Chris P
On 31 Jan 2018, at 1:57 AM, Hannu Venermo gcode.fi@gmail.com [electricboats] <electricboats@yahoogroups.com> wrote:
On 40ft loa, you probably need 2 kW - 2.5 or so on a cat/tri for 5 knots+.
Feasible yes, maths great, plan great.
5 kW is huge and will give you great power and even some airco if you want.
One comment/issue maybe:
The very large 32 sq m panel will have huge wracking and tilting and pushing loads in heavy winds - since it is high up and has a big moment arm.
Think 10-20-++ tons, metric, twisting the boat.
A thick torsion box is probably best.
Thick means the vertical-direction sides and stiffeners / ribs need to be tall, not necessarily thick or heavy.
Criss-cross honeycomb, perhaps 25 cm tall.
Plywood would work fine, and you could even have it with large holes for air passage.
Laser-cut, cheap, epoxy impregnated.
Air spacers or gaps might be good in the top structure.
I would plan for main support pillars in say == 150x8 (-6) mm steel tube.
Any steel blasted, and properly painted, or 316L if You can afford it.
If at all possible try to have low free unsupported span, or a central support.
And very very strong mounts well-tied to the structure.
Consider a gust tilting the boat, and the top structures edge going into the water at 6 knots.
You would want the structure to be streamlined and not a ram.
Even then, probably 5 tons++ of force acting on the edge of the structure in a twisting action.
Alternatively, struss structure like construction cranes.
You could use commercial steel prefab pieces, cheap and strong.
Air would pass, and a water contact would have less load.
It might be possible to have somewhat different heights on the panels, perhaps allowing most of the air to pass instead of acting like a big wing or sail.
I would probably use linear guides, and have some, maybe 1 outermost set, of the panels be retractable on the edges.
Just sliding below the other panels.
316L supported rod, igus plastic linear bearings, ideal for this.
They will resist salt water, salt grit, etc and not rust.
The problem with a big flat rigid plane up top is wind catching it ..
and the more it tilts the more force it has.
This has the potential to flip the boat in a second until the top edges touch water, even in calm conditions, with a moderate gust.
On 17/01/2018 07:25, chrispurkiss@bigpond.com [electricboats] wrote:
Hi all. First post. I'm a sailor from Australia. Currently own a nice sailing catamaran that i built. As i get old it is too hard to hoist the main sail and all the trimming and reefing gets too hard. I am planning on building the perfect sailors motor boat basically i am looking at replacing the sails with solar panels. The design will be a trimaran for stability and to make a hull shape that is very slippery. Looking at approx 40 foot LOA with 16 foot BOA.
I hope you guys can check the maths to see if i am being too optimistic in my assumptions.
Area of solar panels 32 sq meters - gives 5 kW system - in low tropics gives 20+ kWH per day.
Propulsion by twin motors in the amas say 10 hp = 7.5 kW gives cruising speed 5 to 6 knots.
Battery pack similar to the one in a tesla car 75 kWH weight of batteries 540 kg. Total weight of boat 3 ton with back up 10 kWH generator for extended cruising.
Does this seem feasible? Does my maths add up?
Chris P
-- -hanermo (cnc designs)
Posted by: Chris Purists <chrispurkiss@bigpond.com>
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