Side Imaging Sonar on a kayak

As some of you know, I have been tinkering around with side imaging on a kayak. I have been thinking about this for a couple of years now and things started to take shape after some posts on AnglersNet (http://www.anglersnet.co.uk/forums/Hummi….der-t81232.html).

Well, I have had a crack at it and it’s not bad for a first attempt – so I thought I would share it with you all ;)

Side Imaging is a special type of sonar which looks out (up to 240 feet) either side of the transducer (up to 180 degree coverage) – it produces a display which is very detailed – showing actual features on the bottom of the sea/river. For this reason, the transducer has to have a clear line of sight 180 degrees from where it is installed – so you cannot mount an SI transducer inside a yak or on one side of the hull (say in the scupper) because one side of the lobe will be blocked by the bottom of the kayak. I tinkered with a couple of transducer locations – on the rudder and at the back – but finally settled on a location around midships for a number of reasons.

Before I launch into the detail of the installation – I also have to explain that one of the design drivers for the project was that the whole thing had to be easily & quickly removed from the yak and installed on another boat – this made a big difference to alot of the decisions.

1. Battery Installation

The SI unit I have draws quite alot of current – so you need a big battery and a way of changing it whilst at sea. This rules out the battery bag on the T15 – so a different approach was needed. I decided to make my own waterproof battery box and locate it where the fishfinder would normally go (under the sonar shield on the T15).

I won’t put in too many words, but the pictures should show you how I did everything. Used marine silicon to make a waterproof seal on the box – and put the inline fuse inside the box. The waterproof connector allows the battery to be swapped with another one (in another box) – this can be done easily from the seated position. The battery in the photo is a 12ah model.

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I have tested the box – and (thankfully :)) it is waterproof.

2. SI Control unit

One reason I was not worried by the battery taking up the space that the control unit would normally go in, was because I always thought that the sonar shield was too far away from the seat on the T15. So I wanted to move the control unit closer to the seat so that the buttons could be pressed more easily. A number of ideas were prototyped – the best involved mounting the bracket on the sonar shield itself. This meant it was closer to the seat and could also be hinged to allow access to the cables and battery box. It also has other advantages for the transducer as you will see later.

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Obviously, the sonar shield is not build to take the weight of the unit, so I created a leash just in case the whole thing gets ripped off :

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Once the sonar shield is down and the unit is deployed, the sonar shield webbing can be used to secure the whole thing and stop it from being moved by waves etc. The control unit can be easily removed from the bracket – and the sonar shield folds down as before without the control unit present.

3. GPS Module

My Si unit uses an external GPS receiver, Again – I wanted a solution whereby the module could be quickly removed. I wanted to put it just in front of the sonar shield, but it looked a bit low when I prototyped it, and it needed a wide angle of view to pick up all of the satellites. So I built up a base for it to stand proud, using some sandwich board.

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Lovely Jubbly ;D

4. Transducer Cradle

Had lots of thoughts and helpful discussions with other members about transducer location and installation – RAM mounts, Scotties, pulleys etc – decided on the humble BPS (Bog Pipe Special :D). It was cheap and simple and quick to knock up a prototype to see if it would work. 32mm BPS fits perfectly into the T15 front scuppers – so that swayed it for me. I also cut holes into the legs so that the water can still drain from (and into :() the yak. Also used a swinging arm (Preston Innovations off box keep net bracket) which grips the transducer arm (see next section). So the transducer can swing (under the pressure of the BPS seal) and move up and down using the bracket.

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The BPS cradle also has the added advantage that it fits under the control unit which also keeps it in place – a very simple/safe and compact solution.

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5. Transducer Arm

Originally, I was going to mount the transducer on the T15 rudder – but when I looked at it, it made the rudder very difficult to raise/lower (the SI transducer is quite big). I also wanted to be able to use the rudder without the drag of the transducer when paddling home fro example. I loved Bucketboy’s installation – but I needed to be able to raise/lower it from the seat and also wanted it to be portable (and not affected by the wake from the paddle). So I opted for an installation where I could easily reach it to raise/lower and where it would be out of the way of the paddle stroke. I made my own bracket to cut down the water resistance whilst paddling. Also incorporated a bank stick thread in the top of the bracket to use for either a camera or a rod holder – Brucie Bonus ;D

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The arm is a bit long at the moment – I need it to be long enough to reach below the keel of a dinghy when I go pike fishing, I am going pike fishing at Chew this week, so I will take it all with me and locate some crocs (that had put the kiss of death on it :D) – then cut the arm down to size.

Also added a paddle keeper button and some bungee to hold it all close to the kayak and out of the way when not deployed.

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6. Thanks/Credits and More…

As you can see the setup is functional, but the requirement for portability (and my dodgy DIY skills) has meant that it is not as elegant as some of the other mods I have seen.

I have fished for a very long time, and I am not daft enough to think that this is the be-all and end-all of fishing – but I do believe that it might give an angler a really useful (not to mention interesting) insight into what lurks below and hopefully might help me locate a few fish. If nothing else – I cannot wait to scan the locations where I have fished for years, and see what is actually down there ;D

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