Crow Vs. Gyro to Stop UF Snaps
11-09-2017, 10:34 AM
#27
Wow.. Lots of misunderstanding here.. CG has almost zero effect upon an airplanes stall tendencies. Airplanes stall because of 2 things.. Critical angle of attack or insufficient airspeed (generally leading to critical angle of attack). Now if your CG is too far back, your pitch rate can become uncontrollable (due to static instability). Too far forward, and you begin to lack elevator/tail power to effect pitch changes, the most common situation being running out of elevator to land properly.. which often causes a bounce. Granted this is somewhat an oversimplification of things, but CG really only affects stability.
Tip stall is simply one wing stalling before the other. If it's always the same wing, the wing is probably not straight, or the tip has a higher angle of attack than the root (wash-in), or you're skidding around with yaw input. Crow helps fix this because it reduces the angle of attack at the wingtip vs the root, causing the root to stall first, which has less rolling force because of the moment arm relative to the wingtip.
Tip stall is simply one wing stalling before the other. If it's always the same wing, the wing is probably not straight, or the tip has a higher angle of attack than the root (wash-in), or you're skidding around with yaw input. Crow helps fix this because it reduces the angle of attack at the wingtip vs the root, causing the root to stall first, which has less rolling force because of the moment arm relative to the wingtip.
The two are just barely linked. Now.. to be completely accurate, there is a change in stall speed with CG change, but it's so small that I doubt you could detect it outside of a wind tunnel. What happens is.. As the CG changes forward the pitching moment of the wing increases, and more downforce is required to hold a given angle of attack. That change in downforce from the tail requires the wing to counteract the reduction in lift from the tail for level flight(yes, the tail does provide some lift), so yes, an increase in angle of attack is required. BUT, we're talking miniscule amounts here. For reference, a Cessna 172, at the most forward CG at 2400 pounds, compared to the most rearward CG allowed, changes the stall speed by 1 knot. One.
I would have to disagree on the CG not having the ability to affect tip stalling tendencies. Move the CG back enough, and ANY airplane is going to snap and stall and make it unflyable. As a matter of fact, a tail heavy airplane is nasty to fly and is one of my worst nightmares.
I've only had the classic flash and that summavitch HATED being tail heavy. I had smoke tanks behind the CG and if I didn't run them dry, trying to land was like watching shamoo porpoise all across the tank. I don't know how I landed that thing like that. I never let that happen again.
Crow is used all the time in airplanes to produce SPECIFIC results. Most notably, gliders used crow to spot land. And we use it RC-jets for the exact same reason!
Crow is solving the tip stalling with the flash for many folks, so if your flash is doing that to you, then it can likely help yours!
11-09-2017, 11:01 AM
#28
Originally Posted by Doug Cronkhite 
Wow.. Lots of misunderstanding here.. CG has almost zero effect upon an airplanes stall tendencies. Airplanes stall because of 2 things.. Critical angle of attack or insufficient airspeed (generally leading to critical angle of attack). Now if your CG is too far back, your pitch rate can become uncontrollable (due to static instability). Too far forward, and you begin to lack elevator/tail power to effect pitch changes, the most common situation being running out of elevator to land properly.. which often causes a bounce. Granted this is somewhat an oversimplification of things, but CG really only affects stability.
Tip stall is simply one wing stalling before the other. If it's always the same wing, the wing is probably not straight, or the tip has a higher angle of attack than the root (wash-in), or you're skidding around with yaw input. Crow helps fix this because it reduces the angle of attack at the wingtip vs the root, causing the root to stall first, which has less rolling force because of the moment arm relative to the wingtip.
Wow.. Lots of misunderstanding here.. CG has almost zero effect upon an airplanes stall tendencies. Airplanes stall because of 2 things.. Critical angle of attack or insufficient airspeed (generally leading to critical angle of attack). Now if your CG is too far back, your pitch rate can become uncontrollable (due to static instability). Too far forward, and you begin to lack elevator/tail power to effect pitch changes, the most common situation being running out of elevator to land properly.. which often causes a bounce. Granted this is somewhat an oversimplification of things, but CG really only affects stability.
Tip stall is simply one wing stalling before the other. If it's always the same wing, the wing is probably not straight, or the tip has a higher angle of attack than the root (wash-in), or you're skidding around with yaw input. Crow helps fix this because it reduces the angle of attack at the wingtip vs the root, causing the root to stall first, which has less rolling force because of the moment arm relative to the wingtip.
Dear Sir,
I would have to disagree on the CG not having the ability to affect tip stalling tendencies. Move the CG back enough, and ANY airplane is going to snap and stall and make it unflyable. As a matter of fact, a tail heavy airplane is nasty to fly and is one of my worst nightmares.
I've only had the classic flash and that summavitch HATED being tail heavy. I had smoke tanks behind the CG and if I didn't run them dry, trying to land was like watching shamoo porpoise all across the tank. I don't know how I landed that thing like that. I never let that happen again.
Crow is used all the time in airplanes to produce SPECIFIC results. Most notably, gliders used crow to spot land. And we use it RC-jets for the exact same reason!
Crow is solving the tip stalling with the flash for many folks, so if your flash is doing that to you, then it can likely help yours!
I would have to disagree on the CG not having the ability to affect tip stalling tendencies. Move the CG back enough, and ANY airplane is going to snap and stall and make it unflyable. As a matter of fact, a tail heavy airplane is nasty to fly and is one of my worst nightmares.
I've only had the classic flash and that summavitch HATED being tail heavy. I had smoke tanks behind the CG and if I didn't run them dry, trying to land was like watching shamoo porpoise all across the tank. I don't know how I landed that thing like that. I never let that happen again.
Crow is used all the time in airplanes to produce SPECIFIC results. Most notably, gliders used crow to spot land. And we use it RC-jets for the exact same reason!
Crow is solving the tip stalling with the flash for many folks, so if your flash is doing that to you, then it can likely help yours!
First, there is only ONE thing that makes a wing stall (not two things) - that is exceeding the critical angle of attack. That is the ONLY thing that makes a wing stall, period, end of sentence. Furthermore, the critical angle of attack is a function of the wing's physical shape, and nothing else. A wing can be stalled at any airspeed by exceeding the critical angle of attack.
Now it is easier to exceed the critical angle of attack at low airspeeds because at low airspeeds, the wing is working at a higher angle of attack in order to produce the lift needed to keep the aircraft from decending. Thus it only takes a small increase in angle of attack to exceed the critical angle and stall the wing.
Second, moving the CG back does NOT change the stall characteristics of the aircraft - because it doesn't change the shape of the wing, it simply makes it easier to get to the critical angle by reducing the downforce that the elevator needs to produce to get to that angle. The tendency to "snap", or drop a wing in a stall is again a function of the wing shape - that being such that the tips stall before the root and generally since both tips don't stall at *exactly* the same time, a large rolling motion is imparted when one stalls first before the other.
It is correct that crow on the ailerons reduces the effective angle of attack of the wing where the aileron is located (usually, but not always at the tip) and thus delays the tendency of the wing to tip stall. That is one of the reasons that it is effective in making some planes, like the Flash and some Hawk models, land better. It also kills some of the lift of the wing overall and thus makes the aircraft decend better at lower throttle settings - like spoilers. That picture of the airliner landing with the aileron raised is for its spoiler effect - like the rest of the spoilers raised on that wing...
As others have said above, try some crow on your Flash - it will make it easier to land consistently. That's *exactly* why BV calls for crow on the King Cat...
Bob
Last edited by rhklenke; 11-09-2017 at 11:04 AM.
11-09-2017, 02:58 PM
#29
A good discussion. I am learning things here. Thanks Bob Doug and others.
My theory on why a forward CG can cause handling problems in the landing phase..
If the CG is too forward on final approach it becomes difficult to raise the nose and slow down. If we can't pull the nose up to flare, we end up touching down too fast, resulting in a bounced landing, which can be very nasty with a Bandit, and I assume, a Flash.
The next time we fly, we try to fly the entire approach much slower, in an attempt to touch down at the correct speed. We get too slow, and the tip stall occurs..
I know that my Bandit handles much better, with the CG back in its correct position. And the good handling characteristics, makes speed control, (attitude) easier, especially on approach
Just a theory.
My theory on why a forward CG can cause handling problems in the landing phase..
If the CG is too forward on final approach it becomes difficult to raise the nose and slow down. If we can't pull the nose up to flare, we end up touching down too fast, resulting in a bounced landing, which can be very nasty with a Bandit, and I assume, a Flash.
The next time we fly, we try to fly the entire approach much slower, in an attempt to touch down at the correct speed. We get too slow, and the tip stall occurs..
I know that my Bandit handles much better, with the CG back in its correct position. And the good handling characteristics, makes speed control, (attitude) easier, especially on approach
Just a theory.
11-09-2017, 04:55 PM
#30
A good discussion. I am learning things here. Thanks Bob Doug and others.
My theory on why a forward CG can cause handling problems in the landing phase..
If the CG is too forward on final approach it becomes difficult to raise the nose and slow down. If we can't pull the nose up to flare, we end up touching down too fast, resulting in a bounced landing, which can be very nasty with a Bandit, and I assume, a Flash.
The next time we fly, we try to fly the entire approach much slower, in an attempt to touch down at the correct speed. We get too slow, and the tip stall occurs..
I know that my Bandit handles much better, with the CG back in its correct position. And the good handling characteristics, makes speed control, (attitude) easier, especially on approach
Just a theory.
My theory on why a forward CG can cause handling problems in the landing phase..
If the CG is too forward on final approach it becomes difficult to raise the nose and slow down. If we can't pull the nose up to flare, we end up touching down too fast, resulting in a bounced landing, which can be very nasty with a Bandit, and I assume, a Flash.
The next time we fly, we try to fly the entire approach much slower, in an attempt to touch down at the correct speed. We get too slow, and the tip stall occurs..
I know that my Bandit handles much better, with the CG back in its correct position. And the good handling characteristics, makes speed control, (attitude) easier, especially on approach
Just a theory.
A forward CG makes raising the nose harder, especially at low airspeeds, so it would make sense that having the CG at the "right point" vs. too far forward would help make an accurate flare easier.
Bob
11-09-2017, 06:32 PM
#31
Great discussion on this thread. I've always preferred to have a slightly aft CG as it allows nice slow approaches and the ability to flare. I notice many modelers like to fly nose heavy planes.
11-09-2017, 09:51 PM
#32
180 flights and heavy at take off 5.4L of fuel Atj 190sv landing with about 1.5L you have to be careful but it's never snapped be gentle on the elevator it will reward you with longevity.
11-09-2017, 10:39 PM
#33
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Well I'll tell ya where the cg needs to be. Period. Take off the canopy, empty fuel, and it should just set on the tail, I mean just, set on the tail.
I lost my first Ultra flash because I had the CG set too far forward. It snapped and went into the ground, nothing left.
On one of my Classic Flashes I kept bouncing the landings, never could get it right, cuz I had the CG too far forward.
Then I learned where it had to be. I never measure cg on a Flash now. No canopy, set on the tail, Flys perfect everytime.
Also, no matter what Dave sez, (sorry bro), I run crow on full flaps on my UF. ALWAYS. So as flaps go to full, up goes the ailerons and down goes the elevator, for a hands off (virtually) base to final.
Hope this helps somebody, sure sure helped me.....Thx Gary
slpn
I lost my first Ultra flash because I had the CG set too far forward. It snapped and went into the ground, nothing left.
On one of my Classic Flashes I kept bouncing the landings, never could get it right, cuz I had the CG too far forward.
Then I learned where it had to be. I never measure cg on a Flash now. No canopy, set on the tail, Flys perfect everytime.
Also, no matter what Dave sez, (sorry bro), I run crow on full flaps on my UF. ALWAYS. So as flaps go to full, up goes the ailerons and down goes the elevator, for a hands off (virtually) base to final.
Hope this helps somebody, sure sure helped me.....Thx Gary
slpn
11-10-2017, 09:34 AM
#35
I have had the classic flash and currently have the UF with M140. Never had a tip stall. If it bounces on landing it's coming in hot. If it tip stalls, it's too slow. Gyro will not help with tip stalls. It will mask the early signs of tip stall (like a wing wiggle). I have 4-5mm crow with 3.6" of flap and that helps a lot during landing. If I remember correctly my CG is at 225mm. The UF is easier to land then my Bandit since the Bandit is more sensitive to speed when landing. It will kill itself once the bounce starts. Ultra flash can fly slow but not as slow as the bandit. Also the UF needs to be trimmed well during slow flight with flaps down and crow. I have found if not trimmed correctly and CG forward, I would constantly fight with it on the final stages of landing with porpoising. Set CG aft a bit and trim with gear down and full flaps (and crow) on a landing pattern and it's very predictable.
Hope it all works out.
Hope it all works out.
11-10-2017, 12:04 PM
#36
I do 1/4" crow on all my sport jets. Makes them feel heavier and more solid on landing. On my last UF ( burned down due to engine fire 
) i had second mix on a slider switch to add even more for conditions where I had no headwind.. I had a 160 engine on it and it just did not want to slow down ( to my taste 
) .. I have my 2nd UF almost RTF, and this time it has a 140 engine with a lot less idle thrust, so i hope the 1/4 " crow is to my satisfaction.
I never liked gyros on sport jets. I think it takes the "feel" out of them. On scale jets I like the gyro strictly for taking out the wobbles and making the flight more realistic looking.
) i had second mix on a slider switch to add even more for conditions where I had no headwind.. I had a 160 engine on it and it just did not want to slow down ( to my taste ) .. I have my 2nd UF almost RTF, and this time it has a 140 engine with a lot less idle thrust, so i hope the 1/4 " crow is to my satisfaction.I never liked gyros on sport jets. I think it takes the "feel" out of them. On scale jets I like the gyro strictly for taking out the wobbles and making the flight more realistic looking.
11-10-2017, 02:48 PM
#37
Thread Starter
The CG on mine is set back at 222mm from the front wing to fuse joint. Gear up or down does not seem to change it much. The GC in the Manual's looks to be very close to my setting.
I have moved the CG slightly forward and back with little change related to the UF's tendency to snap. I do not use crow as I have never needed it before with the sprint nor on any one of the several giant prop planes I fly. Given that most commenters are telling me they add crow, I am leaning toward there being a design problem and the crow is a Band-Aid. I can land it and fly it just fine. It is just not a comfortable plane for me to fly and that takes the fun out of it. I'll try the crow.
As far as the bouncing, I have figured out that If I keep the nose up and let it settle by itself, then it does not bounce. That technique was reliable the last couple times I flew it.
The only real problem left is the snapping. I think it is occurring at speeds that are fast enough to fly, especially as I can immediately recover from the snaps w/o adding speed. I will try some crow. But, we now have snow on the ground and 20 degrees F. So it is building time. This B.S. with this jet has me building a couple prop planes this winter. They are a lot more predictable and fun, for me.
As far as using the rudder. I do tend to add rudder on turns. On the turn from base to final approach, I add in a small amount of rudder to help keep the plane more towards upright. I do this to try to avoid the snap or at least be in a better position to recover. Maybe I need to stop using rudder when the flaps are down on approach until squarely in the final.
As far as total weight, it weighs 24.6 pounds on the Xicoy Scales. I'll take a look at the Aileron trim to see if lateral balance is spot on. But If I recall correctly. there was no aileron trim required and the weight showing on the Mains on the Xiocy were identical.
I have moved the CG slightly forward and back with little change related to the UF's tendency to snap. I do not use crow as I have never needed it before with the sprint nor on any one of the several giant prop planes I fly. Given that most commenters are telling me they add crow, I am leaning toward there being a design problem and the crow is a Band-Aid. I can land it and fly it just fine. It is just not a comfortable plane for me to fly and that takes the fun out of it. I'll try the crow.
As far as the bouncing, I have figured out that If I keep the nose up and let it settle by itself, then it does not bounce. That technique was reliable the last couple times I flew it.
The only real problem left is the snapping. I think it is occurring at speeds that are fast enough to fly, especially as I can immediately recover from the snaps w/o adding speed. I will try some crow. But, we now have snow on the ground and 20 degrees F. So it is building time. This B.S. with this jet has me building a couple prop planes this winter. They are a lot more predictable and fun, for me.
As far as using the rudder. I do tend to add rudder on turns. On the turn from base to final approach, I add in a small amount of rudder to help keep the plane more towards upright. I do this to try to avoid the snap or at least be in a better position to recover. Maybe I need to stop using rudder when the flaps are down on approach until squarely in the final.
As far as total weight, it weighs 24.6 pounds on the Xicoy Scales. I'll take a look at the Aileron trim to see if lateral balance is spot on. But If I recall correctly. there was no aileron trim required and the weight showing on the Mains on the Xiocy were identical.
11-10-2017, 03:01 PM
#38
I have to disagree with that IMHO. The plane is an incredible design for high speed flight and hard G precise aerobatics. The aero of the wing is best suited to this, just like most super-cars are tuned to drive fast and hard, they wont be great/comfortable at lower speeds like a more traditional car... by using crow, you are changing the way the wing flies, basically punting it into a different mode making it more stable to land .. same way with newer super-cars that incorporate selectable driving modes that electronically alter performance and handling ( engine settings, suspension height, response, electro/hydraulics stabilazers. etc )
UF can be the best of both worlds, but you cant take a plane that is built to fly and land slow and steady and make it a razor precise rocket at speed. Bobcat/Kingcat would be good examples. Land great, and fly great ... at speed, not as precise and have thrust line and control coupling issues ... even these use crow
11-10-2017, 03:05 PM
#39
The only real problem left is the snapping. I think it is occurring at speeds that are fast enough to fly, especially as I can immediately recover from the snaps w/o adding speed.
11-10-2017, 03:57 PM
#40
The CG on mine is set back at 222mm from the front wing to fuse joint. Gear up or down does not seem to change it much. The GC in the Manual's looks to be very close to my setting.
I have moved the CG slightly forward and back with little change related to the UF's tendency to snap. I do not use crow as I have never needed it before with the sprint nor on any one of the several giant prop planes I fly. Given that most commenters are telling me they add crow, I am leaning toward there being a design problem and the crow is a Band-Aid. I can land it and fly it just fine. It is just not a comfortable plane for me to fly and that takes the fun out of it. I'll try the crow.
As far as the bouncing, I have figured out that If I keep the nose up and let it settle by itself, then it does not bounce. That technique was reliable the last couple times I flew it.
The only real problem left is the snapping. I think it is occurring at speeds that are fast enough to fly, especially as I can immediately recover from the snaps w/o adding speed. I will try some crow. But, we now have snow on the ground and 20 degrees F. So it is building time. This B.S. with this jet has me building a couple prop planes this winter. They are a lot more predictable and fun, for me.
As far as using the rudder. I do tend to add rudder on turns. On the turn from base to final approach, I add in a small amount of rudder to help keep the plane more towards upright. I do this to try to avoid the snap or at least be in a better position to recover. Maybe I need to stop using rudder when the flaps are down on approach until squarely in the final.
As far as total weight, it weighs 24.6 pounds on the Xicoy Scales. I'll take a look at the Aileron trim to see if lateral balance is spot on. But If I recall correctly. there was no aileron trim required and the weight showing on the Mains on the Xiocy were identical.
I have moved the CG slightly forward and back with little change related to the UF's tendency to snap. I do not use crow as I have never needed it before with the sprint nor on any one of the several giant prop planes I fly. Given that most commenters are telling me they add crow, I am leaning toward there being a design problem and the crow is a Band-Aid. I can land it and fly it just fine. It is just not a comfortable plane for me to fly and that takes the fun out of it. I'll try the crow.
As far as the bouncing, I have figured out that If I keep the nose up and let it settle by itself, then it does not bounce. That technique was reliable the last couple times I flew it.
The only real problem left is the snapping. I think it is occurring at speeds that are fast enough to fly, especially as I can immediately recover from the snaps w/o adding speed. I will try some crow. But, we now have snow on the ground and 20 degrees F. So it is building time. This B.S. with this jet has me building a couple prop planes this winter. They are a lot more predictable and fun, for me.
As far as using the rudder. I do tend to add rudder on turns. On the turn from base to final approach, I add in a small amount of rudder to help keep the plane more towards upright. I do this to try to avoid the snap or at least be in a better position to recover. Maybe I need to stop using rudder when the flaps are down on approach until squarely in the final.
As far as total weight, it weighs 24.6 pounds on the Xicoy Scales. I'll take a look at the Aileron trim to see if lateral balance is spot on. But If I recall correctly. there was no aileron trim required and the weight showing on the Mains on the Xiocy were identical.
You are nose heavy, the symptons you describe are the same as others when they were near the 220mm CG, I followed suggestions from others flying at 235mm and I do not have the wing drop problems, and I do not use crow, do a search here, you’ll read about people using alleged CG’s as far back as 245mm (don’t take this as a recommendation) I use the 235mm CG, that will cause your jet to sit on it’s tail when empty of fuel and with no canopy as stated before. My UF weights a bit over 24 pounds
Last edited by Ruizmilton; 11-10-2017 at 04:02 PM.
11-10-2017, 04:47 PM
#41
Second, moving the CG back does NOT change the stall characteristics of the aircraft - because it doesn't change the shape of the wing, it simply makes it easier to get to the critical angle by reducing the downforce that the elevator needs to produce to get to that angle. The tendency to "snap", or drop a wing in a stall is again a function of the wing shape - that being such that the tips stall before the root and generally since both tips don't stall at *exactly* the same time, a large rolling motion is imparted when one stalls first before the other.
It is correct that crow on the ailerons reduces the effective angle of attack of the wing where the aileron is located (usually, but not always at the tip) and thus delays the tendency of the wing to tip stall. That is one of the reasons that it is effective in making some planes, like the Flash and some Hawk models, land better. It also kills some of the lift of the wing overall and thus makes the aircraft decend better at lower throttle settings - like spoilers. That picture of the airliner landing with the aileron raised is for its spoiler effect - like the rest of the spoilers raised on that wing...
As others have said above, try some crow on your Flash - it will make it easier to land consistently. That's *exactly* why BV calls for crow on the King Cat...
Bob
It is correct that crow on the ailerons reduces the effective angle of attack of the wing where the aileron is located (usually, but not always at the tip) and thus delays the tendency of the wing to tip stall. That is one of the reasons that it is effective in making some planes, like the Flash and some Hawk models, land better. It also kills some of the lift of the wing overall and thus makes the aircraft decend better at lower throttle settings - like spoilers. That picture of the airliner landing with the aileron raised is for its spoiler effect - like the rest of the spoilers raised on that wing...
As others have said above, try some crow on your Flash - it will make it easier to land consistently. That's *exactly* why BV calls for crow on the King Cat...
Bob
I found your explanation very instructive, thanks, it does make a lot of sense, yet while visualizing the explanation, something came to mind and since I have no education on aerodynamics, I thought it would be of benefit to me to understand, so here it goes;
I did get the reasoning on critical angle of attack, wing shape and CG relationship, this was easy to understand on a straight wing, where for example, with wingtip washout, as the critical angle of attack is reached, the center of the wing stalls first, while the tips are still producing lift, yet since the wing is straight, in a perfect world, the lift generated by the wingtips would be exherted in line with the CG thus not affecting the behavior of the aircraft in any way.
Please correct me if any of my statements is wrong in the past paragraph or the next.
Now lets suppose the wing is swept, this will cause a somewhat wider CG range, but still less than the width of the wing sweep, would, under the same circumstances as above, because the airfoil on the wingtips is behing the airfoil on the root, this cause the center of lift to move around the wing, thus moving behing the CG at some point? Would this not cause undesired behavior at any point as the critical angle of attack is reached and the center of lift (or is it pressure?, just guessing, pardon my ignorance) moves away from the CG? What would the airplane do under these circumstances?
Is this the way I state it, or it just does not work that way?
Last edited by Ruizmilton; 11-10-2017 at 04:54 PM.
11-10-2017, 05:46 PM
#42
When I as the question on Google I get this answer, as BB320, this is how I understand it, I prefer an aft CG as much as possible especially with a heavy aircraft also I understand that the angle where a stall occurs will be reached sooner with a forward CG, if that is the case with the UF then move the CG back to tame it on landings.
The only way to continue level flight is to increase angle of attack in order to increase lift – that means that for the same aircraft weight, a forward C.G. will cause you to fly at a higher angle of attack and thus closer to the critical angle of attack, and therefore you increase the stall speed.
The only way to continue level flight is to increase angle of attack in order to increase lift – that means that for the same aircraft weight, a forward C.G. will cause you to fly at a higher angle of attack and thus closer to the critical angle of attack, and therefore you increase the stall speed.
Last edited by CARS II; 11-10-2017 at 06:08 PM.
11-10-2017, 06:33 PM
#43
I have heard the argument about crow or no crow as long as I have been flying models. It works well on most models. Is it necessary? no, Is it a flaw in the design that makes it necessary, No. But it is a very viable technique on light wing loaded models that allow the Fuselage to increase the AOA, give it stability, and washout, and drag..
On the UF, a lot of guys fly it without, but if you add Crow and reduce a little flap, it will Set up better, fly slower, and won't be as tip snappy.. IT works on a Bandit equally as well, and I heard guys for years argue that it doesn't need. it. Recently I put crow on the EVO. I couldn't find anyone that uses it on that jet, but EVERY video I saw of it, had it dipping the nose and coming in flat.. Just like the UF does with 55 deg flap and no crow.. Same as Kingcat, viper..stinger, etc..
I even use it on my T-28.. In each case, it gives artificial AOA to the model and allows the mains to more easily touch down first and flare..
So try to keep an open mind about it, and don't say " it wasn't designed to use crow" or all that BS.. give it a try..
On my UF, by the way, the CG was behind 230. Kept the nose from falling so easily at or near stall speeds..
Moving the CG Aft of course doesn't affect the stall angle, but it big time affects what happens when the Tail can't fly anymrore, and down comes the nose.. You all have seen how a real nose heavy plane is more prone for an accelerated stall.. thats a tail stall actually.. the Tail cannot counteract the weight in front of CG.. so by moving the CG back, the load on the tail is less, allowing the plane to fly more easily at or near max AOA.
When you add crow to the model in this case, it will reduce the tendency of tip stall, but also gives the tail a little assist to hold nose up. it adds a slight downforce to the tail.
goose..
Last edited by gooseF22; 11-10-2017 at 06:44 PM.
11-10-2017, 07:07 PM
#45
11-11-2017, 08:42 PM
#47
Well, the 1/2 inch of crow on the ailerons worked just fine, two flights today and the touchdown point was very predictable, the added drag kept the Boomer descending without picking up any more speed and that made the touchdown more predictable.
I had the Boomer for a while but till now I get to have fun with it
I had the Boomer for a while but till now I get to have fun with it
11-12-2017, 07:17 AM
#48
Thread Starter
I have over 200 flights on my Sprint. Never used crow. I have flown it with a pound of lead in the nose and no lead at all. I land with and without its "Flap." I land it very hot and very slow. IMHO If the pilot has any Jet or EDF experience, they fly themselves no matter how we set them up. They are fun and relaxing to fly. Good for early morning warmups too.
Not to much comment about gyros other than they can compound the transition into a stall. ??
Not to much comment about gyros other than they can compound the transition into a stall. ??
11-12-2017, 08:10 AM
#49
My Feedback: (13)
There are a lot of guys smarter than me out there so there's my disclaimer. That said I have a lot of flights on classic and UFs. I tried no crow when the UF first came out. I subsequently added it and loved it.
Design flaw/bandaid/whatever. Honestly who cares This is a hobby and meant to be fun...if we can increase the fun, why not? Sure, The wing could probably be molded with just a touch more washout at the tip. FS planes have a lot of that. Goose, our vipers have it, eagles and raptors all. Some different reasons for that which aren't germane here but the FS manufacturers do it (heck, look at the trailing edge of a C172 some time...washout is there). If you're unhappy with what is a snappy plane throw some crow in there (which acts as washout) and watch how much more stable the plane is.
I ran 235 or so on the cg (I can get the actual number out of my balancer if anyone needs) and the airplane was rock solid down final with no tendency to tip stall
One of the reasons for flaps on a FS is to lower the deck angle so you can see over the nose coming down final. If you reverse that (i.e. Kick the trailing edge up like crow) it increases the deck angle a bit. Since we don't care about seeing over the nose that's not a big concern but since we do care about touching a Nosegear first that's another benefit to crow in my mind
Someone above said a wing can stall at any airspeed. That in my mind is a partial answer. If you look at an EM diagram for a plane the left portion of the curve is the stall line. It goes up to a peak, and then comes back down the right side which is the G line. Past a certain airspeed you will over G before you stall with known consequences
Maybe that helps, maybe I've input more chaff!
Design flaw/bandaid/whatever. Honestly who cares This is a hobby and meant to be fun...if we can increase the fun, why not? Sure, The wing could probably be molded with just a touch more washout at the tip. FS planes have a lot of that. Goose, our vipers have it, eagles and raptors all. Some different reasons for that which aren't germane here but the FS manufacturers do it (heck, look at the trailing edge of a C172 some time...washout is there). If you're unhappy with what is a snappy plane throw some crow in there (which acts as washout) and watch how much more stable the plane is.
I ran 235 or so on the cg (I can get the actual number out of my balancer if anyone needs) and the airplane was rock solid down final with no tendency to tip stall
One of the reasons for flaps on a FS is to lower the deck angle so you can see over the nose coming down final. If you reverse that (i.e. Kick the trailing edge up like crow) it increases the deck angle a bit. Since we don't care about seeing over the nose that's not a big concern but since we do care about touching a Nosegear first that's another benefit to crow in my mind
Someone above said a wing can stall at any airspeed. That in my mind is a partial answer. If you look at an EM diagram for a plane the left portion of the curve is the stall line. It goes up to a peak, and then comes back down the right side which is the G line. Past a certain airspeed you will over G before you stall with known consequences
Maybe that helps, maybe I've input more chaff!
Last edited by ozief16; 11-12-2017 at 08:18 AM. Reason: Readability
11-12-2017, 08:15 AM
#50
Well, the 1/2 inch of crow on the ailerons worked just fine, two flights today and the touchdown point was very predictable, the added drag kept the Boomer descending without picking up any more speed and that made the touchdown more predictable.
I had the Boomer for a while but till now I get to have fun with it
I had the Boomer for a while but till now I get to have fun with it
I use Cortex on most all my planes now and crow on most.. It makes every one of them more fun to fly.. they are all locked in.. You should see the Big HH T-28 with crow and Gyro.. It is transforming.. When I let others fly it, I get all kinds of comments about how it goes exactly where its pointed, and how easy it is to land.. it will knife edge easily, and you can use rudder without it being dippy or snappy. Flies hands off easily.
Yes, its a little more money to add Gyro, but the combination of Crow and Gyro makes for some nice experience..
PS.. I don't give a Rip what the "purists" say.. When I hand them the transmitter, they usually enjoy the jet the way its set up.