Originally Posted by Carl@Semroc

Using CA to glue the flap did fix the burn-through problem at the nozzle. However, further tests had blistering at the delay section at 5-7 seconds and burn through at 10+ seconds. We would never have a delay that long, but it does show a potential problem with external case heating.

In cutting open many of the casings, I noticed that the layers are not glued as well as the 18mm casings made at the same time. I suspect NEPT has problems with tubes that small.

We have refiitted to 18mm and will put the 10mm on hold until we have more resources (time, money) to continue trying to make them work.

Thanks to all for the suggestions!