Thru-hull transducer

[Jackdaw]

............... I can't believe the bull crap that these companies (in addition to this one) go through in mounting in-hull transducers when so many people on this site have simply slapped them on to the inside of the hull with epoxy, silicone, toilet wax rings, or anything else within reach which provides a bubble free base AND IT ^&*%#! WORKS.

Placing the transducer INSIDE the hull is a valid and effective DYI solution for depth sounders when done correctly.

However there are very good reasons why build builders do not, and should not.

1) Air bubbles in the laminate are a reality of fiberglass boat construction. Part of the trial and error of mounting inside the hull is checking that you got an area totally devoid of bubbles or voids. It takes only a very small void to impair a reading. That process takes time, and time is money for the factory.

2) Quality control. What if the first time use reads bad depth? What is at fault? Fixing that will cost the company time and money.

3) If the hull is cored, it will not work at all.

4) Installing a standard-size airmar transducer plug allows the transducer to be replaced, upgraded, etc.

5) The final install is stronger and more workman-like. Honestly, if I was going to throw big money at a new boat and saw the depth transducer sitting in a ring of toilet wax I would turn and run.

 

[Sailor_Jeff]

The thing is, transducers are directional, but only to a point. The signal spreads as it comes out. The the sound wave bounces off the ocean or lake bottom and the pings the transducer while it is in its listen mode. While we tend to think of a transducer in terms of a laser pointer, really, it's more like a flashlight.

True or not, I always felt having a transducer on the stern silly. Seems like it would only tell you "yep, you just ran aground". Instead, seems like having it in the front part of the boat would be wisest. Then it could tell you, warning your about to run aground.

Epoxy to hull? Need to change it later? A quick wrap with a hammer will shift most of them off. If it were to go bad. Unless you just go crazy with the epoxy....

 

[Sailor_Jeff]

To clarify, it has been my experience that a little bit off in your aiming is ok. A little bit. However, the boat healed to 30 degrees is, well, "at risk" if you depend solely on the depth finder. You should be situationally aware using good charts with depth. Perhaps have experience in the waters. And general caution.

Micro bubbles, those tiny bubbles in the hull or epoxy CAN disrupt the sonar signal. They spread it out making a wider beam and therefore shortening the range. Most of the time not a problem for simple sailboats. However, For fishing sonars with full imaging or military boats this is bad because it could lack the clarity to image things like fish, features on the bottom, enemy subs etc, And while for depth only rigs it may affect range on the deep-end generally it does not bother sail boaters that are primarily concerned with running aground. Most sailboats just want to know if something is in the upper 10 feet of water. Minor tiny bubbles in the epoxy has not ever stopped my depth finder working in shallow waters. However, my experience is limited, on all my boats I do not have imaging capability, just a number and alarm. And those beam spreading micro bubbles may actually help when I am healed a little. Just my opinion, I could be wrong.

 

[braol]

In the Navy we only really use the depth-finder (sonar) as a double-check against the chart and to confirm depth when anchoring, no one in their right mind would use it to "make sure" they don't run-aground. Just like SailorJeff said, that'd be sheer madness...just as mad as sailing at a speed that would really heel the boat while using your depth finder while sailing over a known shallow area that may or not be 'just deep enough'. I mean, who does that?

 

[Jackdaw]

Micro bubbles, those tiny bubbles in the hull or epoxy CAN disrupt the sonar signal. They spread it out making a wider beam and therefore shortening the range. Most of the time not a problem for simple sailboats. However, For fishing sonars with full imaging or military boats this is bad because it could lack the clarity to image things like fish, features on the bottom, enemy subs etc, And while for depth only rigs it may affect range on the deep-end generally it does not bother sail boaters that are primarily concerned with running aground. Most sailboats just want to know if something is in the upper 10 feet of water. Minor tiny bubbles in the epoxy has not ever stopped my depth finder working in shallow waters. However, my experience is limited, on all my boats I do not have imaging capability, just a number and alarm. And those beam spreading micro bubbles may actually help when I am healed a little. Just my opinion, I could be wrong.

This is not why this happens. Acoustic (sonar) waves encountering material with a radically different speed of sound do not penetrate, but are reflected back. The speed of sound in water/fiberglass is about 1500 meters/sec. In an air bubble, its 350 meters/sec. The sound is not bent, it is reflected right back. The depth system is design to report the first significant echo return as the bottom. If the void(s) are big enough, and it does not take much to make the depth sounder to read the voids as bottom and show zero feet. Or --- (infinite) if it really confused.

 

[Sailor_Jeff]

This is not why... If the void(s) are big enough, and it does not take much to make the depth sounder to read the voids as bottom and show zero feet. Or --- (infinite) if it really confused.

This could be so, however, on a simple depth meters like I have used, that only read 3 foot to a hundred foot, I just have not seen it happen. But perhaps it is possible. So, in consideration of Jackdaw's words, recommend after a new install on a boat with a hull epoxy job, sea trials (or lake trials) to confirm operation in known depth waters at various normal heal angles are probably a good idea. But yes, always use charts for bottom, and depth finder to confirm.

But, I am only relaying my personal experience and not offering a professional opinion, with epoxy'ed transducers on a fiberglass hull. I will defer to more educated professionals. But again and again I have been impressed with just how accurate simple depth finders are, even in crappy environments. Heck, I once laid one in the bottom underneath the V berth in the water there of a 22, placed a bag of sand on it and ran it all season without attaching it at all. It worked fine as long as it had some water in between it and the hull. If you have a dry boat, it won't work.

Years ago a depth finder alarm saved my bacon once at the edge of a marina, in my small Macgregor, (I learned later) there was and old underwater breakwater wall that was only partially removed for an expansion years before. I was creeping along and the beeeerrrp, went off and I went full reverse and stopped. Surface looked fine, but the depth finder told me something was under about 5 foot. My 6 foot keel would probably have hit it. It would have been a devastating embarrassment. I did not notice the buoy marking it. Possibly because being a young man I was watching the young lady with me a little too much. I learned something from that.

 

[smokey73]

Focusing the question on CHIRP and Downvision capability

Focusing the question a little more on the newer "high resolution" sonars like CHIRP and Downvision. Has anyone put one of these on a sailboat? The question I have what do you lose in water of say 25 feet or less with a in-hull mounted transducer. When you cruise an anchorage looking for a place to drop your hook, it would be nice to know if you're dropping it on top of an obstruction that could make your anchor hard to retrieve. Just one possible use (if its nearly free)

I am a former Navy OOD and I'm fairly familiar with my responsibility to not run aground. I AM NOT suggesting substituting this sonar for situational awareness or minding the charts. Its just that some of the deals on the new Chartplotters include this capability and the transom mounted transducer is not very expensive as an add on (as much for ge-wisbang - not really necessary). The transom mounted transducers even come in some of the kits.

Has anyone tried one of these tranducers either epoxied to the hull, in the wax set, or some other method?

 

[Kermit]

I have a transducer that is designed for the transom that is plumber's puttied inside the hull. It's not high resolution but it does find fish and the bottom quite well. Humminbird does not promise it'll will work this way. But it does for me.

Come up to Lake Murray sometime. We'll compare notes and go sailing!

 

[The Garbone]

Have mine in wax forward of the keel. Handy there and no problems.

One note. Went into a full marina for lunch at the restaurant the transient dock had fingers, tried to back in so we could step off on the dock but grounded on the rudder 2 feet short. Turned around and went in bow first and it read about 2 feet. Quite a bit of silt in the slip. Ok for powerboats, tried 3 different slips bow in using the sounder before finding a good one.

 

[Sailor_Jeff]

I have a transducer that is designed for the transom that is plumber's puttied inside the hull. It's not high resolution but it does find fish and the bottom quite well. Humminbird does not promise it'll will work this way. But it does for me. Come up to Lake Murray sometime. We'll compare notes and go sailing!

Is the lake Murray in South Carolina, Oklahoma, or San Diego?

 

[Kermit]

Is the lake Murray in South Carolina, Oklahoma, or San Diego?

South Carolina. Sorry, I keep forgetting there are at least two others.