Pedal Powered Boats

Hi Tom,

When I started the preliminary design for my boat I started making decisions on what it would do. It had to be capable of being propelled by one person while hauling 600 to 1500 pounds (people, camping gear, food, etc.). I am making a smaller boat now for when one or two people are going out - a lighter boat, light enough for me to carry by myself, faster on the water than my big boat. I wanted to be able to store the big boat inside my garage so a 65 foot hull (typical for a rowing 8) was simply out of the question. The storage constraint limited me to 28 feet. My hull is narrow enough (~20" at water line) that it needs an outrigger or dual stabilizers to keep it from tipping. There is a wealth of information on hulls and construction techniques on this thread. If you have some "what if" questions about hull shape and its impact on hydrodynamics you can analyze the alternatives with Michlet. If you are after an optimal low drag hull you can run Godzilla with your design constraints.

http://www.cyberiad.net/michlet.htm

If you use the "search this thread" feature on "Coach Dave" you will find different posts I made with more details about this boat. For example, see posts 1108, 1325, 1330, 1334 & 1341 for the drive train.

Dave

 

The right angle drill drive units have been tried before and discussed on this thread. See post 1236 - 1240. They are designed for high RPM and low torque. For an efficient human powered boat propulsion using a large prop the right angle drive operates at low RPM and high torque which overloads the gears and causes them to fail. Better take a paddle with you to make it back to shore!

 

What about a scavenged lawnmower gearbox, coach? http://www.youtube.com/watch?v=eSaNVZaUi-k

Porta

 

An angle grinder gearbox can be used, the bigger the better. They are generally a 1:3 ratio, this combined with a bike chainring can give you up to 1:8 gearing. Gear ratio can be altered by the size of the gear fitted to the gearbox.

Ian

 

A typical rotary lawn mover motor runs at about 3000 RPM. The transmission on a self propelled unit looks like about a 40:1 reduction to drive the wheels. I attached a view of a Sears Craftsman 702511 transmission. It uses a worm gear - that prevents it from being used to go from pedal cranks (low RPM) to propeller shaft (higher RPM).

Angle grinder gears have been used successfully for human powered boats. I plan on trying that and see how it works out.

Dave

 

Tom, I added three pictures of my amas. They are 24 feet long and 6 inches wide. The front 4 feet and rear 2 feet taper to a point. The middle 18 feet are a half cylinder (3 inch radius) with 3 inch straight sides. The top of the amas are flat. You can see the profile in the picture. The 5 mm luan plywood bulkheads, stationed every 2 feet, are notched to hold the cedar stringers running the length of the ama. I used 1/8 inch three ply birch plywood stitch and glued to the frame.

One of the pictures shows an end view of the struts (akas) used to attach the amas to the main hull. I used 2 x 3 inch aluminum framing 8 feet long that is normally used to build screen enclosures. Another picture shows getting ready to attach an ama to an aka.

After using these amas for multiple trips I decided that they were much larger and heavier than desired. My second set of amas are 8 feet long, use a single aka (instead of 2), have a flat bottom for planing, are much lighter while providing the same 150 pounds of flotation. That is enough to allow people to stand up on the boat, walk around, lean over the side without tipping over. I've tested them in 2 foot waves but normally I am in more sheltered waters. For a solo boat your amas can be much smaller. 6 feet long and 30 pounds of flotation might be about the right sizing - adjust to your preference.

Dave

 

In the picture showing us getting ready to attach the ama - note that there are 2 akas and one ama. That places the center of the ama about 7 feet from the center of the main hull. I also use the boat configured with 2 amas centered about 3 1/2 feet from the main hull. The single ama is convenient to pull up along side a dock for loading/unloading. The double ama configuration provides more stability which is important if my passengers are not familiar with boats and get scared every time the boat rocks.

Dave

 

Thanks, Coach Dave.

Just interested in the lowest cost, most compact and lightest transmission possible for HP, but the worm is a killer on that mower unit. I heard that angle grinders could be used, but would need a second shaft adaptation at the pedals end? How to do that?

This is the smallest HPB gearbox I have seen, made from a breast drill gearbox: http://www.youtube.com/watch?v=HB13MWTbCuo

Porta

 

Here's something that might work if only that same shaft runs straight through: http://www.kmart.com/schroder-heavy-duty-1-2-inch-rotary-breast-hand/p-00934093000P

I would like to do away with the chain drive to keep things compact, like in the film clip...

P.

 

The Open Waterbike Project has updated and improved its website.
http://www.openwaterbike.com/
The bike chainring connected to a 90deg gearbox mounted on the side and connected to a flexible shaft has the advantage of being easy to fit and avoids any hull penetrations.
Another way is if you can get hold of an Involute gearbox, these are a 1:3 ratio with bike cranks fitted and the shaft connected to the gearbox. With a proa setup it can be mounted on the side and a flexible shaft fitted.

Ian

 

Thanks Coach Dave and Ian.... Great shots of the akas. I have always thought that squarish tubes were stronger than round. Also, I have been following the open water bike project for a while now. My current thoughts are along these lines. Sewer rod (spring steel) approx 5 ft long for the shaft. and either involute or mitrpak gear box, and since I want an oversized boat like Coach Dave, I was thinking about a prop like APC 20x15. So, no thru hull, like Ian said, over the side of the boat and have a strut to stabilize the rear end of the shaft before the prop. Is the ideas of using right angle drives and worm gears just because the mitrbox gear box and involutes are so expensive? Also, I can't get my head wrapped around the 1:3 vs 1:1 on the drives.

Coach Dave... I am not too far from you. I am in Jacksonville, Fl, a mere 2 3/4 hours north.

 

I just got a Mitrpak right angle box that goes for $430 retail for $180.00 including the freight on ebay. There were lots more of various sizes.

If you use a three way, like the involute pictured, you can take it from 1:2 up to 1:9 with just 2 pulleys and a belt. The best belts/pulleys are timing belt types, notched. They offer the least loss due to friction etc. and they are the quietest.

With 1:9 ratio you can use Hydrobikes 12" aluminum 2 bladed prop, bore 1/2", which will be much tougher than a plastic RC airplane prop.

Hydrobike prop;

http://www.google.ca/search?hl=en&s...8.655.11.11.0...0.0...1ac.1.7.img.bcNbIuH4ym8

 

I tried ....

 

Porta,

I found a view of the gears inside http://www.model-engineer.co.uk/forums/postings.asp?th=51063&p=2 There are high speed and low speed gears on it depending on which shaft the hand crank is mounted.

Dave

 

For a low drag solo kayak a 12" prop can readily provide enough thrust. A larger boat like Tom the rower mentioned has more drag and benefits from a larger prop. You can try out different configurations with JavaProp to see what is efficient.

Dave