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« on: August 07, 2010, 05:06:25 PM »
JKKASTA
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Hi everybody

if motor supply 500 gr thrust can it fly 800 gr plane?
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« Reply #1 on: August 07, 2010, 11:15:08 PM »
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hi,

I am no expert and not even started flying but the web says the following

Thrust vs weight

1 : 1 - Is the best for any normal plane , more thrust will ensure a vertical climb capability.
0.5:1 - is the minimum for any plane to fly.

Anything in between should be good for a trainer, but it will increase the take off and reduce manuverability in the air when it is low.

i am currently working on a Coro Stick and it has a weight of 700g. My motor is capable of 600 gms thrust. So i presume that is sufficient for my plane
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« Reply #2 on: August 07, 2010, 11:58:12 PM »
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well i can say thrust is not at all related to weight ,it only desides how much speed required to overcome a drag created by air to make a incoming air a bit faster than stall speed!
in some instance even thrust is also made according to wing area, where lift purely depends upon thrust and drag an example Mig-21,it needs a more thrust to get off from the ground!
so general equation says
thrust=drag
weight=lift
but its in theoritical ,practically thrust should be more than drag and lift should be more than weight! than only you can achieve  lift and forward flight!
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« Reply #3 on: August 08, 2010, 12:51:41 AM »
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L'enfant Terrible du RCIndia



but the web says the following

Thrust vs weight

1 : 1 - Is the best for any normal plane , more thrust will ensure a vertical climb capability.
0.5:1 - is the minimum for any plane to fly.

Anything in between should be good for a trainer, but it will increase the take off and reduce maneuverability in the air when it is low.

This is a very important piece of information. Could you please give us a link to the website where you got it from?

Cheers!
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« Reply #4 on: August 08, 2010, 12:58:50 AM »
VC
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L'enfant Terrible du RCIndia



Thrust creates the speed, and the speed helps the aerofoil shape of the wings to create lift. A stationary wing creates zero lift unless the airspeed is enough. If the thrust is not sufficient, speed will be low, drag will not be compensated and enough lift will not be created - the aircraft will not lift off.

I'm rather poor on theory, seniors please correct me if I am stating something wrong.
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« Reply #5 on: August 08, 2010, 01:10:29 AM »
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Hi VC

It is a widely discussed topic...just search thrust vs weight on rcgroups...you will see some good discussions there. Just to add..it is not the speed of the plane but the speed of the air over the wings what matters.

VC...the drag is directly proportional to the sq of the velocity...so is the speed is halfed the drag reduces by 4....what if i blow air over a stationary plane's wings..what do you think the drag will be equal to a plane moving with the same speed???

I am not questioning ur knowledge...but trying to create a debate so that we can improve our knowledge...



Regards
Ankur
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« Reply #6 on: August 08, 2010, 01:26:01 AM »
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it is not the speed of the plane but the speed of the air over the wings what matters.

I am not questioning ur knowledge...but trying to create a debate so that we can improve our knowledge...


1. Speed of the air over the wings (under ideal / still conditions) is directly proportional to the speed at which the aircraft is moving into the wind. That speed is provided by the thrust created by the motor (and the prop pitch). An aircraft always takes off and lands 'into the wind'. Thus, the higher the wind speed, the lower the thrust required to keep the aircraft airborne. Or am I wrong here?

2. If I HAD the knowledge, I wouldn't have been posting on this thread, I would have been sleeping. Grin

Go ahead and keep this discussion going, so that we can all learn!

Cheers!
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« Reply #7 on: August 08, 2010, 01:48:41 AM »
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this may give us a better picture:

http://www.av8n.com/how/htm/4forces.html
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« Reply #8 on: August 08, 2010, 10:03:51 AM »
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VC sir actually speed of air flowing above the wing will be more than speed incoming in any case ,but underneath the wing will be same ,thats why there will be a velocity and pressure diffrence

coming to taking off into wind ,think you are taking off with wind(tailwind) you need more runway and tailwind will disrupt laminar flow over the wing there by reducing lift, and due to less lift you can not pull hard to gain height which will lead to stall thats why you will be floating till to end of the runway!

i think any real world pilots in this forum can put some words on it as they have real experience!

small book which will guide to all the things regarding aircraft mechanics which is used by both Pilots and Engineers

Pearson Education's "Mechanics of Flight"

i think all in this forum should have one ,very useful! Smiley
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