Aileron Flutter
Moderator: hbartel
Aileron Flutter
I was out flying my Open B Battle Axe today and noticed a "buzzing" when it was really going fast. I suspect that it's aileron flutter. Anyone have a good solution for aileron flutter? Other than smaller ailerons or counter balancing I mean.
I forgot to mention, I'm using an HS85-MG on 4.8V batteries
BTW, I was going to simply edit my previous posting, but the forum won't let me do so. This has happened several times. It says that only the poster (that's me), or the moderator can edit. Obviously, I'm the poster and should be able to edit but can't. This is not the first time this has happened. Here is the error message:
Microsoft VBScript runtime error '800a000d'
Type mismatch: 'rs'
/forum/post.asp, line 642
Perhaps the webmaster can look into this. Thanks!
BTW, I was going to simply edit my previous posting, but the forum won't let me do so. This has happened several times. It says that only the poster (that's me), or the moderator can edit. Obviously, I'm the poster and should be able to edit but can't. This is not the first time this has happened. Here is the error message:
Microsoft VBScript runtime error '800a000d'
Type mismatch: 'rs'
/forum/post.asp, line 642
Perhaps the webmaster can look into this. Thanks!
Gary, the hinge style is the problem. People that have changed to the over and under hinge pairs don't suffer from the problem. The tape on bottom and tape on top method relies on the two pieces of bidi to stay stuck together which they don't after a period of time. If you just want to fix what is there now, sew the hinge seam. That should hold for a while.
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<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by boiler</i>
<br />Gary, the hinge style is the problem. People that have changed to the over and under hinge pairs don't suffer from the problem. The tape on bottom and tape on top method relies on the two pieces of bidi to stay stuck together which they don't after a period of time. If you just want to fix what is there now, sew the hinge seam. That should hold for a while.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
How 'bout someone 'splainin the over under method for us that maybe didn't catch it the first time.
<br />Gary, the hinge style is the problem. People that have changed to the over and under hinge pairs don't suffer from the problem. The tape on bottom and tape on top method relies on the two pieces of bidi to stay stuck together which they don't after a period of time. If you just want to fix what is there now, sew the hinge seam. That should hold for a while.
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
How 'bout someone 'splainin the over under method for us that maybe didn't catch it the first time.
OK, thanks. I understand the over and under hinge, it's what we did on old CL sport models in the 60's. I'm not sure how to sew the current existing tape hinges, but I'll figure something out.
As a side note, you can make your own sewn hinges (CHEAP) by taking some Coverite fabric (the stuff with the iron-on adhesive) The FABRIC, not the film. And cut it into strips about 1 1/2" wide.(Use a fabric cutting wheel and a straight edge) Sew the strips together down the middle adhesive-to-adhesive side with a piece of waxed paper in between. The waxed paper keeps them separated until you are ready to iron it on and then tears out easily before you stick down the fabric. I've used this method on CL Quickie Rat racers and a Q-500 pylon bird and it works well. The heat of the iron may be a problem on foam however. They used to sell some iron-on fabric hinges but they sewed them back to back instead of face to face, and it was the thread that was holding the surfaces together. With the face to face method, the actual fabric is holding the surfaces and I think that's stronger and has less air leakage. (gap seals)
As a side note, you can make your own sewn hinges (CHEAP) by taking some Coverite fabric (the stuff with the iron-on adhesive) The FABRIC, not the film. And cut it into strips about 1 1/2" wide.(Use a fabric cutting wheel and a straight edge) Sew the strips together down the middle adhesive-to-adhesive side with a piece of waxed paper in between. The waxed paper keeps them separated until you are ready to iron it on and then tears out easily before you stick down the fabric. I've used this method on CL Quickie Rat racers and a Q-500 pylon bird and it works well. The heat of the iron may be a problem on foam however. They used to sell some iron-on fabric hinges but they sewed them back to back instead of face to face, and it was the thread that was holding the surfaces together. With the face to face method, the actual fabric is holding the surfaces and I think that's stronger and has less air leakage. (gap seals)
OK, here is the sewn hinge. Just take heavy thread and zig-zag it back and forth through the taped hinge so they don't separate.
I put some red marker on a couple of the threads to show up better.
To make an over and under hinge start with two pieces of bidi and stick about 1/4 th of an inch of the two sticky sides together.
Here is one on a finishe plane. It has been covered with colored tape to fuel proof it and is hard to see.
Since that is hard to see here is a simple model of what it looks like before covering. It is also not as tight for photo purposes.
I put the hinge on tape covered wing and tape covered moving surface. Then I put a protective cover of tape over which also hides the hinge.
I put some red marker on a couple of the threads to show up better.
To make an over and under hinge start with two pieces of bidi and stick about 1/4 th of an inch of the two sticky sides together.
Here is one on a finishe plane. It has been covered with colored tape to fuel proof it and is hard to see.
Since that is hard to see here is a simple model of what it looks like before covering. It is also not as tight for photo purposes.
I put the hinge on tape covered wing and tape covered moving surface. Then I put a protective cover of tape over which also hides the hinge.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by ZenManiac</i>
<br />1. Check for any slop in the connections from your servo to wing control horn.
2. Also, sometimes cutting a 45-degree corner out of the outboard end of your aileron is enough to cut back on the flutter.
3. Fly slower. [:D]
-= Dave
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Servo slop. Good idea. The standard Battle Axe aileron servo installation method has the servo attached to the coroplast center section protector but NOT to the actual wing. The coroplast is held in place with the rubber bands and can move around a bit. It may be that this method is OK for SSC speeds (for which the Battle Axe was designed) but not for Open B speeds. I'll put in a mounting plate on the wing like Boiler does and see if that helps.
The ailerons are already chopped so that part is OK. BTW, the reason that the F-15 has the tip shape that it does is to avoid flutter.
Fly slower... yeah, right...[:D] when I'm slowing down to take two cuts off of you instead of just one...[:0]
Thanks, guys!
<br />1. Check for any slop in the connections from your servo to wing control horn.
2. Also, sometimes cutting a 45-degree corner out of the outboard end of your aileron is enough to cut back on the flutter.
3. Fly slower. [:D]
-= Dave
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
Servo slop. Good idea. The standard Battle Axe aileron servo installation method has the servo attached to the coroplast center section protector but NOT to the actual wing. The coroplast is held in place with the rubber bands and can move around a bit. It may be that this method is OK for SSC speeds (for which the Battle Axe was designed) but not for Open B speeds. I'll put in a mounting plate on the wing like Boiler does and see if that helps.
The ailerons are already chopped so that part is OK. BTW, the reason that the F-15 has the tip shape that it does is to avoid flutter.
Fly slower... yeah, right...[:D] when I'm slowing down to take two cuts off of you instead of just one...[:0]
Thanks, guys!
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Going to one servo per aileron will fix it too, as long as the hinges are good and there is little slop in the linkage. Also the length of the servo arm from the center screw to the pushrod should be shorter than the height of the aileron horn. The servo needs a mechanical advantage especially if you are using just the one servo. Two is better, its also easier to trim.
For a fast B plane I think 2 servo's are almost required. Be carefull as flutter has a way of destroying servo's in short order! If you hear buzzing pull hard elevator and reduce throttle real fast to slow down or you'll have a stripped servo in no time! You also need a relatively strong servo. They can also just get overpowered at high speed. I ususally run 6 volts on open B planes.