Success!!! Well, almost
After a long break I pulled out my envelope supplies and gave it another crack.
This time I used two side tape. I know this isn't preferred. I tried a number of brands and found one that was really thin and (as far as I could tell) 'tear' strength. The tape comes a little wider than I need, so I cut it in half to make it go further.
Using two side tape is so much easier than glue. I cut the gores one seam width wider and simply lapped the gores one on to the next with the tape. The goring tool with let me stick down the first gore, then run a strip of tape along the seam. Then the lapping gore I would get stuck down by slowly rolling back the wrapper on the two side tape a little bit at a time. With the tape you still only get one shot to put it down right, but I don't have to risk accidentally sticking down gores when I'm not ready and since the tape has a little give, it's easier to get the joint pressed down flat. The envelope went together surprisingly quick (no waiting for glue to dry)! Since the tape is completely covered each side, there's no hidden sticky parts grabbing at the insides.
I used the fill valve off a helium balloon. Just cut it from the balloon and slipped it into the seam near the tail. More two way tape to attach and seal it. The nose came together perfectly. Used a small button sized disc inside and out. The tail was a little rougher but not bad. More tape and foil pieces to close it in.
27.9g (air filled) weight. There were a few 'not so smooth' seams, but for the most part she looked the part of a blimp. The envelope filled to pressure with a satisfying ping (unlike my first attempt).
So I blew her up a little more and set it aside to sit overnight and see what kind of air loss problems I might be facing. That's when things went bad. The seams started pulling loose until I had air escaping. I'm not sure I understand. When I tested the tape I had to rip the foil to get it free. But in what seems like no time at all, all my seams had spread significant amounts. I think I might have sabotaged my own efforts. The gores were marked with sharpy and cut out. After assembly I use rubbing alcohol to wipe down the seams and remove any remaining sharpy lines. Alcohol is completely useless for cleaning the two side tape off scissors, so I assumed it was tape safe. Now I'm wondering if it softened the tape up just enough to let loose.
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