So Hannu,
Not to hijack the thread, but...
I have heard a lot about "over-volting" motors for efficiency and to increase torque and ultimately speed. You even elude to such in your statements about "higher voltages".
In my questioning, I have a prowler 55# thrust trolling motor I am installing in a PowerYak designed by Glen-L. The boat design states it is for "35# thrust motors." I have built one of this design before and put a 50# thrust motor on it that worked well. The Prowler is originally a 12V unit. What concerns and "mods" do you (or the forum) think it would need to bump it up to say 24V? I am guessing the LED night-light under the power console, and probably the LED power level screen on the top of the console would need some kind of limiter/resistor. Just not familiar with the size or gauging of resistors to keep it all working. Also, I understand the added 12V will add heat to the system, mainly the motor that is water-cooled. What about the speed switch in the handle/console? I also understand that the wire size is relieved for a given power setting due to a given voltage getting half the amps to produce a equal speed. It would be great to find a simple conversion site or instruction to accomplish such "hotrodding" of these motors.
Dan
Sent: Sunday, June 19, 2016 11:21 AM
Subject: Re: [Electric Boats] coronado 27 with torqeedo 1003
Dont know what this is worth, but ..
Old sailing ships, early 1900s, used things like a 60 hp motor to effectively navigate a 400 ton ship of == 30m.
By hand, I can / did easily move a 28 ton, 24 mm, Baia azzurra offshore deep-v pleasure boat on a 2400 nm cruise of about 2 weeks.
(Wind will take the boat away from you).
A human has about 100 W or 1/7 hp of power.
A much larger, lower-rise propeller, would give greatly enchanced results re_ propulsion.
A truly good electric propulsion would have a different driveshaft, about 2-3x larger diameter of prop for == 3-4 more surface area, and probably a power of 0.2 kw / metric ton.
As we cannot easily change the driveshaft, this is never done, and thus the results in efficiency/power are typically about 300%.
Ie an electric motor hp of 1/3 the typical ICE delivers good results.
I suspect, based on experience, physics, and a simple rope-pull on any nr of craft to 70 tons, the mentioned 0.2 kw/ton would be ample (0.9-.95 hull speed and some margin for adverse weather).
The very low rpm would also, imho, need high-voltage motors and or special motors to keep the currents manageable.
Ie circa 400 V / 10(-n) amps max power.
Electric power works much better at high voltage.
On 19/06/2016 15:02, oak oak_box@yahoo.com [electricboats] wrote:
Mark,I would agree that a Torqeedo 1003 is probably a bit light for a Coronado 27.However, I put a Torqeedo 4R on my Catalina 30, and it did fine. (email me off list if you would like more details).I also experiemented with both a Torqeedo 4R and a 2R on my Catalina 22, and they both did great on that boat. The 2R might be marginally powered for your 27, but the 4R should do well for all but the worst conditions. I would also note that the 4R on a Catalina 30 was not sufficient to back the boat with good control into a strong wind from a dead stop. It did just great going forward. Though I noticed that on my Catalina 27 (probably about the same size as your Coronado 27), I even had a problem backing up into a strong wind with the 10HP GAS engine - outboards just have a really hard time backing up a large sailboat with a fixed keel.If you don't have to worry about backing out of a slip in a crowded marina, the Torqeedo 2R might work (much easier to set up 2 batteries than 4), or the Torqeedo 4R would be plenty.Good luck!!John
From: mailto:mike@electricyachtssocal.com[electricboats] mailto:electricboats@yahoogroups.com
To: electricboats@yahoogroups.com
Sent: Saturday, June 18, 2016 10:53 AM
Subject: Re: [Electric Boats] coronado 27 with torqeedo 1003Mark,
You have looking at the marketing with a clear eye. It is a 1kW motor and it performance is based on that power coupled with a very efficient propeller. I sell the Torqeedo 1003 and consider it a good dinghy motor. Once you put it on a displacement hull you will be impacted by the sea state and will see its true limitations. It is 1.5hp motor at best. I.5 hp will push a small boat at slow speed but not through a rising sea as both its power level is low and the propeller, which provides much of it performance, seems to not perform as well.
The simplicity of the gasor propane outboards is when the say it is a 5hp or 9.9hp, it actually is as it is a full motor system measured at the propeller. Torqeedo uses "marketing terms" that are different than the rest of the outboard industry. The same happens when you look at an inboard diesel, it is measured as b (break) hp which is really not very transferable to marine propulsion. On top of that, the parasitic character of the transmission, alternator, pumps (all not measured in bhp, will take as much as 25% of the power away from the smallest diesel to 10% for away from the larger diesel.
Reading motor data and then evaluating true results from users is the only way to understand what works and what does not.
Mike
Electric Yachts of Southern California
-- -hanermo (cnc designs)
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Posted by: "Dan Hennis" <dhennis@centurytel.net>
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