Picture of Sit On Kayak Pedal System
Made from a sit on kayak, a bicycle, weedeater and assorted parts, this water-craft is relatively easy to build, great exercise and fun!
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Step 1: Gather materials

Picture of Gather materials
1 sheet of 2" blue insulation foam (4 ft X 8 ft) (or sit-on-top kayak)
1 bicycle (or 'Big Wheel' trike)
1 old 'Weed Eater' or weed whacker of any make
1 wooden or plastic model aircraft propeller (mine's 18 X 12 but somewhere in the range of 10 X 10 to 16 X 16 should do)
1 3/8 drive 90 degree drill chuck
various and sundry wood and metal bits to connect it all

Step 2: Construct Foam Pontoon Boat

Picture of Construct Foam Pontoon Boat
Insulation foam is relatively easy to work with and makes a utilitarian pontoon boat. (working on Instructable for my new design)
Alternately follow these directions (Dual-Motor SIP&PUFF Controlled Kayak System or

Step 3: Construct Propeller Assembly

Picture of Construct Propeller Assembly
Disassemble "Weed Eater" to get to the flexible shaft assembly.
Remove the weed whacker head and attach propeller.

Step 4: Mount Bicycle to Pontoon Boat

Picture of Mount Bicycle to Pontoon Boat
Use bamboo supports to mount bicycle to pontoon boat

Step 5: Position Propeller Assembly

Picture of Position Propeller Assembly
Position and mount propeller unit to the bicycle/pontoon boat assembly using U-bolts to clamp it in place

Step 6: Pedal Away

Picture of Pedal Away
Find a pond/lake/river deep enough for your boat/propeller and pedal away!
(Pictures of finished project ASAP!)
whaT IS THE MAKE AND MODEL OF YOUR tricycle thingy?
tropidavo3 years ago
HI Leon , This is just the thing Ihave been looking for . I want to adapt it to my 3 x 7 foot pvc raft. Instead of the prop Iwould like to use a pvc paddle wheel. Does anyone have a simple plan for that? thanks, tropidavo
Maybe you could try something like this:

or this:

Just make the blades shorter. Hope that helps.
I'd try really hard to use the propeller over a paddle wheel. It is way more efficient.
cjbikenut3 years ago
This looks great. Could we see the finished project please?
l8nite3 years ago
is this supposed to pull or push you thru the water ?. I hope you continue and take a lot more pics, Ive been considering something like this for a couple years now
kuhldad3 years ago
Congrat! I was considering a similar design but decided it was too difficult. I've decided to try a paddle wheel system using a trike.
bertus52x113 years ago
Very nice!
I have been struggling with this for a while and then put the project "on hold" (and continued with my other projects).

Can you tell what a weed eater is? I'm very interested. Secondly, I have a similar propellor lying around here and I always assumed that it wouldn't be strong enough. Are you using it without any glass fibre / epoxy coverage?
Weed Eater is a product trade name for a landscaping tool also called a string trimmer. They work by spinning a length of replaceable nylon "string" fast enough to cut grass and weeds, hence the name Weed Eater. They are used to get close to items in a lawn or in areas that are inaccessible to larger mowers like steep hills.
Thanks, I understand now.
LeonArchiTesla (author) 3 years ago's a kayak...NOT a pontoon boat but...the foam boat's not done yet so I just put the pedal assembly on my it says you can in the instructable...and there you go! Video soon!