Although the QS 6000W motor I priced is designed for use on a small car and not a ebike type I am reconsidering this option. Their are questions about their durability and to go for a conventional proved motor is good advice. The design and fabrication of a thrust limiter or reduction drive system for me is not a problem as I have a mechanical background but only starting to get my head around the electrical side. I can see some advantages of indirect drive, proven components, no thrust on the motor, ratio's can be very easily changed, lifts the motor higher. The only disadvantage is power loss.Regarding correct prop size, on a previous heavy displacement sailboat fitted with a 30hp Yanmar the theoretical hull speed was about 7..2 kts. Full engine RPM flat out in calm water with no wind resulted in a wave forming at the transom and a noticeable squatting down in the stern. The engine was also loaded up and starting to blow black smoke. I believe that this boat had the optimum engine/propeller for it. The squatting down and stern wave is the boat trying to get up on the plane which is obviously not going to happen. Backing the throttle of 50% only reduced the speed to 5.5 kts.The Nordic 17 based on a waterline lenght of 16 feet will have a theoretical hull speed of about 5.1 kts. I suspect the sweet spot for this hull will be around 4.5 kts.--On Mon, Jan 15, 2018 at 5:58 AM, Matthew Geier matthew@acfr..usyd.edu.au [electricboats] <electricboats@yahoogroups.com> wrote:
I have 'electrifed' a similar Nordic double ender - a project that
probably inspired 'mryanqld'. These boats need very little power - I've
found that the 'sweet spot' cruising speed for my hull, the system is
running only at 1500w.. I can wind the power up more, but little extra
speed is gained for the extra power, the boat just starts to pull a
bigger wave behind it.
I'm using the orginal prop that was on the boat when it used to have a
5.7hp two cylinder, two stroke 'Blaxland'. I believe the prop is the one
that came with the original Blaxland engine and designed for the high
torque two stroke. Certainly back in the 'stink pot' era when the clutch
started to wear I'd had the clutch slip instead of the prop cavitating
when the boat was under load (lots of teens hanging of the back wanting
to be towed through the water!)
I direct drive a Perm 132, although when my Trojan's finally give up, I
may go to 48v and put a 2:1 reduction on it, the higher voltage will
lower the current and the heat losses. (But the new gearbox losses may
be higher than my current heat losses :-)
Kind regards Mick 0414 264 312
Posted by: Michael Ryan <mryanqld@gmail.com>
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (8) |
No comments:
Post a Comment