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-   -   Wing structure question. (https://www.rcuniverse.com/forum/rc-jets-120/11690150-wing-structure-question.html)

Agrav8ed 05-09-2021 08:21 AM

Wing structure question.
 
I have a replacement composite wing for one of my jets. I happened to notice that there was a decent amount of movement along the whole top of the wing. When I borrowed a camera and scoped it, I can see about a 1/16 to a 1/8th inches gap between the lengthwise vertical wing structure and the skin. There is also asimilar gap between the wing ribs and the top skin. Even a couple in the front. Almost like the supports were a bit too short or not enough glue was used. This includes the landing gear area also and some point at the leading edge. This lack of attachment explains why the wing top skin is floating up and down so much.
Because this gap runs the length of the wing the majority of the supports I will not be able to reach to add additional glue. Is my understanding was that the top and bottom composite skin being attached to the vertical supports are what gave the wing its strength. Kind of like a engineered joist. So I am not sure how structurally sound this wing would be at 200mph or bank and yank turns. Nor do I want to unnecessariky risk my turbine and electronics. Therefore I am seeking the advise of some fellow builders. Do you guys think this wing will be safe?
Thanks
Agrav8ed.
https://cimg8.ibsrv.net/gimg/www.rcu...894eaf3c9d.jpg
This is the landing gear area. You can see a lack of glue and a large gap between the support and the wing skin.
https://cimg1.ibsrv.net/gimg/www.rcu...30f75a67ab.jpg
This is near the wing tip, as you can see, the top skin is still not attached
https://cimg9.ibsrv.net/gimg/www.rcu...eb5454f676.jpg
Gap between the wing skin and the lengthwise support.
https://cimg0.ibsrv.net/gimg/www.rcu...697033c30d.jpg
Gap between the vertical ribs, lengthwise support and the wing skin

tp777fo 05-09-2021 08:25 AM

What kit?

Agrav8ed 05-09-2021 09:33 AM


Originally Posted by tp777fo (Post 12677006)
What kit?

I did not want to mention which kit it is until I heard back from the manufacturer.
Thanks,
Agrav8ed

causeitflies 05-09-2021 09:45 AM

I would not trust it. If you can see movement on the ground imagine what it would do in the air.

jofunk 05-09-2021 11:32 AM

Contacting the manufacturer is the way to go. I think any reputable kit manufacturer would replace that in a heartbeat.

cetigershark 05-09-2021 01:08 PM

Hi Agrav8ed

good thing not to fly this wing. Both wing skins must bond with the internal structure. When you build a wing mold, tuning up the perfect internal structure takes a lot of time - trial and check and again and again - so that the fit is perfect and the gaps between skins and the structure are minimal.
I wonder what the manufacturer will tell you.
I received a SkyEmaster F-15 EDF 3 weeks ago. First thing I did was to check the internal wing structure with an endosocopic camera. It was flawless, however some other spots could have become some more building time;)

Agrav8ed 05-09-2021 01:51 PM

Yeah, I was questioning the structural integrity of the wing myself, hence my post. Without the top skin being bonded to make a cohesive structure, there is not alot of support for the internal structures or the bond with the bottom wing skin. It's good to know I was not overreacting.
Agrav8ed

crsetting 05-09-2021 03:45 PM

That wing should have never left the factory. !!

Jetpilot24 05-10-2021 02:59 AM

In the first picture it looks like it delaminated. In the next few looks like it was not a good fit. DON'T use that wing. It is not a matter of if it will come apart as apposed to it WILL come apart.
Hope the manufacturer steps up on the wing and sends you a properly built wing.
Just my 2 cents.

Joe

scoeroo 05-10-2021 03:44 AM

Is there a QA sticker & number on the structure ?

patf 05-10-2021 05:02 AM

At first i thought delamination, but when you look at the 2nd photo you posted, one side of the rib has a good contoured joint, so it looks to me like the rib and wing skin never made contact. Tough one to fix yourself, hope the mfgr makes it right for you with minimal waiting

Agrav8ed 05-10-2021 05:16 AM


Originally Posted by scoeroo (Post 12677135)
Is there a QA sticker & number on the structure ?

None that I noticed.


Originally Posted by patf (Post 12677147)
At first i thought delamination, but when you look at the 2nd photo you posted, one side of the rib has a good contoured joint, so it looks to me like the rib and wing skin never made contact. Tough one to fix yourself, hope the mfgr makes it right for you with minimal waiting

So do I. Due to Covid it took me around 10 months and a ton of shipping to get these. Now that the flying season is finally opening I can't use them. It's a bit frustrating.

I appreciate everyone replying and weing in with their opinions. I was not comfortable with the wing integrity and wanted to make sure I was not overreacting.

Agrav8ed

Dave Wilshere 05-10-2021 09:02 AM

I saw the same thing on a Krill 3m aerobatic model someone in my local club bought. They had skipped putting adhesive on all but the leading and trailing edge joint. It’s impossible to fix. They gave him new wings.

Agrav8ed 05-10-2021 09:57 AM

Just spoke to the manufacturer. They were very receptive to the issue and we are working on replacement options so it looks like things will be handled. I appreciate everyone's feed back.
Agrav8ed.

scoeroo 05-10-2021 11:42 AM

That wing is an accident waitin to happen -

T_CAT 05-10-2021 12:18 PM

I’d be curious to know the aircraft manufacturer also (not to bad mouth them), only to be informed to look out for issues if I either have or order the same aircraft. Mistakes happen, and all we can do is keep an eye out for any issues and notify the manufacturer for a resolution. I’m glad it sounds like this is working out for you and good for the company for stepping up to the plate when it matters.

Joseph Frost 05-11-2021 12:11 AM

Easy fix, rather than waiting for the replacement. Just fill it up with some ply bits and with the long brush fill in with epoxy or any bond agent, like gorilla glue, etc. Don't blame manufacturers, it is pilots responsibility to make sure the ARF models don't fall apart.
I have found similar problems with numerous ARF models over the years, I have covered few cavities and poured in pint of PVA , gave it a good gargel and shake, drained it out and let it dry, good as new, LOL.

cetigershark 05-11-2021 03:43 AM


Originally Posted by Joseph Frost (Post 12677282)
Don't blame manufacturers, it is pilots responsibility to make sure the ARF models don't fall apart.

Hi Joseph
Well, If I buy an ARF turbine jet ((kit) what it still is somehow) with composite wings, I expect the internal structure of the wing to be built correctly.

speedracerntrixie 05-11-2021 04:32 AM

To me it looks like the mold halves weren't fully closed. The lack of prep on the bond line is an issue as well.

Auburn02 05-11-2021 06:34 AM


Originally Posted by cetigershark (Post 12677294)
Hi Joseph
Well, If I buy an ARF turbine jet ((kit) what it still is somehow) with composite wings, I expect the internal structure of the wing to be built correctly.

Agreed - good on the owner to inspect the wings when he felt something was amiss, but that doesn't change the fact that the blame is 150% on the manufacturer here.

I just hope for his sake it doesn't take another 10 months to get the next replacement parts.

Skunkwrks 05-11-2021 10:39 AM

Like what happened to the Carf Extra 330XL when it had a flutter issue and it took quite a while for the replacement wings to arrive.

But Carf did fix the issue, the company does stand behind their product.


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