WARNING - Goldwing Sbach 342 89inch carbon version
 

Hi guys, I want to warn you from Goldwing Sbach 342 89inch carbon version electric.

Take a look what happened to the plane on 15th flight during horizontal flight with ¾ throttle. I wasn’t expecting superb quality from Goldwing but I wasn’t expecting sh*t construction either.

Summary: damaged both wings, shattered balsa ribs, cracked both structure beams, damaged aileron servos, pulled out hinges, carbon tube separated from glue, broken ribs in ailerons etc. Fortunately nobody was hurt. I managed to land safely despite of damaged both aileron servos but it could’ve ended much worse. :mad:

Goldwing refused any responsibility, not even apologize for inconvenience and offered me new wings for full price. Unbelievable.

Goldwing never ever again :mad:

Sorry for the issue, and glad to see you got it down relatively safely.

Just a thought here. Not sticking up for Goldwing, nor am I going to slam them. I'm struggling with the idea a plane could do that much damage to 1 wing in level flight at 3/4 throttle unless there was some aileron flutter involved at some point in time. Whether that occurred on a prior flight or in the flight just prior to you noticing something wasn't right prior to the wing folding or something. How/why that occurred would be at the top of my list of things to check out after seeing these pics.....

What caused the red flag to go up indicating it was time to land right now?

I agree that the damage that I see in your pictures was a result of flutter. The wing structure is very light however the damage pictured is not a result of flight loads. Do you have a picture of your aileron linkage setup and may I ask what servos were used? Not much we can do to help your situation now but may be able to prevent the same thing happening in the future.

Sorry for delay. This is direct result of 3 or 4 seconds long lasting flutter. The wings was not damaged prior to the flutter. It was brand new plane flown with ease.

Aileron servos: Hitec HS-8335SH with 2S LiFe battery (18.5 Kg/cm at 6V; 0,16s/60degree at 6V).

Ailerons went crazy during flutter but I dont remember what happened in the first place, flutter on ailerons caused flutter of wings or other way around.

I will post pictures once I got home :)

I would suggest your focus be placed on the cause of the flutter vs. how the wing is built. If the aileron had not fluttered, the wing would be fine. I doubt many will place blame on the servos, but without more details/pictures it's really difficult to be of much more help.

3 to 4 seconds of aileron flutter is more than enough time to blow the entire wing off the wing tube, looks like they manufactured a strong for you seeing how you were able to get it back on the ground in one piece.

Bob

Servo instalation (of course there were and will be 4 screws). Linkage and servo clearance almost nothing.

http://www.rcuniverse.com/forum/atta...mentid=2209288http://www.rcuniverse.com/forum/atta...mentid=2209289http://www.rcuniverse.com/forum/atta...mentid=2209290

Check out the shearweb on the left hand from the cracks and on the right hand from the cracks. Why they decided to cut away so much material from shearweb? Why they decided to choose so fu*ked up pattern and jeopardize structural rigidity for sake of what, saved few dozens grams? Wood which would end up in trash anyway.


I'm sure customers wouldn't mind to fly with slightly heavier plane for sake of rigid wings. I wouldn't mind, I would appreciate it.


Had they not cut away material from shearweb and had they used shearweb for full lenght of the wing the wing would be fine and I would not have to fix it. Not to mention I lost trust in this plane.


I did not post this thread to cry over spilled milk nor to get your sympathy. I just want to warn people what is behind the oracover and what may happen. Somebody could've been hurt.

I will fix it, then I will seal open D-box for full lenght of the wing and then I will reinforce it with shearweb for full lenght of the wing as it should've been done in the first place.



http://www.rcuniverse.com/forum/atta...mentid=2209327http://www.rcuniverse.com/forum/atta...mentid=2209326

What I see here is 60 degrees of servo rotation

Aileron servos: Hitec HS-8335SH with 2S LiFe battery (18.5 Kg/cm at 6V; 0,16s/60degree at 6V)

What I see in this picture are waaaay to long servo arms. Which = mechanical disadvantage

http://www.rcuniverse.com/forum/atta...909064&thumb=1

Now I start wondering the throws set up? High rates = ? degrees. Low rates =? degrees. What end point adjustment were you using.

In my experience aerobatic flying requires about 20* up and 20* down. 3D only requires another 10* on the ailerons. The elevators 45 or more and the same for the rudder.

It looks like you are throwing servo power and accuracy away for unnecessary throw.

My servo horns are typically shorter on the aileron servo than on the aileron itself. During setup I also always raise the end point to 120% or 140% depending on the radio (what ever max is), and start there with setup.

I love ARF's, but, glue is profit! When I start going over a new plane like this I assume they shorted the glue. I drip 50/50 epoxy / 100% denatured alcohol mixed and put in an old CA bottle every place I can reach. I call this "Taking Ownership". The plane is now mine and my responsibility. I also use trimsolvent on all the covering edges.

I am sorry about your loss.

And these are just MHO's. Of course I agree they should at the very least offer you some 50% discounted wings.

The linkage geometry was the cause of failure.

To build a wing that will resist the effects of flutter is kinda like attempting to build a crash resistant plane. You quickly outweigh any advantages gained with extra strength with extra mass, which only contributes to the devastation on impact. Goldwing builds extremely light weight air frames - that are not designed to be forgiving when things go wrong. There are much heavier designs available if that's what you're looking for.

Agree with kmeyers. The linkage setup does not offer the full strength/flutter resistance that might be available from your servos. Even if it were not for that, servo resolution suffers as well. For instance, if you had used the hole in the aileron horn furthest from the control surface (as in one of the 3 pics you show), and maybe came in a hole or 2 on the servo arm, my bet is you would have the same amount of control surface throw, with much better servo resolution, and a big increase in servo strength/flutter resistance. In other words, you need to use maximum servo rotation available to move the control surface the amount you want (on high rates). To set up linkage like you show, you end up with way to much throw, which you then must cut back using end point adjustments - that's a bad plan!

The more I stripped the wings down the more I realize how poorly its glued together with goldwing glue-like goo. Cant believe how their QA could release it.

Anyway, I would recommend to the owners to stip down the foil and reinforce it with high quality glue.....

Many aircraft are built with what seems like an inadequate amount of glue when in reality not much glue is needed in the first place. The airframe probably was fine but mechanical disadvantage on the ailerons are most likely what caused them to flutter and rip the wings apart. Some other notes to take away:

1. I never recommend the use of anything but an aluminum arm on the servo on an aircraft this size (gas or electric). The arms you have on there now, coupled with mechanical disadvantage, would eventually lead to the plastic arm failing and/or the screws pulling out from the arm extension. Use a high quality aluminum long arm like SWB 1.5" arms.

2. Putting the control linkage that close to the control surface on the control horn gives you more throw but forces the servo to have to work harder and can lead to an overly sensitive airplane. My recommendation is always to use the control horn hole that is furthest out from the airplane. This will give you the best mechanical advantage and keep the setup tight and rock solid.

There is a carbon fibre rod along each beams in wing, approx 1 meter long, going from the root of wing to the tip of wing. All rods are loosen a unglued from root to the tip due to the ****ty glue-like goo. I can literally peel off the glue remains from spruce beams......

That and the damage you previously posted is secondary damage caused by the massive amount of vibration created by aileron flutter. Flutter is very destructive, I have even seen composite wings come apart when flutter happens. I just don't know how many times it has to be said before you will listen. Your aileron linkage setup was done poorly and is the cause of the flutter. The flutter caused the damage.

No doubt about the cause of flutter - aileron linkage. I just wanted to point out the lightweight construction and more importantly the ****ty "glue" they used all over the plane...

I do agree that ARFs are constructed poorly. That's why I don't own any wood ARF airplanes. The only way to avoid that crap is to either build it yourself or buy an all composite airplane.

I will respectfully disagree as not all ARF's are constructed poorly. This is why it pays to be selective with the brands you purchase.

No worries, we all have our viewpoints. I'm not saying they couldn't build a quality airplane and I will agree that some do much better then others but the market drives the quality via price point. If the average guy was willing to pay the price for top quality then quality across the board with all manufacturers would come up. Ever notice after getting your brand new wood ARF that your shop has that wonderful fresh cut wood smell? That's the wood used to build your airplane drying out.

Hinges?
 

Greetings from Finland
This is not my best expertice, but have you checked the hinges of ailerons? If they are loose or, too soft material or they can move up and down in their slots. I think that they also can cause flutter. And one reason can be that aileron material by it self is too soft.

Old Erkki

Why only two screws to hold the ailerons in? I agree servo arm is way to long, and you had it on the lowest hole on the control horn all lead to lots of slop, and mechanical advantage from the aileron to the servo. So over all to high of speed with a poor setup on the servo to aileron.

Two screws just for illustration purpose. Always I'm flying with 4 screws.

Am i the only one that sees that the servo eyelets are mounted upside down? Makes for a loose servo mount because it cuts into the ply.