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Author Topic: What makes a plane feel light or heavy in the air?  (Read 1244 times)

Matthew Brown

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What makes a plane feel light or heavy in the air?
« on: February 03, 2018, 02:18:46 PM »
I have two planes, one is a profile Hawker Hurricane from the Brodak kit. It is really old and abused. The controls are rather stiff and want to self center due to stiff hinges. This plane is a hand me down from one of the guys I fly with. It flies beautifully, good line tension all over and is just effortless to fly. It weighs in at 45 oz.
This other plane is a scratch built enlarged profile Nobler that weighs in at 43oz. 2oz lighter and a bit more wing area. This plane has very free controls, much smoother more consistent running engine. LA .46 on this versus an FP 40 on the Hawker.
Everything says this should be the better flyer. Itís not by a long shot! It just plain feels really heavy on the handle. I have to force it through the maneuvers and itís not pretty! I can imagine some of it could be severe nose heavy as Iím not sure exactly where to balance it but between the two planes there is a world of difference. The Hawker could be a bit aft cg as I do have a little trouble coming out of maneuvers cleanly, always a little correction needed on exit. That could just be my inexperience as much as an aft cg.
Can CG have this much affect or are there other factors Iím not considering?
Just a clarification, Iím not talking about line tension here, just the feel of the flight controls at the handle.

Matt


Offline Dave_Trible

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Re: What makes a plane feel light or heavy in the air?
« Reply #1 on: February 03, 2018, 02:50:38 PM »
I would agree with Ty as to it being too noseheavy and if your handle line spacing is too close the feel will be slow.  One way to judge about where the CG should be is to observe the glide when the engine cuts.  With the controls neutral the airplane should have a fairly smooth flat spiral down.  If tail heavy it will slow greatly and either try to climb or start rotation into a stall right away.  If nose heavy the airplane will drop the nose immediately and dive with speed.  Remove weight or add ballast until you get that nice glide.  Then adjust the handle spacing for feel and turn speed.  Be aware that your lead outs should then be adjusted to suit the CG.

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Online RandySmith

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Re: What makes a plane feel light or heavy in the air?
« Reply #2 on: February 03, 2018, 03:42:40 PM »
WEIGHT  is the biggest  reason, second  is  trim.  What type hinges  are in the plane ? 
You should hang it by the lead outs indoors  and step back to see if it is hanging with the nose down about 2 degrees
Where is the balance point at ?
Have you tried to loosen the hinges ?

Randy
« Last Edit: February 03, 2018, 05:41:43 PM by RandySmith »

Offline Dan McEntee

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Re: What makes a plane feel light or heavy in the air?
« Reply #3 on: February 03, 2018, 04:35:14 PM »
  Gaps in the control hinge area will give this feeling also. Try taping the flap and elevator hinge lines.
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Offline Tim Wescott

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Re: What makes a plane feel light or heavy in the air?
« Reply #4 on: February 03, 2018, 04:57:06 PM »
Good advice so far.  Reading your original post I thought "oops -- nose heavy".  It's the first thing I'd try.

Tape the hinges first.  Then get the CG right (per what Dave says).  Then get the handle spacing right.
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Matthew Brown

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Re: What makes a plane feel light or heavy in the air?
« Reply #5 on: February 03, 2018, 06:16:27 PM »
Iíll keep these all in mind next time out to the field.
After reading the replies here, Iím more convinced the Hawker needs a little nose weight. Last time out I kept playing with handle spacing trying to reduce the over correcting but by the time I got rid of that, I wasnít getting sufficient throw to get through a few maneuvers.
Hopefully the weather will give me a chance to get out again soon.

Matt

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Re: What makes a plane feel light or heavy in the air?
« Reply #6 on: February 03, 2018, 07:29:11 PM »
Flap/elevator ratio can play into the heavy feel also.  Just depends upon what your criteria are for the heavy feel. 
Hard to turn?  Slow to turn?  Heavy line tension? Ect.
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
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Matthew Brown

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Re: What makes a plane feel light or heavy in the air?
« Reply #7 on: February 03, 2018, 07:37:16 PM »
Flap/elevator ratio can play into the heavy feel also.  Just depends upon what your criteria are for the heavy feel. 
Hard to turn?  Slow to turn?  Heavy line tension? Ect.

The Noblerish plane feels like itís nearly hanging on only one line during maneuvers. At least thatís the best way I can describe it.

Matt

Offline Dan McEntee

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Re: What makes a plane feel light or heavy in the air?
« Reply #8 on: February 03, 2018, 09:13:50 PM »
The Noblerish plane feels like itís nearly hanging on only one line during maneuvers. At least thatís the best way I can describe it.

Matt

   Pinned to as forum here somewhere is the Paul Walker trimming flow chart that was published with the article for his Impact model several years ago. It will be handy for this situation. When trimming and making changes, do one change at a time. If it doesn't work, put it back. It kind of sounds like you need to move lead outs forward, if you have adjustable lead outs, but excessive nose heavy can do this also. Better check balance first. Just a guess balance point would be just ahead of the high point of the airfoil. If it balances anywhere near the leading edge, add some weight to the tail. A nose heavy condition will make the nose yaw out excessively also, adding to the difficulty in making the model turn.
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Offline Matt Spencer

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Re: What makes a plane feel light or heavy in the air?
« Reply #9 on: February 03, 2018, 09:18:29 PM »
What makes a plane feel light or heavy in the air?

WEIGHT .  R%%%% LL~ S?P just kiddig , maybe .

===============================
being having reading to much , the Galdini olympic artical , Stunt Column in Model Aviation - on Gieske , and Rabe , and OTHERS ,

start with ' worn controls ' saying wont fly right till they get a bit of slack in them ,

THEN ,

Galdini , 5 mm slack at T E elevators Reqd ,

Gieseke , 1/8 to 1/4 slack at T E Elevator ,

Rabe  , ' Dead Zone - thicker stab than elevator .

The Theory , If you move flaps BEFORE Elevator - you get good ' GROOVE ' . The effective incidance changes ( in level flight ) without changeing the A.o.A.
( being angle of attack . nose up/ nose down )

Id found on one plane , after removeing the 5 mm slack at the T.E. of 2 in chord elevators , the thing wove everywhere , loops , wingover , level , Sq 8 legs as this was considerably irritateing , after two weeks I reaccessed the elevator horns and re slacked of them .

The P51 also suffered a few ailments , a 1/8 horn , the cutting in ( again ) and fitting a flattened 3/16 brasss tube , ( two x 3/32 drill shanks fit adjacent )
got 6 mm slack at the T E ( 3 1/4 chord ) and it ' found the groove ' and lost all its trigger happy tendancies .

NONE of these suckers have oversize tailplanes . Bob Hunt is not a fan of the ' dead zone ' theory , but his have the large % Tailplanes
and oft comments on how earlier he flew Fwd. C. G.s , compared to young Bill Werwage . So this qualifies things a bit .

The first of mine I mentioned was my third F4E Phantom , which is a pirate of a Bjornwall Mustunt P 51 B , moments areas , wing , Bulkhead posn .
Measuring C G found it 3/4 aft of his designated posn. o.k. with the slack . not without . Snappy performer , handles wind well , with a bit of ' tecnique ' ,
But Dislikes aggressive inputs , it came in twelve times on a flight after the city traffic and hysteria .
Hair Trigger & Fingertip control , or easing & flying it . Not attacking it with a mallet . Will do the Bi Slob Tricks , richened up

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Thus Therefore and Sofar , 3/16 free play at T E Elevators : GOOD .  any slack bellcrank ( leadouts ) to Flaps : BAD .

a profile should enable you to ascertain this No Sweat .

Some Theorise the pushrod slack at the Flap Horn ( to Elevator ) - Gieseke ; which alows the pushrod mass as a dampner on the floating travel .

Offline Tim Wescott

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Re: What makes a plane feel light or heavy in the air?
« Reply #10 on: February 03, 2018, 11:31:14 PM »
   Pinned to as forum here somewhere is the Paul Walker trimming flow chart ...

I second that.  It's amazing how much better a plane will fly (even a Ringmaster) when you trim it per that chart.
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Online Brett Buck

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Re: What makes a plane feel light or heavy in the air?
« Reply #11 on: February 04, 2018, 12:35:48 AM »
I have two planes, one is a profile Hawker Hurricane from the Brodak kit. It is really old and abused. The controls are rather stiff and want to self center due to stiff hinges. This plane is a hand me down from one of the guys I fly with. It flies beautifully, good line tension all over and is just effortless to fly. It weighs in at 45 oz.
This other plane is a scratch built enlarged profile Nobler that weighs in at 43oz. 2oz lighter and a bit more wing area. This plane has very free controls, much smoother more consistent running engine. LA .46 on this versus an FP 40 on the Hawker.
Everything says this should be the better flyer. Itís not by a long shot! It just plain feels really heavy on the handle.

   This illustrates my (repeated to the point of tedium) point about "designs".  Almost always, trim issues - which this is - swamp the differences in design. In this case the problem is almost certainly that it is nose-heavy. There are ways to determine a ballpark CG by calculation (search for MGC or mean geometric chord) but in this case, since it's a Nobler, start with the CG about 3/4" behind the leading edge at the wingtip.  Then move the CG back about 1/16" at a time, fly it,  and see what happens as you do.

     What I expect is that you will have to move it a lot with not much effect, then, all of a sudden, it will start having a big effect. If you keep going past that, then you might get into trouble, which is why you need to move it in tiny increments. And you will start noticing that there is a big difference between the beginning of the flight and the end, because the CG shift due to fuel running out will start having a lot of effect.  The Nobler, like most classic airplanes, is *very sensitive* to the CG position and once you are in the ballpark, tiny changes make a big difference. This is why modern airplanes have much larger tail area and longer tail moments, to make it less sensitive to CG shifts, and to permit you to run the CG further aft without becoming unstable. If you start to feel it make a big difference, but it's still too sluggish, stop moving the CG and make the handle spacing larger.

    This is not necessarily optimal way to go about it, but at this point, just getting the basics right will make a large difference. Once you have a few dozen flights under your belt with the "improved" system, you might end up needing to reduce the flap travel with respect to the elevator, or something like that. At that point you might want to seek out an expert to assist, because there are many things that make a difference but you might not be able to pick up on, trim flowchart or not - if you can't see the effects, then you don't know what to adjust.

    People try to calculate the wing loading, worry about weight, worry about what airfoil to use, stuff like that, but never get close in terms of trim and frequently jump to incorrect conclusions like the airplane is too heavy or "I should have used a NACA 0021 instead of a NACA 0020", when in fact it's just out of trim.

    Brett

Offline Skip Chernoff

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Re: What makes a plane feel light or heavy in the air?
« Reply #12 on: February 04, 2018, 09:26:08 AM »
I'm no expert,but from my experience if you have a Nobler and it doesn't want to turn it's nose heavy and needs tail weight. With the extra weight of a modern engine up front ,my Noblers needed an ounce of lead attached to the trailing edge of the rudder to get a responsive nice square corner. Also my line spacing is about 4" with very little overhang.

Online Brett Buck

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Re: What makes a plane feel light or heavy in the air?
« Reply #13 on: February 04, 2018, 11:28:35 AM »
I'm no expert,but from my experience if you have a Nobler and it doesn't want to turn it's nose heavy and needs tail weight. With the extra weight of a modern engine up front ,my Noblers needed an ounce of lead attached to the trailing edge of the rudder to get a responsive nice square corner. Also my line spacing is about 4" with very little overhang.

   The kicker with all these sorts of models is that with the tail volume they have, too nose heavy, and they simply don't have enough torque. It's doubly bad for the Nobler clones, because unless the airplane weighs in the mid-40 ounce range or more, and have a vintage engine, the flaps are far too large. Make them lighter, use a good engine, and you can probably cut 3/4 or more off the flaps and improve the performance (or to keep it classic-legal, reduce the flap throw).


     This led to current designs, in several steps. The first step was logical enough, if the tail is not powerful enough, make it bigger. First, it just got larger, later, it also got longer, both to increase the available torque. Then through experimentation with flap size, finding that the flaps were generally too large (although people knew the general problem in the late 50's, it wasn't made completely explicit until the Imitation article).

    At some point, someone, (possibly Paul Walker) figured out that with a bigger and longer tail, you could overcome the forward CG but you could also move the CG backwards safely and maintain stability. Add piped engines, and that was pretty much it, that's what we have been doing since then, and it works to the point that people thought the entire event was rigged.

     In this case, the problem is very simple, start moving the CG aft, watch the other trim factors like the tip weight (since lots of nose weight tends to obscure other flaws  - which is why people did it for years), and be careful as you get close.

   

    Brett

Offline Matt Spencer

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Re: What makes a plane feel light or heavy in the air?
« Reply #14 on: February 04, 2018, 07:05:52 PM »


Last Paragraph .

If your nose heavy , itll obviously be lighter to take a saw to it ( the Nose ) & shift engine back , than to add lead at the other end .
A bit of judicous use of a chisel and suchlike can get a new vertical bearer in in back of the engine .
Obvious thing is back two holes ( Front bolts in existing rear holes , & drill two more , aft .

Also a toungue mufflers not as heavy as a big stock OS one .  S?P

If the tanks a problem , make a short one , or test with a undersize light one & then get a custom Brodak or such , if justified .

Offline Eric Viglione

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Re: What makes a plane feel light or heavy in the air?
« Reply #15 on: February 04, 2018, 09:10:42 PM »
Assuming you have the CG right as Brett described above, for me, handle overhang is a huge contributer to that heavy feel. Front bar handles with the bar adjusted way out away from your knuckles realy amplify that heavy feel... more than some may ever believe could be possible. It makes the plane feel so dead it's not funny.
EricV
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Offline Skip Chernoff

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Re: What makes a plane feel light or heavy in the air?
« Reply #16 on: February 05, 2018, 03:41:00 PM »
Eric I agree with you completely about the "overhang" issue. What is so perplexing to me is this.... In the film that shows all disciplines of control line flight "Wired for Excitement" (I think) you're in the circle with Bob Hunt in his prime. He's flying with a handle that has a tremendous amount of overhang. Was his plane very tail heavy and he needed to slow down the controls? Maybe some of our in house champs can explain this. Thanks,Skip

Offline Dan McEntee

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Re: What makes a plane feel light or heavy in the air?
« Reply #17 on: February 05, 2018, 05:32:09 PM »
Eric I agree with you completely about the "overhang" issue. What is so perplexing to me is this.... In the film that shows all disciplines of control line flight "Wired for Excitement" (I think) you're in the circle with Bob Hunt in his prime. He's flying with a handle that has a tremendous amount of overhang. Was his plane very tail heavy and he needed to slow down the controls? Maybe some of our in house champs can explain this. Thanks,Skip

    The handle Bob is using in that video is one that he had on the market at that time. it had fixed line spacing, but you could adjust the neutral in flight with that little knob. When I was getting started back in the mid to late 80's, the trend in less overhang was starting, and guys would cut off the ends of those handles a little at a time until they got to a point that they liked the feel. I haven't seen one in a long time but I bet there are some in drawers of some of the longer experienced flyers out there.
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Online Brett Buck

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Re: What makes a plane feel light or heavy in the air?
« Reply #18 on: February 05, 2018, 09:46:31 PM »
Eric I agree with you completely about the "overhang" issue. What is so perplexing to me is this.... In the film that shows all disciplines of control line flight "Wired for Excitement" (I think) you're in the circle with Bob Hunt in his prime. He's flying with a handle that has a tremendous amount of overhang. Was his plane very tail heavy and he needed to slow down the controls? Maybe some of our in house champs can explain this. Thanks,Skip

   I would love for Bubba to give his comments - some of which which I have heard before.

     The answer for the overhang is that it doesn't actually prevent you from moving the controls, it just takes a lot of effort. And the spacing of the CSC handle was large (to fit around Bob's hand comfortably).  Apply sufficient muscle and you can do it. This is different for the CG - too far forward CG, and the load required goes up, and at some point, you just don't have enough line tension to move the controls. This is the Netzeband wall.

     Brett

Offline Eric Viglione

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Re: What makes a plane feel light or heavy in the air?
« Reply #19 on: February 06, 2018, 11:58:05 AM »
  <snip>     The answer for the overhang is that it doesn't actually prevent you from moving the controls, it just takes a lot of effort. And the spacing of the CSC handle was large (to fit around Bob's hand comfortably).  Apply sufficient muscle and you can do it. This is different for the CG - too far forward CG, and the load required goes up, and at some point, you just don't have enough line tension to move the controls. This is the Netzeband wall.

     Brett

Totally agree Brett and I get the distinction. But, the double whammy is when say, a beginner/intermediate flyer who still likes the training wheels feel of an intentionally nose heavy airplane combines that with a front bar handle with a lot of overhang is when I find things can get ugly, and then the wind comes up over 10mph and things get disastrous.

Even I am not immune to the effect when flying OPP's... I have a preset level of control burned into muscle memory, not only the amount of deflection and where neutral is, but also the amount of effort for input. Put me on a nose heavy plane with a goofy handle and I might be likely plant it just as quick or quicker than the owner of the plane. Of course you have to FLY every plane and make the mental adjustment, but we tend to develop mental hard stops in our wrist movement of what we use for what we perceive as max input. Making myself give "panic" amounts of movement beyond that mental barrier when flying OPP's takes conscious effort, heh heh.

EricV
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Online Ted Fancher

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Re: What makes a plane feel light or heavy in the air?
« Reply #20 on: February 06, 2018, 06:00:02 PM »
Here's a mental picture about the extreme extent of handle overhang.

Suppose you had a handle with "totally rigid" 66' long overhangs that attached directly to the leadouts of your 65-70 oz Super Stunter flying around you at ~60MPH.  Take a guess at how much torque you'd have to apply at your wrist just to get the ship to exit level flight.  Now guess how much torque you'd have to apply to obtain even a 10' radius corner.  I don't know either but I do know none of us is strong enough to fly a pattern with it.

Control system geometry is a very big deal although the range of adjustability for "feel" is remarkably wide given the number of adjustability factors available to us via the many variables built into even the simplest of control systems combined with the variables of aerodynamic trim which are obtainable with today's state of the art stunt ships.

This thread is a really good primer on the subject.

Offline Curt D Contrata

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Re: What makes a plane feel light or heavy in the air?
« Reply #21 on: February 06, 2018, 07:33:59 PM »
   I would love for Bubba to give his comments - some of which which I have heard before.

     The answer for the overhang is that it doesn't actually prevent you from moving the controls, it just takes a lot of effort. And the spacing of the CSC handle was large (to fit around Bob's hand comfortably).  Apply sufficient muscle and you can do it. This is different for the CG - too far forward CG, and the load required goes up, and at some point, you just don't have enough line tension to move the controls. This is the Netzeband wall.

     Brett

It also had bias built in, hand was not vertical but negative (down) as I remember. I used it for years and did not do well in competition. It was comfortable, but the only cool part was the adjustable neutral in flight. Mine sold quickly at a KOI a few years ago. 

Curt


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