Building the Bottom

Building the bottom of the fuselage is much like building the sides, only the jigging isn’t nearly as complex.  The first thing you do is glue several 3/8″ sheets of PVC foam together, just like building the sides.  This is trimmed to fit between the forward landing gear bulkhead and F-22.

Once the foam is trimmed along the longitudinal axis of the plane, it is weighted down, and you trace out the longerons, and where all the other pieces of structure contact the foam.  While the foam was upside down on the fuselage, I used a combination of Bondo and hot glue to build a frame on the bottom to maintain the curvature of the bottom when the foam was flipped over on the table.  Once it was back on the table, I trimmed the outside of the foam to match the outside of the lower longerons, per plans.

Foam in frame

As you can see in the picture below, I traced out the landing brake.  What you can’t see is the pretty good job I did cutting it out with a 45 degree bevel all the way around with a jigsaw.  I wish I had gotten some pictures of that before it all got fiberglassed.  Oh well, there will be plenty of pictures of the landing brake in the future.

Landing Brake traced out

Just like with the sides, the contoured shape of the inside of the bottom is created by carving many pieces of urethane foam.  Also like the sides, this was the most time consuming part of the process, and took all the cozy working hours of a weekend.

Laying out contour pieces

Here’s the whole bottom, ready to be glassed, after microing all the contour pieces in place:

After work the following Monday, Heather and I tackled glassing this thing.  First all the foam had to be microed, and it seems I never ever mix enough of the stuff.  The whole bottom is then covered in 2-plies of BID, and the rear seat area is covered in an additional ply for supporting people standing in the back seat.

Performing this layup was quite the challenge, as it was with the sides, because of the difficulty associated with getting the fiberglass to lay down in the corners of the contour pieces.  We exacerbated the level of difficulty by running out of BID just as we were finishing the second layer.  The second and third layers of BID in the back seat area are now a patchwork of the BID scraps we had left over from all of our progress thus far.  We made sure to overlap each scrap by an inch, as is standard procedure, so strength shouldn’t be compromised.  However, because there was so much overlapping, and so much epoxy was retained by the peel ply in smoothing all the transitions, our fuselage bottom is probably a little heavier than average.

Fiberglassing the bottom took Heather and me 3.5 hours just to do the glass work.

Stay tuned for installation of the bottom!

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