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• Additional Bridle Modifications

  J. M. Hopkins • 06/27/2016 at 00:04 • 0 comments

  I was able to travel to the beach again today to test out my next iteration of bridle adjustments. Regrettably the wind wasn't what I was hoping for, but I was able to test out my modifications to some extent, but another day of full wind is needed.

  Some background on my brake line implementation is needed to understand the modifications of the bridle:

  There are three main cells to the design, a central cylindrical cell and two conical cells separated by vertical rbbing. Forward thrust is created by the geometry of the trailing edge, allowing air to be scooped, and vented to the rear. The brake lines deform this rear edge of the canopy, changing the amount of thrust being vectored.

  The first version of my bridling allowed for the brake lines to deform the two conical cells rear edge, but not the central cell. This made for a very twitchy and fast response to controls which was not the most stable nor easiest to control.

  The new revision has changed the brake line attachments to include deformation of the central cell as well as the sides, with a staggered length between the lines, meaning that when the brake lines are pulled that the central cell is deformed first which creates a slight change in thrust, followed by the deformation of the conical cell which then leads to rapid changes in direction. The result is a much more stable design that is easier to control.

  In order to combat nose collapse in the face of oncoming wind from air column penetration, a slight amount of brake line needs tension and a fairly high wing loading is required (approximately 1lb/sqft).

  Again, I hope to have additional photos/video here during the next test.

• Bridle Testing

  J. M. Hopkins • 06/20/2016 at 02:23 • 0 comments

  So one of the nice things that moving to California brings me is a consistent access to the beach and the winds that come along from the Pacific ocean. This allows me to finish my testing on the single skin steerable parachute, in this case bridle testing.

  The bridle allows the canopy inflation geometry to be modified to conform the parachute to optimal characteristics for stable flight. This series of testing, is to establish the correct line length for each support line to optimize the canopy in numerous ways.

  Inflation geometry must maintain shape in order to be effective, in this regard, canopy collapse is an issue that needs to be avoided, particularly in the face of increasing wind on the nose of the canopy. If too much horizontal air movement is combined with insufficient wing loading, then collapse and failure can be expected.

  Modifying the left, right, and center cell rear edge geometry, changes the characteristics of stable flight and control surface reaction time. Meaning brake lines are more effecient, and wing loading transfers canopy rigidity for forward velocity.

  Here is the test video, showing adequate control in 15-20 mph winds, but showing higher control surface reaction than anticipated (very twitchy). I believe that this can be altered by changing the center cell's rear geometry to transfer more of the air column to horizontal velocity, and relying less on the side cell velocity outputs.

  Basically it's working well, but isn't as stable as would be preferred. This can be accomplished by adding length to the rear canopy edge control lines of the central cell.

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