Breaths tube?

Good afternoon,
It needed two breaths tube in the tank acrobatic?
In inverted flight you need one?
Tks

I'm not an expert but there is only a need for one "breather tube" (aka tank vent) for each tank. For aerobatics, you do need a different type of fuel pickup (aka flop tube) that will keep fuel flowing when inverted (same for oil in the engine, depending on what you plan to do).

Not sure what you are asking.

I am not sure what it is that you wish to use one of on an RV-8. The two tank vent lines are put in with a pee trap type shape to keep fuel from backing out of the tanks when you get up-side down or almost any attitude.
Both tanks get there own separate vent line to the main tanks. You will find this all in the plans.
If you wish to put in a flop tube for fuel pick up in most attitudes you can put one in each tank or as most do just put one in and a standard pickup in the other tank. The standard pick up will draw down to almost the bottom of the tank before you lose fuel pickup. The flop tube will set up a little higher and not lose its draw close to the bottom of the tank. We only put one in as most people will not like to hang in the straps more than 15-25 seconds. It all come down to what you want to do. And what you can stand to do..
Not much but hope it helps.. Yours as always, R.E.A. III #80888