Project: Cozy4     -     Entry

Mar 30, 2004 9.5 Inside Layup and Upper Longeron Installation Category: C05 Fus Side
I must have a wider roll of UNI than Nat did when he wrote the plans because the plans clearly show 4 passes to cover the sides at the 30-degree angle and it only took me 3. I double-checked the angle twice to be sure, but it was correct. Suits me fine. To make this less messy I didn't wet out the first layer before putting on the second. The MGS I'm using still wet out the fabric really well (of course, it was 106 degrees at the time!) and I was very careful to spend a lot of time eliminating all air bubbles. This makes it much easier to lay out the second layer. It only works for about two layers at a time, and it helps if your micro is a little wetter than average. This won't make a resin-heavy layup, because the bottom fabric layer wicks out the excess epoxy.

I love it - "This step should take you about 3 to 4 hours." Well, I'm up to 6 hours already and I haven't even installed the horizontal UNI on top of the longeron. The first big layup is a real education. I went through 6 cups of micro and 10 cups of epoxy. I did one thing right, though - I used almost entirely Slow hardener and even so I'm lucky I decided to stippled as I went because the beginning of the layup was setting up by the time I did the "bubble check". I'm still glad I use a digital scale and no pump. The mixing steps gave my arms a chance to rest from stippling. It's only two layers of glass but they're HUGE.

Unfortunately, I ran out of peel ply during this layup so I laid on a bit thicker coat of epoxy in the areas that will need sanding later, to avoid damaging the fibers.

I'm actually a little unhappy with certain aspects of the plans. This section makes it very obvious that some background in both composites and pusher construction are expected, so Nat sometimes overlooked the skill sets of new builders. For example, laying this whole thing up at once was a real pain in the butt, but there was no need for it. It would have been perfectly acceptable to lay up one side at a time, letting the excess fabric from each side hang down into the channel between the sides, for a later knife trim. (The upper longeron makes a GREAT guide for a long razor blade.) Moreover, as you work air bubbles out of one side you tend to pull on the UNI fibers and this affects things on the other side. I had a number of areas that lifted up and left me air bubbles no matter how hard I tried to get it all to lay flat. It took some time to fill and it was all unnecessary.

I did do one thing different that I'm happy about. I didn't run wood block spacers between the longerons during the layup. Instead, I masking-taped some small spacers just at the tops so I didn't have to cut the layup between, then knife-trimmed it after the fact. The Fein and a hacksaw blade cleaned up the few rough spots this created. This was a heck of a lot easier than trying to stuff a wax-paper-covered spacer down between the two top longerons without disturbing anything.

I haven't posted pictures for this section yet because my hard drive is having issues and I don't want to download them from the camera. I hope to post three. The first is a shot of an air bubble area in the strake cutout section that I don't intend to fix. It's not really a bubble, but more of a delamination. Still not good. The second is me standing the instrument panel on its side to get a feel for the space inside the fuselage. It fits really well against the longerons and side so I'm happy about that. There's a gap on top of the longeron itself but this is no problem; I hadn't put the four UNI layers on yet. Finally, there's a shot of me cutting the four UNI strips that help hold the longerons against the sides. This is the beauty of the rotary cutter - this is a 102" long roll of UNI and I counted 24 layers in the roll. Try doing THAT with scissors! Fiberglass stromboli, anybody? I still have a few air bubbles that I didn't fix, but since these are in the strake cutouts I don't intend to. Moving on...

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