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u can do 46 wing problem

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Old 08-11-2003, 10:48 PM
  #1
chip581
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Default u can do 46 wing problem

How many people have had problems with the violent flutter at low speed that has caused the wing and tail to brake on the u can do 3d 46 and has great planes givin you the run around and said that they haven't had any probems
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Old 08-11-2003, 10:59 PM
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shadowspring
 
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Default u can do 46 wing problem

I don't have one but i seem to see a lot people complain about the wing snapping on those things.

Little wonder why I don't have one!!!!
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Old 08-11-2003, 11:01 PM
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Default u can do 46 wing problem

i have about 30 flights on mine so far, every thing is fine, ive done diving snaps of around 60 mph, and alot of other high speed manuevers with no fluttering at all. i am also using 3003 servos all around except for rudder. remember with large surfaces like this it is a MUST that the control surfaces be as close to the stabilizing surfaces as possible. i can barely get a peaice of paper in between mine.
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Old 08-11-2003, 11:41 PM
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Default u can do 46 wing problem

all of the surfaces are as close as they can be and they are gap sealed and i changed to 4-40 rods on everything but it still fluttered very hard at straight and level flight at about 1/2 throttle, and the wing broke and the tail cracked.
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Old 08-11-2003, 11:56 PM
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Default u can do 46 wing problem

Mine blew apart on the first flight ... all ready have the replacement from GP!! They only asked me to send it back! No other questions!

They didn't say what happened, but I think it had some broken ribs. It fluttered then came apart at the servo mount. Also I noticed that the rail that the servo sat on was not glued that well, but I don't think that this started the flutter. I believe that the rib right next to the servo was cracked and this is what started it.

The first one all the covering was really loose. The new one the covering is nice and tight. It took me 2Hrs to get the covering tight on it. In hind sight the loose covering on the wing MAY have been from broken ribs. No way to tell now, they have it.

Give them a call. They will take good care of you! Oh... Yes... they changed the CG range also! 4" to 6" from the leading edge!

Later, Scott
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Old 08-12-2003, 12:12 AM
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chip581
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Default u can do 46 wing problem

well after the first flutter i called them and they told me that they had not had any problems and they just didn't seem to believe me and they just kept transfering me to different people. so i flew it again on saturday and it flutter very very hard but didn't blow apart so i landed it. the spare was broken and the trailing of the wing was too. the tail was also busted.
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Old 08-12-2003, 02:16 AM
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Default flutter

On my first flight my u can do fluttered and all the wood under the stab broke. So i glued it back together and recovered it .I also replaced the rudder and elevator servos which were standard servos with hitec 605s and i sealed the elevator hinge line. I havent had any flutter since. Although yesterday i was performing an inverted elevator and about twenty feet from the ground the engine quite and it crashed.
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Old 08-12-2003, 04:24 AM
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Default u can do 46 wing problem

please guys flutter is a huge problem on the new big control s ervices 3d type planes, because we fly them to fast, put standard servo,s and expect them to do the job and then we blame the plane. here on rcu a lot of experienced people will tell you all about this so take time to read before you go out and have lot's of bad luck with your new plane.

on flutter

We have all seen a flag fluttering in a breeze so we all know what flutter is. The control surfaces on your RC plane can do the same thing. Actually, the whole wing can flutter, too. Flutter is caused by 1. speed, 2. poorly designed or constructed control surfaces and 3. loose, sloppy control hook-ups. Flutter is bad. Flutter is destructive. You may not have seen it on an RC plane, but it is waiting out there to get you. Be aware it can happen.
The onset of flutter is heard as a buzzing or vibrating sound. It is a distinctive sound and virtually everyone at the flying field who hears it will look up. When you fly faster than the buzzing speed, things start breaking or falling off. Clevices, solder joints and servo arms will fail. The servo shaft the arm attaches to will shear off. Hinges will fail and control surfaces will fall off. Whole wings and fuselages will break. All it takes is speed and a little slop in the controls.
Here are my words on flutter:
NEVER, NEVER, NEVER ROUND OFF ANY TRAILING EDGES!
I don't care if the kit plans show it, they are WRONG! If a so-called "expert" tells you to round off any control surface trailing edge, he is an idiot. If the "expert" tells you he rounds his trailing edges off and has never had flutter he is still an idiot, but one who has the skills to build a tight system and who is lucky he has never flown past the flutter threshold airspeed for his planes. These people are doing a great disservice to the modeling community, especially the newcomers who they influence and who, though lack of skills like the "expert," will probably get flutter and may destroy an airplane. You can quote me on that!
Go look in any basic aerodynamics book and look up flutter. It will agree with me. When it comes to control surfaces, STRAIGHT LINES AND SHARP CORNERS DELAY FLUTTER, while CURVED LINES AND ROUNDED CORNERS PROMOTE FLUTTER. Go ask a pylon racer. He'll tell you about inlaying 1/64 ply in the trailing edge of the ailerons so he can sand it to a sharp edge. If you can't make the control surface a straight like to a sharp trailing edge, leave it square and sharp on the corners. Sharp corners preclude flutter while rounded edges promote flutter. NEVER ROUND OFF ANY TRAILING EDGES.
Look at a flag pole. They are rounded and every flag flutters. It's not because cloth naturally flutters, it's the pole.
As for the numerous ARF kits which are sold with rounded of trailing edges, let's look at the economics of the situation. Most people who are not knowledgeable about aerodynamics and flutter automatically think a squared off trailing edge is bad. They erroneously think, "Curves are nice, curves are sexy, curves have to be better." Just looking at a squared off trailing edge, you would have to think it would produce a lot of drag and slow your plane down several miles per hour. I think many people believe a plane with squared off trailing edges won't even fly so they certainly don't want one. It is my opinion the marketing staff insists no one will buy the plane if the ailerons have squared off trailing edges, so good aerodynamic practice is over ruled and the trailing edges are rounded off. Hooray for marketing!
To compensate for this, the building instructions may say, "Keep speed down," "Do not dive at full power," or the sneakier one, "Use long control horns and put the clevice in the furthest out hole." This is to minimize the effect of any slop in your controls. But many fliers will not do this and will end up blowing ailerons off the wing or shaking the tail off the plane.
For trailing edges, here are the choices, and I speak as an engineer and a long time modeler who has sadly and personally verified each of these.
1. Best: A straight line to a sharp trailing edge. This is best and has the least tendency to flutter. It's like commercial aileron stock or trailing edge stock. Don't get me wrong here, these can still flutter, but they will do so at a higher speed than the others. You must still eliminate springy pushrods and sloppy connections.
2. Second best: Straight lines on both sides to a square, flat trailing edge. Squared off trailing edges , too, are very flutter resistant. Think of the elevators of a giant which are made from 3/8 square sticks. DO NOT ROUND OFF THE TRAILING EDGE. Leave the corners square and sharp. I do all mine this way. I recall seeing a magazine article where the designer of a certain Extra 300 kit which specifies rounded trailing edges spoke about the plane. He said to be sure to use the longest control horn and have tight controls. All this does is hold the flutter off until a higher speed. Leave 'em square. It's easier and it works. If you already have the TE rounded off, glue some 1/64 ply vertically on the trailing edge, fill in the gap with Model Magic and Monokote over it. This will give you a sharp, square corner.
3. Next to worst: Sharp trailing edge, but a curved surface. Not very good from a flutter standpoint. These will hold up better than just rounded trailing edge. You probably had to carve some to get this shape and you actually wasted your time. Use long control horns and as tight a connection as you can get. Next time, leave it square or use a sanding block or a plane and carve in a straight line to the trailing edge.
4. The very worst: Completely rounded trailing edges. Think back to the flag pole. If you build up a giant tail surface and round off the trailing edges, you are looking for flutter. If you don't get flutter, it is because you aren't fast enough and you have a really tight control setup. DO NOT DO THIS.
OTHER THINGS YOU CAN DO
Use long control horns and long servo arms, and use the outer most holes. If you have any slop in your control system, the longer arms minimize the angular movement which can allow flutter to start. If you need more control throw, get one of the extra longer servo arms available.
Use stiff pushrods or pull-pull cables, especially on rudder. Tight pull-pull cables take all the slop out of a system. Very good for flutter prevention. Brace the pushrods inside the fuselage if you can.
As a last resort, you can counter balance the control surface."
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Old 08-12-2003, 04:28 AM
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Default u can do 46 wing problem

ps. the flutter article is by Ed Moorman and i have posted it many times on flutter related threads hope it helps.
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Old 08-12-2003, 10:11 AM
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Default u can do 46 wing problem

I was level and at less than half power when mine let go. I don't think I was going 40 Mph, maybe closer to 30.

Scott
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Old 08-12-2003, 12:08 PM
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Default u can do 46 wing problem

flutter with these masive controls and just a little slop can happen at 20/25mph and damage your plane.
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Old 08-12-2003, 01:21 PM
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Default u can do 46 wing problem

I want to be sure I understand some of these points since I am very close to purchasing a UCD .46 to be used with a Saito 72. This will be my first 3D plane so even though I've built many successful "box of sticks" kits, I'm just getting back into the hobby and 3D Planes are a new deal for me.

1) Is there a problem with the design of the UCD 46 that makes it more prone to flutter/less forgiving to construction problems?

2) I was considering using the Futaba 3004s that came with my 9C radio. Will those be adequate with proper construction and linkage techniques with the UCD? If not, will this plane work with anything short of the super expensive digital servos? I have a friend that is flying a Flip 3D with the 3004s and Saito 56. It works great. I figured the smaller UCD would work with them too.
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Old 08-12-2003, 02:11 PM
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chip581
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Default u can do 46 wing problem

i used hitec 422 deluxe on every thing and a 605 on the rudder and the servos never striped. the flutter mainly comes from the hole wing. the wing flaps like a bird. i will say that i would highly recommend not using the 2-56 rods that they incllude in the kit. I useds 4-40 rods.
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Old 08-12-2003, 02:17 PM
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Default u can do 46 wing problem

i truly am at a loss for words, ive seen many imac planes with small surfaces flutter more then mine, considering i have NEVER scene mine flutter. at one point i was spnining a 14x6 on my saito 91, and still no flutter.

i say buy it, if it flutter tell them and get a new one. and your servos are fine, make sure you either do a pull/pull on the rudder, or high torqeu
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Old 08-12-2003, 06:33 PM
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Default u can do 46 wing problem

Quote:
I was considering using the Futaba 3004s that came with my 9C radio.
I'm running those all around, except for the rudder (high torque TS-65) Never a hint of flutter in at least 30 flights so far.

As always, good servo practices apply. I used the supplied hardware except for heavy duty long futaba servo control arms.
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Old 08-12-2003, 07:48 PM
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Default linkages

I think the biggest point to make here is slop in the control linkages. I am running 3004's all around, and here's the important point: I have ZERO slop. I purchased CF pushrods from Central Hobbies, with the titanium ends, used MK horns and dubro metal clevises with the retainer clip. The ONLY slop in my system is in the gear train of the servos and as they're new, it's nothing. On the first 3 flights I was having a blast, but keeping it slow as I've not had a plane with control surfaces this large. One of our excellent pilots flew the heck out of it for a while and was very pleased. We got the thing up high, threw the throttle to full and ran a full pass down the field. Not an ounce or hint of flutter.

Couple of things to remember, just like on the big IMAC planes: All airplanes have a VNE - Velocity Never Exceed. The bigger the surfaces the lower the VNE. Have you ever seen a 35 or 40% Edge or Extra do a full power dive? No, because they'd shred their $6000 in short order. Have you seen the linkages they use? Very short control rods that are stiff and generally capped with ball links or hardcore clevises. The full scale EDGE 540 has a VNE of 265 mph!! That's a sleek plane that doesn't go very fast on purpose.

With all of the overpowering going on in these little planes I'm sure we're going to continue to see this problem. Remember, GP strongly warns against using greater than a 6" pitch prop on the plane, I think 6" pitch is too much myself. The guys with the big ole' engines really need to pay attention to that.

There's my $.02

J
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Old 08-12-2003, 11:07 PM
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Default Re: linkages

Quote:
Originally posted by maxim_jd


With all of the overpowering going on in these little planes I'm sure we're going to continue to see this problem. Remember, GP strongly warns against using greater than a 6" pitch prop on the plane, I think 6" pitch is too much myself. The guys with the big ole' engines really need to pay attention to that.

There's my $.02

J
OK, all the info about the size of the control surfaces and related speed as well as the linkage quality makes all kinds of sense to me. Now, with that last statement, I have to ask, is the Saito 72 too much motor? Should I drop back to the Saito 56?
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Old 08-12-2003, 11:08 PM
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Default u can do 46 wing problem

couldnt had said it any better.
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Old 08-12-2003, 11:36 PM
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Default u can do 46 wing problem

no i don't think that a 72 is to much because if u look at what happen to me and others i was at or below 1/2 throttle in straight and level flight each time it happened. a 56 would fly fine but i don't think that it would pull out of a hover very well, and the power differense between a saito 72 and a O.S. 70 is not really noticeable. The only reason that they recommend the O.S. 70 is because they are distributed by Great Planes. Saito is distributed by horizon, and thats why they recommend the Saito 72 for there Funtana 3D.
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Old 08-13-2003, 01:14 PM
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Default u can do 46 wing problem

This is why i ripped the covering off of mine, got rid of the rounded trailing edges on everything, glued the cracked ribs back together, soaked some thin ca here and there, CF laminate over the spars, reinforced all of the servo mounts, took as much dead balsa weight off as i could, got rid of dual elevator servos-2 carbon tubes mate the elevator halves now, going to use 3004 servos on the ailerons and 9202's on the ele/rudder, with central hobbies 4-40 CF pushronds mated to dubro HD long arms and robart super ball link control horns, O.S 70 supass1, 5 cell AAA rx pack, Sullivan 10 ounce tank centered with the needle valve. dubro pin hinges, glassed the firewall to the fuse sides. Hopefully i took off more weight than i added, got rid of 90% of the monokote over monokote over monokote, this thing had 7 ounces of monokote on it! i should be finishing it up by the end of august, ill let everyone know how it goes.


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Old 08-13-2003, 02:47 PM
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Default Looking for a few good men

Maybe one of you brave 3D cowboys would like to try a experiment . Remove the wing tips of your UCD 46 and let us know what you think. I have not seen anyone try this. I think it would be a worth while experiment. Who wiil be the first to step foward and earn the respect and adulation of his peers?
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Old 08-13-2003, 02:56 PM
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Default Saito 72

I think the 72 is a perfect powerplant. Plus it's as light as the OS 46FX with muffler with more torque... Just don't throw the 13x6 on it, I saw some people talking about using a 14x4w or something like that. Should pull the thing around great.

Dylwad, do you have any pics or drawings of the dual cf tubes on your elevator setup? That's a great idea.

BTW: Radio failure in the first UCD - sent it in. I think my PCM receiver failed. Lost control for a sec, said oh $%#$@, tried to bring it in on approach, but lost control about 30 ft out and up - went in at about a 45 degree angle. Fuse in half, but the wing wasn't too bad, already have it fixed. Just got #2 UCD, but will be rebuilding #1 over the winter.

J
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Old 08-13-2003, 05:03 PM
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Default u can do 46 wing problem

Quote:
Just don't throw the 13x6 on it, I saw some people talking about using a 14x4w or something like that.
It will fly great on a 13x6, just a little common sense like no full throttle dives into a full up elevator pullout... (I've got 30+ flights using that setup so far, no complaints other than maybe a little more right thrust needed in the mount...)
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Old 08-13-2003, 05:03 PM
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Default u can do 46 wing problem

ill take some pics when i get home of the elevator setup, its very stiff and probably weighs a half ounce or less. i thought about removing the wingtips, and extending the span so i wouldnt lose 2 inches of aileron and wing. as far as i know the main reason for having flat tips is the plane stops in the roll axis faster, and doesnt "hunt" like when doing point rolls. With not having flown one with or without the tips i begin to wonder how precise of a plane it is to begin with, and if chopping the tips would help enough to be worth it. Mabe someone will chime in on this.


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Old 08-13-2003, 07:07 PM
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Default 13x6

Hey rkramer,

While I agree that it would fly great with the 13x6, my understanding is that with a larger diameter, lower pitch prop you'll achieve two things: Slower top speeds, and more punch out of hovering type maneuvers (and better vertical). I guess it's like comparing it to shifting your car into a lower gear. I don't doubt that the Saito has plenty of power with the 13x6.


My little 46 swings a 12.25x3.75 and loves it. I'm messing around with mufflers, but I typically get 12000 to 12500 rpms = theoretically getting me about 9 lbs of thrust. (obviously real world is different) I'd love to have the Saito, but my little OS46FX will have to do for now...

Ok, last thing (long winded, sorry) Used thrustHP (can anyone remember where to get this software?) and compared two props for you:

With a 13x6 @ 10000 you get 8.57 lbs of thrust, pushing 56.82 mph
With a 14x4 @ 10000 you get almost 12 lbs of thrust, pushing the wind at only 37 mph

Based on that, I'd go with the 14x4 but I guess it depends on how the 72 likes them.

K, done now, sorry for writing so much...

J
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