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  #1  
Old 08-15-2022, 10:48 AM
RV8 Builder 84943 RV8 Builder 84943 is offline
 
Join Date: Jan 2021
Location: Enid, OK
Posts: 14
Default RV8 Rudder Skin Pillowing/Movement

Hi All. I just bent my rudder skin, and that went well, with only minor adjustments needed. After clecoing on the skin to the skeleton, I have noticed that there is some slight movement in the skin. It's basically like there's slightly too much material between the top and bottom; along the vertical axis. If I apply light pressure to one area of the skin, it will pop down and the adjacent section will pop up. Mind you, this movement is very slight, yet unexpected.

Is this something I should be concerned about, or is it normal to have a little movement in the skin?

My radius looks very nice, and I can't find any significant issues with the bend. A Straight edge lays nicely flush perpendicular to the bend all the way to the radius. The only tiny variance occurs towards the bottom in the area of play, but hard to tell what's going on because it moves.

The issue seems more related to the amount of metal between the top and bottom ribs, and that's not something I can't change. Any thoughts on what the cause is? Has anyone else had this occur?

I'll try to capture it on a video if that's not clear.
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  #2  
Old 08-15-2022, 11:10 AM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: KAJO
Posts: 934
Default

You need to post a picture of two so we can see what you see.

The skin will never going to be perfectly flat like a raw sheet stock after you rivet the ribs . Looking at the finish skin with reflected light, it will highlight every imperfection from the perfectly flat surface. Take this picture and post it.

Mine has slight bow between the ribs. The wings also has the slight bow between the ribs, when seen looking at the reflected light. The oil-canning is opposite to bowing and it is undesirable for cosmetic purpose but I don't think it affects the strength. Based on your description, you may have oil-canning but I am guessing without pictures.

The sheet metal on the fuselage between the various stiffening ribs and frames also show slight bows when looking at reflected light. It will be less apparent after you paint.
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RV8 (N38PV): 90% completed (90% to go)
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  #3  
Old 08-15-2022, 11:30 AM
RV8 Builder 84943 RV8 Builder 84943 is offline
 
Join Date: Jan 2021
Location: Enid, OK
Posts: 14
Default RV8 Rudder Skin Movement

Ok. I took a video, but now I have to figure out how to share that on here.
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  #4  
Old 08-15-2022, 12:12 PM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: KAJO
Posts: 934
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Try the manage attachment. If it doesn't work then post it to Youtube and send us the link. You can create a YT channel with your Google account for free.
__________________
RV8 (N38PV): 90% completed (90% to go)
Days to Final Installation: 999
Days to AWC: 999
Days to First Flight: 999
Painting: 99% completed
Donation paid through 2022
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  #5  
Old 08-15-2022, 12:22 PM
RV8 Builder 84943 RV8 Builder 84943 is offline
 
Join Date: Jan 2021
Location: Enid, OK
Posts: 14
Default Rudder Skin Movement Video Link

https://youtu.be/k8lBWdtI_ec
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  #6  
Old 08-15-2022, 12:32 PM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: KAJO
Posts: 934
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The rudder skin only has the stiffeners instead of a full rib (other than the end ribs). I have to check my rudder when I get home tonight and let you know.
__________________
RV8 (N38PV): 90% completed (90% to go)
Days to Final Installation: 999
Days to AWC: 999
Days to First Flight: 999
Painting: 99% completed
Donation paid through 2022
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  #7  
Old 08-15-2022, 07:24 PM
PhatRV PhatRV is offline
 
Join Date: Mar 2018
Location: KAJO
Posts: 934
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I just checked my rudder and the skin is tight as a drum. The leading edge of your rudder isn't curved and is not riveted yet. This will add a good deal of torsional stiffness to the entire structure and I suspect the flexy skin is from non closed structure.

I didn't check the rudder skin as closely as you did. Give Vans support a call and ask them.
__________________
RV8 (N38PV): 90% completed (90% to go)
Days to Final Installation: 999
Days to AWC: 999
Days to First Flight: 999
Painting: 99% completed
Donation paid through 2022
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  #8  
Old 08-19-2022, 09:38 AM
RV8 Builder 84943 RV8 Builder 84943 is offline
 
Join Date: Jan 2021
Location: Enid, OK
Posts: 14
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Well first of all, I learned what the term "oil canning" means. Lol. I did reach out to Vans, and he said welcome to oil canning 101 class. He said it's a completely normal part of working with these kind of materials and to build on. Shows you how new I am to all this and how much I have to learn.

I'm still keeping my fingers crossed that some of the oil canning is tightened up once the part is riveted, rolled, and closed. We shall see. I'm waiting on a vice grip dimpler tool to arrive, to finish dimpling some of those hard to reach rib/skin trailing edges before I can move on, but hoping for the best.
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