Chapter 21: Fresh Air Vents for Rear Seats

(This is not covered in the plans.)

I decided to fresh air vents for the rear seats in case I actually carry passengers back there some day.  I'm using some pre-molded NACA vents available from Wicks or Spruce.  A thumb-screw opens or closes off each vent.   installed them on the underside of each strake at roughly the same FS location as the rear control blocks.  This location is adjacent to seatback.  I cut the holes while the plane was upside down.  After flipping the plane upright, I trimmed off most of the mounting flange around each scoop.  I cut through the inner skin and hogged out the foam to to form a pocket for the NACA scoops to fit into.  I applied some wet flox to the exterior skin and pressed each scoop into place. 



I made the air boxes by making a pattern, then shaping some blue foam, then glassing the shapes with 2-BID.  Vacuum bagging would have done the trick here.  But if you lack that equipemnt, you can make BID conform to practically anything with enough persuasion (i.e., mixing sticks, clamps and peel ply). 



After only one day, I decided that these air boxes had to go.  While I was proud of how they turned out, they were not what I was really after.  They sit up too high and could be damaged by stuff thrown into the strakes.  I wanted something lower in profile, so I went back to ground zero and started over again.  As you can see in this conceptual sketch, the eyeball vent itself basically sits on the exterior strake skin and the new air box is formed over it.  Simple concept, but it was tougher to build.  There was no simple way to shape the air box form outside of the plane. It had to be done in place.  So I hogged out a bigger pocket aft of the vent for the eyeball vent to fit into.  I taped up the eyeball vent with electrical tape (for mold release) and I shoved some play-do into the NACA vent to seal it off.  I then mixed up some pour foam and poured it into the pocket.  Once cured, I carefully shaped the foam and glassed 2-BID over it.  The new air boxes are alot smaller and they are what I was looking for.    The next steps are to glass the pocket I hogged out, then paint the pockets and the insides of the air boxes.  This is the last chance I have of accessing these areas once the air boxes are permanently mounted.