<January 8, 2006>
Started Right Tank & Z-Brackets
A good day in the shop today! I was able to get my first tank clecoed together, among other things. Clecoing the tanks together is a pain in the butt, but I managed to figure it out. I discovered that building both wings at once takes a lot of clecos. I started with 400 silver clecos but had to order 200 more this week. Fortunately, a local builder was nice enough to lend me some clecos so I could keep building while waiting for the order.
After clecoing the tank, I turned my attention to the right z-brackets. For these I used the Dan Checkoway method and it seems to be working great so far. You can read more about it on his web site, but Dan devised a method of drilling the z-brackets that almost gaurantees perfect alignment of the tank to the wing. Thanks Dan!
I started the day by enlarging and centering the holes for the tie down rings in the leading edges. I used a small round file the enlarge the hole while making sure I didn't hit the threads in the tie down brackets.
I forgot to take pictures during assembly but here is my first tank clecoed together. At first I tried to follow Van's instruction for the leading edges on the tanks (cleco the top then the bottom) but I found to almost impossible to get all the clecos in that way. Instead, I discovered that if alternated between top and bottom, it went together much easier. To install a rib, I would put a cleco in the forward hole on top, then the forward hole on the bottom, the the second hole on top, then the second holw on the bottom. I would do this for about the first three to four holes, then just complete a side before completeing the other.
Sorry, I didn't take more pictures of the Checkoway z-bracket process, but I started by drawing a line down one flange of each z-bracket, offset 1/16" from centerline toward the web. I did this for all but the inboard bracket. Offsetting the line on the flange that will get the nutplates will give you more room to fit the rivet-puller when you rivet the other flange to the tank baffle. Clear as mud? I then drilled a #12 hole in the flange I just marked, on the line and centered lengthwise. Using some throw away AN3-4A bolts, washers and nuts, I squared each z-bracket to the spar and bolted them in place (pictured here). WHen I checked from below, I was able to see the line I drew on the z-bracket flanges centered in the other holes in the spar, so I knew they were was square to the spar. After all of this I back drilled the remaining two holes (upper and lower) in the z-brackets through the spar. Easy enough!
For the inboard bracket, I drew a line offset 1/16" away from the web. This is oppisite from the other brackets where the line is offset toward the web. Offsetting the line and thus the holes away from the web will alow you more room for the wrench for the bolts that bolt the bracket to the spar.
After the z-brackets were drilled, I used some spare nutplates (of the same size) as a jig and drilled the holes in the flanges to accept the nutplate rivets. All but the inboard bracket get nutplates. The nutplates for the inboard bracket get riveted to the spar, not the bracket.
I installed the z-brackets back onto the spar and fit my tank on the wing. This looks so cool! I was tired, and my back was killing me, so I called it a night.