Head-End Dual Deployment Details & Explanations Requested

[watermelonman]

Not necessarily. I've been using it with good results in my 3" Punisher HED, but:

1) You need more (like ~30% more)
2) You need to contain it so it doesn't push itself out unburned. I use glove tips inserted into charge wells then I tape it VERY tightly with electrical tape (thanks to cbrarick for this tip!).
3) Ground Test!!!
4) See #3, repeat a bunch more times, add a bit more (0.1-0.2 gram) for launch. If at all unsure, start higher and work down til failure, then up again to safe margin.

YMMV, but I have to work with what I have and I have it working. After my experiences, I lovingly refer to it as "Puss-o-dex". :wink:

That is definitely true, it can be made to work. Sorry if I am a little negative. I have never had a truly successful deployment of this configuration using pyrodex, despite perfect ground testing. I also have never had a failure using FFFFG powder.

 

[Nathan]

That's exactly been one of my concerns. Every time I have tried to pull out a chute, I have had limited success, like 50% success. Blowing out the chute in the direction it must go to deploy has worked every time. I was also thinking about a glove finger-tip charge taped to the nose tip for this very reason, but I was curious was the successful HED users would say.

I am rebuilding a crash-damaged 5" Gizmo (early HED-like attempt led to a no-chute landing) and converting it to HED with a new, FW nosecone. I am mirroring CJ's technique as much as I can. I've read it before, but I still do not have a good feel for getting the chute out with av-bay located ejection charges. Seems like those charges would mash the chute into the nosecone, but obviously folks are having a lot of success with it.

I agree, here is how I did it on my Minie-Magg. There is a 3" diameter tube in the nose cone with the av-bay located at the top end of the tube, so the deployment charge blows the 36" Fruity Chutes main chute DOWN out of the nose cone. There is a friction-fit cap on the bottom end of the tube to prevent the chute from falling out during ascent or at motor ejection. There are vent holes at the base of the nose cone and also at the top of the inner tube and av-bay. It works perfectly, the only disadvantages of this set up is that the apogee drogue deployment is motor ejection only, and also that there is some disassembly required every time I prep the av-bay charge.

 

[KenECoyote]

That is definitely true, it can be made to work. Sorry if I am a little negative. I have never had a truly successful deployment of this configuration using pyrodex, despite perfect ground testing. I also have never had a failure using FFFFG powder.

No worries...it's actually good general advice! lol I ended up with the "Puss-o-dex" when I went to my local gun shop and asked for bp...they said that all they had was left on the shelf and it was just Pyrodex, so I thought it was the same. After much failed testing, I found out it wasn't. Still, I got it to work and if you look at my sig, you'll notice I don't like failures (at least I try my best to avoid them). I basically found out what the differences are and how to mitigate/limit them through extensive research and ground testing.

I can't emphasize the ground test portion enough regardless of what you use. If it doesn't work on the ground, it likely will work it's way into the ground. :wink:

 

[stealth6]

s6, what do you do to protect the antenna? Is it included in the foam wrap and nomex pocket?

Here's a few pics to show how I go about it:

1st pic: the components- a nomex "pocket" (which I cut out of some fireman's pants I got off E(vil)bay dirt cheap), a piece of kevlar cloth (also a cheapie E(vil)bay find, a second from a ballistics vest), a small piece of soft foam (scrap), some flexible electrical tape, the braided kevlar shock cord, and the BRB900 unit itself.
2nd pic: place the BRB900 on the piece of foam.
3rd pic: wrap the foam around the BRB900


4th pic: put foam wrap bundle on piece of kevlar cloth.
5th pic: wrap the kevlar around the foam/BRB900 bundle.
6th pic: place the kevlar/foam/BRB bundle into the pocket.


7th pic: when putting bundle into the pocket, pull antenna through small hole cut in corner of pocket.
8th pic: place shock cord over pocket.
9th pic: roll pocket around shock cord.


10th pic: do a nice tight wrap of electrician's tape around ends of bundle, and you're good to go. (unless you've forgotten to plug the battery in and turn the unit on - ask me how I know this.)


Works fine. Electronics are protected both from ejection charge blasts, and from knocks and bumps. Unit (& antenna) is outside of rocket airframe from apogee all the way down, so much more chance of getting a solid lock and good communication.

There are lots of ways to go about this, but this is one that works for me (of a few different ways I do it myself).

Try it, it will likely work for you just as well,
s6

 

[kjkcolorado]

Here's a few pics to show how I go about it:

1st pic: the components- a nomex "pocket" (which I cut out of some fireman's pants I got off E(vil)bay dirt cheap), a piece of kevlar cloth (also a cheapie E(vil)bay find, a second from a ballistics vest), a small piece of soft foam (scrap), some flexible electrical tape, the braided kevlar shock cord, and the BRB900 unit itself.
2nd pic: place the BRB900 on the piece of foam.
3rd pic: wrap the foam around the BRB900
View attachment 274690

4th pic: put foam wrap bundle on piece of kevlar cloth.
5th pic: wrap the kevlar around the foam/BRB900 bundle.
6th pic: place the kevlar/foam/BRB bundle into the pocket.
View attachment 274691

7th pic: when putting bundle into the pocket, pull antenna through small hole cut in corner of pocket.
8th pic: place shock cord over pocket.
9th pic: roll pocket around shock cord.
View attachment 274692

10th pic: do a nice tight wrap of electrician's tape around ends of bundle, and you're good to go. (unless you've forgotten to plug the battery in and turn the unit on - ask me how I know this.)
View attachment 274693

Works fine. Electronics are protected both from ejection charge blasts, and from knocks and bumps. Unit (& antenna) is outside of rocket airframe from apogee all the way down, so much more chance of getting a solid lock and good communication.

There are lots of ways to go about this, but this is one that works for me (of a few different ways I do it myself).

Try it, it will likely work for you just as well,
s6

Thanks s6. Will definitely give this a try.

 

[ChrisAttebery]

Why can't you wire your apogee charge from the top of the altimeter bay down the outside of the parachute compartment and through the thick centering ring?

I'm looking at doing a similar setup on my 7.5" Door Knob. I've tried using a cable cutter twice and the parachute has deployed at apogee both times.

It works perfectly, the only disadvantages of this set up is that the apogee drogue deployment is motor ejection only, and also that there is some disassembly required every time I prep the av-bay charge.

 

[watermelonman]

Hah, when I have cable cutter failures I tend to hit the ground on drogue. Your failure mode seems a little better.

 

[Nathan]

Why can't you wire your apogee charge from the top of the altimeter bay down the outside of the parachute compartment and through the thick centering ring?

I'm looking at doing a similar setup on my 7.5" Door Knob. I've tried using a cable cutter twice and the parachute has deployed at apogee both times.

Yes that would work.

I also had problems using a cable cutter. This Minie-Magg was originally built to use with an Archetype cable cutter but after two flights that didn't go well I decided to convert it to dual deploy.

 

[tim cubbedge]

In my Punisher - and in some of my other rockets - I attach my tracker to the drogue shock cord, about 2' away from where it clips to the rear AV bay lid.

I use a BRB900 GPS. What I do is wrap it first in some soft foam, then that gets wrapped in a special nomex "pocket" that I made, then I do a really health tape wrap around the whole bundle (which also fastens it to the shock cord). Works great.

s6

Did you add that rubber duck antenna to your BRB after you bought it or was that an option?

 

[stealth6]

Did you add that rubber duck antenna to your BRB after you bought it or was that an option?

This is an option through BigRedBee. See it here - https://bigredbee.com/brb900_antenna.htm - as "OPTION 3".

What I do is wrap and tape a small loop in the short adapter cable. This way the antenna ends up positioned in roughly the same way/space as "normal" but there is a bit of give in the system in the case of a hard landing, such that the mount itself doesn't take a hard shock and is therefore less susceptible to damage. I also get 2.1 dBi of gain with the Dipole antenna.

By the way, here's a shot of the whole recovery system on it's way down after mains deployment:



s6

 

[tim cubbedge]

Thanks. So just wrapped in Nomex, no foam padding?

 

[stealth6]

Thanks. So just wrapped in Nomex, no foam padding?

See post #34.
Actual transmitter is wrapped in foam, then kevlar cloth, then nomex cloth.
Rubber duck antenna sticks out of this bundle and is not wrapped/protected (except for at the base/connection)

s6

 

[hball55]

I was wondering if anybody ever reversed the chutes, with the drogue in the nosecone and shearpins below the coupler to keep the nosecone/body tube from separating at apogee. I have a Kevlar drogue that would easily fit in the upper nosecone without having to do a burrito wrap. Just wonderin'

 

[tim cubbedge]

I was wondering if anybody ever reversed the chutes, with the drogue in the nosecone and shearpins below the coupler to keep the nosecone/body tube from separating at apogee. I have a Kevlar drogue that would easily fit in the upper nosecone without having to do a burrito wrap. Just wonderin'

You could but you can't use motor ejection as backup.

 

[markkoelsch]

I was wondering if anybody ever reversed the chutes, with the drogue in the nosecone and shearpins below the coupler to keep the nosecone/body tube from separating at apogee. I have a Kevlar drogue that would easily fit in the upper nosecone without having to do a burrito wrap. Just wonderin'

I have been thinking the same thing for a while. Frankly, trying to pack my main and harness into the space seems problematic to me.

I wonder if the opening shock of the drogue would be a problem with shear pins. Would need to size appropriately for sure.

 

[markkoelsch]

You could but you can't use motor ejection as backup.

I have not run motor backup in 15 years. With the quality of today's avionics I am not sure if that is needed.

 

[kramer714]

For what is is worth, there was a punisher drag race at ROCstock this summer on K1440 motors. This didn't leave much room for laundry. All of them were HED deployment and all had trackers.

I was able to put a 48" topflight and a rocket hunter into the nose cone, burrito wrapped, to protect the charges. I did have the main charge on the top of the chute (peak of the cone). Most people used 8-12" drogues and 30-48 inch chutes.

I 3D printed sleds for the avionics. there is room for a tracker in there too, not sure the best way to put in the antenna.

 

[crossfire]

Kramer how did your deployment work out? Some put main charge coupler bulk plate.

 

[kramer714]

Kramer how did your deployment work out? Some put main charge coupler bulk plate.

Mine worked fine, I assume you are talking about placing the charge at the tip of the cone (push the chute out) vs put the charge at the coupler plate (push the chute into the cone).

I did it primarily because I figured with that high of a thrust to weight ratio the chute would be pressed firm against the coupler and I didn't want the charge burning the chute and nomex. I figured that there would be a more of a cavity in the tip.

Mike K

 

[CTom]

I was wondering if anybody ever reversed the chutes, with the drogue in the nosecone and shearpins below the coupler to keep the nosecone/body tube from separating at apogee. I have a Kevlar drogue that would easily fit in the upper nosecone without having to do a burrito wrap. Just wonderin'

hball55,

I had 2 flights at Airfest this year using HED with the drogue in the nosecone.
1st flight was a MD 98mm on a CTI N1560 to 41K' and the 2nd flight was a MD 98mm on a CTI O3400 to 47K'. Both successful.
There were 6 shear pins holding the AV-bay to the airframe and 6 more for the nose cone to the AV-bay.
I choose to put the drogue in the nose cone because of CO2 deployment. I used a Peregrine CO2 system. Because of the orientation of the system, I was concerned that if the drogue was below the AV-bay, acceleration on takeoff may force the CO2 cartridge into the pin causing premature deployment.
It all worked out well.

CTom

 

[Rocketjunkie]

When I built my 7.5" Goblin in 2010, I deployed the main from the nose cone (so a 98-6G motor would fit). Details in this thread https://www.rocketryforum.com/showthread.php?8709-Almost-a-Goblin

 

[ChuckH]

Why can't you wire your apogee charge from the top of the altimeter bay down the outside of the parachute compartment and through the thick centering ring?

I'm looking at doing a similar setup on my 7.5" Door Knob. I've tried using a cable cutter twice and the parachute has deployed at apogee both times.

Hi Chris,

What cable cutter setup were you using? Did it use a zip tie, by chance?

Chuck

 

[DizWolf]

I have not run motor backup in 15 years. With the quality of today's avionics I am not sure if that is needed.

I used to be all about motor backup. Then when I started running into the situation where even Long delays were way too short I started plugging and realized just how bad motor delays are compared to electronics. Even running them long is more of a risk than just not having them.

 

[blackjack2564]

I used to be all about motor backup. Then when I started running into the situation where even Long delays were way too short I started plugging and realized just how bad motor delays are compared to electronics. Even running them long is more of a risk than just not having them.

You as a rocketeer have traveled the "True" path & finally attained enlightenment!

 

[Andrew_ASC]

Bumping this thread for the educational value.

 

[TimothyG]

Bumping this thread for the educational value.

I was literally mulling this over tonight thanks for bumping it. Wanted to see what justification was presented for HED with main and drogue placement. Now I’m feeling more comfortable about having the drogue in the nosecone.

 

[Mustang67]

I am thinking about creating a HED for a 3" PML kit I have. Relying on the altimeter for separation then a Jolly Logic Chute release for the main. Has anyone done this yet on a PML kit or a 3" kit with a plastic nose cone?

 

[blackjack2564]

You can't do Head End Deployment unless main is in NC, you must do some type of hybrid unless you do this, which i designed for plastic cones....
Now you have standard dual deploy with altimeter. Apogee blows off coupler/av-bay and main blows off NC.

You can convert any plastic NC to HED by cutting bottom off leaving just 2inches of shoulder to glue a 3-4 in section of airframe on. Then av-bay will slide right in.

What you are talking about is dual deploy from single "break" in airframe. Done by many by the way.

 

[Mustang67]

Got it and ty Jim!

 

[Tim51]

You can't do Head End Deployment unless main is in NC, you must do some type of hybrid unless you do this, which i designed for plastic cones....
Now you have standard dual deploy with altimeter. Apogee blows off coupler/av-bay and main blows off NC.

You can convert any plastic NC to HED by cutting bottom off leaving just 2inches of shoulder to glue a 3-4 in section of airframe on. Then av-bay will slide right in.

What you are talking about is dual deploy from single "break" in airframe. Done by many by the way.

View attachment 387555

Thanks for posting this. What's the best way to secure the eye bolt in the inside tip of a plastic NC in this configuration? I've considered trying it but without a stepped aluminium tip I was concerned that embedding the eye bolt in rocket caviar and cross wires wouldn't be enough (..?)