So I want to build an electric kayak

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AmpEater   10 W

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So I want to build an electric kayak

Post by AmpEater » Jun 20 2010 10:51am

Kayaking is awesome. Its a simple fact. But, like most things in life, I find myself wanting to incorporate electricity.

Tragically I lost my (crappy) kayak in a big flood about 2 years ago, and I've been wanting a new one ever since. I've got some money set aside, but I haven't made any decisions yet. My main criteria are that it allows for the mounting of an electric drive system. Also, I'd like to be able to bring a dog or two with me (which points more to a canoe, which I've never liked, but I feel like with a fairly powerfull electric drive my feeling might change). The way I see it my drive options are;

Trolling motor. I have 3 of Minn Kota 1.3kw 36v trolling motors from an ebay find, with they weigh ~20lbs each and are made for pushing much larger craft at low speed. They also have no mounting provisions at all. I feel like these aren't really suited to a kayak or canoe, more like a houseboat or pontoon boat.

Through-hull propeller drive, similar to what is used on RC boats. I could use a small, light, but super powerfull motor like a big turnigy and an RC boat ESC....but I have zero familiarity with through-hull seals or proper prop selection for such a thing. My understanding is they typically use very small props at high speeds which may cause cavitation if used to push a large craft at slower speeds.

Electric (airplane) propeller drive, similar to a fan boat. Light weight, no water contact with any moving part, zero off resistance, and simple direct drive. Downside may be lower efficiency and loud noise.

Paddle wheel, easy to build, could be powered from drill motor or geared down RC motor, fairly lightweight with good power handling ability. Downsides are lots of off resistance, and it would look funny, lower eff. than a modern propeller. May cause launch issues.

It seems to me like the simplicity of a direct drive airplane propeller wins. And a just a few pounds it would have virtually zero effect on the portability of the craft. The sound may be annoying, but with a motor capable of 3kw vs a human 100w I feel like the fun factor would be worth it. Plus, there should be no speed limitation within the range likely to be encountered, versus a trolling motor which very quickly reaches it's design speed.

SO....which motor and propeller combination is going to be best for my situation? Battery will be 8s, or 16s if a suitable controller exists. I know larger, slower props typically have higher efficiency. Turnigy? Astro? I know there are some RC guys here that can help me out

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Lock   10 GW

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Re: So I want to build an electric kayak

Post by Lock » Jun 20 2010 12:25pm

Hard to support the weight aloft of a prop and motor and spar etc to hold it up, without adding akas (outriggers) a la trimaran...

Paddle wheels have come up before here:
http://endless-sphere.com/forums/viewto ... 05#p153400

I am interested in air props also, but on a picnic boat-sized catamaran... Check out the threads on flying for some idea of the state of the art for e-flying as far as motors and props are concerned. Yer correct, a larger and slower prop will be more efficient but at some point the diameter becomes impractical.

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Re: So I want to build an electric kayak

Post by hydro-one » Jun 20 2010 12:28pm

GREAT IDEA .......r/c motor in hull. prop or jet drive. Aircraft prop style way way to noisy and annoying in what would be a silent journey IMO.
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Re: So I want to build an electric kayak

Post by AmpEater » Jun 20 2010 1:10pm

hydro-one wrote:GREAT IDEA .......r/c motor in hull. prop or jet drive. Aircraft prop style way way to noisy and annoying in what would be a silent journey IMO.
Any info on setting one up?

It would be the ideal system, IMHO. But there just doesn't seem to be alot of into out there (maybe I am just searching for the wrong things). Plus it requires you to drill holes in your kayak in a non-reversible way, but I can get over that

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Re: So I want to build an electric kayak

Post by Lock » Jun 20 2010 1:14pm

AmpEater wrote:Plus it requires you to drill holes in your kayak in a non-reversible way, but I can get over that
Not necessarily so if you make it a "long tail"
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Re: So I want to build an electric kayak

Post by hydro-one » Jun 20 2010 1:44pm

that looks super simple!!!!! i need an r/c motor !! and a kayak!!!

Use a flexible auger drive for a bigger motor/less obstruction.

im sure these r/c boat guys have some drive system you can adapt......oh and water cooling is easy!! motor and controller.
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Jeremy Harris   10 GW

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Re: So I want to build an electric kayak

Post by Jeremy Harris » Jun 20 2010 4:23pm

The really important thing to bear in mind is that with a canoe/kayak you have a very easily driven hull, that doesn't need much power to propel it, and you also need to keep the weight down, as reducing the weight reduces the wetted area and so reduces the power needed.

A reasonably fit paddler can deliver a sustained power of around 50 to 100 watts. If you only want to go at typical canoe/kayak speeds then this is the sort of power level your looking at. As power determines weight to some extent (more power = heavier batteries for a given endurance) it really pays to look long and hard at efficiency.

You have several options, here's a list with some typical propulsive efficiencies:

Paddle boat type system - typically around 40% at best, unless you make the paddle wheel diameter quite large, when you might get it over 50%.

Air propeller - A big diameter (around 4 to 5ft) air prop might get you up around 65 to 70% efficiency, if you turned it slowly and carefully matched its pitch to the needed power.

Water propeller - Efficiency will depend on the number of blades, prop diameter and blade loading. The fewer blades the better, the bigger diameter the better and the slower rpm the better, as a general rule-of-thumb for this kind of boat. I;ve tested a few props for a very similar project to yours (see the electric boat thread) and have found that an 8" diameter x 6" pitch two blade marine-type prop was only about 40% efficient. My current prop is a 13" diameter x 12" pitch prop that looks just like a model aircraft one. Its a bit over 80% efficient.

A Thai-style long tail drive will work well and is simple to build. Use a low Kv motor and a reduction drive, perhaps using off-the-shelf HTD toothed belts as I've done, and a model aircraft prop (something like a cheap APC 12" x 10") and you should get much better results that using a trolling motor.

You might want to look at just changing the prop on a trolling motor for a model aircraft one and seeing how it works. I have a long thread running on the Boatdesign forum where one member, McDenny, has done just this with pretty good results. See here: http://www.boatdesign.net/forums/boat-d ... post302305

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Re: So I want to build an electric kayak

Post by AmpEater » Jun 20 2010 10:02pm

Wow, thanks for the detailed reply. I never would have thought to try an airplane prop on a trolling motor! I remember years ago trying to cut down a geared RC setup so it wouldn't bog down so much, but obviously that didn't work or I wouldn't be asking this.

I'm definitely going to look into that, thanks

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Re: So I want to build an electric kayak

Post by PedalingBiped » Jun 29 2010 2:11am

You could try to reduce the wetted area ....

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Re: So I want to build an electric kayak

Post by AussieJester » Jun 29 2010 2:31am

^^^ very cool....see Jeremy they didn't even need to use motors in the Scrap Heap Challenge hydro foil ep they could of gone with human power and a kayak build :mrgreen:

Few weeks ago a fella here fitted a big turnigy motor to his whipper snipper looks pretty much like that ICE engine setup hanging off the back of the kayak.

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Re: So I want to build an electric kayak

Post by KTP » Jul 20 2010 8:51pm

Well, it wouldn't really be *building* but you really can't beat the completeness of the Torqeedo kayak brushless motor setup. Maybe you could get some ideas from it at least (it uses a waterproof outrunner style brushless motor with a planetary gear system and a very efficient prop design.

http://www.torqeedo.com/us/sn/image-lib ... light.html

BTW, I have the Torqeedo 1003 much larger electric outboard on my sailboat...it pushes faster than my 2.5hp gas outboard.

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Re: So I want to build an electric kayak

Post by wheelbender6 » Sep 05 2010 2:45pm

I think I would use the long boom setup so I could look like James Bond in Thailand.
"Money can't buy you happiness, but it can buy you a yacht big enough to pull up right alongside it." - David Lee Roth

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boucaneer   1 mW

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Re: So I want to build an electric kayak

Post by boucaneer » May 02 2015 1:34pm

I'm very interested in the these longtail cordless drill trolling motors.
I'm planning to use a Dwalt 995 brushless cordless drill using the middle speed setting at 1,300 rpm with lithium batteries 18 v, 5 amp hour x 4 for the power source.

I'm just trying to remember what size remote control prop to use or what size trolling prop to purchase.

Does anyone have any researched suggestions?

It would be great to solar charge the spare lithium battery whilst under way in the boat with a sun shade solar panel, my canoes are open canoes at 15' LOA with 4' beam with a comfy sitting/sleeping area.

It's a great idea I would like to accomplish, just researching what size prop to use, so any suggestions would be welcomly appreciated.

Great to carry on the conversation.

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Re: So I want to build an electric kayak

Post by boucaneer » May 02 2015 2:26pm

Dear Jeremy Harris,

May I ask, when using your 13" diameter x 12" pitch propeller at what RPM was you running it at please?

On my drill I have three settings, 450, 1,300 and 2000 RPM.
I think I read somewhere that 1,300 RPM is good but my memory is hazy and can't remember where I read that.

So any information about RPM's and R/C prop diameter and pitch attitude would be very welcome.

Thank you guys. :-)

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Re: So I want to build an electric kayak

Post by blisspacket » May 20 2015 7:22am

I'd look at the specs Torqeedo uses, both for sizing the prop and for power needed, and interpolate from there. Or even just buy a Torqeedo prop....

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