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Old 18-04-2021, 20:00   #46
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Re: Solar Electric Catamaran Model

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Originally Posted by capn_billl View Post
What size of turbine do you need to generate 10kw in kets say 10 knots of wind?
Thank you for asking. I have been waiting to get into such details until I see how the model works, first by batteries, then by solar panels. Once that has been determined, I plan on going online to see what the latest in wind turbine technology on boats or catamarans is producing. From experience, I have found that developing something that is not based upon the very latest proven technology can waste time and resources. Depending upon what is revealed, I may not include a propelling turbine, although small auxiliary wind turbines for charging batteries might be an option.
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Old 19-04-2021, 07:42   #47
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Re: Solar Electric Catamaran Model

This is a 10kw system.

The rotor is 20 ft tall, and the blades 19ft diameter.

Runs at 3 to 40 knots.

Very comparable to sail area, and works omnidirectional.

Weighs 1,500 lbs, and is 96% efficient.

That's a fair amount of weight on top of a boat, but maybe doable with a medium motor cat.
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Old 19-04-2021, 12:11   #48
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Re: Solar Electric Catamaran Model

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Originally Posted by KnightSailor View Post
What part of “Also, solar panels will be selected for the required voltage, so none will be in series.” Don’t you understand??????

That argument has already been proven to be false. “Sail boats” with wind turbines have been built that sail directly into the wind. That is a fact.
Hint: How do conventional sails create the power needed to move forward in a tack?
Yes, I do understand... You'll have an entire panel out of commission, or more than one if the mast casts a shadow over more than one at a time, which is likely. All I'm say is that I'd rethink the mast.



Go ahead and build your turbine, we'll see what happens. A rotating cylinder is basically a sail, a power generating turbine to drive electric engines, or even mechanically drive a prop is another matter, and maximum efficiency is going to be a little over 50%.
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Old 19-04-2021, 13:18   #49
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Re: Solar Electric Catamaran Model

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Originally Posted by dustman View Post
Go ahead and build your turbine, we'll see what happens. A rotating cylinder is basically a sail, a power generating turbine to drive electric engines, or even mechanically drive a prop is another matter, and maximum efficiency is going to be a little over 50%.
To clarify, when I say Wind Turbine, and am referring to the typical horizontal-axis wind turbine. As I think I mentioned earlier, having a wide, short vertical axis turbine turning overhead was not a good idea. Also, such a turbine would not be very efficient. If I decide to add a wind turbine to the Cat later on, it would probably be several (4 or 6) smaller wind turbines, mounted on the sides of the cabin, and able to be rotated up when the wind is blowing, and the sun is obscured or at night. They could be something like this. One more time, how do conventional sails create the power needed to move forward in a tack? The same principle is how a wind turbine of sufficient size will be able to power a boat forward against the wind.
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Old 19-04-2021, 13:58   #50
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Re: Solar Electric Catamaran Model

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Originally Posted by KnightSailor View Post
Thank you for your concern.
After looking at hundreds of photos of powered Catamarans, the mast is far from common or traditional. Most didn’t have one. Even so, I put it on the model mostly for show, although a version of it may end up on the full size Cat.
I did the calculations and the largest shadow that mast could cast is 2.4% of the surface of the deck. Depending on the angle of the Sun, that would amount overall to perhaps 1% of the surface overall. Therefore the shadow is not an issue.
I suggest looking into how shading impacts solar output. There are ways to compensate but a small amount of shading can kill a large percentage of the output.
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Old 19-04-2021, 15:58   #51
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Re: Solar Electric Catamaran Model

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I suggest looking into how shading impacts solar output. There are ways to compensate but a small amount of shading can kill a large percentage of the output.
First, as I have noted, the mast in the photo was for aesthetic look on the model. The only reason for a mast on the Cat would be for a radar, and that could be put on the back of the Cat, or even on a short but extendable mast.
I have now been researching the issue, and found all the ways to mitigate the effect, including short strings, bypass diodes, etc. At this point, I am not going to worry about that for the full size Cat. However, I will take that into account when and if I put solar cells on the model. The mast on the model is held on with a single screw, easy to remove.
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Old 19-04-2021, 16:05   #52
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Re: Solar Electric Catamaran Model

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Originally Posted by dustman View Post
Yes, I do understand... You'll have an entire panel out of commission, or more than one if the mast casts a shadow over more than one at a time, which is likely. All I'm say is that I'd rethink the mast.
You were right, I was wrong. I was thinking cells, not panels.
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Old 19-04-2021, 20:35   #53
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Re: Solar Electric Catamaran Model

@KnightSailor: Great to post your project here. Accept the constructive criticism/scientific/engineering points. Ignore the criticism. If Edison were posting on this forum and listening to all the comments we would never have had the lightbulb, phonograph, etc.

Best of luck, I truly hope you succeed. I am a big fan and believe sometime between tomorrow and 10 years we WILL have a fully electric boat with using no fossil fuels that can run all day.

I have posted about Greenline Yachts , who make commercially available 30-60' hybrid powerboats. They can do about 6 hours at 4kts purely on batteries. Takes an hour to recharge while running on diesel. But if the solar panels improved by 2 and the batteries improved by 2, it now runs a day at 4 kts. That will happen in the not so distant future. Keep plugging away!
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Old 19-04-2021, 22:44   #54
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Re: Solar Electric Catamaran Model

20 HP = ~15000 watts = ~800 square feet of solar = max HP of a 40 x 20 solar catamaran ... assuming ideal conditions
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Old 20-04-2021, 05:51   #55
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Re: Solar Electric Catamaran Model

Not sure what size/wt boat we are talking about, but I think half that power would be fine for something that comes in at 5k lbs. So now it is 7.5kw. That is 20 panels of today's 300w/panel.

If you could use 3kw, that is 10, and now it 15' x 15'. You probably want a battery bank of equal Ah to Kw, e.g. 3k Ah for 3Kw of power. Not sure if the goal is to cross the ocean or just be able to go out for a day or 2.

As I said above, not easy to do today, but within a decade or sooner.
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Old 20-04-2021, 08:25   #56
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Re: Solar Electric Catamaran Model

As y’all may have noticed, the idea for this Catamaran has evolved and changed a lot since I first conceived it 35 years ago. I appreciate all the input from the members of this great forum. Although a 40’ live aboard Cat would be great, it is more likely to be a 20-25’ weekender. I might even consider a Trimaran.
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Old 20-04-2021, 09:37   #57
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Re: Solar Electric Catamaran Model

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Originally Posted by KnightSailor View Post
As y’all may have noticed, the idea for this Catamaran has evolved and changed a lot since I first conceived it 35 years ago. I appreciate all the input from the members of this great forum. Although a 40’ live aboard Cat would be great, it is more likely to be a 20-25’ weekender. I might even consider a Trimaran.
I think your model has some issues with scale. If it's only 20-25', just eyeballing the pictures, the cabin would only be 3-4' tall. If you made for 6ft standing headroom, it would look very top heavy.

That also implies a much smaller area available to solar on the roof...guessing 8x8, so at 15w/sft, maybe 1000w. If you try to cover the rest of the deck, there isn't much room for actually using the boat.

So figure 4-5kwh per day of electrical production. It's going to be a slow boat.

It would be good to step back and determine what you are trying to build. Size, weight, performance expectations, use case. Trying to design without knowing what you are trying to design, leads to a lot of assumptions that may or may not align with what is in your head.

Doing something like a 10-15ft dingy on a catamaran layout with a solar roof that folds down when not in use and is expected to do 4-6kts for a mile or two roundtrip would be pretty viable without getting into anything exotic and would have a nice purpose.

What would the purpose be for a 20ft cat that is a little too large to be a dingy but not big enough for most cruising uses.
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Old 20-04-2021, 11:41   #58
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Re: Solar Electric Catamaran Model

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Originally Posted by valhalla360 View Post
I think your model has some issues with scale. If it's only 20-25', just eyeballing the pictures, the cabin would only be 3-4' tall. If you made for 6ft standing headroom, it would look very top heavy.
Good observation. I used the fiberglass hulls I had, which are 4 feet long and 4 inches high. That is about 1/3 as high as the hulls would be on a full size catamaran with a cabin, where half or more of the cabin would be below the top of the hulls. The model hulls I have were so shallow, I was concerned about how it would float with all that deck and cabin weight, 10 lbs. Turns out, there is plenty of freeboard, as you can see by the stripe on the model which is the waterline.
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What would the purpose be for a 20ft cat that is a little too large to be a dingy but not big enough for most cruising uses.
When I was a much younger, I considered cruising the oceans in a 55’ Ketch Trimaran out of San Diego. I almost had one built by a company in Vancouver. At 74, and having had many injuries, a catamaran like this would be more suited to perhaps running up and down the Intracoastal Waterway, the Florida Keys, close in along the Gulf of Mexico and maybe the Mississippi.
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Old 13-05-2021, 17:21   #59
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Re: Solar Electric Catamaran Model

I did a test run of the Catamaran Model. The motors and controller only allow full throttle and only in forward One motor on each hull allows forward when both motors are run, and turning when only one motor is run. The proportional controller I bought was defective.
Otherwise it sit in the water fairly level, and cruises pretty good. I might shift that cabin forward about an inch.
Cruisers Forum will not allow upload of the 1min video.
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Old 14-05-2021, 16:12   #60
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Re: Solar Electric Catamaran Model

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Originally Posted by KnightSailor View Post
I did a test run of the Catamaran Model. The motors and controller only allow full throttle and only in forward One motor on each hull allows forward when both motors are run, and turning when only one motor is run. The proportional controller I bought was defective.
Otherwise it sit in the water fairly level, and cruises pretty good. I might shift that cabin forward about an inch.
Cruisers Forum will not allow upload of the 1min video.

Can you upload it to youtube and then post the link? Be keen to see it. Always good to have a project.
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