I started my fuel tank sealing last weekend, beginning with the skin stiffeners. I decided to go with the method laid out by Rick Galati in the "sticky" thread. so far the sealing at least has gone well, but I have a question and a caution.
First, the caution, which is not really directly related to the fay sealing method, but more to methods of masking. I chose to mask areas around the stiffeners so that I could avoid getting a mess of sealant on the skin. Turns out I needn't have worried much, and caused myself more problems overall by doing the masking.
My main bad decision was using "scotch tape" (actually Staples brand "invisible tape", P/N 34-8711-4390-3) to mask. Most of the experiences I've had with this kind of tape made me think it really didn't stick much.
What I failed to consider was that when you prepare an aluminum surface to maximize adhesion, the tape will stick far better than you ever imagined that this kind of tape can stick. It becomes a film that is only fully removable with lots of physical effort and solvent.
Which brings me to the question: how tenacious should this sealant be? I am using the Flamemaster CS-3204 B-2 provided by Van's. Tech sheet here: http://flamemaster.com/wp-content/up...rev-09-131.pdf
The tech sheet says "For surface preparation as well as removing fresh or cured CS 3204, Methylene Chloride can be used. Cured CS 3204 will
require a soaking period in Methylene Chloride bases stripper for satisfactory removal. "
I have been using MEK, acetone, and ethanol to remove the "scotch" tape residue. MEK seems to work the best, followed by acetone, with ethanol being a very distant third, almost useless in getting the tape off, but it does a decent job on the underlying tape adhesive. Note that I have been doing a very good job of keeping the solvents away from the sealant!
I was nervous about getting MEK and acetone too close to the sealant itself, because of other things I have read that say MEK can be used to remove the sealant.
However, everything I have read indicates that the sealant should be extremely difficult to remove. I understand that until the sealant reaches full cure, it will be easier to remove, but even without solvent, I find I can remove it from the aluminum surfaces pretty easily just by getting my fingernail around the edge and then pulling on it.
Should I be able to do this at all? I set this sealant on Sunday afternoon, struck rivets on Monday evening, and now on Wednesday, I can still peel back the sealant fairly easily.
The aluminum was prepped by acid etching and alodining several weeks ago, and then cleaning with MEK, drying, scuffing with maroon Scotch Brite, and then cleaning again with MEK, and drying prior to sealant application. I can't think of anything more I could have done to prep the surface better.
The sealant has an expiration date of 09/18, but I have kept it in the freezer since I received it in April. I warm it up to room temp (mid 70s fahrenheit) thoroughly before mixing and using. The mix is definitely correct (used 5g B : 50g A)
The sealant seems to have a solid hold until I mess around with it with my fingers. Is this normal?