Friday, September 14, 2012

Juggling Act With Attach Brackets

Priming of most of the tail cone components was completed yesterday, so now the tail cone assembly begins in earnest beginning with the F-1211D attach brackets. The F-1211D attach brackets come with holes that are purposely undersized for a grommet that needs to be pressed into each bracket. The fit is so tight the grommets won’t even start going into the holes with hand pressure alone.  In Van’s plans a suggestion is given for using a C-clamp with a socket on the backside of the bracket to press the grommets into the brackets.

Anybody watching me would have received quite a chuckle as I fumbled around trying to get a C-clamp, socket, bracket with hole and grommet all lined up with only two hands when four were required. Needless to say, it was a juggling act that quickly morphed into a comedy of errors.

Not having any success, I decided to take a break for a few minutes and think about what I was doing … which was working harder but not smarter. Finally, a moment of clarity … why not let the aft bulkhead hold the brackets for me. Duh! Using Van’s suggestion in the plans for a C-clamp and socket worked great … once the aft bulkhead was holding the parts for me.
                                  The socket and C-clamp pressed the grommet into the holes easily. On the left,
                                  below the C-clamp, is what the grommet that gets pressed into the holes looks like.

Once the grommets are pressed into the attach brackets, they are Clecoed onto the bulkhead assembly for riveting along with the tailskid bracket and eight nutplates. Van’s calls for a few pop rivets to be used where it is hard to reach the rivets without various yokes for the squeezer. However, I could reach all the rivet holes with the yokes I have so was able to squeeze solid rivets into all the aft bulkhead's rivet holes.

Two sizes of rivets are called for riveting the attach brackets … discovered the plans call for the wrong size of rivet where the attach bracket rivets go into the bulkhead/bulkhead doubler assembly. The plans call for a AN470AD4-4 which is just to short and should be a AN470AD4-5 instead ... even that is slightly to short for the “perfect” rivet.  (The longer rivets called for where the attach bracket rivets also go through the tail skid bracket are OK). The shorter rivet is enough to hold that bracket but the longer rivet makes for a much nicer squeezed rivet.
                                                             Riveting the tail cone’s aft bulkhead assembly.

Admittedly, it took a lot longer than I had expected, I figured a couple of hours. However, it was closer to four hours because there is the need to constantly change the squeezer yokes and rivet sets and readjust for all the different sizes of rivets used … plus some of the rivets are flush as well.
                                               Finished tail cone’s aft bulkhead ... outer facing side.
                                                      View of inner facing side the tail cone’s aft bulkhead.