Beach Shoot #16 - Meal Helicopters
Date: 2003-12-16
Description
Three helicopter devices, each of a different ID to test various design parameters. Each was charged with straight meal propellant, hot-melt and wadding end plugs, and meal-NC primed blackmatch fuses covered with a little masking tape to allow reliable ignition on wet ground. All had a 45 degree down thrust vector, 1.8 mm nozzle holes for the 5 mm and 8 mm ID devices, 2.5 mm for the 12.5 mm ID device.
The 5 mm and 8 mm ID devices were each 50 mm long, an 8 mm ID tube of the prefered length (80 mm) was not available. The 12.5 mm ID device had a 125 mm long tube, keeping the 10 x ID length ratio of the 5 mm ID device.
The 5 mm ID device had its stabilizer bar hot-melt glued to the end of the tube after assembly. The other two had it drilled through the tube before the additional hot-melt was used to hold it in place.
Comments
All worked!
The 5 mm device flew up about 10-20 metres, caught somewhat by the wind and carried about 10 metres horizontally. It fell into the pool, sank and was not recovered.
The 8 mm device flew quite swiftly about 20-30 metres up in a fairly short burn. Its lower mass (shorter) relative to its ID may be a better design figure for future devices. If it burnt much longer it would reach heights and travel distances that would make the current shoot site too small for safety. It flew about 20 metres horizontally falling onto the sand but was not recovered.
The 12.5 mm device was a poor performer. It took off with great acceleration, but started to slow shortly after. It peaked about 30 metres up and came back down about 30 metres out onto the beach. It burnt for several seconds after landing. On recovery the nozzle hole was found to be greatly enlarged. No doubt this caused the poor performance, a conical clay end plug will be used in future.
The 5 mm device gave a gentle fairly long duration performance. The 8 mm device was probably the best all-round device. The 12.5 mm device if it was correctly built would likely fly to scary heights for this location, not that my rockets don't fly higher, but the helicopter devices are less predicitable and more effected by wind.
Attachments
| title | type | size |
|---|---|---|
| Test Video (5 mm ID) | video/x-msvideo | 738.308 kbytes |
| Test Video (8 mm ID) | video/x-msvideo | 1.173 Mbytes |
| Test Video (12.5 mm ID) | video/x-msvideo | 2.237 Mbytes |
| Pre-Test Picture (all three) | image/jpeg | 28.147 kbytes |
| Post-Mortem Picture (12.5 mm ID #1) | image/jpeg | 95.220 kbytes |
| Post-Mortem Picture (12.5 mm ID #2) | image/jpeg | 51.335 kbytes |