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F996C countersunk bolt holes

A

alpinelakespilot2000

Well Known Member
Mike Hoover and Bill Repucci gave me some great help earlier in this step, but I forgot to ask this question...

Any suggestions for how to address the F996 fuel tank attach reinforcement angle's use of 3/16" countersunk bolts where they attach to the longerons.

Would it be best to dimple the outside skin for the bolt and then countersink the longeron under it? Do I need some sort of larger dimple die? (I think I had to do this on the rudder counterweight but, if I remember correctly, I used a #8 dimple--because that's the largest I had--for the skin and then I countersunk the lead a little deeper allowing the 3/16 bolt to suck the skin into the countersink.) It turned out good on the rudder, but is this the approach here at the tank/fuselage intersection?

Regardless, it seems like I need to take this step now before riveting things together, but the instructions are very vague at this point.

Thanks.
 
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On my QB7 . .

On my QB 7 I didn't have a choice so just countersunk the skin and longeron and it looks fine.

HTH
 
You can drill the holes now while your fuse is upside down. It'll help with getting the chips out. Countersink thru the skins and longeron until the bolt sits flush with the skin. The plans have you do this step just prior to installing the gear mounts.

Steve
checking and re-checking wing sweep/incidence
 
Countersink skin and longeron.

Look at the print carefully, if memory serves, you will see a cross-section view of that bolt hole showing the countersink of skin and lower longeron after they are riveted together. That was how I did my RV-9A. You can see the screws in place for the first time in the first photo on this page: http://www.n2prise.org/rv9a026.htm

You can see these two same screws at the bottom edge of the fourth photo on page 27. One more photo shows them in the seventh photo on page 32 where you see the fuel line and vent line sticking out the side of the fuselage.

Jerry K. Thorne
East Ridge, TN

RV-9A N2PZ, 172.7 hours on the Hobbs meter.
First annual inspection coming up next week.
 
Steve,

Here's another item to consider while upside down. Drill the 4 holes, 2 on each side of the fuse, for the forward gear attach leg now. These holes are about 1" apart and the forward hole is hidden behind that vertical rib (p/n?)which may not yet be riveted in your case. I had to first eyeball and drill an access hole through the inside flange of the rib before backdrilling through the gearleg flange. These holes take the same countersunk bolts as the tank attach plates.

Steve
 
Steve said:
Steve,
Here's another item to consider while upside down. Drill the 4 holes, 2 on each side of the fuse, for the forward gear attach leg now. These holes are about 1" apart and the forward hole is hidden behind that vertical rib (p/n?)which may not yet be riveted in your case. I had to first eyeball and drill an access hole through the inside flange of the rib before backdrilling through the gearleg flange. These holes take the same countersunk bolts as the tank attach plates.
Steve
Click to expand...

Thanks Steve--at first I was going to mock you since I'm building a tailwheel and don't have to attach the gear weldment to those four holes. :D I'll have to look to see if the TW version has anything special there. At the same time, however, I realized that I do have a triangular bracket (F7114, I think) that serves the purpose of tying the F904 (with the spar bolts) to the lower longerons (which the tri-gear folks have to use as well for the weldment). Definitely sounds like it's time to drill those holes now through the side and bottom skins and lower longeron.
Thanks for the heads up.
 
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