We started refitting "Mabellette" to produce 10mm engines just before we left for NARAM. Over the last few weeks we have been able to finish the tooling and make adjustments to the machine and program. Mabellette works great and the engines look very good. There is just one small problem...

At between 3 and 5 seconds into the delay, the casing burns through on many of the engines. We had never noticed before that the first 1/8" of the inner (beginning) wrap does not have any glue. The failure always occurs at the unglued seam just above the nozzle. It does not matter if the delay is a fast burning (10sec/inch) or slow burning (30sec/inch) type. It is still around 5-7 seconds of total time since ignition. Replacing the delay with BP gives a 2+ second burn with no case weakness.

This is disheartning. We were trying to get about a thousand ready to give to the FAI team at the Capital Cup next month to use as practice engines over the next year. I am sorry for the SAM members that were anticipating the 10mm engines.

Perhaps this is a manufactuing flaw or it may be a problem just associated with very small tubes. They were made by New England Paper Tube, the original engine tube company for Estes and others. The 18mm casings made at the same time do not have the problem. I will be following up with NE this week.

Bruce said the upside is that we have B14's quicker and 18mm engines work in most of our current kits. I still hope we can make the 10mm work.

__________________
Carl McLawhorn
NAR#4717 L2
semroc.com