Parachute recommendations.

[Mark Gledhill]

Hi All

After a bit of advice on a suitable parachute please.

My finished payload with a Pi Zero running PITS and an Arduino based backup tracker comes in at around 120g, maybe 125 accounting for gaffer tape and tethers. The smallest pre-made chute I can get hold of is 12 inches, this gives me a descent rate of 6.5 m/s which is a little hot for my taste. The next size up is 18 inches which comes in at 3.5 m/s which is a bit more leisurely than I'd like and will mean a longer retrieve.

At the risk of sounding a bit Goldilocks about the whole thing, I really need one that comes in somewhere down the middle. I know Estes make a 15 inch one but I'm not sure I trust a flimsy polythene chute and I'm not sure how I could attach it to the balloon without risking tearing it.

Any advice would be most welcome.

Many Thanks

Mark

[John Laidler]

It is possible to "reef" a larger chute so it doesn't open up so much.  But I guess this is a bit hit and miss!

John

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[David Akerman]

Yes, you can reef the larger chute, and that's probably what I would do, but that said 6.5m/s for a 120g payload is fine.

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[Steve]

I'd add to that and say you might want to make some form of weight allowance for balloon remnants (unless you plan to cut them off at burst).  Depending on the balloon it could easily be a couple of hundred grams. Again difficult to judge how much aerodynamic drag they might have - depends if its just the neck or more, how clumped up it is ....  Bit of an imponderable

Its also worth saying that the Rocketman chutes include a spring loaded cord lock for reefing - the sort of thing you find on coats.  It slides up and down the lines - so you can adjust the amount of reefing.

    https://www.flickr.com/photos/16828840@N07/50019329112/in/dateposted-public/

You could easily add similar to most chutes.

Sorry I don't have any data on how much to use - a few drop tests might dive you an idea.

    Steve

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