Talador
You are roughly right. You need to remove the big rudders, ensure the hulls are smooth and free from scum and keep windage low.
knots is a measure of speed equivalent to nm/hour.
The 200 gallons of fuel increases the weight significantly so you will be slower initially.
My ideal long range cruiser would be a solar powered stabilised monohull. The energy is delivered to you free every day so range is only limited by food you cannot catch.
You are actually better off using a stabilised monohull configuration like the LCS Independence than a proa. I have designs that I have built to 5th scale model that work well to demonstrate the potential:
An 8m fishing boat:
At full scale and design displacement this will do 16kts with 15kW. Will achieve 8kts on solar alone in good sunlight with sun overhead. Has a range of 30nm at 12kts on battery alone - a lot further at lower speed. It can be built light and needs to be light to get that range. It would have a 200kg battery for ballast and be self-righting with cabin closed. The model lists in a good side breeze but this would be less significant in full scale. The model does 10kts, which scales to 22kts meaning it is running above design speed at full throttle hence the foot of the stem is a tad higher than it should be. The model s displaying more dynamic lift than the full scale wound have at design top speed. Notice that its acceleration is rapid and progressive without any indication of a planing hump typical of a wide planing hull.
This is a 5th scale 7.5m runabout:
At full scale this is cabable of 15kts with 4kW. Will do 8kts on 700W solar alone with sun overhead.
I had a solar electric design that competed in the E-340 last year that was faster than any other boat but stuffed the prop on a log about 100 mile in. At that stage it was approaching dusk and he had not started to suck from batteries. He carried enough battery energy to cover the whole 340 mile at 6mph through the water.
This is based on my Twin-8 pedal boat design. It was a low cost build using heavy rigid solar panels. It was never taken to full speed as it was built and operated to go the 340 mile first time it was put on the water. It would not turn very well at speed but is capable of 12mph through the water on a 24V system supplying the small motor mounted off the side of the foredeck. Motor becomes torque limited over 12mph. It is direct drive to a my standard folding prop that is also borderline at that speed.
I have a solar race boat design being built in Kanas for the E-340 - not sure if it will be ready for the 2015 race. It is an all-out solar river racer capable of 16mph (statute) on its 2.2kW of semi-flexible panels.
None of these hulls produce significant wave drag. Roughly 90% of the drag is viscous drag, which goes up with the cube of the speed. Likewise it drops ff with cube of the speed meaning halve the speed and distance on a charge goes up 8 times.
The right hull with solar panels can be an impressive performer with unlimited range:
These give an idea of what is possible. I prefer slender stabilised monohull to foils because the foils are more prone to damage and fouling than a hull.
Rick
On 26/03/2015, at 1:55 PM, "taladorwood@yahoo.com.au [harryproa]" <harryproa@yahoogroups.com.au> wrote:
Rick - "The 800N is for a 4 tonne proa with 18m lw hull at 4m/s; in calm sea conditions, no windage, perfectly smooth glossy hull, no in-water appendages like pods or rudders. Basically it is what you would get in a tow test with a 4m/s tail wind."
I see it as 3200N now : )4m/s is close to the square root of the 18m hull length, the most efficient point for a displacement hull.A single 2 tonne hull would need 1600W or a little over 2.1 hp to go 8 knots or .11 gallons per hour or 72 knots per gallon. At 60% efficiency that would be 43 knots per gallon.Therefore a single 8 hp engine should easily be able to propel the proa at 8 knots in calm conditions? And get better than 18 knots to the gallon?If that is accurate I think I could make a very strong case for scrapping the sails and just using an engine. A 200 gallon fuel tank would have a 3600 knot range.Talador
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Posted by: Rick Willoughby <rickwill@bigpond.net.au>
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