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Baffling heavy wing issues

flyenforfun

Well Known Member
Perplexing heavy left wing problems.
I finished my -8 back in 2012 and on the initial flights we had a heavy the left-wing. We tried everything that vans told us to do and more ideas from vans Air Force forum. Nothing seems to work except re-drilling and lowering the left aileron out board hinge however that caused us to have a heavy right wing but with almost full left aileron trim it flew straight and level so I've lived with that band-Aid fix for about five years. Now I have decided to revisit the problem and try to fix it properly. This weekend I raised the left hinge 1/16 of an inch hoping that I would be able to trim the plane closer to neutral position. So what's happening now is with the trim in neutral position the faster I go the more the plane wants to roll to the left and the slower I go the more it wants the rollback to the right The strange thing is that if you hold the stick in level flight both Ailerons are in line with the wingtips and flaps which makes me think that there is some kind of airflow issue going on that I can't see. I've tried all of the standard fixes like rigging, squeezing trailing edges, trim tabs and even built a brand new right the Aileron i've had various results but no eureka moments. I feel like I'm missing something and not looking at the right thing. Any ideas? I would love to find the smoking gun. I believe everything is set right i.e. Rigging, wing incidence, wheel pants and fairings. Somehow somewhere I am inducing drag and the drag increases as speed increases and vice a versa. Maybe someone on this forum can think outside the box and give me an idea of where else to look.
Thanks.
 
If it fly's straight when the ailerons are held aligned it is an indicator that asymmetrical aerodynamic influences on the ailerons are forcing them to displace which then makes the airplane roll.
You may be chasing the displacement influence back and forth by making small changes.
Have you done actual measurement checks of the aileron flatness, and their position relative to the wing?
The current Rev. Section 5 of the construction manual has details regarding checking for proper aileron shape.
 
When you change speed, are you holding the stick so it can't move?

There are 2 things that the ailerons produce - a force vector and a hinge moment. The force vector is simply the lift on the aileron, which rolls the airplane. The hinge moment is the twisting force about the hinge line, which gets turned into a push or pull force on your aileron push rod that comes into the torque tube on which the stick is mounted. If the left and right hinge moments are well balanced then all is good. If you have something odd, like the aileron is high, or warped, or the trailing edge is poorly formed on one aileron and not the other, then the ailerons will float to some non zero deflection in order to balance the forces on each pushrod. This will change the roll trim and drive you nuts.

So, do you have an asymmetry on the aileron lift? Or do you have an asymmetry on the hinge moment? Or do you have a twisting wing or wing tip?

You can see that it can be a really difficult thing to pin down. If you want to eliminate the hinge moment, when you test hold the stick to prevent it from deflecting laterally, so even if there is asymmetric force from the aileron push rods it won't affect the aileron position. Also, any testing you do has to have the ball absolutely centered, or it is meaningless. Sideslip generates roll.

YOu say you believe that the wing twist and incidence are good - how did you measure it? Just because the ailerons align with the tips and the flaps is not telling you much - the flaps and tips can be off, by a mile. You need to make accurate templates that will sit on the wing by themselves with out falling over, level the airplane and put those templates along the wing in various places with a very accurate inclinometer and check the wing incidence at various spanwise locations. The templates should also tell you if your flaps and ailerons are aligned with the wing profile both at their inboard and outboard ends. There is something off somewhere that your current measurement methods have not identified. Assume nothing, believe nothing until you have measured it. Are the ailerons or flap TEs bowed?

After that, start looking at any difference in the aileron cove - the space between the rear spar and the aileron that has that bent piece of sheet that fills in the space. Same with the flap. Something has to be off somewhere, but you have not been picky enough to find it. My bet is that if you search long and hard enough, you will find it on the ground.

A final thought, though it is a long shot - do you have a massive lateral imbalance in the airplane? A horrendously heavy landing light on one side? That would give you a roll trim requirement that would change with speed. Just a thought - hard to image that you have something like that. But I wouldn't take anything for granted.
 
Rudder trim

Are you sure the plane is flying straight? With the main section of each wing at the same angle of attack?
 
As we all know an increase in speed will change an aircrafts balanced trim position and require retrimming. Eliminating aileron control position by having them both streamlined, fuel tanks equal quantity, ensuring wing tips are both accurately placed and the fin/rudder are aligned correctly I would be looking closely at the empennage specifically the tailplane and each elevator, this area is often overlooked if a plane wants to roll when speed is increased.
Keep researching -:)
 
Set the controls to neutral, take a digital level and measure left and right control surfaces, flaps, ailerons and elevators every 6 inches along their span.

This will identify any left/right imbalance and any control surface twist.
 
Check wing skin aft of rear spar

I'm not sure if this will help you .... but I'll throw it out there for you to consider. My RV-12 had a slightly heavy left wing which was solved by tweaking the wing skin aft of the rear spar. A straight edge placed parallel to the ribs was used to insure the metal aft of the rear spar was in alignment with the wing skin.

On my RV-12, some areas aft of the rear wing spar were a little low and others were a little high on both wings ... after using a small block of wood to bring the metal into alignment with the wing skin forward of the rear spar, the heavy left wing was gone.

Happy flying,
 
I have the same issue

My airplane started out with a heavy right wing, with the forces increasing the faster I went. I squeezed the left aileron, and it helped but didn't fully solve the problem. In normal cruise, which for me is 8 gph and about 174 KTAS, I have a nice neutral stick. In the pattern, at slow speed, my plane rolls left, but forces are low, so no real issue. The problem is that when I race, the right roll becomes very pronounced and takes a lot of stick force, especially at the end of the race when you are diving for the finish.

I talked to Burt Rutan about it, since he has taken up residence at my home airport. He said, "If it bugs you, put a trim tab on it." Not really the answer I was looking for. For the last several years, I have taped a trim tab on using 230 mph tape, and it works for racing, but I don't really consider this a satisfactory answer.

I have measured my wings several times, and they appear to be straight. I know that my rudder has a trim tab, that is great for cruise, but I also have to use some rudder pressure to keep the ball centered when going fast. I have thought about repositioning the rudder to center the ball at high speed to see what that would do, but I can't see it really solving the roll problem.

I have been thinking about modifying the aileron location up or down, probably down, on the right side thus helping the aileron deflect down, with a higher lift component.

I do agree with a previous post that the issue has to be related to wing, tip, or aileron geometry. For me, I have changed the tips when I race, and no appreciable change, so I think I have eliminated that. I have done the template thing with my wings, and am not able to identify anything. I have not closely looked at the slot between the ailerons and wing, so I will do that.

Very interesting thread, I will keep watching.
 
Gear Leg Fairings

I thought of that, but since they don't move at all I figured it couldn't be them. When fast it rolls right, slow it rolls left. I think it has to be airflow around the ailerons...
 
huh?

I thought of that, but since they don't move at all I figured it couldn't be them. When fast it rolls right, slow it rolls left. I think it has to be airflow around the ailerons...

This suggested to me the current fix may not be the correct one. Maybe an issue was compensated for and not corrected, hence the "fix" only balances out that tendency at one airspeed? JMHO
 
Elevators?

Are the elevators in alignment? I once had a yaw problem on my float plane ( I know not related) turned out that when retracted the water rudders were out of alignment. Elevators could cause a roll tendency of properly aligned.
 
My RV-8 had a heavy left wing when I bought it in 2013. I followed a suggestion I think I read on this forum, and it immediately fixed the problem. The suggestion was: Cut a small coffee-stirring straw in half and tape it to the bottom aft end of the opposite aileron, parallel to and about 1/4 inch forward of the trailing edge. Use clear packing tape to secure the straw. I secured the straw roughly in the middle of the aft aileron span. The straw and tape have remained in place for 4.5 years. This sounds too easy to be true, but I'm not joking -- it did the job.
 
good tip

My RV-8 had a heavy left wing when I bought it in 2013. I followed a suggestion I think I read on this forum, and it immediately fixed the problem. The suggestion was: Cut a small coffee-stirring straw in half and tape it to the bottom aft end of the opposite aileron, parallel to and about 1/4 inch forward of the trailing edge. Use clear packing tape to secure the straw. I secured the straw roughly in the middle of the aft aileron span. The straw and tape have remained in place for 4.5 years. This sounds too easy to be true, but I'm not joking -- it did the job.
Gonna file this one away for the future. Another example showing aerodynamics is complex.
 
Elevators

When I was aligning my elevators, I used an 8' alum. straight edge on the trailing edge. I discovered that elevator horns (where the counter weights are mounted) did not align with the horizontal stabilizer. If one side was flush, the other was off by 3/16". I had a choice, either a straight trailing edge or misalignment with the counter balance arms meeting the HS. Vans, told me this was a common problem. I chose the straight trailing edge. A friend did the opposite aligning the horns, he now has a heavy wing. Just a thought, check out your elevator trailing edges with a straight edge.
 
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FWIW - Solved heavy left wing by slightly squeezing right wing aileron bend full length.

Then had heavy right wing!!

Squeezed left wing aileron slightly at one panel between ribs, airplane now flies wings level by itself.
 
My RV-8 had a heavy left wing when I bought it in 2013. I followed a suggestion I think I read on this forum, and it immediately fixed the problem. The suggestion was: Cut a small coffee-stirring straw in half and tape it to the bottom aft end of the opposite aileron, parallel to and about 1/4 inch forward of the trailing edge. Use clear packing tape to secure the straw. I secured the straw roughly in the middle of the aft aileron span. The straw and tape have remained in place for 4.5 years. This sounds too easy to be true, but I'm not joking -- it did the job.

In other words, a Gurney flap?

https://en.wikipedia.org/wiki/Gurney_flap
 
The of the different advice and ideas is great, but a lot of it misses the mark.

If there is a problem related to the ailerons (likely since the OP said if he manually holds the ailerons in neutral, the airplane fly's straight), then using a lot of different methods to counter the roll, but totally bypassing fixing the actual problem is not the sensible way to fix it.

BTW, split alignment on elevators has very little (if any) noticeable influence on roll trim. You need to think about the leverage available... The elevators are very short in span compared to the wings. Any roll they can induce has a very small moment. That is why adjusting the flaps has only a very small effect on roll trim.
The ailerons though have a large moment way out at the end of the wing. That is why a very small aileron abnormality have a large influence on roll trim.

Just squeezing the trailing edge is not totally the correct way to solve a roll trim problem. You could do that and get the trim adjusted, but still have two ailerons that are equally not the correct shape.

As I mentioned previously, the very first thing that should be checked is that the ailerons themselves are actually built to the correctly (primarily trailing edge shape).
 
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Probably too simple but .....

Might not be your problem but I know about this because it happened to me! Full confession, from 20 feet away, it looked perfectly straight and the aileron to inside tip fit was perfect. I never stretched a line until after I had final drilled the tip. :( Fortunately, we noticed it before it was too late.

nikon_20100626_2082-69495790.jpg


After finding the issue, we also found we could not just shift the tip and redrill so we had to split the tip across the back and then reglass it. Pretty easy fix actually, maybe an hour to do and then let it set.

Now having seen that, I look for it in other airplanes and you would be surprised to see how many are really not straight although the inside part of the tip is perfectly aligned. It's easy for the outside tip edge to be low. Can't quantify the impact but it can't be good.

They always told me to fix glass first and then bend metal. Just saying it is something that can be easily overlooked because it is almost too obvious. I didn't notice anyone suggesting that you check it but I thought I would throw it out there just to be sure.

Bill
 
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Might not be your problem but I know about this because it happened to me! Full confession, from 20 feet away, it looked perfectly straight and the aileron to inside tip fit was perfect. I never stretched a line until after I had final drilled the tip. :( Fortunately, we noticed it before it was too late.

nikon_20100626_2082-69495790.jpg


After finding the issue, we also found we could not just shift the tip and redrill so we had to split the tip across the back and then reglass it. Pretty easy fix actually, maybe an hour to do and then let it set.

Now having seen that, I look for it in other airplanes and you would be surprised to see how many are really not straight although the inside part of the tip is perfectly aligned. It's easy for the outside tip edge to be low. Can't quantify the impact but it can't be good.

They always told me to fix glass first and then bend metal. Just saying it is something that can be easily overlooked because it is almost too obvious. I didn't notice anyone suggesting that you check it but I thought I would throw it out there just to be sure.

Bill

That's a good photo of a misaligned tip. I did mention tip placement in an early post.
 
Thanks Scott for your information I had advice . All of the rigging and incidents checks and so forth and so on for Done during the building process five years ago and it was done as per Van's instructions. I don't remember all the specific details but at the time everything checked out. I have been playing with different hinge configurations i.e. raising and lowering the hinge of both Ailerons I also have tried trim tabs on the Ailerons and rudder and we have gotten different results but I can tell so far we have not found the culprit . The airplane always slowly rolls to the left as the speed increases requiring right trim and slowing down the airplane it starts rolling to the right requiring less right trim. The ailerons can be held neutral and the plane will fly true throughout the speed range however you can't let go of the stick and less you trim the airplane. In other words some force is deflecting one of those ailerons either up or down. I'm wondering if it has something to do with the counterweights I never weighed them when I installed them so I do not know if one is heavier than the other and if it was would it make a difference .
 
The ball is a little to the right and cruise flight I put a trim tab on the righside of the rudder and it centered the ball but I still have the roll problem
 
Might not be your problem but I know about this because it happened to me! Full confession, from 20 feet away, it looked perfectly straight and the aileron to inside tip fit was perfect. I never stretched a line until after I had final drilled the tip. :( Fortunately, we noticed it before it was too late.

nikon_20100626_2082-69495790.jpg


After finding the issue, we also found we could not just shift the tip and redrill so we had to split the tip across the back and then reglass it. Pretty easy fix actually, maybe an hour to do and then let it set.

Now having seen that, I look for it in other airplanes and you would be surprised to see how many are really not straight although the inside part of the tip is perfectly aligned. It's easy for the outside tip edge to be low. Can't quantify the impact but it can't be good.

They always told me to fix glass first and then bend metal. Just saying it is something that can be easily overlooked because it is almost too obvious. I didn't notice anyone suggesting that you check it but I thought I would throw it out there just to be sure.

Bill
Thanks Bill but I think we check that five years ago but I will look at it again thanks for the information
 
My RV-8 had a heavy left wing when I bought it in 2013. I followed a suggestion I think I read on this forum, and it immediately fixed the problem. The suggestion was: Cut a small coffee-stirring straw in half and tape it to the bottom aft end of the opposite aileron, parallel to and about 1/4 inch forward of the trailing edge. Use clear packing tape to secure the straw. I secured the straw roughly in the middle of the aft aileron span. The straw and tape have remained in place for 4.5 years. This sounds too easy to be true, but I'm not joking -- it did the job.
That's interesting maybe the straw is acting like A trim tab . What aileron did you put it on again? The light one?
 
The of the different advice and ideas is great, but a lot of it misses the mark.

If there is a problem related to the ailerons (likely since the OP said if he manually holds the ailerons in neutral, the airplane fly's straight), then using a lot of different methods to counter the roll, but totally bypassing fixing the actual problem is not the sensible way to fix it.

BTW, split alignment on elevators has very little (if any) noticeable influence on roll trim. You need to think about the leverage available... The elevators are very short in span compared to the wings. Any roll they can induce has a very small moment. That is why adjusting the flaps has only a very small effect on roll trim.
The ailerons though have a large moment way out at the end of the wing. That is why a very small aileron abnormality have a large influence on roll trim.

Just squeezing the trailing edge is not totally the correct way to solve a roll trim problem. You could do that and get the trim adjusted, but still have two ailerons that are equally not the correct shape.

As I mentioned previously, the very first thing that should be checked is that the ailerons themselves are actually built to the correctly (primarily trailing edge shape).
Thanks Scott for your information I had advice . All of the rigging and incidents checks and so forth and so on for Done during the building process five years ago and it was done as per Van's instructions. I don't remember all the specific details but at the time everything checked out. I have been playing with different hinge configurations i.e. raising and lowering the hinge of both Ailerons I also have tried trim tabs on the Ailerons and rudder and we have gotten different results but I can tell so far we have not found the culprit . The airplane always slowly rolls to the left as the speed increases requiring right trim and slowing down the airplane it starts rolling to the right requiring less right trim. The ailerons can be held neutral and the plane will fly true throughout the speed range however you can't let go of the stick and less you trim the airplane. In other words some force is deflecting one of those ailerons either up or down. I'm wondering if it has something to do with the counterweights I never weighed them when I installed them so I do not know if one is heavier than the other and if it was would it make a difference .
 
Here is an idea that I just had. The Pitot tube is a dynon avionics Pitot tube it is much larger than the one you build from Van's drawings also it is mount it further outboard then the stock tube. Is it possible that it's causing parasites drag or disrupting the airflow under the left aileron?? Any thoughts on that?
 
Matt, have tried very gentle squeeze of right aileron?
Yes. I've tried everything checked everything tested everything your has to be something I'm missing. From the looks of this forum no one has found the smoking gun to this phenomenon just Band-Aids and patches.
 
I used wide jaw vice grip with duct tape over jaws, try gentle squeeze between outboard 2 ribs first.

FWIW, aileron trailing edge was per the plan, now just tiny bit tighter.
 
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Perplexing heavy left wing problems.
I finished my -8 back in 2012 and on the initial flights we had a heavy the left-wing. We tried everything that vans told us to do and more ideas from vans Air Force forum. Nothing seems to work except re-drilling and lowering the left aileron out board hinge however that caused us to have a heavy right wing but with almost full left aileron trim it flew straight and level so I've lived with that band-Aid fix for about five years. Now I have decided to revisit the problem and try to fix it properly. This weekend I raised the left hinge 1/16 of an inch hoping that I would be able to trim the plane closer to neutral position. So what's happening now is with the trim in neutral position the faster I go the more the plane wants to roll to the left and the slower I go the more it wants the rollback to the right The strange thing is that if you hold the stick in level flight both Ailerons are in line with the wingtips and flaps which makes me think that there is some kind of airflow issue going on that I can't see. I've tried all of the standard fixes like rigging, squeezing trailing edges, trim tabs and even built a brand new right the Aileron i've had various results but no eureka moments. I feel like I'm missing something and not looking at the right thing. Any ideas? I would love to find the smoking gun. I believe everything is set right i.e. Rigging, wing incidence, wheel pants and fairings. Somehow somewhere I am inducing drag and the drag increases as speed increases and vice a versa. Maybe someone on this forum can think outside the box and give me an idea of where else to look.
Thanks.
I have an update to my heavy wings story . I took the trim springs out then flew the plane and I found that as I'm picking up speed the right wing is heavy and is soon as I had 120 kn it shifts to the left wing being heavy. I would like to truly solve this mystery.
 
I have an update to my heavy wings story . I took the trim springs out then flew the plane and I found that as I'm picking up speed the right wing is heavy and is soon as I had 120 kn it shifts to the left wing being heavy. I would like to truly solve this mystery.

Matt, as little as 3 gallons of fuel will affect wings level in calm air, ball centered. I proved it starting with full tanks.
 
My two cents. If that Dynon pitot is larger than the normal pitot and is installed ahead of an aileron I believe that Would create a problem with air flow over/under the aileron. And it's interaction would change with speed.
 
Matt,
It's not the aileron.
Your left flap is low.
Induced drag at high speed.

Level plane and measure full length of
Flap from out to in on right and then do the left.

After that rerig ailerons


Hopes its the smoker you are looking for.

Boomer
 
Solved!!!

To recap, I had a situation that the airplane rolls left at low speed, and rolls more and more right the faster I go until I am unable to trim it to hands off. Stick force in roll becomes quite high when diving for the finish at races. Uncomfortably high. See my previous post in this thread for more explanation of my trim issue.

I had decided to start experimenting with aileron height relative to the wing to see if I could solve the problem this way. The way I figured it was that the left aileron was rigged too high, causing high velocity air on top to create a low pressure area on top, causing the aileron to float up at high speed and therefore a right roll.

I know a picture is worth a thousand words, but I don't have one so I will try to describe what I did: I took a 24 inch ruler and laid it on the top wing skin along the wing rivet lines and also just inside the outboard top rivets on the aileron spar. To ensure consistent measurements, I set the ruler in the same place relative to the back of the wing skin every time. Also, I held the ruler in place by putting pressure right on the 12 inch mark of the ruler.

What I discovered surprised me; the ailerons were rigged the same. However, the wing skin was bent down aft of the rear spar on the right wing above the aileron by as much as 3/16 in. The skin on the left did not have this problem.

So... I gently straightened the skin out on the right, and went flying. Problem solved! It is not perfect, but my spring trim will allow the plane to fly hands off almost the entire speed range of the airplane. Amazing. I have fought this for years, and it took literally 5 minutes to fix once I saw the problem.

I hope this helps someone.
 
...

I know a picture is worth a thousand words, but I don't have one so I will try to describe what I did: I took a 24 inch ruler and laid it on the top wing skin along the wing rivet lines and also just inside the outboard top rivets on the aileron spar. To ensure consistent measurements, I set the ruler in the same place relative to the back of the wing skin every time. Also, I held the ruler in place by putting pressure right on the 12 inch mark of the ruler.

What I discovered surprised me; the ailerons were rigged the same. However, the wing skin was bent down aft of the rear spar on the right wing above the aileron by as much as 3/16 in. The skin on the left did not have this problem.

So... I gently straightened the skin out on the right, and went flying. Problem solved! It is not perfect, but my spring trim will allow the plane to fly hands off almost the entire speed range of the airplane. Amazing. I have fought this for years, and it took literally 5 minutes to fix once I saw the problem.

I hope this helps someone.

Taking two flexible metal yardsticks and holding them on the top and bottom surfaces of the wing at various flap and aileron locations can show where control surface misalignment and the famous "ski jump" conditions exist.

Just think of the flexible, but still somewhat stiff, yardstick tracking the airflow over the wing.

This was one of the methods used by early -6 builders to get flap and aileron alignment and a neutral position. :)
 
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