Electric boat conversion - control lever

The photo shows how engineer Alan neatly fitted the "joystick" speed/direction control lever in the same position as the previous standard "Morse" control. More about this below.

Below is the heavy duty on/off power switch (in "off" position - the "on" position puts the lever at "3 o'clock"- - a good chunky, positive switch!) that breaks connection between the batteries and the drive-motor control electronics (and all other 72V meters, etc.) This switch is required by the BSS, for giving total manual disconnection of the drive whilst being in easy reach of the helmsman - but is, obviously, also suitably convenient for emergency switch-off (and initial turn on! - and never mind the regulations!)

On the right of the mounting box for these two, you can just see the grey plastic of the automatic siphon break valve that is necessary to stop the generator cooling "live water" system potentially syphoning water out of the engine "backwards" through the (underwater, water) intake... in theory this would only happen with the generator "off" and so the water pump ("impeller") not operating... but in fact flows are obviously far more complex... and one can (just, if you listen very carefully) hear the valve "popping" (i.e., operating) when the generator is on... so it's clearly an essential part of the system!!

To return to the joystick control. This is (unfortunately) "linear", and so very sensitive for adjusting cruising speeds - and takes some learning! The thing is, one actually wants fine control over a small low-drive-current range (0 - 40A) whilst for larger "control" pulses of power... variations of 10's of Amps... don't really matter ... so it's a pity the control isn't logarithmic (like a radio volume control.).... Also, intitially, the control tended to "spring back" slightly to zero... but in time the unit "bedded in" and this effect vanished (and we learnt better how to operate it) - and control is not a problem now. On the other hand, it's quite impossible (we find) to operate it with one's hand (and arm) "in mid air" - the trick is to rest the LH side of one's (left) hand on the guard rail and then operate the lever with thumb and index finger.

Incidentally, I would deduce that, at least in principle, the drive electronics unit could be programmed (it's controlled by programmable chip, the handbook says!) to give a different response... perhaps more like the "logarithmic" I've suggested - but how one would actually go about getting that programming done and whether one could get the desired effect is unclear!

Initially, we certainly had some "exciting" moments operating the lever far too drastically - shooting from quiet cruising to violent acceleration!... and the boat's acceleration with the lever "high" is quite stunning - the boat (all 10 tons of it) almost jolts. Until we learnt better control, the other snag is that drive electronics and motor response is very rapid... BUT after about a 0.5s (seconds) "pause" as the system "winds up". So, "suddenly" wanting a burst of power for control it was all too easy to move the lever too far apparently getting no response... only for the propellor to effectively explode into action a moment later... far more than one wanted and requiring hasty re-adjustment, with the boat now galvanised into action... not necessarily in quite the right direction (and needing stopping!)

BUT, to re-iterate, with experience (and the lever itself "bedding in" from awkward initial "springiness") we now get extremely good boat control. Indeed, we find, better than was ever possible with a traditional drive once one is familiar with the lever and the response - although one can gain for using slightly different techniques.

In particular, if you allow for the response "pause" between moving the lever and thrust, one can get extremely positive control by deliberately applying a really short burst of power (tiller in appropriate position) - literally moving the lever up and then back down almost before the motor has responded to give the boat a short shove in the right direction - and control by little pulses of power like this can be incredibly effective... one can have the boat swinging "just so" and then use no power at all as it swings onto the required line. It takes some learning, but can be very effective... and use hardly any average power!!

We do have a snag we believe is due to the crude nature of our old hull design - if one applies high reverse power, the boat tends to "pull left" (i.e., to port) ... I'm not necessarily convinced by explanations, but live with the fact it does! The trick here is (a) allow for this effect and (b) to only use a very brief pulse of reverse to cause drastic slowing, then gentle reverse (where the "pulling left" effect is negligible) to maintain the effect.

In terms of sturdiness and weather resistance, these controls have proved entirely durable (they have never been covered for the last 14 months!.) Another plus for the conversion.