Yeah, it's an old one. And I see lots of hits for it in Google. But I just tried it and it didn't work.
What's the scoop?
OK, I've also complicated things a couple ways.
First, I'm trying to patch in a new valve. I cut out the old, leaving a 1" hole. I have a new one to patch in with 1" all around, giving at least a 1/2" overlap everywhere.
(Why am I doing this? For a third crazy reason. I have an irreplaceable Tufo cross sewup. I rolled it and tore off the valve. They're known to be tubeless. I open it up and it has a nice, regular tube. Stuck to the casing, but it readily peeled up. I have the section exposed and want to at least try splicing in a new valve. THEN I'll try sewing this tire shut. I'll lay in a section of thin fabric first. Yeah, funny, I know.)
Anyway, I glued it all up then glued it. It all laid in smoothly. After a day, it peeled up easily. I didn't sand the tubes. Also I neglected the talc angle. The tubes seem dry and clean and not talc'y, but who knows. So I used thinner and alcohol to clean off the old glue and sanded both surfaces good. Everything looked clean and spotless and dry.
I reglued. And let both surfaces dry for an hour. I reinstalled the patch. I clamped it for a day. Then I let it cure further for another day.
Today I tried to put a little air in to test. It held a bit but when the tube got a bit more of a bulge to it, it blew a half-inch gap.
I've now reglued and reclamped to see if I can get that section to hold.
I used Park patchkit glue the first time. I'm now using car-tire vulcanizing cement from auto parts store. (I use enough of this stuff that I finally bought some in bulk.)
Any hope for using a tube to patch a tube?
Is there an issue here of hole size? (Jobst talks about patches failing from the lip of the hole outward.)