Z-Brackets drilling

I decided to follow the advice of many builders to go the Checkoway method for attaching the z brackets. I know this is not the vans manual way but didn't like the idea of elongating the holes

As described in his method on many sites, when making the first holes in the Z brackets for the AN3 bolts, I made a center line on the outside flange (outer side that leans on the spar) and made an offset of 1/16" towards the web.

When matching the tank baffle in a preliminary attempt to mate it, I see that on the other side, the holes for the pop rivets will be pretty close to the edge of the z bracket and are below minimal edge distance.

I only have like .220 to .230 of edge distance from center of hole to edge for the pop rivets to go.

Is this still ok for strength ? or would you guys replace the brackets and go the normal centered way ?

Have any of you drilled the same way with the offset and had a different result on edge distance ?
Just wondering what I'm doing wrong.

Jurgen,

I don't recall Dan's method, but the Van's method definitely causes problems. I don't like the notion of slotting, either. There's a way around that. Then there is a Van's dimensional mismatch at the root end bracket. I just finished fitting my 9th tank, so it's fresh in my mind.

Use bolts for spar attachment. Clecos are too weak for restraint.

For the six outer brackets, drill one 3/16 hole centered on the flange. Bolt, BOLT, it to the spar (plain nuts are fine), align the length-wise centerline through the outer holes, tighten the bolt and drill the other two holes. (I like to make a center mark with the drill then remove the brackets to finish drilling on a drill press.) Reinstall the brackets using bolts at each end. Lay the baffle on top of the brackets. Overlay the tank skin with all ribs but the root rib installed and cleco the skin to the spar and the baffle. This positions the baffle where it naturally picks up the pre-punched holes. No slotting required.

At the root end, cram the 7th bracket into position. Clamp, clamp, clamp, so it is completely flat on the spar. You will see that you need to move it in or out for a best position compromise. The centerlines will not ever line up on both spar holes and baffle holes. It's best to favor the bolt holes as you need hex head rotation clearance from the web. This bracket does not get plate nuts. Drill bolt and rivet holes, and reassemble using bolts in the spar and clecos through the baffle.

Remove the leading edge. (You could drill the joiner strip to the tank skin before doing this.) Drill the tip-end tank bracket to the baffle while it's still restrained by the tank skin. Cleco in place. Now you can remove the skin/ribs and drill the remaining brackets. No slotting required. You'll see that the baffle holes are very nearly centered over the bracket centerlines.

John Siebold

So I f I understand well... you did not move away from the centerline like it has been suggested on the chekoway related sites when drilling the first AN3 bolts.

on those sites, it says that the reason to do so is to provide clearence for the poprivet tool on the outboard and inner z brackets and to provide clearence for a wrench on the most inboard brackets.

so does that mean that even though the an3 bolts are center lined, the pop rivet tool can still easily reach for those pop rivets holding to the tank baffle ?

I believe this is one area where I had to use my special pop rivet tool that was grinded down on the out edge....my bench grinder did this in seconds. I'll see if I have some pics in my folder.

This is an instance where you're better off modifying the tool rather than the airplane. I purchased a puller with the smallest diameter nose I could find. Then I cut away a large portion of the nose, even to the point of exposing the works inside. This gives you sufficient clearance for a straight-on pull.

The flaps have even less room for a puller during part of their assembly. You'll appreciate the modified tool elsewhere during the build.

John Siebold