Saturday, September 29, 2018

The hours before...

Today is clear and comfortable, with light winds out of the NNE - perfect for the Geezer TARC launch in a few hours...

Ready to compete!

I'm all packed up, with altimeters charged, eggs weighed, rockets loaded with parachutes, and low power pad/controller bagged for use by the modroc flyers. So why did I fret last night, and why I am still fretting?

Because I have doubts about the parachute sizes I have chosen for the payload section, that's why! I woke up in the middle of the night and revisited my descent rate calculations using three different utilities - 2 online, and the app on my iPhone. And I'm still reviewing them this morning, wrestling with the basic issue, which is that all the numbers indicate my chosen 12" parachute size is marginal for the challenge, producing a descent rate of around 23 feet per second. A tad too fast, but the next commercially available size - 15" - would definitely keep the eggs up there way too long. I am wishing I had the talent/ability/motivation/etc. to make my own rip stop nylon parachutes, because I sure could use a couple of 13" diameter hexagons right now. Alas, it's too late, and I'm going to have to make do with what I've got.

Top Flight parachute compared to that from BAMA (hexagon vs. octagon)

To show you how nervous I am, I opted to use some new parachutes I ordered from BAMA Recovery Systems instead of my tried and true Top Flight brand. The BAMA chutes are octagonal in shape, with 8 long shroud lines instead of 6 - this supposedly increases the parachute drag coefficient, slowing the descent. I'm a) hoping this is the case and b) they can take the stresses that are going to happen with that egg capsule is ejected from the sustainer. It'll be very sad and messy if those shroud lines break.

I'm also second-guessing my motor choices, but that's normal before a Geezer TARC launch. We'll see how things go on the field.

Stay tuned...

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