Chapter 13: Bottom and Sides


Lessons Learned:

1.  Make all the necessary adjustments to fit the nose cone to F0 before installing the foam bottom, sides, and top. Otherwise, it's awfully tough to modify the F0 bulkhead without altering the foam too.

2. There was nothing tricky at all about installing the bottom pieces of foam. But carving the inside of the side foam takes a little intuition and alot of guess work.  I worried alot about hollowing out the inside surfaces too deep.  Not to worry though.  I was surprised at how little of the added foam pieces remain after hollowing out the inside surfaces.  Here's how mine looked prior to 2-BID taping.

3.  How did I get such a sharp, feathered edge line where the foam blocks transition?   I found that no amount of sanding will ever feather the transition point where the micro gets exposed.  This is especially true with urethane foam.  Continuous sanding does very little to take down the cured micro, but does create two unwanted depressions on either side.  So, I create an intentional feather line by taking an exacto knife, cutting through the micro where I want the transition line to be, then carefully lifting the micro that falls outward of the line from the bottom foam (in this case, the big side block of foam).  I can usually separate the micro from the bottom foam without gouging or marking the bottom foam.

4.  Do be careful to install the side foam flush with the bottom foam pieces.  Else, the foam will be too far inboard and won't be there to carve, especially if you're going for a more rounded nose.

5.  I had trouble installing the sides to the nose.  The micro and unwetted cloth decided to unionize with the garage gremlins to make my life a living hell  (In plain English-- the micro rubbed off onto the unwetted cloth, the cloth folded underneath the foam, became unmanageable, and made a complete mess).  I trimmed off the now-wasteful cloth and let the sides cure.  The next night, I micro'd and 2-BID taped the sides in place.  I'm glad I did it this way because I had to put more micro down to fill gaps previously hidden by the unwetted cloth.  2-BID taping was a lot easier too.

6. I made full-sized patterns (plan view) before carving the nose.  I measured the depth of the nose cone for every width of inch, then also measured the width of the fuselage at 6 inch intervals along its length past F22.  I transposed these measurements onto my workbench and drove nails in these locations.  I then used a batten (if you don't have a sailboat you can use a long thin strip of wood...) to loft a nice elliptical curve to form-fit the points.   I made two patterns.  I clamped one onto the top of the fuselage and one onto the bottom.  From there, it is a simple matter just to take my spline sander and sand along the pattern.  Sure beats eyeballing it.


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