How to get a really big chute out of a really big rocket??

[PSLimo]

Hi Dave,

No, the nosecone was blown out with the first event and the drogue chute. The chute cannon in that rocket is removable and held in by a quick link.

That beautiful looking V2 above is almost twice the diameter and exponentially the area of what we're both building and only used 28 grams of 4F for the event.

If you use the 7.5 Loc tubing for the main chute cannon, it will eat up a lot of the area in the main tube and won't require that much powder to blow the nosecone off for the first event if that's a concern, IMO.

Here's what I'm building which is a full 4' shorter than yours. I'll look forward to you flying first, LOL!



Phil

 

[David Schwantz]

Well I am now gonna throw mine out Mine is only 1/5th scale, gonna have to start allllllll over again
Great looking rocket. I would love to see as many pics as you would share. Thanks, Dave.

 

[David Schwantz]

That's really nice. I love the main tube. Did you make it?

 

[PSLimo]

Hi Dave,

I'm using this piston set up when flying single deploy. It's has 20' of cord behind it and 50' in front to the nosecone. One of the nice things about pistons is you don't have to worry about burning the chute or anything getting stuck.



Phil

 

[Bat-mite]

1/3 scale V2
The rocket ended up 14 feet long and 22 inches in diameter. It weighed 115 pounds including the 15 pound main parachute. The motors weighed in at 32 pounds, so the total liftoff weight was 147 pounds.

we used 1 ounce of BP for the main 28 foot chute (both for main and backup charge), it had a 6 foot pilot chute to pull the main out of the chute bag

View attachment 438475

So about 20 grams, which is consistent with what Tom C. does.

 

[Banzai88]

Please tell us detail of THIS! I'm about to do something almost the same with my PoleCat Thumper to put an Altus Easy Timer in it for Airstarts! Any more detail pictures?

 

[PSLimo]

I don't want to hijack anyone's thread but I'm glad to answer your question if it helps your build. The below pic's are from my 7.5" diameter 1/3 scale MGM-140 with the same style electronics bay. It's a cut out from the airframe with a piece of coupling tube inside it to screw the door into. I attach the electronics to the inside of the door which makes it easy to change out with the fins and centering rings seal the area inside. Should be an easy way to add to your Thumper for airstarts as long as the outboard motor tubes aren't in the way.

 

[Wayco]

I like your terminal blocks. Where did you get them?

Mouser Electronics:
https://www.mouser.com/ProductDetail/651-1984633

I run wires through the avbay lid, solder to the pins and hot glue the terminal block back down over the 3/32" holes. If the lid is metal, I drill a 1/2" hole in it and fill it with epoxy, then drill the holes.
The TB's slide apart in pairs, so you can make them bigger or smaller easily.

 

[OZRoc]

L3 Project. 1/2 scale Aerobee high. 7.5" dia x 14'. Pistons both ends using approx 50g CO2 ea. Aft drogue piston pushes forward from intermediate AV bay at motor end.

Half way there.
Cheers,
Mark

 

[iowadan]

Your best bet would probably be with a pilot chute. Use the link at the begining of the recovery section to open Parachute Recovery Systems Design Manual and go to page 6-43. There is an explantion of how to size your pilot chute based on the recovery conditions, type of pilot chute and size and weight of the main. It should make picking the pilot chute pretty strait forward.

 

[PSLimo]

Hi David,

I finished the chute cannon on my similar build to yours and tested it out, thought you'd be interested in the results. I used a 30" piece of 4" diameter green PVC sewer pipe because it's lighter than regular PVC and has a flared end. That allows for the breach to simply be a piece of the pipe screwed in. a 36" flame resistant cord is in the back behind the piston and in the front there was plenty of room for a 50' nylon shock is and a 12' rocketman chute. That's the 12' chute in the pic below for size reference.



It only took 2 grams of 4F to send everything sailing out the cannon and no worries about a burnt chute.

Did you come up with anything yet?

Phil

 

[David Schwantz]

I like your cannon.
I have a LOC 7.5" tube installed in NC, not only does it tie the shoulder and NC together, but it also serves as the outside of the cannon. The NC will slide into the tube and at the same time the LOC tube slides over a coupler with a stiffy inside. This is the inside of the cannon. She will have 2 main chutes, one each body and NC. The cannon will blow the NC off and the body main chute out together. The NC will pull the NC chute out as it goes. This chute is installed in the gap along the cannon and main body tube.

 

[PSLimo]

Hey David,

Just shows there's many ways to do dual deploy with a single bodytube and a nosecone.

 

[David Schwantz]

A question on yours. How is it secured into the rocket?

 

[PSLimo]

It's linked with the eyebolt in the left of the pic to the centering ring at the bottom of the airframe. I used Velcro to hold it to the airframe and keep it perpendicular. The cannon also extends a couple inches past the airframe to prevent possible zippering. It's an exact 11.4" version of the 7.5" build below which has flown several time without a hitch.

 

[OverTheTop]

I used a drogue chute at apogee and had an AARD release the main. That was on my 1/2 scale Nike Smoke L3 build. 8.25" airframe.
Detailed info here:
https://forum.ausrocketry.com/viewtopic.php?f=6&t=4612&start=75

 

[PSLimo]

That looks like another simple, reliable way to do dual deploy in a single tube, very nice Nike Smoke.

 

[PSLimo]

Hey Dave,

Thought I'd post some holiday cheer for a laugh as my main tube ejection charge test surprised me today. I use 3 grams of 4F in 7.5" diameter builds so I started with 5 grams for this 12" and just the shock cord to check the separation. Way to much powder as it sent the 7 lb nosecone 50+ feet, LOL!





I guess we don't need all that much more powder in the larger airframes.

 

[David Schwantz]

Go big or stay home
A guy out at MDRS runs 30 grams BP. He blows em straight up 75'.
Love the smoke rings you blew out of the tube.

 

[David Schwantz]

I just finished laminating the last of the V 2 fins today. Will start on the airfoil and get them glued on. I'll take pics of the ground test also. On your 12" dia one, how long is the compartment you are pressurizing?

 

[PSLimo]

Hi Dave,

That was my 12" diameter x 8' tall. 32" length of 12" diameter tube or roughly 3600 square inches to pressurize. In that test, the 4" x 30" chute cannon wasn't in the tube which is another 375 square inches and the drogue chute and cords is another 200 or so. If 5 grams of 4F did that in 32" and all loaded removes another 6" of tube volume. I'm thinking 3 grams of 4F is good.

The crude math to compare is about 1 gram of 4F per 8 to 10" in length of a 12" airframe???

I never got to 1 in the video.

View attachment New video3.mp4

 

[David Schwantz]

I like it!!!!!!!!!!!!!!!!!!

 

[OverTheTop]

On our full-scale V2 we had car airbags to push the man-sized chutes out.

 

[PSLimo]

Which matches your screen name perfectly. "Over The Top"

 

[jbrracer]

At what point are you guys deciding to go to anything other than the standard pressuring of complete body tube?
diameter?
Volume?
Length?

 

[PSLimo]

I'm all ears for other options, what were you thinking of?

 

[Dustin Lobner]

I thought I heard one time of someone using a motor on the bottom side of a piston? You get both the thrust and the pressure on the bottom of the piston. That was like 10-15 years ago I heard of that.

 

[David Schwantz]

Kind of don't think I want that flame inside my rocket

 

[Dustin Lobner]

Kind of don't think I want that flame inside my rocket

Lol, me neither. I post as "a thing I heard about", no guarantee of the soundness of the idea is written, expressed, or implied.

I kinda want to try it just I can say "I had to put a rocket in my rocket", but that's about it.

 

[PSLimo]

I'll second that Dave . Not to mention trying to stop the piston dead in its tracks with a shock cord while under thrust just seems like a bad idea, LOL.