inboard electric-powered kayak

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  • mcmanusr
    Junior Member
    • Mar 2011
    • 3

    #31
    Re: inboard electric-powered kayak

    Gentlemen, the information you need is all in a book titled "Electric Boats The handbook of clean quiet boating by Douglas Little. Hull number one of the McManus Boatworks (downtown chapter) was built using the propulsion principles as laid out in this book. (pictures to follow as soon as i can post them somewhere online). He details a method for mounting the submersible electric motor (don't say trolling motor) which I found effective both in my prototype (a 16' Old Town Loon) and the finished hull which is a beautiful sharpie. Basically i installed a teflon tube that passes through the hull that is slightly larger than the motor shaft. There is a skeg that protects the submersible electric that also helps steering. I found that it is very effective, the speed controller is in the cockpit and I use a tiller to steer. With no visible propulsion I get a lot of "hey how are you paddling that thing?" More later and hopefully pics tonight.

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    • McManusBoatWorks
      Shanty Boater
      • Feb 2010
      • 101

      #32
      Re: inboard electric-powered kayak

      Hello All

      I found some pictures of Bob's Electric Sharpie on the Duckworks site and a link to the Douglas Little book on designing and building small electric boats that he referred to.












      Comment

      • McManusBoatWorks
        Shanty Boater
        • Feb 2010
        • 101

        #33
        Re: inboard electric-powered kayak

        Bigger images. Still trying to figure this picture upload out. What a pain!!!













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        • Thorne
          Like my hat?
          • Aug 2005
          • 16414

          #34
          Re: inboard electric-powered kayak

          In Flickr - You usually have to first click the photo to bring up the black-framed viewer, then click the "View All Sizes" link near the top right. Then you can get the image URL by right-clicking the image. Alternately you can go to the Actions menu on the upper left, then select "View All Sizes".

          But from what I can see you have posted them as large as they can be just above. To get anything larger, you'll need to go back to the source and see what is available.

          I can't find anything on Duckworks under "Electric Sharpie" - was there another name used?
          "The enemies of reason have a certain blind look."
          Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

          Comment

          • McManusBoatWorks
            Shanty Boater
            • Feb 2010
            • 101

            #35
            Re: inboard electric-powered kayak

            Thanks for the advice Thorne.

            The duckworks link to my brother Bob's pictures and description are as follows:



            Or you can just Google "duckworks mcmanus"

            Comment

            • mcmanusr
              Junior Member
              • Mar 2011
              • 3

              #36
              Re: inboard electric-powered kayak

              many thanks to McManusBoatWorks for posting the pics for me. If you look at the pics you will notice that there is only one battery in this boat. Honestly for a car topper I drive to the pond or stream of my choice, and remove the battery from the truck, I boat 5 or six hrs and then put the battery back in the truck and go home. The requirement to go the full 5 knots that this design is capable of seems fast when you are cruising. The sensation of speed you get from being right on the water makes you feel like you are flying at 5 knots! I would say that anyone desiring to build such a boat should keep the speed requirements conservative because this boat at 3 knots feels like 14 kts in a normal skiff. I used the cheapest trolling motor that i could find and i purchased it at a boat show for $99.
              I strongly recommend Douglas Little's book as he has tons of experience with designs like mine and he explains in lay man's detail everything you need to know to enjoy one of the most fun types of boating there is available. We own many boats, Boston Whalers, sailboats, big cruisers, you name it but none compare to a slow quiet cruise through the mangroves in the electric cruiser!

              Comment

              • stuckinthemud
                Senior Member
                • Jul 2010
                • 161

                #37
                inboard electric-powered kayak

                Cheers for posting the pics Mcmanusr, really a great looking little boat.

                Comment

                • mcmanusr
                  Junior Member
                  • Mar 2011
                  • 3

                  #38
                  inboard electric-powered kayak

                  Thank you I appreciate the kind words. I feel the need to clarify my last post. When i say i take the battery out of the truck, i mean I open the hood and disconnect the batt and remove it for the trip. Replace it afterwards and go home. This keeps you from having to put a heavy boat in the truck, and it charges the batt for you so you skip the step of taking the batt in the garage and hooking it up to the charger after a day of relaxing cruising. If you install a amp meter and spend some time using the boat you will learn when it is time to return to shore and become confident that the vehicle will start when you put the batt back in. One of the problems with electric boats is that when the batts are dead your toy just sits there until your trickle charger brings the batts back up. This way the boat is always ready when you are.

                  Comment

                  • Thorne
                    Like my hat?
                    • Aug 2005
                    • 16414

                    #39
                    inboard electric-powered kayak

                    Most modern vehicles won't like having the battery disconnected like that - all sorts of computers, switches, radio settings, alarms rely on having an uninterrupted source of trickle power. And most vehicles use batteries rated for starting power, not length of charge and ability to recharge like a Boat/RV battery.

                    Easier to buy a good smart charger and use that on a deep cycle battery in a transport box/case. If you think you might ever use it near the water or at a marina while cruising, get one of the portable marine-rated ones. The solid-state ones without fans are better than the fan-cooled ones if you will be anywhere within earshot -
                    "The enemies of reason have a certain blind look."
                    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

                    Comment

                    • Woxbox
                      Senior Member
                      • Feb 2006
                      • 9923

                      #40
                      inboard electric-powered kayak

                      I just picked up an AGM starting/deep cycle combo battery for $150, rated at 70 amp hours or so. The price on AGMs is coming down a lot, and I think they're cheap enough now that it doesn't make sense to stick with the cheap ones, which don't last as long and can leak acid.
                      -Dave

                      Comment

                      • mcdenny
                        Senior Lurker
                        • Jun 2006
                        • 1657

                        #41
                        Re: inboard electric-powered kayak

                        I found a sale at Cabella's and got a 80 ah AGM battery and 6a marine smart charger for $220. My sailboat is trailered so the extra weight of the battery and charger is not a problem. The charger is mounted and wired permanently in the boat so I can just plug the boat in at home.

                        Just a note on battery ratings: The 80 amp-hours number refers to how much energy the battery can produce over 20 hours. In this case that would 4 amps for 20 hours. Current and time are not a linear relationship, though. The higher the current the less energy the battery can give up. This 80 ah AGM battery could only produce about 60ah if you discharged it at 16 amps. Pushing a little boat with 12 volts will take usually 10 - 20 amps. Batteries also have a spec called reserve capacity. This is the number of minutes the battery can produce 25 amps. Reserve capacity is a more relevant spec to use when making battery comparisons. For equal amp-hour (technically C20) ratings AMGs are usually better than wet cells.

                        Lithium batteries are better than AGM, they have almost no loss of capacity at higher rates of discharge. They are a lot lighter too but come with their own unique issues that boil down to a much higher price. Probably 3X AGM cost if you are an electrical hobbyist wanting to do a science experiment in your boat to 10X AGM for an off-the-shelf robust solution.
                        Denny Wolfe

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                        • CK 17
                          Senior Member
                          • Jul 2002
                          • 9374

                          #42
                          Re: inboard electric-powered kayak

                          I'm considering a trolling motor for my CK 17. What happens if this setup gets submerged--say in a knockdown. I know the electronics in the motor would probably get trashed. I'm more concerned about safety. I called mini kota and they didn't want anything to do with it. basicly they said water and electricity never mix. What do you guys think?

                          Thanks

                          __________________________________________________ ________________________

                          Comment

                          • David G
                            Senior Member
                            • Dec 2003
                            • 89688

                            #43
                            Re: inboard electric-powered kayak

                            I missed this thread before, but will now contribute my tiny little tidbit. I have a client who has two electric Electa-Ghosts. Fiberglass with a battery box in the middle. Minn-Kota lower unit housed behind the aft bulkhead, and sticking down into a tunnel-hulled sort of cavity in the hull. They use them on their lake a lot during the summer. Love them (that's why they bought a second one). From his description, they don't expect a lot of battery life... like a couple hours max.







                            David G
                            Harbor Woodworks
                            https://www.facebook.com/HarborWoodworks/

                            "It was a Sunday morning and Goddard gave thanks that there were still places where one could worship in temples not made by human hands." -- L. F. Herreshoff (The Compleat Cruiser)

                            Comment

                            • mcdenny
                              Senior Lurker
                              • Jun 2006
                              • 1657

                              #44
                              Re: inboard electric-powered kayak

                              Reagrding getting the electronics wet: The most of the electronic parts of the motor are in the lower unit - wet all the time.

                              If you keep your boat where you can plug it in to charge, a built in battery charger is a great convenience. I looked at Guest chargers - they have alifetime warranty against water damage, probably all "marine" chargers can withstand water.

                              A sealed battery wouldn't leak acid, in fact AGM's can be used in any position except upside down. I would definitely not want a wet battery (where you can unscrew the caps to add water) in any boat. They vent hydrogen when charged and could (would) spill sulfuric acid if rolled far enough over.

                              What about any sailboat with a 12v system getting knocked down? 12v safety isn't your biggest problem right then!
                              Last edited by mcdenny; 08-22-2011, 03:41 PM.
                              Denny Wolfe

                              Comment

                              • stuckinthemud
                                Senior Member
                                • Jul 2010
                                • 161

                                #45
                                Re: inboard electric-powered kayak

                                Been doing a fair bit of reading up on this over the summer, seems that large props(about 9X9) of an aircraft-type pattern similar to a world war 1 scimitar shape, moving slow (up tp 500rpm) are the way to go, perhaps in a kort nozzle and wired to a LRK type motor. And then I got this month's WB and Thiel's go-slow work so time for another rethink....

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