I run both a Humminbird 1197 on the helm (the biggest and best available from them when I bought it new in 2009) and a 2013 commercial EdgeTech 4125P towed system; I have used both systems extensively in a wide variety of water, both salt and fresh, shallow and deep, in lakes, rivers and the ocean off Massachusetts.
BUILDING A UNIT
- As to building one yes this can of course be done; now more than ever these Humminbird forums:
Unofficial Humminbird Side Image Forums www.sideimageforums.com - Index page and
http://sideimagingsoft.com
offer all the info one could want when trying to determine if this is the way to go;
- Home-built units have many limitations; one big one is software; both the Humminbird and the EdgeTech have software that allows me to nail a target’s
Latitude and Longitude to pinpoint it for a dive or, to make close sonar passes with either unit for better images and analysis;
But adding a towfish (and of course now cable) changes everything for a unit generally not designed to use a towfish.
In 2006 when I got my first Humminbird I tried to find software to drive it as I considered building a towfish but found nothing; perhaps this has changed but I never considered it after that.
That said, any commercial system (EdgeTech, Klein, MarineSonic etc.) and any non-commercial system (Humminbird, Lowrance, Raymarine etc.) all have this targeting capability and it is vital to have;
a) I don’t know if home-built towfish units can do this and considering you are looking for things you want to locate, how will you actually find them/dive them easily without capturing the Lat/Lon?;
The EdgeTech software (and other commercial units) allows me to factor in how much cable is in the water (called layback and absolutely critical to have), to change the Range of the sonar wave, to change palette colors, to run one or both frequencies at the same time, to take into account salt water, fresh water, speed-of-sound issues, integrating the data automatically with the GPS, setting my lane spacing using their “Coverage Mapper” for mowing the lawn as well as lane over-laps for 100%-200% bottom coverage and on and on; unless there is off-the-shelf software available to buy that can at least provide a minimum number of basic search functions, a homebuilt won’t do it for the serious searcher;
Your post had asked for some of the features you need most for what you want to do-start with what I just wrote above.
b) The deeper the water the more of a problem this will be with a home-built that doesn’t have the ability to capture coordinates; it could be such a big problem in the end you are wasting time and money going with a home-built because at some point you won’t find what you are looking for even though you have a SSS image that is really interesting; I’m a diver too so I know exactly how hard it can be to locate something on the bottom; even with a great set of coordinates if you have “black water” or deep, dark water, or the target is small, the challenge can be huge, depending on other variables also;
c) Powering a homebuilt may present problems as well because now you are sending lots of data over a cable-can the unit-presumably not designed for a towfish-handle it without crashing? You might need a generator, something else to factor in; there can be other electricity-related challenges I cannot get into here in detail because I am not qualified however I see the potential for a heck of a lot of questions to overcome with a home-built related to electronics; I really hope the Forums for home-builts can give you answers;
d) Unless you have a lot of knowledge about electricity etc. at some point the unit will likely fail-then what? To whom do you go for repair or diagnosis?;
e) If you go this route, Rudiger has it right-go for the largest display you can get;
f) As to problems lengthening the cable I do see issues; that’s why what you get from the factory for cable for a helm-mounted side scan sonar/SSS unit should never be cut but instead, curled up un-cut and stored safely; use the entire cable as it came from the factory;
However people who like this technology and have built their own towfish may have much better answers to this question and that’s where the Humminbird Forums could be of great help because if anyone has messed with cable lengths while building their own towfish, they have;
My advice, assuming you have the money, is to buy a commercial unit (new or used) so none of the points I made above (and that’s the SHORT LIST) will be something you have to deal with if you go commercial vs. home=built. Just too much trouble and time in my opinion to build one.
TOWFISH ADVANTAGES
If you visualize the sonar wave not as a sound wave but as a beam of light, you will understand the geometry involved in ensonifying things on the bottom with a towfish. One huge advantage a towed system vs. a transducer mounted on the hull has, is the ability to get the towfish closer to the bottom, thus generating very very important shadows. The things shadows can tell you is spectacular (technically it’s a loss of sonar data but we call them shadows because that’s what they look like).
The higher in the water column the transducer is, relative to depth, the worse the shadows get. The angle-of-attack sucks. At some point you will not be able to recognize a great target because the angle-of-attack of the sound wave has degraded so badly.
Test: Put a beer can on a table and shine a flashlight on it from say, a 45 degree angle and two feet away and see the shadow it produces. Then lower the flashlight to say, 12 inches off the table from two feet away. The shadow of the can is radically different-and better. This is the benefit you get from towing the transducer lower to the bottom. Getting close to the bottom is really really important.
My Humminbird 1197 works great in “shallow” water but as I get into deeper water it degrades badly for the reasons I just detailed. Of course this has nothing to do with the Humminbird itself, it just the way it is using any hull-mounted transducer regardless of the Brand of the unit.
To answer your question about at what point you would you would start to see benefits from using (any towfish), the answer is the benefits would be immediate and dramatic.
I love the EdgeTech I bought (great people and great products/www.edgetech.com) and I love the Humminbird (
www.humminbird.com).
But buying the EdgeTech towed system-a commercial system-opened a huge new world of exploration for me that has been a great experience that isn’t over yet.
I love the things I can do with a towed system as both a sonar owner/operator and a diver. But I am not a pro, just a hardcore amateur with this sonar technology.
If you have other questions, post them here. If you care to contact me directly, email me through this Forum privately and we can go from there off of the Forum. I’ll help you any way I can.
