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The Sleipner SP285 48v dc bow thruster. The batteries are the old domestic bank moved to the bow. The control systems are mounted on the aft bulkhead close to the thruster with a remote joystick in the wheelhouse which can also operate the auto power of box with the emergency red button. |
We chose to angle the motor unit so that we could have a weedhatch so we can get at and maintain the twin propellors. The water level will be about 75mm below the weedhatch lid. |
We researched using the engine alternator to charge the battery bank at 24v but the long cable route meant that keeping the charging voltage right would be complicated and expensive. Eventually we decided to charge them using a 30A mains charger powered from the inverter, driven by the batteries which would be charged by the engine! The batteries also power the domestic water pressure system and pump out so would always be in use. When the boat is plugged into a shore supply the batteries are always kept topped up. |
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The thruster is 48v in use, but charges and soft starts at 24v. The grey box houses the relay that turns the batteries from 24v parallel to 48v series. |
Weed hatch lid removed to install the propellor anodes. There is a valve fitted to the lid to let air escape when Waterdog is floated. |
If we have to take the lid off while afloat, we can open the valve to see if water comes out and also put a small stick down through it to measure where the water level is. We could dump water, anchor and chain or ballast to lighten ship if needed. |
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The tube was stiffened at several points by welding brackets to the keelson and transverse ribs. This would stop any tendancy for movement and vibration. |
Just enough room to put on or remove the propellors, the anodes can be seen on either side. I had to order and fit 'fresh water' Manganese anodes as our home mooring is in the canal. This wasn't mentioned when I ordered the bow thruster so when it came with 'standard' zinc anodes we had to spend again and have a special delivery. |
The weedhatch lid also carried the piece of tube that was cut from the tube. The tabs on this help it fit snuggly in the rectangular hole. There should be no turbulance caused by the weedhatch opening. |
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The contra rotating composite propellors in quite a long tube. |
The new engine installed, aligned and on solid mounts. We chose white so we could see oil or diesel leaks. |
We had to move berths soon after coming out of dry dock so trialled the engine with 2 hours running while tied up just outside the dock. The engine started very willingly and roared with so much more responsiveness than the old engine. The wash behind us was also much more than we were used to and could also be because of the re-pitched propellor. Temperatures and pressures levelled out at the right values and big stupid grins appeared on our faces. We also tried the bow thruster whilst tied up and the thrust from it was very impressive, like a directional jet which you could feel shuvving the bow sideways. The tunnel, although long, must be smooth and well faired. We let go the ropes and managed to reverse half way up the dock against a 20kt wind and in perfect control, using the bow thruster to keep the bow lined up. We've never managed to go astern in a straight line before. The engine helped manoeuvring too, as it responded so quickly to a demand for a burst of power, ahead or astern. |
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We endured two rough days alongside in Alexandra dock with double ropes to hold us. |
New paint and bow names painted in. |
The new engine is a 6 cylinder 'Mermaid Mariner' based on a Ford Dovertech engine. It develops 135HP at 2600 revs but can do 122HP continuous at 2200 revs. The gearbox is a PRM500 driving the old 29" propellor that was re-pitched to 19" from 15". I will add some pictures later when I remember to take some but it has already changed Waterdog as we have the control to be more confident around other boats and to keep moving along if the wind or tide tries to stop us. |
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