MECHANICAL ENGINEERING

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Mechanical engineering has followed a traditional route to maintain simplicity.  

ENGINE AND PROPULSION

Hydraulic propulsion systems were considered but additional cost, lower efficiency and complexity overruled their use, so a traditional single engine installation was selected.

The engine is a Daewoo L136 8ltr 6 cylinder marine diesel.  It is naturally aspirated and rated for heavy duty continuous operation producing 160Hp at 2200rpm.  In industrial service it has proved to be an extremely efficient and reliable engine.  Many fishing vessels in UK waters have replaced ageing Gardners with this engine or a turbo derivative and their owners find that the engine is considerably more economical that their Gardners were.  The UK importer makes very little money from the sale of spares other than routine servicing items!  L136 Engine leaflet and power/torque curves.    Being a direct injection engine, it does not have glow plugs, so there is one less thing to go wrong and maintain.  The engine was impressively supplied with all ancilliaries - batteries, Morse throttle and cables, water inlet and kingston valve, toolkit with all special to engine spanners and tools, a years worth of servicing spares, spare gaskets, impeller, hoses and jubilee clips and even a pair of overalls with "Daewoo" on the back.  It was supplied by Watermota and  the package also included a 2 hour shore installation review at Triton before being KEI was launched by a Daewoo engineering representative prior to first use and then a sea trial.  Only after this is the installation signed off and the warranty commences.  Overall, the Daewoo package is a very good deal and having a commercial type back up is very reassuring.  In operation, the engine sounds great and makes all the right noises for a luxemotor.

    The gearbox is a TK250, similar in design and operation to a Twin Disc, and has a ratio of 2.5:1.  This ratio was chosen as a compromise between having a large propeller to maximise efficiency, the prop aperture available within reasonable draft constraints and the effect of increased propwalk with a larger prop.  With hindsight, it might have been worth specifying a left handed propeller instead of the standard right handed propeller and consequently changing the gearbox rotation.  The reason for this is the propwalk when going astern.  With a standard RH prop, the stern swings to port when going astern and more often than not, we found that berthing is starboard side to.  A LH prop would swing the stern towards the jetty when going astern.  In fact we discovered that KEI exhibits very little propwalk to port, and what there is is very easy to compensate for by inducing a little opposite swing using the rudder.

A trolling valve (akin to slipping the clutch in a car) was considered but not installed.  KEI maintains steerage way to well below a knot, in fact it is maintained when almost imperceptibly moving.

The engine is keel cooled and has a dry exhaust with exhaust outlet underneath the stern counter.  A Megapower silencer is fitted, which claims to improve engine efficiency and reduce fuel consumption.  It certainly seems to improve efficiency with reduced fuel consumption, but a silencer it is possibly not.  There is a delightful "bark" when engaging gear and it is particularly fruity on opening up the throttle - which scares Thames lock keepers and has kids shouting "do it again, mister".  At river/canal cruising speeds of 5kts or so, it is fine, but a high power it is rather noisy, but luckily the noise is left behind and below us at water level.  The silencing system has been revised and a Cowl TS40TR Residential silencer has been fitted and has made a remarkable difference - amazing for its small size.  These silencers are of a spiral design and are 1/3 of the size of an equivalent reactive hospital type silencer.  The engine also has connections to the central heating system using a Bowman oil heat exchanger, so that both heating and hot water is provided from the engine.  The now redundant connections from the engine to the calorifier will now be connected to the generator.  The calorifier has proved to be very efficient, retaining hot water for over 48 hours.  In Aug 08 whilst travelling down the Thames, I had an airlock in the keel cooling system, with the result that the engine started to smell very warm.  We managed to continue our journey by utilising the new heat exchanger arrangement.  By opening all the radiators in the vessel and running the central heating pump, main engine cooling was achieved by using the radiators.  A useful element of redundancy that I had not previously considered.

    The shaftline consists of a short 50mm diameter stainless steel tail shaft which has an outer cutlass bearing and an inner Deep Sea Seal.  The SS tail shaft terminates at a Centaflex thrust bearing and flexible rubber coupling.  There is a second flexible rubber coupling at the gearbox and between the two is a 2.4m Centaflex AGM 125mm diameter hollow tube shaft which does not require an intermediate support bearing. The Centaflex system was considerably cheaper than an equivalent Aquadrive/Python system and with no metal CV joints is quieter and does not require any lubrication. The aft engine room bulhead has double half inch thick neoprene shaft seals to prevent any fumes entering the aft cabin.  The engine is mounted on R&D  flexible mountings.    On the end of the shaft is a Willmans 4 blade 30 x 20 inch propeller and an extremely sharp rope cutter.  The propeller size was calculated using the tables in Dave Gerr's book "The Nature of Boats", and to Willmans' surprise, agreed with their computer calculated size.  I have also checked with Jooren propellers and they would recommend the same size or possibly increasing the pitch by an inch and going to 30 x 21 inch.

A single lever Morse cable throttle assembly controls the engine.  This has one significant drawback when the engine is running.  With the engine room soundproofing completed, there is now a faint low pitched hum and slight vibration in the wheelhouse.  After much searching and listening, the noise emanates from the Morse control lever housing and is engine noise travelling up the control cables.  This could have been completely avoided with the use of more expensive electronic engine controls, but other silencing and bushing options will be investigated.  It is as annoying as the sound of the ticking clock in a Rolls Royce car.

Fuel economy appears to be good.  On the Channel crossing running at 10% below maximum power, the Daewoo used 17 litres per hour.  The manufacturers figures at max power is 32 litres per hour.  Whilst travelling on canals and rivers at approx 5 kts it has worked out to be approx 3 - 5 litres per hour, although on some days it was difficult to ascertain any change on level on the fuel tank sight glass.

GENERATOR

I acquired a Fischer Panda 12kW genset.  It is a 3000 rpm machine, but nevertheless has an extremely effective acoustic cocoon and watercooling system so noise levels are very low.  It is also keel cooled and has a dry exhaust.  The generator cooling circuit will heat the second coil in the engine room calorifier.  A 3000 rpm generator does have advantages over a 1500 rpm one when it comes to sound attenuation.  Being 3000 rpm, the generated frequencies are higher and therefore easier to attenuate.  When running, the generator is barely audible from the wheelhouse above, however there was some exhaust resonance so a critical grade TXS15 Cowl silencer is fitted in the dry exhaust.  In the galley it is again barely audible, but the trickle of the fuel return back into the day tank can be heard!!

The alternator is wound for both single phase 240v and 3 phase 400v.  3 phase is used for the 1.5kW anchor winch motor and 5.5kW bow thruster and for the latter application a Hitachi SJ200 frequency inverter is also used.  It is also fitted with automatic remote starting which allows automatic starting in 3 phase mode when the bow thruster is selected and in single phase mode when the Chef requires it from the Galley when the oven is used.  I can also link it in to the Victron inverters to start automatically when the batteries need charging.  I would seriously consider another Fischer Panda if and when I need to replace it.

 STEERING

Steering is by a hydraulic system with bypass valve enabling use of an emergency manual tiller.  Equipment was supplied by Groveready in Cornwall.  The pump is a Triton 50 with 50cc per turn and the cylinder is a KS325 with a capacity of 800cc.  This gives 16 turns lock to lock over 70 - 0 - 70 degrees, or 8 turns over the normal range of 35 - 0 - 35 degrees.  The wheel is somewhat larger than recommended, so the pump shaft is supported by a UCF 205 flanged bearing.  An emergency tiller fits to the rudder stock through a hatch in the aft cabin.  I had much thought about rudders and whether to go for a "fishtail" rudder or stick with a plain NACA profile rudder.  The "fishtail" has some advantages in manoeuvrability and can enable very tight turns without the use of a bow thruster.  It also has a couple of disadvantages - they do not work that well astern and can be a little vague in the straight ahead position.  I would recommend Dave Gerr's "Thistle" rudder, essentially a fishtail design.  He has helpfully published all the design ratios and parameters in the open press - and so there is a considerable saving to be had.  Other designs include the original "Schilling" rudder and Alex van Baalen's "Miniturn" from Groveready.  With the NACA rudder and the 70 - 0 - 70 rudder angle, I can turn at rest in virtually the ship's length without using the bow thruster.

I decided very early on that I would like to make the steering wheel.  It is one of two items that connects the helmsman directly to the operation of a vessel - the other being the throttle lever.  I decided that a Morse type throttle level was too diffcult to make.  Building the wheel was quite a challenge and I ended up going about it in reverse - I found some materials before I really new how I was going to build it.  I had done some research and looked at a traditional spoked wheel and a cart wheel type of construction.  Whilst in the Marne region, we came across a small wood mill who specialised in veneers and his 1mm oak veneer was such a bargain that I could not walk away from it.  It came in approx 2m lengths and was 6 inches wide.  I did some rapid sums to work out how much I would need for a 1m diameter wheel with a 38mm thick rim and bought the appropriate number of strips.  Another wood mill provided oak staves for the spokes and the hub is an elm turning blank.  

Having got all the components, the next challenge was construction and I began to think of how I could laminate a circular rim.  I decided that I needed an internal former around which I would wrap the veneers like a snail shell spiral from the inside and use band clamps to hold each piece whilst gluing.  The alternative of using an external former was discarded.  The former was vexing me until I decided to cycle around the nearby industrial estate for inspiration.  And inspiration came very quickly - a wooden cable drum was the obvious solution.  Having acquired a 1.5m diameter drum and rolled it home, the diameter for the wheel was determined by the spacing of the nails holding the drum flange together.  The wheel circumference was accurately cut using a router mounted on an aluminium beam.  A flange was fitted to hold the laminated rim in place and both the drum edge and flange were covered in plastic sheet.  Resorcinol adhesive was used to lay up the veneers, I thought the dark red/brown colour of the glue would look good between the pale oak veneer strips.  The oak veneers were sliced into 2 inch wide strips, and the lay up started.  Strips were attached one at a time and it took roughly 45 mins from start of preping a strip to final tightening of the band clamp.  The rim was then left for a few hours for the adhesive to go off.  Resorcinol has the major advantage over epoxy in that equipment can be washed off with warm water.  In pratice I put on 2 strips a day - morning and evening.  Once the gluing was complete, I had a rim that was 2 inches thick and 38mm deep and the outside edges were a bit uneven.  The next task was to achive a 38x 38mm square section.  I mounted 2 biro refills 38mm apart in a piece of scrap wood and simply drew 2 parallel lines around the outside of the rim.  It was then just a matter of planing down to the lines and I had a square section rim.  The rim was rounded off using a 19 mm radius router - outside to make a half circle and on the inside just the edges removing to leave a flat land for the spokes.  After routing and sanding the rim was complete - and the difference between the 4 diameters where the spokes would mount was less than 0.25mm - so almost a circle.

The hub and spokes were turned on a Black and Decker drill powered lathe.  The hub at 150mm diameter was right on the limit of the lathe's capacity, but it worked.  8 stepped sockets were cut into the hub and the centre opened out to take a hub mounting.  This was turned from brass to match the helm pump shaft dimensions.  The spokes inner ends fitted tightly into the hub and their outer ends were an interference fit on the inside of the rim and secured with long SS screws through the rim.  Epoxy was used to fix the inner ends.

A final sand and a couple of coats of varnish and the wheel was complete.  I had taken about 80 hours, so completely uneconomic to make commercially but an enjoyable challenge.  In use it is a delight - has a meaty grip and has just the right weight to be able to spin the wheel quickly when needed but without over torquing the helm pump internals.

I also decided that rudder indicator would not be the usual little dial from Vetus or VDO - I consider them to be completely overpriced for what they are.  Following an article seen in one of the boating mags, I decided to use a series of magnetic switches mounted underneath the tiller arm operated by a magnet on the ram/arm securing bolt.  As each switch operated a corresponding 12v LED light would light up on the dashboard.  There are 21 magnetic switches - 10 each side and midships and dashboard space determined that each light represents 7 degrees.  6 core alarm cable is used to provide the individual signals from the magnetic switches to the LEDs.  The distance between the magnet and mag switches is such that at if the magnet and switch is exactly lined up, then only one LED lights up.  If slightly off, then a second LED lights.  Again, a fun thing to do and something different.

BALLAST

After much deliberation and assessment of costs, I decided to rely on water and fuel ballast in the various tanks for the trip back to UK.  For some reason ballast in the Netherlands was unduly expensive.  In UK I looked at a number of options - concrete, asphalt, lead, steel bar and steel punchings.  In the end I went for 10 tons of steel punchings and was pleasantly surprised to discover that they were galvanised.  The punchings were shoveled into double polypropylene bags (flood defence type) with approx 25kg per bag.  Waxoyl was also sprayed into each bag for rust prevention.  Most were slightly over 25kg and we moved 396 bags into the bilges in a day and a half.  Inside the bilges, the bags were laid onto hardwood decking tiles to maintain an air gap underneath the bags.  This was impractical in the forepeak due to the sloping hull section, so a thick coating of "anti roest vet" was applied.  To get under Osney Bridge, we needed additional temporary ballast and 22 x 200 litre drums were filled with water in the saloon area.  This achieved the required sinkage and we just got under the bridge - the stem clearance was the thickness of the Oxford Blue paint on the underside of the bridge beams - and this is now on the stem.

BOWTHRUSTER

A Silette Sonic sail drive leg, another virtually new/unused boat jumble bargain at 100, was fitted into a 300mm diameter tube and has a 3 blade CJR kaplan BT prop.  The power system is now installed:  a 5.5kW 400v 4 pole 1450rpm AC motor.  Drive for this is via a 2 inch wide timing belt which has the advantage over a chain drive in that it does not require lubrication.  A high efficiency and high power factor motor was selected and this will be controlled by a Hitachi SJ200 Frequency Inverter.  This was chosen after much thought and discussion on whether just to have motor compensation by capacitors to improve the power factor to as close as 1 as possible, or just use a "soft starter".  One advantage of using the SJ200 is that the motor speed can be controlled to match the propeller - which is a bit of an unknown.  I  felt that 1400 rpm was the maximum speed that should be used and this was reinforced with a similar powered BT with a small prop running at 2900 rpm.   If necessary the frequency can be increased to 60Hz, giving a useful speed increase up to approx 1750 rpm from the normal 50Hz speed of 1450 rpm and overall power increase up to 9.5kW.  I could also control the speed from the helm position and indeed change the prop speed by changing the pulley gearing.  BT motor is powered by the generator which will start automatically in 3 phase mode when the BT is switched on.  In the end a 24v system was rejected as yet another set of batteries would need looking after.  In fact we have managed pretty well without a bow thruster, even when manoeuvring in some pretty tight situations, and I think we only really need one in windy/strong stream conditions.  When stationary or almost stationary, the bow is simply moved to port or starboard with only the briefest of touches of ahead throttle and a reasonable amount of wheel over.

The Bow Thruster has now been set up properly using the AC drive.  The ramp up and down times have been reduced from the default 10 seconds to 3 seconds, which is about right.  The BT motor was also stopping unexpectedly, so something was amiss.  The AC drive was throwing up an error code and the thorough set of diagnostics revealed that the motor was drawing too much current from the AC drive, overheating it and tripping out.  The cause is that the BT is over propped and that the 5.5kW motor is drawing too much current, more like 7.5kW, when running at 50Hz.  The solution was to wind back the motor frequency, until the current drawn matched the output of the AC drive.  This will work perefctly well, an alternative would be to change the drive pulley ratio, so that the motor can run at its natural 50Hz, the power in the water will be the same.    Feb 09.

SPUD LEG

The spud leg is a 2.8m 200mm diameter tube which is handraulically lowered and raised using a trailer winch.  It is fitted with a mechanical interlock.

ANCHOR WINCHES

Strikwerda anchor winches are fitted are fitted at bow and stern.  Bow anchor is a 180kg klip anchor and fitted with 100m of 13mm chain, stern anchor is a 85kg fabricated klip anchor with 70m 10mm chain.  There is also a 35kg klip anchor which is small enough to deploy as a kedge anchor by dinghy.  Both winches have drum ends and are handraulic, although sprocket wheels are fitted to allow conversion to a powered system. Bow anchor winch is now motorised with a 1.5 kW Danfoss Bauer gear motor using a chain drive.

Both the gear motor and frequency inverter were supplied by AER in Kent and Robert Banks was most helpful and willingly answered my many and varied questions.  The WEG BT motor and taperlock drive pulleys and drive belt were supplied by Wyko, Oxford.


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