Jason/James,
Thanks for the great replies. Standards seems to be the only way forward for us the public to make sense of systems offered. Ever since I did my conversion the word 'continuous' and the varying claims has had me confused. Can these IEC duty cycle ratings be used?
http://www.engineeringtoolbox.com/iec-duty-cucles-d_739.html
The most I've seen at my controller is 65C after 2 1/2 hours of motoring. Normally I see 45C. I don't know about the winding temp as I could not get the KTT sensor working, so I have a handheld device to point as best as I can at the motor core. Yet to use it. I've been told by the manufacturer the winding temp should not exceed 100C. I suppose all ratings should be based on a baseline ambient of 25C.
I've come to the conclusion that lead/acid technologies are not ideal for EP and that in fact Lithium is more cost effective over time and far more suitable. My Lithiums are in series and 25.6 nominal LiFePO4. This year will be my first season with them.
As for headroom in a blow, I've never had that even with the old diesel! I consider my system just an auxiliary, just as my 10hp diesel was. In fact most diesels fitted to small yachts are not true continuous use anyhow, just intermittent duty cycle. If my boat was bigger and I wanted diesel (if I had the money) it would need to be a 1,500 RPM unit (not 3,600) with loads of power and a world cruiser around 20m LOA.
I've learned my lesson with direct drive and experimenting with a 3 blade and more pitch. Back to 2 blade for me and max rpm of 1,000. No more burning amps for me as totally agree re rpm and power. I guess it all comes down to what power is enough for any given boat and person. For me as long as I have 750 watts cruise to 1,500 Watts for short periods with a peak of just over 2kW I'm happy at that.
When it comes to tidal gates and such with either electric or diesel my passage plan has options for a safe haven. I'd never expect to punch waves with my small yacht, diesel or electric. I've been off two lee shores in tricky conditions in F5/F6 and sea room has been the saviour. When I couldn't get through the North Channel in the Irish Sea in F6/7 I simply turned round to a safe haven. Once I hit up to 2m waves in a blow my small boat makes no sailing progress to windward anyhow. Solution, go the other way. As I say if I had the money I'd want a boat in the 20m region for safety offshore with a suitable diesel. I use to skipper a 19m jet boat cat, 2,000 hp and felt safe on that up to 3 to 4m waves.
Prop fouling. I can reach my prop to clean it on the pontoon with my hands. I keep a check on hull fouling and being long keel can just lean against a wall over a tide to clean. In my area I get little hull fouling over a season anyhow.
I'm totally with you on realignment Jason. One of the downsides of my direct drive. And I agree James that optimising direct drive for different propeller sizes cannot be done as you have to choose the prop that is effectively the gearing for the motor that keeps voltage up and amps down, but if you are using low power in the first place the percentage loss is not so bad. Just back off speed or sail instead. Again it comes down to how much range and how much power is enough for a person and their boat. For me 2 x 200 Ah LiFePO4 batteries are enough. Any more (were they lead/acid) and the total system weight would be more than my old diesel. Now my weight is less than the old diesel.
I suppose at the end of the day my small system is powerful enough for my small boat and what I do. I consider my boat as a sailing boat. If I wanted a motor cruiser then a Dashew FPB and a lottery win!I But dreaming aside I'm not going back to my 22 knot cruise, 28 knot top speed 8m motor cruiser. I want to sail not motor hence I don't want a 'noisy' electric motor spinning a prop under sail on a sail boat either - unless light airs and electric motor sailing which I love. So, I'd prefer folding for pure sailing, which would be my next step. Silence is golden!
John R.
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (40) |
No comments:
Post a Comment