I have come to the conclusion that using the FT Simple Soarer would be better because:

• It has a part of the wing which is totally flat(perfect for solar cells)
• It is a tried and tested model and its tutorial is better

But, as of now, I am undecided over what scaling to use.
It has a wingspan of 44"
Root chord 5.5"
Flat chord(part of the wing which is flat ) 4"

If I use 150% scale, I will get:
66" Wingspan
6" flat chord(perfect for a 6x6" solar cell)
Can place about 10 cells(part of the wing is curved)

Link to the plans:[link]http://www.stonekap.net/ftplans/FT-SS-plans.pdf[/link]

If we place 10 cells, we get 40W.(only at 6V)
So we must use a DC-DC voltage boost circuit and step it up to 8V. So we will have at least 6A.
The DT 700 consumes 4.5A at 2S while running a 11x4.7 prop. So there is enough room for loss due to angle at which it is facing the sun, power for the receiver and clouds.

Are there any mistakes in this calculation?Is the scaling up correct?Would it provide this 40W?Will the airframe be able bear it?

Can anyone help me to scale up the plans? I don't know how to do it. And could somebody please give me the prop test data for a DT700 on 2S? It would be wonderful.

Update: I have decided to use NCR18650B as they weigh only half as much as lipos but have the same mah rating. More info here: [link]https://www.youtube.com/watch?v=adfydRg8PYU[/link]

Can anybody tell me what kind of landing gear I must use?

But be aware . Only and only use genuine panasonic ncr18650b cells and remove their safety ckt  and make sure to leave extra leads for charging terminals . Just take care while working with them

I just burnt my rc tank(cardboard) due to mis handling those are no less dangerous than lipos .
Btw which solar panels you will be using i would recommend the vega robokit panels. . Quality stuff

But sir, vega robokit takes long time to ship. For more info on what solar cells I have used pls check the other pages of this thread sir .Thank you for your advice sir.

Please Dont call me sir i am just 17
and about vega . They are india based

Oh i forgot to see previous pages . Go for the flexible ones their effieciency is nice  and go . And regarding the airframe a flying wing could be a better option .

Your ideas and suggestions are good sir. But I have gone through these topics in my head, but I found that though flexible solar cells are less fragile, their watt to area ratio is not vey good though they claim thei efficiency to be high. And they are mush costlier and large.

The reason for me selecting motor gliders/electric sailplanes is that they are designed to be light, give a lot of thrust and have a large wingspan. As we can glide, we can use the time when the throttle is chopped to charge batteries.

At first I too thought of flying wings, but later switched to motor gliders.

We share the same way of thinking .

Thanks,
Karthick Ashwath.

Quote from: Karthick Ashwath on October 07, 2015, 08:27:12 PM
I want to find an electric motor which provides 700-900g of thrust at 3S and consumes LESS THAN 10A. Don,t mind about the kv or size, it is not important for the calculations. Could you please help me to find such a motor that costs less than or equal to Rs.2000, preferably from Indian sellers?

The DT700/750 was only suggested as an answer to your above query.
May not necessarily be the best solution to your project. So don't get fixated on it.

Let us look at the data we have:
1. 6x6" cells of 0.5-0.6v and 8amps max, or say 4watts
2. For a 2s lipo emulation we need 16 cells, say 64watts
3. 16 cells laid out in a line would need an 8' wingspan
4. Assuming that the flat portion of the chord would be about 2/3rds (since the cells are not flexible), about 9" chord would be needed.
5. That means an 8'x9" wing, or say 6sqft
6. Assuming that you could build a 6sqft wing down to a 6oz/sqft loading, it would weigh 36oz or 2.25lbs, or 1kg.
7. 64 watts would give a power loading of under 30watts/lb, or just about enough for level flight without any reserve for climbing.
8. The all up target weight of 36oz (for a 6oz/sqft loading) includes the payload.
9. The payload would be say 100gms for the cells, 80gms for a DT, 50gms for servos and esc, 80gms for a 2s 1000mah lipo. Say 300gms or 10oz.
10. That leaves some 26oz for a model of 6sqft wing area, or 4-5oz/sqft.
11. Not easy for a model of this size, but possible with some CF tubes and depron or balsa.

So while waiting for the cells, you could experiment with some depron to see how much a model of 8' span and 9"chord will weigh. Assume horizonal tail are of 25% to start with.
Then we can consider whether an Emax CF2822 turning a large prop on 2s is better...
(Thought you are not available till 2nd week of Nov...)
Regards.

Sir, that seems very reasonable. But sir please take a look at this(I may be wrong,please bear with me )
Wingspan of FT simple soarer = 54"
Wingspan of 150% simple soarer = 81"

Flat chord = 5"
150% flat chord = 7.5"

Area available for solar cells = 81*7.5 = 607.5sq. inch  (let us take as 600 sq.inch)
No. of solar cells that can be fit = 600/36 = 16.6666666666 = 16

Exactly the no. of cells we need for a 2S! Yay!

Total weight of the airframe = 150% of 320 = 480gms

Weight of the solar cells = 6x16 = 96gms = 100gms

Weight of all the other electronics(thanks for calculating the weight of the electronics) =  250gms

Total weight of the aeroplane comes at about 850gms sir. Would 50% thrust be required or should we choose 35% thrust(according to your guide to motor selection sir )

Yes sir, I do agree that the DT700/750 is the best motor which fits all the categories. sorry for getting fixated about that.

And sir, thank you for putting up such a good summary of all the data we have!

Thank you for simplifying everything sir. Was eagerly waiting for your reply sir!

Sir, what do you think of using genuine Panasonic NCR18650B batteries instead of traditional lipos?

Sir, what type of spar configuration do you think we need sir?

You surely can use the panasonic cells but you there is a catch. According to what I know about ncr cells have a c rating of about 2/3 which when multiplied by the current which is 3.4 is something between 6.8 and 10.2, donxt you think you'd be pushing it to it's limits which may be harmful for the cells. I am not sure though.

@karthick ashwath,
No idea about the Panasonic battery.

When you double a linear dimension, the area increases by a factor of 4, and volume by a factor of 8.
So does the weight.
A 1.5 size airframe will weigh 1.5x1.5x1.5 times, or 3.375 times the original.
If the original is 320gms (without payload), the 1.5 times one will be 1080gms! (Without payload)
Please check if 320gms is all up weight, or only bare airframe.

I presume the solar cells cannot be cut to 1.5"x6".
So a 7.5" width can take only one cell.
And 81" span can take only 13 cells!

Yes sir I totally forgot about the doubling.
No sir, it is the weight of the bare airframe without any electronics. Accurate weight of airframe is 311 gms.

Yes sir i totally forgot about that factor. So we can get a maximum of only 52 W. Must start looking for a new airframe.

Maybe should we go back to square one and start a search for a different airframe(maybe we even have to start looking for a new motor)

Hope that someone,you,or me is able to find a good foam electric motorglider which fits all our requirements (at least most of it) 

We now have two choices:
Either to use an existing design or
Design one ourselves! This may or may not be possible, taking in account my experience with rc.

Hope that we could come to a conclusive decision.I would really appreciate any help.

@karthick ashwath,
Remember my saying that
1. Getting solar cells to power a motor adequately is one project
2. Building an airplane model that can fly reliably, is an altogether different project
3. Combining the two above is the third project...?

I'll add one more.
4. Learning to fly an RC model is an entirely different project in itself.

Do NOT combine these 4 in a single attempt!

I had also suggested that you look at the flitetest Nutball.
Please do so now.
It is not so great aerodynamically, but it can take 25 cells in less than 4' wingspan!

Questions:
1. What do you calculate as the minimum span required to accomodate 25cells? Or 16 cells?
2. What equipment do you already have?
3. Have you made a list of items you need and their cost? Please share the list.
4. Have you considered the cost of replacing items that can get damaged (eg, props, motor) or because they were the wrong choice (eg, motor, props, esc, batteries, charger)? Will your budget cover these?

Several times I've lent, on a returnable basis, stuff required by newbies, to help them avoid wasted expenditure. But i guess you can manage on your own  .

Please do answer the above questions specifically, so that i can share the next steps i have in mind.

But if you have exams, turn off internet, and do not post on RCI till they are over.
Sms me when free.

1.Sir I go with 16 cells and I take the maximum wingspan for conventional airframes as 17*6 = 102", this is when the width of the aeroplane can only support one cell.

2. I already have:
1 366W motor
1 60A ESC
1 Orange Rx receiver
1 Orange transmitter
1 Skyzone 5.8ghz Tx Rx set
1 Camera
5 sets of XT60s
1 Orange transmitter
4 landing wheels
1 set of Circular polarized antennas for 5.8ghz
2 turnigy 2200mah 3s lipos
1 Turnigy Accucell 6 smart balance charger
1 10A SMPS (to power the charger)
2 APC style 7x5 prop
3 HXT 900 servos
1 multimeter
1 Soldering iron

3. No sir, I have not made up a list of the things I will need. Will make one soon.

4. No sir, I have not considered buying any extra props(I will buy 2) as I have a prop protection fan casing which I use to protect my props. As for the motor, I do not know what to do sir.
And yes sir, my budget will cover the cost

And sir, could you please say what you mean by

QuoteSeveral times I've lent, on a returnable basis, stuff required by newbies, to help them avoid wasted expenditure. But i guess you can manage on your own

Sir, what do you think of using this glider:www.charlesriverrc.org/articles/aegea2m/markdrela_aegea2m.htm

I could build this glider by using depron instead of balsa except for the fuselage where I will use Dollartree foamboard. I could use Carbon fibre spars.

@karthick ashwath,

Good. You have nearly everything required. You'll need a hot glue gun, and props, pushrods, control horns, wire for undercarriage etc.

Well, you can build the Aegea if you like, though not a suitable choice in my opinion.

My recommendation is that you built a Nutball scaled up to say 44-45" dia. The reasons are:
1. Simplest configuration to accomodate 5x5 or 4x4 cells
2. Easiest construction. Can be built in a few hours.
3. Cheap
4. Easy to repair/replace
5. You can use your existing motor, esc, lipo
6. With this model you can teach yourself to fly, even if you don't have access to an instructor.
7. Fly it without the solar cells first. This will ensure you have a safe platform before you risk the cells.

Go ahead. Best of luck.

Sir but the op has a 366w motor with 60a esc. I don't think that would work.

Thank you sir. I will definitely get a new hotglue gun and, the benefits of the nutball seem almost endless. I will learn by using this plane. Safe to fly without an instructor? amazing!

You can expect this plane to be built by 7 Nov. By that time I will also have my solar cell test results ready.But sir, I came to know that it becomes very difficult to build large nutballs due to its requirement for light wing loading. I don't know what to select sir.

Sir what type of foam do you recommend for the nutball?

Thanks,
Karthick Ashwath.

Also there is one more thing to consider, the lift produced by the wings. I don't think it can fly with 64 watts on a 8v and 8A setup weighing around 700-900 grams. I don't think that's enough power for a giant nutball which has very less lift. It can't even increase it's altitude. You need a glider.
Experts correct me please

@rcrcnitesh,
@karthick ashwath,

Karthick has been looking at various alternatives.

Please suggest a suitable model that:
1. Has enough flat surface to fit 25 solar cells of 6"x6" each
2. Can fly on 100 watts
3. Can be built and flown by a newbie building his first model and with no prior flying experience
4. Will not cause too much heartbreak if it crashes!

Let me condense my reasons for recommending a scaled up Nutball:

It is the simplest and cheapest way to find out experimentally, the minimum power required to fly the smallest model capable of carrying 25 cells, especially for a newcomer. As opposed to an expensive, large, lightweight, multimotor model that could be built by an expert using carbon fibre

Why don't I try both the options and which one suits me the best? Sir, why don't we make a smaller Nutball, with lesser wing area, lesser weight and which requires lesser power? That would make things a lot easier. Nutballs get difficult only when you go crazy on the size. So let me try different diameters, experiment with them in my thoughts and by calculations, and find out what type of scale is best. I will keep my eyes wide open for even simpler airframes which are large enough.

Sir, I have a few calculations, according to which I need to build a Nutball with 60" diameter (approx) to fit 20 cells. I will love any tips and advice on the following:

1.How to build a large nutball with minimum weight with a Kfm-4 aerofoil and spar configuration(for 60" wingspan)
Any existing builds (if any) with a similar configuration can also be put up.
2. How to balance a brushless motor

Though I have looked at various pieces of information on how to balance a brushless motor, none of them are detailed. Any links/advice is very good.

I will post my calculations as soon as possible.

I have given up on finding any gliders with a flat surface as such a glider simply doesn't exist. Anyway, building gliders is not for the beginner.

Here are my calculations:
Required flat area not affected by control surface = 20x36 = 720 sq. inch.
Usable flat area = 8x12 = 96 sq. inch

Therefore, scaling up required = 720/96 = 7.5
If scaling up for area is 7.5, then scaling up for side is sq. root of 7.5 = 2.8(actually 2.73)

Scaled up length = 3(instead of 2.8)x12 = 36"
Scaled up width = 3x8 = 24"
Scaled up diameter = 3x19.3 = 57.9~58"

It is possible to fit 4 solar cells side by side along the breadth
It is possible to fit 6 solar cells length wise.(I will fit 5x4 )

Extra space is for battery,esc, etc.

I have referred to the plans by Flitetest which I have scaled up.

Please check and verify my calculations.