Friday, June 15, 2012

Ch 6: Building the Fuselage Bottom

On to step 3 of Ch 6...the fuselage bottom.  This two-sided canoe-looking thing is going to get a 3rd side to it now.

Framing:  The process starts by gluing 3 sheets of 3/8" PVC foam together so their long enough to go from the F22 bulkhead back to the fwd gear bulkhead.  With the foam laying across the bottom, the edges of much of the interior are marked on the inside of the foam using a sharpie and a wooden frame is built to hold the bottom in its curved shape so it stays that way when you move it to the work bench for glassing the inside.

1x2 frame built to hold the bottom foam in shape.  Pic shows the spacers (white line) discussed below installed for fitting.

In the middle of shaping and installing the spacers
Spacers:  Next, spacers are built from Last-a-Foam to provide some added dimension to the interior.  This is the same process used in Ch 5 when the sides were built...except I'm much better at it now.  My beveled spacers came out more consistent and nicer looking than the ones I made for the sides.  (TIP) This was in part due to a little tool I created to help provide the proper 30 degree bevel.  The tool (below) is just a piece of 2x2, cut to match the 30 degree angle for the spacers, with sandpaper on the face.  It worked perfect.

Once the spacers were shaped, I temporarily secured them with wood screws and checked the fit on the fuselage. (see top pic)  It came out amazingly accurate...only a few small adjustments were made.  Time to micro the spacers down to the PVC foam and prep to glass the bottom.

Onward, cab

Wednesday, June 6, 2012

Ch 6: Heat Duct & Seat Back Brace (Part 3 of 3)

Final Assembly
I would have been done with the heat duct but since I had to add the extra foam to the sides of the duct in the back to accommodate the wider seat brace, I have to add glass over that to finish it out.  This was pretty straight forward using 2 plys of BID.  I failed to take a picture of this but it wouldn't be very exciting.

De-skinned Seat Brace.  Removed glass on the left.
OOOPPPSSS!  I glassed the exterior of the seat brace and it went very well...until a couple of hours later when I suddenly had a stray thought.  "Did I cut that glass with the correct orientation?"

Sure enough, after checking the part and retracing my actions, I had glassed it with the fibers at 90 degrees to the base of the brace instead of 45 degrees per plans.  In the long run, this probably would have been OK, but my conscious wouldn't let me live with it.  It is a structural part and you never know when you may need a part to be at it's strongest.  The brace wouldn't have been as strong as designed with the fibers running that direction.

Since it had only been 10 hrs since I finished the glassing, I applied a little heat action with my heat gun and the glass pulled off fairly easy.  A little dry micro to fill some foam that pulled off and new glass was back on 2 hours later.  What a waste of time...all because I wasn't paying attention.  Lesson learned I hope.

Now I checked the fit in the Cozy and made final adjustments before joining the two pieces.  Here they are after being floxed together and joined with 2 ply BID at the sides.
Note the added width allowing
2 water bottles in the map pocket.

Final Assembled Heat Duct / Seat Brace

Final Installation in the Cozy
Installation was pretty easy once I got it fitted well.  Now it's time for the fuselage bottom.

Onward, cab