Multiple Parachutes

[MartyAMC]

I'm finalizing plans for my level III flight next spring and I'm considering using multiple parachutes. My project will weigh about 90 lbs.

For those that have used multiple chutes do you rig them special in any way to ensure they don't tangle during deployment?

Thanks in advance.

 

[Mike Di Venti]

I used to use 2 48" pml chutes in my 5.5" nike smoke.
I folded and wrapped them in nomex seperately then slid them in side by side with some dog barf in first.

At 90# you might want to have the nc come down on its own chute when the main pops.
Size the chute for the weight of the nc only. It should come right down next or near the rest of the rocket.
I do this with my 60# Nike Smoke. 7.5"dia.

Depending on how high you're going you might also consider a 3' drogue chute. It'll reduce the stress on the main(s) they come out.
If the nc comes down separately the main chute can be smaller. Thus a lighter rocket overall.

 

[cjl]

Deployment bags would probably be a good idea. I'd probably also go a bit on the large side so that even if one doesn't work, it comes down at a safe (though perhaps uncomfortable) speed.

 

[troj]

Something to factor in, when using multiple chutes, is that they interfere with each other, and the effective drag produced is lower. Each has 60% - 70% its normal capacity, if I remember right. A friend knows off the top of his head; I just don't remember.

Multiple canopies does increase the risk of entanglement. Two deployment bags velcroed next to each other is very much recommended, to help make sure things come out properly.

-Kevin

 

[WDG]

Multiple chutes look way cool! For such a nice looking rocket that has to be a consideration.

I have seen (but not done it myself) a separate chute for the nose cone, as previously suggested, put tethered to the rest of the rocket. More chance of entanglement. Mark did that on his Entropy Bites rocket (with a 50#+ nose cone) out at Argonia. He had about 40 ft of shock cord tethering the 2 pcs together. He had it sized perfectly and they both fell at nearly identical rates. The line between the nose cone and the rest remained slack the entire way down. That means in that particular instance, tethering them added no real benefit (other than reducing his dread of lots of walking for recovery). Derek often lets his rockets come down on 2 separate chutes and almost always they are right next to each other - at least in plain sight of each other.

Dan

 

[MartyAMC]

First, my thanks to Mike, cjl, and troj for your input.

Dan,

I've pretty much committed myself to the multiple chutes. Making arrangements for Nick to pickup chutes from Mark. 1" nylon shock cords, 2" kevar harnesses, and D-bags ordered and should be here in the next week or so. I'll free bag the nose cone on a 10' chute to pull 3 D-bags off. A little over kill with the 10' chute but I want to make sure the D-bags get pulled. So I may have to walk a little further to get to the nose cone.

 

[kandsrockets]

First, my thanks to Mike, cjl, and troj for your input.

Dan,

I've pretty much committed myself to the multiple chutes. Making arrangements for Nick to pickup chutes from Mark. 1" nylon shock cords, 2" kevar harnesses, and D-bags ordered and should be here in the next week or so. I'll free bag the nose cone on a 10' chute to pull 3 D-bags off. A little over kill with the 10' chute but I want to make sure the D-bags get pulled. So I may have to walk a little further to get to the nose cone.

Marty your setup you should have no problems. Good luck with your L3 attempt.

 

[MartyAMC]

Thanks for the feedback Scott.