Tanks in progress

[N941WR]

Originally Posted by YellowJacket RV9

I wouldn't worry too much about the MEK. I did at first, and then started looking into it. There are many other builders that use MEK to actually thin the pro-seal for some applications, and plenty others that have used it to clean the outside of tanks with no ill-effects. I am not saying that the problems somebody else experienced are not real, but would not worry too much about the MEK causing leaks IF you make sure to fully cover every rivet shop head and form nice complete filets around every seam. I cleaned my tank skins with MEK and they tested leak free right off the bat. Maybe fuel vapors will be different, but they'd have to go through a LOT of MEK to get out. Proseal is (relatively) cheap, I used plenty.
...
Chris

To be clear, I did not thin the proseal and I did cover the rivets, and the entire rib flange as well as put a bead down each rivet line. My tanks tested great, no leaks and worked without any leaks for two years. It was just before I painted the wings that I cleaned the top of the left tank.

Sure enough, that is where I had a bunch of rivet leaks, no place else. unfortunately, the leaks appeared a year after the airplane was painted.

So, for future builders, DO NOT use MEK to clean up excess proseal with MEK. You can wipe it off with a rag while it is still setting up or let it harden and then sand it off later. Simple and easy.

Chris, I see you are still building. If that is the case, I take it you haven't filled your tanks with fuel yet? Seeing that balloon still inflated after one day really isn't much of a test. However, is seems that is all we have short of installing a pressure gauge and seeing if it changes over the course of a week or two.

[YellowJacket RV9]

I could certainly have issues once I fill the tank, no doubt about it. My only point was that many others, including many currently flying have cleaned with mek with zero ill effects. Also, it seems in your case the MEK was used years after initial construction, whereas we are talking about using it to clean fresh proseal that has probably not thoroughly cured. Perhaps the effects on aged proseal are different.

Certainly MEK could have caused your problems, and using it sparingly or not at all may be excellent advice. My aim was to reassure the poster that he is not automatically doomed to leaky tanks. Searching the forum brought up plenty on this subject, so I'll leave it at that. In any event, your experience is certainly worth sharing no matter what.

Chris

[N941WR]

Originally Posted by YellowJacket RV9

I could certainly have issues once I fill the tank, no doubt about it. My only point was that many others, including many currently flying have cleaned with mek with zero ill effects. Also, it seems in your case the MEK was used years after initial construction, whereas we are talking about using it to clean fresh proseal that has probably not thoroughly cured. Perhaps the effects on aged proseal are different.

Certainly MEK could have caused your problems, and using it sparingly or not at all may be excellent advice. My aim was to reassure the poster that he is not automatically doomed to leaky tanks. Searching the forum brought up plenty on this subject, so I'll leave it at that. In any event, your experience is certainly worth sharing no matter what.

Chris

And my point is that a good number of people have had problems with paint blisters and leaks on tanks that held air, as yours and mine did. After my paint blisters appeared, I did some research and found that you simply should not clean up excess proseal with MEK.

Why some builders got away with it and others didn't, I have no idea. I'm simply saying, for the sake of future builders, do not use MEK to clean up your tanks, it is simply not worth the risk. There are other ways to clean up the excess proseal without touching it with MEK.

Simple as that.

[blueflyer]

Originally Posted by JimWoo50

When you install the rear baffle to the skins the tendency for me anyway was for the sealant to be squeezed out of the skin/baffle seam. Good Luck.

......I can't tell from your pics if you opened up the lightening whole on the fuel filler rib to full diameter but if you do this and the next inboard one it will make fueling the plane easier.

Good tip about the rear baffle. I will keep that in mind. I must admit I was unaware folks enlarged these lightening holes, and I did not do that on mine. Sounds like a good idea though.

[DanH]

Originally Posted by N941WR

...do not use MEK to clean up your tanks, it is simply not worth the risk. There are other ways to clean up the excess proseal without touching it with MEK.

Bill, did you have wet leaks, dry blisters, or both?

Regarding MEK, recall that a sample group of blistered builders volunteered to anonymously answer a long list of survey questions, with the goal of locating common factors. MEK cleanup was not a common factor in this group.

I've had sealant samples submerged in a 50/50 mix of MEK and lacquer thinner for several years now. The samples were carefully mixed (by weight) using improper ratios as well the correct proportions. At last check there was no gross significant effect. With this reminder I'll pull the lids for another look. I suspect long term reduction in elasticity or tear strength, but for sure they're not melting like the Wicked Witch.

[Maxrate]

I hope not! I cleaned the H*** out of everything with MEK and used the Fay sealing method, being careful to fully encapsulate each shop head and make thick fillets as Rick suggests. I would even wet my finger to slightly move the tank sealant at times. I let the tanks set for several days before testing making sure it was hard like rubber. Using a natural gas gauge I pressure tested my tanks inside the house at 75deg (climate controlled) for several days at different pressure levels, 1.2 to 1.8 psi. The gauge never budged. I have yet to introduce fuel. I think there would be an admonishment somewhere about contamination in product material. I simply have found none. I also queried several APs and they all used MEK in small quantities while working with tank sealant on small jobs.
The great thing about the VAF is all the opinions offered and experiences had. Thanks to the heavy hitters for weighing in!

[N941WR]

Originally Posted by DanH

Bill, did you have wet leaks, dry blisters, or both?

Dry blisters on the top of the left tank only. Again, this was the only place that I cleaned off proseal with MEK and I did that two years after I started flying, just before the plane was painted.

Never a blue streak or any other indication of a leak of any kind.

The odd thing was that it wasn't just one or two rivets but something like 14.

That tank looks horrible right now because the paint is sanded off. I'm thinking of painting each rivet head with a rattle can just to see if it still leaks before putting a finish coat on it. Any suggestions?

[byoung]

Andrew, how did you form the end of the nails to get your various "spoons"?

[Aerosporty]

Great time to put the tank in the cradles, and fill with water. I found leaks this way, and was able to address them before the baffle installation.

[blueflyer]

Finally, finished the tanks (no baffle yet obviously). Man, this was slow and tedious work for me. I am glad to be done with all the ribs. I hope there are no leaks. Did I say this was slooow work. Man, maybe I took more time with it or something, but I will be glad when these tanks fully complete and tested!