Pressure on bulk head at ejection I can't do the math

[Scott Chase]

I simply Cant do the math involved here

1) Bulkhead is held in with epoxy and attached to a lock 2.14 coupler.
2) Shockcord is Estes 1/2 x 96 inch that is (13 mm 243.8 cm)
3) Rocket Length is 45"
4) DIM 2.14"
Weight without motor is 18.4 oz
5) rocketry works data
6 G80-T Motor

 

[Nytrunner]

I simply Cant do the math involved here

What is your question

 

[Banzai88]

I think that he's asking if, during the ejection of a G80-T motor, that his rocket will open up, deploy the parachute, and if the shock cord will keep all the pieces together. But you know what they say about assumptions......

The answer is a HIGHLY qualified "MAYBE". Depends on what the spec of the shock cord is, and how well the rocket is put together, along with the variable of how many giraffes wear vests because they have no sleeves or because ice cream has no bones when pancakes fill up a dog house.

To know how much pressure is in the section and bearing against all surfaces, you need to know the volume of said compartment and the volume of BP in the ejection charge.

I use one of these calculators

 

[Neutronium95]

This rocket has less volume to pressurize than a lot of kits that successfully fly on the G80. It will eject perfectly fine.

 

[Scott Chase]

This rocket has less volume to pressurize than a lot of kits that successfully fly on the G80. It will eject perfectly fine.

Neutron95
Thank you for your reply!
If it's ok I'd like to ask you a question that's troubling me?
I'm going to attach my parachute with a ball bearing swivel 175lb maximum weight.

One end of the swivel to the bulkhead with 225lb Kevlar and attach the other end of the swivel rated at 175lb to the parachute using the coast snap. I want to do this so I can move the chute to other rockets the same size as the one in this conversation. Any stronger snap is to large for my rocket. Will the 175lb snap be strong enough to hold the pressure of the 15" chute opening using G80 with 9 second delay? If this swivel works I would also use it with JL chute release at 400ft.
Thank you
Brian Johnson

 

[Zeus-cat]

You can Z-fold your shock cord to reduce the force on the shock cord system when it deploys. Take a couple of inches of shock cord and fold it onto itself and tape it with masking tape. Repeat until the length of the exposed shock cord is taped.

 

[manixFan]

If you are using Kevlar and opening at a high velocity there is a good chance you can zipper your body tube. When the chute opens at a high velocity the kevlar is pulled through the body tube leaving a big slice through it. I prevent that by using a cork threaded through the kevlar and positioned at the top of the tube. I just push a straightened paper clip through the cork, form a loop in the clip, thread the kevlar through it, and then pull it back through. I've never had a zipper in a rocket that uses this method.

Good luck,


Tony