RC Solar powered Boat

[Baltic Bandit]

And with that design it won't work

 

[Baltic Bandit]

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.

but your model

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) ==> KPH_max = 1.38 x L²_{WATERLINE_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.

 

[SamSam]

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.

 

[Baltic Bandit]

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.

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?

 

[Zain]

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??

 

[Zain]

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..

 

[Zain]

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.

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....

 

[messabout]

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.

 

[Zain]

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.

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?

 

[Zain]

1hp motor should be fine for doing this with a 33' long platform weighing 50kg

that's 746 watts

So depending on where you are in the USA, https://www.kencove.com/fence/131_Solar+Panel+Calculator_resource.php

So in Seattle you would need about 19 of these panels https://www.kencove.com/fence/Solar+Panels_detail_MSP40P.php which if assembled on top of a 33' long hull will take up 31 ' of it.

so if you build your hull to look a bit like the image below (ignore the mast and the mini hull under it, you will end up with something that weighs about 95kg (80 kg for the panels, 5kg for the motor, 10 kg for everything else)


You will be hard pressed to do 15kph but you should just about make it.

Of course you do need a battery for some power smoothing but you should be able to do it

though my initial swag about the motor being the primary weight factor was wrong. its the panels.

1" diameter CF tubing weights 0.11#/ft so assuming 4 tubes x 33' => 7kg

Wrap it in shrink wrap http://www.usshrinkwrapinc.com/industrial shrink wrap supplies.html which will add about 3# to the whole thing (8kg now) leaving you with 18' of tubing for cross bracing - which should be enough.

And at 90kg you only add about 1sq meter to your immersed surface area. (10cm vs 5cm)

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

 

[Baltic Bandit]

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

 

[Zain]

Well first you need to figure out how much power you will draw at 15-20 kph

And its basically a looped design principle. your optimal displacement hull will run roughly 22:1 aspect ratio, which really isn't stable enough to carry a wide array of solar panels. (but you can perhaps try a very very very long design)

So that suggests a catamaran hull since that gives you arbitrary width for the panels and still lets you have slender low drag hulls.

so then you swag the drag equation for the hulls

you hit a massive drag increase at 1.34 sqrt of the length of the hull in feet (or roughly 2L^0.5) in knots

15kph == 8.1 knots means your lowest drag hull will be 32-33' long. and 1.5' wide at max beam.

that might be wide enough to get you enough surface area for solar cells.

the next step is to figure out the drag on that hull - which then tells you the amount of power you will have to generate to http://sanderroosendaal.wordpress.c...-2-acceleration-and-deceleration-of-the-boat/

The rowing shell equation in that link is pretty accurate

Basically your biggest drag factor is surface drag which is given by F = alpha v² and alpha is roughly 1.2xsurface area in meters.

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...???

 

[Baltic Bandit]

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

 

[Zain]

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

 

[Zain]

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

I didn't understand the second choice??