It has taken 3 months to fix, however what seemed impossible has been achieved.
I did not build my Rebel so I was at somewhat of a disadvantage.
The Rebel in question is a Canadian Advanced Ultralight and the leaky
wet wing only occupies 2 bays in the wing.
I tried sloshing initially and when that failed I made the decision to cut
access holes in the bottom of the tank.
Since I'm not a builder, I had a sheet metal man from the conventional
aircraft world cut 4 access holes in the bottom of the tank. I promised him
some dual time in the Rebel in exchange for his labour.
The access holes are the ones shown on the website of Scott Hibbs
http://home.pacifier.com/~hibbs
Once the holes were cut it was up to me to clean out the tank, what an
unenviable task, the builder had used 2 different kinds of sealant on the seams,
plus a sloshing compound of some sort and then there was the Sealpak slosh-
ing compound that I had used, what a mess.
I soon learned what MEK, a respirator, face shield, chemical
proof gloves, razor knife, scrapers and a dremel tool with a flexible drive shaft
and brass wire wheel brushes were for. A powerful light was also a must,
I used an auto handheld spot light and my aircraft battery to power it.
Of course when you clean the bottom portion of the tank a mirror is required
to see, my wife had to give up 2 of her cosmetic mirrors to the cause. I felt like
a dental student learning how to put my brain in reverse.
My hands are still healing from all of the cuts I sustained during the cleaning
process.
When the tank was as clean as I could get it after going through 2-1/2 gals.
of MEK at $20/gal., it came time to PRC and rivet the doubler rings in place using
RR6403 tank rivets and test for leaks before applying PRC to the seams. My thinking
here was to identify leaky areas of the tank before applying PRC to the seams and
gussets.
I must have bought 3 pints of PRC at $97Cdn per pint along with a couple of
Sem Kits at $40 Cdn per kit. Ridiculous!
I was ignorant and inexperienced, I should have expermented with mixing small
quantities using the 10:1 ratio by weight that is suggested. Also it wasn't until near the
end of the project that someone wrote that you could quick freeze PRC that has been
mixed for future use as long as you don't put it in a frost-free freezer.
In order to determine where the leaks were I was advised to use a vacuum cleaner
to suck air out of the tank with soapy water on the seams and look for bubbles. I made
4 access covers out of lexan and I cut a hole in one of them slightly larger than my
vacuum cleaner nozzle. No need to fasten them in place because the decreased pressure
in the tank sucks them down against the doubler rings, it doesn't matter if they leak a little,
a small pressure decrease in the tank is quite sufficient.
Use soapy water on the seams, put the lexan covers in place, shine the spotlight on the
soaped up seam, apply vacuum and look for bubbles.
This system of leak detection worked like a charm, but there is a technique when testing
the bottom seams using a mirror which limits your viewing area to the width of the mirror.
Only soap small portions of a seam at a time, no more than a mirror width, here's why:
If you soap a seam in its entirety and there is a leak along that seam out of your view,
you may void that leak of soapy water real quick and by the time you slide your mirror along
to view this spot, you may not see any bubbles. This happened to me and caused me no
end of grief and lost time.
When I finally repaired the last leak, I tested the tank before re-installing it on the plane,
first with water and then with fuel.
I hope the expense and the effort is going to be worth it, so far so good, the wing has been
back on the plane for 8 or so hours of flying and no leaks. I'll keep my fingers crossed!