Batch 2019.01.08

4 Terry-length Everyclear grains for 54mm cases, with 0.625 inch cores, cast as two 6-inch-long double grains with 0.5" delrin coring rods, then cut, cored, and trimmed.

The 54mm casting tube I'm using weighs 1.84g per inch.

This was my second time mixing APCP propellant. Again used the 4.5qt mixer and hand packed with no vacuum processing. Same formula as yesterday

These grains were cast on 2019-01-08.

Results

The updated batch size was just right, there was a bit of excess propellant so we can make density and burn rate measurements after cure. The excess weighed in at 17.9g after cure.

• Grain 1, 2.980" long, 162.6g gross, 5.48g casting tube, 157.12g net
• Grain 2, 2.970" long, 162.0g gross, 5.46g casting tube, 156.54g net
• Grain 3, 3.010" long, 164.7g gross, 5.54g casting tube, 159.16g net
• Grain 4, 2.995" long, 163.6g gross, 5.51g casting tube, 158.09g net

The mass per unit length was within 0.1g/inch, which seems awesome.

In total for this batch and the previous day's, which were post-processed together at the same time, there was 10.4g sanded off the grain ends and 64.7g of waste from core drilling the 0.5"-ish holes to 0.625". Really leaves me wondering if it wouldn't be better to just start with the right size coring rod for future batches and avoid the coring waste. Might leave me wanting to rough the cores for better ignition? But, maybe not. Something to ponder more.