1974 GCBC Restoration with Milman Spars

morgan

Active member
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Aug 24, 2018
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I thought I'd start a thread on my project since it might help someone in the future.

The backstory. Julie and I love airplanes. We currently have 2 gliders and a Glasair 2RG in the fleet. The Gliders are great fun and I put in thousands of miles of cross country flying in them each year, but they aren't point to point aircraft. The Glasair is a great commuter. 200mph on under 9gph. Fast and efficient, but also complex and for some reason doesn't feel like the kind of airplane you just hop into and knock around the pattern 10 or so times for fun.

Julie and I both got our tailwheel endorsements in Citabria's and they are a blast and something that was on our radar. Especially since you can add a towhook and use it for our own private towplane.

A neighboring hangar had a project Citabria in it. Over the period of a few years I saw a little bit of progress. Finally paint on the fuselage, but the wings were bare and hanging in the rafters. I asked the owner on a few occasions if he was looking for a partner. Not really. Then he mulled it over a few times. Then his business picked up and space went down and he bought a house and the projects were piling up. Julie nagged him a bit more about selling her the project. In March, he decided it was time to do a little hangar cleaning.

So we ended up with a 1974 GCBC. Mid time engine. The fuselage fabric and interior are done and immaculate. He took it down to bare metal and brought it all back. The kind of work that makes you smile when you look under the panel and see tidy laced electrical. Then I think about that level of quality and wonder if I can maintain it during the remainder of the build. As we moved box after box of parts to our hangar, the reality of the scope kind of hit hard. What did I get myself into?

The wings were already stripped and a previous, previous owner had started the Milman Spar conversion. So they looked like they were just a few steps from covering. But the spars weren't primed and the ribs weren't cleaned and ... So the guy we bought it from had completely disassembled the right wing. So I had piles of parts and the left wing to go off of as a guide.

Progress has been slow. A variety of things have got in the way during the spring and early summer. Lately I've been hammering away at it pretty hard. Trying to stop at the hangar for an hour or two on my way home from work. Progress has felt great the last couple of weeks with the right wing nearly back together.

I'll post a few pictures and try to keep this updated a bit.

Morgan

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ahhhh yes, the motivation that comes from other people's projects! Keep it going and keep the pics coming! Another unprimed set of spars.....you guys are making me kick myself for all of the time I wasted trying to prime mine only to see my hard work scratched to sh*t when the ribs were slid on! doh!

Is there much stress on that one gear leg with the one wing panel hung out there?
 
My spars are going back together primed. This is a before-ish shot when the right wing was still just a pile of parts. But I feel your pain on the scuffs of the freshly primed spar. I will add a few more pictures of the progress.

I don’t think the gear leg even notices the imbalance.
 
Thought I'd try to add a few photos from the timeline since getting the project.

Table built and parts laid out after initial cleaning.

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Cleaned all the old cloth and adhesive off the ribs. Deburred holes, addressed a few cracks and replaced the root rib that had some repairs I didn't like.
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grungy aileron bellcrank.

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Much nicer.
 
Finally got my spray booth set up at home. Using Stewarts paint system so the aluminum all gets cleaned with their EkoClean degreaser, then EkoEtch prior to priming with EkoPrime.IMG_6331.webp
Retaining wall/drying rack. Labrador for scale.


IMG_6333.webphanging and drying.
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Finished parts stacking up. A few must have been not quite dry as I did have one or two stick. Not a real problem, but could have been more patient. Also painting in 65 degree coastal weather makes for slow dry times.

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Cleaning and etching for the spars. No, I did not dry them with the propane torch. Separate task for that, unrelated to the Citabria.

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Spars set in place and used one internal rib to hold them upright. The problem with this approach was that the ribs should really be slid from the root to the tip. The taper of the tip distorts the I-Beam just enough that the outboard ribs scraped a lot. so I have some touch-up priming to do. Lesson learned for the Left wing.


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Coming together nicely. Tank ribs to go. I need to have fun with the damn root rib and trying to drill new holes since I bought a replacement root rib. locating and getting those in the right spot is going to be a challenge.

Next up are a the aileron hinges, bellcrank and the trailing edge cove.

Then it will be time to trammel and put in the final braces out near the tip. Maybe next week? Been wrapped up in some additional priming tasks that need to be done.
 

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What is that black bracket at the root? homemade for a rotisserie or part of the wing? Maybe that's a GCBC thing?
 
The GCBC has a root rib bracket inboard of the fuel tank bay.

Floats would be fun, but we are in California and we have more fire than water. Closest reservoir that can be landed on is about 100nm north of us. The ocean down here is not supportive of seaplane operations. Although we did have a 185 floatplane ditch off the coast after losing the engine. It flipped in the swell and sank. Both people on-board were rescued thankfully, but it's a rough ocean that we have.
 
A bit more progress the last couple of days.

Cleaned up the aileron bellcrank with a media blaster last week. Threw a coat of primer on it and the aileron hinges yesterday and got those reassembled and reinstalled on the wing. Slow and steady progress. The wing root rib is new and so I've got to finish locating and drilling the holes for it to attach to the root bracket.

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Been radio silent for a while it seems. The project is still coming along at a snails pace, but it looks like I will meet my deadline of all of the left wing parts primed by the end of the year. Assuming I get the spars primed tomorrow, that is.

The right wing is trammeled and ready for the leading edge to go on. The left wing came off the plane about a month ago and I tore it down pretty quickly over a couple of afternoons after work. Then starts the cleaning. So much cleaning... Lots of scotchbrite and elbow grease. This wing had much less adhesive on it left over from the old covering. That made the cleaning go a lot faster.

Just trying to keep making progress.

Milman Leading edges arrived in early December so I'm looking forward to getting that installation underway.
 

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Looks great reminded me of the erector set I had as as a young person, wife tells me I'm still a child just more expensive toys. The tear Down is the easy part all the preparation I think is most time consuming and then my problem is not having enough patience and making mistakes by rushing to get finished. Which always makes it take longer. The finished product is looking fantastic please post pictures of the fabric work as you go.
Bruce
Knoxville TN
 
Been a while since I have posted any updates.

I finished assembly of the left wing. Completely screwed myself by doing the one thing I had worried about and thought I checked against time and again. Ribs in the wrong position. Basically the GCBC has a couple of similar shaped ribs. The aileron and flap ribs are different, but only by about 1/4” if you aren’t paying close attention. I had paired up two ribs from the flap bay and slid them into place in the aileron bay. Put the aileron ribs in the flap bay. All of this looks pretty normal, especially once you have hinges in place and it breaks up the sight line down the trailing edge. Also making this mistake raise was the fact that most of the flap bay only had trailing edge stubs, it full ribs. And of course you install the stubs nearly last.

So I managed to get the wing 95% complete and discovered my error. Had to tear down to about 50% to swap the parts. About a day of effort lost. Sigh...

After fixing that I did manage to get a few other little items out of the way and get the wing trammeled and tensioned.

So I am finally starting the addition of the Millman leading edges and I have hit a bit of a question mark. I can’t get the underside of the ribs snug using the straps.

I think my root rib is just slightly out of plane with the rest of the ribs and is causing a little bit of interference. I have sent some pictures to Mike and I am awaiting feedback.

On mobile at the moment and can’t share pics right now. The new photo format on iOS doesn’t seem to be supported by the forum software.
 
Bob, I might try that. I am thinking it is less about the pressure exerted and more about some distortion. At least that is my current theory. This is in part due to the fact that if I crank down the strap over the #1 rib, the nose of the root rib gets distorted. I don't think I got a picture of that. I think that the root rib is just slightly different shape or position.

Unfortunately, I never saw this wing assembled with the old spars and Leading edge. So I don't know how it all looked originally. I'm just trying to get it perfect (or at least really close) before I start drilling holes.
 
Very nice, on drilling the old saying is measure twice in my case I study measure manny times then hope I get it right😬
 
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