Adding sonar to your
I use sonar in my
tube. I have had sonar in it for years. On the very very rare occasion
I go out for a few minutes without it, I feel blinded and ineffective as
if I am fishing
with a broken rod, or with a hook with no bait on it.
Get ready to join the float tube navy with underwater eyes. You will be
amazed at what it will do for your overall understanding of what lies down there ... and your enjoyment of the sport
will be greatly enhanced.
Having an electronic sonar unit on board will
help you improve your fishing techniques by giving you more information
and guiding your presentations. You might not see fish, (sometimes you
will) but seeing the bottom where you are fishing allows you to fish
Very often you will be fishing a certain depth and catch fish. If you
have spot that the fish are taking in a limited depth range, use the
sonar to stay in the best water.
Fishfinder or Sonar?
The thing about sonar
on a float tube is that when you are fly fishing and spinning, you are
casting away from the tube, you do not expect to see the fish that you
catch. In shallow water not many fish will stay underneath. So we are
not fishfinding, we are looking at the bottom.
we actually want is:
In short, you figure out
a new water in 1/50th of the time with a float tube sonar. Whether you
continue to use it later is optional.
- a way to learn
the deeps, the shallows, and where the dropoffs are located. When
you know the location intimately, you fish those spots casting from
a little distance away, and catch fish on them.
- something to look
while the fish are not taking!
- a reading of
depth, and the ability to then fish there, counting the line down
until contact is made with the bottom. The advantage? You now know
precisely how deep you are fishing for a given number of seconds
countdown with that fly, that length leader, and that fly
line/backing combination. So if you plan to fish at 18' in 20' of
water, after testing, you can do exactly that.
- identification of
bottom hardness in various places.
- identification of
rough and smooth lakebed.
- while over deeper
water - see visible fish underneath, in front, to the side, and behind
(but still within the beam cone).
There are vertical fishing techniques for fish under the boat or tube,
and visible on a sonar unit. The main ones are
and drop shot fishing.
A quality sonar will let you watch the take below, a cheap one will not.
are the essential sonar features?
Each manufacturer has
a range of units, each unit has similarities and differences to the
others. There are however certain features that you absolutely need.
After you have these essentials, you can if you wish, add money to get
more features that are nice but optional.
The sonar unit should be: Compact and
convenient to fit on the
tube but not get in the way of fishing. Have a
power consumption such that a small light battery can run it for as long
as a fishing session lasts. Have a clear display screen on which depth and
structure are visible with adequate detail.
Temperature of water
Colour if possible.
GPS if possible.
Side scan if possible.
The upgrades are add-ons that increase the price! If they push the cost
too high so you delay buying a sonar, you are hurting your own catches.
better to remove a few add-ons off your "features wanted list" and get
the unit sooner.
It has to be affordable, so you buy it instead of thinking about buying
options tend to take your attention away from the necessaries. The
essential features your sonar unit should have
are: depth display ( figures), visual bottom chart display with detail
of texture, and water
surface temperature (figures). Look for a compact unit with these
If you pirk, fish dropshot style, or
vertically fish leadhead jigs for fish directly beneath, a higher
definition screen (more pixels) that shows individual fish will be
advantageous. To get the detail of seeing your lure beneath the boat, and the
location of fish relative to it, increase the power over 1000 watts to
about 2000 watts, and make sure the transducer is 20 degrees minimum
the cone is wide enough so the lure fishes in it and gets displayed for
you to see on screen.
Remember however that while fishing shallow water, you cast away from the tube to cover
undisturbed fish with a retrieved bait/fly/lure, you are fishing for
fish that will never appear on screen due to not being underneath the
transducer. Be honest: while lake fishing, how often do you hook fish in
deeper than 20 feet of water? Vertical fishing is not really practical
in under 25' much of the time, so seeing fish is not realistic, but
seeing baitfish shoals well that is another thing and worth a little
extra spending cash.
Most of the time while fishing from your float
tube, you will be fishing in water less than 20 feet deep. Rarely you
may venture out into the 30 - 50 feet range. This means that a sonar
unit does not need the same power requirement for instance as an ocean
fishing boat. As a result you do not need the most powerful sonar unit
for tubing, and this allows you to choose from inexpensive units with a
power rating between 600 and 2500 watts peak-to-peak. Staying between
600 and 1500 watts reduces the battery size required to power it up and
makes the tube easier to carry ready for launching. That 600 watts
figure is more a depth gauge however and won't show detail. The
1500 watts will show rocks and smooth, differentiate between
weeds and fish, and begin to let you know bottom hardness. A
2000 watts unit penetrates weeds far better.
Some brands with good
reputation for reliability are Lowrance, Humminbird, Eagle, Northstar,
Interphase. Their complexity, power and cost vary. Eagle are like
a Lowrance without the unit-to-unit information sharing features. Eagle
have a lower power rating than their comparable Lowrance version.
You will get longer out of a battery on Eagle, than a Lowrance, but the
Lowrance with it's greater power will show tinier details on screen if
that is what you want. Humminbird used to be less reliable than Eagle or
Lowrance but in recent years and newer units HB seem to have beaten that
problem. For size guidelines: a screen with a diagonal measurement
of 3 1/2" to 5" seems right on a tube. Humminbird and
Lowrance are the side looking makes, if you want that
feature. Lowrance Eagle and Northstar are the best and clearest
downlooking display at the moment, which is the fundamental feature.
Cheap units are just
that, cheap! They will disappoint you with their performance. Don't fall
for the marketing propaganda that says "costs half as much - just as
good as xxxx". The Smartcast is an example of a sonar that just about
works, but does not have good enough quality to tell you anything about
the bottom, just that it is there. A simple weighted plumb line is more
effective than these (it allows you to feel the bottom hardness) and
costs nothing. The Smartcast is a useful bottom depth device if you
don't plumb, and I notice that shore based bank anglers like them. But
by now you will realise that serious anglers, afloat on the water,
expect much more information than just the depth from a sonar unit. So recognise that there is a quality threshold in these
items, and don't "cut-price-yourself" into getting something unsuitable.
Guide to Choosing the Right Float Tube Sonar
Power of Unit:
If all you want is to see the bottom and know the depth 600watts
to 800watts will do fine.
If you want to see the bottom and fish in mid-water, but
weeds and fish will get confused sometimes, get an 800 watt to
1000 watt sonar unit.
If you want to see the bottom, what sort of bottom (hardness),
fish mid-water, fish near the bottom, and most of the time tell
the difference between weeds and fish 1500 watts and up does
this. A 1500 watt unit has sufficient power for all float tubing
A 3" screen only shows minimal information.
A 4" screen shows medium detail
A 5" screen gives you all you will ever need from a tube
The cost of units is more related to the screen size than the
power, but that figures in the cost too.
A sonar that uses AA or AAA size batteries is too weak and
toylike for meaningful service. Look at the
battery page for
portable power source suggestions.
exactly what you need, be honest with yourself in acknowledging
what you need it to do, and save up for the lowest that does it
properly. That way you won't have to trade up and buy twice.
anglers look at their sonar fishfinder and all they see is the depth.
But it tells much more if you can understand the way little things are
displayed by these units.
So it's a good idea to learn how to
interpret what appears on screen.
Here are three
excellent tutorials for you to read:
Lowrance Sonar Online Tutorial
Deciphering Sonar Charts by Luke Morris
Understanding, Using and Interpreting Depth Finders
Is colour worth a bit extra?
Does colour give you
advantages over black and white while fishing? The answer is - it
depends on how you fish.
The more you fish for species that swim in mid-water, like roach,
surface feeding trout, rudd ... the less colour is necessary. Any big
return in mid-water is a fish.
The more you fish for fish that live on the bottom, like bigger trout,
bream, pike, perch ... the more difficult it becomes to tell what is
bottom and weed, and fish. They get mixed up. Lots of practise is needed
to figure out a black and white bottom sonar chart, but you can
figure it out (with a good unit) because they are different shades of
grey. A colour chart plots softer items in one colour (weeds) more
solid items in another colour (fish) and the rocky bottom in another
different colour. You don't have shades of grey, you have different colours
helping your eyes to separate images apart from each other and recognise
Black and white
monochromatic screens do have two unique advantages over colour.
They cost less. They are easier to see when intense sunlight is shining
directly on the screen (in this situation) colour screens seem to go a
bit "gray" and the colour appears to fade.
Let your mode of use, and your budget decide.
If you are planning to tube in under 15' of water then due to the
relative shallowness of the water your sonar footprint will be small,
unless you get a wide angle transducer. The shallower, the less you will see.
is a cone shape, so the shallower you are floating in, the smaller the cone, the deeper
you go the
larger the cone.
In 10 feet with a 20 degree transducer your sonar beam "illuminates" a
circle of 3 1/2 feet diameter.
In 15 feet, you are scanning a circle of 5 1/2' diameter.
In 20 feet, you are scanning a circle of 7' diameter.
Say a 5' circle under you is disturbed by your presence, but you are
looking at an outer circle of lake bottom which goes 1' farther each
side of that 5' circle below.
The wider beam also takes in more "stuff" which increases
clutter. Note that the wider beam spots a structure feature at a greater
distance ahead while you are moving.
detail of fish, separate fish, separate weeds, and structure with clarity
is easier with a narrower angle xducer.
The narrower beam spots new items at a nearer distance to
under you while moving.
How wide is enough? It varies according to your taste.
From my tube. My preference is about 20 degrees. Shallow water
anglers should maybe think in terms of 40 degrees.
While tubing, much useful information is
coming from the sonar and a fishing map. Your eyes and the fish
(nibbles, takes) supply the rest of the information that goes into
making good decisions. But if you never take your eyes off the sonar
display you will miss out on a lot.
Here are some handy
"estimates" of the coverage footprint of the commonly available
sonar cone angles for the depths we mostly fish in:
: Cone diameter
10 degrees =
1/6 x the depth
20 degrees = 1/3 x the depth
30 degrees = 1/2 x the depth
45 degrees = 3/4 x the depth
60 degrees = same as the depth
90 degrees = 2 x the depth
GPS-Sonar Combo units
It can be near impossible
to locate a spot 3 metres wide when you're 600 metres out from the shore on a
featureless surface of water. The GPS sonar combo units solve these
difficulties and bring some amazing fishing techniques to your fishing
toolbox. Marine GPS units are different from handhelds, they have more
compatibility with computers and other units to exchange information. A
handheld GPS - while it gives location - might not have all the features
you need, unless it can "talk" with the sonar. These are covered under
"Making fishing maps"
Sidefinders & sidescans vs
finding" sonar can help locate fish holding
off the bottom near a shoreline. This is useful if you are casting towards the shoreline from a
position out in the lake. This would be a major help for fishing for
rudd in particular. They are also good for spotting trout patrolling
along the shallows looking for a meal. their bottom display is of lower
quality than other types.
Humminbird-Bottomline Fishing Buddy will provide this sort of information.
You can be finning along, "see" a couple of fish 30 or 40 feet
the side of the tube, turn and cast a fly out the approximate distance,
and get a quick take resulting in a hooked trout. With no sidefinder,
unless they make a rise (were you looking at the water or the
sonar?) would you know the fish was there? The Fishing Buddy units
are liable to also show other "stuff" that is not fish at the same time,
especially when looking into the shallows. So a little study at
For a flyfisher in shallow water,
vertical view and seeing
fish beneath the tube isn't so useful apart from knowing the depth and
water temperature. Flyfishing with floating line is lateral not vertical
so the features of side looking sonar units are attractive to fly fishing
You will naturally have a greater interest in side view sonars when you
cast and retrieve whether it's spinners, plastics, or flies that you tie
on the line.
This make the side scan structure view from Lowrance HDS and Humminbird
side imaging units more interesting to consider, but heed this expense
warning - side view works best on a big screen, and large screen units
cost a bundle!
Remember your own style of fishing when reading up on the sonar units
and coming to a decision. The extra features are nice but the essentials
are dictated by your own mode of use.
The transducer mount
Your transducer (xducer)
must be facing downwards, and held steady if the sonar is to show the
Try to get the handiest type of transducer when purchasing your sonar
unit. There are xducers designed to be glued inside a boat hull, sending
their signal through the hull, they look shoe-shape rather like a mini
travel clothes iron. Others types are designed to stick on the outside
of a boat like a limpet mine. They are vulnerable to being knocked by
rocks and damaged.
A third type of xducer is designed to bolt onto the transom (rear) of a
boat in front of the outboard motor - and this is the handiest type to
get for a float tube. The L-shaped transom mounting bracket included is
ideal for bolting onto a home made float tube mount.
"Skimmer" transducer is of this type and is very handy for mounting
sonar on a tube. It comes with mounting brackets that allow you to
secure it to an aluminium strip or tube, wood dowel, PVC, golf club handle or
old landing net handle or a section of broken fishing rod. Next position
it so as to have the sonar beam
pointing vertically down. Bungee cord is great for doing this, low
cost and easily available. Take a look at the xducer (right) on my float
tube. Once the tube is afloat I simply push it into a vertical position
ready for use.
& Chargers - Powering it up
Normally we are
looking for a source of 12 volts onboard our tube. The standard answer
is a sealed lead acid (SLA) 7 amp 12 volt battery. It has plenty of juice
to run a sonar continuously, without
worrying about running the battery down.
There is an improved version called
Gel Cell batteries.
these look the same as the lead acid, but the chemicals inside are in a
gel form and cannot spill and ruin your equipment.
These batteries like to be recharged
as soon as possible after use. So don't leave them for long in a
discharged (empty) state, because it shortens their life substantially.
Recharge with the correct trickle charger as soon as you return home. A
trickle charge for this size of battery is 700mAh (3/4
amps), and takes 10 hours
and camping shops sell them.
There is an alternative
option to the SLA. This is the smaller, more compact, lighter and faster
charging modellers RC battery. Not the kind you get in an electric car
with 6 or 7 individual cells in the pack. You need to get a 10 cell pack
which will have the desired 12 volt rating. Easier to carry, can be
recharged in 1/2 hour, smaller to fit in your tube pockets. What is the
catch? It will cost you more than the standard SLA.
For a full description
of the use of batteries in float tubes go here:
Power Afloat - Float Tube Batteries,
and Battery Alternatives