The Barn Find Build

[Eric Page]

Well, fellas, you're not going to believe this, but I actually worked on my Kitfox today. First actual work in the garage since Feb 18th, 2022.

I moved the car out for the winter (I'll regret that in December when I have to report to work at 5am), moved the wing cradle away from my work table and got busy on a job that I've been dreading since I brought the plane home: repairing the seat pan.

The first builder appears to have trimmed it with a hacksaw blade while three days into a bender. Here are just a couple of examples (there are many more like them):

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I went after it with coarse sandpaper and a rotary sanding drum. My idea was to sand back the damaged edges to eliminate the over-cuts, then add back material -- either with polyester repair putty and milled glass, or with glass mat and resin -- until I have enough to reshape the edges properly. Here are a couple of the bad spots after sanding them back:

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That second photo shows my preparation for adding glass mat to the back side to rebuild the area that's scalloped out of the edge. I've never done any fiberglass work before, so I'm relying on an article in a recent issue of Kitplanes about extending an engine cowling; it looked like the technique would work for this too.

For the small areas where the over-cuts were sanded back, I mixed up some repair putty with a lot of milled glass and slathered it on, making sure to get it spread onto the back surface as well. Here's what that looked like:

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In the center seatbelt slot, I didn't want to extend the slot by sanding so I just filled the over-cuts with putty.

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I fully expect the putty to take a week to cure since the garage is only 60-ish degrees, then it'll probably just break off the edge when I start to shape it. Apparently that's not a big deal with fiberglass, as it's supposed to be almost infinitely repairable (or so AlexM told me once). We shall see.

For now, the garage smells like a canoe factory so I'm back inside.

Oh, I almost forgot: the glass mat and resin repairs will have to wait. My PolyEpoxy crystalized into a solid mass in the can. Aircraft Spruce says you can heat it up and it'll return to liquid and work fine, but that it can take many hours to melt completely. I've repurposed a small crock pot to handle that job. Hopefully it doesn't poison my next pot roast...

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[alexM]

^First clue that someone is a bachelor---> Heating up fiberglass resin in a crock pot on the kitchen counter.

Also on the list:
De-greasing car parts in the dishwasher
Baking a car headlight in the oven so you can remove the clear lens

Glad you're working on your plane though! Let me know if you need any help with the fiberglass stuff. That (unlike electrical stuff which you've been so helpful with) is my wheel house.

[Geek]

Good to see you're back at it Eric!!! After drooling over your prop set up, was beginning to worry you were going to get stuck over at the dark side (turbines) and miss the fun side.

Gary

[Eric Page]

Let me know if you need any help with the fiberglass stuff.

I'll make you a deal, Alex. You come down here and do my fiberglass work, and I'll head up there and do your wiring. Everybody wins. I'll even swab out the respirator and put fresh cans on it for you.

...was beginning to worry you were going to get stuck over at the dark side (turbines) and miss the fun side.

Fat chance. Unless a turbine is on fire it's pretty mundane flying. I flew out to a little fishing town on the coast a few days ago for lunch with my neighbor in his '53 C-180 (it was actually a 4-ship; the other three were an RV-6, an RV-9A and an RV-12). Kinda lit a fire under my lazy butt.

The RV-12 guy is desperate for me to finish my Kitfox so he won't be the slowest any more!

[Kitfox Pilot]

[QUOTE=Eric Page;109769]I'll make you a deal, Alex. You come down here and do my fiberglass work, and I'll head up there and do your wiring. Everybody wins. I'll even swab out the respirator and put fresh cans on it for you.


Man I wish I had that deal offer when I was wiring! haha

[Eric Page]

Well, the polyester repair putty didn't work. It never cured beyond the consistency of chewed gum. I suspect that I didn't add enough MEK to the putty, so it never fully cured. I seem to remember having a similar problem the first time I used it, to plug the badly drilled holes in the seat pan. Anyway, I pulled it off, scraped away as much as possible, then rubbed at it with acetone to remove the sticky residue. Sigh...

Instead of trying that again right away, I moved to rebuilding the edges where I had to grind away significant material. To form a backing for the new material, I softened a hotel key card (thanks, Hilton!) with a propane torch, then formed it to the seat pan and taped it in place.

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Next I cut out some patches of fiberglass mat in increasing sizes to layer into the repair.

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Finally, I mixed up ~12g of epoxy (the crock pot melted it beautifully), barely saturated the fiberglass, wetted the seat pan surface, then laid in the layers of mat. Lather, rinse, repeat.

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I'm pretty sure they're going to need more glass on the top side once the key card is removed (if they can be removed... it has just occurred to me that I don't know if hotel key cards stick to epoxy!). Oh well, fingers crossed.

[alexM]

Definitely not enough catalyst on the first try. I did the same thing with the stuff I used on my Laker Leading Edges. Once I started weighing it instead of eye balling it, the stuff worked perfectly.

Weird trick I learned from boat builders which applies to woven fabric (not necessarily the mat like you used) is to apply the big patch first, then medium, then small. Seems backwards to all of us but if you do it the "normal" way it's more difficult to work out the bubbles/excess resin where it steps down.

Last thing and then I'll shut up. It has been a while since I've done a lay up but it used to be that mat and epoxy didn't get along well. The reason is that the mystery goo that holds those random fibers together breaks down readily in the presence of styrene (found in poly, iso, vinyl ester - aka stuff that smells like normal fiberglass resin), but not in epoxy. It's quite possible that mat has been developed for epoxy since then and I don't know about it. It will still work and will still give you good structural properties, it just doesn't lay down as nicely while you poke at it with a brush.

The hotel card is likely made of PVC. Great idea to warm it up and make it a one sided mold. I'm actually not sure it it will release. If so that is a great find!

[Eric Page]

Definitely not enough catalyst on the first try. I did the same thing with the stuff I used on my Laker Leading Edges. Once I started weighing it instead of eye balling it, the stuff worked perfectly.

The stuff I have here is from Total Boat. The directions on the can say to use 14 drops of MEKP for every 100g of putty. I'm trying to mix 10g batches, so accurately measuring the catalyst is a problem. I tried again today; see my next post...

...apply the big patch first, then medium, then small. ...if you do it the "normal" way it's more difficult to work out the bubbles/excess resin where it steps down.

Yeah, I discovered that. I ended up with a significant step at the edge of the seat pan, which presumably resulted from an air pocket between the glass and key card.

[Mat] will still work and will still give you good structural properties, it just doesn't lay down as nicely while you poke at it with a brush.

I was actually surprised how easy that part was. I expected it to completely come apart since the pieces were so small, but it mostly held together and I only had a few fibers coming away on the brush, even when I used tiny scraps to fill in. I used a disposable 1/2"acid brush; it seemed to work fine.

[Eric Page]

Alex's worry about the hotel key cards releasing from the epoxy was prescient; they didn't. I did get them off, but both left their top layer of clear plastic behind. You can see it in the second photo below, where some of the printing went with it. Fortunately the violence required to get them off didn't break the fiberglass. I take that as a good sign.

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I decided to make another attempt at the repair putty, this time mixing a "hot" batch, with about double the specified amount of MEKP catalyst (3 whole drops in 10g!). Again, I added a good amount of ground glass to make a thick slurry. I troweled that on top of the fiberglass, bringing it about flush with the top surface of the seat. I'll plan to trim it all flush with the edge, then sand and fill with Smurf poo.

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Since I had plenty of the putty left, I went after the other spots again as well. I'm not sure how healthy it is to get that crap on your skin, but I found the only way I could shape it the way I wanted was with the tip of my finger, so that's what I did. I haven't started trembling and drooling yet, so maybe I got away with it.

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I turned on a heater in the garage and headed inside before the fumes cooked my few remaining brains.

[jiott]

Eric, just curious why you didn't just wrap the patch material over the edge and onto the front finished side? It seems it would make a stronger, easier applied patch. Admittedly it would require a lot more sanding to bring it to finished dimensions, but a good old Dremel tool would make fast work of it. You will have to refinish/repaint the front side anyway. Just my 1.5 cents.