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Thread: inboard electric-powered kayak

  1. #1
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    Smile inboard electric-powered kayak

    Don`t know whether to post this to building or to plans, but I`ve been reading up on the WWII electric canoe (MSC/Sleeping Beauty), and found they only used a 0.3 hp motor to achieve 3 or 4 knots for up to 16 hours endurance, albeit with some very,very large 12v batteries.

    This made me wonder, if you were to build a solo kayak with an inboard electric propulsion system, how would you do it? Strip-build/SOF/stitch-n-glue/?? and what would be the sort of power system needed, presumably sub 2hp, but aiming to get 8 knots in a burst or work against a tide, and an endurance of 8 hours at 4 knots, oh and it should be light enough to car-top without removing the batteries....

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by stuckinthemud View Post
    ...and what would be the sort of power system needed, presumably sub 2hp, but aiming to get 8 knots in a burst or work against a tide, and an endurance of 8 hours at 4 knots, oh and it should be light enough to car-top without removing the batteries....
    Circumnavigate as well? <-------JOKE!

    Batteries are just too heavy for cartopping (particularly in a kayak!), and you'd probably need more than one for that 8 hour requirement. Start that weight program now...
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Default Re: inboard electric-powered kayak

    Thought that car-topping may be a little optamistic, but still trailering is an option.

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    Default Re: inboard electric-powered kayak

    Car topping is easy if you are permitted to remove the batteries though, It shouldn't be so complicated a system that removing them is a big chore. I guess it's your boat your rules though. IOT cartop I'd forgoe that requirement.

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    Default Re: inboard electric-powered kayak

    Torqeedo has the lightest option. Also the most expensive, but it is made for what you propose.

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    Default Re: inboard electric-powered kayak

    Those Torqeedo's are high tech, high performance, high cost systems and a great way to go if you are OK with the price. You can make your own drive system for 1/4 the cost of the cheapest Torqeedo. Buy the bottom of the line PWM (infinite speed control) trolling motor; cut the bottom off and mount it into a fairing. Use an RC model airplane prop. (10 x 6) worked best for me.

    Do not use a resistor speed control (usually 5 discrete speeds) unless you plan to run the motor wide open nearly all the time. This could work if you used 6 or 8 volt batteries instead of 12v.

    4kts for 8 hrs will take 200 lbs of lead acid batteries of maybe 75 lb of LiFePO4 cells. 8 kts ain't happenin'

    Here's a thread describing my 18' sailboat with a trolling motor modified with fairing and RC prop. http://forum.woodenboat.com/showthre...ower&highlight=
    Denny Wolfe
    www.wolfEboats.com

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    Default Re: inboard electric-powered kayak

    Cheep and cheerful is the way I like it, love the plan Mcdenny.

    Here are the figures for 1943 according to Quentin Rees:
    endurance 12 miles at 4.4 knots, 40 miles at 3.1 knt (about 14hours) from a very slippery hull weighing over 550 lbs with loa 13ft, beam 27in, using a 8in prop running off 4 6v 89amp hour batteries.

    My thought was if the weight was dramatically reduced - their hull was steel - performance would improve, and with modern motors, wouldn`t it improve some more? 8 knts is likely impossible but still a good start for discussion, but is 6 achievable, or has the technology advanced so little in 70 years?

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    Default Re: inboard electric-powered kayak

    You are joking, right? Those batteries weigh over 60lbs EACH. You want to build a lightweight kayak and put 250lbs of batteries in it, then cartop it???? Unless the kayak is heavily built the batteries will break it in half when you hit a bump.

    If you want a small electric launch, build (or modify/restore) one - lots of designs out there, or just mod an old plywood daysailer. Use a boat trailer, fer crissakes.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  9. #9

    Default Re: inboard electric-powered kayak

    I have always though about a powered Kayak would be neat to play with.

    I think it can be done AND keep it cartoppable.. I would estimate 30-40 lbs. WITH lead acid batteries. 8kts is optimistic but you might be able to get close.

    Things have come along way since 1943 with both motors and batteries.

    Check out the Torqeedo Ultralight 402 on page 8, a kayak propulsion system (thanks woxbox)

    http://www.torqeedo.com/fileadmin/us...easures_01.pdf

    Less than 15 lbs including battery, 9km/h top speed, 30km range at 4km/h........

    All from a 230 Wh Lithium battery, the Lead equivalent of about a 12v 20Ah battery.

    a 12v 10 Ah battery weighs just over 8 lbs, and you will need 2. That gives you 10-20 lbs for the motor and controller. I wouldn't go heads up against the torqueedo for pinks, but You could probably beat the 1943 monster.

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    Default Re: inboard electric-powered kayak

    Once again I suggest that you folks check out the Electric Boat forum. http://groups.yahoo.com/group/electr...guid=421621470 All the options are covered- and there's lots and lots of pictures JayInOz

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by Thorne View Post
    You are joking, right? Those batteries weigh over 60lbs EACH. You want to build a lightweight kayak and put 250lbs of batteries in it, then cartop it???? Unless the kayak is heavily built the batteries will break it in half when you hit a bump.

    If you want a small electric launch, build (or modify/restore) one - lots of designs out there, or just mod an old plywood daysailer. Use a boat trailer, fer crissakes.
    Hi Thorne, think you may have got hold of the wrong end of this stick, my question really is to avoid all that weight by building as light as possible and not to use heavy batteries. Since kayaks are very easily driven, they can operate with very small motors and (hopefully) very small batteries to match, wheras even a small launch needs much more power, more batteries, more expense, more hastle. Ideal is to take the boat off the car jump in it and away to go; I just wondered how close to this ideal we could get, preferably for as little cash as possible.

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by stuckinthemud View Post
    Ideal is to take the boat off the car jump in it and away to go; I just wondered how close to this ideal we could get, preferably for as little cash as possible.
    Many thousands of folks already doing just that every day, and a huge industry exists to support them - so do you think you've discovered something they haven't? The pedal kayak designs like the Hobie Mirage sound perfect for your needs. When batteries get vastly more powerful, and motors more efficient, you might be able to do it electrically -- but not with the present tech unless you want to spring for a torqueedo.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Default Re: inboard electric-powered kayak

    I think we've been down this road before, but how far could one go with a fiberglass tank of compressed air running an air drill with a prop chucked in it? Eco friendly, quiet, and not too heavy. More than 1 mile?

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    Default Re: inboard electric-powered kayak

    The comments about electric boat technology advancing reminded me of a little research I did into the ELCO 32' electric launches used as mass transit at the 1893 Chicago Worlds Fair. I found a digitized version of an 1894 engineering magazine giving a lot of specific data collected over the period of the fair - IIRC about 50 boats were in nearly constant use for 5 or 6 months.

    The second latest reincarnation of ELCO electric boats offered a 30' launch very similar to the Worlds Fair boats. Its performance - both speed and range - was about the SAME as the boats from 120 yrs ago. The electric efficiency of the batteries (they called them piles back then), motors and speed controls (elaborate contactors to alter series / parallel connections to vary voltage) was about half as good as today's technology but the new fiberglass hulls are so much heavier than the old wood ones that the performance turned out about the same.
    Denny Wolfe
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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by Thorne View Post
    Many thousands of folks already doing just that every day, and a huge industry exists to support them - so do you think you've discovered something they haven't? The pedal kayak designs like the Hobie Mirage sound perfect for your needs. When batteries get vastly more powerful, and motors more efficient, you might be able to do it electrically -- but not with the present tech unless you want to spring for a torqueedo.
    Yep, I`m one of them thousands, built a coracle, building an SOF sailing canoe, got a big and very heavy fibreglass sea-canoe (takes two to carry it), but paddling isn`t so much fun after a few hours, so an electric alternative might be be nice, and although sails are easy to get information on, and petrol/diesel-power is stright-forward to get help with too, I know totally nothing about electric-power, except it sounds like a nice quiet way to travel, kind of best of both worlds - a quiet kayak that drives itself when I get tired.

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    Default Re: inboard electric-powered kayak

    My brother built a kayak and embedded a minkota tolling motor in the skeg. Faired it in all nice and smooth. Cut down the upright shaft and ran it up into the hull. Moved the speed control up into the cockpit. I dont recall what type of batteries he used. He used it down at Sanibel Island a good bit. It worked out well. Cheap, Efficient, Easy.

    If you are interested I will see if I can get some pictures and specs.

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by McManusBoatWorks View Post
    My brother built a kayak and embedded a minkota tolling motor in the skeg. Faired it in all nice and smooth. Cut down the upright shaft and ran it up into the hull. Moved the speed control up into the cockpit. I dont recall what type of batteries he used. He used it down at Sanibel Island a good bit. It worked out well. Cheap, Efficient, Easy.

    If you are interested I will see if I can get some pictures and specs.
    Yes please, that would be great if you could

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    Default Re: inboard electric-powered kayak

    While were at it, anybody built their own motor/prop/controller set-up? motors on their own seem to be much cheaper than a complete trolling motor, but I guess if you add up the cost of a wiring harness and speed controller, the costs of DIY kit wouldnt be significantly cheaper?

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    Default Re: inboard electric-powered kayak

    Trolling motors on ebay are cheap, they even have these
    http://cgi.ebay.com.au/ws/eBayISAPI....ht_2287wt_1145
    for project boats, replace the control panel with a servo tester and electronic speed controller (to extend low speed range), I just bought both of these and a couple of props for $16 shipped, from Hobbyking.com
    While you are there check out their LiPo's 5ah 11.2 volt 20C discharge rate about 400g from memory are in the low $20 range, so 20ah will be less than 2kg and they don't mind being deep discharged repeatedly to 80%, just dont discharge completely as it will destroy them.

    Oh, try and stick around the 30lb thrust range as it will drive the kayak at hull speed (may need to play with props for max speed minimum current) with out excess current draw.
    Last edited by Geebee666; 03-19-2011 at 05:26 PM.

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by Mis4tun81 View Post
    I have always though about a powered Kayak would be neat to play with.

    I think it can be done AND keep it cartoppable.. I would estimate 30-40 lbs. WITH lead acid batteries. 8kts is optimistic but you might be able to get close.
    Hull speed for a 17 foot displacement hull is around 5.5kts, so without chucking several horsepower into the equation, 8kts is impossible. Below hull speed though, it doesnt take much power to get along nicely - look at how well a kayak goes when being paddled. The average person is worth all of about 300W continuous. That is cycling, and I am sure my legs are probably good for much more than my arms.

    Check out the Human Powered Vehicle Association website - they have (or had several years ago) a lot of info on really efficient propellers for low speed, low power marine applications - they do look a lot like a model aircraft props but are designed to work properly in water instead of air.


    Edited to add - just had a look at the HPVA site :-(
    It looks like the organisation had a bit of a meltdown some time ago, and the guys who were doing a lot of practical prop testing and manufacture have long gone - I dont know what state the forum archives are like there, but if they still exist there is load of info.
    Google HPV propeller, Jake Free, Spinfin - there is still a bit of info out there and a few places selling props, but most people seem to have reverted to model aircraft props. 16x16 looks like a popular size.

    Pete
    Last edited by epoxyboy; 03-19-2011 at 07:28 PM.
    Don't underestimate the power of stupid people in large numbers!

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    Default Re: inboard electric-powered kayak

    Hull speed for a 17 foot displacement hull is around 5.5kts,
    That assumes a traditional hull with some beam. A light narrow boat can easily do 2x root of waterline, or 8 kts for 16 ft waterline.

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    Default Re: inboard electric-powered kayak


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    Default Re: inboard electric-powered kayak

    Possibly modify this

    http://www.electricpaddle.com/

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    Default Re: inboard electric-powered kayak

    That GlenL looks very similar to the boat my brother built. He is a fan of that source. I bet he modified that design for his purposes.

    I will contact him today and see if we can get some pictures.

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    Default Re: inboard electric-powered kayak

    Try this thread:
    http://www.songofthepaddle.co.uk/for...read.php?16099

    The guy who started the thread is a real engineer.
    Someday, I'm going to settle down and be a grumpy old man.

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    Default Re: inboard electric-powered kayak

    Quote Originally Posted by Woxbox View Post
    That assumes a traditional hull with some beam. A light narrow boat can easily do 2x root of waterline, or 8 kts for 16 ft waterline.
    I know that racing kayaks like K1's go faster than their theoretical hull speed, but everything I have ever seen and experienced on "normal" modestly stable sea kayaks suggests that 8 kts is unlikely. Paddling hard out gets them going fast enough to start suck the stern down - it is like hitting a brick wall. Even a sail and a decent breeze wont get you much more speed.

    I think for the most part, the sort of hull form you are referring to is more likely to be found on a catamaran or downriver race kayak, than the sort of thing being proposed here.

    Pete
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    Default Re: inboard electric-powered kayak

    We've done it already(club acquaintances of mine) using a 16 ft plastic sit on top kayak, a mini kota trolling motor from Wal Mart. 30lbs thrust. Shaft shortened and inserted thru the hull and fixed stationary. Steering was with the kayak rudder. Batteries was a single optima blue top marine battery in a plastic milk crate strapped down in the rear tank well. Im sure it can be installed inside the hull under the hatch. Battery removed for transportation. 5 min hook up. Not a big deal. Easily done.

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    Default Re: inboard electric-powered kayak

    jclays -- Do you have information on run time, speeds, etc., with that rig?

    Pete -- I agree most commercial kayaks are too heavy and beamy to go 8 knots, but if you built one specifically to do this, there's no law of physics that makes it impossible. A light boat with a waterline 12-1 length to beam ration, and a nice clean shiny bottom should do the trick. Yep, that's a 16" beam at 16' on the waterline. But I'll bet 18" wouldn't kill the performance. A very simple and light outrigger could provide reserve stability if the skipper felt the need. The Olympic class kayakers go even faster than that. Here's a link with some actual facts.
    Last edited by Woxbox; 03-20-2011 at 08:42 PM.

  29. #29
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    Default Re: inboard electric-powered kayak

    forget the electric motor. Drop a mirage drive into it:
    http://www.kayakfishingsupplies.com/...e-Drive/Detail

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    Default Re: inboard electric-powered kayak

    Found this while I was searching, any thoughts? www.streamdancer.com As I understood it a propeller (screw) was just a cut-short worm-drive, and more efficient because of lower drag?? So is this worm-drive a ducted fan in a tunnel housing, and where do ducted fans come into all this, they may be more effective on a kayak, since like a trolling motor faired into the skeg, they dont dangle below the boat and bang into the rocks in shallow water?
    Last edited by stuckinthemud; 03-21-2011 at 04:19 PM.

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    Default 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.

  32. #32
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    Default 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.













  33. #33
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    Default Re: inboard electric-powered kayak

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














  34. #34
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    Default 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_.

  35. #35
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    Default Re: inboard electric-powered kayak

    Thanks for the advice Thorne.

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

    http://www.duckworksmagazine.com/03/...cmanus/bob.htm

    Or you can just Google "duckworks mcmanus"

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