Maximizing Flight Performances at Unideal Flight Conditions

[Schrodinger-Cat-8]

Hi, I'm relatively new in the Flight community, and I have some questions on flying in "unideal" flight conditions:
I'm a high school student with a relatively low budget doing flight with a partner (first time), and I've been basically using completely stock JH Stinger Kit's, and I've had pretty good performances with them. I can consistently get above 2 minutes (sometimes slightly below, or sometimes with a miracle above 2:30 closer to 3 minutes) in a 26' gym ceiling, with a lot of luck. My strategy for my gym is the fact that my gym ceiling is flat, which allows me to "bang the ceiling" without too much repercussions (but there are vents that suck things even on a ceiling, which has led to some tragic accidents). However, I'm quickly realizing this configuration isn't going to work because my regional and invitational competition gyms have not only a significantly lower gym height at like 18-23' but also a significantly smaller gym with girders and a chandelier and I haven't managed to adjust to that (I can't give exact dimensions unfortunately, but I think estimating my gym can comfortably fly 2-3 planes while regionals/invitationals should probably only fly 1). I'm suspecting it has to do with the torque, propeller pitch, rubber thickness, left wing washin, and stab tilt.
I'll show some insight on how I'm attempting to tackle these problems, and I'd like to have some advice, thanks in advance!
Regarding my issue with a "smaller turning circle" for a smaller gym:
For my gym, I don't think I've went into it without a heater/AC/something on because the temperature is either boiling hot to very unrealistic trim setups, or an extremely cold gym, which is fine. However, my planes will always drift a certain direction to appear to have a gigantic turning circle, so I can't tell if it's the plane or the gym itself.
The stab tilt is 2.8125 degrees (I think I did the math properly, not sure but I can remeasure tomorrow with an exact measurement).
Regarding torque, propeller pitch, rubber thickness/density, left wing washin:
For some context of my plane, I think in general Stingers have a pretty fast ascension rate, which I should probably address. For my ideal flight configuration at 26', I usually take a stock 3/32' rubber at somewhere ~0.062 g/in wound to max of ~1.0+ torque depending on the calculator and dewind to certain experimenting values (ex. 0.7, 0.6, 0.5.... 0.3). While I have seen differences in rate of ascension, the torque didn't really change the maximum climb height. Changing the rubber thickness/density lower did manage to decrease the altitude of the plane, but at a very significant time cost even when I changed to 0.087' rubber. So I started messing around with prop pitch and I bought a propeller pitch measurement tool from FF, but I don't believe that I'm using it correctly. For some context on why, I'm using JH's guide on trimming linked here (https://www.youtube.com/watch?v=pF2_K4T ... oshuawfinn) to test if the plane can fly decently or not, and when I decreased the propeller pitch a little (or how I perceived it), no matter how much I trimmed it, even ridiculously, the plane couldn't lift with the nose up like it did with a standard Ikera prop. Even though propeller pitch should match rubber density, I believe that a plane conventionally should fly nose up at lower powered flights or test glides (correct me if I'm wrong) . I'd like to have some insight on how to properly use a propeller pitch, thanks in that regard! Also, I've been reading the forums on propeller radius and x'' at y'' radius (x and y are variables that represent numbers), and I'm a little foreign to those terms, so I'd appreciate if I could be referenced to any sources on knowing what it is!
Typical Flight Configuration that I Use:
Stab tilt: 2.8125 degrees (I used trig for this one based on measurements, may be somewhat wrong)
CG: ~10.18 cm from LE
"Front Wing" Incidence: None, JH kits don't have a TE and LE post that is adjustable like FF I think
Stab Wing Incidence: Not sure, but using this guide by JH, (https://www.youtube.com/watch?v=8BKVXRz ... oshuawfinn), I found that using a 1/32'' shim works fine, might vary based on varying gym temperature condition.
Left Wing Washin: Not sure, I'll measure it soon in a couple hours
Propeller Pitch of Stock Ikera Prop: Usually 35-40 degrees fluctuating, I'm not sure if I'm measuring it correctly, but I'd like to see if what I'm measuring is somewhat accurate or if I'm just wrong
Rubber Thickness and Density: 3/32'' and ~0.062 g/in
Rubber Winds: 70-80ish winds on 15:1 winder depending on max turns calc w lubricant ~1.0+ torque dewinded down to x torque
Dewinds: Varies from 2-5 dewinds depending on experimentation, I haven't pinpointed a perfected setup
Rubber Weight: 1.45-49, I haven't exactly figured out how to get it consistent all the time, but I'm almost getting there
Some notes on flights: I've noticed that high torque flights allow this plane to ascend very quickly (~30 sec ascent) and descend slowly (~+1 minute), but dewinding to a lower torque allows it to have a more even distribution, but it didn't help that the plane still managed to ceiling bang at 26'.
Just to sum up my post, I'd like to find out how I can decrease the launch height without sacrificing time, and be more literate with terms in flight in general, especially with propeller pitch and see if I'm using a propeller pitch device correctly. Thanks in advance!
I could provide a video of my plane and how I'm using the prop pitch from FF to give a better perspective.

[coachchuckaahs]

Cat:

You have a lot of things in one post, it may be hard to address. I'll try to address a few things that jump out.

As far as AC/Heat being on, it is difficult to get a good consistent trim. Every HVAC system will affect the room differently, and most will provide a lot of random swirling that makes consistency impossible. You will want to trim for stability (move CG forward, increase wing incidence compared to still air trim) so that disturbances have less effect. Of course this means you understand the basic trim in calm air first. I believe the J&H planes have a saddle that you can shim for incidence adjustments.

For circle size, generally speaking tail tilt has the most impact at slower speeds (cruise adn letdown) which rudder (tail offset) is most effective at higher speeds (climb). At extreme torque a little left thrust may help, but at low ceilings you are probably not at these torque levels. In practice, insufficient tail offset (rudder) will likely cause an oversize circle in all flight phases. We usually will tighten up the overall circle with more tail offset, and then fine tune the slower circle with tail tilt adjustments.

If the plane is not properly trimmed at slow speeds, it may climb too quickly at higher torque. You mentioned trying for a nose-high attitude. You probably want the nose up some, but not a lot. Normally we add decalage until we get a stall and then take a little out. These planes, especially C div, tend to mush through the air with too much decalage, rather than stalling. Perhaps try a little less decalage. While there are not adjustable wing posts, there is a shimmable saddle, and you can measure the leading edge and trailing edge height from the motorstick to get incidence. It is important to know and record such measurements.

As far as the prop adjustment is concerned, you want a pitch/diameter ration of 1.5 to 2. That is a wide range. Generally these planes seem a bit happier on the lower half of this scale.

The pitch gage does not measure pitch, rather it measures pitch angle. You need to convert that to pitch. For example, I believe the FFM Pitch gage has a measurement radius of 3.5" (prop shaft to protractor distance). The pitch is determined as tan(pitch angle)*circumference at measurement point, or tan(P.A.)*(3.5")*2*pi. Then compare this to your prop diameter (9.5") to get the P/D ratio. A helical pitch prop has the same PITCH at every station (position of measurement). The FFM gage is not adjustable so only reads at 3.5". The Ikara props are NOT helical. They have somewhat less twist than a true helical prop would have. So we want to measure at about 2/3 the way out. 3.5" is a decent place to measure, given the prop radius is 4.75". As long as you are consistent in your measurements you have data that YOU can work with. I suspect that your are going too low on pitch. Generally the Ikara props are a decent starting place, but those I have seen if adjusted tend to need more pitch, not less. A couple degrees pitch angle change is significant. I suspect you have made a large change to lower pitch to the point the prop blade ("wings" are not lifting (thrust) much at all.

You want the pitch to be somewhere between 1.5 and 2x the diameter. So diameter is 9.5", you want pitch 15-19 inches at the 2/3 location. That is a wide range. You will have to match that to you rubber, or preferably match your rubber to your pitch. At 3.5" radius (FFM gage if I recall properly), 15" pitch would be 34.3 degrees. 19" pitch would be 41 degrees. I suspect you are much lower than that.

You really need to get hold of the climb, as ceiling banging is not advisable in SO. This is because you only get 2 flights. Ceiling banging can be good on a flat ceiling, but is highly risky in terms of redirecting your plane into a wall. In AMA flying you get 5 official flights and your score is your 1 best flight, so you can take that chance. Not so much in SO.

There is a HUGE difference between 3/32" stock (0.094" wide) and 0.087" wide rubber. While 3/32 could be consistently overpowering and putting you into the ceiling, 0.087 could then not have enough power to climb after initial peak torque runs out, or more importantly, enough power to keep the plane flying in cruise (thus the much shorter times). You do not report turns remaining at the end of the flight. This is the critical information (given climb to same altitude) to compare two rubber density choices (or adjustments to prop pitch). If you are leaving a lot of turns, you need thicker rubber or lower pitch. If you are running out before landing, you need thinner rubber or higher pitch. These two adjustments are NOT interchangeable. There will be an optimum combination of both. However, for small adjustments to match your particular rubber you can tweak the pitch half a degree or one degree. I suspect you will need something in between your rubber choices, but get the prop pitch at a reasonable place first, say 37 degrees on the FFM at 3.5" radius. Then "read your rubber" after the flights.

My limited experience with this year's J&H is that it needs little to no wing wash. Only add wing wash if the plane consistently rolls into the circle enough to dive at high torque

Coach Chuck

[Schrodinger-Cat-8]

Thanks Coach Chuck for the tips, I understand the terms now.
I'd like to ask, how would you control the rate of ascent/letdown of the plane? I don't think I have the resources to trim the rubber, so I'm assuming matching the pitch to the rubber (I think decreasing pitch angle) solves ascent/letdown because the current plane configuration I have right now is more suitable for high ceiling flights probably upwards of 26' since it's ceiling banging and ascending too quickly. I've tried decreasing the decalage in general to stop the plane from lifting too much, but the time loss (loss ~20-40 seconds from 2:00-2:30) doesn't seem to solve the issue in the most efficient way. I've also experimented using a flaring propeller by modifying the plane to weigh significantly lighter (switched winglets from balsa to FF design), and it achieves times of around 1 minute 30 seconds, which isn't too bad but could be better trimmed. I've noticed on the flaring prop the ascent is good, but the letdown is particularly terrible (I think it was because of the torque since I decided not to dewind, but I felt that dewinding would straight up not give enough power for it unless otherwise). I'm also getting ~300-450 turns remaining after, which I assume could be lowered?

[coachchuckaahs]

You are trying to solve multiple things with one solution.

The climb is set by torque, AFTER you get the plane trimmed. Don't try to reduce climb by reducing decalage! The rest of your flight will suffer.

Dewinding is used to set the launch torque, which has to do with the initial climb. You need to wind to near max torque, and then dewind to launch torque. Dewind and launch torque do not affect letdown!

Your letdown is poor because of a mismatch with your rubber. This is evidenced by both the poor letdown and the number of turns remaining on the motor. If the rubber matched the symmetric prop OK, it likely is not a match for the flaring prop. However, this sounds like a large mismatch, I would go to the next larger rubber motor that you have before reducing prop pitch. You can go too far on reducing pitch. You want to make sure you are at least 1.5 Pitch/Diameter on the prop, up to 2.0, but evidence suggests this year's planes may be better on the lower end of that scale. So on a 9.5" prop, you want the pitch to be minimum 14.25", up to 19".

I think you really need to systematically go through your trim again:

1. Set your CG per the plans
2. Fly at low torque, launching from the shoulder. Increase decalage, primarily with wing incidence, until the plane stalls. The C division plane may "mush" more than stall. Then back off a little bit. This sets your decalage. Don't change it!
3. Adjust your circles size with tail boom offset and/or tail tilt. Many kits don't have enough tailboom offset. If you adjust it, go back to step 2 again.
4. Wind to max torque and then dewind to a safe starting torque, say 0.4 oz-in. Observe the climb. If not enough, dewind to 0.5, then 0.6, etc. until the climb is good.
5. IF, and ONLY IF the plane rolls inward and dives (rolls left), add a little left wing wash in, a few mm at a time. If you do this, go back to step 2 and repeat all steps.
6. Observe winds remaining WHEN YOU ARE CONSISTENTLY REACING THE RAFTERS. IF a lot, go to thicker rubber. If it deadsticks, go to thinner rubber. For small changes you can adjust the prop pitch, lower pitch to climb more or to use up more winds. If you change rubber or pitch, go back to step 4.

Coach Chuck

[jgrischow1]

Coach Chuck,

Very useful info...could you clarify something about pitch you were suggesting to Schrödinger? In your second to last post, you said "I suspect that your are going too low on pitch." and "I suspect you have made a large change to lower pitch to the point the prop blade ("wings" are not lifting (thrust) much at all." and in your last post you said " I would go to the next larger rubber motor that you have before reducing prop pitch"...is this because Schrodinger's winds remaining were more than you had anticipated?

Sorry, just trying to understand the intricacies of changing prop pitch. Thanks!

[coachchuckaahs]

Coach Chuck,

Very useful info...could you clarify something about pitch you were suggesting to Schrödinger? In your second to last post, you said "I suspect that your are going too low on pitch." and "I suspect you have made a large change to lower pitch to the point the prop blade ("wings" are not lifting (thrust) much at all." and in your last post you said " I would go to the next larger rubber motor that you have before reducing prop pitch"...is this because Schrodinger's winds remaining were more than you had anticipated?

Sorry, just trying to understand the intricacies of changing prop pitch. Thanks!

No, decreasing prop pitch would use up more winds, as the prop is easier to turn. However, decreasing it too much, the plane cannot attain much forward speed before the prop generates no lift at all (the angle of attack goes to zero as the speed forward changes the angle the prop is slicing through the air). The student reported going to thinner rubber, and then reducing prop pitch resulting in no climb. Generally students first attempts at changing prop pitch are large, so I suspect the change was larger toward lower pitch. A 2 degree pitch change is significant.

Generally the Ikara props come at the lower end of pitch I suggested, but they do vary. Therefore I recommended going to the thicker rubber and increasing pitch to get a better match. This issue also reminds us that going from 0.094 to 0.087 is a HUGE change in rubber linear density. The apparently need something in between these cut widths. They can match one or the other existing densities by changing prop pitch. They went to thinner rubber and then lower prop pitch. This is the right direction for thinner rubber, but it appears the pitch is too low for the forward airspeed of the plane. So the other choice is to go back to the thicker rubber and increase prop pitch until it does not deadstick. This likely will not be an optimum combination, but is likely to be better than the thin/low combination.

Coach Chuck

[jgrischow1]

Coach Chuck,

Very useful info...could you clarify something about pitch you were suggesting to Schrödinger? In your second to last post, you said "I suspect that your are going too low on pitch." and "I suspect you have made a large change to lower pitch to the point the prop blade ("wings" are not lifting (thrust) much at all." and in your last post you said " I would go to the next larger rubber motor that you have before reducing prop pitch"...is this because Schrodinger's winds remaining were more than you had anticipated?

Sorry, just trying to understand the intricacies of changing prop pitch. Thanks!

No, decreasing prop pitch would use up more winds, as the prop is easier to turn. However, decreasing it too much, the plane cannot attain much forward speed before the prop generates no lift at all (the angle of attack goes to zero as the speed forward changes the angle the prop is slicing through the air). The student reported going to thinner rubber, and then reducing prop pitch resulting in no climb. Generally students first attempts at changing prop pitch are large, so I suspect the change was larger toward lower pitch. A 2 degree pitch change is significant.

Generally the Ikara props come at the lower end of pitch I suggested, but they do vary. Therefore I recommended going to the thicker rubber and increasing pitch to get a better match. This issue also reminds us that going from 0.094 to 0.087 is a HUGE change in rubber linear density. The apparently need something in between these cut widths. They can match one or the other existing densities by changing prop pitch. They went to thinner rubber and then lower prop pitch. This is the right direction for thinner rubber, but it appears the pitch is too low for the forward airspeed of the plane. So the other choice is to go back to the thicker rubber and increase prop pitch until it does not deadstick. This likely will not be an optimum combination, but is likely to be better than the thin/low combination.

Coach Chuck

Got it, thanks!

[jgrischow1]

Coach Chuck,

Very useful info...could you clarify something about pitch you were suggesting to Schrödinger? In your second to last post, you said "I suspect that your are going too low on pitch." and "I suspect you have made a large change to lower pitch to the point the prop blade ("wings" are not lifting (thrust) much at all." and in your last post you said " I would go to the next larger rubber motor that you have before reducing prop pitch"...is this because Schrodinger's winds remaining were more than you had anticipated?

Sorry, just trying to understand the intricacies of changing prop pitch. Thanks!

No, decreasing prop pitch would use up more winds, as the prop is easier to turn. However, decreasing it too much, the plane cannot attain much forward speed before the prop generates no lift at all (the angle of attack goes to zero as the speed forward changes the angle the prop is slicing through the air). The student reported going to thinner rubber, and then reducing prop pitch resulting in no climb. Generally students first attempts at changing prop pitch are large, so I suspect the change was larger toward lower pitch. A 2 degree pitch change is significant.

Generally the Ikara props come at the lower end of pitch I suggested, but they do vary. Therefore I recommended going to the thicker rubber and increasing pitch to get a better match. This issue also reminds us that going from 0.094 to 0.087 is a HUGE change in rubber linear density. The apparently need something in between these cut widths. They can match one or the other existing densities by changing prop pitch. They went to thinner rubber and then lower prop pitch. This is the right direction for thinner rubber, but it appears the pitch is too low for the forward airspeed of the plane. So the other choice is to go back to the thicker rubber and increase prop pitch until it does not deadstick. This likely will not be an optimum combination, but is likely to be better than the thin/low combination.

Coach Chuck

So let me see if I can apply what you've been saying to my kids' plane. It's doing around 2:10 in a 22' gym and seems to fly pretty nicely. Doesn't seem like a lot of trim settings need changed. It lands with a few hundred winds left. They have been using standard Ikara props thus far, maybe 38 deg. pitch angle. Would now be the time to try flaring props, props with a lower pitch, or denser rubber? Thanks!

[coachchuckaahs]

The student has a good flying stable plane at 2:10. The next steps are incremental, and take considerable experimentation.

You did not say if this is B or C. But to be clear, even a plane that looks nice in the air may need further trimming. Getting the nose up a little may help (or hurt). Clearly if you have a few hundred winds left you need to increase rubber density or decrease pitch. These can have similar results in reducing remaining winds, but may not have the same result on the clock. It is truly a two parameter problem.

You do not say if the plane is getting close to the ceiling. You cannot compare flights unless you are getting to the target altitude.

You do not indicate the position of you pitch angle, so that pitch angle does not paint a clear picture.

You do not indicate your winding process, torque, rubber density, etc. Often a significant gain can be found in winding. See Coach Brian's video and winding resources.

Yes, you can try other props, and they may help. But until the basic trim is optimized, it is a rabbit trail.

Each change requires going back to basic trim, rubber prop matching, lunch torque after unwinding. You have to be systematic, and once you match the peak altitude and use up most of the winds, then you can compare the clock.

Without trying props, I would first explore the basic trim and the winding techniques

Coach Chuck

[jgrischow1]

The student has a good flying stable plane at 2:10. The next steps are incremental, and take considerable experimentation.

You did not say if this is B or C. But to be clear, even a plane that looks nice in the air may need further trimming. Getting the nose up a little may help (or hurt). Clearly if you have a few hundred winds left you need to increase rubber density or decrease pitch. These can have similar results in reducing remaining winds, but may not have the same result on the clock. It is truly a two parameter problem.

You do not say if the plane is getting close to the ceiling. You cannot compare flights unless you are getting to the target altitude.

You do not indicate the position of you pitch angle, so that pitch angle does not paint a clear picture.

You do not indicate your winding process, torque, rubber density, etc. Often a significant gain can be found in winding. See Coach Brian's video and winding resources.

Yes, you can try other props, and they may help. But until the basic trim is optimized, it is a rabbit trail.

Each change requires going back to basic trim, rubber prop matching, lunch torque after unwinding. You have to be systematic, and once you match the peak altitude and use up most of the winds, then you can compare the clock.

Without trying props, I would first explore the basic trim and the winding techniques

Coach Chuck

Sorry, should have been more clear.

This is Div B.

Slightly nose up.

Getting very close to ceiling.

We are using the FFM pitch gauge. I think in another post you or coach Brian say the typical distance from prop shaft of that measurement; I don't remember what it is offhand.

They wind to about 90% of max winds then back off to launch torque. Rubber density is in the low .060s typically. We have been using coach Brian's videos and winding resources extensively.

Thanks!