A.K.A. 'Mr. HoJo'
- Dec 4, 2016
- Reaction score
- Birmingham, AL
Saturday at the club launch, had my first opportunity to fly some of the Q-Jet motors from Aerotech. Decided to test fly them in a Boyce Aerospace 3-D printed Honest John. I had previously flown this rocket without any issues using Estes C6-7 black powder motors.
First flight (pictured above) was on a Q-Jet C-12-8 motor which according to packaging is equivalent to the C6-7.
The motor is a bit slim to fit the body tube on the 3-D printed rocket, which lacks a motor mount or hook. A couple of rounds of masking tape resulted in a firm, tight fit. Note: I did not peel off the label for this motor.
This motor proved to be a nearly perfect match for the heavy 3-D printed rocket. It leapt off the pad for a beautiful straight flight up to around 850-900 feet. Ejection came right at apogee.
But we experienced a problem. The shock cord attachment for this rocket is unique. The nose cone is attached with a kevlar shock cord (not supplied with kit) by gluing in between the fin can section, and the body tube section during construction. After glue drives, you trim the excess with a knife.
This rocket had flown three times without issue, but on this flight, the shock cord pulled loose, allowing the booster to free fall to the ground, while the nose cone returned under chute. No damage to either.
Decided to attempt a field repair, and fly again later in the day. Using a small hand drill, I drilled a small 3/32" hole near the top of the booster section. I threaded a 3.5' length of kevlar thread through this hole, and knotted it. A bit of CA glue secured the knot, and made sure that the shock cord would remain attached to the booster section.
2nd flight on the Q-Jet C-12-8 was also arrow straight. But at ejection, a major malfunction. The rocket spilt into three pieces. Post flight examination revealed that drilling the hole into the airframe was a huge error on my part.
Because 3-D components are printed a layer at a time, stacked on type of each other--the shock of ejection resulted in a "horizontal zipper" sawing the airframe cleanly at the point where I drilled the hole.
Lesson learned for sure.
Overall, very impressed with the Q-Jet C12-8. The only other Q-jet I flew was a B4-4 (equivalent to an Estes B6-4 according to package.) Fly a Der Red Max, which had performed very well on B6-4's in the past.
It lifted off the bad, and struggled to reach about 400 feet. It was clear this wasn't enough motor for the rocket. It peaked, and nose dived towards the ground. It fell and fell with no ejection. A full second after it lawn darted into the moist Alabama clay, the ejection charge fired at last. The rocket was a near total loss.
All present agreed that the delay seemed much longer than four seconds, but no video or other documentation to verify.
I'll be cautious in the future, and fly some RTF models to do initial testing. YMMV.
Gotta order another HoJo from Boyce Aerospace. Love that rocket!