Boat bow and stern thrusters

I would like to put homemade bow and stern thrusters on by 28 foot boat. I plan to buy used trolling motors; cut handles off; mount to homemade aluminum brackets directed port-starboard.

Here is what I envision:

- 12 volt system

- An 8 position joy stick. Reference directions North South East West NE SE SW NW. For now N S are not used, in a future version I might mount a second motor on stern directed bow-stern and use them.

- One relay at bow and one at stern. Each relay takes two control lines and can switch positive or negative on the trolling motors for forward or reverse.

- An on/off toggle "reverse switch" which causes the thrusters to go in opposite directions to double up the turning force.

I would like the joystick to control the bow and stern thrusters as shown below:

West - both thrusters to port East - both thrusters to starboard NW - bow thruster to port SW - stern thruster to port NE - bow thruster to starboard SE - stern thruster to starboard

With reverse switch (RS) on: NW - bow thruster to port; stern thruster to starboard SW - stern thruster to port; bow thruster to starboard NE - bow thruster to starboard; stern thruster to port SE - stern thruster to starboard; bow thruster to port

Logic table Control Lines Joystick Bow Stern N S E W NW SW NE SE RS Port Starboard Port Starboard

1 0/1 0/0 0/0 0/0 0/0 1 0/1 0/0 0/0 0/0 0/0 1 0/1 1/1 0/0 1/1 0/0 1 0/1 0/0 1/1 0/0 1/1 1 0/1 1/1 0/0 0/0 0/1 1 0/1 0/0 0/1 1/1 0/0 1 0/1 0/0 1/1 0/1 0/0 1 0/1 0/1 0/0 0/0 1/1

As above there are nine input lines and four output lines. What is the simplest way to implement the control logic?

Thanks for reading. Mike

Reply to
rh5680
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Why bother with a reverse switch?

The simplest way to do this, assuming the joystick can carry enough current to actuate a relay, is to run a diode from the relevant joystick to the relevant relay for each "1" in your table, supply the joystick with 12 volts, and ground the relay coils on the other end. Some sort of RC snubber in the joystick may or may not be called for, to keep the inductive kick of the relays from damaging your diodes.

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www.wescottdesign.com
Reply to
Tim Wescott

Why not just two DPDT center-off toggle switches? No logic needed. That can do any combination of drives, and it would be intuitive and easy to get used to.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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Reply to
John Larkin

A typical joystick has 4 output lines (usually called forwards, back, left, right) mount it rotated 45 degrees. NW and NE switches control the bow thruster the SW and SE control the stern.

The reverse switch conects the opposite switches on the joystick, (use a DPST switch) If you want east and west to function as before it's a bit trickier.

there aren't, and don't.

assuming theses are brush motors the

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  \_(?)_
Reply to
Jasen Betts

Sorry, how many trolling motors? And which direction are they pointed? Are you going to be cruising around with a regular outboard motor too? (I might be afraid of breaking the props on the trolling motor.) Have you ever "driven" your boat with just the trolling motor? (PITA, in my experience.)

George H.

Reply to
George Herold

In theory it should work. It isn't like there's enough thrust there to horse a 48 footer around with impunity and you'd have plenty of time to change directions as the boat came up on the pier (whatever).

What would make me reconsider it would be the physical modifications to the boat. One assumes you haven't already got built-in, sealed, and reinforced tunnels for the thrusters. Installing that is a monumental undertaking IMO.

What will that do to your cruising speed? You can't just open a few holes in the hull and expect the hydrodynamic characteristics of the hull to remain the same.

This is a displacement hull? Sail, barge, houseboat, etc.(one hopes..)

Trolling motors are designed on the cheap. Immersed 24/7 might be death to the motors, so make them easy to change out and leave the mounting so you're not locked into only one size/brand.

I know one guy that buys cheap junkyard automobile ventilation or heater core motors and uses them as trolling motors and he says he comes out ahead if he only gets one fishing trip per motor. The motor is immersed in salt water and gets a spray down with WD-40 and may go two trips before it has to be replaced.

You may do better with something like those hull de-icer motor/props they are usually in a can filled with oil and designed to take a lot of abuse. (but don't provide a lot of thrust)

I don't know what your boat is worth and what emotional attachment you may have to it... but I'd get an opinion from a yard before I started hacking into the hull....

I paddle my kayak (I have a large sailboat too) on the Cape Fear and can see the barges they use. A utility pusher drives into a socket on the barge and connects to the thrusters built into the barge. When the barges are sitting empty I can look (can almost paddle the kayak through) the thruster tunnels. A hellovalot of engineering goes into those things. If it were me, I pay the extra bucks and get thrusters installed by a yard BUT ONLY IF THE HULL CHARACTERISTICS could work well with large holes and the turbulence that would cause.

They use hydraulic motors for commercial barge thrusters and that gives them lots of power and control and the motors are damn near bullet-proof without being built specifically for marine use. They look like ordinary hydraulic motors with a heavy coating of epoxy paint on them.

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