electrics continued.

short delay caused by doing a delivery bilbao to dublin of a small
voith schneider propelled tug called Beaufort for dublin port company.
6 days to take over from shipyard, obtain certificates and prepare for sea passage. 4 beautiful days at sea with very kind weather force 3 max. we had to go round the coast of biscay for insurance purposes but more days more dollars. a day handover in dublin, night in hotel then back to holyhead on ferry. no flying, yippee!!

got home to find speed controllers had arrived so installed all
electrics. but then found transmitter had been affected by damp
so could not program it for new model. sent that off to the
graupner transmitter krankenhaus for repair. while waiting for
that to return did float test in bath, shifted main batteries
to obtain required trim and found she floats on her marks with
no further ballasting required.
am using 2 x 12v, 7 A/hr gell batteries mounted on their sides
for main motors,
1 x 6v pack of 4 x 1.5 v 2500 mA/hr NiMH AA cells for bow
thruster.

2 x 20 Amp viper marine reversable electronic speed controllers
(esc) for main motors.
1 x 10 Amp esc for thruster.

2 x standard servos for port and starboard rudders.
2 x 20 Amp switches and 1 x 10 Amp switch for main motors
and thruster respectively.
2 x 15 amp fuses for motors and 1 x 5 Amp fuse for bow
thruster.
intend rigging external charging points for batteries so won't
need to disturb covers.

1st pic shows main batteries, receiver and its powerpack.
2nd shows antenna exit point between port funnel and deckhouse.
3rd shows escs and servos with esc switches.
4th shows motor and thruster switches and fuses.

total hours 300 dead.

although this model more involved than voith "parat" experience
gained doing her stood me in good stead for this one.

am going away again next week to deliver a supply boat from
ravenna (Italy) to Istanbul. should get 2 weeks out of that.

FINISHED!!!!

finished fitting tyres, last touch up and construction is complete.

still waiting for r/c gear. come on postie!!!

the electronics bit.

yesterday realised model had no radio antennae so knocked up a duplex pair of mf/hf aerials with antenna matching units out of a scrap bits of 6x3mm plastic and 0.8mm wire. will do some vhf aerials this afternoon. glued up the rudder halves onto the rudder shafts with slow set epoxy. got to be really careful not to get any ooze out in the bearings. painted inside hull with grey primer, bit of window dressing. have been looking at electronic speed controllers (esc) on 'tinterweb. have had my eye on viper marine 20amp units for main motors and 10 amp for bow thruster motor. however b/th is 6volt and main motors are 12v. i understand that escs do not reduce voltage but switch the supply on and off very quickly. the varying of time on, with respect to time off, thus permits the motor to be controlled. i believed that excess current (electron flow) is what causes motors to burn out, so if the current is restricted heat build up should also be restricted and as i can program my transmitter to not request esc to deliver full current then my motor would be safe. i needed advice so spoke to mrs. white at model slipway and she put me on to dave milbourn at action electronics (he drew up the working plans for aziz and a plan of the suggested electrical layout). he shot me down in flames and suggested i use a separate 6v power supply dedicated to the bow thruster. i decided to heed his advice as i don't want to prove myself wrong the hard way. (i have made the thruster motor accessible but only just). he also suggested i us a dual mixed esc module which reduces the speed of the inboard motor when rudders are moved. i have seen these modules in action but they are used to simplify the installation and save money but this is obtained at the expense of the full manoeverability that i wish for. it has been shown many times on full sized vessels, turning at speed, that reducing power to the inboard engine actually reduces rate of turn rather than increasing rot. this is because the lift of the rudder is greater than the torque between props. i am going to have independent motors and also independent rudders as per most supply boats. on a full size vessel it can take 20 seconds for the rudders to go hard over from one side to the other and when your close under a rig that's too slow. by swinging both rudders inboard and forgetting about them, the rudder on the ahead screw is always in position to swing the stern.(rudder position on astern screw has little or no effect). the engines can go from ahead to astern in most cases in 8 seconds or less. this is what i'm used to and will incorparate in the finished model. then i can "make it talk".

so i'm eagerly awaiting the postman with my servos, extension leads and escs. got to get some fuse holders and a couple of 20 amp switches and then i can box the job off. i'm going away on sunday to deliver a new tug from bilbao, spain to its new owners in dublin. hope to be back in 7-10 days weather permitting (march-biscay-some hope) more days more dollar!!