Saturday, 7 September 2019

Inflating the DIY 1.5 meter annular parachute.

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. 

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