For balancing motors youtube/google/rcgroups is your friend.

My piece of advice would be to first build a avispad and learn flying on it with the electronics you have and learn flying on it once you are able to fly it properly then you build/buy the plane which you will use for the solar plane and fly it properly, then you can add the solar panels and test it. Till then you need not sit idle, you can do all the calculations and make your plans theorotically successful ;-)

25 cells in a 5x5 grid need 30"x30"
Diagonal is sqrt((30x30)+(30x30)), or sqrt 1800, or 42.426"
A 44" dia will leave 7" each left/right and fore/aft
Enough for bent up wingtips
Enough for elevator (more than enough)
Motor, ESC and battery go in the power pod / fuselage. Dont need any space on wing.

The whole point of suggesting this configuration is to:
1. Get a flyable model with your existing equipment, and initially without solar cells
2. Learn to fly
3. Find out experimentally the minimum throttle required for level flight
4. Use the same throttle position to check volts/amps/watts with wattmeter
5. Find a real answer to whether it can fly level on 100 watts or less. If not, we need an alternative, probably more high tech, using carbon fibre frames etc. if it flies at 100w or less, then the question is whether the solar cells can provide adequate power
6. If your tests of the solar cells show that 25 of them can give 8amps at say 12.5 volts, you can remove the 2200 lipo (about 180-200gms) and replace it with 25 cells (about 150gms)

I think it's time to move from theory to practical.
Tell me when you are ready.
Then we can discuss the materials required, the expected wing loading etc...
Regards.

Edit:
As well as your motor kv, potential prop sizes etc

Sir, I will start with a DT 700. Could you please tell me an Indian seller which sells this motor? I can't find one.
I will order the motor as soon as possible. But, please beware that around half of the parts that I have listed will be with me only from December. So I will have to wait till the winter holidays.

Sir, is a bent tip required? Or could I put ailerons there?Or shall I have a bent tip with ailerons?Please tell me what foam to use and where to get them.

I will be ready from 5 Nov. I will start building on the 6 Nov. and probably finish the airframe within the day(the whole day is a free day for me)

The all up weight is 700g. With the motor giving 900g of thrust on an APC 11x5.4 prop on 3S, it will be enough.

Warm regards.

I based my recommendations on what you said you have, so that you don't have to buy anything new.

Now i don't know what you have.
If you are yet to buy everything, please consider alternative designs.

Try not to open too many fronts at the same time. There is no end to possibilities. The point is to make a start. And move from theory to experiment.

Once you finalise your plans, contact me for any assistance you need.
Good luck.

Incidentally, it seems to me from theoretical considerations, that it may not be possible to build a functional solar powered aircraft model without recourse to a carbon fibre based structure of fairly large span.

A Nutball (which provides the maximum flat surface area for a given span) seems the cheapest, smallest and easiest way of finding out whether a model is able to fly on the power produced by the cells it is able to carry. Or whether a battery would be essential, and the solarcells would only be able to supplement it to extend the duration.

Meanwhile Karthick's experiments should reveal the output of solar cells under real conditions...

Sir I have already bought the parts it is just that it is waiting in my relatives' home in singapore. They are coming to India on Dec when they will bring it with them
I did this to evade a hiccup from customs.

@ karthick ashwath,
See this.
http://webosolar.com/blog/wp-content/uploads/2013/03/I-V-Curve.png
Max power may be only ~70% of the rating.
Earlier estimates may need significant upward revision!
Practical tests with a few cells essential before proceeding.

OK sir, as mentioned earlier I will put up the test results only on Nov 6. The solar cells are yet to arrive. Anyway, we had planned the model with lots of surplus.

and I found a grave mistake in the specifications. It says that it can produce 4.2~4.3 w at 0.6V. so maximum current produced can only be 7A NOT 8A!

Anyway the motor produces enough thrust on 3S. Lots of extra power. No need to worry.

And sir, when I add the solar cells, I will have both the solar cells and the lipo for safety reasons. And when the solar cells produce more than that is required, it can be used to charge the lipo.

@rcrcnitesh
@ K K Iyer

I would like to make a few things clear. I have already tried all those and gave up. I simply couldn't find a guide to balancing brushless motors that is as good as K K Iyer sir's motor selection guide. Which means that I couldn't understand either. Sorry, but I am just a newbie.

Sir please answer the following questions:
1. Where to get the DT700 motor in India online? I can't find any seller that sells these motors.
2. What type of foam do I use?
3. What configuration of landing gear do I use?
4. What spar configuration should I use?
5. Shall I take a watt, volt and amp reading every 20 minutes for 8hours for the solar cells?

As soon as you answer these questions (sorry, I don't know what to do without the answers for those questions) , I will execute the following plan:


1. Make a test setup for each of the five solar cells
2. Evaluate all the results
3. Post all the results in the form of a graph
4. Build the airframe for a Nutball with 44" diameter
5. Test the motor as soon as it arrives and collect as many details about it as possible
6. Mount all the electronics on the Nutball
7. Acquire 20 solar cells(if nothing breaks)
8. Get a few hours of RC flying under my hood
9. Keep flying till I stop crashing
10. Mount FPV on the nutball

At the same time, I will be doing the following :
1. Mount all the solar cells in series on a piece of foamboard
2. Test the cells as a whole
3. Make it run the DT 700 reliably for quite a long while
4. Test the solar cells running a DT 700 at 80% throttle for 8 hours straight

Final step in making the solar plane:
Mount the panels on the plane and fly it!

Future modifications:
1. Build a blunt nose flying wing whose blunt nose is a square of side 30" using EPO foam
2. Attach the solar cells to it
3. Complete the solar plane project Ver. 2.0!

I will post more info on this Ver. 2 as soon as possible.

Again, I tell you that the test results for solar cells will be available only on 7 Nov.

Warm regards.

hey,
the nutball is a high alpha kind of aircraft which does not fly properly straight. i.e broken stalls ( The tail and nose are in not a straight line while flying!)
So when you are coming toward you, the plane will obviously face you with its nose up. Obviously you'll face away from the sun at all times. so, a moment will come sometime when the solar cells lose sunlight just because the plane is coming towards the sun!
Either you consider attaching a lipo or choose another plane(ft delta would do)

Here is a DT 750 not a 700
http://www.vibranthobbies.com/planes-parts/electric-motors/hextronik-dt750-brushless-outrunner-750kv.html

@prabal276
Thank you, but I don't know of any other aircraft that is as simple as this. Maybe I will make a small one as a trainer and then make that blunt nose flying wing. But I don't know anything for sure, so I will confirm this in a future post.
Thank you very much for finding the motor prabal!

Iyer sir pl. comment on reply #84
Wont the plane lose control for some time even if the plane loses sunlight for a sec.

I figure that what you say is right. But it won't lose control as it has a 2200 mah 3S 20C lipo from Turnigy. I planned on putting a lipo in there for safety.

allright. Then its okay.

Re reply #84,
I said many times that the Nutball is not a great choice aerodynamically.
but it is the smallest airframe that can accomodate 25 cells of 6x6".

If you look at the link in reply 81, you'll see that the max power is well below max voltage times max amps. If you consider that most of the time during flight the sunlight won't be perpendicular, and that the brightness may also vary, perhaps we should not expect more than 50% of the Vmax x Amax!

So the power would probably be quite inadequate for flight on solar power alone.

However, the first objective of this project has to be to simply establish the power available from the cells under practical conditions, and compare it with the actual power requirements. And whether the solar cells will be able to charge the lipo when it is in use.

Meanwhile you could make an estimate of the weight of
the airframe+motor+prop+ESC+rx+lipo+Servos/pushrods+undercarriage and wheels,
assuming 5mm or 8mm depron as the material,
and 2 spars of carbon fibre tubes, say 3mm OD x 30" each.

Sundaram or sandy sir is selling dt700 motors if you are interested , contact him or refer to the second last page of his giant sale thread

To get you started,
My 38x25=950sqin 5mm depron sheet weighs 204gms...

Oh thank you very much sir. Do you still feel that we ought to go ahead with the nutball?
And sir, the weight of the airframe + electronics = 384 + 350 = 744gms ~ 750gms
The AUW when dollartree foam is used is 720gms.

Or shall I start drawing diagrams of my custom built blunt nose flying wing for the solar part of the project? And shall I have my first plane as the flitetest nutball? I have decided to buy a DT750 from Vibrant hobbies as soon as possible.

Do not forget heat shrinks and bullet connectors.
go ahead. Vibrant is a very good shop.

.

I am yet to purchase any heatshrink or bullet connectors. The solar cells have just arrived. Only one cell is broken. I have filed a guarantee claim on ebay. If anyone of you wants to get those cells, then hurry! Only one solar cell set is left! I will post the test details. I had promised a video of the unboxing, but the video is not good at all which is why I dropped the idea.

Could anyone please tell me where to get epo and depron online from Indian sellers?Not a single shop in this city(as far as I know) sells such kinds of foam. This is very important and would be highly useful for me. 

Quote
Which means that I couldn't understand either.

I think I mistyped that one in Reply #83. This sentence is supposed to mean that I couldn't understand the brushless motor balancing video, not the motor selection guide.
As far as I have understood, it is simply trial and error and trying the best to find the light side by using some tape. Then we must take the opposite side of the motor as the light side and subtract a little bit from it by using a Dremel/motor tool.

Am I right?

@v2eagle
I have done a little bit of research and I found that:
1. The Solar Impulse uses Maxeon cells (v2eagle recommended it to me in reply#6)
2. We are planning to use 6x6 solar cells
3. The maxeon is stronger and more durable.
4. though the Maxeon cells are said to have the best efficiency, it has a worse efficiency than these cells

All these are based on the data posted on the internet, not actual data collected by me experimentally.

And please don't even imagine buying those cells on ebay. They are costlier than their actual price. Here is the right place to buy them: RC Hyderabad

Has anyone bought from this store earlier? Has there been any problems?

My claim on ebay has been resolved. I will continue with the aforementioned plan only after testing the solar cells.

Can we please start looking for airframes again? I will buy the DT750 only after completion of testing.

And whoever you are, v2eagle, your selection is very good. sorry, but I checked that plane out just now. But the wing is not flat, which means I can't put my cells there.

I don't know the pros and cons of maxeon cells. The comparison between traditional cells and maxeon cells is in RC Hyderabad.

Note: I am not posting the link because for some reason or the other whenever I put the link and preview it , I get some other website. When I click it, it says that the website does not exist. It displays this: sp4mm3r.com. Why is this happening?

My exams have ended! I will start testing the solar cells soon.