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Duffy Electric boats....?

Discussion in 'Tenders & Dinghies' started by Norseman, Sep 18, 2013.

  1. BEK33

    BEK33 New Member

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    I have just bought a 2004 Duffy but not yet taken delivery and am looking forward to playing with the new toy.
    I can't work out how to post a new message without using "reply". I hope that this does not offend users.
    Do any users have thoughts about adding a swim platform? A pity to spoil the lines, but Florida waters are too tempting not to swim in from time to time.
  2. Norseman

    Norseman Senior Member

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    Picture, post a picture..
    Not sure about a swim platform on a Duffy, but perhaps a removable swim ladder on the Starboard side?
    I never swam or dove of my Duffy, she was more like a bar/restaurant cruiser and good at it.
    Now I regret selling the Duffy, should have kept it. Perfect canal boat for Fort Lauderdale.
    Live and learn.
  3. BEK33

    BEK33 New Member

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    No photos yet as I will not be taking delivery until later in January, but I am enjoying planning next year's use. In the video on the Duffy website there is a picture of a 21 with a very good looking platform on the transom. I would like yo know what mounting/fixing technique was used as there does not seem to be much space below it for support legs.

    I will need a trailer at some stage and would appreciate any feedback on trailer selection if any forum users have trailed their Duffies.
  4. nevetsyad

    nevetsyad New Member

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    How did the solar work out? I'm looking for a Duffy 22 Cabin Cruiser that I can stick 8 100 watt semi flexible panels on. I'm thinking two charge controllers, 400 watts of panels on each controller, 48 volts out to each bank...not exactly cruising speed, but enough to drive the boat at about 3 knots, right?
  5. Norseman

    Norseman Senior Member

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    Think of solar panels as extending the range, not powering the motor:
    If your batteries are depleted to the point that your speed is down to 3 knots, you are damaging the batteries and the boat will barely run on solar alone, even if you bypassed the batteries.
  6. nevetsyad

    nevetsyad New Member

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    I was thinking more like - batteries are full, sun is out, set it to a slow cruise, and go all day while barely using the batteries, or not touching the batteries. Not, batteries are dead, limp back to the docks slowly. Or, use one bank to 50%, then switch to the other, both are charging at around 8 amps and 48 volts constantly, while doing a decent 5knot cruise speed. Could really extend the range. Considering camping out over night, charging up a bit in the morning, and knowing I'll have full batteries before heading back.

    Also, dreaming of taking a week or two off and hopping around the Chesapeake 10-30 miles a day, purely off solar. Stop at marinas for a full charge and a shower every two days maybe?
  7. Norseman

    Norseman Senior Member

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    Not touching the batteries?
    As in by-passing the batteries completely?
    Probably not a good idea, you would need thick cables from the panels to the speed controller, in addition to the thick cables from the panels to the voltage regulator for charging the batteries from solar.
    Make it simple, use the batteries at all times and let the solar panels help to keep the batteries charged up, or slow the discharge.
    Don't forget to install an MPPT Solar booster, it makes a big difference..
  8. nevetsyad

    nevetsyad New Member

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    No, just as in, putting in 20 amps, running the motor at 20 amps. Cloud hits, it drains more than it puts in. Sun comes out more, may put in 25 amps and we keep pulling only 20 amps.

    Yup, I upgraded to an MPPT on my sailboat and I could never go back to MWP. So much more efficient.

    There was a guy that said he was adding solar to his Duffy on here, never heard back from him...

    Also, anyone know what the draw is at various speeds on the 22? I'm curious if 12-18 amps at 48 volts going into the bank would be enough to do a decent cruise without needing much juice from the battery. Does the quoted run times on the Duffy page give 50% battery usage, or fully drain times?
  9. Norseman

    Norseman Senior Member

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    Not sure about the 22, but on my 18' Duffy with 8 GC batteries, the factory quoted 15 hours run time.
    Cut that in half, then in half again to stay above 50% discharge.
    4-5 hours at good speed is safe and comfortable, another hour with solar panels perhaps.
    I looked at panels as well and did the calculations, in my case not worth it as a 4 hour ride cost $0.50 worth of shore power.
    Panels and a good MPPT would cost $1,000's.
    You want to go further, add batteries instead of panels and plug in each night.
    Or both, depends on your piggy bank:)
  10. Capt J

    Capt J Senior Member

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    You'd be better off with a 2000 watt Honda generator and the largest battery charger it will run. :D
  11. Norseman

    Norseman Senior Member

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    Nooo.
    Trying to avoid the noise, the gas and the fumes.
    You missed out on the Duffy rides Capt. J.
    Too late now, otherwise you would have one your self.

    I regret selling my Duffy and buying this twin outboard job but money was burning a hole in my pocket,
    Duh..
  12. joules

    joules New Member

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    I have carefully evaluated the battery market for my 48V Duffy. The best possible use of money is to buy an inexpensive (Cosco Interstate) 6V battery string, and use the $1000 you have saved on batteries for solar panels. You could quite easily get 800W PCT above a surrey top if using flexible modules. With a modern brushless motor this is more than enough to propel Duffy at cruise speed (mine needs 500W for 4kts). 100W panels are the best value at $1.6/W shipped, and you need an MPPT charge controller. Even if you don't fully offset the motor's battery consumption, the solar input will reduce your Peukert losses in the batteries, combined with any power offset will extend your range beyond what a set of premium batteries will get you (especially true for GC2H form).

    I don't have a surrey top, so my solar build is a bit more complicated. I have the original fiberglass cabin pop-top.
  13. joules

    joules New Member

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    BTW, I own a Honda/Alpha Power Systems 48VDC 3kW generator. Super quiet. Its not part of the boat though. The largest AC battery charger I have is 48V 60A, but again, not part of the boat.
  14. Flyinbob

    Flyinbob New Member

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    If you are going to go a distance, you should have a trailer that will allow the Duffy to sit on its keel rather than the hull alone. That is how the Duffy trailers are designed. The boat sits on the keel and the rails are just to keep the boat upright

    21 A Trailer.jpg

    The Hull ID Number is normally on the starboard side of the stern, just under the rub rail.
    .
    Last edited by a moderator: Jan 10, 2017
  15. joules

    joules New Member

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    My much older Duffy, which was actually built by W.D. Schock corp has the HIN on the transom, port side facing aft.

    I spent a portion of my vacation modifying a steel trailer to haul a Duffy across the country, which included a day of setup and adjustment.
  16. Flyinbob

    Flyinbob New Member

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    Aloha y'all,

    I've been dealing with Duffys for 12 years as a dealer in Honolulu, and I can say without any reservations that solar panels may make you feel as one with the environment, but they will NOT run the boat.

    Duffy has tried all of the permutations and doesn't even recommend them as an option. You can solar charge the batteries so that if you are idle for a week your 48V will take you out for 4 hours. That's about it.
  17. joules

    joules New Member

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    Hi Flyinbob, I agree, you can't really run a Duffy from solar panels. But what I am talking about is the net energy budget for boating. Since I upgraded my motor technology I saw a 40% reduction in power required to turn the prop at the same speeds. High is 1200W for 3000RPM at 6mph and low is 500W at 1500RPM at about 3.5mph.

    Solar on my boat will be intended to offset some motor energy consumption, while this sounds pathetic it actually has a profound impact on range and cruise time during the day:

    210Ah Costco Interstate GC2 battery:$85, 7.09 Wh/$, $1760 for a bank of eight 440lbs
    260Ah T-145 Trojan GC2H Battery: $230, 15 Wh/$, $672 for a bank of eight 576lbs

    Use the spare cash to purchase $1100 worth of solar modules and MPPT charger.
    $190 for Genasun 350W boost 48V MPPT
    $640 for Kingsolar (4)100W flexible PV modules
    $100 for fuses, wiring and misc hardware
    $170 for Victron 700-BMV energy monitor
    $1100 total

    Float plan energy budget: 1200W high speed cruise 25A discharge to 1.75VPC
    184Ah from 210Ah battery (7.38hrs)
    234Ah from 260Ah battery (9.38hrs)

    With a 300W solar offset your new discharge rate is 18.75A, which puts you at 194Ah deliverable from 210Ah batteries, 10.34hrs of cruising. So the same investment, an hour extra of cruise time, solar panel tree-huggery goodness, ~120lbs lighter, self charging (approximately 3hrs of solar charging for each hour used on high) and you end up with awesome battery fuel gauge from Victron.

    If you store your boat outdoors I would recommend heavier glass and aluminum PV modules, which are significantly cheaper than the Kingsolar flexible modules.

    If cruising on low speed 500W (10.4A)
    210Ah from 210Ah battery (20hrs)
    269Ah from 260Ah battery (25hrs)

    With a 300W solar offset your new discharge rate is 4.15A
    241Ah from 210Ah battery (58hrs)

    Of course you can't harvest at night, but is still a valuable comparison on how PV modules can offset Peukert losses at the batteries.
  18. Jim robertson

    Jim robertson New Member

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    m
    I was told that the Duffy should not sit on the keel because the weight could damage the keel. I purchased a boat trailer for my Duffy but I am concerned that the keel could be damaged. Can you help. Does the attached trailer look ok for a Duffy. The previous owner said he hauled his Duffy on it. Thanks, Jim

    Attached Files:

  19. BEK33

    BEK33 New Member

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    Do you ar any other member have any info from Duffy about the boat not being designed to sit on its keel. I am used to sailing boats which tend to have ballast in the keel and so are strongly built down there, so while I can understand that it might be true that the Duffy is lightly built in the keel area I am keen to get the facts. My concern is that I am about to buy a trailer and to me it makes sense to have the weight on the keel with the side beds or rollers merely holding the boat upright. I don't want to make an expensive mistake.
    Bernard
  20. Jim robertson

    Jim robertson New Member

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