Chap 8 – Rollbar Cross Bar

I started today by taping up the side rails so that only the area that will lie under the ends of the cross bar was exposed.

Priming front side of side rails

I then shot each side rail with weldable primer.

Side rails primed

I then removed the tape after I had pulled out my chop saw from the back shed & prepped one of the 7/16″ stainless steel bars (that will be used for the aileron weight) to cut 2 pieces 7/8″ long.

Side rails primed

Here are the two 7/8″ long pieces of the 7/16″ diameter stainless steel cut to be inserted into the crossbar as support inserts for the seat belt mounts.  I’ll drill 1/4″ holes through the center of these inserts & weld them into place in the crossbar.

Seat belt mount plugs

Here are the side rails re-inserted after the weldable primer had cured.

Primed side rails re-installed

Primed side rails re-installed

With the side rails completed, it was time to fit the crossbar into place.  I marked the cross bar & trimmed each side a very little at a time.

Trimming crossbar

Here I’m trimming the left side of the cross bar.

Trimming crossbarHere’s the cross bar trimmed & inserted into place.

Crossbar installed

I then mounted the headrest (lower half) back into place with the aft bolts.

Headrest bolted into placeHere’s a side view of the remounted headrest.

Drilling crossbar headrest mounts

I then opened up an extra long 1/8″ drill bit I picked up specifically to drill the front mounting holes for the headrest, that will attach it to the cross bar.

Long 1/8" drill bit

Here’s the drill bit ready to go!

Ready for some deep drilling

I marked the target drill points for the front headrest mounting holes.

Crossbar mounting holes marked

And then used the extra long 1/8″ bit to drill the front headrest mounting holes.

Holes drilled through headrest

Once I had drilled both mounting holes, and confirmed that I had drilled into the cross bar, I removed the headrest.

Headrest removed & crossbar holes

I then drilled out the initial 1/8″ holes to 3/16″, and test fitted the holes with a couple of AN3 bolts.

Crossbar mount holes drilled to 3/16"

I then turned my sights on the cross bar.

Crossbar marked by headrest holes

I drilled the 2 spots I had marked by drilling my initial headrest mount holes with the 1/8″ long bit.

Crossbar headrest mount holes drilled

And repeated the process a couple times with thicker drill bits, ending up with 1/4″ holes.

Crossbar headrest mount holes drilled

I then clamped a K1000-3 nutplate to the surface, and drilled out the first rivet hole.

Crossbar headrest mount nutplates

I then inserted a rivet on the just-drilled side, re-clamped the nutplate & drilled the other rivet hole.

Crossbar headrest mount nutplates

With the right side holes drilled for the headrest mounting hole, I repeated the process for the left side.

Crossbar headrest mount nutplatesResulting in 2 set of holes for the headrest mount nutplates in the cross bar.

Crossbar headrest mount nutplates

Crossbar headrest mount nutplates

I had originally considered using flush mounted rivets but it would have been too difficult, so I simply used Cherry Pop rivets to hold the nutplates in place.

Crossbar headrest mount nutplates

And tested the nutplates by quickly installing a couple of AN3 bolts.

Crossbar headrest mount nutplates

I then mounted the headrest to the cross bar, or I guess at this point in time I actually mounted the crossbar to the headrest.

Headrest mounted to crossbar & seat back

Headrest mounted to crossbar & seat backI placed the top of the headrest back in place and the lower seat back in place as well to get an idea of how the seat back, headrest & rollbar looked up to this point.

Headrest & cross bar mocked upWith everything looking good, it was time to focus on the seatbelt mounts.  But before I moved forward with mounting the seat belt reinforcement inserts, I wanted to verify the positioning of the upper seat belt mounts.

I grabbed the wood mock cross bar & screwed the upper seatbelts to my initial, proposed mounting locations.  I climbed into the fuselage to check the fitting.  All seemed good at first, but after moving my head around & moved around as if I were leaning to each side to look out of the canopy, the inside edges of the seatbelts were scraping the side of my neck.  Not bad, but I decided to move the seatbelt mounting points outboard a mere 0.150″, so I remounted the seatbelts & it seemed to do the trick.  Clearly if I move drastically to one side of the fuselage, I’ll get a belt in the neck.  But for normal ops, moving the seatbelt mounting locations out just a tad seems to worked.  BTW, as I’m sure many of you know, the original plans positions received a few bad reviews for being too far outboard & not fitting so well on the pilot’s shoulders.

Checking seat belt positioningWith my new seatbelt mounting positions in hand, I started drilling the cross bar for the seatbelt mount reinforcement inserts [7/16″ SS bar drilled with a 1/4″ hole].

Drilling seat belt mount holesI got the holes drilled: 3/8″ on top to provide a positive stop for the seat belt bolt & 7/16″ on the bottom to allow for the installation of the reinforcement inserts.  I then test fitted the left side seatbelt mount reinforcement insert.

Seat belt mounting holes drilledThe cross bar from the bottom with one of the seatbelt reinforcement insert in place.

Seat belt mount holesAnd then tested the fitting & look of the 1/4″ seatbolt mounting bolts with their associated washers.

Checking seat belt bolt & washer fit

So I clearly busted my March deadline to finish Chapter 8, but I’m very pleased with the progress so far.  I estimate that it should only take a few more days to finish the rollover assembly.




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