RC Groups

RC Groups
    Hand Launch
        Discussion How Does This Happen??? :(

#1 Jwmflying14 Jul 06, 2012 06:24 PM

How Does This Happen??? :(
 
12 Attachment(s)
Well my TS2 Disser is about a week and a half old now. After a pretty darn clean, and well done build.

Recently I have been practicing good form, and today my wing almost snapped in half. In the middle of a 50-60% power throw (not even trying to thermal, literally WORKING ON FORM) and I hear a HUGE CRAAAAACK. First thing I did was look up at the plane (now about 70 feet high) and both wings were still there, So I decided it must have been the blade ripping out, not too big of a deal. Then I realized I had very little aileron input. I brought her down ASAP. Upon landing I looked over the plane and was shocked as there was no "instantly noticeable" damage. Then I started to look closer. My joint was okay... Everything looked good, so what could it be? and why doesn't my right aileron move? Then I found it. The wing delaminated on top and bottom, and I believe the foam is broken in half as well. The wing is now as flexable as a wet noodle, which is why I believe it is MORE than jst delaminated. Also if you look from the aileron hinge you can see what appears to be the start, or end, of a crack in the foam.


Now I have a couple questions.

WHY? I have not once had a landing where the wingtips hit the ground until it was at a DEAD stop. Most of my landing have been catches anyways.
The Pictures are hard to see but I will post them anyways...

How? I figured if it were to fail it would fail at a weak point like my joint, but sure enough it isnt my craftsmanship at all that failed....

What? Should I do about this? I mean I guess I can use a needle and inject the large crack with epoxy, then try to re adhere the skin to the foam... But why? Why the hell do I have to do that on a brand spankin new DLG?

No matter how cleanly I do this repair it will never be strong again, and it sure as hell wont have that new finish... Especially since the whole damn chord (all the way around) is rinkled and rippled.


These pictures dont do it justice, but here you go. Let me know if I need to circle or highlight the broken areas, but if you blow up the pic I believe its obvious... and of course you still cant tell the extent of the dammage as you aren't holding the Floppy noodle in your hand.

I am extremely Upset.... As I have treated this bird like my baby.... It would be one thing if it were something I did... But its not, at all....

Oh and before I forget, I am right handed, I throw with my right hand, and this happened on the right wing, not the left in which my peg is in....

#2 Jwmflying14 Jul 06, 2012 06:27 PM

Also, for higher res images, and larger images Press ctrl and then click the picture. This Should open it in a new window (on most browsers) allowing you to see the whole image.

#3 ThomasLee Jul 06, 2012 06:32 PM

Hi Justin,
My first instinct would be to say it looks like a tip strike to me....
Sorry to see a nice new plane damaged, never a good feeling!
Good thing is if repaired correctly, it WILL be strong and you may not even notice any difference when flying :)
Pour boiling water over the creased area (or, since it's near servos, maybe a better solution will be to place a wet towel over the area and iron it with a clothes iron set to 'nylon' or 'silk'), and allow the foam to come back out to the original shape. Rub in or inject some laminating epoxy, and weigh the parts down.

Thomas

#4 Jwmflying14 Jul 06, 2012 06:37 PM

4 Attachment(s)
See, Clean wing tips, not a nick on em! This plane has never hit ANYTHING with impact!

Thomas, thanks for your input. Definitely not a tip strike AT ALL. The wing tips have never touched the ground, in flight, on landing, or on a throw. The cleanliness should show that pretty darn well.

These have not been "fixed up" or cleaned what so ever. Everything you see is EXACTLY from the field when this all happened about 35-40 minutes ago.

#5 GaryO Jul 06, 2012 06:41 PM

I can't quite tell which wing half failed. The peg side or the other side?

Tip strikes, IMHO, usually have a different kind of damage. And it's hard to visualize how the cf and the kevlar could shear. Loaded during throw? Do you throw up or use elevator preset to rotate?

Gary

#6 gopherhunter Jul 06, 2012 06:43 PM

Was it windy?

#7 ThomasLee Jul 06, 2012 06:43 PM

Hi Justin,
Although I'm not saying it 'has' to be a tip strike, I've found that quite often with a Dbox wing or other wings with lots of carbon at the LE, you may not find any nicks. You definitely won't feel the tipstrike though, I've tip-striked twice, first time I had no idea what when wrong, and simply thought it was badly built. Second time I was a bit more aware, and realized what I was doing wrong.
There really isn't many other ways a wing can fail like that I can think of, especially if properly taken care of as you did.
Hope someone with more experience can chime in!

Thomas

#8 ThomasLee Jul 06, 2012 06:44 PM

Quote:

Originally Posted by Jwmflying14 (Post 22093721)
See, Clean wing tips, not a nick on em! This plane has never hit ANYTHING with impact!

Thomas, thanks for your input. Definitely not a tip strike AT ALL. The wing tips have never touched the ground, in flight, on landing, or on a throw. The cleanliness should show that pretty darn well.

These have not been "fixed up" or cleaned what so ever. Everything you see is EXACTLY from the field when this all happened about 35-40 minutes ago.

From photos, seems like he is a righty, blade seems to be on the left wing and damage on the right wing.

#9 rcgeorge Jul 06, 2012 06:50 PM

What is TS2 Disser never herd of that plane.

#10 Jwmflying14 Jul 06, 2012 06:53 PM

Where I was flying today there was about a 5mph head wind. I tend to throw approximately 20* up. I know for a fact It wasn't a tip strike As I throw from the dirt on a baseball diamond, which make a very distinct noise. Secondly The form I have been working on doesn't bring the tip within 16-18 inches of the ground. The ground is specifically why I am not throwing at 25-30*

As for Preset I Have about 2mm up on spoilers/flaps and Very very little up elevator. Not enough for it to over G.

Not to mention the noise started about 200* from when I threw it Right when acceleration really starts to build (yet still not much, as this was a LOW energy throw. and I was working on form). It was Right after that point of no return in the throw....

Gary, My throwing peg is on my left wing (I am right handed) and the damage occurred on the Right wing just past the joint reinforcement.

Personally I am 100% positive It was not a tip strike. not only have I seen the damage from tip strikes, But I am 100% in the throw that it did not touch the ground at all. Again, i was working on form, not doing anything stupid or new. Just being "smooth". That Is why I am so stumped as to why this happened. Also if you look in picture #1 you can clearly see a huge crack in foam, which i can only assume follows the whole line of damage.... The reason I think this is beyond just injecting with resin is because of how much of a floppy noodle it currently is... It feels like NOTHING is there....

#11 Jwmflying14 Jul 06, 2012 06:53 PM

Quote:

Originally Posted by rcgeorge (Post 22093807)
What is TS2 Disser never herd of that plane.


Topsky 2 Disser

#12 ThomasLee Jul 06, 2012 07:02 PM

The foam being cracked is no problem as long as it is still shaped correctly (after the hot water/steam methods), the laminating epoxy will hold it back together, and the foam is not a ver structural material to start with along the length of the wing. If the spar is broken, then that's a bit more problematic. If needed, laminate a layer of 3K carbon both top and bottom at 90 degrees (no bias), and it will be stiffer than original.

Hope you figure out what went wrong so it doesn't happen again in the future! :)

#13 Jwmflying14 Jul 06, 2012 07:07 PM

Quote:

Originally Posted by ThomasLee (Post 22093911)
The foam being cracked is no problem as long as it is still shaped correctly (after the hot water/steam methods), the laminating epoxy will hold it back together, and the foam is not a ver structural material to start with along the length of the wing. If the spar is broken, then that's a bit more problematic. If needed, laminate a layer of 3K carbon both top and bottom at 90 degrees (no bias), and it will be stiffer than original.

Hope you figure out what went wrong so it doesn't happen again in the future! :)

Thanks for your input... as soon as I can find hypodermic needles I will start the repair. I am 95% positive the spar is broken as the damage is ALL the way around the wing top and bottom.....

100% truthfully I believe there was something internally that caused it... I see nothing else that would have done it.

When you say add carbon top and bottom 90* do you mean parallel with the leading edge? 90* away from the pod and boom? this would only make sense to me... But get ready for an ugly plane.... What a bummer.

#14 xwingnut Jul 06, 2012 07:12 PM

You've given some key information:
"Recently I have been practicing good form. I tend to throw approximately 20* up." and "The ground is specifically why I am not throwing at 25-30*"

Throwing at any angle off from level induces undesired loads. Some much larger than one would think. Induce those loads and they can and will eventually transform into something you don't want to see happen. You mentioned this happened during launch, right?

#15 ThomasLee Jul 06, 2012 07:21 PM

Hi Justin,
I would do it 90 degrees along the length of the wing.
We've make a couple wings like that, 3K dbox at 90 degrees without any spars and they're stiff as a rock, just doesn't look very 'refined'.
Now that there's battle scars you'll fly it without worry and get way better, right? :)

Ken, yeap, there's definitely a lot of loads on DLGs and many other sailplanes don't see. I'm very interested in seeing how this one turns out and see why it failed.

Thomas


All times are GMT -5. The time now is 06:07 PM.