# RC Solar powered Boat

Discussion in 'Boat Design' started by Zain, Dec 19, 2013.

1. ### Baltic BanditPrevious Member

And with that design it won't work

2. ### Baltic BanditPrevious Member

that won't work. at all. The reason is fairly simple Surface friction drag goes up as the square of the immersed surface area

Form drag is roughly linear for speeds in knots up to roughly the square root of twice the waterline length in feet after which it too becomes quadratic as the boat has to plane.

For sub-planning speeds, empirically the ideal form is a symmetrical double ended form that has an aspect ratio of roughly 22:1. any aspect ratio lower than that has higher form drag, any non-tapered stern has higher form drag

Now for non-planning modes surface drag has a fairly low coef. and water is quite dense so it doesn't take much surface (assuming close to cylindrical optimal) to float something. So as long as you have an optimize form, you aren't doing too badly.

a) has a lousy aspect ratio so its form drag will be higher
b) has a lousy stern shape so its form drag will be higher
c) if limited to 1m long - is limited by the equation of

.54 (sqrt (2x3.3L) ==> KPHmax = 1.38 x L2WATERLINE_in_METERS

So you are limited to 1.38 KPH with a 1m model if you want to make it solar powered.

If you already have the model, just try it. put it on a tow line behind a row boat. attach the tow line to a moderately calibrated spring scale (the kind you use to weigh groceries at the store) Turn on the GPS on your smart phone.... have one person start rowing at a steady fairly slow pace. have the observer verify the GPS speed over a 10 second average, and have a second observer note the amount of drag in pounds (or kilos) the model is generating. you will find its quite high for even for the range of 2-8 kph. way more than you can generate with solar cells that can fit on that hull shape.

there is a reason why racing catamarans ALL and I mean ALL have a 22:1 beam to length ratio. and while mono-hulls appear to be different when sitting flat at the dock, most are designed to be sailed heeled at an angle that changes the actual shape that is immersed in the water to try and approximate that 22:1 ratio.

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### SamSamSenior Member

There is no evidence Zain understands anything being posted. I think he wants a set of plans and instructions.

I wish the internet had been around when I was going to school, it would have been much easier.

4. ### Baltic BanditPrevious Member

I'm starting to think that's true.

Zain do you really not understand the fact that your hull is wrong for what you want to do?

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### ZainJunior Member

baltic i am not english speaking....i understand some of the thing and some of thething not...the things i understood are
According to you to make a 1m boat
1.the hull should b dual not mono because of the wideness of the solar panels
2.the motor should be of 1hp
3.19 solar panels should be used in which 1 solar panel should be of 40 watts to run the motor
am i right??

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### ZainJunior Member

forget my dimensions and speed...coz i said it before that i dont have any knowledge about the boats and their designs..i just have a rough idea....i thought its too easy but after getting into this forum i just felt its not an easy task to build a boat and drive it on the canal.....So Baltic according to you what should be the minimum length and maximum width of the boat to drive the boat at reasonable speed...and we are using a charger and batteries too...so which batteries should we use....i mean dry batteries..?? capacity of the batteries?? volts of the batteries?? and one thing more if u can use simple english instead of scientific one.. thanks in advance..

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### ZainJunior Member

yeah dear i want a set of plans and instructions because i dont have much knowledge about it...but we have to complete our project to get the engineering degree....

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Zain; Does your teacher say that the boat must be one meter long, must travel at 15 to 20 Km/hr, and must be solar powered? If that is true, then your teacher knows nothing of boats and the hydrodynamics that govern them. Or he/she may be playing a trick on you.

Baltic has given you the necessary formulae based on the laws of physics. Those laws cannot be changed no matter what the teacher says.

As stated in another post; "It is not going to happen". We are sorry to disappoint you and your teacher.

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### ZainJunior Member

No my teacher didn't said that...it was just a rough idea by me.....so whats the best and minimum length should we use?

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### ZainJunior Member

This is the sail boat...we can make a simple boat with this type of hull.?

11. ### Baltic BanditPrevious Member

if you want an engineering degree, you need o be able to figure that out

if you want your model to travel a 15kph you have two choices

1) minimum length is 10 meters

2) horsepower is well in excess of what solar can generate without sinking the model

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### ZainJunior Member

Sir!!! Can we use these dimensions and values for our boat which u have calculated above like 1m boat length 33'hull and 1.5m the maximum beam...using 0.6hp motor....0.6m²...with the catamaran hull...???

13. ### Baltic BanditPrevious Member

you want to be an engineer. I gave you equations and sources....YOU as an engineer, need to be able to figure this out

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### ZainJunior Member

Okay sir thanks alot...u helped me alot i will work on it.....

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### ZainJunior Member

I didn't understand the second choice??

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