8-02:04 - Riveting HS Front and Rear Spars

Once all the primer was dry, i began to rivet the HS rear spar together. I initially clecod the rear spar doubler to the rear spar, and realised i had clecod it on with the wrong face to the spar - it was almost symmetrical, however the rivets fit into the holes much better when i realised and flipped it over.

The rear spar doubler has a couple of AN426 countersunk rivets in the rear spar where the elevator bracket assembly bolts. I decided to back rivet these using my normal tungsten bucking bar, taped into place.

Instead of rivet tape, i use removable 3M tape

Once these were done, i used the cupped set and the tungsten bucking bar to finish all the other spar doubler rivets. There was only one rivet that needed drilling out, and i inadvertently put the shop head on the rear face (which didn't look great). 

For AD4 rivets, i like to drill the head off with a #31 drill bit, then once it is snapped off, i use the #41 drill to drill out the centre of the rivet shank. They tend to just pop out then. 

Once the doubler was riveted on, i riveted on the elevator brackets. 

The final task on the rear spar was to bolt on the centre elevator bearing bracket. This involved torquing the MS21042-3 all metal lock nuts onto the AN3 bolts. This required measuring the "prevailing torque" of a new nut onto a new bolt. To do this i used a beam type torque wrench, and held the bolt head in a drill press vice, that was clamped to the work table. I used a normal ratchet to screw on the nut so that one thread was showing through the nut. I then got the nut running, and read the "prevailing torque" off the wrench. For reference, i also measured the torque from some normal AN365 nylon lock nuts. Below are the results - these values were added to the standard torque values from Van's manual section 5. 

I was then able to bolt the elevator bearing bracket onto the rear spar, and torqued the nuts to 38 in/lbs using a calibrated click type beam torque wrench. I used torque seal to visually show the nuts had been torqued. The bolts went into the holes with a little bit of persuasion, so next time i will use a 3/16" or a 1/4" reamer to finish the holes, instead of a #12 or 1/4" drill. I read that i needed to keep the torque seal off the threads, to prevent galling later if removing the bolts, so i did that. 

Moving onto the front spar, the first step was a number of countersunk rivets in the doubler, where the VS attach bracket will bolt on later, and also where the HS bolts to the aft fuselage attach bars. I was able to fit my large back riveting plate under the doubler, and i used wooden blocks to hold up the ends of the spar. I had to grind down the plastic end on my back-rivet set so that it nested nicely into the spar caps. When i was doing this, it must have put some sideways pressure on the roll pin that holds the plastic end on, which sheared the pins and the end fell off - need to fix that! I used some wooden shims on the bucking bar when doing the lower rivets, to make sure the bar stayed perpendicular to the rivets.  

Backrivet tape holding the rivets in

 

Modified edge to the end of the backrivet set

I use electrical tape on the cupped set as this eliminates all rubbing of the set on the head of the rivet and leaves a nice rivet 

Shims used on the bucking bar so that it remained perpendicular to the tail of the rivet

Shims used on the bucking bar so that it remained perpendicular to the tail of the rivet

All the rivets turned out very well - i was pleased, except for one where i did not keep the set 90 degrees to the spar and got a little smilie on the paint - it did not go through to the aluminium doubler though - so i think it is just cosmetic. 

A little smilie on the rivet in the centre

I then moved onto creating the cradles for the HS skins. This was a simple matter of following the plans and i made a cardboard template of the HS nose and inspar ribs - i traced it about 5mm larger as i was planning to use tape and foam weather seal on the cradles. 

Next up is a lot of HS rib preparation!