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!!