N762C Wing overhaul project
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.
Same spar, different hole.
Wings in their current state - getting ready for soda blasting.
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.
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.
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!
Wing stands. Nothing fancy at all, but they work.
Hello, my name is Danny Hogan and I live in Poteau, Oklahoma. I have some Stinson wings and spars. One left and right, several lefts in various stages of disrepair. I also have spar sets. Not being a Stinson guy I couldn't tell you what they fit exactly, but the guy I got them from was restoring a -3 possibly. If you would like to have this collection of parts, no cost, let me know.
Hey Danny, I actually would love them. Call or email when you can. 757-277-6254. Caseyleehutson@gmail.com
I wish I had something major to update on the wing build, but I only have a few small things. I guess that's how these things go...small victories.
I made much less progress than I was hoping for over the holidays. Traveling to see family is always worth it, but it was tough to leave when I had this major project looming.
Just before the holidays I got the old wings removed and brought home so I could work on de-skinning them after the new year. Knowing I was short a few parts for the new wings I spent some time de-skinning the wings after the new year. Sadly, the corrosion has hit pretty much every piece on the wings. Some it is very light, and actually the wingtips are free of corrosion, but the parts I needed were bad enough that I didn't want to mess with it. I figured by the time I sanded the corrosion out of it there wouldn't be much material left. Plus, even if it was light corrosion but I don't successfully stop the corrosion process, I just created a headache for the next guy (or maybe me) who has to redo the fabric down the road. Or worse, it becomes an issue sooner than later and I have to deal with it after doing all this work - not worth it!
I did find a very quick way to de-skin the big panels off the wing using a sanding wheel on a grinder. I didn't use it for any leading edge skins or wingtips - basically anything I thought would be worth something as this sanding wheel sands FAST. Rivet heads didn't stand a chance.
After figuring out that very little could be salvaged from the wings, I moved back to soda blasting. I want to reiterate from above that if you are spearheading a soda blasting project for something like wings or anything bigger than hand-sized parts, buy a big compressor. My 20 gal putting out 4 CFM just didn't cut it. I tried a few makeshift things like combining another small compressor and running them in parallel. While that helped to extend the time I could use the blaster before depleting the air, it was only slightly. After a couple days of my compressor running for hours doing this, it quit. After a quick assessment I think it's just the motor's output shaft bearing, but it was making BAD noises and shut off on its own.
It was really a blessing in disguise because I needed a bigger compressor to paint the wings anyways. In fact, I had been pondering what I was going to do, and was considering one of those Citation units with two turbines (one for spray gun, one for supplied air). They seem like really great units. After reading the Stewart Systems manual, I found where they specifically suggest not to use one. After talking to some Stewart Systems guys, it seems they just haven't had any good experiences with them using their system. The manual also called out for a 13 CFM compressor, so that sealed the deal for me on getting a compressor. After searching for a bit I found a screaming deal on a much larger compressor than I need (7.5HP 80 Gal 24CFM). When I got it home and my wife saw it, her reaction was priceless. She just assumed it would look something like my old 20 gallon. It probably wasn't the best time to buy a 500lb compressor, but I *needed* it for the project. In reality, this will likely serve me well for many years and I can't imagine a situation where I would need more air than this thing can provide. I've only ran it for about 30 minutes, but it can provide more air than the soda blaster can use. And surprisingly enough, it's a LOT quieter than my old oilless compressor. I should have gone to an oil lube compressor long ago!
Anyway, the wing is close to done and I am working on individual components now (bellcranks, etc). Speaking of bellcranks, I ran into a bearing issue. Univair doesn't have any stock of the Aileron/Flap Bellcrank bearings, P/N: 452-342. They even called all their suppliers and nobody had any. The guy actually asked me if I had tried a bearing shop. I chuckled at first....but wound up going to a bearing shop the next day. After measuring the bearing I supplied, they came up with P/N: 31702-01. They had to order it so I will see it they are identical when they arrive. They sold them for a very fair $5 a piece (same as univair).
My order for Stewart Systems is in! I will be doing a double cover process. I first learned of it watching some videos that John Hansen did. Actually, I guess I first learned of it watching Mike Patey build Scrappy. He did his control surfaces in fabric and double covered. Anyway, John is a supplier of Stewart Systems and a Stinson guy as well. Stewart Systems is matching a shade of brown I sent them from my plane and that should be ready in a couple weeks - probably much sooner than I will need it. Still need to source a few parts, but I am looking forward to getting some epoxy prime on the wings!
Just a heads up in case someone is reading this and needs bellcrank bearings. The above mentioned P/N does not work. Do not use P/N: 31702-01. The picture below shows the issue. The right bearing is the correct piper bearing. The left bearing won't work due to the "hat" being taller in relation to the shelf. with both installed in the bellcrank it won't fit into the bracket on the wing.
I put a couple of the old crusty bearings in an ultrasonic cleaner with Hoppes #9 cleaner for a few minutes and they came out looking brand new. If I can get the rest of them this clean and they are still tight I might not need new bearings.
Could you grind down the “Hat” on the $5 bearing?
Also could you explain a bit more about the ultrasonic cleaner you used? That sounds cool.
I probably could grind the hat, but if you notice in the picture, the body of the bearing is shorter as well. Doesn't affect the function, I just don't love it. The ultrasonic cleaner did such a good job I'm not sure I am interested in changing them unless I found more of the correct bearing. Here's a link to the ultrasonic bath I bought:
The ultrasonic part is what really does the work to clean, but I put Hoppes #9 gun cleaner in it. It is pretty magical, in about 2-5 minutes whatever you put in there is completely stripped of any gunk. I'll do before and after pics of the next bearing I put in there.