Reefing Chutes

[kitchw8436]

I do dual deployment on most of my HPR rockets which means the main deploys at a fairly high velocity. I've had rocket damage during main deployment. I'm considering reefing my main to reduce loads on the rocket. Looking for guidance on selection of reefing rings or other ways reef the main for more gentle deployment.

 

[Conway Stevens]

I do dual deployment on most of my HPR rockets which means the main deploys at a fairly high velocity. I've had rocket damage during main deployment. I'm considering reefing my main to reduce loads on the rocket. Looking for guidance on selection of reefing rings or other ways reef the main for more gentle deployment.

Define high velocity deployment? What size of rocket? Weight? Drouge size? Chute size? Lengths of harnesses? Do you reef your harnesses? Are you doing traditional dual deployment? HED? Other? Where are you placing the chutes on your harnesses?

I deploy on a 6 inch drouge for alot of my rockets all the way to M powered. 25lb rockets I bring stuff down anywhere from 75 fps to 125 fps and deploy the main at 1000ft with zero damages or issues. Several things can affect what happens.

 

[OzHybrid]

Show us a typical diagram of how you are packing all your laundry including the shock cord.

For the main, my shock cords are z folded with masking tape holding together. The last few bundles get taped heavier so that if there is a big shock there is still something to absorb it as the more heavily taped bundle releases. Are you using just Kevlar with no taped bundles?

 

[sharkbait]

I do dual deployment on most of my HPR rockets which means the main deploys at a fairly high velocity. I've had rocket damage during main deployment. I'm considering reefing my main to reduce loads on the rocket. Looking for guidance on selection of reefing rings or other ways reef the main for more gentle deployment.

I’ve done Bungee cord shock relief on some fast descents, take a 3’ length of bungee cord, make 2 marks on your harness 6’ apart, sew the ends of the bungee cord in at the 6’ marks and whip wrap with some tape. The bungee cord will absorb the initial chute opening load

 

[OzHybrid]

I’ve done Bungee cord shock relief on some fast descents, take a 3’ length of bungee cord, make 2 marks on your harness 6’ apart, sew the ends of the bungee cord in at the 6’ marks and whip wrap with some tape. The bungee cord will absorb the initial chute opening load

Bungee works, but can flick the nosecone or AV Bay back at the body. Depending on what you connected it to.

 

[tfish]

I started playing around with reefed chutes in 2010. I found that most flights overs a few thousand feet ended up a tangled mess...that solely used a reefed chute out in the airstream..

I started putting the chute and some of the recovery gear in a deployment "sack" that was then held closed by the zip tie.

I've used this to 40k, 54mm -6" rockets and with 3 main chutes once.

Putting stuff in the deployment sack keeps it altogether and tangle free..during long and or fast decents.

Tony

 

[KenECoyote]

FWIW For the few times I've reefed (a chute) on LP & MP, I simply tied a knot further up on the chute lines.

However for a HP DD, I feel it's better to just change the chute to a smaller one if you feel it's too big.

 

[tsmith1315]

Because of a minimal inventory of parachute sizes, I used to reef chutes often. On-site judgement call, based on rocket weight, altitude, wind, etc. with either a knot or a few wraps of masking tape.

However, I think the OP is thinking of a system that will gradually open the chute to full-size to minimize shock loads. A low-friction ring around the lines near the chute temporarily reefs the chute and would be pushed down as the canopy inflated.

 

[Handeman]

I do dual deployment on most of my HPR rockets which means the main deploys at a fairly high velocity. I've had rocket damage during main deployment. I'm considering reefing my main to reduce loads on the rocket. Looking for guidance on selection of reefing rings or other ways reef the main for more gentle deployment.

Most mains are deployed at 75-100 ft/sec. This is not fast enough to damage most commercial chutes.

If you are flying drogueless, then it's possible and not uncommon for the rocket to return ballistic where the nose-cone/payload leads the fin can straight down. You could get significantly higher drop speeds this way. Also, the main will deploy straight down. If the chute opens quickly and you are using a long shock cord, the payload would be susceptible to zippers when it hits the end of the cord while still dropping ballistic. The BT of the fin can is much more susceptible to zippers and damage with a ballistic return as it will continue straight down as the chute and upper section slow way down after the main opens.

First suggestion, if you aren't already, is to use a properly sized drogue chute to control the drop from apogee to main deploy. This is usually the longest part of the whole flight. Without the a drogue chute, there is no control of how the rocket drops. A V shape when the main deploys ensures the main opens to the side of the rocket and won't get tangled. It also allows the rocket to swing under the main from the side, reducing the shock on the recovery and the chance of damage from things dropping straight down when hitting the end.

 

[T-Rex]

Giant Leap sells "sliders" that are supposed to slow the opening of 'chutes......
https://giantleaprocketry.com/collections/fins-1/products/slider-4

 

[ep29030]

Consider a deployment bag as well. They assure that lines are stretched before chute inflates which reduces the opening force.

 

[kitchw8436]

Thanks for the quick feedback all. I wasn't that clear in the original post. I'm looking for a way to more gradually slow the chute opening to reduce loads on the shock cord attachments and parts of the rocket. Haven't had an issue with damaging chutes, but have damaged an e-bay bulkhead at the eye ring attachment to the shock cord.

@tfish, I had thought of reefing the shrouds part way and using line cutter to fully deploy the chute after initial deployment. Nice to see someone has done this. However, I'm hoping from something simpler.

Here's my typical setup. I use chute protectors in a burrito wrap style and tie the chute proctor to the shock cord about a foot away from the chute. I've been using tubular nylon cord and usually coil it an tape the coils. However, my current build is 76mm diameter fiberglass with a mass of 4.6 kg w/motor. I'll be using kevlar cord, and plan to tape it in z-folds. I've been using a 12" drogue.

I was hoping someone had guidance/experience with using a smooth SS ring to reef the shroud lines during initial deployment and allow a slower chute opening--or some similar technique.