Fuel Tank Gasket and Tooling Hole

[tgmillso]

So, I've just lined up and cut the hole in my inboard tank rib, centered to perfection. I then aligned the T-708 access plate with the vertical stiffener bead, aligned the T-407 stiffener ring beneath the plate to ensure the holes lined up, drilled the #19 holes for the #8 screws, removed the access plate and drilled the #40 stiffener ring holes. Then in all my amateur aeroplane building wisdom, decided to countersink the rib and use NAS1097AD3 oops rivets to hold the rib/stiffener/nutplate combination together rather than dimpling the 0.032 rib and countersinking the stiffener plate. Van's says to rivet it now without proseal, but I can see that the tooling hole is in a compromised position (1/64th from the edge of the gasket). Looking on the forum, the suggestion is to put proseal in the hole, however being a Proseal virgin (apart from the trailing edge applications) my question is, should I fay seal the this stiffener ring first, then attempt to wet rivet my oops rivets once this has set up for a day or so, or should I just do it all in one hit? I guess I'm just a little paranoid given that the last thing I wan't in my tank to leak. Also, has anyone successfully used NAS1097 rivets in this application, or am I going out on a limb here? I just thought it may give better sealing than dimpling in this situation.

 

[Lemmingman]

It looks like on yours you match drilled the tooling hole. I did not, I simply installed the ring and prosealed over the tooling hole.

 

[wirejock]

Seal and rivet

My vote is fay seal and rivet. You're going to seal the inside anyway.
Seems like you can set a big rivet in the tooling hole but it's been a while.
I used sealed floating nut plates.

 

[tgmillso]

Thanks guys. Not an ideal situation, and I should have thought more about this tooling hole before I pulled the trigger on following the instructions and aligning with the vertical stiffening bead. Per your advice, I think I'll go ahead and fay seal, then wet rivet. For the tooling holes that I'm supposed to put the AN470AD6-XX rivet in, I discovered (again thanks to the forum for confirming this) that they are not included in the kit. I called Van's and they don't even have any in stock. Joy. For those in Australia, I found that Aircraft Props and Spares out of Moorabbin had a few, so I'm OK. Just a little frustrating that Van's don't include these, as they're not something you have laying around the shop.
Thanks.
Tom.

 

[wirejock]

Big rivets

Thanks guys. Not an ideal situation, and I should have thought more about this tooling hole before I pulled the trigger on following the instructions and aligning with the vertical stiffening bead. Per your advice, I think I'll go ahead and fay seal, then wet rivet. For the tooling holes that I'm supposed to put the AN470AD6-XX rivet in, I discovered (again thanks to the forum for confirming this) that they are not included in the kit. I called Van's and they don't even have any in stock. Joy. For those in Australia, I found that Aircraft Props and Spares out of Moorabbin had a few, so I'm OK. Just a little frustrating that Van's don't include these, as they're not something you have laying around the shop.
Thanks.
Tom.

Tom
Don't fight those big rivets. Put the factory head on the inside with proseal and squeeze them so they are tight then seal the head when you start sealing the tank.

 

[Z-EDD]

Tom, bear in mind the rivet in the tooling hole is only one option. Fine if you are a serial offender and happen to have the correct rivet lying around. I did not so I just riveted a piece of scrap over the hole using a couple of -4 rivets.

Regarding the inboard rib, I believe that using sealant now is a waste of time. Your tooling hole looks to be very close to where mine was. In which case the T-708 should cover it comfortably. When you close up the tank you will plonk that cover plate on with a thick layer of sealant that will cover all those rivets and the tooling hole quite comfortably.

Try not to stray too far from the instructions on the tank, it all works out pretty well the vans way.

 

[tgmillso]

Thanks Larry. Good call on the factory head inside. I've asked the guys at Aircraft Props and Spares to send me some "A" versions instead of the "AD" if they have them to make the squeezing easier, but I gather they don't need so be squeezed to normal specs, given that they're just there to stop the flow of fuel.

T.