Flop Tube Retrofit

I have an RV-8 that does not have a flop tube in either tank. I'd like to install one to increase my inverted time beyond 20 seconds. Is it feasible to retrofit a tank with a flop tube? What would be required? I'm sure I'll have to remove the tank but how much will I have to violate the integrity of the tank to install the flop tube? Can I use the existing float sender or will I have to install a capacitive one?

I'm not a builder but am comfortable with the RV construction techniques. That said, any help from you experts will be much appreciated. And I'd especially like to hear from anyone that has accomplished this change.
Thanks,
Randy

The hardest part is pulling the tanks off. Last time I took my tank off it was to repair a leak at the sump.... since it had been a long time since the build I forgot there was 3 bolts at each attach point and only took 2 out.....

After cursing at the tank....I said duh! Took out the 3rd bolt and came right off


You have to add a couple pieces of metal inside the tank to insure the flop tube won’t get hung up and a flapper to restrict the flow of fuel migration outboard.

A little drilling to add the flop tube, a little sealant and you are done.

If the sender is mounted on the end rib per plans, it must be moved to the next bay outboard and mounted on the rear baffle. Or switched to a capacitive type of setup.

Bob burns
Rv-4 n82rb

sequence musings...

It will be more than a casual effort but it is doable.

• pull the tank, 21 bolts, lots of screws, fuel plumbing, forward spar attach...
• remove tank access panel (you will need to cut the pro seal... use a small, thin putty knife - sharpen the end - work slowly)
• cut away excess access panel as needed to use sender attach holes in the access panel as a drill and cut template (you will need to order a blank cover plate)
• drill sender attach and access hole in the first bay of the baffle using the template (make sure to get the orientation correct)
• cut out center (I think it is a two inch hole to fit the sender through)
• clean up holes, install nut plates, clean out shavings, test fit sender.

through the access hole:

• fabricate, fit, and install the trap door
• fabricate a small plate to cover the center rib hole
• fill / cover other tooling holes
• fabricate anti-hang up brackets (one on the rib and one across the access panel - review tank plan sheet )
• rivet it all up through the access panel (should be interesting but doable with pull rivets)
• drill the flop tube -6 90 bulkhead fitting hole
• clean up shavings

test fit
mix pro seal
install sender, flop tube, access panel with pro seal

wait 48 hours for pro seal cure

leak test tank

re-install

fly

Good Luck!