This one's been at the back of my brain for a while.

Craig, when you talk about parachutes shredding with deployment speeds in excess of 20 fps, are you thinking in terms of traditional plastic parachutes?

If that's the case, then it seems that nylon chutes would be *much* sturdier, and therefore capable of withstanding the higher speeds. But then would that take into account the additional strain placed on the whole recovery system?


As usual, (WIERD, according to MarkII) inquiring minds want to know.


Cheers,

__________________
Jay Goemmer
"Centuri Guy"/"Tau Zero"
YORF Member 28
Semroc SAM #0029
NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014

Jay,

Yes, I'm thinking about the typical plastic "parasheet" type that we use most often. That's what most builders will have available, whether they buy it separately (like from Semroc), make it from a garbage bag, or use one they already have from a previous kit.

You could probably allow for higher Dv's if you know the parachute is capable of taking the stress. I'm staying with the idea that lower Dv's are better, no matter what the recovery system can handle. Keep in mind, a stronger parachute often results in a heavier parachute, which takes its toll on the upper performance. Lighter is better, so the "engineering principle" is to lower the Dv as far as possible.

__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
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SAM 0044
AMA 352635

I always correlated "shred" to shroud line separation, not actually the parachute material shredding. Granted, with nylon or heavier parachutes, the shroud line attachments are "beeffyer" (is that even a word?).

__________________
Don
NAR 53455
"Carpe Diem"

Pretty much the same effect -- you lose the parachute at the wrong moment...

What I've noticed when I have a line come out is that it generally tears through the plastic. I like to use the two-hole slip-knot attachment method, with the sticky paper reinforcement. If the plastic material is torn, then it still counts as a shred to me. It's the end result of the canopy "popping" open with a gunshot bang, meaning it was moving too fast. This type of failure happens more often than having the line itself break.

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Craig McGraw

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SAM 0044
AMA 352635

After too many melted chutes, I ordered Top Flight's thin mil nylon for my modrocs. No regrets and not much of a weight penalty. But the thing I like the most is the day-glo orange color. It really stands out in the sky and when it is on the ground. I ordered different sizes and used a permanent marker to tell me what size it is. Come to think of it, I really need to write my name and cell number on it, just in case!

http://topflightrecoveryllc.homestead.com/thinmil.html

Greg

They nylon chutes Semroc ships in the SLS kits are no pushover and can handle much higher DV's than expected.

Last time out with my SLS Hustler and I had a severely weather-cocked launch due to some wind that had picked up and a late delay with a G38-7FJ single use. It was a completely arching flight with chute deployed only a couple of hundred feet off the ground ... it was really moving. I would have bet money that the chute would have snapped at least a few nylon shroud lines or zippered the kit. It was in perfect condition and my electronics in the payload section were spared but I did have a cracked fin that I still need to repair from the hard landing. I attribute that save not only to the nice nylon chute but also to the beefed up parts in the recovery system for that rocket that includes the ECR-236 elastic cord & SCK-418 kevlar leader. I was impressed.

I generally sub nylon chutes for everything unless it's light enough to drop with a streamer. Don't use plastic at all anymore. I have some little 9" & 12" nylon chutes that work real well in smaller rockets.

.

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__________________
Steve Naquin
TRA# 677 L2
NAR# 85518 L2
SAM# 0052

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🚀 In Paint & Detail: USR Banshee
🚀 In Build Queue: Estes Doorknob w/Vander-Burn Rocketry Upgrade Kit [Sport Decor], Semroc Centurion-F, Semroc Egg Crate
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Greg, I really like the Top Flight nylong chutes as well and can recommend them highly. And you're right, the thin-mil chutes are, indeed, thin and quite light.


Steve, I still use plastic chutes in some of my rockets, mostly the smaller ones, but I definitely use a nylon chute whenever I have one that will fit and is sized appropriately for the rocket and flying conditions.

__________________
John Thro, NAR #84553 SR
I was too old when I started! Now I'll *never* become a BAR!

I have the PAR- 9TM & PAR- 12TM from Top Flight

I also have a small 9" ish or so chute from a LOC Precision Lil' Nuke kit that I've been having for years that just won't die

.

__________________
Steve Naquin
TRA# 677 L2
NAR# 85518 L2
SAM# 0052

🚀 In Construction: Der Blue Maxx/Minie-Magg 5.5” & Vander-Burn MDRM Clone w/Stickershock23 Custom Decals
🚀 In Paint & Detail: USR Banshee
🚀 In Build Queue: Estes Doorknob w/Vander-Burn Rocketry Upgrade Kit [Sport Decor], Semroc Centurion-F, Semroc Egg Crate
🚀 In Repair: SLS Lil’ Hustler, SLS Aero-Dart 1969 Trim
🚀 Stay Tuned For Fall 2021 Launch Dates