@rcneil21
No sir, it is my second rc airplane build.(ironic)Thank you very much for your wishes!
Thanks in advance,
Karthick Ashwath.

 I have found that even a Kfm-2 based flying wing with 96" wing span is not enough. So we must look at huge planes or find a different motor that consumes mush lesser current. Hope that you could help me.
Thanks in advance,
Karthick Ashwath.

Karthick

I think you should have a look at the current multirotor motors with kv in the range of 300-400. They would use big props (15-17 inches) and consume low amps. But these motors cost some bucks and won't be in 1300-1500 Rs range.

If you can spend some bucks have a look at motors like T-Motors Anti Gravity 4006 380 kV. If you believe the manufacturers data, it produces 380 Watts of power and weighs mere 66 grams. These are the lightest motors I have come across till now. However they cost 150 USD for a pair.

Oh no, sir , but that is way out of my range. Sorry. I will see if I can somehow obtain those motors.
Thanks in advance,
Karthick Ashwath.

@karthick ashwath,
RIGHT!
Exactly what i've been considering.
Tell me, do you have the cells with you or yet to get?
Do you have ANY motor for testing? (Don't buy a motor yet. Wait. You can use a 12v car headlight bulb of 50/55w as load)
Do you have a wattmeter that can display amps and volts simultaneously?
I agree that the first test has to be with some or all cells mounted on a flat plate, to check output at different angles of sunlight.
And for the present, put 10+hours etc on the backburner.
Just now we need to establish how much power we can get for say half an hour around noon.
(Flying wing or conventional etc we'll discuss a bit later.
And what is the weight of each cell? 6gms?)
BTW, I'm free till 9. So we can exchange msgs back and forth.

Sir, though I do possess a motor for testing, it consumes 3000W, which is way too mush. I can build the constant current load setup which will pull 10A at all times, or as you said, I can simply use some car headlights. Yes sir, the weight of the cell is 6gms. I will ask my acquaintances if they have a watt meter which they can lend. I will somehow acquire one, or I will simply resort to multiplying amps and volts. But no sir, I have not bought the solar cells yet. This is just research. I will acquire them as soon as possible.

Thank you very much for your excitement,
Karthick Ashwath.

@k k iyer
Sir thank you very much for your excitement and interest. Thank you sir!

3000w?
4hp?
Probably not meant for model airplanes

Sir I made a terrible mistake. Sorry. It has 366W at 3s and has 3000kv. Sorry sir.
Thanks,
Karthick Ashwath.

Regarding 24-25 cells.
I think with solar cells, when sunlight reduces, it is the current capacity that reduces, and the voltage remains the same. Pl check if this is correct.
So instead of 0.6x25=15v, 0.5+ x24=12v-13v should be ok.
I've not yet checked the internal resistance of solar cells, so i don't know how much the voltage will drop under load. With lipos it often goes below 11v at full throttle...

But sir, I am not sure of what happens at such times. I will try enquiring about it.

@karthick ashwath,
This project needs to be broken into 4 parts:
1. Capability of power source (solar)
2. Power required
3. Aerodynamic issues / payload capacity
4. Structural issues.

The last three are interconnected.

Let's tackle no 1 first.
The one thing we know is the per cell voltage (0.5-0.6v)
To emulate a 3s lipo, we need 24 cells.
To emulate a 2s lipo, we need 16 cells.

The questions before us therefore are:
1. How much current can they produce?
2. How much do they cost?
3. Should we get 16 or 24 or 25?
4. When will they be at hand?

You can answer 2 & 4.

Meanwhile i'll try to evaluate the amps and thrust with larger props at 2s voltage with some of my motors (DT700 or 750, not sure, DT850, CF2822 1200kv, 2836 1000kv etc)
May take me some time as my 2s lipos have jst connectors, and ESCs have XT60s. And i don't have jst's to make up jst to xt converters.

If you would like to tackle some more issues, i'll put them in my next post 

Sir, that reply is very good. Anyway, I will try my best to answer all the questions.
Question No. 1
Ans 8A at maximum(reptitive, sorry)

Question No. 2
Ans. They cost almost Rs.4500 for 30 cells but this is on ebay.com and since this includes shipping this is costly. I will speak with a dealer whom I know and ask about this to him.

Question No. 3
Ans. If we are using 2S at around 80W so we will need 20 cells(I have taken 80W instead of 78 and have also taken per cell wattage as 4W)

Question No. 4
Ans. Probably by the end of this month(maybe) but this will become true only if our research becomes conclusive and we settle on a single setup. My parents will allow it only if we have conclusive evidence(my mom has a physics background, she will check all my calculations)

Thanks in advance,
Karthick Ashwath.

Quote from: Karthick Ashwath on October 15, 2015, 08:44:51 PM

Question No. 1
Ans 8A at maximum
That's what it says. What we want to know is how much for about half an hour around noon, ie, in real life

Question No. 2
Ans. They cost almost Rs.4500 for 30 cells.
For about Rs 1500 you get a 3s 2200mah, which can safely give 8-9amps or 100w for 10minutes. So if 24 cells for Rs 3600 can output 100w for 25-30 minutes... But this is not about economics i hope...

Question No. 3
Ans. If we are using 2S at around 80W so we will need 20 cells(I have taken 80W instead of 78 and have also taken per cell wattage as 4W)
No. Go by the voltage, not wattage. 16 to emulate a 2s

Question No. 4
Thought experiments are good and necessary. But they have to be followed by real trials. You can't proceed ahead without at least 16 cells and a meter! Good that your mother has a physics background, so she can examine my suggestions, and PM me for clarifications...

Thanks in advance, No more thanks in advance, as this is an ongoing conversation!

Ok sir, I am thinking of getting a single cell and examining its characteristics to find the amps , watts and the volts at different times of the day(i am going to place it there at different times, not leave it there as it will increase the temperature of the cell which will definitely reduce the no. of amps produced). This will prove to be priceless for future calculations.

Let it heat!
Not going to use an umbrella on the plane!

No sir, not that we are going to use an umbrella for my plane, its that while flying, the wind will cool the cells.

Sir, I just saw a Five piece solar cell pack being relisted in ebay.in. Shall I buy it for testing? According to it, it cost Rs.170 per cell.Not bad. I just came across it. Here is the link<link>http://www.ebay.in/itm/Educational-Solar-Cell-High-Efficiency-4-33W-5-pieces-/111798896253?</link>. Sir it is a very hot item so it may go out of stock in a couple of days. please inform me about the thrust test, if you have completed it. Could you tell me what soldering iron you use?I also want to know what setup you use for long range FPV.

I have a multistar 4010-375kv motor invade you need it.

JK

@karthick ashwath,
You may be confusing yourself by tackling too many different issues at the same time.
1. To check out solar cells, you have to get some. Whether it is worth it it is something only you and your budget can decide.
2. What soldering iron i'm using has no connection with this project.
3. FPV? What's that?

Have you even flown an RC plane yet?
Let your imagination fly, but don't let it ignore reality.
Get your feet firmly on the ground.

To make a solar airplane you need to know two things
1. How much power is available?
2. Is it enough to fly my plane?

If it was simple, others would have done it already, no?

Um sir, to be frank I have not but I have flown one in my simulator with a real Mode 1 remote. Yes sir, what soldering iron you use has no connection to the project , it is because I am thinking of buying one but don't know which one to get. Sir, FPV stands for First Person View(by placing a camera on the plane, transmitting the video and receiving it on the ground, mostly using 5.8 ghz due to its free use in India)

And your philosophy is good, which is what I often keep reminding myself about. Sir it is not simple, but it looks like a bit of the starting of the forum when you say:

QuoteTo make a solar airplane you need to know two things
1. How much power is available?
2. Is it enough to fly my plane?

Sir please confirm whether it would be correct to get those cells.

Sir I feel that it would make things a bit (just a bit, not a lot ) if we use an existing glider airframe as they are large and they are designed in such a way that they fly for a long time as it would be perfect for our project. Gliders can be used because we do not require a lot of speed(just 2.5-3 times the stall speed  )

Sir could you please tell me a time when we can come online together so that we can discuss things a lot more efficiently? We could decide on some time form 6.00 to 8.00 pm(when I am allowed to do my research)

@karthick ashwath,
You answered my FPV question, without even realising that it was a rhetorical question!
Obviously you thought i dont know what FPV is...

You appear to have gained enough knowledge to not require any further assistance.

So goodbye and goodluck.

Sorry sir that was not what I intended. No sir, I cannot accept that I have gained enough knowledge on this topic. Maybe I had been rude, too overconfident, my bad, please don't take any offense. Sorry again. I am just a newbie. 


Sorry again. Hope that this doesn't happen in the future. My bad,I accept.

Sir, I like this particular plane for our project. It is a Allegro Lite 2m balsa glider. Many people recommend this glider. Here is the link to its plans:http://www.charlesriverrc.org/articles/allegrolite2m/Allegro_E_Lite.pdf

A DT700 running on 2s would be more than enough for this plane.ccording to the winf=g area of the plane, we can fit 13 cells (actually 14, but some area is curved, so 13) which will give us 7.8V at optimal conditions.

I have purchased the solar cells. It will arrive on October 28. But my exam ends only on Nov 5. So you could expect the test results by 7 Nov.(exam is yet to start)

But I have 0 experience with balsa so a foam glider with about 2M wingspan would be good.(I am unable to find one.)

Though I cannot find a good foam glider with 2M wingspan, I would like to know whether this glider would be enough>It is the photon, has 60" wingspan 5" root chord. I do not know the other details, which is why I am unable to calculate the wing area.

Link to video(by Experimental airlines):

Link to a preliminary pdf plan: https://docs.google.com/file/d/0ByhtTaHuhLwvb3luRDJhMjdkTEU/edit

Or would using the FT Simple Soarer be a better idea? Link: http://flitetest.com/articles/ft-simple-soarer-build