of the sides have wax against them. Again...the goal is to have ZERO air bubbles!

The wax will remain very soft...but won't melt, run or shift. We just completed a 5 day sailing trip, the Mississippi 110. It worked perfectly, just as I had expected! Deepest depth read was around 38 feet while in a channel. But for me...the important part was being able to read the depth while we were sailing in shallow waters near sandbars/shoals and while approaching our anchorage sites.

Some great things about this mounting method is that it is cheap, easy, removable and doesn’t require drilling holes in the hull or pulling the boat out of the water. Total cost was $3 for the wax ring and about 30 minutes labor...including wiring, removing and re-installing the floor board and playing with the wax.

If you are considering adding a depth sounder, bottom machine, chart-plotter, etc to your boat, this gives you one more option for mounting your TXD. This also works good on plastic boats like kayaks, etc.

[budgates]

Very nice write-up Flyboy. Thank you.

I considered mounting my transducer in wax but living in the desert the inside of the hull can reach temperatures high enough to either melt the wax or soften it enough that the transducer would slide out of place. With that in mind I decided to mount it with RTV silicone. A piece of dental floss embedded into the silicone that extended out both sides allowed me to easily saw through the RTV and remove the transducer when I sold the boat. It worked so well I used the same mounting for my new boat.

[Calin]

The Garmin in hull transducer comes with a cylinder like support. The bottom is fixed to the boat fiberglass and the transducer is at the top. An antifreeze liquid fills the gap between the hull and the transducer bottom. The inclosure is sealed to avoid evaporation.

[FlyboyTR]

Very nice write-up Flyboy. Thank you.

I considered mounting my transducer in wax but living in the desert the inside of the hull can reach temperatures high enough to either melt the wax or soften it enough that the transducer would slide out of place. With that in mind I decided to mount it with RTV silicone. A piece of dental floss embedded into the silicone that extended out both sides allowed me to easily saw through the RTV and remove the transducer when I sold the boat. It worked so well I used the same mounting for my new boat.

Bud,
Great idea using the dental floss! I don't know what the melting point of toilet bowl wax is. But...I have had it locked up in my car for hours during our scorching hot Lower Alabama summers...probably 140-150 degrees in the car and have never had one melt. However, you make a valid point.

There are numerous commercial options for internal mounting...but there is an additional expense involved...way more than the $3.00 for the cost of a wax ring!

[Sea Shadow]

I have mounted my Garmin transducer inside the hull, forward of the battery storage on the starboard side alongside the ballast channel. I used plumbers putty, a big wad pressed onto the inside of the hull and then pressed the transducer onto that. We have summer temperatures of 40+ degrees Celsius and it works great.