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Dual Deploy in Stubby Rocket

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emaher

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I'm working on an Estes Big Daddy upscale based on 7" PML tubing. I'd like to do some form of dual deploy on this bird, but am not quite sure how to go about it.

I've been thinking that I'll use engine ejection to deploy the drogue. I'll then use my Hi-Alt-45 to deploy the main. I'm wrestling with how exactly to achieve this. Perhaps a chute compartment between the fins...?

Anyone over tried anything like this?

Thanks for any advice!

-Eric
 

dixontj93060

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I have a number of rockets with this setup:

  1. Nosecone resident altimeter
  2. Defy Gravity tether (or other release device)
  3. Main chute "burrito"-wrapped in a shield or held in a closed deployment bag
  4. Drogue or drogueless apogee event via accel-based altimeter or motor deploy
  5. Main event via altimeter firing release device and freeing main chute

You can alternatively mount your alt between fins and have the tether hold the main inside the airframe, but then you risk damaging the inside of your airframe (at least with the Defy Gravity tether--other designs might be superior in this regard.
 

hardinlw

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I did a 7.5" Fat Boy with the drogue out the rear and the main out the front. Basically, I ran a 54mm tube parallel to the motor tube between two of the fins and put the altimeter (PML co-pilot setup) into the top of that tube. The bottom end of that tube contained the drogue and was capped with what was basically a PML piston held in place by a couple of shear pins. The main went into the normal place. Issues to consider are the lack of room for the drogue, the need to use shear pins to keep the drogue from deploying under the acceleration of the launch, and the potential for the drogue and main getting tangled. The rocket arced over and deployed the drogue which stabilized it nose-down, but slightly cocked because the drogue was off-center. When the main deployed, it was thrown sufficiently to the side so that the main and drogue did not tangle. The rocket did look a bit odd coming down with a chute on both ends. (You want to make the main shock cord long enought that the two chutes could not twist together during descent.)
 

DAllen

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Chute cannon?

I am working on a project with a 28' main that is in a burrito of sorts. We got it all compacted into a 6" tube about 34" long. We pack the chute ultra tight and put it inside a coupler that is cut in half length-wise. Coupler + chute is inserted into 6" tube with a piston at the base. A small charge (3g of FFFg I think) below the piston is all that is needed to push the entire assembly out the cannon. A little dash of graphite powder and the dumb thing just about slides out under it's own weight.

Needless to say, ground testing is essential. The big disadvantage to this is all the pieces that float down after deployment that we have to find. With some fluorescent colored streamers I think they ought to be easy to spot.

-Dave
 

emaher

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Thanks to whoever suggested the Defy Gravity Tether. Seems like an elegant solution.

I think the easiest thing is to place the electronics in the nose, use motor ejection to deploy drogue, and use the Defy Gravity Tether to deploy the main.
 

dixontj93060

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You are welcome. And Defy Gravity is open for business again with a sale on pre-orders.

Thanks to whoever suggested the Defy Gravity Tether. Seems like an elegant solution.

I think the easiest thing is to place the electronics in the nose, use motor ejection to deploy drogue, and use the Defy Gravity Tether to deploy the main.
 

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