I have decided to install a flop tube in the left tank of my RV-8QB. So far so good. I've installed the fuel sender, the trap door hinge and the flop tube guides. What I need assistance with is installing the actual flop tube. The problem. What do I do with the large thick coating of Proseal that is on the inside of the tank where the hole is to be drilled for the tube. I can't tighten the 90 deg bulkhead fitting that must go through the hole with all the proseal there. I'm obviously concerned about leaks if I mess up the reseal as there isn't much room in there. Secondly, the plans call for locating the hole 1 1/16" from the leading edge. This location might not be the best to avoid disturbing the rivets that hold the T-405 wing attach angle to the wing. Anybody invented this wheel yet?
Van's Air Force
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RV-8QB Flop Tube
- Thread starter Rv8Medic
- Start date
No easy way to do this that I know of. Take note that I am not flying yet! I drilled the hole for the fitting using a step drill and then cut away the pro-seal by peeling up a small amount at a time then cutting while reaching in through the access. Once the fitting sat flush I used tape over the open end of the fitting , filled the inside area with fresh pro-seal and pushed the fitting through from the inside. I added some more pro-seal to the outside and put on the nut. I smoothed out the pro-seal on the inside. Note: After sealing the tank and curing, I rinsed out the tank with 2 gal. of 100LL several times to get all the chips out. I filtered the same 2 gal. through paper towels in a funnel to remove chips and it took 10 times to get fuel with no chips. I left the fuel in overnight to check for leaks. Caution: shaking the tank to get the fuel around the inside built up a lot of vapor pressure, the first time I removed the cap it shot 4 feet up. But the tank holds pressure!
I drilled out the hole with a 9/16 drill bit I picked up, then scraped the area where the fitting will seat with the good ole finger nail and a razor blade. To ensure no leaks, scratch up the sealant left behind with a metal bristle brush to give the sealant something to grip to then MEK it. Wet install the fitting and put a thin coat over it and the roughed up area on the inside. To reach in the tight space between the leading edge and the fitting I bent an acid brush to reach in there. You will have fun with all of this as it will require you to do it all with a mirror and a flashlight taped to the rib so you can see what your doing. I pressure checked my tank to 1.7 psig for 6 hours and no leaks. Good luck.
I would make 100% sure you actually want the flop tube first.
Based on my research, it seems like you only need it if you have an inverted system ... basic aerobatics should not uncover the standard pickup.
Keep in mind that there is a 5 year replacement recommendation on the flop tube ... I now wish I hadn't put one in my SB wings, since given the pace of my project I've already passed 5 years since install, and am not anywhere close to flying! Now I get to open the tank back up...
Sorry to be a bit off topic, but something to consider.
Based on my research, it seems like you only need it if you have an inverted system ... basic aerobatics should not uncover the standard pickup.
Keep in mind that there is a 5 year replacement recommendation on the flop tube ... I now wish I hadn't put one in my SB wings, since given the pace of my project I've already passed 5 years since install, and am not anywhere close to flying! Now I get to open the tank back up...
Sorry to be a bit off topic, but something to consider.
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I guess this is something I need to work on.
I could have sworn there was ... Let me look around and check. Napping before a night shift now.
Quick search shows that some people are replacing them at 5y:
http://www.vansairforce.com/community/showthread.php?t=64460&page=2
Quick search shows that some people are replacing them at 5y:
http://www.vansairforce.com/community/showthread.php?t=64460&page=2
I corrected my original post ... for some reason I thought Van's had a bulletin about it, but it looks like a recommendation from others based on experience:
http://www.experimentalaero.com/flop_tube_alert.htm
Sorry for creating confusion...
http://www.experimentalaero.com/flop_tube_alert.htm
Sorry for creating confusion...
Robert Anglin
Well Known Member
Out on the lim..tube
I will go out on a branch here with this one, but. You would have to go by the recommendation of the "O.E.M." to be safe. The old rubber hose flop tubes would go maybe 8-10 years before starting to get stiff, so 5 years in service would sound about right on them. The last flop tube I got from Van's was made up with AE701 and that stuff is, are I should say I have seen it go 15 years in service with no problem. I would and do have it set to be checked for replacement after 10 years in service.. but will expect it to still be flexible and have only lost the little "O" ring off the billet end pick-up. We did not know how good it was going to be with these newer Teflon stainless hoses, but this stuff will spoil you. Hope this helps Yours as always R.E.A. III #80888
I will go out on a branch here with this one, but. You would have to go by the recommendation of the "O.E.M." to be safe. The old rubber hose flop tubes would go maybe 8-10 years before starting to get stiff, so 5 years in service would sound about right on them. The last flop tube I got from Van's was made up with AE701 and that stuff is, are I should say I have seen it go 15 years in service with no problem. I would and do have it set to be checked for replacement after 10 years in service.. but will expect it to still be flexible and have only lost the little "O" ring off the billet end pick-up. We did not know how good it was going to be with these newer Teflon stainless hoses, but this stuff will spoil you. Hope this helps Yours as always R.E.A. III #80888
