PET bottles based catamaran from wood - solar charging

Hi,
This catamaran (you can find a short video about the catamaran here: https://www.youtube.com/watch?v=GaI47gZ66QE )was planned and built by me. The boat has an electrical engeen, and I'm planning to make a solar charging. The boat has an enginee with 46lbs. How big solar do I need? Could you help me, please? The battery is 86Ah big.

 

Its quite impossible to answer your question.
Trolling electric motors are rated at static thrust (lb or kg) which is not a good way to report power. Also we have no idea of the efficiency of the motor, the resistabce of your hulls etc.
I think the best way is to borrow a pinch style (looping pluer thing around the power chord) ampmeter. Measure the current at your desired drive speed (might be full power but anyway). This way you know how much elctric power is used. Then you need to think what range do you want and how much of it you assume to get from the solar panel(s) during the use or if panels are more for charging the battery.
Remember that a panel is not going to give its rated power in practical use. Try finding info on actual average outputs on panels in your area. (installed panels are often aligbed to south which is hard to do on a boat).
Also remember that a lead acid battery doesn't like deep discharge. So out of 86Ah you shouldn't count on using more than 60% before full recharge.

 

Hi, thanks for the quick replay. I would like a panel, which can charge fully the battery during the working days. It means, that the boat will be used only at the weekend. The engine has 500W power.

 

86Ah at 60% = 51,6Ah to use
Energy at 12V is 51,6 * 12 = 619 Wh so you can run a little over an hour if 500w is correct.

Now check what is expected energy from solarpanel in your area. 80w is probably plenty if it has several days to charge.

 

Your hull shape is very inefficient.

 

Ok, thanks. I'm understanding now how it can be calculated

 

welcome to the forum Asbar!

That is a really cleaver design, you made excellent use of low cost materials to make a decent fishing platform or picnic and swimming float. I like it, very well done.

However as a boat those sponsors are very draggy and really slows your movement. Even square cut logs would be better. As a float it is fine, but if you intend to drive it you need to rethink the hull design, particularly with such a low output motor.

I suggest using plywood to build new floats, with a better prow front. they can be simple framed boxes, seal and screw plywood sheets to the frame, and put 7 or 8 layers of paint on it. you might also put watertight bulkeads in it to create floatation chambers. It will be fast and easy to build, and will allow you to go much further on your electric charge, more than doubling your range. it can also be built with planks, but that will take a lot more sealing and add weight, but might cost less. Any plywood should work, as long as it has waterproof glue. six mm should do it, or go with 10 or 12 mm on the bottom, and six mm on the sides and deck. You can reduce your framing lumber down to 38x38 mm (1.5"x1.5") so save some weight too. I would not go any smaller with low cost lumber, if you use marine quality lumber you can go smaller still.

Add one more battery to your installation and you can motor for about two hours. Add a small mast and a simple spinnaker or square rigged sail made from a plastic tarp for going down wind, and you will increase your range even further using "wind power".

Good luck

 

Hi Petros,

Thank you very mutch for your suggestions. This is my first boat, that's why I used the cheaper wood. I did not know, it will work or not

I think, the wind-energie is a very good idea for this solution. I will think about this.

The engine: I will change for a bigger, but for the test of the boat it was enought.
The boat is planned for fishing, and for my familie: in the cabin (2000mm#1250mm) the sleeping is possible also

Sandor

 

I think this boat can be very, very dangerous for passengers.
In another thread started by asbar_marta you can see more details and there is a video on it.
In my olpinión, we should not encourage this man embarking his family on that boat.

 

Hi, i checked your photo galery, there are some very nice designs. Unfortunatelly I'm a beginner in the boatbuilding. When you have some ideas how can I make better, please share it with me. Thanks for any suggestions!

 

As a first step, you should follow some ot the advices given by Petros in post # 7.

 

Following on to TANSL advice, one of the biggest dangers would be being helplessly blown into shipping, or onto rocky shores, or out to sea - when the wind pushes your very square design, and you do not have enough power to steer where you want.

 

Yes, that is going to have a lot of resistance. A trolling motor will barely move it when there is no wind. I think that an anchor ready to be deployed will be a necessity.

 

what you have is suitable to float around on small lakes, or other inland calm waters, near shore, on days without much wind. Use it as a swimming or fishing float, with an achor as suggested, and never go further from shore than you are willing to swim. If everyone keeps their life jackets on, and you have a suitable tow rope (that can also reach the shore, You and your family should be fine.

If you want to motorize it build some proper plywood hulls more suitable for boat intended to be motored around, not a float.

 

and make sure the doors can be opened by kids in full panic.

seriously you don't want someone trapped in there if things go wrong.