Last weekend I went down to the excellent Midland Sky rocketry event hosted by the Midland Rocketry Club, it was a fantastic weekend with great weather and lots of flights. I was very pleased to successfully fly the ODR rocket again with the dual deployment working perfectly! The fab Alex Ward lent me an onboard camera and I had a padcam set up so there's a couple of nice videos below.
The other excellent thing was that my friend Charles Simpson wanted to fly my annular parachute on one of his rockets, his "zombie" rocket (as it had been resurrected a few times!) was about 1.6kg and the annular chute gave it a really steady descent rate on a single deploy flight. I would estimate it in the region of 6m per second. I know I am biased but it looked gorgeous in flight! I need to make more!
So I have been working on and off on this 1.5 meter diameter parachute for a while now. It's been a great project and I have learnt loads especially about sewing machines! It's designed to be the correct size for my Level 2 certification rocket I am currently constructing. The parachute is designed with 16 "gores" or panels which are hot cut using a soldering iron.
I made a plywood pattern to cut around and the hot cutting method works well as the edges are all sealed and don't fray. I added enough material to allow for a flat felled seam but cut the inner and outer edges to be the designed size with no seam. I think that this is strong enough but I am interested to make another and experiment with adding binding to the edges as I have seen this done on some ex military parachutes I own.
After cutting all the panels it took a few sessions at the sewing machine to connect all the gores together, then came the task of connecting all the top lines which are the shorter lines on the inner diameter that connect into (hand sewn into) the main lines, with 16 of each that was plenty of work!
Above showing the stage with all the inner diameter lines sewn in on the machine. I just used 2mm braided nylon for this build as I had some and its quite cheap which is important when you use about 45 meters in this construction. Now that I have worked out some design issues etc I will probably make another at some point and use a higher quality material for the lines.
Above is the first test inflation on a luckily breezy day. The geometry/shape of the annular design when inflated actually results in a much higher drag coefficient than other parachute designs which seems counter-intuitive particularly when you consider the huge hole that they have in them! Finally, massive thanks to my parachute making mentor BJ Gray of Bama Recovery Systems, who I heartily recommend if you want to purchase a very high quality parachute made by a true master of the art.
So I have been working on the rocket with which I may potentially attempt my Level 2 High Power Rocketry certification flight. The nosecone for the air frame is quite large and I wanted to be able to use some of the area within it for a payload. In particular I am considering flying a DIY GPS tracker in it. I also wanted to firmly affix the bulkhead to the nosecone, probably by bolting it into the 3d print but also epoxying it in place so the bulkhead will be in place permanently. So I've designed and built this payload area that can be threaded in and removed. It consists of a 31mm OD tube with a threaded 3d printed adaptor glued to its base. Another 3d printed threaded section is glued to the bulkhead which receives the tube and allows it to be fixed in place.
Above the tube is glued to the 3d printed base which has an internal threaded section.
Inserting the payload tube.
Payload tube in situ and tightening the threads.
Above is the tube threaded through the bulkhead removed from the nosecone. I've 3d printed a press fit cover for the upper end of the tube, to make sure the cap is retained throughout the violence of a rocket flight I'm going to experiment fitting a flush mounted M2 machine screw to fix the lid in place.
As part of this process I of course had to cut the card tube to the length I required so I made a quick episode for the Rocketry Series on my YouTube Channel about approaches to cutting cardboard model rocketry tubes. Enjoy and don't forget to hit like and subscribe!
A while back I came across this "Peak of Flight" issue all about odd chutes or odd parachute designs (Direct PDF download here). In it featured a tutorial for making an interesting looking Hexagonal Annular parachute, Ages ago I made a quick prototype using string and tape and the canopy cut from a plastic bag and it made me interested enough in the design to sew a small one from rip-stop nylon.
I wanted to test the parachute but didn't want to move straight to chucking it into a rocket so I decided to build a drop test mechanism I could attach to my drone. Rather than reinvent the wheel the servo holding pin pushing part of the mechanism (see video) was 3D printed from some files found on thingiverse here.
In the (badly edited!!) video above I walk through the main components of the drop mechanism and then show some clips recorded from today's test flights and test drops. Massive thanks to my son H (9yrs) for his excellent help in operating the release mechanism.
