Fitting A Bow Thruster

[C08]

Planning an installation and a few unexpected hitches are apparent.
1 Most thrusters do not appear to be water resistant so I will need to a pair (to match) of waterproof hatches. There are plenty of deck hatches suitable at a reasonable cost but the biggest is about 600x450mm wheras I would prefer about 650x550 to match the inner hole size.
2 The foredeck lockers drain and having sealed the deck hatch I also need to close the drain to ensure that in substantial seas the water level din the locker does not raise and flood the motor. Being sealed at the deck this should not be the case but it is possible to visualise the deck hatch being "popped" by the water pressure or the seal beaing eased and leaking water in.

So sealed at the top and a through hull shut off ok so no water ingress problems but what about temperature rise in the locker with the thruster burning its large number of amps or on a hot day. I would need a vent probably inside the boat .

Am I over thinking things or are these the sort of normal fitting problems that are to be expected and need to be planned for?

I will fit a dedicated battery close by and charged from the boat charging with its own isolator switch. Apart from the structural fitting of the tube, thruster, fuse, relay and control with a time delay is there anything else to think about?

 

[Talulah]

What boat are you fitting this to?
Normally the bow thruster is not as far forward as the foredeck locker as there is insufficient hull in the water. The thruster tube needs to be well below the water line.
Most boats have the thruster mounted under the forecabin berth.

 

[dunedin]

Depending on boat, may be worth fitting a retractable thruster. Some extra cost / complexity but much less drag - and more effective as when in use is deeper and further forward

 

[Resolution]

Threading the (heavy) cable from the boat battery charger up to the thruster battery can be a real problem.
Heat build up is also a factor, you should only use the thruster in short bursts.
Depth of immersion is critical, do check where other examples of your boat have had their's fitted.

 

[Fendant]

Have you looked at the Sleipner Exturn external bow thruster. Mine is very quiet and efficient. Installation can be doen in one day.
No shares in Sleipner Co. !

 

[C08]

Have you looked at the Sleipner Exturn external bow thruster. Mine is very quiet and efficient. Installation can be doen in one day.
No shares in Sleipner Co. !

!
Thanks for the suggestion - they look very good but not on my small budget

 

[Fendant]

My choice for the Exturn was based on the following reasons:
a) Efficient, as well below water line
b) Silent, you don't wake up you neighbours
c) Shortest Installation time with minimum changes inside the boat
d) Lowest cost installed
e) Shortest Installation time

 

[C08]

What boat are you fitting this to?
Normally the bow thruster is not as far forward as the foredeck locker as there is insufficient hull in the water. The thruster tube needs to be well below the water line.
Most boats have the thruster mounted under the forecabin berth.

It is an 8 M Catalac Catamaran and a good point thanks-yes I may be trying to get it too far forward. There is room at the front of the wet locker to port between the mini bulkhead and the heads thro hull fittings. I will have to measure up. It could go very nicely to starboard but that is SWMBO's hanging wardrobe locker which I would tamper with at severe risk to my life and limb. I will need to measure up carefully as the further back I get the more powerful the thruster will need to be and that is more cost and a bigger hole in the hull.

 

[macd]

My choice for the Exturn was based on the following reasons:
a) Efficient, as well below water line
b) Silent, you don't wake up you neighbours
c) Shortest Installation time with minimum changes inside the boat
d) Lowest cost installed
e) Shortest Installation time

May I add an 'f'? I've never seen it mentioned but the tunnel in a conventional thruster inevitably reduces buoyancy at the bow. (Mine, in the boat when I bought her, is mounted somewhat further aft than usual, so the tunnel is longer and the effect more pronounced.)

 

[prv]

It is an 8 M Catalac Catamaran and a good point thanks-yes I may be trying to get it too far forward. There is room at the front of the wet locker to port between the mini bulkhead and the heads thro hull fittings. I will have to measure up. It could go very nicely to starboard but that is SWMBO's hanging wardrobe locker which I would tamper with at severe risk to my life and limb. I will need to measure up carefully as the further back I get the more powerful the thruster will need to be and that is more cost and a bigger hole in the hull.

I'm a bit puzzled by this - you talk about it going "to port" or "to starboard", but surely it goes right across the boat and the motor part is in the middle? Or are you talking about the two hulls of your catamaran? I don't know catamarans - is it normal to fit a thruster in only one hull?

Pete

 

[Tranona]

I'm a bit puzzled by this - you talk about it going "to port" or "to starboard", but surely it goes right across the boat and the motor part is in the middle? Or are you talking about the two hulls of your catamaran? I don't know catamarans - is it normal to fit a thruster in only one hull?

Pete

Think thrusters are not common in a cat because by the time they get big enough to need one and have space to fit in narrow bows the boat is likely to have two engines so the value of a bow thruster is much less than on a long monohull.

Not sure fitting a bow thruster in one hull would be very effective - or as the OP is discovering is there room (either depth or width) in the hull.

 

[C08]

I'm a bit puzzled by this - you talk about it going "to port" or "to starboard", but surely it goes right across the boat and the motor part is in the middle? Or are you talking about the two hulls of your catamaran? I don't know catamarans - is it normal to fit a thruster in only one hull?

Pete

Thanks-yes in the port or starboard hull.

 

[Boathook]

It is an 8 M Catalac Catamaran and a good point thanks-yes I may be trying to get it too far forward. There is room at the front of the wet locker to port between the mini bulkhead and the heads thro hull fittings. I will have to measure up. It could go very nicely to starboard but that is SWMBO's hanging wardrobe locker which I would tamper with at severe risk to my life and limb. I will need to measure up carefully as the further back I get the more powerful the thruster will need to be and that is more cost and a bigger hole in the hull.

The bow thruster in my 9m Catalac is in the forward cabin starboard side. With hindsight I might of been able to get it in the forward hanging locker (internal to the boat) but it was getting difficult with depths in water etc. If SWMBO also want the BW she may have to give up locker space. My BW is a vetus 55kg model with a 150mm diameter tunnel. The wiring is also something to consider.

 

[C08]

The bow thruster in my 9m Catalac is in the forward cabin starboard side. With hindsight I might of been able to get it in the forward hanging locker (internal to the boat) but it was getting difficult with depths in water etc. If SWMBO also want the BW she may have to give up locker space. My BW is a vetus 55kg model with a 150mm diameter tunnel. The wiring is also something to consider.

.
Thanks for that info. Yes the Vetus 55kgf is the one I have in mind as it uses the 150mm tube where many others use a 185mm tube. I think it will go in the hanging locker to port and still leave some hanging space

 

[pvb]

I'd agree with Fendant, an external thruster would make a lot of sense on a catamaran. Cheaper to install, gets the thrust lower in the water (minimising problems with the adjacent hull).