Electric outboard drive for small cruisers

  • 06 Apr 2020 18:32
    Reply # 8882055 on 8809939

    hi david

    sometimes you need an excuse to go sailing!
    i'm glad that everything went well…

    ueli

  • 06 Apr 2020 18:02
    Reply # 8881974 on 8809939

    No damage; thanks for asking. Got away with it this time.

  • 06 Apr 2020 17:38
    Reply # 8881896 on 8809939
    Deleted user

    No damage, I hope......

    Matthew


  • 06 Apr 2020 13:42
    Reply # 8881271 on 8809939

    Ahem. As it's turned out, the first trial was today, in slightly less than ideal circumstances. After a breezy night, a neighbour came to tell me that Weaverbird had broken free* and was trapped against the railway bridge. Out with a light inflatable tender, down the road, pump it up, get aboard, fit the motor to the bracket, connect it up - all at the double. That's my vigorous exercise for the day.

    I'm happy to report that there was plenty of power available to get her off against a moderate breeze, and control was good. I discovered that the magnetic cutout's lanyard wasn't quite long enough, and was tied with landsman's knots, which added to the fun.  At least it was sunny and warm.

    * I later found that the mooring strop had got caught around one of the keels and chafed through.

  • 04 Apr 2020 10:45
    Reply # 8878498 on 8809939

    Thanks, Kurt, that's encouraging. Now 'all' I have to do is to get through the current situation unscathed, complete my installation and be in a position to go out and get some real-world data myself.

  • 03 Apr 2020 21:15
    Reply # 8877876 on 8809939

    A little real-world data from pretty careful measurements I've taken over 2 seasons, in canals and up & down the River Thames:

    minim makes a little over 2 knots on 250W electric input.

    2.5 knots on 450W

    3.25 knots on 1100W and that is nearly top speed

    So, with her 280W solar panel in good sun, she glides through the middle hours of the day for free, or sits still & recharges from a cloudy yesterday, and she confirms the classic shape of the power-speed curve - slow is easy.

    (Newbridge Coromandel; 6.4m oal, 5m wll; ~1 tonne displacement.

    Motorguide 24V '82lb thrust' trolling motor; 9 inch diameter 3-blade prop.

    3840WHr lead-acid battery bank.)

    mehitabel is 12m, ~11 tonne and makes >2.5 knots on 1100W - even big and slow is easy.

    (really good data is hard to get in open & tidal water, of course. but over a long time, that's quite reliable for mehitabel too.)

    Economics? Well, if I replaced mehitabel's tired (AGM) batteries now, I'd spend more than I would have for diesel over the ten years they've served. But I'm eking them out, and it's not too difficult.

    Cheers, Kurt





  • 27 Mar 2020 16:38
    Reply # 8862370 on 8809939

    Yes, David, I purchased a chinese hydraulic crimper from eBay a couple of years back, rather quaintly described as "Hydraulic Pliers"  - one of my better tools, it made all the battery, inverter and alternator cable making an actual pleasure.... and ~£20 from memory.

    I think that the pressure is such that you achieve a "pressure weld" of the cores and lug - this is the same process that "wire-wrap backplanes" achieved in the 70s in computers of the day - the point pressure of the wire being wrapped around sharp-cornered pin was high enough to achieve the same result... and they were ultra reliable, with thousands of connections on a single backplane you would soon know if the process was less than perfect or allowed any corrosion...

    Last modified: 27 Mar 2020 16:39 | Anonymous member
  • 26 Mar 2020 15:51
    Reply # 8860213 on 8860153
    Darren wrote:  Here is another example, the pic on the left is made with an indent crimper, like I mentioned earlier in this thread and the pic on the right is made with a hexagonal die, like the kind David bought.  

    When I made the butt splices, I was able to look down inside after I'd crimped one end. I can confirm that 10 Tonnes of pressure on hexagon dies is pretty darned effective at squashing the copper cable and terminal into a solid mass.

    For the copper strap.  The strap itself should be fine left bare, but the mechanical connections are best with something to exclude air and liquids.  Silicone dielectric grease is the gold standard, but has the drawback that it is silicone.

    I carry a 50 gram tin of silicone dielectric grease aboard. That's enough to last a lifetime, it only needs a little smear on the surface to be protected. It's great stuff for any kind of plug and socket connection - phone and tablet charging sockets in particular.


  • 26 Mar 2020 15:19
    Reply # 8860153 on 8857430
    Deleted user
    Anonymous wrote:

    Plain, un-tinned  copper will corrode at the joint, would solder tinning the wire ends before crimping be a good idea?  Likewise a copper strap.

    I used to be a follower of the solder faith, and I suppose none are as devout as the converted, so please excuse me if this sounds like I'm once again mounting a soap-box :-)  If you don't have extra time on your hands due to Covid 19, then the bottom line is crimps are great with glue lined heatshrink, otherwise, hopefully what follows is either entertaining or informative.

    Glue-lined heatshrink can be used for insurance for crimped terminals. Heat it not just until it shrinks, but until you see a little glue ooze out of both ends.  However, the crimp itself is almost as good as the wire are resisting corrosion.  Keep in mind, there are millions of cars driving around on salt-laden roads in the winter.  All of their connections are crimped and most are less protected than you will do on your boat.  Lots of folks have seen, made or inherited poor crimps and this probably makes them more concerned than necessary.  A proper crimp matches the ferrule to the wire size so there is little extra space before the crimp.  During the crimp both the wire and the terminal deform to create a join that should not have any gaps.  It should be air tight.  I've actually gone to the trouble to cut a lug in half, acid etch it, and view it under the microscope to confirm that I can make crimps this well.  But, for those that are wiser with the use of their time, here is one example of what a good crimp should look like.  Here is another example, the pic on the left is made with an indent crimper, like I mentioned earlier in this thread and the pic on the right is made with a hexagonal die, like the kind David bought.  

    For a person at home, or on their boat, most industrial means of inspecting crimps are impractical (expensive, specialised equipment, etc.).  However, there is a pretty good relationship between mechanical strength and electrical conductivity in crimps.  So, buy a couple extra lugs and make a test piece.  If you can come between the UL and Mil Spec tensile strengths listed in this table, you're making good crimps.  Your test apparatus need be no more complicated than the rafters of your garage (or a tree branch), a bucket, a bathroom scale, and a way to keep yourself (especially toes), away from danger should the connection fail.  Weigh things on your scale and add them to the bucket until you meet the spec weight or the connection fails.  Please use sense in testing, don't use something stretchy (use chain rather than nylon line) in the test rig so that things don't fly about if they break, wear some safety glasses, be responsible for your own safety.  If you use a plastic bucket, think about how strong it and its handle are.

    For the copper strap.  The strap itself should be fine left bare, but the mechanical connections are best with something to exclude air and liquids.  Silicone dielectric grease is the gold standard, but has the drawback that it is silicone.  Maybe it's just me, but silicone seems to like to go everywhere and also has the property of being impervious to virtually all solvents and cleaners.  Thus, years later you may wonder why you are getting fish-eyes when you refinish your brightwork because you have long-forgotten the silicone fingerprints you left behind.  I keep a small tube of silicone dielectric grease for things like VHF coaxial connections that need the very best.  I've used a fair bit of Grote Ultra Seal, mostly because it is easy for me to get locally.  It is some kind of petroleum based grease.  It seems to get thicker and darker as it ages on the connections.  However, I've pulled apart stuff more than ten years old and it still seems to be doing its job.  Get the tube version for less mess.  Lanolin is another alternative.  Lots of us have experience with Lanocote.  This is Lanolin with petroleum distillate added to make it workable through a wide range of temperatures, it may have other additives.  I'd just as soon not have the petroleum distillates, so I've been using straight anhydrous lanolin for a while now.  It seems to work just as well, and your hands are silky smooth at the end of the project.  During Canadian winter temps you need to keep the container in your pocket or it gets too cold and hard to work with.


  • 26 Mar 2020 00:07
    Reply # 8859250 on 8857430
    Anonymous wrote:

    Good subject and lots of useful info.  
    I have to say that soldering wires is an art I have never mastered, copper pipe fitting I can do.

    Plain, un-tinned  copper will corrode at the joint, would solder tinning the wire ends before crimping be a good idea?  Likewise a copper strap.


    From the post below: "The problem most folks will run into is that by the time you get a part as large and heavy as battery cable hot enough to solder, it is very easy to have the solder wick along the wire." This means the stranded wire you paid extra for becomes one solid wire more likely to break with flexing.  Also ... as if that is not enough, a layer of solder before crimping means the crimp will not be fully tight or as tight as it would be with no solder. If the solder gets hot enough, it moves to a part of the joint with more space for it leaving the joint loose which leads to more heat and eventually smoke... There are covering for battery terminal connections, depending on the battery chemistry involved. That is why your car probably has lead posts and lead ends on the cables... and still corrodes in an acid fume environment. Lithium based (or sealed) batterys have less problems in this area. For salty air, shrink wrap (the best is the stuff with melty goop inside) is the easiest stuff to use. Done properly, it leaves no air next to the copper.
       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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