Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

General Electric Discussions Talk about topics related to e-powered RC flying

Thank you for your support (hide ads)
Reply
 
Thread Tools Display Modes
Old 08-29-2007, 02:47 AM   #1
Ribcracker
Flight Junkie
 
Ribcracker's Avatar
 
Join Date: Aug 2005
Location: Oxford, MI
Posts: 1,087
Thanked 40 Times in 39 Posts
iTrader: (0)
Friends: (2)
Unhappy Aileron Flutter!

I bought a Chinese Jumping Jack clone (Desert-EP) that quickly became my favorite until the wings folded in a steep dive. I immediately bought another. The only thing I did different in the build (besides re-enforcing the wings) was to use Du-Bro pinned nylon hinges instead of the ca type. The hinge gap was a little over a sixteenth of an inch to accommodate the hinge barrels which is a wider gap than I would ordinarily use. I got aileron flutter on the maiden so I made some linkage adjustments and went back up. The flutter was so bad that the aileron actually flew off. I pulled out and re-glued the hinges but with epoxy this time. Again aileron flutter! So I put new control horns on with undersized pushrod holes to remove all slop. Aileron flutter! So I used Blenderm to seal the gaps and add stability. Aileron flutter! There were broken teeth in the servo gears so I replaced them. Aileron flutter! And then more broken teeth!
I had no such problems with the first plane nor any of my many other planes. I swear I'm at my wits' end and don't know what to do. I guess my next step is to tear out the nylon hinges or cut them off flush, cut new slots, install ca hinges and hope for the best.
Wattflyer is rich with many, many wise people. I appeal to you folks for ideas on how to beat this demon. You're my last hope.

It's easy to be wise. Just think of something stupid to say and then don't say it.
Ribcracker is offline  
  Reply With Quote
Old 08-29-2007, 03:30 AM   #2
Sir Raleigh
Super Contributor
 
Join Date: Apr 2007
Location: Raleigh, NC
Posts: 1,557
Thanked 95 Times in 90 Posts
iTrader: (0)
Friends: (3)
Default

Is one surface of the aileron flush with the wing, on the bottom, perhaps?

If it's like my Wing Dragon 4, they used one continuous strip of tape all the way across the length of the aileron to eliminate the gap.
Sir Raleigh is offline  
  Reply With Quote
Old 08-29-2007, 04:50 AM   #3
batman
Member
 
batman's Avatar
 
Join Date: Jul 2005
Posts: 238
Thanked 5 Times in 5 Posts
iTrader: (0)
Friends: (0)
Default

The best way to fix aileron flutter is to put in more hinges, that closes the distance between each hinge and stops the aileron from flexing. There may be another way to stop flutter but the only way to properly fix it is to close the distance between hinges. You may only need one per side but space them equally.

I hope that's soft water......
Meddle thee not in the affairs of dragons, for thou art crunchy and wouldst be tasty with ketchup.
batman is offline  
  Reply With Quote
Old 08-29-2007, 06:15 PM   #4
Elfwreck
PHD in Crashology
 
Elfwreck's Avatar
 
Join Date: Sep 2005
Location: Oakland Ca.
Posts: 1,143
Thanked 47 Times in 46 Posts
iTrader: (0)
Friends: (1)
Default

Hey now,
Let's see, you tried sealing the gap, no help. Replaced the servo gears, redid the hinges, tightened up the controls, still no help.
Bummer. Have you tried slowing down a bit? Or maybe the aileron edges got rounded somehow? Check and see if the aileron edgge is round or square, square works better on airbatic models, less flutter.
Um, also if you don't inset the pinned hinges they are just flexable enough to cause trouble. I'd try going back to tyvek hinges and use a lot of them, then seal whatever gap is there as well..

I just went through this same thing with a racer, finaly ripped it apart and built in a live hinge, now it's fine. Good luck.
RobII
Elfwreck is offline  
  Reply With Quote
Old 08-30-2007, 01:56 AM   #5
pd1
Still Learning
 
pd1's Avatar
 
Join Date: Sep 2006
Location: North of Boston
Posts: 4,098
View pd1's Gallery69
Thanked 588 Times in 550 Posts
Club: Cape Ann RC Model Club
Awards Showcase

Globetrotter Pilot  WAA-08 Pilot  Outstanding Contributor Award 
iTrader: (6)
Friends: (53)
Default

Ribcracker, Could you post pictures of your installation.

I use the DuBro pinned hinges on almost all of my planes and have not had flutter due to hinges.

Things that can contribute to flutter:

1. Control horn on surface too short.
Shorter horn increases mechanical advantage of servo and decreases
mechanical advantage of surface.

2. Surface can move up and down in area of control horn.
If the surface can wiggle in this area the horn has little effect.
You can hinge the surface immediately next to the horn to stop
movement.

3. Control linkage slop.
You've already addressed this.

4. Servo gears.
Worn or stripped gears can cause flutter, again you've already
addressed this.

5. Loose pivots on torque rod tubes.
The pushrods can move, even if the control surface is held.

6. I forgot, very flexable control surfaces will flutter.

A picture would help us see what might be wrong.

Paul
pd1 is offline  
  Reply With Quote
Old 08-30-2007, 02:11 AM   #6
skiman762
FFFC
 
skiman762's Avatar
 
Join Date: Feb 2006
Location: North Carolina
Posts: 1,008
Thanked 3 Times in 3 Posts
iTrader: (0)
Friends: (2)
Default

It's a balance problem more the likely some models need to have the controls counter balanced you see it alot on the bigger planes

''To those who defend it freedom has a ring the protected can not hear''
Thank You Uncle Henry 4-April-1945
skiman762 is offline  
  Reply With Quote
Old 08-30-2007, 03:28 AM   #7
Ribcracker
Flight Junkie
 
Ribcracker's Avatar
 
Join Date: Aug 2005
Location: Oxford, MI
Posts: 1,087
Thanked 40 Times in 39 Posts
iTrader: (0)
Friends: (2)
Red face Some photos

Raleigh- everything looks flush to me...I think.
batman-I'm using four hinges on each side in slots that were pre-cut by the factory but what you say makes sense. I'll add more hinges when I re-do these.
RobII-Speed is an issue but you have to slow to a gentle cruising speed to get it to stop. I even had flutter on take-off before the plane even left the ground!
The wing is rounded but the aileron is square. Now, the hinge barrels are not inset...you can see them in the gap. And...if you take one of those hinges between your fingers and twist, you'll see a lot of flex in the nylon. This may be an issue.
Paul-Thank you for the well reasoned "trouble-shoot". 1. I have the rod through the middle hole on the kit-included horn. 2. A very good point but these slots are identical to the slots on the first plane which flew beautifully. 5. No push-rod tubes are used. Servos are exposed under the wings with direct linkage. 6. This control surface does seem very flexible. And again, the difference between the two planes was/is the hinges.
skiman-I hadn't thought of balance issues but I've had many squirrelly unbalanced maidens with no flutter. Nonetheless, there could well be balance issues.


Attached Thumbnails
Click image for larger version

Name:	Image00001.jpg
Views:	270
Size:	98.9 KB
ID:	39338   Click image for larger version

Name:	P1010021.JPG
Views:	335
Size:	68.3 KB
ID:	39339   Click image for larger version

Name:	P1010022.JPG
Views:	339
Size:	61.1 KB
ID:	39340   Click image for larger version

Name:	P1010023.JPG
Views:	326
Size:	63.1 KB
ID:	39341   Click image for larger version

Name:	P1010024.JPG
Views:	329
Size:	72.8 KB
ID:	39342  


It's easy to be wise. Just think of something stupid to say and then don't say it.
Ribcracker is offline  
  Reply With Quote
Old 08-30-2007, 03:37 AM   #8
Ribcracker
Flight Junkie
 
Ribcracker's Avatar
 
Join Date: Aug 2005
Location: Oxford, MI
Posts: 1,087
Thanked 40 Times in 39 Posts
iTrader: (0)
Friends: (2)
Wink Woops!

Here's me with the first one.


Attached Thumbnails
Click image for larger version

Name:	Image00003.jpg
Views:	216
Size:	97.3 KB
ID:	39343   Click image for larger version

Name:	Image00004.jpg
Views:	256
Size:	103.6 KB
ID:	39344  

It's easy to be wise. Just think of something stupid to say and then don't say it.
Ribcracker is offline  
  Reply With Quote
Old 08-30-2007, 01:34 PM   #9
pd1
Still Learning
 
pd1's Avatar
 
Join Date: Sep 2006
Location: North of Boston
Posts: 4,098
View pd1's Gallery69
Thanked 588 Times in 550 Posts
Club: Cape Ann RC Model Club
Awards Showcase

Globetrotter Pilot  WAA-08 Pilot  Outstanding Contributor Award 
iTrader: (6)
Friends: (53)
Default

Ribcracker, A question or three.

In picture two, if you grasp the aileron at the control horn position, can you move the aileron up or down?
Not pivoting or rotary action but vertically.

Since it's a mystery I would start with longer horns.

Maybe also shorter arms on the servos as well.

Some tape on the upper surface of the aileron at the control horn position might help as well.

See if this gets rid of the problem, if it does, then slowly increase the length of the servo arms.

Another guess is the control surfaces seem large, is it possible it is too much for those servos to handle?

Maybe stronger servos or gears?

Paul
pd1 is offline  
  Reply With Quote
Old 08-30-2007, 07:52 PM   #10
Arkitexas
Lone Star Flyer
 
Arkitexas's Avatar
 
Join Date: Jun 2006
Location: Bryan, Texas
Posts: 117
Thanked 6 Times in 5 Posts
iTrader: (0)
Friends: (0)
Default

Are you using the same ESC? If you changed ESC's or if the original was overheated during the crash, the BEC amperage capacity could have diminished.

I experienced a case of uncontrolled flutter due to servos overloading the capacity of the ESC's BEC. A servo will draw more current as load is applied (wind on the aileron, thus to the servo motor). Similarly, once a servo deflects to its limit of travel, its amperage draw will also increase. If you are right on the edge of BEC overload, a little wind or end-of-travel will tip the scale and send the ESC into BEC overload. With some ESC's the BEC will turn on and off producing wild servo movements. A plane may show no overload while on the ground, but as soon as wind hits the ailerons, overload could occur. You can test for this on the ground by adding a small weight to the trailing edge of each aileron to simulate wind load in one direction. For your plane, I estimate that a 4 oz. weight would represent a 10 to 20 mph airspeed (depends upon throw and aileron area). What ever the cause, I hope that you locate it soon.

Rick
Arkitexas is offline  
  Reply With Quote
Old 08-31-2007, 02:22 AM   #11
skiman762
FFFC
 
skiman762's Avatar
 
Join Date: Feb 2006
Location: North Carolina
Posts: 1,008
Thanked 3 Times in 3 Posts
iTrader: (0)
Friends: (2)
Default

I meant to say the balance of the aileron not the plane
you might need a counter weight on the aileron
here's a picture of one


Attached Thumbnails
Click image for larger version

Name:	counterweight.jpg
Views:	293
Size:	217.6 KB
ID:	39407  

''To those who defend it freedom has a ring the protected can not hear''
Thank You Uncle Henry 4-April-1945
skiman762 is offline  
  Reply With Quote
Old 08-31-2007, 02:57 AM   #12
Ribcracker
Flight Junkie
 
Ribcracker's Avatar
 
Join Date: Aug 2005
Location: Oxford, MI
Posts: 1,087
Thanked 40 Times in 39 Posts
iTrader: (0)
Friends: (2)
Default

Paul,
Yes, there is slight vertical movement at the hinge line by the horn. I'd estimate it at about a sixteenth of an inch. I still have the wings from the first Jack clone and guess what--no movement! So, it appears as though you've nailed that one. But I don't want to risk damaging the ailerons tearing out the old hinges so I'll try your suggestion of taping top-side at the horn and replacing the HS-55s (there's a reason they call them economy servos) with Karbonite or metal gears. HS-55s are rated at 15-18 oz torque while 65s are rated at 25-30. That should certainly make a difference.
Rick,
This is the same ESC that was in the crash. It's the Thunderbird 36. The BEC has a linear regulator (whatever that means) with a 3 amp max. I'll bet the "economy" servos just aren't up to the task--at least not with a flexing surface. I placed a 4 ounce weight on the TE of the aileron. The aileron drooped about a half inch but the servos held, albeit with a lot of strain noise.
skiman,
I'll be darned! I have never seen any thing like that and I can't imagine how it works. Does it neutralize an intentionally induced resistance in the servo? Wow, I guess I've got a lot to learn.

You fellows have been very generous with your time and expertise. I promise to let you know how this conundrum solves out. I can't get the new servos until next week and the gears are shot on these so I'll put it to bed 'til then. Really, thanks for your help.
Oh, and RobII...what's a live hinge? Is that where you connect the aileron with the covering? Maybe I should try that. It worked on your racer!
Peace,
Bud (Cracker of Ribs)

It's easy to be wise. Just think of something stupid to say and then don't say it.
Ribcracker is offline  
  Reply With Quote
Old 08-31-2007, 03:05 AM   #13
skiman762
FFFC
 
skiman762's Avatar
 
Join Date: Feb 2006
Location: North Carolina
Posts: 1,008
Thanked 3 Times in 3 Posts
iTrader: (0)
Friends: (2)
Default

Well almost all full scale planes have balanced flight controls about 30% from the leading edge just like we do the cg on the plane itself
I guess to be technical and I'm not you really can't stop flutter you can only change the speed at which it starts
I once had a aileron servo horn break in flight and never heard any flutter
I noticed a trim issue and poor roll rate so I landed and found the problem
Anyway if keep having trouble you might try that

''To those who defend it freedom has a ring the protected can not hear''
Thank You Uncle Henry 4-April-1945
skiman762 is offline  
  Reply With Quote
Old 09-09-2007, 03:35 AM   #14
Ribcracker
Flight Junkie
 
Ribcracker's Avatar
 
Join Date: Aug 2005
Location: Oxford, MI
Posts: 1,087
Thanked 40 Times in 39 Posts
iTrader: (0)
Friends: (2)
Default

This is going to be very, very, embarrassing for me but, well...I guess I'd better just come out with it. I'm not a very patient sort so instead of making incremental changes, I went ahead and threw everything I had at the flutter problem, including the kitchen sink. First, I used a hack-saw blade to cut through the pinned hinges, then I Dremeled the debris flush, cut new slots (6 on each side), installed a dozen CA hinges, bought some HS-65MG servos (Yikes! They're expensive!) with metal gears and twice the torque of the 55s. I also bought a 6v switched BEC so the servos wouldn't have to work so hard.
A minute into the first flight, the plane began to roar and shudder. I couldn't believe it! So I brought it down, pinned the stab between my feet and ran up the throttle. The plane began to roar and shake......at the motor mount! Ya see, it's like this...I had modified an Ultrafly 320 watt motor because it was designed to be mounted behind a fire-wall or in one of those adjustable cages. But I wanted to mount it on a fire-wall (stick-mount, actually) and reversing the shaft wouldn't work unless I used a wheel collar in back to hold the shaft in place. Since the shaft was poorly supported, it would destabilize at a certain speed and......well, you know.
So I bolted on my Hacker A30 and the plane leapt off the ground to do some fancy, furious sky work....with no vibration!
I'm such a moron! All that wasted time and money. Sigh.
On the plus side, I've got a solid, well appointed plane that flies like the dickens. I guess things could be worse.
Peace,
Bud (Cracker of Ribs)

It's easy to be wise. Just think of something stupid to say and then don't say it.
Ribcracker is offline  
  Reply With Quote
Old 09-09-2007, 04:14 AM   #15
CHELLIE
Super Contributor
 
CHELLIE's Avatar
 
Join Date: Oct 2006
Location: Hesperia, So. Calif
Posts: 19,054
View CHELLIE's Gallery13
Thanked 2,254 Times in 2,155 Posts
Club: Chino Renegades RC Flying Club
Awards Showcase

Scratchbuilders Award  Scratchbuilders Award  Ambassador Award  100mph Speed Demon 
iTrader: (4)
Friends: (326)
Default

Hi Ribcracker you can consider yourself a Aileron Flutter expert now
Thats how we all learn, sometimes its something simple and sometimes its right infront of our nose, and we just dont see it right away, I had a aileron flutter problem on a gasser, and it drove me crazy, found out that my aileron was very long, and a servo did not work well at the side of the aileron, but worked if mounted in the middle of the aileron, live and learn i Guess, Glad you found the problem, take care and have fun, Chellie
CHELLIE is offline  
  Reply With Quote
Old 09-09-2007, 01:17 PM   #16
pd1
Still Learning
 
pd1's Avatar
 
Join Date: Sep 2006
Location: North of Boston
Posts: 4,098
View pd1's Gallery69
Thanked 588 Times in 550 Posts
Club: Cape Ann RC Model Club
Awards Showcase

Globetrotter Pilot  WAA-08 Pilot  Outstanding Contributor Award 
iTrader: (6)
Friends: (53)
Default

Hi Ribcracker, Chellies right, you learned something and I'll add we learned something too. You have a good plane and all is well.

Good luck
Paul
pd1 is offline  
  Reply With Quote
Old 09-10-2007, 04:09 AM   #17
batman
Member
 
batman's Avatar
 
Join Date: Jul 2005
Posts: 238
Thanked 5 Times in 5 Posts
iTrader: (0)
Friends: (0)
Default

You can relax in the knowledge that, with that aircraft, you will never get flutter. By the way, when I saw the picture of the plane I thought 4 hinges should be enough.

I hope that's soft water......
Meddle thee not in the affairs of dragons, for thou art crunchy and wouldst be tasty with ketchup.
batman is offline  
  Reply With Quote
Reply

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > Electric R/C Airplanes > General Electric Discussions


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
what causes rudder flutter cliffh Beginners 12 10-11-2008 10:10 AM
Video flutter kolchac Aerial Photography 7 06-07-2008 11:40 PM
aileron help pappy60 Beginners 5 06-01-2008 03:36 PM
Aileron Aircraft RandolphNav Beginners 8 03-17-2007 04:35 AM
Elevon Flutter, Stryker B RSS Feed RCU RSS Feed 0 09-20-2006 08:00 AM


All times are GMT +1. The time now is 04:57 AM.


Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation



Page generated in 0.98118 seconds with 61 queries