With the lower fuselage joint nearly complete, the last step was to add 2 plies of EBX-1200 (if I recall correctly) fiberglass cloth over the top of the joint. With my ever-increasing fiberglassing skills, this task wasn’t particularly challenging.
For smaller layups, I found that wetting the fiberglass cloth with epoxy resin was easier when accomplished on the work bench. But for larger pieces like these, I prefer to do the layup in place.
The first ply of EBX-1200 cloth was laid up over the exposed foam core, after filling the open cells with a wet micro mix, of course. A 1 – 2 inch overlap on all sides was the standard. Then another ply on top of that one, with anothere 1 -2 inch overlap.
Apply a final peel ply, and let the whole thing cure. Voila! Lower joint complete.
A side note here for those of you with bad backs: don’t build this airplane. I don’t have a bad back, but after several hours hunched over in the fuselage working on this joint, I sure felt like I did. And I was only half way done.
Also, get yourself a set of knee pads. You’ll thank me later.
Now that the lower fuselage joint was essentially bonded together, the next step was to strengthen the joint. This is achieved by filling the “valley” with rigid foam core, then glassing over the top. For this project, the Builders Manual called for medium density 3/4 inch core. Although lower density than the 1/4 inch stuff I was using to make bulkheads, I found this foam more difficult to work with. It was difficult to sand, although responded fairly well to rasp files.
Trying to fabricate one long piece of foam to fill the entire ~10 foot long valley would be have been ridiculous, so I attacked it 16 inches at a time. Each 16 inch (approximately) section of core was carefully filed, shaped and sanded so that it fit exactly into the valley. This was a very iterative and time consuming process of shape-test-shape-test-shape. Once I was satisfied with the fit, the foam section was bonded in place with a wet mix of epoxy micro, with some dead weight to keep it in place. I prefer Play Sand for this job.
Then the process was just repeated over and over until the entire lower valley was filled up to the area of the NACA inlet.