The Barn Find Build

[Eric Page]

PS, I don't think I would worry to much about the flaperons, as long as the hinges and the main tube are good, and the damage shown is the worst of it.

Thanks, avidflyer. I was thinking about this today...

Does anyone know what alloy the flaperon skins are made from? If there were markings on mine, they've been removed. I'm guessing 2024, in which case stitch-welding isn't an option.

My initial repair idea is this: Stop-drill the cut in the skin (the hole would be barely around the leading edge, just on the opposite side). Using a wooden buck that matches the airfoil shape, fabricate a patch from 0.020 sheet just large enough to extend about an inch beyond the damage in each direction, with the slot shape pre-formed in the patch. Finally, bond and rivet the patch over the damaged area so that the patch aligns with, and reestablishes the end of, the bracket slot.

For the deep scratch in the other flaperon, stop-drill both ends of the sharp crease, use a dab of Hysol to fill the holes and crease, then use body filler and sanding to smooth out the rest of the dent.

Any other suggestions are welcome.

[109JB]

On the Kitfox IV speedster, the flaperon skin is cut all the way around making a 1/4" gap at each hinge location. At these points the trailing edge is connected with a small metal tab. The 1/4 gap is covered with fabric. Was supposedly done this way to prevent flaperon binding during high g maneuvers. If I remember I'll post the directions for this from the builder manual. Bottom line is that a little cut in the flaperon skin isn't much to be worried about.

[PapuaPilot]

My initial repair idea is this: Stop-drill the cut in the skin (the hole would be barely around the leading edge, just on the opposite side). Using a wooden buck that matches the airfoil shape, fabricate a patch from 0.020 sheet just large enough to extend about an inch beyond the damage in each direction, with the slot shape pre-formed in the patch. Finally, bond and rivet the patch over the damaged area so that the patch aligns with, and reestablishes the end of, the bracket slot.

For the deep scratch in the other flaperon, stop-drill both ends of the sharp crease, use a dab of Hysol to fill the holes and crease, then use body filler and sanding to smooth out the rest of the dent.

Your repairs for the flaperons seem good. AC43.13 would be the best guide, which has you use the same thickness of sheet metal as the original material. I am pretty sure that the flaperons are made from 2024-T3 aluminum.

[Eric Page]

Thanks, guys. I appreciate the info. I'll check 43.13 before I proceed. I'm a long way from needing the flaperons, so they can wait until I'm stuck waiting for parts on something else.

-=-=-=-=-=-

I made some progress the last couple of days. I got the fuselage and vertical stabilizer stripped of fabric, and I'm glad I did. The Poly-Tack application was pretty inconsistent, so the fabric wasn't uniformly stuck to the structure. In some places it came off easily, and in others I had to pick at it with a knife blade to get an edge up that I could get ahold of.

With the tail open I can see how the ribs were done. It looks like Hysol was applied with a kitchen spatula on the end of a broom handle (it ain't pretty!), but the ribs appear to be straight and structurally sound.

Once it was stripped, I got started on removing everything. The doors came off first, then I dove into the flight control system. In all of the controls, there was ONE nut and bolt that didn't fight me. All the rest were either torqued way too tight, or had surface corrosion that made them difficult to remove, or both. I'm REALLY glad I'm taking it apart.

The rudder torque tube assembly is a mess. The pilot's left pedal and the copilot's right pedal are very tight and hard to move. It looks like the nuts holding them to the mounting brackets are too tight, so the tubes are bound up on their bushings. Unfortunately, there doesn't appear to be any way to fix it without drilling out the rivets and separating the torque tubes. The nuts holding them in the brackets just spin their bolts and won't come loose, and the bolt heads are inside the tubes and inaccessible. At least the whole assembly is off the fuselage so I can put it on the bench.

I just need to get some cable cutters and I'll be able to finish the fuselage disassembly. The rudder pedal adjustment handles are trapped because the bolts that hold the cable ends are stuck in the handle tubes, and the cables are captive in the fuselage due to Nicopress sleeves. I have an idea how to get the bolts out using some wood blocks and the bench vise, but I've got to get them free of the fuselage first.

[PapuaPilot]

I'm REALLY glad I'm taking it apart.

That is what you want to say after wondering if total disassembly was the right thing to do.

As far as you rudder pedal issue I would search the forum on this subject. Look especially for the people who did a build log. This is a known problem and it usually takes us several days of work to align, trim, shim, and mount the rudder pedals and get them free from binding. There is a good chance this wasn't done properly at the original build. Now is the time to take care of it.

[Eric Page]

As far as you rudder pedal issue I would search the forum on this subject. Look especially for the people who did a build log. This is a known problem and it usually takes us several days of work to align, trim, shim, and mount the rudder pedals and get them free from binding. There is a good chance this wasn't done properly at the original build. Now is the time to take care of it.

When I discovered the problem I thought it must be a misalignment in the way the brackets were mounted to the fuselage, but the assembly is still very stiff even after it's removed. I need to look at the assembly and fitting procedure in the manual to understand how it's supposed to work, but it sure looks like the bolts/nuts that attach the torque tubes to the brackets are too tight.

Like the flaperons, fixing this will wait awhile. Primary focus for now is getting the fuselage ready to go to the welder for tail reinforcement and additional mounting tabs for avionics and antennas. The disassembled rudder torque tubes will go as well, for gusseting.

[Dave S]

Eric,

It is not that rare that people have some fitment issues with the torque tube mounting. If the original builder did not remove enough material from the hard plastic bearing that could be the issue.

Your comments about encountering bolts that were over tightened may be an issue; but, realizing that the bearings are inserted after the bolts are tightened to the mounting part would seem to indicate that the bigger problem with them sticking may be the fit in the first place.

If a person follows the procedure in the build manual for turning/filing/sanding the bearings down to fit that should alleviate the problem. I found that mounting the bearing on a bolt chucked into the drill press made it easy to turn them down. I also found that working the bearing into a slight barrel shape by taking a bit more off the ends of the bearing while keeping the fitment at the center very close helps a lot with whatever misalignment may be present.

It is not beyond possibilities that if the assembly sat for a while there may be some light surface rust inside the torque tube at the bearing end that may be interfering.

You'll get it figured out.

[alexM]

Yes, those outboard bearings with the hidden bolt heads should pull right out of the tubes. The bolt isn't some kind of chinese finger puzzle.

[Eric Page]

Excellent, thanks for the tip, Alex. I'll give that a try tomorrow and see if the bearings will pull out of the torque tubes. And Dave, I appreciate the tip on fitting the bearings for smooth operation. I'll refer back to this when the time comes.

-=-=-=-=-=-

I finished disassembly of the fuselage today, after having the light bulb come on over my head with the idea that I didn't need cable cutters to get the control cables out -- I could use the Dremel! The cable made short work of the first cutting disc, so I switched to a 4-1/2" angle grinder, which did the trick. That freed the rudder pedal adjustment handles, which had bolts holding the cables in place that were stuck. I put them in the padded vise jaws, applied a little penetrating oil and gave them a few taps with The Persuader, which broke them loose.

I also removed the flap handle and center console, which completed disassembly of the flight controls.

Finally, I pulled off the brake calipers and found that they had significant surface corrosion, some of which appears to extend into the cylinders. If anyone has an idea how to get the pistons out of these things, I'd be thrilled to hear it. I want to check the cylinder bores and pistons, and at a minimum, replace the o-rings.