RC India
Welcome Guest, please login or register.
 
Pages: 1 [2]  All   Go Down
0 Members and 1 Guest are viewing this topic. Topic Tools Topic Tools 
Read
« Reply #25 on: September 20, 2017, 10:24:31 PM »
K K Iyer
Global Moderator
Forum Hero
*****

Reputation Power: 61 
K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!
Offline Offline

City: Indore
State: Madhya Pradesh
RC Skills: Intermediate
Posts: 5165
Join Date: Jan, 2012



@swapnilnimbalkar,
Thats not the end of the story though.
When you are in a left bank, the plane slips to the left.
When you are in a left yaw, the plane slips to the right.
Both result in extra drag as the plane is flying a bit sideways.
Balancing these two is called a 'coordinated turn'

Stopping here as we are quite far from the heading of this thread...
Logged
 

Read
« Reply #26 on: September 21, 2017, 05:54:16 AM »
sanjayrai55
Plane Lover
Forum Hero

*****

Reputation Power: 85 
sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.sanjayrai55 is a force to reckon with.
Offline Offline

City: Gurgaon
State: Haryana
RC Skills: Intermediate
Posts: 8337
Join Date: Dec, 2011

Don't wake a Tiger until you've factored the teeth



 Salute Iyer sir. Unretired fully now, I trust
Logged

 

Read
« Reply #27 on: September 21, 2017, 07:11:58 PM »
swapnilnimbalkar
Plane Lover
Forum Veteran
****

Reputation Power: 4 
swapnilnimbalkar has no influence.
Offline Offline

City: Thane
State: Maharashtra
RC Skills: Beginner
Posts: 307
Join Date: Nov, 2016



@swapnilnimbalkar,
Thats not the end of the story though.
When you are in a left bank, the plane slips to the left.
When you are in a left yaw, the plane slips to the right.
Both result in extra drag as the plane is flying a bit sideways.
Balancing these two is called a 'coordinated turn'

Stopping here as we are quite far from the heading of this thread...

Understood. Thank you Sir.

Now consider this imaginary situation.

I am in a level flight, now I move stick to the left for a left turn,
Left aileron has moved up and the right one down,

Now here's the twist,  suddenly the left aileron servo stops working and puts the aileron at its place i.e. at "0" position.
But the right aileron is down.

What will happen next?
Logged
 

Read
« Reply #28 on: September 21, 2017, 09:56:43 PM »
K K Iyer
Global Moderator
Forum Hero
*****

Reputation Power: 61 
K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!
Offline Offline

City: Indore
State: Madhya Pradesh
RC Skills: Intermediate
Posts: 5165
Join Date: Jan, 2012



@swapnilnimbalkar,
Let me share a true story.
I was flying my Dynam Tiger Moth slowly.
So slow that it was just about moving forward.
Its possible to fly her like that due to her low wing loading.
I gave left aileron, and she started turning right!
I really thought that the controls had somehow got reversed, but they had not.
So what's the explanation?

You need to look at a typical lift and drag curve graph to find out.
The clue lies in the fact that the airspeed was low, hence the ...... Huh???
I think you'll feel really happy on discovering the answer!
All the best.

image.jpg
Re: Props - Diameter and Pitch
* image.jpg (31.85 KB, 800x600 - viewed 815 times.)
Logged
 

Read
« Reply #29 on: September 22, 2017, 05:02:28 PM »
swapnilnimbalkar
Plane Lover
Forum Veteran
****

Reputation Power: 4 
swapnilnimbalkar has no influence.
Offline Offline

City: Thane
State: Maharashtra
RC Skills: Beginner
Posts: 307
Join Date: Nov, 2016



So this is what I feel,

consider a metal rod with two wheels on either end attached to it.

lets say the whole assembly is moving forward;

suddenly you apply brake on right wheel, still the left wheel is free to move, so what will happen?

left wheel will keep on moving and the whole assembly will take right turn.

In the Dynam Tiger example the right aileron which had moved down acted as a brake and left aileron was neutral so your plane turned (actually yawed) right, instead of rolling.

This is what I can think of. 

Expecting your views.
Logged
 

Read
« Reply #30 on: September 22, 2017, 06:27:33 PM »
K K Iyer
Global Moderator
Forum Hero
*****

Reputation Power: 61 
K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!
Offline Offline

City: Indore
State: Madhya Pradesh
RC Skills: Intermediate
Posts: 5165
Join Date: Jan, 2012



Left aileron was NOT neutral.

The problem needs to be viewed in aerodynamic terms, not mechanical engineering terms!


You need to look at a typical lift and drag curve graph to find out.

The clue lies in the fact that the airspeed was low, hence the ...... Huh???
I think you'll feel really happy on discovering the answer!
All the best.
Logged
 

Read
« Reply #31 on: September 24, 2017, 08:14:19 PM »
swapnilnimbalkar
Plane Lover
Forum Veteran
****

Reputation Power: 4 
swapnilnimbalkar has no influence.
Offline Offline

City: Thane
State: Maharashtra
RC Skills: Beginner
Posts: 307
Join Date: Nov, 2016



I thought a lot about it.

It seems that,

when the plane was turned to left the (i.e. right aileron was down) it increased the Lift on right wing

but increased lift came with a penalty of increased drag.  Since the plane was just above stall speed it could not overcome the drag produced by the right wing.

Hence it turned to the right.

Correct  Head Scratching
Logged
 

Read
« Reply #32 on: September 24, 2017, 10:33:48 PM »
K K Iyer
Global Moderator
Forum Hero
*****

Reputation Power: 61 
K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!
Offline Offline

City: Indore
State: Madhya Pradesh
RC Skills: Intermediate
Posts: 5165
Join Date: Jan, 2012



I thought a lot about it.
It seems that when the plane was turned to left the (i.e. right aileron was down) it increased the Lift on right wing but increased lift came with a penalty of increased drag.  Since the plane was just above stall speed it could not overcome the drag produced by the right wing. Hence it turned to the right.
Correct  Head Scratching

@swapnilnimbalkar
Was wondering why no response for over 48 hours. Obviously you were thinking about the problem!

In scientific enquiry, one has to be careful in statements. You said:
"Since the plane was just above stall speed it could not overcome the drag produced by the right wing."
Remember that the lift and drag directions are at right angles.
So the lift cannot play any role of 'overcoming' drag.

Did you look at any lift curve and drag curve graphs?

The Tiger Moth, when at low airspeed, had to be flying at high angle of attack

In the lift drag curves, you will see that at high angles of attack near stall, an increase in the angle of attack produces negligible increase in lift, but a significant increase in drag. (right aileron down)
Similarly at high angles of attack near stall, a decrease in the angle of attack produces negligible decrease in lift, but a significant decrease in drag. (left aileron up)

Is this true when flying at higher airspeed, ie, at lower angle of attack?

I'll be very happy if you find the answer by looking at a graph of lift and drag vs angle of attack.
Enjoy your research!

Logged
 

Read
« Reply #33 on: September 25, 2017, 11:45:59 AM »
swapnilnimbalkar
Plane Lover
Forum Veteran
****

Reputation Power: 4 
swapnilnimbalkar has no influence.
Offline Offline

City: Thane
State: Maharashtra
RC Skills: Beginner
Posts: 307
Join Date: Nov, 2016



Iyer Sir,

Did you look at any lift curve and drag curve graphs?
> Yes I did (but didn't understand),

But your statement,

"In the lift drag curves, you will see that at high angles of attack near stall, an increase in the angle of attack produces negligible increase in lift, but a significant increase in drag. (right aileron down)
Similarly at high angles of attack near stall, a decrease in the angle of attack produces negligible decrease in lift, but a significant decrease in drag. (left aileron up)"


made it clear.

What I assumed is that, lets say your wing is at an angle of attack of 10°, I thought it means whole wing is at that angle of attack.  But when you deflect the ailerons your angle of attack is different on both the sides of the wing (correct?), I didn't know that.

"Is this true when flying at higher airspeed, ie, at lower angle of attack?"

>No, it's not true. At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!
Also at higher speeds L/D is most favorable.

It seems to be an interesting topic to explore.  I will try to find out more information on this.

Thank you!

Swapnil N.
Logged
 

Read
« Reply #34 on: September 27, 2017, 01:17:33 AM »
K K Iyer
Global Moderator
Forum Hero
*****

Reputation Power: 61 
K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!K K Iyer is a rising star!
Offline Offline

City: Indore
State: Madhya Pradesh
RC Skills: Intermediate
Posts: 5165
Join Date: Jan, 2012



At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!
Also at higher speeds L/D is most favorable

As I said earlier, have to be careful in your statements!
"At higher airspeed the angle of attack is decreased and CL will decrease but CD will decrease too!"
That was not the point.
What I wanted you to see was that the effect on the lift and drag, of a change in the AOA, at low AOA was different from that at high AOA.

"Also at higher speeds L/D is most favorable"
L/D is highest at a specific speed, not just 'higher speeds'
Logged
 

Pages: 1 [2]  All   Go Up
Jump to:  

Related Topics
Subject Started by Replies Views Last post
Wanted brushless motor (2350kv-2500kv) 28mm diameter.
Wanted
krishnatr 3 1875 Last post April 25, 2014, 05:24:13 AM
by krishnatr
Wanted brushless motor in the range 2350kv-2700kv. 28mm diameter.
Wanted
krishnatr 1 1653 Last post June 27, 2014, 01:29:55 PM
by IndianHobbyShop
Plastic Propellers - 5.5" diameter
For Sale
ankush812 0 1133 Last post September 15, 2015, 12:11:26 PM
by ankush812
Looking for a 3.25 inch diameter Spinner
Wanted
shobhit17 8 2591 Last post February 18, 2016, 08:05:01 PM
by shobhit17
12mm diameter smooth rods 1meter length
Wanted
cyberhack 0 898 Last post April 20, 2016, 11:09:59 PM
by cyberhack