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Discussion Starter · #1 ·
Decided to putter on the kayak today, and rebuilt the external transducer mount that I experimented with late last year. I'd mounted it to the rudder mount on my Manta Ray, so that the transducer sat actually down in the water, rather than the various inside-the-hull options. My goals for the rebuild were to add a breakaway to avoid damaging something in the event of scraping it on the bottom, to make it look nicer than the prototype, and to get pictures this time so Jeffo wouldn't give me a hard time about that. :D

The overall design is to mount a piece of 3/4" PVC to the kayak as a clip to hold a piece of 1/2" PVC, to which the transducer is mounted. The transducer cable is passed into the hull of the kayak through a hole I drilled in the top rear area of the tankwell, then passed fore to where the head is mounted. The cable pass-thru is secured with a rubber stopper.

For those who don't know the Manta Ray, the rudder mount consists of two brass sockets molded into the stern of the kayak. I marked the location of them by covering them with painter's tape and poking a hole with a screwdriver. This allowed me to transfer the location to my workpiece -- the 3/4" PVC. I used a nailset to mark the center of each hole, then drilled them out to match the diameter of the screws.



After drilling, I cut it to length (about a 30-degree angle on both ends), and cut a slice down the small end, to allow it to shape into something resembling the taco-style paddle clips. Then I heated it over my backpacking stove until the plastic became pliable, and let it cool around the half-inch. Then I went to work with my dremel to open the slot far enough for the half-inch to be inserted and removed thru the slot, to achieve the breakaway effect. I started with a cutting disk and then used a sanding drum. Finally, since the rudder screws are pan-head, I used a round etching tip to scratch away room for the corners of the screw heads.



I checked that the half-inch fit and went to work on the transducer arm. I fired up the stove again and heated the end of the half-inch, then crimped it in the bench vise so that it would fit inside the flanges on the transducer, where the transom-mount was designed to fit. I actually crimped it too tight the first time, and had to warm it back up to allow it to relax a bit. I checked the fit and drilled it for the stainless-steel bolt and nylock nut. Then I took a wood rasp and scratched out flat spots where the screw heads inside the breakaway sat -- glad I didn't throw away the tape earlier. This allowed it to sit inside the socket much more nicely.



On my prototype, I taped the transducer cable to the floor of the tankwell and ran it into the hull through the small hatch behind the seat. For this job, I wanted to run it in from the stern of the boat. I almost went through the top face, but then realized that entering the hull high at the aft would still put the hole above the waterline while protecting it from bumps and from water that might be standing on the flat top surface of the boat. I chose a 3/4" hole so that the transducer connector could pass easily -- 5/8" might have done for my Humminbird, but it would be tough to redrill it a little bigger, so I opted for the safer size. I found a rubber stopper that had a 13/16" upper diameter, drilled a hole to allow the cable to pass, and cut a slot to allow me to insert the cable. When squished into the hole, it sits nearly flat with the surface, so it's not likely that something will pull the stopper out. It might not be 100% waterproof, but it will certainly keep splashes out. (If that part of the boat is under any kind of water pressure for any length of time, I've got bigger problems than a 3/4" hole.)



A shot of spray paint and a little electrical tape to secure the cable, and it's done!

Now I just gotta replace my battery and I'll be all set.
Enjoy -- Lefty
 

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Discussion Starter · #3 ·
Thanks Guffey.
My first two implementations were in-hull, those of course don't affect the performance of the boat. I've known several to use the over-the-side mounts and have been happy with them, but that drag imbalance has always bothered me. It probably doesn't affect the performance of the boat enough that shifting your paddle an inch-and-a-half to one side won't solve, but it just never sat right with me.
Lefty
 

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You were wise to follow your gut and center it... Mine is only maybe 2" left of the transom's center and paddle shift does help when paddling flat water. The thing I didn't consider was how drag would affect it when I'm drifting/coasting - Even with just a little flow, the current will catch it like a sock and turn the boat... And heading upstream? That's a slow, miserable ride dude. Figure 3 or 4 strokes left for each stroke right. Very frustrating.

Here's why I think you've stumbled on a serious innovation... The "over the side" setups are easy enough to reach for the down-image and 2D units if drag gets to be a problem, just lift it up. That's probably why most guys don't complain much about drag with the liberator mounts and similar setups. Thing is, the new side-imaging transducers HAVE to be outside the hull, skimming the surface just BEHIND the boat for best performance (under the boat is asking for problems). They won't work properly any other way and there's no way to reach it back there - you're stuck with drag if you don't put it where you've got yours (DEAD CENTER). Considering what it costs to replace the SI 'ducer it oughtta be a break-away setup too.

Thumbs up Lefty!
 

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As an aside, consider sending a couple of shots of that to HB's R&D folks. They've got no outta-the-box solution for mounting the SI's transducer on a kayak - might get yourself a finder's fee or at least a little recognition.

Just a thought ;)
 

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Nice work, and great idea! My one question would be what do you do with the transducer when transporting the kayak (particularly upside down or sideways on a J-rack?)

I am currently using the through-hull setup on my Manta Ray, but I've always wondered if it affects the function of the transducer at all, or how much.
 

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Discussion Starter · #7 ·
That will be an upcoming test. I expect the mount will hold it in place during transport. It holds pretty firm top-to-bottom, especially after painting. It comes loose more easily as a result of front-to-back pressure.
 
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