Project 5 build thread

[alexM]

I've learned that a feature of this forum is that you can't come back later and edit a post to add pics.
Since all my pics are taken with my phone and typing significant content isn't phone friendly I will post some pics now and then do another post with a real keyboard
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[alexM]

Okay the explanation of the above. First picture is the gussets I made from 0.032" 4130 that I ordered from Aircraft Spruce. I didn't do very careful math and ended up making 16 when I needed 8, so I'm giving the other set to Eric (reference his barn find thread here in the builders section).

In the second picture you can see one of rudder pedal sections after the welding was complete. I had intended to completely disassemble the pedals to avoid getting those plastic bushings hot and blew it. Later on when operated the pedals I found increased friction and thought that was the problem. Well it wasn't, and a lot of you already know what happened: The tube at the base of the T isn't straight after you weld on the gussets.

I read through a thread on rudder pedal friction and found where people fixated on grinding out the weld bead that comes through the inside of the tubes. I was hung up on that too at first. I also didn't see how you could possibly sand enough material off the outside of the torque tube and inside of the T, while also sanding the minimum possible from the plastic bushings.

Well you can't. When you slide the T onto the torque tube and get it slipped onto the inner plastic bushing you will note that the other end of the T and the torque tube are not concentric. In my case it was not necessarily "riding hard" against the torque tube but it was touching. Even a zero thickness plastic bushing wouldn't provide smooth operation.

The issue is that you have two plastic bushings which need to be coaxial but are not, so without spherical bearings there would never be a way to get them to run smooth. No wonder so many people have issues getting their rudder pedals to operate smoothly. I considered chucking the whole thing and making my own design, but decided to stay with it if I could.

Using the straightest piece of steel I own (a set of 12" mitutoyo calipers) I verified that the torque tube was pin straight, and then checked the T. One of those forehead slapper moments where it is obvious what happened. The base of the T had curved due to the welding and they would need to be straightened. What you're seeing in the picture is a fixture I made to accomplish the task. I knew it was going to take some force so I used an 8' 2x6 and some plastic blocks (a motorcycle part I designed and happened to have some extras). I placed them so that they would restrain the sections of the T that I wanted to hold still. A 3' section of galvanized pipe with some strategically placed silicone "rescue tape" brought the OD of the pipe to perfectly match the inside of the T and provide leverage. With the T clamped in place I had my youngest son hold the far end of the 2x6 while I worked the galvanized pipe. I started gently and worked my way up until I was able to get the T within about 0.010-0.015" of straight. Of course the second one went much faster. No need to change anything on my alignment fixture for the second pedal because they are identical at this stage.

I test fit them on the torque tube with both plastic bushings in place. Without having even wiped off the sanding debris or using any form of lubricant they operate very well.

The next pictures were from just yesterday. My fuselage is at the airport, tucked in behind my Citabria so I dragged it out in the open and got to work with a 2" sanding wheel on my electric die grinder to knock the welds down where the rudder pedal bracket holes were filled. That went well and I managed to get it done without nicking a tube with the non working side of the sanding wheel. Thankfully the bottom side of the welds wasn't too thick so the clean up from down under was mostly getting rid of the roasted powder coating and getting it ready for primer and paint.

Next I cleaned up the hole for the elevator push pull tube bushing. It still had hysol in it from where the PO removed the bushing (must have destroyed it getting it out too, I imagine). Heat gun and a little love and it was 90% out. Dremel tool with a flapper wheel and it was done. Test fit is perfect. My project arrived with the elevator push-pull tube in the tail cone but zip tied with pool noodles to keep it from banging around. With the new bushing dry fit in place I was able to do a temporary install of the push pull tube and check for friction at the controls. It is operating nicely. I know it's not much but I finally felt like I got something moved forward.

When I get out there later today I will use my die grinder and scotch brite wheels to remove the white epoxy primer applied by the PO where he removed loose powder coating. The steel has been protected by it, now it's time to get to bare metal and make it all red again.
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This pic was taken while the welding was being done on my tail wheel reinforcement. I forgot to remove the center console piece but we rolled the plane super careful so it didn't really bang around.
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This pic taken at the end of the day yesterday. Hoping I can keep up some forward momentum.

Side trip.
Back when I first had some money to buy a plane with I wanted to get a kit. Then I realized that it could be 2-3 years without flying. I ended up buying my Citabria and had instant access to a fun airplane. Now that I have this plane to build I'm motivated, but some days I get to the airport and decide "aw, screw it" and get in the plane that flies NOW. I need to strike a balance.

In the meantime, I'm flying the crap out of the Citabria. I do some informal STOL practice and recently took my youngest son mountain flying. Shown here at Tieton which is a state owned runway here in WA
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[Jerrytex]

Good progress.

The gussets turned out good. I too went through the "bananna" T-Torque tubes. I used a vise and some pipe to get it as close to straight as I could, and then alot of sanding, and fitting to make them smooth. The crazy part is I was missing that part of the rudder pedal assemly and had to fabricate the longer "T" torque tubes. I was careful when I welded it to keep the heat bending to a minumum and it still happened. I think it's just the nature of the beast when welding on tubing.

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[alexM]

I would agree that it would be very difficult to avoid this exact banana when creating this part, especially with asymmetrical gussets. And I know that some experienced welders use strategically placed applications of heat or short welds to make things flat (or intentionally domed). I will say I'm impressed with the strength of 4130 tube. I was worried about it bending too easily or putting a kink in it. It was amazing how much it flexed before the shape changed at all. No wonder it makes such a fantastic material for bicycle and airplane frames.

Today I flew down to TDO to meet Eric and see his barn find Kitfox 5. He's doing a great job of rolling back the areas of relaxed workmanship standards and what he is down to looks quite serviceable. I'm going to have to get some momentum up if I'm going to get mine built anywhere near his deadline.

To that end I'm planning on sanding off the hand applied white primer and then applying my primer, paint and clear coat this weekend. I just researched to see how much time I needed to allow between coats. I know from the primers and paints I spec as part of my job you have to wait a certain time for each coat to dry, but you also have to get the next coat on before it completely cures - otherwise you have to treat it like existing paint and sand it.

There are also paints that have another time line, where if you do let it go past that initial cure time then you have to let it go for a few days or it will soften the layer under it and possibly bubble up. Good times.

Well I'm glad I read up from the manufacturer because I was lead to believe I have mere hours once I mix the two part epoxy. Manufacturer says 4 days. That would of course be shortened dramatically in the (what locals call) hot weather we're having now. Before I use the primer I'll go over everything with wire brush and detail sander to lessen the need to fill scratches from the sander and scotchbrite, then wipe/flash everything with acetone or denatured alcohol.

[alexM]

I put some more time on the project last night (I have to keep up with Eric now). I used my detail sander to prep the surfaces for primer. While I had it out and was making dust I removed all traces of powder coating on the metal tubes both inside and outside where the plastic bushings live. I worked carefully and with good lighting to just barely break through the last molecules of powder coating. That kept the surfaces round and didn't remove any steel.

I test fit the parts dry and was shocked how freely my rudder pedals work now. They literally flop around but aren't the slightest bit sloppy.

Today is much cooler than the past week and it's not windy, so I'm going to get some primer applied.

[Eric Page]

Nice! Can you tell me more about that detail sander? It sounds like something I need to invest in.

[alexM]

A detail sander is just one of those high rpm oscillating head devices that has a head the shape of the rotor in a Wankel engine. The angles are acute so you can get all the way into 90 degree corners.
The originals were the German company Fein and were priced accordingly. Mine was a random Christmas gift from years ago and is a Harbor Freight $40 knock off. I guess "multi tool" is the other name because you can run various metal cutting blades, and is what I normally use it for. It has helped up much better than I have come to expect from Harbor Freight but wear ear plugs..

It should be noted that it's not a random orbit sander but you can achieve a random-like finish if you make light passes and keep it moving consistently.

I'm also getting quite a bit of use out of my Dremel tool. I recall a Bryan Bowen video where he had one basically catch on fire and had to buy a new one. I'm now using mine for 20 minutes at a time and I'm starting to realize that catching on fire is a distinct possibility. It gets pretty hot when you're using it "for real" instead of the 30-60 seconds of use per year it normally sees.

The tools I'm really glad I bought are the two Milwaukee M12 straight and 90 degree grinders. The 90 lives with a 2" Roloc style mandrel that I swap scotch brite and sander discs on. The straight shaft motor has been used to cut 4130 up to 1/8" and most recently has been running an arbor with skinny but long sanding drums.

If the Dremel tool burns up I'll just chuck those Dremel accessories on the straight shaft Milwaukee.

Today I ended up using it all.
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It got all organized and then grabbed my can of 2 part epoxy primer. Followed the directions on the can, shaking for two minutes, whacking the thing on the bottom and shaking for two more minutes. I noted that the can said the pot life was only two days, in conflict with the online instructions.

I had already wiped the parts down with acetone and a lint free towel, so I got to spraying. I was quite puzzled when it came out clear. I know sometimes spray paint can start out clear but I put a pretty good layer on and it still had no color.

Huh. Maybe this primer is clear. I kept spraying but then realized bought gray primer so it should probably be gray. Oh look, I mixed up the two part clear coat that goes on after the red. I guess I know what I'll be doing this weekend after all.

An acetone soaked rag removed all traces of the clear. I wasn't sure that was the case yet but discovered a few hours later that acetone will in fact remove even the incredibly durable epoxy primer on a few swipes.

Once the correct spray can was catalysed I sprayed all the parts. The Germans sure know how to make a good rattle can. It lays on nicely. The only flaws were where I didn't feather the powder coating down smoothly enough.
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You know how it is when you hear that voice in your head that says "don't touch it"? Right. I waited 45 minutes and attempted to feather it in with some 400 paper and light pressure. Made a complete mess of the uncured primer.

Thats when I learned that acetone took it right off, and I was able to pretend it never happened. The second time I sprayed, I skipped the lint free rag. Won't be making that mistake again, but at least this time I didn't try to fix it.

Instead I set the parts aside to cure, gathered my things and headed to the airport.

There i wheeled the fuselage outside, used the detail sander to reduce scratches and feather the powder coating back a ways, acetone rag and lint free - starting to get the hang of this.
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I used strategically placed rags to protect adjacent structure, flight controls, etc then shook the can again for good luck. I started on the bare steel up front and was happy with the way that turned out.
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Then I addressed the areas the PO applied two part epoxy. It's good primer so I really didn't need to remove it, I just needed to smooth out out. Detail sander to the rescue. Acetone wipe, lint free, spray

Working my way to the back of the fuselage, I propped up the tail and removed the rear clamp for the tail wheel. Then I proceeded to use every device I brought with me to clean up the welds, the bare metal, feather the powder coating, etc.

I thought I found a crack and was busy digging at it with various small Dremel bits when my hangar neighbor came by. I had just come to the conclusion I was digging at a glob of powder coating when it came out. He welds and inspected it all. It was all good, so I finished the clean up and sprayed out the last of it.
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Next up, things I should probably already know about spraying red.

[Eric Page]

A detail sander is just one of those high rpm oscillating head devices that has a head the shape of the rotor in a Wankel engine. The angles are acute so you can get all the way into 90 degree corners.

Ah, OK. I know the tool you're talking about. I've got one of those oscillating cutters; I'll have to see if anyone makes sanding heads for it. Thanks, and nice work today!

[alexM]

I was tempted to spray the red last night but then remembered a step mentioned in the manual directing builders to fill moisture traps with structural adhesive. The crevices on the insides of the gussets definitely count as such.

I probably should have done the Hysol before primer but this isn't about strength as much as it's about gap filling. So I apply the expression I often use in my day job: "it doesn't hold the wing on". Besides, fresh primer on good metal isn't a terrible place to start.

So I eye balled the ratio and mixed up my first batch of Hysol. After mixing thoroughly I put it in a sandwich bag and nipped the corner off, cake decorator style. That allowed me to lay a bead in those tight areas with making a mess.

I used the end of a pen to make a fillet, then came back with my finger and some denatured alcohol to clean up any excess. I didn't hate how it came out.

I'm curious what scales you folks use to weigh Hysol?

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I let that cure overnight, then this morning I was up early trying to get some paint on without disturbing domestic tranquility. I flashed all surfaces with lint free alcohol wipe and coreographed how I would apply the red without getting any finger prints in my paint.

I ended up using the same cheater pipe I used to un-banana the inboard rudder pedal tubes. I shot the tight spots by hand and then slid each T onto the pipe. Set on a pair of saw horses I could then get every where else without touching anything.
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The red went on perfect. Not a run or flaw of any kind. I let that dry for maybe 30 minutes then repeated the process with the clear.

I was worried about having rushed the job and was concerned that it might fish eye or worse. What to do other than put my stuff in the car and head to the airport and keep going before I knew, right?

The red went on absolutely amazing. This is going to sound funny but I'm color blind. Oddly, I may not be able to tell you what color something is, but I can detect the slightest mismatch. In a different lifetime I used to do gelcoat repairs on damaged canoes and kayaks. Matching the color on a surface which has weathered can be difficult but once I knew the color I could make the damage invisible.

I can see red just fine, and was super stoked to see the only way to tell where I had painted was because it was flat instead of gloss.
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To keep from rushing the job I walked down to the airport restaurant with my son where we had breakfast. I gave the clear coat a good shake and covered the flat red. That work is now tucked into my hangar to gas off, while I returned home.

Inspecting the rudder pedals I am quite happy with them. No fish eye and no house flies mating in the middle of my wet paint.
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Pretty happy to be at this point. I feel like I can now make forward progress. I'm going to let the red and clear cure the rest of the day, then I'll clean everything well, do another dry fit of the plastic bushings, then lube it up and rivet the assemblies back together.

[jrevens]

Alex,

FWIW, I mixed it by volume. It was very easy to do small amounts using measuring spoons & popsicle sticks, then mixing in dixie cups.