Chute Release Dual Deploy

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dford

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Has anyone put a 12" drogue, 24" CR'd drogue and a 36" main for dual deploy or similar? Something for a high altitude flight. Slow drogue, CR open to slow further and a main even further...is this redundant? Would it get the rocket to drift less under a smaller drogue before a larger opens before main?

Be honest is this a stupid idea? Other than the lines being tangle i'm wondering if it'd get the rocket closer to the pad with less need for tracking.
 

KenECoyote

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I was actually thinking along the same lines this morning. Funny.
 

Bat-mite

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The only purpose for a drogue is to keep the parts separate and the nose down when the main deploys. Drogues are not really there to slow decent. You want the rocket coming down as quickly as possible until it's time for the main.

If you are using a 36" main, then I'm guessing the rocket weighs between 2 and 3 pounds? If so, you probably only need a 6" drogue. You could CR it to open 100' before your main
 

Nathan

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The only purpose for a drogue is to keep the parts separate and the nose down when the main deploys. Drogues are not really there to slow decent. You want the rocket coming down as quickly as possible until it's time for the main.

If you are using a 36" main, then I'm guessing the rocket weighs between 2 and 3 pounds? If so, you probably only need a 6" drogue. You could CR it to open 100' before your main
What is the benefit of the nose pointing down? Last year at BattlePark I saw a large level 3 rocket fall into it's main chute just as it opened because it deployed straight downwards.
 

Banzai88

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Parts separate I'll agree with, but intentionally nose down? It's going to probably be nose down-ish anyway, but I size the drogue to intentionally keep the rest of the rocket BELOW the payload section for main deployment, which can be difficult if the booster section falls flat or twirls with the fins catching the air.

Nathan describes a nightmare scenario. All my main events that have been well to the side, but I have see a few main parachutes that tangled on fins because there wasn't enough separation between parts either through bad luck, not enough shock cord and/or improper shock cord ratios on where the drogue was placed, or just plain too small of a drogue to keep the parts separated.
 
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lawndartman

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I would forget the dual deploy. Pop at the top. Set your CR to pop when you want it to. Less is more. Over thinking things gets you in trouble. just my 2 bits...
 

AlfaBrewer

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If you need a bit of drag to help orient/space the fin can and payload sections, a streamer is a good choice. I use them on lighter DD rockets simply to help with tracking.
 

dford

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I suppose my thinking was dual deploy drogue to slow down the rocket to not rip the main at high decent rates. Orienting is the other half I didn't think about.
Having two small open chutes would probably make cords quite a bit more hairy and just confuse the situation I imagine.

I would forget the dual deploy. Pop at the top. Set your CR to pop when you want it to. Less is more. Over thinking things gets you in trouble. just my 2 bits...
In flights past I've had to find a way to slow recovery events because the manufactured ejection charge wasn't long enough. Sometimes motor deploy won't work.
I'm only beginning to scratch the surface in dual deploy. My mind is racing like a 4 year with too many questions.
I'm already seeing how all the extras like DD and tracking are going to make me appreciate building a successful rocket.
I don't think dual drogue + main will make a rocket anymore successful now though. Probably just more expensive when the extra cords cause it to tumble to pieces when it hits the ground
 
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Bat-mite

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What is the benefit of the nose pointing down? Last year at BattlePark I saw a large level 3 rocket fall into it's main chute just as it opened because it deployed straight downwards.
I don't have data to support this, but here is my visual take on the best deployment position. I guess it doesn't have to be nose down, but if it is, then the direction of the main chute is angled down, and once it begins to inflate, it pulls the nose up, and then the aft section drifts down on the drogue.

nose down.png

main out.png

descent.png
 

Bat-mite

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I suppose my thinking was dual deploy drogue to slow down the rocket to not rip the main at high decent rates. Orienting is the other half I didn't think about.
Having two small open chutes would probably make cords quite a bit more hairy and just confuse the situation I imagine.



In flights past I've had to find a way to slow recovery events because the manufactured ejection charge wasn't long enough. Sometimes motor deploy won't work.
I'm only beginning to scratch the surface in dual deploy. My mind is racing like a 4 year with too many questions.
I'm already seeing how all the extras like DD and tracking are going to make me appreciate building a successful rocket.
I don't think dual drogue + main will make a rocket anymore successful now though. Probably just more expensive when the extra cords cause it to tumble to pieces when it hits the ground
Agreed.
 

cerving

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I don't have data to support this, but here is my visual take on the best deployment position. I guess it doesn't have to be nose down, but if it is, then the direction of the main chute is angled down, and once it begins to inflate, it pulls the nose up, and then the aft section drifts down on the drogue.

View attachment 301003

View attachment 301004

View attachment 301005
^^^ This ^^^

You want the Drogue fairly close to the AV bay, and the Main at the nose end if you can (nose-blow vs. coupler-blow). When the Main deploys, it will be blown clear of the rocket so when it opens the assembly will swing down under the Main.

Coupler-blow is easier, which is why people do it, but you run the risk that either the chute won't get pulled out of the payload bay, or that the lines will get fouled in the AV bay/drogue.
 

Handeman

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I would forget the dual deploy. Pop at the top. Set your CR to pop when you want it to. Less is more. Over thinking things gets you in trouble. just my 2 bits...
I assume by pop at the top, you mean popping the CR held chute and letting it deploy at a low altitude. I would agree. Simple is better.
 

Handeman

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^^^ This ^^^

You want the Drogue fairly close to the AV bay, and the Main at the nose end if you can (nose-blow vs. coupler-blow). When the Main deploys, it will be blown clear of the rocket so when it opens the assembly will swing down under the Main.

Coupler-blow is easier, which is why people do it, but you run the risk that either the chute won't get pulled out of the payload bay, or that the lines will get fouled in the AV bay/drogue.
I'm not sure what you mean by coupler-blow. I've always sized my drogues to make sure the av-bay and payload with the main stayed above the fin can on the way down. Fin cans can do a lot of weird things on the way down, from spinning fast and twisting up shock cords to flying sideways and dragging the upper sections away with it. I like a drogue that keeps the fin can pointed down and not flying while the payload with the main stays well above the fin can.

That configuration cannot prevent the payload section from fouling the main, but it does prevent the fin can from fouling the main. I usually use a drogue that is attached to the payload about 1/10 of the length of the shock cord. i.e 20 ft. shock cord between payload and fin can, the drogue is 2 ft. from the payload. What I did notice with that configuration is that if the drogue isn't too big, fin can and payload hangs directly under the drogue, the payload is usually pointed to the side when the main deploys and as long as the main charge isn't too big and shoots the main way below the payload, there isn't a fouling issue.

Bottom line, I think any type of drogue is better then drogueless where you have ZERO control of the way things fall.
 
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