Comrades:

Would somebody (who knows) talk me through the theory of X-shaped parachutes, please?

Less drift?

Use the next size larger because it has less area?

Is it strictly aesthetics?

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wait to see the answers you get

I have seen some folks claim that the X shape gives less drift, altho the only way that really works is if this chute shape has a higher rate-of-descent (less time in the air, less time drifting in the wind). But then it hits the ground harder. And you can accomplish the same thing with a smaller round chute, or a round chute with a bigger spill hole.

To me, the biggest single advantage would be that when constructing mid-power (or high-power, if I built those) chutes from heavy fabrics that require sewing, making the two rectangular panels might be easier to sew and would require fewer shroud lines. I could see that an X-shape would pack a little more simply in tight spaces. But that's about it.

I don't think it's a big deal either way.

less drift, only if you swap out say an 18" hex chute for an 18" x-form. an x-form has about 75% of the surface area of hex chute, so an 18" x-form is roughly equivalent to a 15" hex.
they do pack nicely though. I like them because I can use a bigger easier to see chute. I would suggest that possibly an 18" x-form is nearing the edge of minimum size, smaller than that and they start to get tangled up in the shrouds(untangling them gets...interesting(with words of power being considered)).
Rex

Dragsters sometimes used them in the 1970's--as opposed to round ones, but I don't know why.

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One of the design features of the X-chute was softer opening. As I understand, it was originally designed for high speed deployment without the initial opening shock of a standard chute. It was thought that as airplanes went faster, it would allow the pilot to bail out without becoming six inches taller in the process. Of course ejection seat tech advanced pretty rapidly and was a better solution.

Those features were perfect for a parachute used as a decel device though, and they ended up behind dragsters, etc. The Russians like to use them behind fighters and fast bombers, while the US went with ribbon-type decel chutes.

I use X-chutes quite a bit. I have noticed that they do seem to drift a bit less than standards, but I've never actually done any testing. The qualities listed above do make them a great choice if you aren't sure about that delay time though!

Several comments here ring true. They open softer, have less lift, have far better flow through for higher speed deployments. They are smaller than an equivalent hemispherical chute even with a 15% spill hole. The side openings act as large spill holes.

It is especially important to make sure the lines are properly positioned or it spins.

Any chute on a heavy potentially high speed deployment rocket should use a slide ring like a key ring or reverse wound masking tape.

Jerry

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I do not have any, but interested in knowing what views are -- Ive always like the looks of them. Also like the looks of The Rocketman Chutes, which look like the love child of a regular chute and an x-form chute.

http://www.the-rocketman.com/chutes.html

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X chutes are something I hadn't thought about for rockets but then I do low power. Do recall the dragster and aircraft applications, and seeing them spinning. (Were the 70s and 80s really that far back? Really? Can't be, just can't be.) The Rocketman chutes are a new one to me. Interesting.

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The four shroud chutes are cool. They need 15% spill holes.

__________________
Exemptions not regulations. Please support DOT treating slow burning solids as not subject to HMR. 2015 NAR President declines!
U.S. Rockets instaship. http://bit.ly/1aca7mA Please buy some rockets.
The O administration believed in tax, spend, borrow, fine, mandate, monologue. D voters will soon be very happy with the election outcome!
Model rocketry is as safe as safe can be defined in human existence. Bow and pray: GH Stine, Orville, Vern, Lee, Lonnie, Carl, etc. No, really.