Sunday, October 7, 2012

Ch 6: Installing the Bottom

Better to be lucky than good
This post has a happy ending but it almost didn't.  The time had come to install the bottom.  All was ready and the prep went well.  I planned my work and worked my plan.  First I applied a thin layer of resin to the mating areas, then I buttered up all the mating areas on the fuselage, then to install the bottom.

With my father-in-law helping, we gently lowered the bottom onto the fuselage inserting the front first, then the back, carefully aligning with my marks to assure me everything is lined up correctly.  We then started applying some weight on top to put pressure on all the mating joints.  First we added a tool box down the center, a case of water bottles, various storage bins filled with garage accessories, even kitty litter containers I use to soak up oil spills, anything with some weight to it.  Everything was going great but as I turned to get some additional weight...CRASH!  I turned to find my fuselage hanging half off the sawhorses with items I used to add weight littered all over the floor...Oh the horror!

After a second or two of disbelief, we jumped into action establishing some new hard points to support the fuselage.  I knew I didn't have much working time left on my resin and I certainly didn't want to scrape all this off and start over.  We were able to get the fuselage level again in about 10 mins (this time better supported) and inspection indicated that there was only superficial damage that I could attend to later.

Damage Assessment & Repair
Fortunately the damage seemed minor and there was nothing to prevent us from resetting and continuing the mission.  There were two obvious minor damaged areas.

The first was a small gouge out of the bottom of the IP.  This was a raw piece of foam I added anyway because of the IP comes out .25" short.   I cleaned up the damaged IP bottom, floxed a sliver of foam where it was missing, fared back the glass and installed a BID repair on the raw foam, then taped the seam.
Small gouge out of the .25" added foam at bottom of IP

The second was a small split in the lower triangular longeron just behind F22.  I had installed an alignment screw to hold the bottom on at this location and the screw got hit in the fall causing the wood to split.  Luckily it didn't break all the way just split out a partial section between two relief cuts.  Fortunately, I still had some triangular longeron stock left over (BTW, save all your extra foam and wood pieces) so after removing the damaged section, I cut a matching section to replace it, sanded it to fit, floxed it in place, and taped the seam.

Split lower longeron forced by an alignment screw

The Not So Obvious...
A few days later I noticed a small crack in the outer PVC foam.  I decided to investigate little deeper so I did some inspection tapping in the area and I could hear what sounded like delamination.  Sure enough, the large front Last-a-foam spacer between F22 and the IP was cracked all the way through.  Looking back on the fall, one of my saw horse extensions came loose and went vertical.  The 1x1 lodged into the center of the falling fuselage just fwd of the IP (the cause of the IP damage).  The center of the bottom was forced upward...but remember I had secured the corner with an alignment screw.  Since one corner was secured, instead of just pushing the bottom off, it caused the bottom to bend at the center and cracked the foam that is sandwiched between the glass and the blue PVC foam.

I began cutting into the PVC foam to find the crack and then traced it until it ended.  I didn't take a picture of the crack but you can see in the picture below its extent by the foam I replaced.  The crack ran vertical from the top right and curved down to the bottom of the picture.  The area that runs to toward the aft (left) ended up not being a crack but just a stress point in the glass that I could see in the glass on the other side.

I injected the crack in the foam with raw resin all along the crack.  Then I micro'd in replacement PVC foam and sanded it all back down.  I think's it's now as good as before and I should not have any problems with this...especially since a portion of this area will get cut out for the nose wheel well anyway.  It doesn't look pretty but the repair matches the bottom lines and sanded smooth easily.  The light colored areas are where the micro squirted out and was sanded down. it's starting to look like something.
Fuselage looking forward into the cockpit
Fuselage looking forward from behind
the firewall into the back seat

I feel good about all the repairs and I've finished taping all the off to chapter 7 I go.