Doing a DDSEJLCR

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David Schwantz

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I am doing a dual deploy, single eject with a JLCR. Will have a 3' drogue chute and a 9' main. I normally use a third loop in my cords for chute attachment. How do you suggest to locate the drogue and main for this type recovery?
 

Cameron Anderson

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I am doing a dual deploy, single eject with a JLCR. Will have a 3' drogue chute and a 9' main. I normally use a third loop in my cords for chute attachment. How do you suggest to locate the drogue and main for this type recovery?
How long is your shock cord going to be?
 

Cameron Anderson

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I drew this out to make a little more sense...

Bottom line, I think you need a longer shock cord. I'd go min 25', and 30' to be safe.

You need enough length on your shock cord to allow your chute to lay fully out while it inflates and not tangle with the drogue. In addition, you need a long enough shock cord to pull your out of the airframe if the JLCR accidentally releases in the tube (or, more likely, the rubber band gets cut).

I made some rough estimates based on standard chute dimensions on how much room you need between your drogue and where you attach the main, and between the main and the airframe.

Measure your specific chute and the dimensions will change some, but the estimates will be close. At most, with a 20' cord, you have 10' above your chute and below your chute of you mount your main right in the middle of your shock cord...your chute laid out fully is at least 12' so you run the risk of the main tangling with the drogue (not a huge concern, but it is a concern), but more importantly, only 10' of cord could leave the main in the airframe even with a drogue and 20' of the shock cord fully extended.
 

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Antares JS

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To add to what Cameron Anderson said, locate the drogue on top, maybe one or two feet back from the nose. If your main gets stuck but your drogue ejects, your drogue can hopefully pull the main out the rest of the way. Definitely get at least a 30' shock cord and locate your main between 1/2 and 1/3 of the way from the nose to the main body.
 

o1d_dude

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AE44220B-EC6A-472A-A99E-6ABAB17CCD9D.jpeg


DD/SE/JLCR in action.

Drogue attached to the nosecone.

Main/JLCR attached between nosecone and booster.

Booster is already on the ground.

The little thing above and to the left of the main is a Fruity Chutes “slipper” used like a burrito for the main. It’s attached to the top of the chute.

Main chute is a Fruity Chutes 42”

Rocket is a Polecat Goblin 5.5 and weighs about 5.5 lbs. Ironic, innit?

This arrangement was found to be the least likely to experience unexpected events over about 6-7 flights. Once I got it nailed down, I certed Level 2 with this rocket using this method.

Hope this helps.

Obligatory plug for One Bad Hawk: The shock cords are from his shop.
 

David Schwantz

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3d printed her with files provided from Dave's Rocket Shop. 8"dia, 22lbs depending on motor choice, blue tube for body under printed outer layer. Went with a bit larger chute due to she will land on the fins and engine fairings. Fins are TTW 5/16" ply and the fairings were made from Mach 1 3" glass couplers. So I was shooting for 12 to 13 fps on decent. Also she will fly with the fake engines, made them from stainless cups and they are designed to be expendable. The main and drogue in the blanket do not even take up half of the chute compartment.
 

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Cameron Anderson

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3d printed her with files provided from Dave's Rocket Shop. 8"dia, 22lbs depending on motor choice, blue tube for body under printed outer layer. Went with a bit larger chute due to she will land on the fins and engine fairings. Fins are TTW 5/16" ply and the fairings were made from Mach 1 3" glass couplers. So I was shooting for 12 to 13 fps on decent. Also she will fly with the fake engines, made them from stainless cups and they are designed to be expendable. The main and drogue in the blanket do not even take up half of the chute compartment.
Beefy, I like it.

Motor arrangement?
 

David Schwantz

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54mmt, Aeropack Flanged mount. I think this is what you were asking?
 

David Schwantz

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Hi Greg, yes I will be. But our launches were cancelled for the 13th. Hopefully July 11 and 12 will happen. I will let you know. Dave.
 

David Schwantz

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Hi Greg, thanks. that was taken at our club field. KLM farms in North Branch. We fly off the sod farm portion. They also have lots of corn:( Also flew the grain bin and my L3 flight.
 

Greg Furtman

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Hi Greg, thanks. that was taken at our club field. KLM farms in North Branch. We fly off the sod farm portion. They also have lots of corn:( Also flew the grain bin and my L3 flight.
Hi Dave, yup, searching for a rocket in a cornfield sucks, especially when you are short & have short legs. :music1: The fields to the east and south & north are soybeans this year. A lot easier to find things.
 

David Schwantz

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We had a jet go down in beans years ago. Took us 4 days to find it:)
 
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