Landing Gear SB Question...

Piper J3 · #1 12-17-2015, 01:58 PM

I need to do both the Fuel Tank and Landing Gear SB?s on the RV-12 I recently bought. I want to do the fuel tank first and I?m considering buying a new completed tank directly from Van?s.

I have a question? If I install the new tank now, can the tank remain in position during the landing gear upgrade or does the tank need to be removed for that SB? I think I read in VAF that the tank can remain in position but you need to be careful when drilling out rivets for the new skin doubler so that the drill doesn?t protrude and damage the tank. I can use a drill stop and even slid a piece of steel sheet metal between the side skin and the tank for precaution. Can someone confirm that this is doable?

JBPILOT · #2 12-17-2015, 02:05 PM

Have the tank out for landing gear mod. If you have not worked with tank sealant, it may be hard to convince you it is not that hard to do. If you can find a builder near you for help, I'd suggest doing tank yourself. Messy, but you will have a better understanding of the tank. My opinion again, but just take the top off. Much easier to do the 2 mods to the tank, and close the window if it is there. Good time to do vent kit, and mechanical gauge.

DonFromTX · #3 12-17-2015, 03:14 PM

I think we all dreaded the tank, then when we did it we felt silly for the worry. Just do it, it is one of the simpler jobs of building the plane!

Tony_T · #4 12-17-2015, 03:40 PM

To answer your original question, yes you can use the methods you describe to safely remove the rivets without removing the tank. We have done it that way here twice on 2 different RV-12s. The only down-side is that it is difficult to clean out the removed rivets from behind the tank.

That said, since you also have the tank mods to do, I would take out the tank and do those mods or plan to install your new Van's built tank at that time. Since you have the LG SB to do, then you will have the tools necessary to do the tank SB's. To do this part, for instance, you need the countersink tool and the right bits for the different flat head rivets:

The tank SB is fairly difficult for an in-experienced non-builder owner in my opinion. So is the MLG mod.

You may be better off with a new tank but realize that for that much money you can buy some tools and get experience about the tank, as J. B. has said. And like he says, get help and take the top off and work from the top as opposed to trying to work through the front cover. Getting the top off is not a big deal:

Also, if you are going to work on the tank, do install the little anti-rotate device on the bottom fuel return fitting:

A new factory built tank will no doubt have this already installed.

Regarding the vent install, if I were doing it again, I would skip that. It doesn't help all that much and creates it's own minor issues. Like dripping gas on the hangar floor if you fill the tank and are using a non-vent cap.

Regarding the window, there was a window SB a long time ago that addressed problems with the original window. If that has been done, and your window does not leak, then keeping the window is an option.

Some will argue that the window will leak eventually. There are loads of opinions about the window on this forum.

MartySantic · #5 12-17-2015, 04:08 PM

Echo most of the responses. Follow the service bulletin and remove the tank prior to implementing the landing gear repairs. You will be doing a lot of drilling in the tank area.

Working on the tank is not that hard. After you have tank tank removed, REMOVE the top of the tank and implement the tank service bulletin and all of the improvements. Here is my short list....

Remove the window if still present.
Add the Moeller gauge.
Add the fitting for the fuel vent (even if you do not install the vent line).
Add the anti-rotation device to the bottom of the tank.

Working on the tank top is quite simple. Use a thin putty knife and drive it with a hammer around the perimeter to break the seal, per Tony's photos. Scrape the old sealant with the putty knife. I then used a wire brush in an electric drill to brush and clean the mating surfaces. Implement the changes, vacuum and wipe down the inside of the tank. Re-rivet the top of the tank using the correct rivets. Let it cure. As a final step, I added about a gallon of gas to the tank, sloshed it around, drained the gas thru coffee filters and repeated till the coffee filters were clean.

Piper J3 · #6 12-17-2015, 04:17 PM

Thank you all for very detailed answers. I really appreciate everyone sharing their time and knowledge.

I have another question... If I buy a new tank from Van's, and I don't want to install the vent, can I continue using the vented cap and then plug the vent fitting? I think this is my preferred option at present.

Seeing as it's winter in northern Ohio perhaps I will buy and install tank now and wait until warmer weather to do the gear SB. Gear SB doesn't bother me - I have previous aircraft sheetmetal experience and also a friend who is A&P.

Then the real question is - does installing the tank, removing the tank at a later date, and re-installing again after gear SB propose a risk for developing leaks or other unforeseen problems?

MartySantic · #7 12-17-2015, 04:24 PM

Quote:

Originally Posted by Piper J3

Then the real question is - does installing the tank, removing the tank at a later date, and re-installing again after gear SB propose a risk for developing leaks or other unforeseen problems?

Not really, Only risk is twisting the fittings on the bottom of the tank and breaking the sealant between the fitting and the tank bottom. Use a backup wrench and you will be fine.

D&M Dan · #8 12-17-2015, 04:51 PM

Anybody have the part number for the anti rotation device? I am doing all the revisions now sooooo, might as well do that also.

Mich48041 · #9 12-17-2015, 05:23 PM

Save yourself $800 or whatever a new tank costs and repair the original tank. While the top of the tank is off, install the vent fitting whether you intend to use it or not. At least you will have the option at a later date. Follow John Bender's example using 1/2 inch tube.

MartySantic · #10 12-17-2015, 05:45 PM

Quote:

Originally Posted by Mich48041

Save yourself $800 or whatever a new tank costs and repair the original tank. While the top of the tank is off, install the vent fitting whether you intend to use it or not. At least you will have the option at a later date.

AGREE! Save the $$$$. Tank work sounds intimidating but is NOT! If you have not worked with tank sealant, find ANY RV builder to help!! They ARE, no matter the rumors, are quite friendly.