HED With a Deployment Bag?

[PBic]

I’ve fit (crammed) my parachute, shock cord and blanket into the nose cone of my HED 4” rocket, and it’s pretty snug. Im a little concerned that a single yank is going to pull it all out. I mocked up a deployment bag, and with a small bit of continuous tension to simulate a pilot chute, the main chute comes out of the bag ok. Has anyone else flown with a configuration like that?

Thanks!

 

[jd2cylman]

For HED I always fasten the chute to the AV bay bulkhead. This insures the chute deploys as long as the nose cone comes off the AV bay. Works for me... I just burrito wrap my chute with Nomex.

 

[PBic]

For HED I always fasten the chute to the AV bay bulkhead. This insures the chute deploys as long as the nose cone comes off the AV bay. Works for me... I just burrito wrap my chute with Nomex.

Thanks Adrian. Is your deployment charge on the bulkhead, or in the tip?

 

[jd2cylman]

Thanks Adrian. Is your deployment charge on the bulkhead, or in the tip?

For the nosecone I always put it in the tip. This makes sure the cone is empty on deployment. I've seen the chute blown into the cone on deployment and stayed in there...

 

[rfjustin]

What size chute and make/model are you using? What is the weight of the rocket in question?

 

[PBic]

What size chute and make/model are you using? What is the weight of the rocket in question?

The chute is a 60” SkyAngle Classic II, and the apogee weight, including chutes, is going to be right about 5700g/12.57lbs.

 

[Chris_H]

I think lots of people have done HED in a 4" design.

I used a 48" Fruity Chutes compact Iris Elliptical, a deployment bag, a 15" FC pilot chute, 1/2" nylon webbing, nomex blanket, and it fits easily, with a little planning. The burrito with the harness is up top, and pulls the deployment bag out, so the pilot cute is out first. I made my own deployment bag sized to fit the chute and the nosecone. This was for a 12lb bird. For a bigger one, also 4", a Fruity Chutes 60" compact Iris Elliptical also fits in a deployment bag.

 

[PBic]

I think lots of people have done HED in a 4" design.

I used a 48" Fruity Chutes compact Iris Elliptical, a deployment bag, a 15" FC pilot chute, 1/2" nylon webbing, nomex blanket, and it fits easily, with a little planning. The burrito with the harness is up top, and pulls the deployment bag out, so the pilot cute is out first. I made my own deployment bag sized to fit the chute and the nosecone. This was for a 12lb bird. For a bigger one, also 4", a Fruity Chutes 60" compact Iris Elliptical also fits in a deployment bag.

Chris, would you happen to have a photo of your rigging you’d be willing to share? I’d like to sew up a bag and ground test it as soon as the wildfire smoke clears up here.

Thank you.

 

[Chris_H]

I looked, and the photos I have of the deployment gear are not that good.

I will get it out and set up a pic that shows how it all works.


Please allow a day or two for this.

 

[Chris_H]

A long day or two, or more.

This first photo shows the components, laid out as they fit in the nosecone. This is a 60" Fruity Chutes compact iris elliptical in a home made deployment bag. It fits fine in the nosecone, and can be shaken out easily. The burrito is a blanket with 9/16 nylon webbing, terminated in kevlar at both ends, stitched together with kevlar thread.

The anchor at the nosecone was modified from original by removing the minimally threaded 1/4-20 bolt into the aluminum tip, and making a larger diameter, better fitting G11 round anchor disc. The 1" kevlar strap was sewn around n M6 316 stainless eye nut with some M6 stainless threaded rod glued in with JB Weld after cleaning the bonded surfaces well with acetone. The forward cavity created by this was filled with epoxy loaded with tungsten powder, adding quite a bit more weight.
At the aft end of the kevlar strap is a stainless locking loop. A 4' long by 1" sewn kevlar strap connects the chute to the nosecone. Through the top of the chute connects the bag, and a 4' kevlar string for the pilot chute.
The main harness also terminates in the forward stainless loop. It is stuffed into the nosecone first, and in the second photo, the 3/8" kevlar strap loop that comes out of the nosecone is what comes out of the burrito. Inside, the nylon harness is z-folded and taped together, which gives a little resistance when the aft end of the harness is tugged, which in turn pulls the burrito out, and also the deployment bag. The pilot chute is the last thing stuffed in. I think I have folded it in under the flap on the bag.
In flights so far, I have used the blanket to give added protection to the bag and the chute.

Deployment charges have been the vinyl tube, high altitude sort, carefully laid alongside the bag, and sitting up alongside the main harness in the burrito, to boost the laundry out of the nosecone.
One failure that I had, was in assembling this, realizing that I had the screw holes misaligned for the nosecone to the AV bay. This twisted the deployment wires around the recovery system, causing a tangle and only allowing the chute to partially open. If the charges are in the tip, careful about twisting, and extra care about any potential tangles.

To simplify, I am going to do some testing with the charges in or against the AV bay lid. If the nosecone has any forward momentum, which it will, the 'short leash' of the folded and taped harness should pull the bag out without problems. I do not think that 'everything will be jammed up inside by the pressure'.

This is how my level 1 cert flight was rigged, and the level 2.

Another potential change are a lightweight blanket to protect the pilot chute.

 

[PBic]

Thank you very much Chris, I appreciate the explanation and photos. Looks like I'll be ground testing for a bit, right after I talk my sister into sewing a deployment bag and some blankets.

P.S. Really nice paint job from what I can see.

 

[ether]

what sized pilot chute are you using?

 

[Chris_H]

what sized pilot chute are you using?

Pretty sure that is a 15" chute, maybe a little smaller. I sewed it, and do not recall which one that is.

 

[OverTheTop]

I typically run a different system. I have a harness that runs directly between the avionics bay and the NC. A small drogue is attached to the NC. The NC is blown off at apogee, by electronics in the NC, and puts the rocket in a controlled descent. The main is in a deployment bag in the airframe, and its harness is attached to the avionics bay. The deployment bag is attached to the main harness. At main altitude (I normally use 1800') the DB is blown out of the airframe. There is a pilot chute on the main which is kept just under the flap of the deployment bag. Once the bag is out of the airframe the flap opens, air catches the pilot chute which pulls the main out of the bag.

 

[Chris_H]

I typically run a different system. I have a harness that runs directly between the avionics bay and the NC. A small drogue is attached to the NC. The NC is blown off at apogee, by electronics in the NC, and puts the rocket in a controlled descent. The main is in a deployment bag in the airframe, and its harness is attached to the avionics bay. The deployment bag is attached to the main harness. At main altitude (I normally use 1800') the DB is blown out of the airframe. There is a pilot chute on the main which is kept just under the flap of the deployment bag. Once the bag is out of the airframe the flap opens, air catches the pilot chute which pulls the main out of the bag.

Thanks for posting that. I was hoping to hear other people's methods, or critique of what I have been using thus far.

 

[Chris_H]

Over The Top, does that mean that from apogee, the drogue is keeping the nosecone up top, with the rest of the pieces hanging below, and when the main chute pops at 1800, that the nosecone has the potential to hit the main chute as the descent rate is slowed by the main?

With this setup you are describing, the AV bay slides fully inside the airframe, leaving the compartment up top for the main chute? Or you are using the more typical switchband on the AV bay?

I am not sure I fully understand your system.

 

[OverTheTop]

Switchband on the AV bay. The rocket airframe stays together. Depending on drogue size it could be more vertical sometimes, but I try to get it coming in relatively flat.

I have not had this method fail me yet. I used to use the same method, but without the DB, and it still worked well. Deployment bag helps heaps with packing and deployment. I like to use them for every flight now.

Don't undersize the drogue. I had one flight where the drogue was too small and the NC streamlined in behind the airframe as it descended. It was coming in quick but the main deployed and an nominal landing happened.