Do I have a big problem here?
Posted: Wed Aug 14, 2024 9:52 am
by DWest
Working on installing the leading edge of the left wing here. The skin came out of the box with an extra bend in it on the bottom that I did I did not see when doing inventory. With the help of somebody that knows how to do metal work we were able to get the extra 1’ bend out with his 10 foot bending break and some massaging of the skin. As I’m pilot drilling the skins to the ribs for the bottom I noticed there are some divets? in between the ribs on a few areas. I understand when you’ve bend metal and then bend it back it has been stretched and possibly this is why I have some divets/slumps in some of these areas. It’s only under side of the wing. This is not the typical indentations around the ribs. It’s in between the ribs. First question is one is this a aerodynamic issue in which case I really need to fix the problem and two what are some ways that I can get rid of these divets?
The top was done first and updrilled before I even started the bottom side nightmare.
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 11:43 am
by Area 51%
Can’t speak to the aerodynamics issue, but I can tell you where the original “puckers” came from.
The leading-edge skins are terribly under-bent leaving the factory. If you try to bring the back edges together at a single point, they will oil-can and leave you with said “puckers”. Ask me how I know. I was never able to remove the dents to my satisfaction and ordered replacements. I used the already dented skin as a “tethered goat” and could repeat the oil-canning at will.
Vacuum-bagging the parts will make them less susceptible to the “pucker” and much easier to fit around the nose ribs. .
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 1:07 pm
by DWest
Well I did end up vacuum bending this one because I couldn’t get the holes to line up to the spar on the bottom side. Probably because of the added bend caused during shipping and because of the under bend that I am sure we can all agree with. After vacuum bending it, I didn’t even need straps to get clecos in the bottom holes! Just a push of the hand and things started lining up.
As for taking out the oil can flexing anyone have thoughts on how to “shrink” it to tighten things up? I saw somewhere that heating it and then applying ice could do the trick?
Also I may try removing all the clecos from the ribs to relax it and then put them back in to see if anything changes.
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 1:55 pm
by Bryan Cotton
I did not vacuum bag mine. What I did was to focus on the top - get that nice and tight, both during drilling, clecoing, and finally riveting. If you cleco the top, then flip it and do the bottom, is it any better?
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 2:55 pm
by DWest
I did that exact process Bryan. Did the top first and the bottom second based on what I read here. My right wing turned out pretty nice doing just that.
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 3:33 pm
by daleandee
Bryan Cotton wrote:I did not vacuum bag mine. What I did was to focus on the top - get that nice and tight, both during drilling, clecoing, and finally riveting. If you cleco the top, then flip it and do the bottom, is it any better?
Been a number of years ago but this is the method we used. There were boards and straps involved to pull everthing in place. The top was completed first and then the wing was flipped over & the bottom was finished.
Dale
3.0 Corvair/Tailwheel
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 9:21 pm
by sonex892.
I had a similar crease on one of the upper surfaces of the leading edge I only noticed after doing the vacuum forming so not sure if it was always there, or caused by the vacuuming. I spooned the crease out using the flat sonex spar bucking bar on the outside, and worked the metal from inside by rolling a table spoon and a rounded panel beaters bucking bar. The crease was totally unnoticable afterwards on a polished plane.
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 9:34 pm
by DWest
Yea the crease I can work out with the spoon I think. I am going to try the propane torch heat and then cold compressed air on the loose oil canny parts. Anyone have thoughts on that?
Re: Do I have a big problem here?
Posted: Wed Aug 14, 2024 9:38 pm
by Bryan Cotton
DWest wrote:Yea the crease I can work out with the spoon I think. I am going to try the propane torch heat and then cold compressed air on the loose oil canny parts. Anyone have thoughts on that?
A propane torch is hot enough to anneal 6061-T6. This is ok for fairings but I would not do it on structure. The skins are structure.
Re: Do I have a big problem here?
Posted: Thu Aug 15, 2024 1:03 am
by sonex892.
Bryan Cotton wrote:
DWest wrote:Yea the crease I can work out with the spoon I think. I am going to try the propane torch heat and then cold compressed air on the loose oil canny parts. Anyone have thoughts on that?
A propane torch is hot enough to anneal 6061-T6. This is ok for fairings but I would not do it on structure. The skins are structure.
Bryan’s advice is good. Please dont heat it
Re: Do I have a big problem here?
Posted: Thu Aug 15, 2024 11:44 am
by DWest
Interesting where this experimental build brings me. Did some research on 6061 t0-6 ductility and understanding of the process. Perhaps a heat gun and a cold wet rag might help? I don’t know what else to do at this point other than abandon it and get a new skin but then hopefully my holes will line up if not then, I’m in even more of a mess!
How ‘structural’ are we talking here? I mean we’re putting holes in the leading edge for pitot tubes and landing lights. Perhaps that’s my next topic of research, aeronautical structural design!
Re: Do I have a big problem here?
Posted: Thu Aug 15, 2024 12:58 pm
by Area 51%
DWest wrote:I don’t know what else to do at this point other than abandon it and get a new skin but then hopefully my holes will line up if not then, I’m in even more of a mess!
I had a leading-edge skin that was de-burred, dimpled, and ready to rivet. It got badly bent by a visitor that couldn’t keep control of his feet and it couldn’t be saved. I got a replacement with the same worries as you. All the holes lined up with the dimples falling into place perfectly.
CNC machines to the rescue.
Re: Do I have a big problem here?
Posted: Fri Aug 16, 2024 8:22 am
by DCASonex
The wing skins are VERY DEFINITELY structure. do not even think about using high heat on them.
David A.
Re: Do I have a big problem here?
Posted: Fri Aug 16, 2024 3:00 pm
by DWest
Thanks for all the insight everyone! I’m going to stick with rule #2 of my guiding principles of don’t cut corners/do it right. New skin on order.
I guess I will start making flaps and ailerons while I wait.