Bow Thrusters

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Davydine

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Here is a problem that was discussed at the weekend and I wondered how you guys would get round the problem!

A fairly large long keel ketch needs a bow thruster fitting for easier handling in tight spaces. most sufficiently powerful bow thrusters on the market are 24Volts but the entire boat systems are 12 Volts. I guess the best bet is to have a dedicated bank of batteries in the bow for the thruster. What size batteries are needed and how do you wire the system to keep them charged!!

I look forward to your answers!

Many thanks

David
 
David

Yep, interesting problem. The most powerful 12v bow thruster appears to be the TX which produces 9hp. It is also all stainless including the prop which is why I chose it. The TX also has the benefit of a motor that lies along the thruster tunnel, unlike the vetus which protrudes at right angles and takes up more room.

I keep my domestic batteries up forward, (420 ah) which eliminates many of the problems and allows for very short runs to both windlass and bow thruster and I can switch in the engine bank (another 420 ah) when thruster is being used.

Depending on boat weight, windage and keel configuration (cut away forefoot?) will effect thrusters performance.

I can not provide you with wiring sizes but if I was doing this again I would look seriously at an hydraulic system. These are two component systems. The pump gets attached to your main engine and the pipes feed through to the motor which drives the thruster. Slightly more expensive but failsafe (providing you can get your engine started!)

Most important thing tho is that a thruster is an aid only. It will not push the bow upwind into a force 5 and neither will it push against a strong ebb/flood. What it does do is to allow you to berth your boat almost anywhere without having a heart attack and wrecking yours and others boats and it makes going in astern a dream, you just steer using the thruster.
 
Check with Vetus. They do bits and pieces for 12 to 24 volts for their thrusters. Also PBO back in March? issue did a bit about extra batteries for this and gave 2 names of companies that sell 12 to 12 volt chargers and possibly 12 to 24 volt chargers. My newly installed Vetus thruster allows me to turn the boat on the spot and hold the bows over moorings bouys. It did struggle yesterday in 30 knots of wind though!!
 
One solution is...

One solution I've seen, and it's quite elegant, is described on Colin Foster's site. It allows 24 volts for a thruster with only 1 extra battery and 1 switch, and it charges the extra battery too. Go to www.yandina.com/24VoltBattery.htm for a description and wiring diagram (note: the website address is case sensitive so you need cap V and B).
 
Installed a Vetus80kgf thruster over the winter and after all consideration kept the battery installation simple. I put in an Optima yellow top 60Ah battery very close to the thruster joined with a 110sq mm power cable. Good cable is expensive and I had to borrow a hydraulic crimper to make the joints.
The battery can deliver 560Amps for 80 seconds (ideal conditions). Vetus suggest 200Ah batteries that can deliver 500Amps for 90 seconds. Its much easier to charge the smaller Optima so the charging cable from the alternator is quite small- I reckoned at the time even if I got it wrong I would just put a second battery at the bow.
Have used the thruster for parking my long keeler in various marinas and so far so good!
 
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