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Old Jul 06, 2012, 07:21 PM
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United States, AZ, Tucson
Joined Nov 2010
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yup, But still relatively shallow. Maybe not even 20* nose up. Either way much less than Oleg, Jun, And most of the others you can see and study all over youtube.... I doubt My working on form at LOW "throttle" settings would be anywhere near close to the same stress the big guys put on planes...
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Old Jul 06, 2012, 07:26 PM
Registered User
United States, AZ, Tucson
Joined Nov 2010
4,001 Posts
Thanks Thomas. Hopefully the slump of anger and frustration will wear off soon so I can put this stupid thing back together....

In the mean time I am still very curious why it broke. As far as form and throwing power goes this throw was weak and actually very beautiful. Although I am "new" to dlg, my technique and form is much better, and MUCH MUCH more smooth than half the guys you see hackin these airframes into the air... Some of the launches are brutal! Being that I would LIKE to compete someday I have been working on form and finesse rather than brute force, which is why I am so dumbfounded by this wing failure....
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Old Jul 06, 2012, 07:27 PM
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United States, AZ, Tucson
Joined Nov 2010
4,001 Posts
In the mean time how much is a new wing? I imagine its most of the cost of the plane in the first place.....
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Old Jul 06, 2012, 08:01 PM
Registered User
Germantown, Maryland
Joined Apr 2004
4,501 Posts
My first guess is that it was a tip strike. EVRERYBODY denies that possibility the first time, or two times, or three times it happens. I saw (actually, only heard it, but saw the broken wing)a first time tip strike at The Bruce last weekend, and the pilot, of course, denied that it was a tip strike.

Your photos appear to show that the right wing LE was forced back as well as up and/or down. You can confirm (or deny) this by inspecting closely, the right flaperon root end. Does it look as if it was mashed up against the fixed tab at the center of the wing? Aerodynamic loads would have a hard time creasing the flaperon root end as seen in some of the photos. A folding wing that folded due to aero loads and inherent weekness, would crease the wing, but not the flaperon, in most cases. The right wing tip being stopped by the ground, would force that tip back as well as up and/or down, until the flaperon root end smashed into the center fixed tab of the wing. That would jam up the flaperon so it wouldn't want to operate properly and probably show some foam crushing at the contact points between the flaperon root and theh fixed center tab of the wing. I think that is the best way to answer your question as to what happened.

My best advice is to do nothing until you've had a chance to cool off and thinik. You should be able to repair that wing to just about as good as new, both structurally and cosmetically, if you take your time to get some advice and help with a cool head.

I would also say that if your enjoyment of DLG flying depends on always having a cosmetically perfect airplane that never breaks or even looks old with time and use, then you have picked the wrong pastime to get into. DLGs are subjected to brutal use and they often require repairs. You should plan on spending as much time learning to fix them as you spend learning to fly them.

Typically, the retail value of a wing is about half the cost of a full plane.
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Old Jul 06, 2012, 08:35 PM
a.k.a. Bob Parks
Glendale, AZ
Joined Jun 2008
2,205 Posts
Do Dbox / disser wings without center panel reinforcements really have enough strength at the center of the wing?

My Lighthawks and Vandal have at least three layers of kevlar out to where the servos would be installed.

BP
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Old Jul 06, 2012, 08:45 PM
Aurora Builder
United States, MD, Lusby
Joined Nov 2003
3,405 Posts
I've had a few wing failures, well, one wing failed twice, first time was structural, second may have been a tip strike. It really sucks but I will say repaired correctly the wing will fly like new again!

I'll second the notion to chill out, enjoy a beer etc. Repairing these planes is not a trivial task, best to do it when you are calm and thinking 110% clearly.

As to the repair, their are a few different ways to manage it. The critical thing is to keep the airfoil shape close to original. Best to pour boiling water over the wing carefully (so as not to damage the servos) and return the wing to near-original shape. In this particular case, I would not follow Thomas' original recommendation for a carbon patch, unless you have vaccuum equipment, and even then I'd still be very hesitant. It looks pretty clear to me that the crack went through the foam shear web in the wing. Thus, you should first inject epoxy to bond the shear web back together, should be a few grams at most. On the aft portion of the wing, you can also inject epoxy between the kevlar skin and the core. Let this cure overnight with some wax paper between the wing and the wing beds.

After getting the shear web back to shape, you could reinforce the area with a carbon patch on the 0-90 (so the fabric is mostly parallel to the wing root), but I would suggest a carbon rod of 0.060" or thicker diameter, at least 2-3" long, top and bottom. Slice through the skin into the foam, use the end of the rod to create a channel perpendicular to the root and ensure the rod can be fully embedded into the wing, but just the minimum needed to clear the surface. Then roll the rod in some laminating resin and glue it into the wing. After this is dry, I would smooth the entire area with some light spackle (http://www.amazon.com/12141-FastN-Sp.../dp/B0006MXS10). Finally, wrap the entire joint with a piece of fiberglass, use laminating resin, mylar if you have it, otherwise wax paper will probably be OK and put the wing back in the wing beds for a final overnight cure.

The reason for using carbon rods are they stronger than a single layer of carbon and not much, if any, heavier. They also serves to restore most of the shear capability the foam lost when it was split in 2. Finally, carbon rods and glass are easier to get smooth and lightweight than working with a 3k (5.7oz) carbon, at least in my experience.
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Old Jul 06, 2012, 09:15 PM
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United States, AZ, Tucson
Joined Nov 2010
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Well thanks for the input everyone!

I still have doubts of a wingstrike, although what you explain sounds pretty much identical.

The reason I say the is that a strike significant enough to do that much damage would certainly make noise considering it was over the dirt in a bssebsl diamond. Secondly my throws never get that low as that had always been s fear of mine, and if it did get that low it would have had the red dirt on it. (This dirt is nasty! It turns your shoes reddish orange and it doesn't come out! ) it has red marking on the tail where it has touched in the past, yet not the wing.

Now I'm not saying its nit possible, just that when recalling events it just doesn't sound Luke the experience. Although the damage does..... Not to mention I heard the crack befor the lowest part of the throw.. 360* was straight ahead, and I release at 20* the lowest point is around 120-140* and the crack started around the 220-200 degree mark, literally on the way down to the lowest point. However at this point it is more like shoulder level!

I'm curious if the twisting of my hand, ie changong the pitch of the plane to a more positive pitch in preperation for the upclimb/release it could have twisted right as it torqued and started the sling shot effect? However this sounds like it would have cased similar damage but on the left side.....
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Old Jul 06, 2012, 09:21 PM
G_T
Registered User
Joined Apr 2009
5,676 Posts
You shouldn't be twisting the plane with the hand at all. You can induce all sorts of damage that way. Plus, it won't launch as high. Just FYI.

The damage may have occurred initially on a previous throw, and then failed on the last one.

Gerald
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Old Jul 06, 2012, 09:23 PM
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United States, AZ, Tucson
Joined Nov 2010
4,001 Posts
Well when I say twisting I just mean changing the AOA on any throw that isn't a level circle. It should occure when ANYONE launches a plane at any other angle than straight and level
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Old Jul 06, 2012, 09:32 PM
Registered User
Congress, AZ
Joined Sep 2001
4,711 Posts
It looks like a pretty clean break. Just separate the wing and then do a wing join. No problem.

Is there any reinforcement at that part of the wing? It's usual to have a kevlar doubler go out at least past where the servos are.

There are a lot of better builders than I, but I'd always have a kevlar doubler past that location.

What is puzzling is that kevlar just doesn't break like that. At least in my experience.

Gary
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Old Jul 06, 2012, 10:28 PM
Registered User
United States, CA, Tehachapi
Joined Jun 2011
3,140 Posts
It sucks to have a plane break like that. FWIW I've never seen the wing with the throwing peg break on a launch. Ever. When wings fold it's in buckling, which is a type of compressive failure. The throwing wing is under a large tensile stress, and the opposite wing sees a large bending stress as it creates lift. That means the top skin is under compression. The point where the flap starts is the weakest point unless it's reinforced, so that's where failure most frequently occurs.
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Old Jul 06, 2012, 10:30 PM
hass-alfed and bass-ackwards
carlsoti's Avatar
United States, AZ, Chandler
Joined Jun 2008
5,278 Posts
Quote:
Originally Posted by Jwmflying14 View Post
Well when I say twisting I just mean changing the AOA on any throw that isn't a level circle. It should occure when ANYONE launches a plane at any other angle than straight and level
That's not entirely true. That would only happen if you try to change the plane of the swing while spinning. I did it a little when I was starting. It's a good habit to break soon, or you'll soon be breaking more planes.

If your radio can do it, you should program a momentary "launch" switch. Typically, this is a little bit of up elevator, and sometimes a little bit of down "snap flap" or camber. Frequently, a pilot will hold the momentary switch as they spin, then just a fraction of a second after letting go of the plane between level and about 20* up from the horizon. The plane will pitch up out of your hand. The difference of a few fractions of a second will determine the trajectory of the launch.

It's sounds kinda sketchy, but if your plane tracks straight out of your hand, as it should during the climbout after launch, you can start by adding the equivalent of one click up elevator trim to the momentary setting. Throw the plane a few times, and adjust as necessary.
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Old Jul 06, 2012, 11:02 PM
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United States, AZ, Tucson
Joined Nov 2010
4,001 Posts
Thanks for the replies guys.... I just did my best injecting resin. The foam was as expanded as possible and I used dermic needles. However it was extremely hard to get resin in there without thinning it. I hope I got enough in, but I could always thin resin and try again. Currently I'm just trying to get the skin to lay flat.
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Old Jul 06, 2012, 11:39 PM
Build something.
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United States, CT, Fairfield
Joined Mar 2012
665 Posts
This wasn't Kevin Costner's ball field by any chance? Maybe you struck one of the ghost players?

Yeah if it wasn't a tip strike or excessive aerodynamic forces then I'm thinking maybe you got a bum wing? Have you tried contacting the manufacturer? I know it'd be a hard sell to convince them it just broke for no good reason but it might be worth a try.

Chances are this'll be one of those annoying unsolved mysteries. If you can't get a replacement wing, best of luck with the repair.
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Old Jul 07, 2012, 04:16 PM
Yes..ok..maybe..lol.....
Tucson Avra Valley, Arizona, United States
Joined Jul 2004
5,712 Posts
Yes...................Tip Strike...............You won't see it..you won't feel it..and everyone denies it....hopefully we can fly together some day and I can observe your form................You certainly don't want to copy mine,lol....
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