parachute location on shock cords

[AP aroma]

I am building a fairly standard dual-deploy rocket. IT will have a lower airframe housing a drogue chute, an upper airframe housing the main chute, with an AV-bay in-between. I am aware that you want the parachute for the apogee event and main event located not in the middle of the shock cords because the parts of the rocket might collide during descent. I am thinking I will attach each of these chutes about one third of the way along the shock cord but I'm not sure if they should be 1/3 away from the AV-bay or 2/3 away from the AV-bay. Can any of you fine folks help?

Thanks,
Jim

 

[JohnCoker]

I generally put it closer to the AV bay, since the aft section is the heaviest and I would prefer that to touch down first. This reduces the likelihood of the aft section coming down on top of another section and damaging it.

 

[waltr]

I put the Drogue closer to ebay, about 1/4 to 1/3. What you want here is to see the ebay - booster seperate and the shock cord form and inverted 'V' while on the drogue. Then when the charge for the Main goes off, the nose cone and main moves away from the booster.

The Main I put closer to Nose, again by about 1/4 to 1/3.

Then under Main it parts land in the order, Booster, Ebay, Nose.

On each deploy, you want the lengths to be different enough so one section does not hit the lower section.

 

[JoePfeiffer]

You're right that the one absolute rule is don't make them equal. I figure the fin section will be going much slower than the rest due to the ejection charge, so I put it on the short end.

The nose cone is much, much lighter than the rest, so I put that on the short end. For relatively small rockets, I might not use a shock cord on the nose at all.

 

[AP aroma]

Thanks guys, several different opinions here, but the one that is unanimous is don't have the chute in the middle of the cord.

Jim

 

[MidOH]

I put the drogue on the bottom of the ebay. So it comes down like a normal rocket, just with a really long nose cone.

 

[Funkworks]

Thanks guys, several different opinions here, but the one that is unanimous is don't have the chute in the middle of the cord.

If in the middle, the nose and airframe could knock onto each other. A rocket I'm building has a heavy nose and the last thing I want after deployment is for the nose to smash into the fins.

 

[teepot]

I agree, closer to the av bay and closer to the nose cone about a quarter way down the shock cord.

 

[Onebadhawk]

https://www.onebadhawk.com/why-a-3rd-loop.html