Wing incidence question
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Wing incidence question
I've been told that a wing on a plane with a high wing (example Q-Tee as pictured) should have positive incidence. To me that means the front of the wing is angled up compared to the horizonal plane of the plane. If that is true, is there a rule of thumb how many degrees?
Has anyone flown a plane with negitive incidence? What are the flight charteristics of negitive incidence? It is my understanding that if a plane has positive incidence and there is a negitive downthrust on the motor, it puts a .....????.... downward or pre load on the wing which makes it fly much stablier than if everything set a "0". Am I makng any sence. Explaining is my shortfall. Any truth to this? Terry
#2
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RE: Wing incidence question
This will probably require more explanation than I can give but I will give it a shot.
The incedence is relative to the horizontal flying surfaces. A positive wing incedence will be seen as the leading edge of the wing higher than the trailing edge. This is while the hor. stabilizer is neutral.
The same effect can be had by leaving the wing neutral and having negative incedence on the stabilizer. That is the LE of the stab being lower than the TE of the stab.
Down thrust and right thrust on the engine being a seperate issue.
Ideally there should be neutral incedence on all of these for efficiancy however they are sometimes required for our purposes.
A racing plane has these things closer to neutral than sport type planes. They also require a good deal more attention to fly.
Positive incedence is usually designed into a plane to increase available lift and also to do so at slower flying speeds. This will allow quicker take offs and lower stall speeds. This is something beginners can benefit from.
Thbe more positive incedence, the greater effect on the lift and stall speed, up to a point. Remember that as you increase the incedence, you also increase drag.
As for negative wing incedence, I don't recall any designs right off that have any. There may be some biplanes where one wing may have negative incedence but if so, the other will have positive incedence.
Another note is that by having either positive or negative incedence adds to the overall drag of the plane. For a plane you want to slip through the air quickly as a race plane, this is not desireable. A trainer or other type plane where speed is not the priority, this drag is not so detrimental.
I hope this helps some, Robert
The incedence is relative to the horizontal flying surfaces. A positive wing incedence will be seen as the leading edge of the wing higher than the trailing edge. This is while the hor. stabilizer is neutral.
The same effect can be had by leaving the wing neutral and having negative incedence on the stabilizer. That is the LE of the stab being lower than the TE of the stab.
Down thrust and right thrust on the engine being a seperate issue.
Ideally there should be neutral incedence on all of these for efficiancy however they are sometimes required for our purposes.
A racing plane has these things closer to neutral than sport type planes. They also require a good deal more attention to fly.
Positive incedence is usually designed into a plane to increase available lift and also to do so at slower flying speeds. This will allow quicker take offs and lower stall speeds. This is something beginners can benefit from.
Thbe more positive incedence, the greater effect on the lift and stall speed, up to a point. Remember that as you increase the incedence, you also increase drag.
As for negative wing incedence, I don't recall any designs right off that have any. There may be some biplanes where one wing may have negative incedence but if so, the other will have positive incedence.
Another note is that by having either positive or negative incedence adds to the overall drag of the plane. For a plane you want to slip through the air quickly as a race plane, this is not desireable. A trainer or other type plane where speed is not the priority, this drag is not so detrimental.
I hope this helps some, Robert
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RE: Wing incidence question
Thanks Bob. I agree with what you say. If you have down thrust in the motor and excessive positive incidence in the wing, it will require more power as there is much more drag.
I got this info from the old timers I flew with 20 years ago. I'm not sure exactually how they did it, but their 2 channel planes would fly pretty much hands off, full throttle( high wing type planes). When the engine ran out of gas, the plane would still pretty much fly hands off. I mean it wouldn't start diving. It would glide great while only using the rudder and elev once and a while just as landing. When the motor quit, you could see the nose of the plane go up a little. They must have had quite a bit of down thrust to make it do that. ...??? Terry
I got this info from the old timers I flew with 20 years ago. I'm not sure exactually how they did it, but their 2 channel planes would fly pretty much hands off, full throttle( high wing type planes). When the engine ran out of gas, the plane would still pretty much fly hands off. I mean it wouldn't start diving. It would glide great while only using the rudder and elev once and a while just as landing. When the motor quit, you could see the nose of the plane go up a little. They must have had quite a bit of down thrust to make it do that. ...??? Terry
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RE: Wing incidence question
Hi again I may have gotten a little side tracked with hands off and the diehidrel and not asking exatually the right question. I realize the more diehiedrel the plane has the easier it flies hands off the transmitter. The question I have and wondering how the old timers did it is after their plane ran out of gas, you could see the nose go up slightly and glide to a landing and rarely you would have to touch the elevator except to flare it just before touching down.
My planes now days, as soon as it runs out of gas, I have to give it up elevator to keep it from going into a dive. I doesn't go straight down but maybe 20-30 deg. I can't for the life of me remember what those old timers did to make it a nearly hands off elevator landing. How about your plane? What does it do after it runs out of gas? Anyone got any ideas?
Terry
My planes now days, as soon as it runs out of gas, I have to give it up elevator to keep it from going into a dive. I doesn't go straight down but maybe 20-30 deg. I can't for the life of me remember what those old timers did to make it a nearly hands off elevator landing. How about your plane? What does it do after it runs out of gas? Anyone got any ideas?
Terry
#5
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RE: Wing incidence question
The wing will seek its' own AOA due to airfoil, wingloading and air speed. Setting up a "battle" between the wing, the thrust line and the tail-plane doesn't benefit the model. Some designs that have very low or high thrust lines require "gimmicks" to get the plane to fly right, but designs like this give the pilot a speed dependent work load.
A good flying model plane shouldn't need trim changes that are speed dependent, but adding elevator when coming in for a landing is normal.
If your planes are diving to the ground when dead stick, the number 1 cause is nose heavyness. The model should maintain it's attitude without much input until it is almost time to touch down.
A good flying model plane shouldn't need trim changes that are speed dependent, but adding elevator when coming in for a landing is normal.
If your planes are diving to the ground when dead stick, the number 1 cause is nose heavyness. The model should maintain it's attitude without much input until it is almost time to touch down.
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RE: Wing incidence question
Hi CP. The model is balanced where is should be. I can see having to give a little elev just before touch down, but it doesn't seem you should have to hold elev all the way down. Maybe I'm wrong but it doesn't sound right. Terry
#7
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RE: Wing incidence question
When balancing a model the CG listed is not a law handed down by God. This is a starting point that is close to where you need to be. I gotta go with CP and say you need to shift your balance point back just a tad. You should see a marked improvement in the responsiveness of the plane when you do.
Your plane if balanced and trimmed properly should require no extra input from you to have a nice smooth glide.
Robert
Your plane if balanced and trimmed properly should require no extra input from you to have a nice smooth glide.
Robert
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RE: Wing incidence question
Hi Guys. Thanks for the ideas. I'll try moving the CG, it does made sence and seems logical..
Build Light, since it dives after the motor dies, did you mean move the wing forward instead of back? Terry
#10
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RE: Wing incidence question
Terry, most times after the plane is built, moving the wing is not easy. If it is then this would be preferable to adding ballast weight to achieve balance.
If you can move the wing, for your condition, move it forward just a tiny bit. No more than a quarter of an inch. Even that may be to much as your balance is really not very far from being 'spot on' You need to just fine tune your balance. For a plane which is experiencing more severe problems moving the wing would be more appropriate.
I do think in your case you might do something else like moving your battery pack back a little if possible. This can usually be done a little at a time without adding ballast weight or moving the wing.
Remember yours is not far from being just right so a very little bit of change could mean a lot in performance and handling.
There are other things to check as well like the battery pack or other inside goodies shifting around inside thus making changes to your CG Make sure that everyyhing is secure! Sometimes even a hand launch can shift things that you 'thought' were secure. A sudden nose in can even if there were no other damage cause something to move inside. Recheck your balance from time to time.
Don't forget that warpage of flight surfaces can play into this as well.
When your plan is all trimmed out like you like it, is the elevator flat with the stab? or is it pointed down? Or up?
Incedence is very important but it isint everything. To quote CP's last post:
"Problems can also come at you from different angles at the same time. "
He is exactly right. There can be more forces at work here!
Keep us informed!
Robert
If you can move the wing, for your condition, move it forward just a tiny bit. No more than a quarter of an inch. Even that may be to much as your balance is really not very far from being 'spot on' You need to just fine tune your balance. For a plane which is experiencing more severe problems moving the wing would be more appropriate.
I do think in your case you might do something else like moving your battery pack back a little if possible. This can usually be done a little at a time without adding ballast weight or moving the wing.
Remember yours is not far from being just right so a very little bit of change could mean a lot in performance and handling.
There are other things to check as well like the battery pack or other inside goodies shifting around inside thus making changes to your CG Make sure that everyyhing is secure! Sometimes even a hand launch can shift things that you 'thought' were secure. A sudden nose in can even if there were no other damage cause something to move inside. Recheck your balance from time to time.
Don't forget that warpage of flight surfaces can play into this as well.
When your plan is all trimmed out like you like it, is the elevator flat with the stab? or is it pointed down? Or up?
Incedence is very important but it isint everything. To quote CP's last post:
"Problems can also come at you from different angles at the same time. "
He is exactly right. There can be more forces at work here!
Keep us informed!
Robert
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RE: Wing incidence question
The weather isn't going to be good for the next few days but I'll let you know. When the plane is balanced, the all surfaces are flat and straight. I'll experment and let you know. Terry