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  1. #51
    A thousand pints of lite. Joker 53150's Avatar
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    Here's something I've really been wanting to do for a while now, test my idea for finishing the plane! As mentioned previously, the plan is to fiberglass & epoxy the plane and leave it mostly clear/natural. I'm using a very lightweight fiberglass for this, which will hopefully limit the amount of epoxy needed. The test is being done on an extra wing I got with the Extra 300s kits. Actually, I got two extra wings, both left sides, and one of them was in such horrible shape I just threw it out. This one was kept to perform tests on.

    Step one is to cut the 'glass to the approximate size needed. This is a leftover piece that'll do half the wing, good enough for me!

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    The epoxy being used is Z-poxy finishing resin, which I'm thinning with denatured alcohol so it is easier to apply. The mix stats off 50:50 resin to hardener, and then I thin that by about 50% with the denatured alcohol. So the final ratio is 1/3 : 1/3 : 1/3. The denatured alcohol gets mixed in after the resin and hardener are completely mixed.

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    With this stuff, a little goes a LONG way! I poured it onto the middle of the wing and then worked from the center out with a brush. After it's started I switch to an old playing card as my squeegee and keep working it farther and farther from center. Excess material is scooped up and moved to thin areas. You really don't want ANY excess material, and the goal is to get as much wetness out as possible. Any excess is removed, and I run the 'glass and epoxy just past the edges. I may try the other half of the wing with a little stain on the wood first, although I'm thinking that would be hard to apply evenly and the wetness could cause other problems - something I need to look into...

    Note: I did this first test without adding any extra balsa filler to the wing panel. It was only sanded smooth and the extra balsa dust was removed. Assuming I do this to the entire airframe it'll all be covered with balsa filler and sanded just to make sure any small dings/dents/scrapes/seams are filled and smooth.

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    For anybody wondering what that black line is across the wing, is the hold-down strap on my "Wing Station", a handy device I got from a vendor at Flite Fest 2016. It'll hold wings, fuselages, etc pretty securely so you can work on the part easily. In my case it's perfect for only 'glassing 1/2 a wing!

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    Here's their owner's manual, it's worth checking them out online if you do a lot of balsa work. Covering a big wing becomes much easier when it's held securely.

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    Joker

    Balsa dust is a wonderful thing, make some today!

  2. #52
    A thousand pints of lite. Joker 53150's Avatar
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    A quick (or a bunch of them) are required before the resin sets up. Part of the reason you don't want excess resin in spots is that it'll allow the 'glass to "float" and not stick down to the balsa. This also creates lumps that have to be taken care of later on, not to mention the extra weight the extra resin adds. After this cures overnight I'll sand and/or scrape the surface and apply another very thin coat to fill any remaining voids. If it works as planned, scraping the surface with a regular razor blade will do most of the smoothing, and will allow the final coat of resin to be ultra thin. But I haven't tried that yet, so we'll see what happens! In the past I sanded and then filled the weave with thinned body filler and primer. This was ok for a painted plane, but that isn't the plan here.
    Joker

    Balsa dust is a wonderful thing, make some today!

  3. #53
    A thousand pints of lite. Joker 53150's Avatar
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    I checked the wing this morning and it looks like the 'glass was done right. I didn't find any streaks, bubbles, or runs in the epoxy. It cured nicely and the excess should be quick & easy to remove. It'll sit for another 7 hours till I get home, at which time I'll scrape it with a razor blade and follow that with another very thin layer. In theory it should then be "done". Maybe? This is a new technique for me, as normally it'd be scuffed up, primed, and painted.
    Joker

    Balsa dust is a wonderful thing, make some today!

  4. #54
    A thousand pints of lite. Joker 53150's Avatar
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    Hmm, mixed results so far. I started off today's work by trimming excess fiberglass off the wing, and then scraping the surface with a razor blade. For scraping it, I simply took a razor blade and scraped it back & forth quickly across the surface. This knocked down a lot of the higher spots to even the surface out even more. While there aren't any bumps or thick spots of epoxy, there are still very tiny high and low spots. After scraping I had quite a bit of epoxy dust, and the surfaces felt smoother and less like the grain of the fiberglass.

    As this is my first time trying this, I didn't know where or when to stop, so I did 2 scrapings and wiped the wing down. Another very small batch of Z-poxy finishing resin was mixed up and thinned with the denatured alcohol, and then applied to the previous layer. I spent some extra time with a new playing card going over it a few more times until there was no excess being removed. My hope is that enough epoxy will remain in the low spots to fill them in level with the high spots. Hopefully. At least I'm hoping it'll be smoother than the previous finish! The picture shows the reflection of my shop lights, and it doesn't look quite as glossy as I'm wanting. Maybe a coat of clear gloss paint will help, although I don't know how well it'll stick to the epoxy finish. Just more stuff to test, I guess!

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    Joker

    Balsa dust is a wonderful thing, make some today!

  5. #55
    A thousand pints of lite. Joker 53150's Avatar
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    Aaaaaaand, I think I have a NEW plan! Looking at options for painting the plane I thought about adding some tint to the epoxy, which led to Google searches, which led to a recommendation of using regular Testors enamel paint. So I tried it. And I like it!

    This was a very small batch of resin, with two drops of red paint, also thinned out with the denatured alcohol. The color isn't very vibrant, but is still subtle enough to clearly show the grain of the wood. I'll need to test a few different ratios of paint to make sure it doesn't throw off the epoxy so much that it doesn't harden, as that might be considered a "problem".

    There is also a concern as to how the paint will tint the balsa filler, so that'll need to be tested as well. But I'm stoked about the possibilities!

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    Joker

    Balsa dust is a wonderful thing, make some today!

  6. #56
    A thousand pints of lite. Joker 53150's Avatar
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    Pushrod work is now underway (when I'm not screwing around with the tinted fiberglass). There are two slots on each side - one side gets the elevator pushrod and the other side gets the rudder. I'll fill the extra holes so they don't stand out too much when the finish work is done. You can see how rough the cut-outs are, as I'm assuming this was all die-cut wood. There is also a bit of balsa filler spread over this area which is only rough-sanded and it makes it look like the balsa is a bit scaly. For the pushrods I'm using Sullivan Goldenrods, which I've used on a number of projects, and they should be plenty strong enough for this job.

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    Joker

    Balsa dust is a wonderful thing, make some today!

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