Page 2 of 2 FirstFirst 12
Results 36 to 46 of 46

Thread: Arctic Tern Electric Power

  1. #36
    Join Date
    Aug 2011
    Posts
    913

    Default Re: Arctic Tern Electric Power

    What by the way is the displacement of arctic tern in crusing trim.
    What sort of power would you need for a 2200lbs sailing boat?
    Perhaps 2 motors?
    The batteries are easy to obtain and good ballast too.

    James

  2. #37
    Join Date
    Dec 2008
    Location
    Maitland, Nova Scotia,
    Posts
    451

    Default Re: Arctic Tern Electric Power

    How about using a salt water motor, would not expect the regular motors meant for fresh water to do very well in salt water.

  3. #38
    Join Date
    Jun 2006
    Location
    SE Mich
    Posts
    1,659

    Default

    Quote Originally Posted by Jamesh View Post
    What by the way is the displacement of arctic tern in crusing trim. What sort of power would you need for a 2200lbs sailing boat? Perhaps 2 motors? The batteries are easy to obtain and good ballast too. James
    I'd guess around 600#. Not much.

    The 'how much power' question depends on how far and how fast you want to go. One cheesy trolling motor and one 50# battery would easily move your boat around in calm wind and still water for an hour. It wouldn't be practical outside that narrow definition though.

    A decent system would be a 5 kW motor with four 60# 12v batteries. A better one would use 8 6v batteries
    Denny Wolfe
    www.wolfEboats.com

  4. #39
    Join Date
    May 2010
    Location
    Chicago
    Posts
    563

    Default Re: Arctic Tern Electric Power

    This is what I don't quite understand, why would anyone put a resistor in parallel with a motor? That would just waste power. I can imagine putting a resistor in series with a motor which would be a crude but effective speed reducer. If anyone can verify that the speed coils are parallel to the motor, then the coils are probably acting as additional field coils in a shunt-wound motor. Contrary to intuition, a stronger field reduces the speed of a motor by increasing the back-emf of the armature. This would also explain why the current doesn't decrease at lower speeds as much as one would imagine; the extra juice is used to suppress the rpm.
    Ken

    Quote Originally Posted by mcdenny View Post
    Yes the lower speeds put a resistor in parallel with the motor. As the speed drops the load on the prop lessens so the current doesn't go up.

    If I recall speed 5 puts all 12 v into the motor and speed 4 cuts that to 6 volts.

  5. #40
    Join Date
    May 2010
    Location
    Chicago
    Posts
    563

    Default Re: Arctic Tern Electric Power

    Actually, I just thought of another possibility (which I can't test either because the motor is 1200 miles away)it could be that the field coils oppose the permanent magnet, that the lowest speed is the one with no field coils energized, and the coils weaken the field, increasing the speed. Someone from Minnkota needs to chime in here, or someone who can open up one of these motors and find out how they are wired.

    Quote Originally Posted by kbowen View Post
    This is what I don't quite understand, why would anyone put a resistor in parallel with a motor? That would just waste power. I can imagine putting a resistor in series with a motor which would be a crude but effective speed reducer. If anyone can verify that the speed coils are parallel to the motor, then the coils are probably acting as additional field coils in a shunt-wound motor. Contrary to intuition, a stronger field reduces the speed of a motor by increasing the back-emf of the armature. This would also explain why the current doesn't decrease at lower speeds as much as one would imagine; the extra juice is used to suppress the rpm.
    Ken

  6. #41
    Join Date
    Jun 2006
    Location
    SE Mich
    Posts
    1,659

    Default

    Maybe I mis-spoke 😬. Probably the resistors are in series with the motor brushes.
    Denny Wolfe
    www.wolfEboats.com

  7. #42
    Join Date
    Jan 2008
    Location
    Lake Champlain, Vermont
    Posts
    2,558

    Default Re: Arctic Tern Electric Power

    Quote Originally Posted by kbowen View Post
    . Someone from Minnkota needs to chime in here, .
    Good luck trying to get MK to speak on the issue. They have refused to reply to several requests I have made on their "help line" which is no help at all.

  8. #43
    Join Date
    Apr 2012
    Posts
    216

    Default Re: Arctic Tern Electric Power

    When I asked MK about the amperage of a 10 lb thrust motor bought about 1975, they replied within a week.

  9. #44
    Join Date
    Jun 2006
    Location
    SE Mich
    Posts
    1,659

    Default Re: Arctic Tern Electric Power

    In case anyone finds this old thread, I've just refinished the boat to sell (check out Woodenboat website ad) as its been sitting unused for several years. Battery was dead as a doornail of course but the motor (installed used 8 years ago) and electronics still work fine.
    Last edited by mcdenny; 07-12-2018 at 12:03 PM.
    Denny Wolfe
    www.wolfEboats.com

  10. #45
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    10,571

    Default Re: Arctic Tern Electric Power

    That is a fine looking vessel for a very attractive price. I hope someone snaps it up.
    I also just sold two boats (canoes) that had been sitting around unused for years. Better someone else uses them then have them hanging in the rafters gathering dust.
    I was born on a wooden boat that I built myself.

  11. #46
    Join Date
    Jun 2006
    Location
    SE Mich
    Posts
    1,659

    Default Re: Arctic Tern Electric Power

    Thanks Rich. I priced it to sell as I know it can be very hard to sell an owner built wood boat, no matter the quality.

    In this case it sold right away to a guy from southern CA who saw it on the WB site a few days after to ad went up.

    In related news I finally sold my second Harmony 25 (for about the cost of materials) after six years of trying.
    Denny Wolfe
    www.wolfEboats.com

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •