Sepetmebr 9, 2006
September 9, 2006
Human Powered Ocean Crossing Boat Design
Introducing the CapCat
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.
A word about your designs. Lovely ideas. Having pedalled 6,500 miles on the ocean I look at the idea of remaining so beautifully stable with great envy!! I'm no design expert, so Alan Boswell or another marine architect's opinion is more valuable than mine, but my two pence-worth of advice is to keep it simple. Build a nice sleek, strong monohull, enclose yourself inside a cockpit you can seal but also give you plenty ventilation when you want it. Pedal power beats rowing power every time - I'm sure you'll be able to beat any rowing record over the same route. Use bearings and solid shafts to transfer power from feet to prop - not chains. Build a stainless steel version of the MicroMarine units we used, so you can easily replace and repair. Monohulls are horribly tippy and uncomfortable, but a self-righting monohull desgn is safest bet for you. I assume you want to do the northern route from Newfoundland, 2,000 miles. The North Atlantic is cold and the weather can be bad, even in summer. Have a very supportive custom-built pedal seat with racing driver seat belt, and a place to wedge your neck and limbs in tightly to sleep.
The ocean is a terrifyingly powerful place, you can't stop, you can't get off if things go wrong. When I look at your design I see a lot of windage to slow you down and make it hard to steer, I see complicated engineering, three right-angled changes in direction of power to get to the prop, and a lot of elements that could snap or seize up and be extremely difficult to repair at sea. Also I see your prop being out of the water as much in it.
In essence: minimize windage, keep your design low in the water, round heavy hull and light tapering deck and stores stowed low for ballast - all this will ensure self-righting safety. Monohull, enclosed cockpit, all-in-one pedal replaceable units to fit into a central well - thus power delivered midway along hull.
And rich writes:
The ladybird is a nice design. I would say the hull has been
optimised for the speed the rower can sustain in good conditions- say
5mph. It would be difficult to maintain that sort of speed once it
gets a bit rough. The average speed will depend a lot on the chosen
route to take advantage of wind and currents. AND some luck that the
weather is kind.
The concept I have sketched should be possible of sustaining maybe
5.5mph but I would need to check this based on the actual
displacement you think you will need. However the proposed design
should not be bothered by sea conditions as much as ladybird so you
can sustain a higher average. The concept would move very fast in a
following sea with very little effort.
I had anticipated question 1. See previous email.
Regarding question 2. The boat needs to be able to stay afloat and
upright if swamped. It could be made to be self-bailing for the most
part through the open well for the drive leg. It is also a good idea
to have a closed well low down in the hull that collects condensation
and can be pumped out. The whole hull needs to have clear drainage
to the low point. You get a lot of condensation at night after a warm
day so things get wet and uncomfortable if they do not drain.
The 22" width is at the waterline so you can go wider than this above
the waterline. It would be borderline to have it stable enough to
walk around on. I think the idea of an outrigger that deploys from
one side would make life a lot better. It could actually be part of
the bow or stern fairing when folded away. It could have some
netting so you can sit on for washing and calls of nature.
It is surprising how little clearance you need above the waterline in
the centre of a boat to avoid having water come in. I expect you
could operate with the cockpit open for maybe 80% of the time
depending on the chosen route. You would need to have good weather
forecasting to leave the cockpit open while sleeping.
Your body weight will be part of the ballast. The ends of concept 1
get narrow very quickly and you do not want to widen above the
waterline in the ends to allow for sleeping. I would be thinking
about a retractable or folding seat to provide a nice bed.