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« on: June 10, 2014, 07:04:39 PM »
topalle
Topalle Srinivas Azad
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Hello Everyone,

Here is a topic that needs to be there on the forum for every member's help and reference...
Experts please put in your two pennies worth and grow this thread..

Regards,
Topalle Srinivas Azad
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« Reply #1 on: June 10, 2014, 07:05:59 PM »
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First up, RC Aeroplanes...

For Scratch-Building scale models of aeroplanes, there are some factors we need to keep in mind...


1)The model is small but the wind blowing doesn't know that whether our model is small or big.
2)The weight to lift ratio of the model may be different  from that of the original aeroplane taking into consideration the different materials and types of construction.
3)The motor-ESC-Prop selection is key to the Scale performance...
4)CG must be very accurate...
5)The aerofoil shape may be complex in the original model which may change the performance of the plane like its stall speed, Lift provided, etc...

This is what I have learnt after reading and searching a lot...
Experts please contribute...
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« Reply #2 on: June 17, 2014, 07:37:26 PM »
topalle
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Nobody wants to contribute?
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« Reply #3 on: June 17, 2014, 10:12:25 PM »
K K Iyer
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You may like to explore cubic wing loading.
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« Reply #4 on: June 17, 2014, 10:22:26 PM »
K K Iyer
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Nobody wants to contribute?

Perhaps because you consider their contribution worth only two pennies...

"Experts please put in your two pennies worth..."

A host may call his house his 'Garib Khana'
But for a guest to call his host's house a 'Garib Khana'...
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« Reply #5 on: June 18, 2014, 05:43:24 PM »
topalle
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Them please consider putting you  Indian Rupees 2 lakh worth knowledge...  Giggle
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« Reply #6 on: June 18, 2014, 07:03:40 PM »
K K Iyer
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You missed my 2 cents worth, contributed in reply number 3.

Looks like you also missed the point. Doesn't matter.
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« Reply #7 on: June 22, 2014, 08:00:40 AM »
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I had been spending these days collecting gyaan about the topic you suggested...
Thanks a lot Iyer sir, for telling me that such a thing existed...
This will improve model-making of not only me but all others who read this...

Cubic Loading...
First the formula... ( I love formulae... I'm a JEE Advanced aspirant Giggle)

Weight of the model
(Wing area)3/2

Why use cubic loading instead of standard wing loading?
Wing loading varies with the size of the model. Cubic loading is constant.
That way, we can compare the performance of the model accurately to that of the original airplane.
Its slow speed performance and stall speed will be scale w.r.t the original airplane

Scale Speed

The scale speed of the model must be approximately th speed of the original subject times the scale factor.
For example:
If the speed of the subject is x km/hour then the speed of a 1:1/50 scale model will be (x/50) km/hour
« Last Edit: June 22, 2014, 08:41:15 AM by topalle » Logged

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« Reply #8 on: June 22, 2014, 08:47:40 AM »
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To achieve this scale speed, we CANNOT simply divide the power of the subject by the scale factor.
We have to take a lot of thing into consideration...
Power systems are DIFFERENT...
Model construction materials and techniques are DIFFERENT...
So, we need to have a different approach...

We need to consider power loading...
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« Reply #9 on: June 22, 2014, 05:11:00 PM »
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Srinivas, you seem to be bent on doling out a monologue Roll Eyes. Let the 'wise men' come out and elaborate . Give people some time, will you?
One more small suggestion : 'putting in my two cents worth' is an idiom; Check how it is used.
Just my two cents. Hope you don't mind.
regards and good luck.                                                                                                                                                                                                                                                                               
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« Reply #10 on: June 25, 2014, 06:41:57 PM »
topalle
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LEGENDS of scratch building please contribute...
Ashta sir, Sanjay Sir, please post your valuable words here...
I guess VC sir and Gajjark sir are not posting because the boats topic hasn't come up yet...
These are the some names that struck my head when it came to scratch building...I may have missed out other great builders...
Please give your words of help here...
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« Reply #11 on: June 26, 2014, 02:06:34 PM »
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I don't think I qualify

However, do remember that in air models, scale is not linear. Dimensions change apparent laws!

Glad to know you are trying for IIT, my Alma Mater. Just remember - the JEE is the easiest part! The fun starts when you are in  Wink >Cheesy
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« Reply #12 on: June 26, 2014, 06:02:34 PM »
topalle
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An example for that is Reynold's number.
SO, we have an IITian here...Bow Bow
Is JEE easy? With the current system, in open category, its harder than ever...
During those days, it must have been a bit easier due to less competition
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« Reply #13 on: June 26, 2014, 06:23:29 PM »
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According to Wikipedia,

 http://en.wikipedia.org/wiki/Reynolds_number

Reynolds numbers are used in airfoil design to (among other things) manage "Scale Effect" when computing/comparing characteristics (a tiny wing, scaled to be huge, will perform differently). Fluid dynamicists define the chord Reynolds number, R, like this: R = Vc / ν where V is the flight speed, c is the chord, and ν is the kinematic viscosity of the fluid in which the airfoil operates, which is 1.460x10−5 m2/s for the atmosphere at sea level. In some special studies a characteristic length other than chord may be used; rare is the "span Reynolds number" which is not to be confused with span-wise stations on a wing where chord is still used.
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« Reply #14 on: June 26, 2014, 06:30:08 PM »
topalle
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Back to power loading...

According to http://www.rc-airplane-world.com/

Power loading needed for rc planes is

Less than 50W/lb - very lightweight / low wing loading slow flyer.
50 to 80 W/lb - powered gliders, basic park flyers and trainers, classic biplanes and vintage ('Old Timer') type planes.
80 to 120 W/lb - general sport flying and basic/intermediate aerobatics. Many scale (eg warbirds) subjects suit this power band.
120 to 180W/lb - more serious aerobatics, pattern flying, 3D and scale EDF jets
180 to 200+W/lb - faster jets and anything that requires Arnie-amounts of muscle!
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« Reply #15 on: June 26, 2014, 06:35:56 PM »
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Hi All,
Can any one guide me on how to make a RC car from start? Note i am new to each and every part but i am very much passionate about cars and bike. I am willing to make my own rc car from scratch to  better understand all the parts needed.
Looking forward for responses.
Thanks,
Shreyas
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« Reply #16 on: June 26, 2014, 06:37:18 PM »
topalle
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Ask Anjan Babu, He has made an awesome 3 wheeled rc car fom scratch...
Start a new thread, experts will help you out...
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« Reply #17 on: June 26, 2014, 10:29:41 PM »
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Thanks but I am not able to post any new thread, I have registered today to this forum
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« Reply #18 on: June 27, 2014, 10:43:34 AM »
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Hi shreyasm, Welcome to the forum. I would suggest going to the following link:
http://www.rcindia.org/beginners-zone/
and then clicking on new topic on the top right corner.
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« Reply #19 on: June 30, 2014, 07:44:49 PM »
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Materials of construction

Old School scale modellers generally use balsa wood for scale modelling
Newer techniques are using depron, coroplast and HD Thermocol
Even newer techniques are vacuum forming, and using a CNC router on a block of foam

I don't know about balsa, so someone who knows please post details...
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