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Flite Test STEM

400 MPH + RC JET

Zoom Master

Zoom Master

Elite member
For now im gonna focus on breaking the 200 mph barrier breaking that barrier with a jet turbine is a piece of cake but with a electric motor its just that much harder...........
 
Houndpup Rc

Houndpup Rc

Legendary member
khuzaima said:
For now im gonna focus on breaking the 200 mph barrier breaking that barrier with a jet turbine is a piece of cake but with a electric motor its just that much harder...........
Click to expand...
Jet turbines have other things to worry about though.....And BTW have you looked at the price of the fuel? Keep in mind that electric motors are free every time, because you just charge a battery...Unless you crash! JK:ROFLMAO::ROFLMAO:
 
telnar1236

telnar1236

Elite member
Houndpup Rc said:
You mean the skill involved in driving those speeds?
Click to expand...
At 400 mph skill, power, and structural strength are the main impediments. I've already mentioned the skill and reaction times.

In terms of power, I saw 16x more being mentioned. To be a bit more precise with the wording, you need 16x more thrust but 64x more power assuming a constant efficiency (which is a bad assumption with turbines). Thrust needs to be equal to your drag to achieve a given speed. Drag is given by 1/2*rho*u^2*S*Cd (half of the density of air times the speed of your plane squared times the reference area (generally wing area for a plane) times the coefficient of drag) so 4x faster means 16x more drag and therefore 16x more thrust. Power is thrust times speed so you need to multiply by 4 again to get 64x more power.

In terms of structural strength, to fly in a given area, a 400 mph plane needs to be about 16x stronger than a 100 mph plane (in practice you might be able to get away with slightly less by changing the way you fly but it still needs to be much stronger). All the pressures on the plane will scale with the square of the speed as will the g force required to turn in a given radius.

At 500 mph things get even worse. You're starting to approach the speed of sound at that speed and the way air behaves starts to be somewhat different. At 400 mph, air will still more or less behave about the same as at lower speeds and even at 500 mph you still mostly get the same behavior. However, your plane is pushing air out of the way as it moves which makes the air speed up in some places (e.g. the top of the wing, the control surfaces, some parts of the fuselage) and as soon as some of that air exceeds the speed of sound relative to your plane stuff behaves totally differently and unless the plane is carefully designed it becomes impossible to control. You don't need to fully understand what happens/why to break through these speeds but doing so without that understanding is pretty risky.
 
Houndpup Rc

Houndpup Rc

Legendary member
telnar1236 said:
At 400 mph skill, power, and structural strength are the main impediments. I've already mentioned the skill and reaction times.

In terms of power, I saw 16x more being mentioned. To be a bit more precise with the wording, you need 16x more thrust but 64x more power assuming a constant efficiency (which is a bad assumption with turbines). Thrust needs to be equal to your drag to achieve a given speed. Drag is given by 1/2*rho*u^2*S*Cd (half of the density of air times the speed of your plane squared times the reference area (generally wing area for a plane) times the coefficient of drag) so 4x faster means 16x more drag and therefore 16x more thrust. Power is thrust times speed so you need to multiply by 4 again to get 64x more power.

In terms of structural strength, to fly in a given area, a 400 mph plane needs to be about 16x stronger than a 100 mph plane (in practice you might be able to get away with slightly less by changing the way you fly but it still needs to be much stronger). All the pressures on the plane will scale with the square of the speed as will the g force required to turn in a given radius.

At 500 mph things get even worse. You're starting to approach the speed of sound at that speed and the way air behaves starts to be somewhat different. At 400 mph, air will still more or less behave about the same as at lower speeds and even at 500 mph you still mostly get the same behavior. However, your plane is pushing air out of the way as it moves which makes the air speed up in some places (e.g. the top of the wing, the control surfaces, some parts of the fuselage) and as soon as some of that air exceeds the speed of sound relative to your plane stuff behaves totally differently and unless the plane is carefully designed it becomes impossible to control. You don't need to fully understand what happens/why to break through these speeds but doing so without that understanding is pretty risky.
Click to expand...
Wow! Very interesting!...And a bit mind blowing....
 
Zoom Master

Zoom Master

Elite member
Houndpup Rc said:
Jet turbines have other things to worry about though.....And BTW have you looked at the price of the fuel? Keep in mind that electric motors are free every time, because you just charge a battery...Unless you crash! JK:ROFLMAO::ROFLMAO:
Click to expand...
yeah I know paying for fuel will make me start crying every time.......
 
Zoom Master

Zoom Master

Elite member
telnar1236 said:
At 400 mph skill, power, and structural strength are the main impediments. I've already mentioned the skill and reaction times.

In terms of power, I saw 16x more being mentioned. To be a bit more precise with the wording, you need 16x more thrust but 64x more power assuming a constant efficiency (which is a bad assumption with turbines). Thrust needs to be equal to your drag to achieve a given speed. Drag is given by 1/2*rho*u^2*S*Cd (half of the density of air times the speed of your plane squared times the reference area (generally wing area for a plane) times the coefficient of drag) so 4x faster means 16x more drag and therefore 16x more thrust. Power is thrust times speed so you need to multiply by 4 again to get 64x more power.

In terms of structural strength, to fly in a given area, a 400 mph plane needs to be about 16x stronger than a 100 mph plane (in practice you might be able to get away with slightly less by changing the way you fly but it still needs to be much stronger). All the pressures on the plane will scale with the square of the speed as will the g force required to turn in a given radius.

At 500 mph things get even worse. You're starting to approach the speed of sound at that speed and the way air behaves starts to be somewhat different. At 400 mph, air will still more or less behave about the same as at lower speeds and even at 500 mph you still mostly get the same behavior. However, your plane is pushing air out of the way as it moves which makes the air speed up in some places (e.g. the top of the wing, the control surfaces, some parts of the fuselage) and as soon as some of that air exceeds the speed of sound relative to your plane stuff behaves totally differently and unless the plane is carefully designed it becomes impossible to control. You don't need to fully understand what happens/why to break through these speeds but doing so without that understanding is pretty risky.
Click to expand...
True but to be completely honest with u im first gonna start out small and break the 200 mph barrier and then break the 300 mph barrier which shouldn't be to hard to do and after that I will see if I even want to continue with this project. Because after this questions will start getting answered like, Do I even wanna go that fast ?, Can I handle the speeds ?, Can I afford it ?, Am I interested in going faster or happy with 300 mph ?
 
Houndpup Rc

Houndpup Rc

Legendary member
khuzaima said:
True but to be completely honest with u im first gonna start out small and break the 200 mph barrier and then break the 300 mph barrier which shouldn't be to hard to do and after that I will see if I even want to continue with this project. Because after this questions will start getting answered like, Do I even wanna go that fast ?, Can I handle the speeds ?, Can I afford it ?, Am I interested in going faster or happy with 300 mph ?
Click to expand...
Good idea (y)
 
Houndpup Rc

Houndpup Rc

Legendary member
khuzaima said:
no not sure I was thinking maybe a speed gun but something that goes in the plane would be great.......
Click to expand...
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Zoom Master

Zoom Master

Elite member
Zoom Master

Zoom Master

Elite member
Houndpup Rc said:
yup!
Click to expand...
telnar1236 said:
At 400 mph skill, power, and structural strength are the main impediments. I've already mentioned the skill and reaction times.

In terms of power, I saw 16x more being mentioned. To be a bit more precise with the wording, you need 16x more thrust but 64x more power assuming a constant efficiency (which is a bad assumption with turbines). Thrust needs to be equal to your drag to achieve a given speed. Drag is given by 1/2*rho*u^2*S*Cd (half of the density of air times the speed of your plane squared times the reference area (generally wing area for a plane) times the coefficient of drag) so 4x faster means 16x more drag and therefore 16x more thrust. Power is thrust times speed so you need to multiply by 4 again to get 64x more power.

In terms of structural strength, to fly in a given area, a 400 mph plane needs to be about 16x stronger than a 100 mph plane (in practice you might be able to get away with slightly less by changing the way you fly but it still needs to be much stronger). All the pressures on the plane will scale with the square of the speed as will the g force required to turn in a given radius.

At 500 mph things get even worse. You're starting to approach the speed of sound at that speed and the way air behaves starts to be somewhat different. At 400 mph, air will still more or less behave about the same as at lower speeds and even at 500 mph you still mostly get the same behavior. However, your plane is pushing air out of the way as it moves which makes the air speed up in some places (e.g. the top of the wing, the control surfaces, some parts of the fuselage) and as soon as some of that air exceeds the speed of sound relative to your plane stuff behaves totally differently and unless the plane is carefully designed it becomes impossible to control. You don't need to fully understand what happens/why to break through these speeds but doing so without that understanding is pretty risky.
Click to expand...
Yeah after talking to a lot of people on rc groups iv decided that its easier and better for me to try to first break a lower speed record maybe build a plane that goes 300 mph and then move up to 400 or even 500...........
 
Zoom Master

Zoom Master

Elite member
Houndpup Rc said:
Jet turbines have other things to worry about though.....And BTW have you looked at the price of the fuel? Keep in mind that electric motors are free every time, because you just charge a battery...Unless you crash! JK:ROFLMAO::ROFLMAO:
Click to expand...
Yeah fuel prices have def gone up like crazy and I know jet turbine fuel is hella expensive.
 
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