The Barn Find Build

[Eric Page]

Made a little progress this week. Using Dave's advice I used compressed air to force the brake pistons out of the calipers. I started with 5 psi and worked upward from there. It got scary before they came apart. In the end I had them face down on the garage floor, on a furniture blanket, with my foot on them. It took 120 psi before they popped out! The pistons have a little discoloration from corrosion, but they should be perfectly usable. The cylinder bores (the most expensive part, naturally) are probably a write-off. I can feel significant roughness in the area where the o-ring rests, so I'll be very surprised if they don't spray brake fluid all over the rotors.

After a few days doing landscaping, I got back to scraping Poly-Tack and Poly-Brush from the fuselage. Apart from some small areas where the frame is sitting on the saw horses, the scraping is mostly done. Next step will be to wipe it all down with acetone to remove any remaining residue. Once that's done, I'll need to inspect every inch to find places where bare metal might be exposed, either from inadequate powder coating from the factory, damage during storage or transport, or my own ham-fisted scraping efforts. Those spots will need to be cleaned of any corrosion, roughed up with light sanding, then sealed with fresh epoxy paint.

[Kitfox Pilot]

Thanks for this idea Eric. I have glue all over me by the time I get a job done. That should help. Harlan

Attached Images
Thanks for this idea Eric.

[rv9ralph]

M The cylinder bores (the most expensive part, naturally) are probably a write-off. I can feel significant roughness in the area where the o-ring rests.

You may be able to hone the roughness off, it may just be residue from the decaying O rings.

Next step will be to wipe it all down with acetone to remove any remaining residue. Once that's done, I'll need to inspect every inch to find places where bare metal might be exposed, either from inadequate powder c

You might try MEK, if you can still find it. If I remember correctly, the Poly-Fiber products are thinned with MEK.

Ralph

[efwd]

MEK also makes short work of the powder coat as well.

[Eric Page]

You may be able to hone the roughness off, it may just be residue from the decaying O rings.

I plan to try that before I buy replacements. I hope you're right, but it sure looks like corrosion on the aluminum.

You might try MEK, if you can still find it. If I remember correctly, the Poly-Fiber products are thinned with MEK.

Indeed they are, but I can't find any locally. I exchanged a few emails with someone at Poly-Fiber and they said acetone works too. It does, but boy do you go through the paper towels. They quickly get loaded up with Poly-Tack residue, and you end up just smearing that around. It's a messy and frustrating process.

MEK also makes short work of the powder coat as well.

Good to know. That would be a blue air moment for sure.

[Eric Page]

Re attached photo: this, boys and girls, is why we don't use Teflon tape on our fuel fittings!

I completely disassembled the header tank. Out of 13 threaded joints, six (where brass reducers were threaded into the tank) had what appeared to be dried, crumbly plumber's putty, and seven (where AN fittings there threaded into the reducers) had Teflon tape. The tank contained plastic swarf from when the bosses were tapped at the factory, and bits of dried putty. I had to chase the tank threads with a pick to clean out the remaining gunk, and clean all of the fittings with a wire brush. I don't have any of the specified Permatex thread sealant, so I bagged up all the fittings for later reassembly, and I'll need to rinse out the thank, obviously.

Speaking of header tanks, I have the polyethylene tank. I seem to recall reading something about leaks with this tank. Can anyone provide details on this issue? Do the tanks crack, or do the threads weep, or something else? I'd like to avoid spending $335 for the aluminum tank kit if I can avoid it.

I also finished scraping Ploy-goop from the fuselage structure and wiped everything with acetone to remove any remaining residue. I still need to go over it with a damp cloth to get 25 years worth of dust off of everything, but the fuselage is almost ready to go to the welder for the tail reinforcement and other mods.

Today I gave the rudder structure the same treatment: scrape off Poly-goop, then wipe with acetone. I didn't want to scrape the fiberglass leading edge, so I sanded that with 120 grit, which worked great and left a nice, smooth surface for the fabric. Once that was done, a quick blow-out with shop air and another acetone wipe cleaned it up nicely. The previous builder made one extra slot in the fiberglass within 1/4" of the correct slot, and the fiberglass between the slots has cracked through, so I'll need to bond in a reinforcement to the back side before covering. Fortunately, there's plenty of the fiberglass material left over. I'll be able to reshape the rudder horn opening at the same time, as his cut-out was a bit rough in that area.

[PapuaPilot]

Good find on all of the fuel fittings! Use the right type sealant on them.

For the header tank just throw it away the plastic one. I haven't heard of anyone who had long term success with the poly tank. Bite the bullet and get the aluminum one. I went through the same thoughts with the poly tank that come with my 1999 kit (in 2013) and ended up buying the aluminum one. No regrets.

Keep plugging away. The best way to do things is right the first time.

[Eric Page]

What's the issue with the poly header tanks? I'll buy the new one if I have to, but I'd like to know what problem my money is fixing.

[PapuaPilot]

Here are some suggestions for this topic.

1. Check out this thread: Replacing original header tank with aluminum SS7

2. Do a search on the forum about "header tanks". You will find several about the poly header tanks.

3. Call the factory.

Let us know what you decide after doing a little research.

[alexM]

What's the issue with the poly header tanks? I'll buy the new one if I have to, but I'd like to know what problem my money is fixing.

I sold my NOS plastic tank to someone on this forum since my project came with an aluminum and the original plastic. I should stop selling my surplus parts until you've had a chance to pick through them.

Shortly after selling the one I had someone told me the plastic tanks all split with out much provocation. I don't think I need fuel spilling under the seats in flight.

Hoping to see pics of the welding soon. You've got some catching up to do!