IronDawg

IronDawg

Member
I am getting close to sealing my tanks. I'm fitting my ribs with everything for future flop tubes and have been wondering if anyone has ever tried adding an inspection plate on top of the tank for flop tube inspection and replacement. I couldn't find anything in the forums.

Thanks,
Jeff
 
I'm thinking the same thing... I got word from Van's (last week) that a "reasonable" service life of the flop tube is 5-8 years. I plan on putting this on the 36 or 48 month replacement schedule. But I was thinking of putting an access panel(s) in the rear baffle (like Dan H) for a couple reasons. Its hidden & to allow access for better sealing of the rear baffle. I really wonder what other's input / ideas will be on this topic. I've heard the flop tube is not too hard to replace without any additional access panels. But I'dont know for sure. I'm not hacking on the tanks (yet).
 
I inspected both of my "Flop-Tubes" when I did the inspection and work for SB 06-2-23. The "Flop-Tubes" were 10-1/2 years old with over 2,082 flying hours. The old "Flop-Tubes" were inspected by my A&P and found to be in the same condition as the new ones that I had purchased for replacement. I left the old ones installed and sold the new ones on VAF.

Note: I am my A&P.
I do not like people changing A&P to mechanic as that degrades the A&P who spend time and effort getting the LICENSE and making them worth no more than a back yard grease monkey that calls themselves a mechanic.
 
If you are planning on putting a plate on the rear of the tanks you will have to remove the tank, so instead of making more work why not just use the existing plate in the end rib, you will still have to remove the tank to gain access and a small bead of proseal to reinstall in my eyes is a lot easier to do than creating a whole new inspection plate.

To caviat on the flop tube question, are builders adding anti rotation brackets to the AN fitting on the flop tube? Or do you rely only on how tight the AN nut is?

-david
 
I have been thinking about getting an expert sheet metal guy to fabricate an inspection plate with a contour so I can place it on the top of the tank over the flop tube bay. I'd only use a gasket to seal it. That might be the rub right there, though. The idea would be to not have to deal with proseal in the future.

With that being said, I'd also like to know how difficult it truly is to inspect/replace the flop tubes if I go the conventional route.
 
You may not know if your flop tube fails in flight until the fuel level gets below the point of failure or outlet and the engine quits.
The advantage of having two tanks is that if you do have a flop tube failure you have another tank to switch to, providing you have fuel in that tank.
Now you can just hope you have good emergency procedures, can assess the problem, and take action on it.
PS - I have never heard of one failing, but I suppose it could and has happened.
 
Tank removal

Why is that needed? I put a plate on the end rib like the standard tank and have the standard fuel level sender on the back. If I ever need to service the tank I'll remove it from the wing and work on the bench. Seems better than installing a service panel on your nice clean wing.
 
I'd really like to NOT make an inspection/access plate in the top of my wing. I'm just wondering if it would be easier than removing the wing and breaking the proseal on the inboard rib, then resealing it and doing it all the hard way. That seems like a monumental effort, but maybe it isn't so bad.

Does anyone have pictures of the process of tearing into the T-807 or T-411 cover plate for an inspection? How about a story?
 
IronDawg said:
I'd really like to NOT make an inspection/access plate in the top of my wing. I'm just wondering if it would be easier than removing the wing and breaking the proseal on the inboard rib, then resealing it and doing it all the hard way. That seems like a monumental effort, but maybe it isn't so bad.

Does anyone have pictures of the process of tearing into the T-807 or T-411 cover plate for an inspection? How about a story?
Click to expand...

It is more work adding something that is not in the plans and is not necessary. The design is good.

It is easy to remove the cover plate that Van has on the plans. The only change I made was to use Allen Screws.

Have not seen a gasket that did not leak on a fuel tank. ProSeal is all I use.

I have taken two sets of tanks apart and reused everything. It is easy to remove a ProSeal cover and reinstall it once you know how to do it. It is hard to write up. I have done it and it is harder to write how I did it than to just do it.

Use a thin sharp putty knife to break the ProSeal bond. Use a hammer to get the putty knife as parallel as possible to the two metal surfaces and use that technique to CUT around the access plate. DO NOT PRY the cover off.

The above short description is how I have done it on two different airplanes.
 
IronDawg said:
I'm just wondering if it would be easier than removing the wing and breaking the proseal on the inboard rib, then resealing it and doing it all the hard way.
Click to expand...

I removed the rib while converting a std to a flop. NOT fun but that is not something you will need to do. Build the tank's outside rib like a standard tank, instead of placing the fuel fitting on the ~6" round plate, mount it up front for the flop tube. Removal of the round plate will give you enough access to inspect/replace the flop tube down the road without removing the rib.
 
Inspection holes

A friends T18 Thorp has 4 access holes in each wing , located on the bottom, one hole between each fuel rib. These are the only access areas for the tank.
 
RV6_flyer said:
It is more work adding something that is not in the plans and is not necessary. The design is good.

It is easy to remove the cover plate that Van has on the plans. The only change I made was to use Allen Screws.

Have not seen a gasket that did not leak on a fuel tank. ProSeal is all I use.

I have taken two sets of tanks apart and reused everything. It is easy to remove a ProSeal cover and reinstall it once you know how to do it. It is hard to write up. I have done it and it is harder to write how I did it than to just do it.

Use a thin sharp putty knife to break the ProSeal bond. Use a hammer to get the putty knife as parallel as possible to the two metal surfaces and use that technique to CUT around the access plate. DO NOT PRY the cover off.

The above short description is how I have done it on two different airplanes.
Click to expand...

I totally agree with Gary. I would add careful application of heat with a heat gun makes the proseal soften and more pliable easing the job. I did mine twice too, once without removing them from the airplane. I made a "chisel" with a piece of 1/2" x .063 x 9" steel strap filed on one side. Round and scothbright the corners slightly so you don't gouge the rib. If you are doing it while the tanks are still on the airframe, the long thin knife will bend allowing you to clear the lower flange and skin while keeping it flat on the surface of the rib and still get a hammer on the end of it. I didn't have a putty knife that I could get up in those tight quarters.
 
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