37-01 -> 05: Roll Over Bar

Like every chapter, the Roll Bar starts with prepping parts. The roll bars consist of a forward and aft roll bar, which are each split into left/right parts, held together in the centre by a doubler. This needs to be riveted on, to join the left and right halves of the roll bars, before moving onto the rest of the chapter. So i prepped and primed the roll bars and the doublers before riveting them together, then will shoot a second coat of primer over the roll bars where the following steps (ake countersinking) will occur. 

When riveting the roll bars together, the plans have you cleco the roll bars to the fuselage (to the roll bar bases), then set the bottom outer, and centre upper rivets in the roll bar doublers. You can then remove from the aircraft to finish the rivets off. 

I found that there was a bit of stress in the parts, and they were hard to get aligned well on the aircraft (the clecos on the doublers were hard to get in). I had a lot more success with clecoing the roll bars together on the bench, and inserted a bunch of rivets to help with alignment. I then cleco'd the assembly to the aircraft, and set the required rivets, before removing and finishing them off on the bench. 

The parts cleco'd together on the aircraft.

Not aligned very well - the clecos were hard to get in. Not sure why, but alignment was difficult.

I cleco'd together on the bench, then used as many rivets as i could to aid in alignment..

...before clecoing back onto the aircraft, for setting a few of the rivets.

Oh, and this little rivet represented the 20,000th of the project! 

Once the forward and aft roll bars were riveted together, i added some curve to the roll bar splices by rolling it around the edge of the work bench, to assist in getting it to fit. I was then able to slide on the aft roll bar over the top, and cleco both of them to the splices. All holes were then reamed to #30, and the parts pulled apart and deburred. 

The splice rolled roughly to the shape of the roll bar

The splice clecod into position

Half way through the reaming process

Once this was all put back together, i was able to complete the countersinking of the forward roll bar flanges. This is countersunk for AD4 rivets (as the roll bar splices are riveted to the forward roll bar using solid rivets). 

I had to suicide countersink the ones in the corners.

Checking that the countersinks were deep enough to fit the dimples in the roll bar brace.

To countersink the aft roll bar, i clecod on the aft window shim and this gets countersunk to 120 degrees for CS4-4 pull rivets.

On page 37-06, there is one single rivet hole which needs to be countersunk for a CS4-4 flush pull rivet - this sits underneath the plate which holds the bushing for the canopy locking pin. Since i had the countersink cage setup, and was going to prime the outside faces of the roll bar anyway again, i countersunk this hole now. 

Then all the parts were removed, deburred again, cleaned, etched and primed.

The roll bars got a second coat of primer - to make sure all the new countersinks were painted. 

Riveting Together the Roll Bar

The splice strips were riveted to the forward roll bar using sold rivets. I was able to set all of them using the squeezer. 

The locking pin cover plates were installed into the aft roll bar. The forward plates are installed when the roll bars are riveted to the roll bar bases on the aircraft.

The aft roll bar was then installed over the top of the splice strips, and pull rivets were used to attach it. 

The tiny holes remaining in the roll bar splice will be the drilling locations for the aft window, when it gets installed.

Next, i dimpled then riveted on the side brackets to the roll bar brace

The hole in this location is aligned with the centre screw hole for the aft window - so you can get a nut onto the screw. Clever!

Drilling the roll bars to the aircraft

The final step was to slide the roll bars over the roll bar braces - this was initially slightly difficult, until i realised that the splice strips were sitting up slightly and stopping the roll bars sliding all the way down. Fortunately, there is an access area to allow you to later access to the bolt heads at the bottom of the roll bar bases - so you can get a finger in and make sure the splices are sliding down properly. I used a wooden block and a mallet to make sure they were seated, then match drilled the bases. 

This is why you leave out the last few rivets on the tailcone skins waaaaaay back when - so you can pull the skin out of the way to match drill / rivet the roll bars. 

It is starting to look more like an aeroplane and less like a canoe every day!

Once drilled, i removed the roll bar assembly, and deburred all the parts. I diligently made sure to clean up all the swarf! 

 

Before these can be riveted to the fuselage, i need to final paint them in cockpit color - but it is just too cold in the shed at the moment - so they were added to the ever increasing number of parts waiting to be painted before installation.