Which thruster?

Canal Boat - - Back Cabin: Experts -

Q As my crew be­come less strong in han­dling a boat pole and my ma­noeu­vring skills de­te­ri­o­rate, I am con­sid­er­ing retro-fit­ting bow thrusters to our 52ft boat.

I am in­trigued that I have read lit­tle about hy­draulic pow­ered thrusters, yet elec­tric ones seem be­set with prob­lems of charg­ing, short­ing and only be­ing use­able in lim­ited bursts.

Any ad­vice? What sort of boat­yard should be en­trusted with the work? JOHN RICH, via email A TONY REPLIES: First en­sure it is phys­i­cally pos­si­ble to retro-fit a bow thruster, it re­quires a sub­stan­tial tube across the full width of the boat. This could ob­struct the cabin walk­way, cause prob­lems for gas bot­tle stowage, or mean fit­ting a smaller water tank.

A hy­draulic bow thruster will re­quire hy­draulic pipes (not easy to hide and messy if they burst) run­ning the length of the boat. It will also re­quire a means of driv­ing the hy­draulic pump which adds com­pli­ca­tions: a power take-off from the gear­box (if avail­able), belt drive from the en­gine (with the need for jockey wheels and ten­sion­ers), or an elec­tric pump (with the same prob­lems of lim­ited use as an elec­tric thruster, al­beit at least the bat­ter­ies will be close to the al­ter­na­tor).

Hy­draulic thrusters are not nec­es­sar­ily a bad idea – for ex­am­ple, if you al­ready have hy­draulic power for winches or some­thing sim­i­lar.

The main prob­lem with elec­tri­cal ones is ad­e­quate charg­ing be­cause of long ca­ble runs. If you keep the bow thruster bat­ter­ies very well charged, the charg­ing cur­rent flow­ing will be small, but once it starts dis­charg­ing you get into a vi­cious cir­cle where the high charg­ing cur­rent causes volt-drop, which in turn re­duces the charge and leads to even flat­ter bat­ter­ies. This can be avoided by in­stalling thick enough charg­ing ca­bles.

Al­ter­na­tively, if you have mains (eg, you use an in­verter 24/7 for a mains fridge, charg­ing from a ded­i­cated mains bat­tery charger at the bows min­imises prob­lems.

These mo­tors will wear their brushes: fol­low rec­om­mended ser­vice in­ter­vals to keep on top of wear, and clean brush dust out of the mo­tor as this can cause short­ing. Burned ca­bles or con­nec­tions can also be caused by us­ing the thruster with dis­charged bat­ter­ies: as a mo­tor slows be­low its de­sign speed, the cur­rent draw rises, so things can burn out.

Whichever yard you use, make sure they use very thick wall tube (or thin­ner tube with a wear in­sert around the im­peller) to pro­tect against cav­i­ta­tion pit­ting, and that they do not weld a mesh over the tube ends as it needs to be re­mov­able to black the in­side of the tube.

Retro-fit­ting a bow thruster can be done

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.