Pattern trimming 101
08-28-2008, 08:24 PM
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Pattern trimming 101
I'd like to take this time to start a thread where possibly we can get all trim issues and theories behind them in one place.
Let's get some facts (As I know them, I'm probably wrong as will be pointed out shortly) out in the open right at the start.
1. A symmetrical wing must fly at a positive incidence to generate lift.
2. All airplanes rotate around ONE point, they do pivot in three axis true (Pitch, Roll, Yaw) but always around one point somewhere in the middle of the airplane.
Can we call that point CG?
3. The wing produces lift, the stab and vertical fin are there to stabilize the wing. The rudder, elev and ailerons are there to drive the wing in a different direction.
IE The farther we place the stab from the wing the more stable the airplane is, the closer, the less so.
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
Now I've read all I can find on why a pattern plane will pitch to the gear if tail heavy, I'm still not clear on this one.
I've also read as much as I can on why a pull to the canopy either up or down is cured by a more positive wing. To me this would require more down elev trim which when unloaded in knife edge should push the nose even more to the gear?
Why would a Yaw input cause the nose to drop?
If moving the CG forward we must use more up elev trim to bring the wing more positive?
By moving the CG back and forth all we're doing is changing the center of lift or pressure on the wing?
My head is hurting trying to wrap my brain around this.
Anyone else care to chime in?
Tim
Let's get some facts (As I know them, I'm probably wrong as will be pointed out shortly) out in the open right at the start.
1. A symmetrical wing must fly at a positive incidence to generate lift.
2. All airplanes rotate around ONE point, they do pivot in three axis true (Pitch, Roll, Yaw) but always around one point somewhere in the middle of the airplane.
Can we call that point CG?
3. The wing produces lift, the stab and vertical fin are there to stabilize the wing. The rudder, elev and ailerons are there to drive the wing in a different direction.
IE The farther we place the stab from the wing the more stable the airplane is, the closer, the less so.
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
Now I've read all I can find on why a pattern plane will pitch to the gear if tail heavy, I'm still not clear on this one.
I've also read as much as I can on why a pull to the canopy either up or down is cured by a more positive wing. To me this would require more down elev trim which when unloaded in knife edge should push the nose even more to the gear?
Why would a Yaw input cause the nose to drop?
If moving the CG forward we must use more up elev trim to bring the wing more positive?
By moving the CG back and forth all we're doing is changing the center of lift or pressure on the wing?
My head is hurting trying to wrap my brain around this.
Anyone else care to chime in?
Tim
08-28-2008, 08:45 PM
#2
RE: Pattern trimming 101
good god what a great idea. i can trim a plane to fly level but moving the cg back to prevent or increase roll coupling or any other pattern terms that i see all the time is something i need a beginners course on. how do i balance a plane to fly inverted hands off anyway. thx tim.
david
david
08-28-2008, 08:57 PM
#3
RE: Pattern trimming 101
Well, I can certainly use all the help I can get... This link is to Bryan Hebert's trim method, figured it might as well get posted early. Someone could also reference Peter Goldsmith's articles and the NSRCA trim chart as well.
http://www.hebertcompetitiondesigns....ngulation.html
Mark
http://www.hebertcompetitiondesigns....ngulation.html
Mark
08-28-2008, 09:06 PM
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RE: Pattern trimming 101
I think the largest problem we have as pilots is the ability to know the difference between a trim problem and a pilot induced problem. This is why I always get a better pilot than myself to fly the airplane so I can watch and see if the same thing happens with them flying it. If so then I consider it a trim problem.
Tim
Tim
08-29-2008, 05:37 AM
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RE: Pattern trimming 101
Thomas,
If you join after October 1st you will get your membership for the remainder of 2008 plus all of 2009.
After you join I will do everything I can to round up the August back issue and personally mail it to you.
Maybe even the earlier issue with Bryan's article.
What a deal, huh?
[sm=thumbup.gif]
[sm=thumbup.gif]
JLK
If you join after October 1st you will get your membership for the remainder of 2008 plus all of 2009.
After you join I will do everything I can to round up the August back issue and personally mail it to you.
Maybe even the earlier issue with Bryan's article.
What a deal, huh?
[sm=thumbup.gif]
[sm=thumbup.gif]JLK
08-29-2008, 06:20 AM
#8
RE: Pattern trimming 101
ORIGINAL: jlkonn
Thomas,
If you join after October 1st you will get your membership for the remainder of 2008 plus all of 2009.
After you join I will do everything I can to round up the August back issue and personally mail it to you.
Maybe even the earlier issue with Bryan's article.
What a deal, huh?
[sm=thumbup.gif][sm=thumbup.gif]
JLK
Thomas,
If you join after October 1st you will get your membership for the remainder of 2008 plus all of 2009.
After you join I will do everything I can to round up the August back issue and personally mail it to you.
Maybe even the earlier issue with Bryan's article.
What a deal, huh?
[sm=thumbup.gif]
[sm=thumbup.gif]JLK
sounds like a deal to me
i almost pushed the order button for the subscription, till i noticed it was only good to the end of the year. even after 16 years in the hobby, I dont get how almost everything in RC costs the same for 12 months of the year or 6 months of the year... but ohh well 
08-29-2008, 06:26 AM
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RE: Pattern trimming 101
Thomas,
Wait 'til October then you'll get the rest of 2008 and all 2009.
Let me know when you join and I'll get the back issues to you.
We've (the NSRCA board, I'm the D5 vp...don't be too impressed...I'm the only guy that volunteered) has talked about
prorating the dues in some way be we haven't finalized anything.
Let me know when you sign up!
JLK
Wait 'til October then you'll get the rest of 2008 and all 2009.
Let me know when you join and I'll get the back issues to you.
We've (the NSRCA board, I'm the D5 vp...don't be too impressed...I'm the only guy that volunteered) has talked about
prorating the dues in some way be we haven't finalized anything.
Let me know when you sign up!
JLK
08-29-2008, 07:04 AM
#10
RE: Pattern trimming 101
ORIGINAL: jlkonn
Thomas,
Wait 'til October then you'll get the rest of 2008 and all 2009.
Let me know when you join and I'll get the back issues to you.
We've (the NSRCA board, I'm the D5 vp...don't be too impressed...I'm the only guy that volunteered) has talked about
prorating the dues in some way be we haven't finalized anything.
Let me know when you sign up!
JLK
Thomas,
Wait 'til October then you'll get the rest of 2008 and all 2009.
Let me know when you join and I'll get the back issues to you.
We've (the NSRCA board, I'm the D5 vp...don't be too impressed...I'm the only guy that volunteered) has talked about
prorating the dues in some way be we haven't finalized anything.
Let me know when you sign up!
JLK
sounds great. i'l let ya know.
08-29-2008, 07:10 AM
#11
RE: Pattern trimming 101
Hello MasterTech,.....
I will replay to this but it's going to be long,...and will take several posts to get it accomplished. I know there are a few Aeronautical Engineers/NASA Engineering commrads that fly pattern out there. This should be fun!
The kool thing,.is I can bore you with it all next weekend at the contest in Winston,...HEE HEE,......[X(]
I finially have completed the full CAD drawings of my pattern design called "Serenity" now off to the plotter we go!
Bill Holsten
I will replay to this but it's going to be long,...and will take several posts to get it accomplished. I know there are a few Aeronautical Engineers/NASA Engineering commrads that fly pattern out there. This should be fun!
The kool thing,.is I can bore you with it all next weekend at the contest in Winston,...HEE HEE,......
[X(]I finially have completed the full CAD drawings of my pattern design called "Serenity" now off to the plotter we go!
Bill Holsten
08-29-2008, 08:09 AM
#13
RE: Pattern trimming 101
Peter Goldsmith trimming article: http://www.flagstaffflyers.com/image...thTrimming.pdf
Mike
PS: Please try to keep this one on track, it makes it very difficult to find what you need if we have a lot of irellevant comments.
Mike
PS: Please try to keep this one on track, it makes it very difficult to find what you need if we have a lot of irellevant comments.
08-29-2008, 08:37 AM
#14
RE: Pattern trimming 101
Thats a very nice article for trimming basics,...However, it does not address the aerodynamic questions that MasterTech has posted for answers or ideas.
I don't mean that in a disrespectful way.
Bill Holsten
I don't mean that in a disrespectful way.
Bill Holsten
08-29-2008, 08:44 AM
#15
RE: Pattern trimming 101
ORIGINAL: Mastertech
I'd like to take this time to start a thread where possibly we can get all trim issues and theories behind them in one place.
Let's get some facts (As I know them, I'm probably wrong as will be pointed out shortly) out in the open right at the start.
1. A symmetrical wing must fly at a positive incidence to generate lift.
ALSO Any airfoil must be at a EFFECTIVE positive incidence to make lift
2. All airplanes rotate around ONE point, they do pivot in three axis true (Pitch, Roll, Yaw) but always around one point somewhere in the middle of the airplane.
The rotation (roll) is around the crankshaft C/L
The pitch "centers", depending on CG location
Can we call that point CG?
3. The wing produces lift, the stab and vertical fin are there to stabilize the wing. The rudder, elev and ailerons are there to drive the wing in a different direction.
IE The farther we place the stab from the wing the more stable the airplane is, the closer, the less so.
The more effective the leverage you setup - the more force you will have to change or stabilize- BUT stability is a CG thing.
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
the wing will ALWAYS produce lift -if it is held to an AOA other than ZERO
Now I've read all I can find on why a pattern plane will pitch to the gear if tail heavy, I'm still not clear on this one.
CG
I've also read as much as I can on why a pull to the canopy either up or down is cured by a more positive wing. To me this would require more down elev trim which when unloaded in knife edge should push the nose even more to the gear?
This is A complete fallacy The "positive wing" is simply a referrence line. The wing will fly at an angle it chooses depending on CG/weight n speed . You can change the location relative to the fuselage all yo want -but it will still pick it's own AOA for flight. BUT- the change in related parts (fuselage /stab fin) wil change drag profile -this can change pitch
basically it's a CG thing.
Why would a Yaw input cause the nose to drop?
stab blanking reduces effective tailplane download the more forward the cg-the more this will be seen
If moving the CG forward we must use more up elev trim to bring the wing more positive?
No we are simply attempting to HOLD the correct AOA - there is a very slight increase in effective wing loading as the tailplane operates at a higher AOA (more drag)
By moving the CG back and forth all we're doing is changing the center of lift or pressure on the wing?
No - basically you are basically de stabilizing pitch . You are also moving the CG closer to the CP
My head is hurting trying to wrap my brain around this.
Relax - once you eliminate the mystery of all this the easier it al becomes
there are No secrets to it.
Try this: ALL flight is simply differences in air pressure and nature is always trying to equalize pressure .
all of our fiddlin around with angles of attack/ offsets etc., simply changes relative pressures on the airframe
lift is just higher pressure below and less pressure above a surface
Anyone else care to chime in?
You don't have to agree with any of these additions God only knows you won't be the only one.
Tim
I'd like to take this time to start a thread where possibly we can get all trim issues and theories behind them in one place.
Let's get some facts (As I know them, I'm probably wrong as will be pointed out shortly) out in the open right at the start.
1. A symmetrical wing must fly at a positive incidence to generate lift.
ALSO Any airfoil must be at a EFFECTIVE positive incidence to make lift
2. All airplanes rotate around ONE point, they do pivot in three axis true (Pitch, Roll, Yaw) but always around one point somewhere in the middle of the airplane.
The rotation (roll) is around the crankshaft C/L
The pitch "centers", depending on CG location
Can we call that point CG?
3. The wing produces lift, the stab and vertical fin are there to stabilize the wing. The rudder, elev and ailerons are there to drive the wing in a different direction.
IE The farther we place the stab from the wing the more stable the airplane is, the closer, the less so.
The more effective the leverage you setup - the more force you will have to change or stabilize- BUT stability is a CG thing.
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
the wing will ALWAYS produce lift -if it is held to an AOA other than ZERO
Now I've read all I can find on why a pattern plane will pitch to the gear if tail heavy, I'm still not clear on this one.
CG
I've also read as much as I can on why a pull to the canopy either up or down is cured by a more positive wing. To me this would require more down elev trim which when unloaded in knife edge should push the nose even more to the gear?
This is A complete fallacy The "positive wing" is simply a referrence line. The wing will fly at an angle it chooses depending on CG/weight n speed . You can change the location relative to the fuselage all yo want -but it will still pick it's own AOA for flight. BUT- the change in related parts (fuselage /stab fin) wil change drag profile -this can change pitch
basically it's a CG thing.
Why would a Yaw input cause the nose to drop?
stab blanking reduces effective tailplane download the more forward the cg-the more this will be seen
If moving the CG forward we must use more up elev trim to bring the wing more positive?
No we are simply attempting to HOLD the correct AOA - there is a very slight increase in effective wing loading as the tailplane operates at a higher AOA (more drag)
By moving the CG back and forth all we're doing is changing the center of lift or pressure on the wing?
No - basically you are basically de stabilizing pitch . You are also moving the CG closer to the CP
My head is hurting trying to wrap my brain around this.
Relax - once you eliminate the mystery of all this the easier it al becomes
there are No secrets to it.
Try this: ALL flight is simply differences in air pressure and nature is always trying to equalize pressure .
all of our fiddlin around with angles of attack/ offsets etc., simply changes relative pressures on the airframe
lift is just higher pressure below and less pressure above a surface
Anyone else care to chime in?
You don't have to agree with any of these additions God only knows you won't be the only one.
Tim
08-29-2008, 08:55 AM
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RE: Pattern trimming 101
From Byrans Mind,
"Hi Todd
your flying wayyyyyy tail heavy,
move you c/g forward probably an inch and your dive will go away ,,, Trust me
remember tail heavy elevator will be sensitive and c/g forward elevator is positive and effective around nuetral
it will require very little elevator to mantain inverted flight ,,,,however you might require more over all throw in the end
when you get way back on the c/g the airplane behaves opposite of what you think it should, very confusing.
make sure your wing inc is 1/2 pos to the thrustline of your model and your motor should be 1/2 neg to the thrustline
your c/g should be around 25% of the MAC not in the 30`S where most models are set up
try this and report back please
P.S.you will find your snaps, spins, knife, up and downlines all improve with this setup"
Bryan
"Hi Todd
your flying wayyyyyy tail heavy,
move you c/g forward probably an inch and your dive will go away ,,, Trust me
remember tail heavy elevator will be sensitive and c/g forward elevator is positive and effective around nuetral
it will require very little elevator to mantain inverted flight ,,,,however you might require more over all throw in the end
when you get way back on the c/g the airplane behaves opposite of what you think it should, very confusing.
make sure your wing inc is 1/2 pos to the thrustline of your model and your motor should be 1/2 neg to the thrustline
your c/g should be around 25% of the MAC not in the 30`S where most models are set up
try this and report back please
P.S.you will find your snaps, spins, knife, up and downlines all improve with this setup"
Bryan
08-29-2008, 09:21 AM
#17
RE: Pattern trimming 101
So increasing incidence on the wing reduces the pull to the canopy in up and down lines. Is it safe to assume that increasing the incidence of the wing will also reduce the amount of "up" elevator trim to maintain straight and level flight?
08-29-2008, 09:23 AM
#18
RE: Pattern trimming 101
I agree with you Tim in the sense that trimming gets confusing when you look at all different approaches. Some procedures start with pre-determined incidences (Hebert's) and finish with C.G. while other methods start with C.G. and finish with wing or engine thrust incidences. The confusion gets worst when some trimming charts are not recommended and no one seems to make corrections to them.
I completely understand the fact that all these variables are part of one big mathematical equation of multiple variables f(x,y,z,...) = "ultimate trimming". The issue in finding the solution for such equation, is that all variables are geometry dependant.
Furthermore, can we question if one trimming procedure is applicable to a small set of similar geometries or is it applicable to any geometry?
By geometry I mean the relative dimensional arrangement of wing, stab, fin, engine, not incidences because these are the ones we must adjust to get the best result of the ultimate trimming equation.
Does it make sense? Am I being too scholastic here?
Pedro
I completely understand the fact that all these variables are part of one big mathematical equation of multiple variables f(x,y,z,...) = "ultimate trimming". The issue in finding the solution for such equation, is that all variables are geometry dependant.
Furthermore, can we question if one trimming procedure is applicable to a small set of similar geometries or is it applicable to any geometry?
By geometry I mean the relative dimensional arrangement of wing, stab, fin, engine, not incidences because these are the ones we must adjust to get the best result of the ultimate trimming equation.
Does it make sense? Am I being too scholastic here?
Pedro
08-29-2008, 09:55 AM
#19
RE: Pattern trimming 101
ORIGINAL: Mastertech
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
Tim
4. The wing only generates lift when flying upright or inverted. When flying either up, down or in Knife edge the wing doesn't generate lift.
Tim
The wing always generates lift, whereas she has a minimun AoA ,no matter its position
if you are flying at zero AoA, no lift
start flying with AoA, it will prdoduce lift, no matter you are flying up, down, KE, inverted, normal, etc
08-29-2008, 09:58 AM
#20
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RE: Pattern trimming 101
ORIGINAL: invertmast
So increasing incidence on the wing reduces the pull to the canopy in up and down lines. Is it safe to assume that increasing the incidence of the wing will also reduce the amount of "up" elevator trim to maintain straight and level flight?
So increasing incidence on the wing reduces the pull to the canopy in up and down lines. Is it safe to assume that increasing the incidence of the wing will also reduce the amount of "up" elevator trim to maintain straight and level flight?
We must remember that the stabs are what dirve the airplane around the wing. The wing carrys the weight but the stab/fin drive it where we want it to go.
I have my airplane set at 0-0 ref wing to stab. I'm taking a bunch of weight and some shims with me tomorrow to try different methods. I plan on shimming the wing .25 then .5 compared to the stab. Then try to move the CG forward and see what happens with each change.
Tim
08-29-2008, 10:11 AM
#21
RE: Pattern trimming 101
ORIGINAL: Mastertech
I believe that increasing wing incidence will result in a down elev trim condition. Once the wing is unloaded, ie up/dn the stab now drives the airplane. What I don't understand is how this seemingly backwards condition drives the airplane positive in KE.
We must remember that the stabs are what dirve the airplane around the wing. The wing carrys the weight but the stab/fin drive it where we want it to go.
I have my airplane set at 0-0 ref wing to stab. I'm taking a bunch of weight and some shims with me tomorrow to try different methods. I plan on shimming the wing .25 then .5 compared to the stab. Then try to move the CG forward and see what happens with each change.
Tim
ORIGINAL: invertmast
So increasing incidence on the wing reduces the pull to the canopy in up and down lines. Is it safe to assume that increasing the incidence of the wing will also reduce the amount of "up" elevator trim to maintain straight and level flight?
So increasing incidence on the wing reduces the pull to the canopy in up and down lines. Is it safe to assume that increasing the incidence of the wing will also reduce the amount of "up" elevator trim to maintain straight and level flight?
We must remember that the stabs are what dirve the airplane around the wing. The wing carrys the weight but the stab/fin drive it where we want it to go.
I have my airplane set at 0-0 ref wing to stab. I'm taking a bunch of weight and some shims with me tomorrow to try different methods. I plan on shimming the wing .25 then .5 compared to the stab. Then try to move the CG forward and see what happens with each change.
Tim
ok. so more positive incidence would require more? up elevator? I'm currently running a 1/2pos (wing) and 0 (stab) incidence settings. i've got about 4 flights of up elevator. The plane is tail heavy, and pulls on both up and downlines to the canopy.
I get adjusting the wing to a more positive incidence will eliminate much if not all of the pull, but if it would require more up elevator trim to maintain level flight, wouldn't that just put you back to square one?
Am i confusing anyone else yet?
08-29-2008, 10:13 AM
#22
RE: Pattern trimming 101
ORIGINAL: prgonzalez
I agree with you Tim in the sense that trimming gets confusing when you look at all different approaches. Some procedures start with pre-determined incidences (Hebert's) and finish with C.G. while other methods start with C.G. and finish with wing or engine thrust incidences. The confusion gets worst when some trimming charts are not recommended and no one seems to make corrections to them.
I completely understand the fact that all these variables are part of one big mathematical equation of multiple variables f(x,y,z,...) = "ultimate trimming". The issue in finding the solution for such equation, is that all variables are geometry dependant.
Furthermore, can we question if one trimming procedure is applicable to a small set of similar geometries or is it applicable to any geometry?
By geometry I mean the relative dimensional arrangement of wing, stab, fin, engine, not incidences because these are the ones we must adjust to get the best result of the ultimate trimming equation.
Does it make sense? Am I being too scholastic here?
Pedro
I agree with you Tim in the sense that trimming gets confusing when you look at all different approaches. Some procedures start with pre-determined incidences (Hebert's) and finish with C.G. while other methods start with C.G. and finish with wing or engine thrust incidences. The confusion gets worst when some trimming charts are not recommended and no one seems to make corrections to them.
I completely understand the fact that all these variables are part of one big mathematical equation of multiple variables f(x,y,z,...) = "ultimate trimming". The issue in finding the solution for such equation, is that all variables are geometry dependant.
Furthermore, can we question if one trimming procedure is applicable to a small set of similar geometries or is it applicable to any geometry?
By geometry I mean the relative dimensional arrangement of wing, stab, fin, engine, not incidences because these are the ones we must adjust to get the best result of the ultimate trimming equation.
Does it make sense? Am I being too scholastic here?
Pedro
There are no magic angles or trims or CG setups
But here are two pretty well established "absolutes" for any powered aircraft.
A you physically, can't make em too light -it's just an impossibliity.
B you can't overpower em another real time ,impossible scenario.
so make em as light as possible (lowest wing loading and highest power loading
and go from there
Why?
because you will start with a model capable of flying with the least AOA for any given maneuver.
This means less control input is needed to change or hold any line -at any speed
you can't fool Mother Nature.
08-29-2008, 10:37 AM
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RE: Pattern trimming 101
Hey fellas, it's been a long time since I last played around with my RealFlight simulator, but it did help me tremendously to go in and edit my set-ups, move CG back & forth, crank incidences and thrust angles one way or t'other, and observe the effects (which were quite visible in flight). (Don't forget to adjust wind speed and direction in your experiments.)
I also browsed extensively on aerodynamic websites. There are a few good ones, but it would take me too long to dig them all up again. (They were bookmarked on a now defunct computer.)
I can tell you there are such things as center of gravity, which we all know about, but also center of pressure and aerodynamic center, which are somewhat different. At one time I thought I was beginning to understand how they all work together, but I found it more rewarding to just get my plane so it would fly straight, then go fly it instead of studying esoteric stuff with my math education suffering many decades of erosion.
What works here on RCU seems to be mainly simple rules of thumb. If you can't explain it to everyone's satisfaction in 500 words, well enough that we can all go to the bench, set up our plane, take it out, fly it, trim it, mix it and then everything flies like a Bryan Hebert or a Peter Goldsmith or a Nat Penton or a Dick Hanson, then we are in for a long thread, hairy disputes, and probably many unresolved questions. I don't like to come across as pessimistic, because this stuff can be learned and applied, but it takes careful study, careful thinking, lots of experimenting (like with a flight simulator), lots of flight testing (which cuts into fun flying and practicing for competition) and finally lots of sharpening the eye as well as the mind to see what your plane is doing and figure out why it might be misbehaving in some subtle way. So that's my contribution to this thread. Study, think, experiment, fly, observe... repeat many times.
(By the way, NSRCA really ought to junk that trim chart. Problem is, you'll never get a committee to agree on how to replace it. You need one genius, and there are a few to choose from, to run it like a dictator ... benevolently, of course.)
I also browsed extensively on aerodynamic websites. There are a few good ones, but it would take me too long to dig them all up again. (They were bookmarked on a now defunct computer.)
I can tell you there are such things as center of gravity, which we all know about, but also center of pressure and aerodynamic center, which are somewhat different. At one time I thought I was beginning to understand how they all work together, but I found it more rewarding to just get my plane so it would fly straight, then go fly it instead of studying esoteric stuff with my math education suffering many decades of erosion.
What works here on RCU seems to be mainly simple rules of thumb. If you can't explain it to everyone's satisfaction in 500 words, well enough that we can all go to the bench, set up our plane, take it out, fly it, trim it, mix it and then everything flies like a Bryan Hebert or a Peter Goldsmith or a Nat Penton or a Dick Hanson, then we are in for a long thread, hairy disputes, and probably many unresolved questions. I don't like to come across as pessimistic, because this stuff can be learned and applied, but it takes careful study, careful thinking, lots of experimenting (like with a flight simulator), lots of flight testing (which cuts into fun flying and practicing for competition) and finally lots of sharpening the eye as well as the mind to see what your plane is doing and figure out why it might be misbehaving in some subtle way. So that's my contribution to this thread. Study, think, experiment, fly, observe... repeat many times.
(By the way, NSRCA really ought to junk that trim chart. Problem is, you'll never get a committee to agree on how to replace it. You need one genius, and there are a few to choose from, to run it like a dictator ... benevolently, of course.)
08-29-2008, 07:30 PM
#25
RE: Pattern trimming 101
Put me down as a NO.
When these charts first surfaced, it became apparant to me that as well intended as they were - they could never cover all the situations of all planes for all flyers .
Some of the info works - and how one sorts it out - depends on how well one understands the basics of flight - which some trimmers do and some sorta do and some sorta don't.
It is worth reading tho .
Knowing all the terms used by professional aerodynamicists, and and researhing airfoils etc., this not necessary for you, in order to develop a comprehensive approach to sorting out your model.
I know some will poo poo this idea but a good small aerobatic flat foamie will teach you a LOT about what really does what -
It will also show that some sacred cows in what constitutes a good aerobatic model are simply not so.
When these charts first surfaced, it became apparant to me that as well intended as they were - they could never cover all the situations of all planes for all flyers .
Some of the info works - and how one sorts it out - depends on how well one understands the basics of flight - which some trimmers do and some sorta do and some sorta don't.
It is worth reading tho .
Knowing all the terms used by professional aerodynamicists, and and researhing airfoils etc., this not necessary for you, in order to develop a comprehensive approach to sorting out your model.
I know some will poo poo this idea but a good small aerobatic flat foamie will teach you a LOT about what really does what -
It will also show that some sacred cows in what constitutes a good aerobatic model are simply not so.