Flop Tube Install in pre built tank

[andrewbutler]

I am installing a flop tube in a pre-buillt tank for an RV-7. I was wondering if anyone had any general guidlines for doing this? I have drilled out two AN470 rivets to replace with AN426 in the tank attach angle. I also need to drill a 9/16 hole for the AN elbow.

Can anyone tell me where I can get this size drill bit online? My set maxs out at 8/16ths. I am unable to buy imperial sized bits in Ireland.

Also, what is the correct procedure for attaching the flop tube to the tank/elbow with regards dealing with the bucked rivets protruding on the inside of the tank attach angle/reinforcement plate?

[sf3543]

For the 9/16 hole, use a step drill, unibit, to drill out to that size and then use a round file to enlarge the hole where the unibit didn't go all the way through. (You will get a stepped hole because the step on the bit won't be thick enough to cut the entire depth of the tank skin and the angle bracket.) I sdid it this way and it worked out fine. Very quick. Be careful not to over drill and get an oversized hole.