New Build - Piper Cherokee 40 Sport Scale for 2015 Sweepstakes

Started by sanjayrai55, July 28, 2015, 07:57:24 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

jana.f22

This looks like a balsa ARF model. Kudos sanjai sir for the finish .  :salute:
3D addict

rcrcnitesh

Arre waah waah waah, arre waah waah waah arre waah waah waah.
Awesome build.
Maker | Aeromodeller | Teenager

sanjayrai55


rohitsharma


sanjayrai55


Ghanesh Raajasekar


sanjayrai55


sundaram

This model definitely needs to flaunt a Piss on Balsa sticker.  Fantabulous Model.

sanjayrai55


sanjayrai55

Let's hope the weather is good this Sunday. Maiden planned

sundaram


sanjayrai55

Finally maidened it  ;D ;D

High winds. So I asked my good friend Group Captain Ramesh Tahlan (retired) to maiden it  ;)

I had taken my camera, but realised I had left the memory card in the laptop since the last time I used it. So - Girish's camera


sanjayrai55

So we have some very good video of landing and take-off, and some very good audio in between  :rofl:

The model flies very well. Despite a strong cross wind, it was very steady and stable in the air. Although it cruises at 40% throttle in a very scale like flight, it is capable of most sport aerobatics

Would highly recommend it for someone who wants to make a 46 size Sport Model

ashok baijal


sanjayrai55

Thanks Ashok-ji. Finally had some clear weather - very windy though

sanjayrai55


rastsaurabh

Sir, it nice to see coro getting into Nitro... hope this will attract many more to try their hands on coro.

from far its hard to tell its balsa or coro.

regds
SR

sanjayrai55

Thanks Saurabh

Actually Spads started purely in Nitro. The original site was spadtothebone.net and still is. The mirror site with forums is spadworld.net. One of the reasons was Spads were perceived to be heavy, and Electrics in those days meant brushed, geared motors and NiCd or NiMh batteries!

The only popular electric spad I have known is Bex's Avispad. In fact when I started out in Electric Spads I, and many others built this - I built 3  ;D

Later on I started adapting balsa-nitro designs I found to electric, with some success. As I progressed, I discovered with proper build techniques, Corro could be built lighter than balsa!

sanjayrai55

I got a PM, which I choose to answer here, just in case any others have similar doubts

"hello sir,
this pm is regarding the piper cherokee of yours.
will a 3536 1100kv suffice?"

Anyone who has followed my Corro builds will realise I have done a large number of Balsa/Nitro conversions to Corro/Electric. Although I do not claim to be, nor am, any sort of authority, a few fundamentals based on schoolboy physics tell me:

A prime mover, whether an electric motor or engine has a few basic output characteristics _

Power - measured in Watts or HP normally
Torque - unit is eg N-m, dyn-cm, foot-pound etc
RPM - inv. sec
Power = Torque X RPM; ie the rate of doing work

For an electric motor: Power = V X A
For an IC Engine, Power = PLAN X K
P= Brake Mean Effective Pressure, a combination of Compression Ratio, Fuel Thermal & Combustion Characteristics etc.
L A = Length X Area or swept volume in cylinder
N = RPM
K is a constant depending on Units of measurement eg MKS, CGS, FPS systems

For a model to fly successfully, the prime mover (or Power Source) should be able to swing a propeller of desired diameter and pitch at a desired RPM. Which would need appropriate Power, and Torque.

In the case in question, the Cherokee as stated earlier has a weight of 2.8 Kg, or ~ 6.2 lbs. It is a low wing sports model, and would need 100-125 W/lb to fly, going by a rule of thumb. It would therefore need about 620 - 775 Watts power.

The motor in question (Avionic) has the following performance data as per RCB website

PROP – 10x7E
● Get 1600gms Thrust
Lipo – 3cell 11.1V
Operating Voltage – 10.8V
Amp draw at load – 32.7 amp
ESC - 30 amp
Power – 327W


PROP – 11x5.5E
● Get 1900gms Thrust
Lipo – 3cell 11.1V
Operating Voltage – 10.8V
Amp draw at load – 32 amp
ESC - 30 amp
Power – 300W


PROP – 9x4.7E
● Get 2000gms Thrust
Lipo – 4cell 14.8V
Operating Voltage – 13.8V
Amp draw at load – 42.5 amp
ESC - 40 amp
Power – 595W


PROP – 10x7E
● Get 2300gms Thrust
Lipo – 4cell 14.8V
Operating Voltage – 13.6V
Amp draw at load – 48.5 amp
ESC - 40 amp
Power – 630W


PROP – 11x5.5E
● Get 2700gms Thrust
Lipo – 4cell 14.8V
Operating Voltage – 13.6V
Amp draw at load – 47.2 amp
ESC - 40 amp
Power – 613.6W

So it is clearly not enough Powr.

Another point which I would advise caution on in selecting a motor - do not go by the maximum output of the motor. If you have to fly at full throttle continuously it is not a very smart selection at all! Better have a motor of at least 25% higher rating.

prabal276

hello,
thank you for answering my queries.
but cant the model be built lighter? (i.e when you remove the engine, its accessories and extra supports for the engine)
the weight would significantly go down.
or another method,
scaling the plans down a little.
I obviously may be wrong in what i am suggesting above! ;D

sanjayrai55

In my experience, once you cross a certain threshold, eg a 25 size engine, the motor/engine equation shifts in favour of the engine. ie, the Battery/ESC/Motor combination will start to weigh more for a decent flight time (7 minutes or more)

There is not much weight reduction for fuse strengthening: you still have to design for the power and torque

On scaling the plans - I don't venture much into the Airframe design, so I cannot comment. Suffice to say that IMHO it really needs very advanced knowledge to be done properly. If someone wants to do a Mickey Mouse job, that is their affair

shauviks

+91-8093863974
#Bring it on flyer

prabal276

Sorry sir if i have hurt your feeling or have said anything wrong.....
From the message of shavik sir above,
i feel that i have done something wrong.

I deeply apologize....

sanjayrai55

Not at all Prabal!

Don't worry about Shauvik - nowadays he comes on the forum once a year and creates some hungama then vanishes  :rofl:

shauviks

@prabal  dude   hah ha ha  .. no need to apologise .... i was joking


@sanjaysir - u still owe me a plane ................   hungama apna style hai sirjeeee
+91-8093863974
#Bring it on flyer