Coming Soon: Canards
10-22-2008, 12:01 AM
#151
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see post 146 again. for a degreed engineer there are some fundamental errors here.
mk
mk
10-22-2008, 01:04 AM
#153
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What happens when you change the gear ratio of the plane's final drive?
This thread has:
This thread has:
10-22-2008, 01:15 AM
#154
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Golden Retrivers,, I know theres a message in there somewhere Hacker............ Is this kinda like beatin your head against the wall.
I learned my lesson
I learned my lesson
10-22-2008, 01:22 AM
#155
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Actually, for some reason I did a google image search for "plane" and found an airplane full of dogs and I thought of this thread, since it has completely "Gone To The Dogs"
10-22-2008, 01:55 AM
#157
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10-22-2008, 02:27 AM
#158
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10-22-2008, 02:57 AM
#159
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Ok, last one
Original quotes in order, to facilitate clarity:
This is fundamentally incorrect. Elevators and canards are used to balance an aircraft about its' center of gravity. <picture left out for brevity>
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
You must have misunderstood the comment. elevators and canards are used to set the angle of attack of the main wing. You say what i have said, at the end of your statement.
Also, a canard and and elevators can have downforce or up force depending of whether you want their forces to lift the nose or the tail up or down. on straight and level flight you are right .
you keep on loosing the point of the entire discussion. its about, what do the wings or canards do on the front of a car or airplane ?
You are correct, I was misled by the way you stated "you can get an airplane to .... by use of elevators or canards". Push on this one, we're both speaking the same language.
Your point about the gliders. I mentioned that the limit of gliders speed was a structural limitation. thanks for the half credit though!
I'm going to have to take that half point away, I went back through all the posts in this thread and you didn't mention the speed limitation due to structural limitation.
veritical component of lift, or negative lift, or downforce, arent they the same thing? semantics! common, if you are going to be a know-it-all, you are going to have to do better than that.
No. Negative lift and downforce can be used interchangeably, but "Vertical component of lift" does not = downforce. I'll come back to this one later when I address your response to Glenn's comment.
Yikes! Repeat after me: Airplanes don't fall - they accelerate down (unless the wing "stalls" and makes no lift). Also, if you are "falling ballistically", then you (the observer/pilot/aircraft) experiences 0 g.
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
And birds don't really do this.
The point was is that you can pull negative Gs and go down faster than the force of gravity. that was the ONLY point of that. Now, airplanes dont fall? what the heck does that mean? if you are in a dive, you accelerate at a rate of 32f/s/s, (in a vacuum) however,not in a vacuum you will accelerate at some lower rate due to the net force going down as speed increases. at terminal velocity, (somewhere generally, between 140 and 200mph), you dont accelerate anymore, and you as the pilot will experience 1g again. I ment to say a reverse split S which i thought was a half roll and a positive G dive. I think you say the same thing twice above referencing an Immelmann manuever. you pull up and do a half roll at the end of you half loop.
Yup, you were right about the first part, why didn't you just say it like that? The "airplanes don't fall" coment was a pilot joke, sorry. There is no such thing as a "reverse split S". There are two complementary maneuvers. A Split-S goes down and an Immelman goes up. They are not the same maneuver. The outcome of the two maneuvers is drastically different, think about the end altitude and airspeed, not just heading. Don't argue terminology with a pilot, you'll only end up confused 
You are correct, so say it that way and leave it at that.
Ok, now I will address post 146 (which is here)
Your words are mostly correct, but your physics is not. Repeat after me: f=ma.
If there is a net force acting on the aircraft, as you say here:
"a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity."
then there will be an acceleration. In a "steady rate of decent", there is no acceleration, so therefore the forces must be balanced, so there is no "differential force of gravity".
No "downforce" is required for an aircraft to descend, just like no downforce is required for a glider to escape a thermal. You just reduce your vertical component of lift (not to zero, and certainly not negative) until your weight is greater than your lift, and viola, you descend. You can push over to negative g and do all of the above (plus make everyone on the aircraft sick), but it is not required. And this is what Glenn was trying to say, and was 100% correct in the way he said it.
Oh, and one more thing. Gravity is not a force, it is an acceleration field. Google "gravity is not a force" if you don't believe me. I believe one of the direct quotes is from Einstein himself.
F=ma == W=mg
If you feel like arguing further, imagine how you would feel if I tried to argue the correct line around Laguna Seca with you.
Glenn, feel free to correct me if I screwed anything up.
Cheers,
-Jason
The point i was trying to make with my comments was that a plane needs negative lift, or downforce, if he wants to do an outside loop, or wants to go "down" in excess of the force of gravity. you can get an airplane to go down at greater than 0g, and even 1g or better, by use of the elevators,(canards on the rear of the airplane) or canards, (elevators on the front of the airplane)
Of note is a conventional tail has downforce, and a canard will always have upforce (lift) due to the balance about the CG.
When the elevators (or canards) are moved, it rotates the aircraft about its' center of gravity putting the main wing at a different angle of attack to the relative wind. This change is angle of attack is what causes the aircraft to climb or decend.
Also, a canard and and elevators can have downforce or up force depending of whether you want their forces to lift the nose or the tail up or down. on straight and level flight you are right .
you keep on loosing the point of the entire discussion. its about, what do the wings or canards do on the front of a car or airplane ?
Only half score here Mark. High aspect ratio wings have lower induced drag, but higher parasite drag (compared to a lower aspect ratio wing with the same surface area). And because of the high aspect ratio wings, gliders generally have a lower maximum allowable airspeed before the wings rip off.
If you want to go down faster than 1 G, you just push down on the stick. you can then not only fall at 1G, you can fall at as fast as the airplane has structure to support negative Gs (as well as your brains ability to get the blood out! )
However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
However, if you want to pull hard Gs, faster than just a free fall, you would do a combat aircraft manuver to reverse directions, and keep G loading positive on the wings. Learned from Birds, they roll over and do an "Emmelman".
However, negative Gs, such as found when doing an outside loop gets you down much faster than gravity, as you are then able to convert potetial energy of your airplane based on its altitude to kinetic energy (speed of decent) and fall (dive) far faster !
Most tactical (fighter) aircraft are stressed to +9/-3 g. Why? Because the human body can stand about those limits. So if you want to get down in a hurry, you roll inverted, and pull 9g. If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)
And birds don't really do this.
Ok, now I will address post 146 (which is here)
BZZZT. Wrong answer. 1/2 credit. yes, if lift is less than weight the aircraft will ( or can) accelerate downward proportional to the net force due to gravity minus lift, + weight - drag. However, this is progressivly less as the airplane approachs terminal velocity. (remember,drag goes up with the square of speed. double the speed, quad the drag.)
Lift equal to weight creates steady altitude flight.
a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity.
The pilot must vary the elevator (canard) setting to keep any particular rate of decent constant ,
Lift equal to weight creates steady altitude flight.
a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity.
The pilot must vary the elevator (canard) setting to keep any particular rate of decent constant ,
If there is a net force acting on the aircraft, as you say here:
"a steady rate of decent would equal a differential force of gravity and weight plus lift, and the force of drag dictating its terminal velocity."
then there will be an acceleration. In a "steady rate of decent", there is no acceleration, so therefore the forces must be balanced, so there is no "differential force of gravity".
No "downforce" is required for an aircraft to descend, just like no downforce is required for a glider to escape a thermal. You just reduce your vertical component of lift (not to zero, and certainly not negative) until your weight is greater than your lift, and viola, you descend. You can push over to negative g and do all of the above (plus make everyone on the aircraft sick), but it is not required. And this is what Glenn was trying to say, and was 100% correct in the way he said it.
Oh, and one more thing. Gravity is not a force, it is an acceleration field. Google "gravity is not a force" if you don't believe me. I believe one of the direct quotes is from Einstein himself.
F=ma == W=mg
If you feel like arguing further, imagine how you would feel if I tried to argue the correct line around Laguna Seca with you.
Glenn, feel free to correct me if I screwed anything up.
Cheers,
-Jason
10-22-2008, 09:31 AM
#160
Team Owner
Jason, your gonna see, you will be banging your head against the wall, as there never seems to be any way to get a point across, Its like trying to taxi with the wheels chocked and the tail tied down. Or trying to rotate with the gust lock installed. LOL
10-22-2008, 10:07 AM
#161
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Or trying to fly a plane in a vacuum.
Differential gravity.
I swear I hit some of that when I drink too much.
10-22-2008, 01:00 PM
#163
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man, this thing got way out of control, mainly due to the term "downforce" which can have many different defiinitions and uses.
by the way, gravity is a force.
common defintion:
"The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity which is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found by the equation:
Fgrav = m * g
where g = 9.8 m/s2 (on Earth)
and m = mass (in kg)"
Now, what glen was saying was wrong. you cant have acceleration downward, unless you have a constant net force . Yes, F=ma. You know I know this equation better than most!
. He even said that if lift force equaled gravity force, you would have a constant decent , and that is just wrong. you know that there are things like parasitic drag, drag due to lift and these factors go up and down (with speed). Parasitic drag goes up, and lift due to drag goes down as speed goes up, and this is usually due to the angle of attack being less as speed goes up. In a decent,if you have a constant rate of decent, the forces will be tradiing off. a straight dive at termal velocity is a constant rate of decent. (no acceleration).
whenever i was talking about a plane going down, i was associated that effect with downforce. It didnt matter if it was due to gravity or a canard, elevator interaction. The point of this was to show that a canard can be a symetrical or non semetrical airfoil and it produces forces in both directions based on its angle of attack.
As far as the aerobatic manuvers, ive forgoten their names. I used to fly a lot, and havent in many years now. With a father that was a airforce fighter pilot, airline pilot and avid private pilot, I got my share of flying. The point there was to understand that you can push over an upright plane, and create negative Gs. more Gs than gravity alone, even though the wings were symetrical. anyway, you said:
"If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)"
These both sounds like Immelmans to me. a split S was (i thought ) a 1/2 roll and a half loop dive. sure, i do know they have different outcomes.
If we just had an aero discussion, things would be a lot more clear and clear for those reading this. incorporating the "downforce" term has created some confusuion it seems.
mk
by the way, gravity is a force.
common defintion:
"The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity which is directed "downward" towards the center of the earth. The force of gravity on earth is always equal to the weight of the object as found by the equation:
Fgrav = m * g
where g = 9.8 m/s2 (on Earth)
and m = mass (in kg)"
Now, what glen was saying was wrong. you cant have acceleration downward, unless you have a constant net force . Yes, F=ma. You know I know this equation better than most!
. He even said that if lift force equaled gravity force, you would have a constant decent , and that is just wrong. you know that there are things like parasitic drag, drag due to lift and these factors go up and down (with speed). Parasitic drag goes up, and lift due to drag goes down as speed goes up, and this is usually due to the angle of attack being less as speed goes up. In a decent,if you have a constant rate of decent, the forces will be tradiing off. a straight dive at termal velocity is a constant rate of decent. (no acceleration). whenever i was talking about a plane going down, i was associated that effect with downforce. It didnt matter if it was due to gravity or a canard, elevator interaction. The point of this was to show that a canard can be a symetrical or non semetrical airfoil and it produces forces in both directions based on its angle of attack.
As far as the aerobatic manuvers, ive forgoten their names. I used to fly a lot, and havent in many years now. With a father that was a airforce fighter pilot, airline pilot and avid private pilot, I got my share of flying. The point there was to understand that you can push over an upright plane, and create negative Gs. more Gs than gravity alone, even though the wings were symetrical. anyway, you said:
"If you keep pulling and end up straight and level going the opposite direction, this is called a "Split-S". (An Immelman is the opposite - a 1/2 loop starting level and going up - named after a WWI German fighter pilot)"
These both sounds like Immelmans to me. a split S was (i thought ) a 1/2 roll and a half loop dive. sure, i do know they have different outcomes.
If we just had an aero discussion, things would be a lot more clear and clear for those reading this. incorporating the "downforce" term has created some confusuion it seems.
mk
10-22-2008, 01:11 PM
#164
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sorry....
10-22-2008, 01:21 PM
#165
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Jason you will find that Mark is never wrong......just misunderstood He presents a constantly shifting target and ALWAYS gets in the last word ! Need not be correct or accurate , simply the last word. Remember those who race MUST believe that they can WIN the race or they would not race and if they do not win it was because some one else had a better car , more money , new tires , a pit crew , or there was a Voodo Doll in their image with pins stuck in it. This should complete the hijacking of this thread
He presents a constantly shifting target and ALWAYS gets in the last word ! Need not be correct or accurate , simply the last word. Remember those who race MUST believe that they can WIN the race or they would not race and if they do not win it was because some one else had a better car , more money , new tires , a pit crew , or there was a Voodo Doll in their image with pins stuck in it. This should complete the hijacking of this thread