Greetings,
I lost my Showtime yesterday, due to some really extreme flutter......I was pulling through a 45 degree downline and started to add throttle on pullout, and the wing started to flutter really bad...I cut the throttle immediately, and actually saw the wing fold up to about 30 degrees, and BAM, it was over.
I had newer ( about 20 flights ), 92 oz servos in the ailerons ( they are plastic geared though, and both were stripped out ), and I really didnt have any gap in the hinges. Although underpower for 3-D Standards, I had an OS .91 four stroke in it.
I guess what I am really wondering, is if I should build another or bag it. I just am not sure that if I build another, the same thing wont happen. Maybe the servos should have been metal geared, I dont know......
I havent seen any others in the Showtime threads have this happen, and the Showtime seems to be just like the Matrix I have, and I havent had any problems with that plane at all, and it seems as though this plane could handle a bit of speed anyway......
Any thoughts?
Thanks

Sorry to hear about your Showtime. I did not have a flutter problem but I did split the fuselage on a less than perfect dead stick landing. I bounced on the main gear and it looked like a harrier landing.

I called Horizon to possible warranty the Fuselage and they kindly told me "no". To make a long story short I repaired the damage this week and found that the Balsa was soft and paper like (not much strength). I cut out the offensive section and sliced square stock in. I then added strips of light ply to splint the joint. I also added light ply splint to the other side to prevent another fracture.

If you are planning to build another one you might want to carefully check this area.

I should add that I am a fan of Horizon products and own (or owed) about 12 to 15 of their planes. This is the first time I have had a problem with quality and it is possible that the bugs have not been worked out of the production line.

Thats the first case of flutter I've heard of on the ST. What was the linkage set up (lengths) on the arms and horns? Proper mechanical advantage is absolutely critical when you are running 3D throws and bigh surfaces. I'd also go with metal geared servos.

Hello Mike,
Thanks for the reply......The stock set-up is what I used with the arm being a Dubro HD arm, 1 1/8 long from center of servo to center screw of ball link ( stock H9 ). The measurment of the link on the screw on the aileron ( the one thats glued in ) was set @ 27/32 high, just like the manual says.
Nothing was loose, and still isnt....just stripped servo gears. The angle of the link isnt perfectly straight, but I dont think it really is on any of my planes.
The wing folded just aft the wing tube, and the aileron is still in one piece......bolt is still glued in tight, etc.
I want to build another, but am not sure of the cause of the flutter, and am apprehensive to do another. I work at a rather large Hobby shop part-time for fun, and alot of people buy what I fly ( I am like a guinea pig ), so if I have a problem with something, they want to know about it before they buy one, so its important for me to come to a definate conclusion. I will probably be sending the wing panel to Horizon this week so they can take a look at it. At least if there was a problem with glue joints or something, I know I can build another plane and not worry so much about it.....
I was flying this plane more sport-like than any hard 3-D, so I just dont get it......
Thanks alot

A few weeks ago a fellow club member was flying his Showtime, Mike I think you know him, Brian J from Venture Hobbies, when his throttle became stuck wide open. He flew for about 5 minutes before it ran out of fuel. This plane was screaming throught the sky, he has a YS 110 in it, absolutely no flutter. I believe he has JR 8311's on all the surfaces.

Unreal...... I just dont get it....I definately wasnt flying fast! I have another built, but I am not sure I am going to fly it anytime soon...... What doesnt make sense to me is that when you look at the aileron set-up, the rod between the linkages is angled down from the servo to the link. As a friend recently pointed out, the lower the link, ( on the screw coming up from the aileron ) the less leverage, and the higher the link, the more leverage, so that it would take more force to get it to flutter. I set it at 27/32 just as the manual says, but I am really think it should be set even ( link higher up on the screw ).
Problem is, it seems nobody else has had this problem ( or at least not posted anything about it ), and I know it was nothing I did flying wise.

I have a os 1.08 on with a 16x8 apc. with out the SFG's on it I flyit like a true pattern ship. I throttle back on the down lines, and open it up when I'm level... full throttle passes no problem.

I used Hitec HS945MG's on ailerons, elevators and a JR8611 on the rudder. SWB servo arms, I also sealed all gaps.

With this set up I can do huge jet like loops EZ

If you are talking about the DuBro HD Glass filled plastic servo arms... this may have been the start of you problem. They do not like Ball links! Ball links will twist the servo arms, clevis's will not. The ball part is so far above or below the arm that it twist. This is why I stopped using them.

Try it... hook one up and power up the servo and test it at 1 1/8" arm, it will flex with the ball link. Then try it with a clevis.

Scott

Interesting post regarding Dubros HD's and ball links. Seems to support my argument that the Cr@ppy nylon horns as supplied with the F90 are way below spec. This explains why our original F90's fluttered but now do not despite our best efforts when equipped with proper metal HD/giant scale aileron horns. Interesting that Mike suggests metal geared servos - what does the manual say. The F90 manual says 50oz in entry level digis are okay, and it has huge ailerons...Now if only Mike would bother to respond to my comments on the F90 flutter thread in this forum, Mike???

I have replaced the Dubro ones on the ailerons with the metal H9 3-D arms.....The manual doesnt say anything about using Metal-Gear servos, but I put those in too. If I get flutter this time, I will be real suprised...I also changed the the height of the swivel clevis to be more in line to the servo arm.......Unfortunately for some of us, the manual "forgets" that not all of us are Extreme 3-D pilots.......
Thanks for the info on the Dubro arms......

I read in another thread that the servos you used on ailerons was Futaba S9252. I also installed that servos on the ailerons, but there seems that these servos in conjunction with the supplied linkage and the weight of the ailerons all together forms an oscillating loop. Both my ailerons would "flutter" when the plane stands still. I have not tried to fly with these servos so I don't know how this would affect any real flutter once airborne. I don't know if this can have something to do with your flutter, but it may have some influence. Maybe you where very near the "natural" oscillation frequency (as I suspect your where as mine where spot-on with the same setup as yours), and that this triggered the flutter in air.

Changed to S9451 on the ailerons and they are rock solid without any oscillation tendency (yeah, I know they are a bit overkill for this plane...but they work!)

I'm using the 9252s in the elevators though and they do not seem to have same problem. I can see a slight oscillation there also, but only for a fraction of a second if the servos is stopped really quick.

Are you using the 9252s on elevator? I'm getting a little nervous about using this servos now.

Regards
OAK

Oak....
I havent used these servos on anything that required high torque, but they are rated at 91ozs, but the key seems to be that they are plastic geared.
I had a good six or seven (?) flights on it without a hint of flutter, and it struck basically without warning. I followed the directions in the manual ( although I didnt seal the gaps, because there really werent any ).....I think it was a structure problem. I flew a new one yesterday with the 9451 servos in the ailerons, and once again, didnt notice any flutter......
I think I will use metal geared servos from now on in planes with large surfaces to be safe, but it still doesnt explain why this happened in the first place. I also changed the servo arms from the glass-filled Dubro to the H9 aluminum ones.
I didnt notice any oscillation on the servos, or anything out of the ordinary for that matter with these servos on the first one...otherwise I wouldnt have used them.
I think I would just use metal geared servos on this plane all around if I were you.....
Good luck with your plane......
BR289

You can still use the dubro glass filled arms, you just can't use ball links in them... they require clevises so that control forces are in-line with the arm, not above or below.

I know this is an old thread, but I think I may have witnessed a similar incident on my friends Showtime.

What I saw wasn't flutter, the wing actually flapped like a bird. Mike wasn't over flying his plane, as a matter of fact, I fly mine a lot harder than he flies his.

This is what I wrote in another forum, it tells the story well.



Well the day started like any other, load a plane in the van and go to work . I was going to meet Temptation at the field, after work, to get a few flights on our Showtimes. Mike called around 8:30 and said he wasn't going to make it, he had some work this afternoon that had to get done. I said to my self, "self", I'm going anyway.

Sooooo, about 1:00 I started looking for reasons to leave the job. Sweet!!! One of the doors is the wrong size, I better go and get the right one, I'll come back tomorrow .

I had 3 or 4 flights in when my phone started ringing, "Are you still at the field?" Mike asked. I said, "Listen to this", as I proceeded to rev the throttle on my Saito 150...

His response was such that I can't write it in this forum, but you get the picture. "I'm on the way, be an hour or so".

Mike showed up about 4:30, with his Showtime and a friend from work, so I figured, "it's show time"...

I was in the air when they got there, so I played around for awhile and landed to talk with Mike. He was finishing the assembly of his bird, so I waited for him to put his first flight in. He fired it up and rolled to the line, taking off as smooth as always in a slow methodical climb. His flight went as usual, couple of dozen fast rolls in a vertical line, then slid into a hover, finally a little harrier action nice and slow. A few passes later, he came across the field again, snapped into a hover, held it for 10 seconds or so and did a 3/4 throttle climb with rapid rolls on the way up.
At the top came a stall turn, then idled on the down line. At 50 ft. or so, he leveled off and powered up. Shortly after he leveled off, all hell broke loose. The right wing started flapping like a sparrow! Mike yelled, " Flutter!"

Flutter my *****, the whole wing flapped like a bird. He immediately backed the throttle down and the plane went into a slow spiral. I heard the engine come up slowly and saw the plane level off, by this time he was at the weeds. The plane came up and went between two trees, I thought it was a goner for sure, then he was above the tree line, I said, as calmly as I could, "Mike, you better get that thing on the ground, slowly". I didn't have to tell him that, but I did it out of habit from helping newbies all of the time.

He brought the plane around real slow, just above stall speed and made a perfect 3 point landing. After we did the normal congrats and praises, for the save, we started to look at the plane. I grabbed the wing, to check for damage, and was able to flex one wing half almost an inch, you could plainly see the balsa buckle. When Mike removed the wing from the plane, you could plainly see the ribs, near the wing socket, were broken all of the way down. When the wing flapped it actually broke the ribs past the servo mount.

We couldn't see why the ribs broke, he wasn't flying hard enough to break anything, in my opinion. The only thing I can figure is there might have been a cracked rib at the end of the socket. A small crack is all it would take to start a big problem.

I figured I might as well fly mine and see what happens. So up I went, immediately slamming this thing around the sky. I was going to find out if it is a design flaw or just one isolated case. I'm sure Mike will chime in here and contest to the fact that I put my Showtime to the test. I did everything from full throttle tumbles and flat spins to high speed vertical and horizontal walls. No problems with my bird...an isolated case.

We never did get to shoot the video of "Dueling Showtimes"...another day.

__________________
Ken Thompson

Mike has since been in contact with Horizon, I'm sure the problem will be solved. With so many Showtimes out there and so few problems, I think I will keep mine, and maybe get another.

Please read through my posts in this thread: http://www.rcuniverse.com/forum/m_3729312/tm.htm

Flutter will almost never start in a wing. It starts in a control surface and if it does not dampen, it can migrate to the entire lifting surface very quickly. That is what I suspect here.

Were the aileron servos stripped when the model was landed? What were they, and what were the aileron linkage mechanics?

Mike,

The servos are JR 4131's, and they are still in wings. The wings are on the way to Horizon and should be there by Wednesday of next week.

The box is addressed to Josh's attention, so you should be able to see the setup and geometry.

Thank you for your concern.

Ken Thompson

Gotcha. But are the gears striped in either of the servos? 4131 are plastic gear servos. I would not use plastic gears if setting up 3D throws.

Mike,

If I am not mistaken the gears were stripped in at least one of the servos. I realize that it would be normal for the servo selection to be something with metal gears in large scale planes, but this is a 90 size plane, I wouldn't think metal gear would be necessary. I don't remember my manual recommending metal gear for 3D throws, of course my memory isn't all that good at times

Ken

Hi Everyone,

I witnessed the events as described by kenandannie. Yes, I was there. The Showtime was only on it's 4th or 5th flight and was being flown very conservatively. I really would like to be there when the wings are inspected. I understand that they have been sent back to H-9.

I am a quality engineer and I did a search in Mike's Forum under 'Flutter'. I understand Mike's knowledge and point of view on flutter and using the correct servo set up, etc. But there was no flutter in this case, the wing simply came apart inside and began to flap severly exactly as BR289 and Spoiler described in their posts. I believe that BR289, Spoiler and Kenandannie have presented enough information to warrant a throrough review of the building process. It is time to take a look at the wing building location. Are there control numbers or production runs stamped in the wings? You need to find a clean point working backwards to the time the wings in question were built. This should have been standard practice after Spoiler brought up the problem in July, 2005. If I let product go down the building process (knowing the information I have been provided) without finding reviewing the building process and creating a clean point, would be gross negligence and I probably wouldn't have a job either.

Ken took his ST up afterwards and duplicated the same manuevers over and over - in fact he put the ST through a lot tougher testing and his stood up well and his plane has more flights on it.

I have been saving my hard earned money to purchase a ShowTime to fly this Spring. I believe it is a great airplane. I have read all of the reviews and feedback that I could find. No doublt about it - it is a great flying airplane. But now, I will not purchase one until I am certain that the wings are being built properly - I can't take the chance on spending that kind of money. I don't want to put all my expensive equipment in a plane that is prone to failure.

Since I am ready to purchase I will have to go with Quique's Yak. I have also heard great things about this plane.

QQ's Yak is a great airplane. You should enjoy it. I'm going to get the 102" myself to play with.

To answer your questions, no there is not a mark on the wing showing the production run. There are also no changes that have been made to the design or production process. There are also no instances of this happening except in the isoluated cases where the mechanics are in quesion, which are very few.


I stand by what I said. Any model with largely oversized surfaces, particularily ailerons, will flutter if not set-up correctly. My analysis based on experience and observation is that the aileron fluttered, the servo gear stripped, ver quickly, and they now unattached aileron went into a very high amplitude flutter which excited the entire wing. The servo gear being stripped supports that as well. Unless you look this in slow motion video, it will look like the wing began to flutter or flap instantly. You'd never see the aileron flutter prior to the servo gear letting go in real time.

I do have a few specific questions abou the model that will help me better understand. I know iut had 4131 servos on ailerons, and I know one was stripped when the model landed. Can you tell me this:

1. How much total aileron travel on high rate (degrees of deflection)?

2. What are the Travel Adjust values (ATV) for aileorn?

Thanks!

Well Mike,

I can see that you have already taken your position. Have you seen the wings that were sent back to Josh in tech support? Perhaps you can give us a pictorial breakdown. I would ask that you actually call the person who owns the plane. He is not a member at RCU so he as asked me to relay that he has left two voice mails and you haven't returned his calls yet. His name is Mike as well. He can answer all of the specifics.

Hello,
I had stripped servos in boths of my wings ( they were nylon geared ). I was super-sure the geometry was right on with the manual.
Unfortunately, I had to bite the big one and buy another, which I almost am afraid to fly! I have only flown the new one once since I put it together. I was definatley not flying the model fast, or even very hard. My friend did though, and hes a great up-and -coming 3D pilot ( Chris Maier ) who did the Ultimate 3D DVD with the Extreme Flight Yak last year. If anything was going to break, it would have when he flew it!
I originally thought I didnt seal the hinge gaps, but I had. I re-measured the horns, and they were right on with the manual, so either it was the Dubro heavy arms with the ball links from H9, or a bad wing.....either way, I lost........

Yeah; definitely food for thought. I'm having to re-do my wing incidence, and while I'm at it I'll go to small servo wheels to seriously reduce throw. I'm using the airplane for IMAC back-up, and I've got the servos dialled-down so much that one click of trim makes a BIG change.

This model was intended for 3D throws; the servo holes in the wing are offset from the aileron hinge point quite a bit; so much so, I'm concerned about the linkage binding, since it won't be at 90 degrees to the hinge line. Mike said it should be okay... we'll see.

The good news is that, even with the large amount of aileron trim I was carrying due to the cock-eyed wing incidence, the plane flew beautifully. The excessive trim was causing major problems in some of the IMAC manuevers, but for a "regular" sport plane it would have been fine as it was. This is one smooth ship; which is why I'm taking the trouble to correct the problem. It ought to be a dream, once I get the wings aligned...

Personally, I would use metal geared sevos if you are setting up 3D throws.

As Mike said in the previous post, use metal gear servos. I have since pretty much sold all my Nylon geared servos, and purchased metal geared ones for most of my aerobatic models......