MMcConville

My Feedback: (4)

Hi Guys, Hopefully this will clear this up and put it to bed. I was able to get the wings from this model and look into this as well as tt Mike the owner. After looking at them, I have no doubt what I described in post 14 is the case here. I hope this will be helpful to any of you guys looking to get a 90 size or larger 3D airplane in the air. Here is what I found:

1. Both aileron servos were stripped. Tell tale sign that flutter happened.
2. The mechanics were such that the aileron had 45 degrees throw in each direction at full servo sweep. Good for 3D, but demands a lot from a servo. Makes it very suseptable.
3. Aileron hinge gaps were not sealed. This is a good measure that can help inhibit flutter in some cases. It also makes for a batter flying model in general. Just do it.
4. Servos were 4131. These are plastic geared servos. They were one of the best on the market when they came out in the mid 90's, and are still very good servos today. But IMO not the best choice for using on a 90 size model with large surfaces and 3D throws. They will be right on the edge and the gear train could strip.

What happened was this. The ailerons tried to deflect against the servo. The force of the aileron movement was greater than the servo gears could stand, and the gear stripped. Once the gears stripped, the ailerons are effectively disconnected from any servo and are free floating. This happens almost instantanously. Once the ailerons became free floating, the ailerons begin to flutter at a high frequency and a very high amplitude (they move up and down a lot and very quickly). The force on the wing structure becomes HUGE! This will make the wing "flap" up and down till it either stops (by landing) or the wing fails.

Though the servos were stripped in both wing panels, only one panel appeared to have damage. I cut it open to take a closer look, and honestly I was amazed at the little damage I found.

Some ribs had broken vertcal members behind the spar. Missing pieces but not structural. The leading edge sheeting showed compression breaks on top and bottom directly at the end of the wing tube. The up and down flapping would do that. There was a crack in one seear web along the length of the tube.
But, No shear web glue joints were broken, the main spar was intact and all glue joints of the spar to the webs, ribs and sheeting were fine, the wing tube sockey was still secure.
I'm familiar with this type of failure mode and have seen it on various models. More often than not, it causes a total structural failure before the model can be landed.
I'm amazed that one wing panel had no damage, and even the one that did, was still strong. Honestly, I'd bet a dinner that the panel could have a metal geared servo installed and flown w/o failing it.

Lessons learned I guess are that the wings are even stronger than I thought, and its best to use a metal gear servo on a model this size if setting up mechanics to support 3D throws.

BR289

My Feedback: (106)

Thanks Mike.....thats really cool the way you went into it and checked things out!
Blair

kennyandannie

My Feedback: (2)

Mike,

Thank you for handling this by investigating the wings, that, in my opinion, is the only way to know for sure.

I also would like you to know I have talked to Mike and am stating in this forum, I will continue to purchase Hanger 9 products and deal with Horizon.

Thank you for handling this in a professional manner, you will have my future business.

BTW: Since this one is laid to rest, what is your next 3D monster? I think I want one Preferably Giant Scale...

Ken

shanes300

My Feedback: (8)

I am glad I went ahead and put the 8411s in it that I had. I cant wait to get it in the air. I also checked the wing incidence as Steve suggested, mine was dead on with each other.
I hope to fly mine this weekend if the rain holds out...
Shane

kennyandannie

My Feedback: (2)

Shane,

Good luck with the maiden, you are going to love this airplane. I speak from experience when I say, it's the best flying all around plane I own.

Ken

LSP972

My Feedback: (13)

I set it up per the book; which gives 3D throws. But I wasn't flying it with those. I had the throws dialled WAY down for IMAC. Still, I experienced the same "stationary fluttering" (the control surfaces chattering big-time with the model on the bench) that OAK mentioned, with the 9252 servos I had in there. I replaced these with two like-new 9252s; same deal, though not as bad. So I put in 3305 metal-geared analogs. So far, no chattering.

What a welcome relief, at $39 per servo. A fellow at the Mount Pleasant IMAC Boot Camp with a big 40% plane, that he flew the SNOT out of, told me that while digitals are all fine and good, he has a full set of these 3305s in that 40% monster that are three years old and going strong, and the difference in "feel" between these inexpensive analogs and big-buck digitals is, in his opinion, not worth the extra $60-$70 per servo.

I'm starting to buy into that line of thought. It occurred to me, while re-doing the linkages/aileron servos on my ST, that this plane with regular servos can fly tons better than my meager ability to control it. I've gotten too deep into this "precision flying" mindset; I'm beginning to feel like the guy with a Raptor 30 (cheap plastic heli) who buys two grand worth of servos and purple widgets to put on a $200 machine. Time to back off and take a breath...

Anyway... I fabricated the wing pin hold-down last night. I'm only going to move the left wing's incidence for starters, since when I re-measured according to Mike's suggested method, the right wing appeared to be real close while the left wing was way out. We'll do that tonight; I'm eager to fly this model some more.

BTW, Mike, you have my (and no doubt many other's) respect for the way you deal with issues on these forums. That's probably why you catch so little heat from unhappy customers, since your up-front and honest approach is hard to argue with...

.

MMcConville

My Feedback: (4)

Thanks for the comments guys. I do have a few comments to the last post. It brough up a point I wanted to make but forgot.

Thanks fore the comment that it was set up for 3D throws but dialed down. I meant to addres that. I'm not sure you meant that the mechanics were set up for 3D throws but the throw turned down in the TX (with ATV/TRavel Adjust or DR) so max throws werent 3D. But assuming that was what was done, it important to point out that that is irrelivant. The amount of throw at the surface doent matter. If the mechanics are such that 3D throw can be achieved with full servo sweep, how much you are limiting the servo doesnt matter., the mechanics are the same as the model with throws thurned up at the TX.
Another point there is that flutter potential aside, its never a good idea to reduce the servo travel to get the throw you want. Set the mechanics so at nearly full servo sweep you get the deflection on hi rate you want. If you need to reduce the servo travel then instead change the linkages (shorter servo arms and/or longer control horns). If you reduce it at the TX you end up with things than will negatively effect the performance of the airplane:

1. Less servo resolution
2. Centering innacuracy of the servo translates to a higher centering inaccuracy at the surface
3. Less torque is seen at the surface. Blow back is more likely.

I think that may not be the case with your model Steve, but I wanted to make that point. I think we as pilots in general get lazy to try to do everything we can through transmitter based programming and not at the model. I know I've been guilty of that, its easier, but its not ideal in many cases.

LSP972

My Feedback: (13)

It WAS the case with my model; you made me realize the error of my ways a few threads back...

I've got small servo wheels all-around now (except for rudder) on the ShowTime, and will be doing the same thing on the Extra 260 while fitting it up for the BME 50 gas engine.

goldenclan

My Feedback: (5)

This dosen't involve flutter yet, but wanted to get some feed back on a problem that I am having with my showtime 4d. No flight on it yet, I have hitec 645's on all of the surfaces and a 5645 on the rudder. Just finished up the building process and was setting the throws on the elevator. I centered the elevators on using the counter balance and looking from the back of the plane, the left elevator is about 1/4 inch plus lower than the right elevator. I have already drilled the holes and secured the elevators. So If I have to adjust the incidence of the elevator, I will just flip the tube over and re-drill. The wings look good so far. I did the tape measure thing and checked the leading edge and the trailing edge near the fuse and they are within about 1/16 of each other.
Other items on the plane
horns are 1 1/4 dubro hd
2700 mha ni
saito 125. Haven't decided on a prop yet, any suggestion?
jr 7 channel receiver
jr 8310 radio

LSP972

My Feedback: (13)

Use an incidence meter on both wings and stabs. And, I strongly suggest gluing the stabs in place once you're sure they are right.

An incidence meter is the only way to know for sure. This airplane is so neutrally stable, any misalignment in either wing or stab will show up as a major roll trim correction.

MMcConville

My Feedback: (4)

My guess there is a twist on an elevator. Look for that and correct it with a heat gun if thats the situation.

goldenclan

My Feedback: (5)

I will post a few pics tomorrow to show what it looks like. But I will check for warping. Going to get the hangar 9 incidence meter tomorrow, borrowed a friends awhile ago and now can't live with out it.

goldenclan

My Feedback: (5)

Ok Checked the incidence with the hangar 9 meter. Sitting on the kitchen table, wings were with in 1/2 degree. The elevators were a different story all to gether. Checked for warp, did not see any. Put the meter on it from the wings and the left elevator half was 2 degrees positive of the right half. Going to get the dremal warmed up tomorrow and put a fix on the elevator. Seen the video of a similar problem with the extreme flight yak and have it on my computer. Should be able to knock it out in an hour or so. Will let you know what happens.

stek79

Hello,
can you explain that procedure in detail?

The plane I'm building probably has a warped elevator, it is made of foam covered with balsa and Oracover. Do you think it is possible to correct it Mike? If so HOW?

MANY THANKS!!! Good infos, as usual

goldenclan

My Feedback: (5)

Not sure how yours is connected to the fuse. The showtime has an alunimum rod for the main brace and a carbon fiber pin for alignment at the leading edge. How is yours connected?

stek79

Hello goldenclan,

my stabs are connected in the same way, I think. But the problem I have is not with the stabs, but with the elevators. I have about 1,5° difference between root and tip incidence, and I would like to fix it. I other words, in my case it is the elevator (hinged part) that is a bit twisted, not the stab.

I've tried with an hairdryer, but with little results, albeit the twist is very little... any ideas?

goldenclan

My Feedback: (5)

sent you a pm stek79

goldenclan

My Feedback: (5)

Here are the pics of the elevator

goldenclan

My Feedback: (5)

sorry about the mess in the back ground of the third photo, my dog got hold of anything it could during the night but it is cleaned up now lol.

goldenclan

My Feedback: (5)

Wow!!!! Just finished up the breakin of the saito 125. After 4 tanks of keeping it under 4000 rpm, Still have not started to lean it down from the 5 turns open yet, but the throttle response was right on the money!!!! I can't wait to get it to the air strip and lean it out abit. Runninng a 16X6 prop (wood) and there is some power there with is running rich. Cant wait to start on the saito 220!!!! (20X8) for it