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L3 Chute Deployment Suggestions
#1
Problem: Chute tangles in the shock cord and nose cone chute does not deploy.

On my L3 attempt the d bag came out and deployed the Main chute.  The Main tangled in the 30' shock cord.  The nose cone chute did not deploy at all.  The D bag and nose cone chute are packed inside the nose cone (10" Bull Pup).  Nose cone shot away from the av bay as anticipated but the chute did not deploy.  It was packed separately in a protector along side the d-bag.  There was no pilot chutes used.

Suggestions?  Pictures?  Details on a fix?
Jim Goggins NAR  L3
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#2
(07-26-2011, 05:47 PM)Jim Goggins link Wrote:Problem: Chute tangles in the shock cord and nose cone chute does not deploy.

On my L3 attempt the d bag came out and deployed the Main chute.  The Main tangled in the 30' shock cord.  The nose cone chute did not deploy at all.  The D bag and nose cone chute are packed inside the nose cone (10" Bull Pup).  Nose cone shot away from the av bay as anticipated but the chute did not deploy.  It was packed separately in a protector along side the d-bag.  There was no pilot chutes used.

Suggestions?  Pictures?  Details on a fix?

My suggestion.  Use a drogue chute on the nosecone and your DG tether to control the main deployment.

At ejection deploy the nose cone and make sure the nc drogue deploys.  you can ensure this by attaching the nc dbag to the booster and have the nc pull the chute out of the dbag when the nc is ejected off.

The NC chute should be sized so the descent speed of the nosecone + chute is less than the booster if they were separated. This is not a straightforward calculation especially for the booster.  Sizing the NC for less than 40 ft/sec descent speed is probably a good first step as the booster would likely fall faster than that. 

This will ensure that the NC is above the booster under drogue.  This is a critical factor though.  If there isn't a natural descent speed difference between the nc and booster then there will be no tension in the shock cord available to deploy your main.

Then the tether is rigged so that it is keeping the shock cord from the NC from pulling the dbag off the chute which is attached to the booster bulkhead.

When the tether is fired the shock cord will pull the bag off the shoot keeping the shock cord well away from the chute rigging.

If you do not want to go the tether route and use traditional 2 breaks, then the descent speed this still applies. You need tension in the shock cord during descent.
John Derimiggio
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#3
After a lot of examination, reviewing suggestions, consulting with others ( namely Linda who came up with the best method) over my chute issue, I have decided on this:

Due to the heavy weight of the nose cone, I am going to deploy a 9' chute at apogee and get it away from the rest of the rocket.  The nose cone will have a tracker in it.

The main booster section and coupler/av bay will come down from apogee under a 5' drogue.  At 900' the booster section will separate from the coupler pulling the D bag off the 14' main.  This section will also house a tracker.   This deployment method should prevent any tangling of shock cords and chutes, as well as ensure that the nose cone is no where near the rocket to inflict damage.
Jim Goggins NAR  L3
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#4
Is the main part of the rocket gonna split?
Bill Clune L2 | NAR#88583
MARS Club|SRC|METRA|MDRA - Forever
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#5
(07-29-2011, 07:44 PM)Jim Goggins link Wrote:as well as ensure that the nose cone is no where near the rocket to inflict damage.

What about the rest of us?
John Derimiggio
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#6
Stay in Ohio until September  ;D

N
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#7
(07-30-2011, 01:01 PM)jderimig link Wrote:[quote author=Jim Goggins link=topic=206.msg2308#msg2308 date=1311983041]as well as ensure that the nose cone is no where near the rocket to inflict damage.

What about the rest of us?
[/quote]

Remember John, look skyward. I ensure nothing.  ;D
Jim Goggins NAR  L3
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#8
(07-30-2011, 11:13 AM)Bill Clune link Wrote:Is the main part of the rocket gonna split?

Bill.  The main part will come down slowing with a 5' Drogue attached and then will split at 900'.  The booster will have a 14' main attached and the av bay continues down on the 5' drogue chute.  Three pieces of rocket with three chutes.  Oh, and 3 rf trackers to boot.
Jim Goggins NAR  L3
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#9
defy gravit tether?
Bill Clune L2 | NAR#88583
MARS Club|SRC|METRA|MDRA - Forever
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#10
I think Jim is sying that the nosecone leaves at apogee on a 9ft. chute.  The av bay and booster fall under a 5ft drogue to designated altitude (900ft.) still attached with bluetape adn shear pins.  When the second (main) charge fires the AV bay and booster seperate completely with the booster under 14' chute and the AV Bay under a 5ft. chute (the drogue).  All pieces independent with own chutes.  No tether required. Right, Jim?

Dale
Dale Stoyer - L3
NAR #91256
TRA #13499
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