Building fuel tanks... one for Inverted

I'm at the point of adding all the internal details to the LH tank & ribs, fuel transfer holes, venting, fuel cap and the inboard rib. When ordering a bunch of new parts from Vans, I decided that I'd build one tank with the inverted pickup option. I've done quite a few searches and while it seems most build the LH tank with this option one could go either way.

Is there any advantage to having the inverted pickup in one tank or the other? I assume when flying aerobatics you still keep the fuel load balanced as best you can so one wing isn't heavy but does this actually work out in practice? Does the trap door modification to rib #2 keep the fuel in the first bay full? Are there recommended modifications other than what Van's shows in the plans?

For those that built an inverted tank did you add an inspection plate to the second rib bay and mount the sender to that the same way as it's done for the inboard rib? There is absolutely no detail for where to mount the sender in the rear baffle. Anybody have some advice here?

Comparing the -8 tank plans to the -4 it seems Van moved the location for the vent line fitting on the inboard rib. Wondering why and if there is an advantage to making the -4 the same way.

Not your question, but...

Unless you have fuel injection *and* an inverted oil system *and* intend to do sustained inverted flying, using an inverted fuel pickup will add weight, complexity, additional risk of fuel starvation, and $money$.

If all you do is loops, rolls, cubans, etc, there's no need of an inverted system.

If carb'd, the engine will quit as soon as you go negative, regardless of fuel pickup. If injected without inverted oil, it will run past losing oil pressure, even with the standard fuel pickup.

And, there are numerous cases of the flop tube hanging up, causing fuel starvation in level flight.

FWIW....

- Original vent line position would interfere with full up/down flop tube movement.
- Later instructions call for a strap installed vertically to prevent side movement of flop tube to eliminate hang-ups.
- Flap in #2 rib will slow sloshing effect, but will not hold the fuel in bay1
- yes, sender would be mounted in #2 bay, you duplicate the access cover arrangement as used on the side rib, position vertically same as the side rib location, adjusting the float arms will accommodate final sender readings
- be sure to note which direction is 'up' for the sender (matching the other gas tank) when fabricating the cover plate
- a good idea to run a ground wire from one of the sender mounting screws back to the fuselage (as precaution) as would require tank removal later if you had fuel sender grounding issues
- Left tank seems to be the most common flopped, just commonality?

I do plan on going injected with at least a 1/2 Raven (probably full Christen) inverted oil system but to be honest I haven't researched the two options fully.

While on the topic of injected fuel systems, I know there are a few options and ways to go but has anyone had experience with the Rotec TBI system and aerobatics? Seems like a elegant solution for injection. It's so far off though, I just plan on building as future proof as possible right now.

For the baffle mounted sender it looks like it is mounted close to the second rib which would preclude the use of the standard T-708 access plate since it would overlap the rib flange/baffle joint. One could move the sender outward more to clear this but I think that makes the reading of low fuel that much worse, no?? Maybe no one cares since it's already inaccurate.

Yes I can see the lower vent line position on the inboard rib could contact the pickup at the inverted position. I'll be building as per the -8 spec for both tanks, can't see why not.

I put flop tubes in both tanks, now I just fly the way I want.

Flying inverted is so dumb.

Imagine hanging upside down in family room, watching foot ball game trying to drink a beer and snack on snackies with eye balls ready to pop out of head due to high cranial blood pressure.

What exactly is the point?

I knew a pilot years ago who could stand on his head upside down leaning against wall and drink an entire can of beer, how he got it to to up is unknown but I saw him do it.

There are guys here who have had a snack doing positive G stuff, but I don't think anyone has tried it inverted with negative G. Unless there is enemy on your tail with guns blazing, there is no point in doing it. Humans are not designed to live in negative G environment, it turns everything upside down.

Years back I buzzed the Lake Placid ski jump in a T-37, but I didn't get a very good look, so the IP I was flying with took us back around and we made an inverted low level pass so I could get a better look. It was totally cool.