Chpt 8 - Headrests, Heat Duct & Seat Belts

Home Chpt 7 - Fuselage Exterior



Working on Chapter 17

updated: 01/01/2020


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28/05/2007 I have decided not to follow the plans method for the Head rests and will be fitting standard car head rests.  I feel the plans head rests do not look very good and block access to the rear of the aircraft.  As I'm also considering a forward opening canopy, I will not be installing the side piano hinges as stated in this chapter.  So I will only be making and fitting the seat belt shoulder brace and the rear heat duct in this Chapter.

It has been suggested by other builders that it is better at this point to move straight onto Chapter 9 and make these bits whilst installing the Main Landing Gear and Landing Brake.

Step 1 Carving the Foam pieces 

I used left over pieces of 3/8" thick, blue low-density H45 PVC Divinycell Foam.  Wicks part No. F500-030 to make the shoulder support.  One edge of each piece is cut with a 45 bevel, so that there is a good fit with the sloping seat back.  Trial fit the pieces to ensure that there is a good fit in the fuselage and against the seat back before assembly, trim as required.  I used my trusty nail profile gauge to obtain the correct profile for the notch, that is cut into the front panel, on each side to allow for the longeron.


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As I was going to fit standard car type head rests, I extended the length of the 1 " Birch square inserts to 2", this would gave me enough of a hard point to allow me to drill and fit my headrests.  Approximately 90% of all double bar car headrests in Australia have a common measure of 140mm centre to centre between the posts. I obtained a couple Toyota Camry headrests and the guide tubes from the inside of the car seat, from a local scrap yard dealer for $20.  I marked the centres for the posts and carried these down onto the front seat back.  


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Using basic trig I obtained the point on the front seat, on which the Headrest support posts would line up with when vertical and then drilled 3/4" holes in the front seat to match the 4 aluminium 3/4" x 1" long 6061-T6 pipe guides. The holes do not carry on right through the seat, but stop just inside the fibre glass layer on the back of the seat.  The ends that went into the seat back were bevelled at 45 to match the angle of the seat.  Once I was happy with the fit, I floxed the tubes into place and reinforced the bottom of the hole with a little extra flox.  The photos show the headrests fitted loosely with the plastic guides, which will be floxed into place once the shoulder support is installed.    


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I followed the recommendations listed on the Cozy Builders Mailing List FAQ and riveted the 1/4" Nutplates to 1" square aluminium plates and then floxed the squares onto the underside of the Birch ply inserts and secured the plates with 2 small screws.  I also pre drilled the 1/4" holes so that I could line the Nutplates up using a 1/4" bolt.  I did not drill the 1" hole under the left longeron & seatback, as I'm still unsure on how I'm going to fit and lock the latch for my forward opening canopy. 


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Step 2 Glassing the Inside Surface for Wet Layup

Before installing the single BID ply to the inside of the shoulder support, I measured and fitted the guide tubes for the Headrests by drilling matching holes in the shoulder support birch inserts as well as into the front of the Seat back.  The guide tubes pass through the shoulder support holes and locate and lock into the holes in the front seat.  Once I was happy that everything lined up OK, I then floxed the 4 x 1 " nutplates into place following the instructions below, which I obtained from the Cozy Builders Mailing List FAQ :-


"1. Build your nutplate, aluminium, riveted, thing-a-ma-bob (Is that spelled correctly? :-) ).

2. Sand the mating surfaces for good bond.

3. Drill through the wood.
4. Insert your screw through the wood and screw the nutplate on the screw.
5. Flip the whole thing over (nutplates on top).
6. Flox between mating surfaces, and use the screws to pull the nutplates down tight.
7. Let the whole thing cure and remove the screws. My screws had a little epoxy left on them so I dumped them in MEK over night and they came out clean.
8. Put some duct tape on the bottoms of the nutplates and drip candle wax into the screw holes. Remove the duct tape. Mount the shoulder support.
9. Do the 12 ply lay-up then the 2 ply overall. The holes are visible through 2427 epoxy. Carefully drill them out insure you don't go down to the threads. The wax keeps the epoxy out of the threads.
This is really easier than it sounds."


The shoulder support was then fitted and glassed as per plans.  Remember to add the 3 additional 4" x 13" UND strips across all 4 seat belt hard points. The next day I re-drilled all the 1/4" holes and fitted the headrests.   


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Step 3 Installing the Outside Seat Belt Attachments

I found that the instructions in the plans for making and fitting the reinforcements was not very clear and I had to do a little research on the Internet, before I was finally happy to proceed.  As I was not fitting the plans external step I made all 4 reinforcements the same size, " thick birch plywood x 2 5/8" long x 2" wide.  The measurements for the location of the inserts are given in Fig 10, on page 2 as 5" from the front seat, for the front 2 and 8" for the back 2.  But the drawing is not clear whether this is to the edge or centre of the insert.  I assumed it to be to the centre of the insert.  The inserts were individually shaped to suit each location along the longerons.  The sides were also tapered to allow the glass to lay down properly. After sanding the sides of the fuselage and inserts, they were floxed into place and the edges smoothed.  The 7 plies of BID used on each insert were cut into squares 5" x 5" and were first laid up on the worktable, on grease-proof paper, before being moved to the fuselage and placed over the inserts.


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I left the drilling of the holes through the seat belt inserts until the 2" long seat belt brackets were made from 1/8" x 1" x 1" 2024T3 aluminium angle.  I used an 18mm radius to round the top of the bracket and drilled all the holes using a 1/4" bit.  The seat belt inserts, front and back were then marked and drilled, the brackets were sanded and floxed into place. 


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Step 4 Heat Duct and Centre Seat Belt Attachment

This step is basically a repeat of what was done to create the front heat duct and you need to refer back to Chapt 6, pg 5, fig 22, 23 & 24 for instructions.  I started off by making a cardboard template to pickup the profile of the fuselage bottom and correct lengths for the aft heat duct and marked these sizes out on left over 1/4" x 4.5lb last-A-foam from Chapt 6. Wicks part No. F400-005.  I made the transition piece at the same time as per plans and used electrical tape to cover the foam.  The length of the round section is not specified so I guessed that a 2" section should be long enough.  The BID was cut as a single piece, long enough to rap around the foam twice.  The BID was wetted out on plastic first and then rapped around the foam and finished off with Peel Ply. 


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A 2" long section of 3/8" ODx0.065" 2024T3 aluminium pipe was cut and floxed onto the top of the heat duct, 8" fwd of the fwd landing gear bulkhead.  The 7 ply lay-up was applied as per the instructions in Chapt 6, pg 5.  The final 2 ply BID lay-up was then applied.  After cure the heat duct was floxed into place onto the fuselage bottom, along with the baffle piece at 45 and all joints taped.


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The fuselage bottom and heat ducts were then sanded with 36 grit sandpaper and the final 7 ply lay-up (4" wide 4 BID & 3 UND, alternating and extending onto the fuselage bottom by approx. 6" on each side.  This was completed for both the front and back seat belt attachment points.  The widths and lengths were altered slightly to minimise bumps and finished off with Peel Ply.  After cure the 1/4" holes were re-opened.  I really battled to get the 7 layers to lay down over the 3/8" OD aluminium pipes and just couldn't get the air out.  I eventually used cling wrap over the peel ply and this stopped the lay-up from lifting.  If I did this again I would do the lay up one layer at a time, straight onto the centre heat duct.


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 Finished this Chapter on 20/06/07.


Onto Chapter 9