Sunday, May 20, 2012

Ch 6: Heat Duct & Seat Back Brace (Part 1 of 3)

Seat Back Brace
Step 2 of Chapter 6...boy, chp 6 has some big steps.  It's now time to build the keel of the aircraft.  This consists of the front heat duct that runs along the floor up to the instrument panel and a triangular seat brace that provides support for the seat back (duh!) but also houses  a map pocket for some storage, the fuel valve, and a mount for the manual landing brake lever.  I'm not installing the last two items here since I''m converting to an electric landing brake actuator and I'm moving my fuel valve to either the center console or the instrument panel where it's easier to see and use.

Note: Ignore the extra 2.25" added to the bottom (height)
of the Seat Brace Triangles.  I changed this later back to the
plans what I was doing below.
At the right are all the pieces to make the heat duct and seat back brace.  At the time of the picture I had already glassed one side and floxed in the birch triangular reinforcements per plans.  I suppose you could leave out the birch reinforcement if you're not using the manual landing brake, but I thought I would go ahead and install the pivot tube for the brake lever and possibly use it to engineer a fold down arm rest like the one below. (idea from Keith Spreuer)

Keith Spreuer's Folding Arm Rest

Wider Map Pocket
I'm making a small deviation from the plans here.  Checking the archives, I noticed a few folks who thought the map pocket was handy but needed to be wider as you couldn't get your hand in it to retrieve small items.  I thought if it was a little wider it could be used for a couple of water bottles...there is really no place in the front seat to put a water bottle and with a 1000 mile range, you might really need one.

There are two main changes to increase the width of the map pocket.  First, I doubled the width of the spacers (center of the picture) to 3" vs 1.5".  I picked 3" because that was about the size of a decent 16 oz. sports bottle.

Second...since the brace is no longer the same width of the duct, it won't sit on top of the 2" wide heat duct per the plans, it will fit over it with a gap between it and the duct.  So, in order to have it all fit properly, you either have to add height (2.25") to the bottom of the brace triangle so it sits on the floor but maintains the same height or you have to add some foam to the sides of the heat duct behind the seat wide enough for the brace to sit on top of.  I chose to make the brace taller and fill the .5" void on either side with foam.  (Update: I changed my mind during the process and decided to add foam to the sides of the heat duct so the brace could sit on top as the plans intended.)

1/2 of the seat brace showing the map pocket spacers.
(Note again that the seat brace has not yet been
cut back down to plans dimensions yet.)
First the map pocket.  Here are the spacers that form the map pocket laid out prior to floxing in place.  The map pocket is the space in the middle with the opening to the right (front of the aircraft).  This opening will be accessible vertically between the pilot and copilot's shoulders.  Note that in addition to being twice as wide (difficult to see in this picture), I also raised the top of the pocket an additional 2" making it 8" tall vs 6.25.  Looking at the plans, It didn't appear like the taller pocket would interfere with anything.

Detail showing built in wire channel

Wire Channel (TIP)
Look a little closer and you'll see one more thing I did...also picked up from the archives.  There is a double layer of glassed .25" foam at the back of the map pocket.  In the center, behind the glass, I removed a .25" strip of foam and inserted a straw from the bottom up to above the map pocket.  This will make it easier to allow for stringing any wires for a red flood light or intercom up through the brace without interfering with the map pocket.  The straw makes a nice smooth surface that won't chaffe any wires.

Note:  If I were to do it again, I would have made the wire channel .5" instead of .25".  I'm worried that I may not have made enough room for the wires that I might need to go through there.  With a .5" channel I could have used a McDonald's or Whataburger straw...they have a larger diameter than most.

Assembled Seat Back Brace
I give you the assembled seat back brace with a 3" wide map pocket instead of the 1.5" wide plans version.  It's now ready for final exterior glassing, attachment to the heat duct, and installation into Cozy #1606.
Seat Back Brace ready for exterior glassing
(Note:  now it's been cut back down to plans dimensions)

Onward to the heat duct.

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