Bulkhead Installation



With the fuselage cutouts complete, the next chapter in the builder's manual had me install the bulkheads that I built last summer (1998).  Before doing this, however, it was necessary to have the fuselage perfectly level.  You can read about that process here, or by picking the fuselage level button at the bottom of this page.

There was an outstanding issue that I wanted to clear up before I actually began installing parts: from my experience with the big toys (e.g. B-2, 777), I knew that the edges of a composite sandwich panel are usually sealed (or "potted") to prevent damage and fluid ingress into the core.  So far the builder's manual made no mention of edge potting.  I got ahold of the factory and questioned them on this.  Their response was--indeed--edge potting was recommended.   Strange, I thought, that this was never mentioned earlier.  I wonder how many other builders thought to ask that question, and more importantly, what other undisclosed processes I may have neglected.

The photo at left shows how I used my Dremel tool to grind away the foam core along some of the edges, to be followed by the application of epoxy/flox, epoxy/microballoons, and/or SuperFil (I did a little experiementing).  Note that not all edges were sealed, just those that wouldn't be eventually be glassed over.  After curing, all sealed edges were sanded smooth.   By the way, the 3.61" wooden blocks are just used as spacers during installation and were removed after the nose gear plates were firmly glassed into place.  

OK, now I was ready to begin installing bulkheads.  No, wait.  There was one more fuselage cutout required: the cutout for the nose landing gear.  After some careful measuring and marking, I made the cutout as shown at right.

OK, now I was really ready to begin installing the bulkheads.

In nearly all cases, the bulkhead installation entailed tacking the part(s) into place on one side with Bondo, hot glue, tape, or even go ol' friction, then laying up 2 plies of "S2" glass on the other side.  Once cured, the peel ply was removed and any excess glass was sanded/ground flush.  Then the Bondo, hot glue, or tape was removed and the other side was glassed with 2 plies of "S2" glass.

Some layups were trickier than others.  The one shown at left was one of the easier ones; relatively unobstructed and straight.  It was a little more difficult to make the fiberglass (and especially the peel ply) conform smoothly to the highly curved joints.  Attempting to avoid glassing over fasteners or through-holes did prove a bit challenging for some joints.   In some cases I masked off the affected areas and trimmed the glass to fit around them.  In other instances, I simply glassed over holes and had to re-drill through them.

I also found that positioning the parts was as time consuming as glassing them into place.  All bulkheads had to be parallel and perpendicular to eachother in all 3 axes, and making that happen inside a highly contoured fuselage wasn't so easy; I used many levels, measures, and even a plumb bob.  The station lines for the major bulkheads were inscribed onto the outside of the fuselage (part of the mold), but I found these unreliable to guarantee the bulkheads were straight.  I used them more as a general reference to station location and instead relied on measurements from other bulkheads and reference to a "chalk line" I made down the center of the floor.   The photo at right shows how I used a level, a plumb bob, and some 6" spacers to located the FS-43 Bulkhead.  At this point it is being held in place by 2 globs of Bondo on the forward (non-visible) side.  The gap between the top edge of this bulkhead and the skin section is where the windshield will eventually slide into place.

When I was fitting the instrument panel bulkhead into place one day, I decided I really didn't like the way it fit, nor did I like the way it looked.   Nothing too major... it just didn't look symmetrical.  It was also a little bit low for my tastes.  The blueprints had 2 choices for the instrument panel (and bulkhead): standard and tall.  Back when I was building templates, I really couldn't tell much difference between the 2, so I opted to build the standard.   Now that I know better, I should have built the tall version because it sits higher off the floor (a benefit for us 6'2" guys with long legs).  But fear not.  With my ever-increasing composites confidence, I decided to covert the standard IP Bulkhead into a tall version by splicing in some additional core and blending the fiberglass facesheets together.  I also decided to re-do the upper, curved portion by cutting it out, building a new piece to the shape I desired, and splicing it back in.  It took some time, but I'm happy with the end result.  I'll breath easier knowing that I now have an additional 1.4" leg room, and a perfectly symmetrical shape.

Once the IP bulkhead was glassed into place, the last task in this section of the builders manual was to turn the fuselage over and glass the Nose Gear Plates to the OML.  Nothing too tricky here, but these plies were added to the outside of the airplane.  I had to sand the edges down and then fair them out with SuperFil so that they won't be visible under the future paint job.

That's about it.  The fire wall won't be installed until after the center spar goes in.   Next it's time to tackle the window installation.

 

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