2.1.2 Joining Trailing Edge Wing Cores to the Spar

So, last week I finished aligning and gluing down the leading edge foam cores for the left wing.  This week I tackled the trailing edge cores.  As I gain experience I’m getting a bit better at leveling the cores as well as gluing them down.  Here is a photo of the left inboard trailing edge cores glued down at the inboard side of the spar.  Those aluminum I-beams on top help to hold the trailing edge for all 4 cores in alignment.

And here is the wingtip side of the trailing edge. This sucker wanted to twist quite a bit so to keep it in alignment vertically I had to use some strapping tape to twist and pull it into shape.  And even if it’s not perfect here, there’s a final straightening procedure that’s used right before applying the fiberglass to the foam cores.  Once that fiberglass epoxy dries it has to be straight or I’m in trouble!

Here’s a shot of the entire left wing core assembly while the trailing edge epoxy cures.  The fiberglass strapping tape is used to pull the cores as tightly to the spar as possible for a good bond.  There will still be gaps and those gaps get filled in later before applying fiberglass over the entire assembly.

Trailing Edge Glued Down

For the right wing, I call this the “Big Oops”, although I’m sure there’ll be more of these in the future! As you can see, the outboard side of this inboard foam core was miscut at the factory, leaving about a 1” gap just on one side between this core and the adjacent core. That gap is way to large to fill in with slurry, so the factory suggested I hotwire a slice of scrap foam to fill in the gap. I did that and with a lot of sanding, got it to fit nice and tight.

Big Oops! (1)

Here’s another view of the problem. The core is not covering the hole on the right even though it is covering the hole on the left.  Hmmmm… That’s a problem. You can see a faint line in the spar (yellow part) that the left side of the core aligns with but not the right side. That’s the gap that needed to be filled in.

More Big Oops! (1)

The end result is a finished right wing. (Finished is a loose term here since there’s still a LOT of work that needs to be done before these wings are flyable!) In the end, I’ve now got two fully glued and cured wings. Next step is to prepare each wing for fiberglass. That means a lot of filling and sanding to get everything as smooth as possible before applying the fiberglass and epoxy. I’m told it’s much easier to get everything as smooth as possible now than it is trying to sand and smooth out the fiberglass.  Makes sense to me.  Here’s a photo of the two completed wings.

Two Wings in the Hangar (1)

Next step is to install the navigation antennas on the wings. We start with the left wing.  Click here for photos!

ui© John Trautschold 2018