Deploy from nose cone or mid-airframe?

[gvasiloff]

I’m building my first L1 kit, a Loc 4” Patriot. I’m trying to keep it simple. No e-bay. I want to make it look like my first rocket from 33 years ago (Estes Patriot).

I just got the kit today, and I’m trying to figure out if there’s anything wrong with permanently joining the two airframe sections and having the shock cord attach to the nose cone (modified with a bulkhead and eyebolt, of course) for separation like a big Estes kit. The “general” loc instructions have it separating mid-airframe with a coupler and bulkhead in the middle of the rocket. The rocket tubes together are 40” long. Is that too long for 38mm motor deploy?

Are there any issues with going that route? I know other kits of similar size, like the Apogee Zephyr are setup that way. Nose cone just comes off the top like a low power kit. I would think having all the laundry up higher would help with stability as well by pushing the CG forward and reducing the amount of nose weight added. Is there anything that should be done to keep the parachute from sliding too far down the tube under heavy acceleration as well?

 

[teepot]

To answer your question. No it's not to long and yes you can put a shelf with holes in it or a baffle. Or you could attach a coupler with a bulk head at the break point. Attach the coupler with screws or rivets so it can be removed. That set up will allow you to swap an Av bay in place of the temporary coupler if you want to do DD. Of course it depends on the length of the motors you plan on flying the rocket on. A 4" dia 40"long BT minus a 14" long mmt minus a 4" NC shoulder isn't to much space for the ejection charge that comes with a DMS motor to pressurize. I have a rocket that is similar to yours. It's NC eject without a shelf or baffle. I have flown it on I175's and I280's without issue. If you don't plan on using an I280 or an I500 you will have more space for a DD set up. A lot of my rockets have removable couplers. Both for ease of repair or to make a DD rocket.

 

[Jmhepworth]

My concern would be the volume of the airframe that needs to pressurize to push the parachute out. You’re more than doubling it. Without testing, I would be concerned that the powder from the motor wouldn’t have enough oomph to get everything to come out. I would just have it separate as designed. Think of it as a really long nose cone. Put the chute 1/3 of the way down from the nose cone so the two parts don’t bang against each other on the way down.

 

[rcktnut]

My 4" PML Patriot has lots of flights with the mid airframe deploy on it. Never had a problem deploying that way with amount of BP supplied with the motor. Going with a nose cone deploy would most likely have to be adding more BP for deployment. I never added any nose weight to it. Nose cone is secured with 2 plastic rivets, weight could be added if ever needed.

 

[David Schwantz]

Your idea will work. Ground test all rockets before flight. But you could add a stuffer tube and bulkhead to reduce volume. This will also act as your "shelf".

 

[Steve Shannon]

Two concerns come to mind:
1. The volume that you must pressurize. That can be mitigated by incorporating a stuffer tube.
2. If you break at the nose cone but fail to get the chute out the rocket might still be stable, which increases the risk of damage to people or property. If you break it midway, even if the chute doesn’t come out the rocket will be unstable, which causes it to fall more slowly.

 

[Hobie1dog]

mid-frame

 

[NAR29996]

I have 40+ flights on my 4" (original) NCR Patriot. It ejects the nose cone, and, as I still fly it, this has worked fine for me. Of, course. I have repaired it a time or two.

 

[loopy]

Personally, I'd go mid-sep and make it dual deploy capable for the future for when you want to really send it. Also makes it easier to transport.

That being said, making it nose-blow would work, you just need to make sure you ground test it for ejection charge sizing.