When I bought my catamaran its reverse was not functional, nor was the electric
start. Unfortunately neither was my budget, in fact it hasn’t been the same
since I got her. Propulsion was provided by an unreliable, single, two stroke outboard
giving her about the same turning radius of a big rig. With me scrambling back and
forth to start the motor every time she died, the
heavenly twins being a center cockpit, this gave me some decent exercise.
I learnt a few things in the scramble, one, plan several steps ahead coming into
an anchorage, two, keep that handbrake “anchor” handy and how to flip
a tit with the anchor tied to one of the bows.
Although it was fun, I decided to come up with a solution if I’m to be single
handed in a breeze. Problem is I needed something soon and on a budget. After having
looked at numerous options; twin diesel engines, twin hydraulic screws, steerablesillette leg, electric propulsion,
bow thrusters etc. I think
I finally found a budget solution for the docking and windage woes which will solve
the problem until I get a diesel in.
Well, of course, bow thrusters are the perfect solution, but they
are not cheap and installing them on a sail boat is major surgery, not to mention
the price tag. My custom solution is not the prettiest solution, granted, as with
my installation there will be visible motor mounts, but it can be installed without
major surgery and amateur DC electrical knowledge. They can be installed off the
stern in various configurations but my current steering configuration didn’t
allow for this. Two, 55lb (0.8HP),
trolling motors with the controls mounted at the helm. These can be purchased
relatively cheaply because they are mass produced. Total cost was $1500 for all
parts which is pretty damn good considering two vetus 55lb thrusters will set you
back $3750 before parts and installation, and we all know how much twin screws cost,
weather it’s hydraulic or twin diesels, we are looking at well over $10K.
In fairness those Vetus thrusters would probably perform better. You could probably
do better than this if you hunted around for a bargain on the motors. Once I found
all the parts, installation and testing took three days.
Installing the bow thrusters on the boat was pretty
easy. This being a sail boat there where considerations on placement
of the budget bow thrusters, see the next page for details.
Pontoon mounts, Cut some starboard ½” and ¼” strips. One
¼” overlapping the gunwale. Longer bolts where needed. Still need to
drill out and epoxy the cored deck. I chose to use pontoon mount because of the
boats layout. You may well be able to use the standard mounts.
The controller will need to be as close to the battery and motor as possible to
reduce the amount of wire needed as the size of wire needed to handle the amperage
draw is large and pricey. Dismantle the head and cut the pot (speed control) wires.
Unplug the motor wires.
The stock shafts where to short for my boat so I ordered longer ones. Cut the original
shafts off and chiseled out the remaining carbon fiber shaft. Painstaking work because
you need to take care not to damage the threads or wires. Was advised by the manufacturer
to heat up the casing to loosen the locktight and they would screw out but the carbon
shaft simply caught alight. So much chisel work was needed. These composite shafts
are really tough!
Extended the wires using 8AWG wire cause you have a longer shaft and need to reach
the plug socket. Drilled two 1 1/8” holes to install the plugs.
Mount each controller in line with the batteries and where the motor plug is to
be placed. This is to keep the wire run as short as possible and consequently lessen
the voltage drop or size of wire needed.
Install big 150A main fuse and two 60A fuses next to each controller.
Ran some small controller wires from the controllers to helm and soldered them where
the pot wires where cut on both the controller and pot.
Mounted the speed controls in original casings and use old shafts as mounting poles.
This gives me two variable speed controls at the helm.
Speed : 1.5 knots with both motors full forward (might have picked
up a bit more speed but I was short on space. This speed was reached in two boat
Turning : 90 degree turn done in 14 seconds. Without using rudders
or the main engine.
The initial test was disappointing, the amperage draw is only 84 and is, according
to the manufacturer meant to run at 100, 50 amps each, which is 0.67HP each, as
opposed to the published 0.8hp. According to prop calculations 100amps should push
her at 2.9 knots and 84 amps at 2.7 knots, so 1.5 is disappointing. Which leads
me to believe these, stock, wheedles props aren’t as efficient as they could
be. According to the manufacturer they are designed for around 4 knots. I have ordered
some larger 3 blade props which claim additional power. I’ll post an update
when they arrive. Turning ability however is reasonably good in calm. I tested this
without the use of the rudder or outboard and was able to navigate the tight marina
single handed with ease. She did turn on her axis. I noticed afterward I forgot
to pull the main prop out the water but I doubt this slowed it down much.
Coming up with the parts for the bow thrusters took the most time
Crossing the bridge, the bigger the wire the better, motor performance is dependent
on the voltage supplied. Initially I didn’t have large enough wire which cut
the performance by 40% upgrading the wire size across the bridge kicked it up to
around 84%. I used 4AWG. The batteries will need to handle this. I chose to use
the existing house bank. I have 2 X 6v Trojan T125’s (235AH total) considering
the Peukert factor this will give me 30 min to 50% DOD. This is more than enough
time for docking/anchoring, for occasional assistance with tacking and use as an
electric dagger board.
This has worked out reasonably well. It gives me the confidence knowing that I can
dock single handed under most but the worst conditions. It certainly doesn’t
hurt to have a little extra finer control. I would do it again.
Location of mounts I’ve mounted the motors off the gunwale
in the center, which is probably not the best place for this. As an afterthought
if the motors could be mounted so that, when deployed, they are positioned where
the twin screws would be i.e. in front of the rudders. This would give the benefit
of rudder wash and I assume better steering ability. With these mounted on the bow
or stern pointed perpendicular to the waterline, with the main engine running, I
think you could swing an aggressive turn.
Using contactors would definitely simplify the installation, fiddling
with those tiny controller wires was painstaking work. This will also leave a much
neater setup with only two small switches at the helm and you would improve on efficiency
having eliminated the controllers. The down side is you will then not have variable
control and I’m not sure if this will work yet, still to be tested.