How to de-floptube a tank?

szicree · #1 05-13-2008, 11:12 AM

I've now decided that my plane will never need a floptube and am leaning towards switching back to a fixed fuel pickup. I figure I'm supposed to open the tanks anyway for the safety wire thing, so I may as well do it. However, it's been so long since I built them I can't even remember what the differences are. Obviously I would relocate the fuel sender back to it's original location and close the hole in the rear baffle with a solid plate. I seem to remember some hinges, trap doors, and guides that should be easy to put right. As for the actual removal of the flop tube itself, what should I use to plug the hole in the nose of the inboard tank rib? Any other advice would be great.

RV8RIVETER · #2 05-13-2008, 11:26 AM

Seems to me that the easiest thing to do is make a rigid fuel pick-up and mount it in the same position as the flop tube you remove. It would be a simple matter to make the new pick-up tube lay against the bottom of the tank all the way to low point corner. It will be longer and may have to add a small angle or bracket to keep it down (keep it from moving). Can't think of any reason you would need to relocate anything.

You could remove the tap door, but since it not really designed to be fuel tight it is not going to make any difference either way.

**Just saw the RV-4, so your tank may be (probably) is different, but then again .....

ddurakovich · #3 05-13-2008, 11:36 AM

I removed the brass weight and safety wired the flop tube in place, safetied a cap on the fitting in the rib, fabbed a new pick-up tube, and pretty much left the rest alone.

Some 85 hours later, some mild acro, and all is well. If I ever decide to do more aggressive acro and configure appropriately, it will still be there!

N941WR · #4 05-13-2008, 12:44 PM

Why remove it? It should have no impact on your flying or fuel pickup.

I like the idea of safety wiring it in place so your engine will stop if you go negative.

And heck, if you ever want to do inverted stuff, just add the oil system and you are good to go.

rv8guy · #5 05-13-2008, 05:25 PM

I took the flop tube out and bought a fitting to seal the AN fitting at the front.

I left the fuel sender in bay 2, and I added the fuel pick up in the access plate as standard.

This could be reversed very easiily, giving me or future owner flexibility.

Geico266 · #6 05-13-2008, 05:38 PM

Quote:

Originally Posted by N941WR

I like the idea of safety wiring it in place so your engine will stop if you go negative.

Bill, why would you want the engine to stop?

N941WR · #7 05-13-2008, 07:26 PM

Quote:

Originally Posted by Geico266

Bill, why would you want the engine to stop?

Larry,

With no inverted oil system it is desirable to fuel starve the engine rather than letting it continue to run w/o oil. Once you complete your negative G maneuver, the engine will probably restart on its own. If not, hit the button and if that doesn't work, time to practice your glider skills.

If the engine continues to run when pulling (pushing?) negative G's without an inverted oil system you will soon find yourself in a glider anyway, maybe even one that is on fire after the engine grenades.

szicree · #8 05-13-2008, 07:33 PM

Quote:

Originally Posted by rv8guy

I took the flop tube out and bought a fitting to seal the AN fitting at the front.

I left the fuel sender in bay 2, and I added the fuel pick up in the access plate as standard.

This could be reversed very easiily, giving me or future owner flexibility.

I find this to be the most appealing plan. Thanks to all who've responded. For those who wondered why I'm bothering, it's mostly to eliminate one possible failure point, save a few ounces, and avoid the ridiculous challenge of plumbing around the forward tank mount.