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N762C Wing overhaul project

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Casey
(@caseyleehutsongmail-com)
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Joined: 2 years ago
Posts: 23
Topic starter  

Warning! Long intro...

Well I figured I would document my wing project here. At the end of October I opened up my -3 for annual. Upon looking in the right wing my IA found some "swelling" in the rear spar (see attached pictures). We cringed a bit, but kept looking. Going to the left wing we found much worse. Exfoliation/separation of the spars witnessed in several lightening holes. My -3 has been metalized since 1956, so they likely haven't had any love since then. Looking further, we found exfo in both front spars, and the swelling in the right rear. Best we can tell, the left rear spar is still ok, but I'll know more when I get the wing off and open it up.

A little background: I bought the plane in November 2020. I knew off the bat the wings had surface corrosion, the previous owner did not try to hide anything. He had been treating it with corrosion-x for the last few years before I bought it, and I continued the same. As such, I got a good deal on the plane and took the leap to buy it. It has an IO-360, so that sweetened the deal.

I knew the corrosion would be an issue I'd have to deal with down the road, but I wasn't expecting it to progress so quickly. During my 2021 annual, the corrosion hadn't changed much and I thought it would be several years before I would have to do something drastic about it. That was probably more just wishful thinking as I couldn't bear the thought of not being able to fly it for several months while it is under repair. 

Anyway, back to now. Found the corrosion and knew this was a done deal. It's time to look for a set of wings, or maybe spars from Univair. After finding the corrosion on a Friday evening I waited the longest weekend ever to call Univair on Monday to see about options. Turns out they don't support the -3 wings. They sell complete -2 wings and all the individual pieces, but -3 spars are unheard of. I can only assume this is because of their different alloy being more prone to corrosion, but nobody I've been able to talk to at Univair has a clue. One gentleman I spoke with stated "maybe because there aren't as many -3's, so it isn't as beneficial to make them"? That's about the time my eyes glazed over and I found the quickest opportunity to get off the phone. 

A little more background, I am getting ready to move to OKC in March of next year, so that's just another piece of the puzzle I have to take into account. Obviously I want this thing flying as soon as possible, but certainly before we move, just to make things easier.

I wound up finding a project -3 on Barnstormers. Someone had completely disassembled their -3 in hopes of restoring it, but then sold it. The person who bought it held onto it for a few years with intentions of rebuilding it but never did, and eventually listed it for sale. So I drove from our home in Virginia Beach to Lafayette, Louisiana to pick it up. Before heading out there, I consulted with Eddie Stewart. He lives about an hour south of OKC and I thought he might know of somewhere I could store some of this project. I really didn't want to bring this frame and all associated pieces back to Virginia, just to have to move them back to OKC in 4 1/2 months. I got the idea that since I will be about 8 hours from OKC, I'll just drive there and drop off everything except the wings - assuming I can find some storage. After talking with Eddie, he and his wife, Amy were gracious enough to actually meet me in Louisiana and take back all of the stuff AND store it in his hangar until I move there. I was truly amazed at how helpful the Stinson community is and am very grateful that Eddie and his wife were so willing to help out in such a big way!

Fast forward to now, a few days after returning from Louisiana, and the "new" wings are in my garage. I am preparing to finish soda blasting them. Someone started to at some point and got mostly done, but there's a bit left to do. I want to soda blast them completely before moving into reassembly. Once reassembled, I will prime and epoxy prime before covering. The epoxy primer won't stop any of the exfoliation from happening, but it will keep any surface corrosion from happening, and it will certainly look like a clean job when all is said and done. 

If I am honest, this project is daunting! I am an A&P, but most of my experience is military aircraft. I foresee the hardest part being learning how to do certain things I haven't done before, like setting the drag wire tension, washout, fabric work, etc. Also, the Stinson community is great and there is lots of knowledgeable people out there and on this site. I intend to document the project here in this thread and would love any feedback/advice along the way. 


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

Corrosion


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

Same spar, different hole.


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

"new" wings


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

Wings in their current state - getting ready for soda blasting.


   
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Bret
 Bret
Trusted Member
Joined: 9 years ago
Posts: 61
 

Casey - thank you for documenting your project.  The information you share here will greatly help others in the future.

The Stinson community is a great support system.  Eddie and Amy's help is a tribute to how the Stinson family helps out.

I encourage you to take a bunch of photographs and video clips of the project and submit them to Randy Phillips.  I am sure he could create a video from the photographs and videos for the Stinson Tech channel.  

Hang in there Casey!  You will have a nice bird when you are done.

Bret C


   
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Will Ware (Webmaster ISC)
(@stinsono)
Reputable Member Admin
Joined: 4 years ago
Posts: 367
 

Great posts Casey, and its great to highlight these issues so people can learn what to look for. 

I need to clean my wings too (Rattle can brown) so Im interested in your “Soda Blaster” setup and how well it works. I know your wings are mostly done, but I will have to do ALL of mine. 

 

Will 

Dallas Texas


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

Not as much progress as I wanted this past week, but I got the soda blast equipment and made some makeshift wing stands (pics below). 

Being that I have a small amount to do, I decided not to invest too much into the soda blaster. I got a cheap gravity fed blaster that is capable of any type of media and has a control valve to meter the media flow rate. In function, it operates flawlessly. It takes quite a bit longer than I was anticipating, but it really has more to do with the nature of the soda being much less abrasive than sand or glass or some other synthetic media. There were some parts that the paint just came flying off, and others that I really had to sit and hit it for a prolonged period of time. I went through way more soda than I anticipated as well. I bought a 50lb bag and based on what I have completed I may need another bag or two. It's hard to give an idea of how much material a certain amount of soda can strip, but it sure takes a LOT of soda. Also be ready to be covered in soda. I wore a respirator and goggles, but just accept the fact that soda will be everywhere!

My 20 Gal compressor never shut off, and I spent a bunch of time refilling the (severely undersized) hopper for my blast gun. If you are doing a big job, try to source a big compressor. I also wouldn't use a gravity fed blast gun if I was doing a bigger job. They are really great for small things, but are limited by the hopper size. 

For the stands, I needed something I could roll in and out of my garage by myself. I took two pallets and put four casters under each one. Then from the bottom side of the pallet, I screwed in my saw horses. I then glued some foam to the top of the saw horses. While rolling, I bungee the wings to the saw horses and they move very easily. 

This week should be more productive!


   
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Casey
(@caseyleehutsongmail-com)
Eminent Member
Joined: 2 years ago
Posts: 23
Topic starter  

Wing stands. Nothing fancy at all, but they work.


   
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