What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Flop Tube

Kwright

Kwright

Active Member
I’ve opened my fuel tanks to remove sloshing. My Inspector pointed out that the flop lube, probably rubber, is subject to a life limit and therefor it would be a good time to replace it. So I went to the local hose supplier who stated that hose for fuel is not rubber. So if it’s not rubber is it still life limited?
 

Attachments

  • IMG_0327.jpg
    IMG_0327.jpg
    295.5 KB · Views: 187
It looks like Aeroquip hose with the stainless steel braid, but I don't know what it actually is made of. If you have that access plate & pick-up all the way apart, I'd be tempted to replace the flop tube while you're there. It's cheap insurance. At a minimum, you need to install the brown O-ring that fits onto the weighted end of the tube. Not sure if you took it off or if it fell off, but you need to account for its whereabouts. If you didn't take it off, it may be hiding in the dark recesses of the tank.
 
It is a Aeroquip 701 hose, or a mimic of one. RUBBER liner and is life limited. Teflon, which is better, unfortunately doesnt work well for a flop tube. Its stiffer, and has a 'memory', so it doesnt move well, without a live swivel.

Tom
 
Kwright said:
I’ve opened my fuel tanks to remove sloshing. My Inspector pointed out that the flop lube, probably rubber, is subject to a life limit and therefor it would be a good time to replace it. So I went to the local hose supplier who stated that hose for fuel is not rubber. So if it’s not rubber is it still life limited?
Click to expand...

It IS rubber and DOES have a limited life. I resealed a tank this spring and that hose was hard as a rock. It had taken a set and therefore pulled fine when upright, but if you turned the tank upside down, the hose only went half way to the other tank skin. I meant to post a warning to others out there and forgot to do so.
 
Sage time frame

Specifically for Tom .. but anyone … I’d there a reasonable calendar time frame to apply here ? Thanks. Stew
 
Stew----Normally 5 years in service. But understand, we assume the hose is submerged in fuel, and we dont know the additives in the fuel. But we do know that whatever those additives are, they deteriorate the liners. In Larry's case, it made the hose very stiff, so it wasnt going to flop.
Teflon would be fabulous because the liner doesnt deteriorate, BUT its pretty stiff as is, and doesnt flop well. WE messed with a live swivel fitting several years ago, and it worked, but wasnt cost effective.
So right now the best solution I can say is to change the flop tube every couple of years. Yeah, I know, its a pain to reseal the tank. but until a better alternative comes up, I guess thats what has to happen.

Tom
 
Seen it done it

I recently re-sealed a local set of RV-4 tanks from an older RV-4. It had flops in both tanks, of the standard Vans issue from what I could tell. Both had become so stiff they they wouldn't come close to touching either upper or lower skin and likely left 2 gallons or more of unusable fuel. Both were missing the brown O-ring which keeps them from chaffing the skins. I replaced both of them with new from Vans units, and I surmise the O-rings were either never installed, or completely deteriorated as I could find no sign of them anywhere in the tanks. When I built my -4, I didn't put flops in because I'm not set up for inverted, and I'd recommend anyone to eliminate flops if not planning for inverted flying..just my 2 cents...don't forget to follow the safetying of the B-nuts per instructions.
 
Question.. how much sustained inverted flight do you do? That's the only reason for these flop tubes. I installed one when building the tanks, but later removed it because I realized I never, and will never, actually make any use of it. Simpler to just have the regular, fixed aluminum pickup tube.. no lifespan issues or other maintenance required.
 
Last edited:
You must log in or register to reply here.
Back
Top