Ok Greg, good idea, let's try a different tack. Let me lay out how this has been put together so we can assess whether it looks like it will do the job, or not. And I am more than happy to hear from those who have a viewpoint based on meaningful analysis ie from direct experience or professional knowledge or real world data. Let's keep the FUD opinions out of this, because it really is not helpful. I am hear to learn, not to be a fanboy of any particular technology. On the other hand, if I am wrong, prove it. Don't expect me to just believe your opinion because you say so. OK?
resistance work and real experience with performance on a sister ship with 39HP Yanmar
shaftdrives and Brunton Autoprops, we believe the 30kW electric
will produce 6 knots on flat calm with the right size and pitch
Kiwiprop for electric
using one motor
. OK? Lets assume this is true. Kiwiprops feather very nicely, so no more rubbish FUD about dragging around bigger props, OK?
Then we are cruising at 6 knots using 6kW/hour (from a known rpm
at a known torque spinning a known propeller
spec) which means we can cruise
for approx 2 hours until the 13kW Lithium propulsion battery
is flat. Yes I know it should not be flattened but kept to 80%DOD.
At that point we start the 6.4kW diesel generator
or the 6.5kW petrol Honda
(haven't decided which yet) and charge the now depleted battery with 2 (two) 3kW chargers, which should take about 2 hours to rechage. Right? We are now running on the other side motor
and battery for the next 2 hours. and so forth, OK?
When the 50 knot wind
causes us to drag at anchor
we can apply full throttle for about 30 minutes from each motor ( 30kW from 15kW battery), BUT
and this is the point I want to make, it will not be necessary to use full throttle because the thrust developed by the high torque electric motor
and bigger higher pitched prop will push the boat against the wind
without needing to use full throttle.
This seems to be the point that is hard to get across, so let me try an analogy and see if that works.
Let's take 2 extremes. Two boats, one has a 10HP outboard
with its normal prop (WOT is say 5,000rpm) and one has a 10HP electric with bigger higher pitched prop (WOT is 2,000 rpm). Stand up to your waist in the water
pushing against the bow as the driver puts the outboard
and motors against you. Feel the force pushing against you. Get the driver to increase revs slowly until you cannot hold the boat back any longer. Now do same thing with the electric. Take note of the revs of each boat at the point when it would push you over.
What would the result be? I maintain that you would be pushed over by the electric motor
lower revs than the petrol outboard
. I maintain that the outboard will go much faster (planing hull
form) at WOT with it's smaller but faster rpm
prop than the electric boat at WOT with the bigger, higher pitched, but slower rpm prop.
Furthermore, and this is the main point, I maintain that the electric boat will be able to maintain its lower maximum speed against a bigger force (like the wind) than the outboard, which will slow down more against the wind.
So the point re EP cruising boats is that the electric can be run at lower rpm, and hence less energy drain from battery giving longer run times and range, and still cope with adverse wind and wave conditions.
So it seems to me that with adequate solar
, adequate lithium house bank, good generator charging
system, reliable EP system from top quality components with built in diagnostics, and a vendor who stands behind the entire system (meaning they fix it no matter what!) regardless of what may develop a fault, it seems to me this has to be taken seriously as a viable cruising EP solution offering many, many advantages.
I am prepared to be convinced otherwise by argument based upon real data or other evidence. If I am right, this is really good news, it seems to me. If I am wrong, then there must be a fault at principle, not execution. Meaning there may be technically inadequate spec somewhere, but that can be modified or fixed. But if the EP system has adequate power motors and sufficient propulsion
battery to deal with adverse scenarios, and has reliability
& support, then it would seem to be a serious contender.