[sblair]

Hi everyone,

I'm getting ready to drill the #12 holes in the tank Z brackets. I'll use Dan Checkoway's method, but need further definition on one point. I understand I should locate the 3 holes 1/16th in toward the web, except do the opposite on the one inboard bracket.

Where do you measure? The inside of the flange (blue pen) or the other side of that same flange? Taking into consideration the thickness of the vertical part of the bracket, a measurement on the other side seems like it would be centered, then automatically because ofthe thickness of the vertical would be inset toward the web by 1/16th.

Does this make sense?

Thanks

 

[bruceh]

The reason to slightly offset the holes on the brackets is to ensure that you can get a socket on the bolt head when it comes time to torque everything down to the spar. Same goes for getting a rivet puller on the pop rivets that go to the tank on the other side. It is pretty tight in both directions. Don't drill until it is perfect for both.

 

[SeanB]

Which side of the flange should I measure?

Thanks, Bruce. I understand the reasoning for doing the offset. I'm just not sure if the measurement is done on the less wide "inside" portion of that flange, or the greater width "outside" portion of that flange....then offset by 1/16th. It seems that would make a difference to the overall position depending on which I choose.

 

[RV7ator]

I've done four -7s, so consider this.

Centerline the face of each flange, the surface against the baffle or spar. Don't drill holes. Using lots of clamps and clecos, wrap the tank skin around the ribs and baffle like you're making the leading edge then attach to the spar with the leading edge in place. The gap should be almost line to line between LE and tank skins. Remove the LE. Position Z's at two outboard stations. The center lines should fall diametrically through the holes in the baffle and spar, or be very close. Pay attention to the vertical (with respect to the spar) positioning of the baffle so you don't induce a hickey into the airfoil, and keep the Zs symmetrical about the spar and baffle hole pattern. Clamp, clamp, clamp. Drill these. The inboard Z needs to be jockeyed to even the barely visible centerlines; Van's has a dimensional problem here and the centerlines will not be diametric. Drill this bracket when you've accommodated wrench clearance for the three bolts. Remove the skin/ribs, keep the baffle in place, position and drill the remaining Zs.

I can't over emphasize the need to strongly clamp each flange against it's mating surface while drilling and further restrain with bolts and clecos as you drill each hole

John Siebold

 

[David-aviator]

I've done four -7s, so consider this.

Centerline the face of each flange, the surface against the baffle or spar. Don't drill holes. Using lots of clamps and clecos, wrap the tank skin around the ribs and baffle like you're making the leading edge then attach to the spar with the leading edge in place. The gap should be almost line to line between LE and tank skins. Remove the LE. Position Z's at two outboard stations. The center lines should fall diametrically through the holes in the baffle and spar, or be very close. Pay attention to the vertical (with respect to the spar) positioning of the baffle so you don't induce a hickey into the airfoil, and keep the Zs symmetrical about the spar and baffle hole pattern. Clamp, clamp, clamp. Drill these. The inboard Z needs to be jockeyed to even the barely visible centerlines; Van's has a dimensional problem here and the centerlines will not be diametric. Drill this bracket when you've accommodated wrench clearance for the three bolts. Remove the skin/ribs, keep the baffle in place, position and drill the remaining Zs.

I can't over emphasize the need to strongly clamp each flange against it's mating surface while drilling and further restrain with bolts and clecos as you drill each hole

John Siebold

John,

How would you match the brackets to a wing spar shear web in a finished airplane?

I'd like to build new tanks to replace the original QB tanks that continue to have blisters, but have not figured out how to match the Z brackets to the holes in the sheer web.