Human Powered Ocean Crossing Boat Design

Introducing the CapCat
anti-capsizing, wave isolating, energy generating human powered boat.

Here are some video views from the front, and the rear

It is driven by a prop and pedals and rides on two catamaran outriggers. Ocean swells and waves from the side are absorbed by the pivoting outriggers keeping the cabin and prop level. If ocean conditions are severe, and the vessel capsizes, the outriggers simply rotate around the cabin and swap positions with the lower set of hulls. The constant rocking action can turn an electric generator to store power for radios, water maker, and other misc electronics.

An alternate version of this concept is to use three triangulated hulls rather than four:

A higher resolution version of this animation is here

And a third version of this concept is to eliminate the third hull and in the event of a capsize, one hull section can be manually rotated back into the water. A serious technical problem to this approach is that once the hull has been rotated back onto the water, it would need to be rotated further to lift the heavy cabin up and then locked into place to match the original geometry. I'm not sure how the operator would lever his power to lift the entire boat up 2 or 3 feet. This animation shows a capsize, but does not show how the lifted hull would rotate back into the water.

Possible Advantages:

1. Narrower catamaran hulls may be more efficient than a single mono-hull featured on traditional ocean rowing vessels due to far less displacement. According to a study by The International HISWA Symposium on Yacht Design and Yacht Construction, they found that the most efficient hull design for a long distance water bikes is a catamaran or a slender mono-hull. The traditional ocean rowing boat is a mono-hull, but most probably not a "slender mono-hull".

Further evidence that multi-hulls are more efficient than single hulls is the fact that all longer distance human powered boat speed records have been set with multi-hulled boats.

2. Because the catamaran hulls rotate around the main cabin, the cabin will never capsize.

3. Because the cabin won't capsize, this design does not require a heavy, draggy keel or center board thereby improving efficiency.

4. Vastly increased comfort for the operator due to some of the rocking motion being reduced by the pivoting cabin.

5. The electric power generation from the rocking motion of the catamaran hulls around the main cabin could eliminate the need for wind and/or solar generators.

1. If the constant movement of the pivots combined with the harsh sea water environment were to corrode or damage the pivots, then the main cabin could flip over with a capsize, and power generation would stop. This could be resolved by ensuring that there is a over-ride mechanism to turn the cabin manually in the case of a pivot malfunction. There should also be some form of power generation back-up like a solar panel or wind generator.

2. The force of the hulls hitting the surface of the water upon a capsize could damage the hulls, struts or cabin - especially in the case of the quad hull version.

3. The aerodynamic drag of this design would be greater than a traditional mono-hull because there is more surface area exposed to the air. However, at typical speeds of a few knots, aerodynamic drag is a very small factor unless powering into a stiff head-wind. Because the cabin and one or two catamaran hulls are up in the air, the wind could catch it and blow it over causing unwanted hull rotations. This risk is greater with the tri version than the quad version.

4. The weight of this design would probably be greater than a traditional mono-hull and could be slower and less efficient because of this.

5. It is possible that with the drag of the prop and strut, an ocean swell would rotate the main cabin section almost as much as the catamaran hulls are being rotated thereby negating much of the wave isolating pivot effect. The side profile of the prop strut should be as hydrodynamic as possible to allow it to slip sideways through the water.

Rick Willoughby wties:

Greg

I will make sure I give you dimensions in British units. 600mm is

only 2 feet. A narrow hull. Just wide enough to get the shoulders

into. The boats I build are just over 1 foot wide at the waterline

but they are only intended to displace 200lb or so.

The stability is a matter of getting the weight low enough and having

buoyancy up high. A sphere with a small weight on the surface will

float with the weight down. The boat I am thinking of would have an

offset ellipse X-section at the cockpit. A rounded bottom coming up

to a beam of 2 feet at the waterline, a little bit wider above the

waterline to give shoulder room and then narrow above the shoulders

to take in the head.

When you are in the ocean the water is rarely level so a boat that

relies on gravity for stability rather than hull form is often

better. You could set your drive leg up to get weight down low to

help with stability. You may even add some ballast below the prop.

It would also be handy if you can lift the drive leg out of its well

to inspect and work on. Something like Warren B has done with his

Necky Kayak.

You would need to strap into the seat in rough weather so that if it

rolls you stay in the right place. For sleeping you collapse the

back of the seat. You are then even more stable because the weight

is lower. Again strap in so the boat can do a complete roll without

you smashing the canopy.

I am not sure if you are aware but sailing monohulls are normally

designed to have a positive righting moment throughout a 360 degree

roll (apart from the 180 position). Some modern ones with flat decks

are stable upside down and this is a safety issue. The small boats

in the Sydney to Hobart ocean race might roll through 360 degrees up

to 4 times in a race. The bigger boats often destroy masts if they

suffer a complete 360 but they usually get upright and stay afloat.

I am certain that if you continue with this adventure you will be

thanking me that I talked about righting moment and it is a design

feature of your boat when you are facing 5m cresting waves in the

middle of the night 1000km from anything. You need a very large

multihull to feel secure in such conditions.

The boat would be built for speed and is not intended for lounging

around. It is intended to work well IN water and not designed for

sitting ON the water.

Another advantage with pedal power is that you do not need to operate

a paddle over the deckline. In fact you can site below the deck. If

the deckline of kayaks was made higher then you would start to

improve stability. It becomes more like a Canadian canoe with high

sides.

I have attached a sketch of this concept. The proportions are not

correct but you should get the idea.

Draw it up and seek comment from people on the IHPVA boat site. I

think it will look fast. The hull needs to be about 500mm wide at

the crank so you have clearance for the pedals and heels.

Rick

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