Chute Reef Line Cutter

Out of curiosity, has anyone tried a staged chute deployment using a reefing line/cutter apparatus? It's probably been done, but I wonder how much trouble it is to implement.

Greg

Tony Alcocer has done one. He comes through here periodically and should be able to tell you how he did his.

-Kevin

Greg, I've been playing with it on my min dia rockets. I've flown it five times now and learn something new on each flight.



I've been using a 357 bullet case that has an aluminum piston in it. There is a hole drilled through both the case and the piston. A nylon tie strap is fed through this hole. Then around the part of the chute to be reefed. It use 0.2 grams of 4F to operate.



Some issues that have come up..Using old brittle nylon tie straps = Use fresh tie straps. Lines twisting and breaking = pack lines and chute in deployment bags.



Don't glue depolyment bag closed = Don't use CA glue near chutes or deployment bags.

This photo is after the flight of mach 2.25 to 33K..came in a little bit fast.



here's a video of some early tests in my shop
https://www.youtube.com/watch?v=ggtsORqpFEY

Tony

tfish said:

Greg, I've been playing with it on my min dia rockets. I've flown it five times now and learn something new on each flight....

Tony

Click to expand...

Wow! Great stuff Tony!

I liked the test shot. It gives me a pretty good understanding of how it works.

I was thinking through the "how to make it work" phase and it was a pretty tough one to mull over. I did like your cutter solution and chute arrangement.

Do you configure for apogee/reef release, the main/reef cut deployment where a single chute is working as both drogue and main?

Have you had a successful flight, where everything worked as designed?

Greg

Greg, I deploy everything at apogee and then at around 2500' I un-reef it. It's worked twice out of three times now that I think about it. I've been running the shock cord up through the spill hole in the main to help avoid tangles. I does save space (length) on min dia rockets. I'm going to keep playing around with it.


Here's a video of one of the early reefed chute flights

[YOUTUBE]HwbsMH8cPRc[/YOUTUBE]

Tony

tfish said:

Greg, I've been playing with it on my min dia rockets. I've flown it five times now and learn something new on each flight.

Click to expand...

I've been thinking of doing something similar to retrofit dual deployment on my PML Ariel. One thing I'm concerned about is having the leads from the altimeter to the deployment device flopping around in the breeze as the rocket descends
from apogee. I can just imagine them disconnecting or breaking and having the main deployment fail. Is this a potential problem and if so what do people do about it?

Jonathan
-----
Jonathan Sivier
jsivier AT illinois DOT edu
NAR #56437 | Tripoli #1906
Home Page: https://netfiles.uiuc.edu/jsivier/www/

JonSivier said:

I've been thinking of doing something similar to retrofit dual deployment on my PML Ariel. One thing I'm concerned about is having the leads from the altimeter to the deployment device flopping around in the breeze as the rocket descends
from apogee. I can just imagine them disconnecting or breaking and having the main deployment fail. Is this a potential problem and if so what do people do about it?

Jonathan
-----
Jonathan Sivier
jsivier AT illinois DOT edu
NAR #56437 | Tripoli #1906
Home Page: https://netfiles.uiuc.edu/jsivier/www/

Click to expand...

I have the same concern, too. There's a lot of things being stressed when the laundry is out. I am not sure what is the best way to mitigate the risk. What do you think, Tony?

You could test a solution by using a leaf blower on the drogue configuration, and then, after a minute or so, activate the cutter or check continuity. Still thinking this through.

Greg

Jonathan, Yes there is a concern with the wires on the ematch breaking. I feel this would mostly happen from twisting. I had that happen once. That's when I went to the deployment bag. If you look closely at the 3rd photo down you can see my quick link that attaches to my bulk head. This seems to have stopped the twisting issue. I don't feel that there is a problem with it "flopping around in the breeze" now. You could always sub out the solid wire to strand wire on the ematch. Below is a photo of how things end up if your main does not deploy right.



Looks worse then it was.

I'm not sure a leaf blower could even come close to the stuff that goes on to these rockets on their way down.

Tony

JonSivier said:

I've been thinking of doing something similar to retrofit dual deployment on my PML Ariel. One thing I'm concerned about is having the leads from the altimeter to the deployment device flopping around in the breeze as the rocket descends
from apogee. I can just imagine them disconnecting or breaking and having the main deployment fail. Is this a potential problem and if so what do people do about it?

Click to expand...

Yes, flopping in the breeze can sever the ematch wires, especially if using a terminal block. I now wire the ematch directly to the altimeter with a stopper knot to prevent pull-out. I also try to keep the ematch wires long, so that they see no tension and thus the other recovery harnesses carry the load. I saw somewhere where the leads were zip tied to the shock cord, which may help.

In addition to the problems above, I also experienced lines that failed to cut and parachutes that failed to unfurl after being cut. Too many failure modes for me. I am going back to traditional DD with two-part airfraime separation.

GregGleason said:

Out of curiosity, has anyone tried a staged chute deployment using a reefing line/cutter apparatus? It's probably been done, but I wonder how much trouble it is to implement.

Greg

Click to expand...

I actually recently wrote and article for Apogee showing how I design mine. They are pretty similar to Tony's.


Braden

JonSivier said:

I've been thinking of doing something similar to retrofit dual deployment on my PML Ariel. One thing I'm concerned about is having the leads from the altimeter to the deployment device flopping around in the breeze as the rocket descends
from apogee. I can just imagine them disconnecting or breaking and having the main deployment fail. Is this a potential problem and if so what do people do about it?

Click to expand...

Jonathan,

I've used this method 8 or 10 times using a Defy Gravity tether. I quickly went away from a buritto method of holding the chute closed as I found twisting of the chute to be a problem. Most reliable method is to hold a deployment bag shut with the main inside and with the bag being held upright and fairly stable on descent by a small pilot chute. I have never had a problem with ematch wires because the stiff cable on the Defy Gravity doesn't allow it to twist at that point. Also you must keep the wires longer with enough slack to accommodate the movement of the tether.

-Tim

Buckeye said:

I am going back to traditional DD with two-part airfraime separation.

Click to expand...

The application is really for airframes that don't have enough space for traditional DD (stubby designs) or lengthening is not an option (scale rockets).

Here is my article. It's almost exactly like Tony's, but I like to use a dowel instead of what I originally tried, an aluminum peg of sorts. If lost, the wood is cheaper to replace. I also haven't found a dowel that fits right in the case, so I use colored pencils wrapped in tape. They actually last quite a while, and when they are fried, just cut another piece of pencil, wrap it in tape and drill a new hole through it.

Tony's design was my inspiration. Throughout testing, I discovered I like .38 special cases better. and that I should use wood dowels (or pencils) because they are easier to replace. There were quite a few of the devices destroyed when I was trying to figure out how much BP to use as well.


Braden