The Barn Find Build

[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.