Hi all,

Unfortuneately, I crashed my DLG today on only my third time flying it. But I'm not sure what caused it. Here are the facts, any thoughts on the cause, or any unique repair hints are greatly appreciated.

I bought the plane used, it's about a year old. I first flew it last week, and it flew well. I was giving it medium strength tosses. Today at lunch I flew it for 15 minutes, launching it twice at medium strength tosses (the thermals were amazing). Then after work I took it out again, hand tossed it twice, then went to discus it. The plane made that horrible rapid thumping noise, like flutter, and instead of climbing, slowly arched over and drove into the ground and 30 feet in front of me and at about 40 degrees.

On inspection, we found this: the plane mostly ok. The top of the nose pod broken off a few inches back, the battery ejected, but the servo's still in place. That was expected, but here's what confused me: the wing seemed fine, except the right flaperon's (the side opposite the throwing peg) top skin had come completely off, just like you peeled it back. The foam was still attached to the bottom skin that was live-hinged to the rest of the wing from the root out to about where the control horn was located on the flaperon. Then pretty much the rest of the foam was attached to the top skin. The pictures were explain this best.

After the crash the rudder, elevatr, and both flap servo's were tested and found to be working just fine, no broken teeth, in fact it all still works just fine. The rudder and elevator are all solidily attached still and have no real slop in them. I was standing there with three other people, one of them a fellow R/C pilot, and all agree I didn't take off with the flaps down. And besides, I've done that before and it doesn't make the plane pitch down.

Their theory is that the top skin most have been lose to start with, and the launch ripped it back badly and the crash ripped it all the way off. I want to agree with this, because a) the skin is very cleanly ripped off the foam, and I don't see any epoxy residue still sticking to the foam, and b) the crash would force the flap down; I don't see what force could have possibly caused the skin on top of the flaperon to come off.

Let me know if you have any ideas or you've seen anything like this before. Thanks!

-Charles

My best guess is that the lamination/skin had started to 'part' fractionally from the foam on your flaperon. The speed of the launch with the wind assisting will have them subsequently peeled away the rest. The tearing up on the the mainwing would have been due to the "effective" massive down flaperon on the wing effect, pushing the flaperon surface violently up and causing the tear effects.

What I /do/ find interesting is that it looks like it happened on both front-corners of the flaperon, as apposed to just one.

I believe by the looks of it that the skin didn't go into the notched section of the hinge, this is a weak point for skin/foam bonding. To prevent this there should be either a thin layer of tape or other such skin going down into the hinge notch and over the exposed skin/foam bond.

Paul.

On further examination I'm going to speculate that the delamination started at the root, pulled off quite a bit of skin then the drag effect pulled it back along the length of the wing inwards again to the tip.

I'd say that the bond between the foam and skin had been degraded somehow, either due to an unfortunate/bad cure/bagging, or due to exposure/wear.

How long have you had the wing?

Scary and amazing. What wing is it? Spar looks like Taboo or Raptr, but planform does not, so I suppose it is some non-production wing?

As for repair - I would get some laminating resin, apply thin layer, blot most of it off, align the parts, perhaps secure them with some tape to avoid any misalginment, lay the wing down between two sheets of polyethylene or polypropyleen film, put it on a flat table and press it down using some weights. Thin layer of foam rubber between poly and weights would be good idea. Put some glass over the tear on them bottom - not sure about it put I would use two layers of 1.4oz or similar glass. Sand the skin under the glass patch.

regards,
Arne

Originally Posted by arneansper

...two sheets of polyethylene or polypropyleen film...

Is that the same as mylar? If not, what exactly is it, and where does one look to find it?

Thanks
-Charles

It's an ordinary plastic film. You can use mylar but then you must wax it, etc. And since the wing is already cured and in shape you do not gain much from mylar's stiffness that is required during initial bagging.

Advantage of the polyethyle and polypropylene is that epoxy does not stick to it and you do not have to wax it. Polyethylene has dull finish but polypropylene has very shiny finish.

Arne

Originally Posted by arneansper

What wing is it? Spar looks like Taboo or Raptr, but planform does not, so I suppose it is some non-production wing?

Yes, please can you tell us; was this a production wing? It looks like the inner section is non-tapered, but that may just be perspective. (The Raptr wing inner section is less strongly tapered than the TabooGT - they are not identical planforms - so maybe it's one of these, but on the other hand there would not be many Raptrs that old.)

Thanks
Hugh

Originally Posted by floquet

Yes, please can you tell us; was this a production wing? It looks like the inner section is non-tapered, but that may just be perspective. (The Raptr wing inner section is less strongly tapered than the TabooGT - they are not identical planforms - so maybe it's one of these, but on the other hand there would not be many Raptrs that old.)

Thanks
Hugh

I'll give you that's it not a custom build, at least not completely.

Actully, I think I'm going to abstain here, because the plane was in a fairly major crash before I bought it. A mid-air at a contest, and if I recall it nosed it pretty big time. In fact, I think it was one of those where the two planes tangled, and the pilot of this plane ended up following the wrong plane out of the tangle while this one went off on it's own, deadstick! Man, I dread having that happen to me. At any rate, there was wing damage along with fuse crumpling, etc,etc - the things you would expect for a nose-in. That being said, I don't want people to skim this thread and get an undue impression that I'm questioning the quality of the original build.

Additionally, I was at that contest, and I'm friends with the person who owned it for more than a year before he sold it to me. He's an aggresive, competitive pilot with super throws, and he's never had any problems with it. And I think he would have told me if he had since he was selling it to me and told me about anything he thought might be wrong with it.

I'm confident this wasn't an original quality problem. Now whether that crash had some lasting effects, that's a good question.

-Charles

Fair enough. I hope you are able to repair it OK; looks like it could come back together nicely. Good luck, let us know what happens.

Hugh

I would say that prior damage could have been a factor in the crash. If the flaperon skin was loose and air got under the loose skin during a high velocity launch then this could lead to the entire skin peeling off the flaperon. The plane would be expected to do some crazy, uncontrolled maneuvers during the time that the skin/flaperon parts were in the process of separating from the wing. The partially delaminated skin on the wing bottom that is visible in the pictures is typically what you see from the heavy impact of a crash and I suspect that that delam happened as a result of your recent crash.

The moral of the story is that you should look for loose skin (on any model) and fix it before doing any high speed launches. That would prevent the type of crash you experienced. Fortunately it looks like your model is fixable as explained earlier in this thread.

In keeping with everyone's wish to avoid having people skim this thread and get undue impresions; I'd like to point out that the wing in the pictures is clearly not a TabooGT. All production TabooGTs have the logo on the right wing and the tip shape is different.

In keeping with the thread title, "DLG detectives", a quick reading of the second to last paragraph of post 18 in this thread should give a big clue as to where this DLG came from.

I believe the appropriate statement here is "Case dismissed"!

Hugh

Originally Posted by Phil Barnes

In keeping with the thread title, "DLG detectives", a quick reading of the second to last paragraph of post 18 in this thread should give a big clue as to where this DLG came from.

What am I missing? What in that thread says what plane he was flying at the time of the crash? Clearly, it's not any great mystery what kind of plane it is, but I don't see how the link answer's that.

At any rate, I plan on attempting the repair this week sometime, so I'll let you guys know how it goes. I need a plane to fly at the BASS contest this upcoming weekend, I've already sent in my $30.

-Charles