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Aileron stall buffet

Smilin' Jack

Well Known Member
I know it has been adresses before and the general response was roll slower. But has anyone come up with a fix such as a flexible gap seal on the wing in front of the aileron? I was thinking of taping some very thin UHMW tape to the wing and letting it lay against the aileron to see if the airflow over the bottom and top of the aileron could be improved and eliminate the buffet... Like a gap seal
What do you think,
That little tapping feeling only becomes an issue in double rolls perhaps because my airspeed has decreased.
Also thought about vortex generators installed just adhead of the aileron.
Jack
 
It probably is not a problem. I just don't care for the tap tap in the contrail stick that I can feel during the roll.
J
 
Whatever. Do not put on gap seals. The frieze aileron is designed to have this gap. There have been several attempts at gap sealing the aileron with bad results
 
Andy,
Usually I am well below 142 mph and it only happens rolling right. I am taking some measurements and will see if I can find a difference.
Thanks
Jack
 
Whatever. Do not put on gap seals. The frieze aileron is designed to have this gap. There have been several attempts at gap sealing the aileron with bad results

I've never seen RV ailerons taped, but the Pitts S-1S has Frise ailerons, and taping the gap - i.e. laying 3" wide tape on the top of the wing/aileron gap makes a significant improvement in roll rate, aileron feel, and also reduces stick force slightly. I've flown mine both ways and it felt like a different airplane without the ailerons taped. I don't know anything about attempting to gap seal RV ailerons. What were these "bad results"? Just curious. I too, had previously thought the Frise aileron was aided by airflow through the gap, but that seems not necessarily the case.
 
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I've never seen RV ailerons taped, but the Pitts S-1S has Frise ailerons, and taping the gap - i.e. laying 3" wide tape on the top of the wing/aileron gap makes a significant improvement in roll rate, aileron feel, and also reduces stick force slightly. I've flown mine both ways and it felt like a different airplane without the ailerons taped. I don't know anything about attempting to gap seal RV ailerons. What were these "bad results"? Just curious. I too, had previously thought the Frise aileron was aided by airflow through the gap, but that seems not necessarily the case.

I'm having a very slow rate on my RV7A (even compared to my former RV9A) and some buffet when rolling. Even under 140mph. So I will try to tape the gap. Can you provide me with some pictures from your settings or instruction of which tape to use or how to do it (links to the product) - I'm in Brazil not that easy to find good tapes here. Any help will be nice!
 
I'm having a very slow rate on my RV7A (even compared to my former RV9A) and some buffet when rolling. Even under 140mph. So I will try to tape the gap. Can you provide me with some pictures from your settings or instruction of which tape to use or how to do it (links to the product) - I'm in Brazil not that easy to find good tapes here. Any help will be nice!

I recommend you that you do not tape the gap. A frise style aileron is designed to have airflow between the wing and the aileron.

I think you should look at your problem in a different way.....
If there is 9000+ RV's flying.... with good aileron response (without sealing the gap).... wouldn't it be better to figure out what is different about your airplane from all the rest?

I suggest you start with reading the portion of the current Section 5 of the construction manual regarding proper trailing edge shape of control surfaces.
 
I know it has been adresses before and the general response was roll slower. But has anyone come up with a fix such as a flexible gap seal on the wing in front of the aileron? I was thinking of taping some very thin UHMW tape to the wing and letting it lay against the aileron to see if the airflow over the bottom and top of the aileron could be improved and eliminate the buffet... Like a gap seal
What do you think,
That little tapping feeling only becomes an issue in double rolls perhaps because my airspeed has decreased.
Also thought about vortex generators installed just adhead of the aileron.
Jack

I wouldn't really worry about it. It happens with my RV-8 at certain speeds too. The first time it really got my attention (I hadn't read about it before so it was a surprise during phase 1...) after a while you would miss it if it didn't happen.

Oliver
 
I recommend you that you do not tape the gap. A frise style aileron is designed to have airflow between the wing and the aileron.

I think you should look at your problem in a different way.....
If there is 9000+ RV's flying.... with good aileron response (without sealing the gap).... wouldn't it be better to figure out what is different about your airplane from all the rest?

I suggest you start with reading the portion of the current Section 5 of the construction manual regarding proper trailing edge shape of control surfaces.


Nice Scott! Many thanks as I did not built my plane I did not know about that. I'm going to look into it. Thanks again for the info
 
Define "very slow". How many deg/sec at various IAS?

I wouldn't know how to measure it RV7A Flyer could you tell me?

I'm saying slow as compared with my former 9A who should roll slower than this new 7A but not...

I'm also saying it by a educated guess comparing two flown 7A I've got arround my base.

But It would help a lot if I coud measure... never thought of it. What would you say is the best method? To roll 360 and time it? Just as simple?
 
Well I timed some videos doing tunneaus I had and ones I found and came up with the results:

Average roll for RV7 is 109 to 95 degrees/sec

Mine is doing 85 to 75 degrees/sec (very low as I had supposed)

My 9A (from timing its videos) did about 70 to 65 degrees/sec

Question how do I improve my RV7 roll rate? Clearly it was not feeling right now with some numbers it must not be right and needed to be fixed.

Any comments?
 
1) Is your airplane rigged correctly? In other words, do your ailerons reach the specified deflections?

2) Do cushions or maybe your thighs block full stick travel?

3) What is your technique for rolling the airplane? Walk us through all of your control inputs.

4) Is your airplane stock? No outboard fuel tanks, no luggage storage in the tips, etc?
 
1) Is your airplane rigged correctly? In other words, do your ailerons reach the specified deflections?

2) Do cushions or maybe your thighs block full stick travel?

3) What is your technique for rolling the airplane? Walk us through all of your control inputs.

4) Is your airplane stock? No outboard fuel tanks, no luggage storage in the tips, etc?


1) Don't know I did not build it myself (wish I did). Bought it. Can you provide info on that for me to verify if it reaches specified deflections? Appreciate.

2) No.

3) Not much of a technique , most of the rolls I start at about 120 mph pitch the nose about 25 degrees over the horizon and apply full aileron (no rudder input at all). Most of time. This is my most common roll. Just use rudder in slow rolls. Should try it on normal ones?

4) Stock RV7A no mods. Brand new 143 hours , rolling solo with about 13 gals each tank (balanced and light). First flight October/2015
 
1) Don't know I did not build it myself (wish I did). Bought it. Can you provide info on that for me to verify if it reaches specified deflections? Appreciate.

2) No.

3) Not much of a technique , most of the rolls I start at about 120 mph pitch the nose about 25 degrees over the horizon and apply full aileron (no rudder input at all). Most of time. This is my most common roll. Just use rudder in slow rolls. Should try it on normal ones?

4) Stock RV7A no mods. Brand new 143 hours , rolling solo with about 13 gals each tank (balanced and light). First flight October/2015

Regarding item 1: Do you have access to the instructions or construction manual for your RV-7? It should specify control deflections. I'm an RV-6 guy, so I don't have the data for the -7.

Regarding item 3: I believe your roll rate would increase up to about 150 mph and rudder input would increase the rate as well. Others may have data supporting my belief (particularly regarding roll rate vs airspeed).
 
The IAC tech tips published a method of sealing Pitts ailerons and I liked it on my S1S.

My RV-6 has aileron throws in spec, slightly under in aileron, and they will give some thumping above 1 g near vA, less if unloaded a bit.

I would not seal them. The gap and amount of leading edge in the high pressure below the wing is not the same as the S1S. I bet a few VGs in the right spot would remove the buffet. Do all series of wingtips act the same?


Just a gut feeling. Plus, a 4 aileron Pitts may act differently if a gap seal becomes loose compared to an RV.
 
Rudder definitely assists roll rate in a -4; no reason to think it would be any different in the other short wing models.

Is the roll rate really that slow in a -7? I figured it would be just a bit slower, but not that much.
 
I bet a few VGs in the right spot would remove the buffet. Do all series of wingtips act the same?

The buffeting has been attributed to the nose on the "up" aileron sticking down below the bottom surface of the wing and tripping the airflow as it passes under the aileron. 20 years ago (or thereabouts) Van tried VG's on the leading edge of the ailerons to address this issue. I never saw the results from that trial.

Personally, I might try the VG tape the sailplane guys use. Properly positioned on the LE of the aileron, it might keep the airflow attached and prevent the buffeting. Or it might not. ;-)
 
If memory serves, when I 1st experienced it over 20 years ago in my 1st -4, I called Van's and they told me it was aileron *stall*. Empirical evidence supports this; higher airspeeds reduce the bumping.
 
VGs probably won't help

I tried VGs on my RV-8 on the outboard wing leading edge i.e. in front of the ailerons. They made no difference to the stick buffeting that you are talking about or the roll rate under any configuration.
Cheers
Nige
 
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