Mac
December 7th, 2007, 04:20 PM
This is not advice, this is a posting for historical reasons:
BASE Article #2 - Freefall Deployment Systems
From: ftr@sam.neosoft.com (Walt Appel)
Newsgroups: rec.skydiving
Subject: BASE Article #2 - Freefall BASE Deployment Systems
Date: Thu, 20 Apr 1995 18:53:53 UNDEFINED
This is the second in a series of articles that I am posting about BASE jumping. It gives an overview of freefall BASE deployment systems and their components. Future articles will include more discussion on equipment, techniques, and general info. I will also discuss sources for gear and information.
Feel free to e-mail me, but don't ask me to recommend specific sites. I will not recommend specific sites, nor do I recommend BASE jumping. BASE, even though it has evolved a great deal over the past few years, is still somewhat experimental and I consider it to be an extremely dangerous activity. I am posting these articles because the lessons that have been learned about BASE have cost us dearly. I do not want to see anyone hurt or killed because they were unknowingly re-inventing the sport.
In case, you're wondering about my background in BASE, I have made 55 BASE jumps, mostly freefalls from under 500 ft, from a variety of sites. I make and sell BASE accessories, e.g., pilot chutes, bridles, mesh sliders, etc., and I have been on the Bridge Day staff for the past few years.
Disclaimer: I am not now, nor will I ever be, the final word on BASE jumping. Nobody is the ultimate authority.
BASE is an extremely dangerous activity. In my opinion, the best way to reduce your chances of injury or death is to talk with as many expereienced BASE jumpers as you can, learn as much as possible, *think* about it, and jump in a way that makes sense to you. This article is written from one person's point of view (mine) and you'd be nuts to consider it the best or only point of view. There is a lot more to BASE than any series of articles can present. Use the information only as a starting point.
In contrast to a freefall skydiving deployment system, the performance requirements for a BASE deployment system can easily vary from one jump site to the next.
I cannot overemphasize the point that you need to evaluate the suitability of your deployment system for every single BASE jump you intend to make. The reason is that the amount of altitude that you can spend freefalling and deploying your canopy varies from site to site.
For any given BASE jump you need to use a deployment system that will give you an opening altitude sufficient to reach the landing area under existing conditions. BASE jumpers do this by selecting a combination of deployment system components that will meet their needs for the jump at hand.
A deployment system consists of the devices that control or affect parachute extraction and/or inflation. The devices commonly found in BASE freefall deployment systems are:
# A BASE pilot chute and bridle,
# A tailpocket (on ram-air parachutes),
# Deep or multiple brake settings (on ram-air parachutes),
# A low-drag (usually mesh) slider (on ram-air parachutes),
# The container closure.
What you don't see very often in freefall BASE deployment systems, with the exception of the very highest BASE jumps, are deployment bags. There is a variety of reasons for this, but of primary importance is the need for an on-heading opening. Free-packing seems to give consistently better results than deployment bags.
BASE Pilot Chutes and Bridles
BASE pilot chutes are designed to provide sufficient drag and snatch force to quickly open a container and fully extract the parachute at low airspeeds--much lower airspeeds than encountered in skydiving deployments. These pilot chutes may be made of either F-111 or zero-porosity fabric. F-111 BASE pilot chutes range in size from about 40 to 54 inches in diameter. Zero- porosity BASE pilot chutes range from about 36 to 48 inches in diameter. There are differences between BASE pilot chutes and skydiving pilot chutes other than the obvious size difference.
# Most BASE pilot chutes do not have handles; they are designed to be hand-held during launch and freefall--not stowed in a pouch.
# BASE pilot chutes generally use mesh with much larger holes than the mesh found in skydiving pilot chutes, and are typically built with much stronger reinforcement.
The choice of pilot chute to be used on a given BASE jump usually depends on the planned freefall duration. For delays of 2 seconds less, I usually use a 46" zero-porosity pilot chute, which produces roughly as much drag as a 52" F-111 pilot chute, but is less bulky. For delays of 2 to 4 seconds, I usually use a 42" zero porosity pilot chute, which is roughly the equivalent of a 45" or 46" F-111 pilot chute.
With the exception of the container closure, the bridle for a BASE pilot chute is the least-changed component of a freefall deployment system. BASE jumpers use a 9' bridle to help ensure that their pilot chute can easily clear their burble. These bridles are typically made of MIL-T-5038 Type IV nylon webbing, usually called "1 inch square weave". This is commonly used for skydiving bridles also.
I want to emphasize the importance of using an appropriate BASE pilot chute and a BASE bridle. I can think of two jumpers who died because they were using skydiving pilot chutes and bridles on BASE jumps. The pilot chute and bridle comprise what is probably the most important component of a freefall BASE deployment system.
Tailpockets
A tailpocket is a rectangular pouch sewn onto the center of a ram-air canopy's trailing edge. It is used to stow the suspension lines. Tailpockets, also used widely in CRW canopies, are usually made of parapack and closed with velcro, but I have seen some made of spandex. They may or may not have rubber bands for stowing the lines. The advantages of using a tailpocket instead of a deployment bag are quicker deployments and less possibility of line twist or an off-heading opening, because there is *no* possibility of "bag spin" or "bag lock".
Interestingly, I have seen a "nose pocket" used on a round reserve that was being BASE jumped. It worked well, but the typical line-stowage for round canopies is in the pack tray of the container.
Deep Brake Settings
Many hard-core BASE jumpers have deep brake settings or even multiple brake settings in their canopy's steering lines. They are a standard item on canopies designed specifically for BASE jumping. The reason is that deep brake settings reduce the forward speed during and after inflation. One worst-case scenario dreaded by all BASE jumpers is the 180 degree off-heading opening, i.e., the canopy opens facing directly toward the object. In this case the standard brake settings for skydiving canopies (roughly half brakes) may result in an object strike, which can be lethal. I have seen deep brake settings save a friend from an object strike. After a 1-2 second delay from a 350' cliff, his canopy opened toward the cliff face. Because of his deep brake settings, he had time to steer away from the wall. With skydiving brake settings he almost certainly would have hit the wall and gotten hurt or killed. I have had a 180 degree off-heading opening after jumping off a 215' cliff. I didn't have deep brake settings, but fortunately the wall was overhung enough that I was able to steer away from it. Deep brake setting are very smart for jumping off walls, but aren't really necessary for bridges, or antennas when jumping in good wind conditions.
Sliders (Ram-air Canopies)
Most short-delay freefall BASE jumps, i.e., jumps having delays of less than two seconds, are done with the slider left down at the connector links ("slider down"), or with the slider removed entirely. Normally, when a slider is left down, it is secured to the *front* connector links by passing nylon cord or webbing through each front slider grommet and the corresponding connector link, and tying the loop securely. The rear slider grommets and connector links are not secured. Tying the slider down prevents it from being pushed up the line groups during inflation. The reason for securing the front slider grommets and links only is that securing the rear slider grommets and connector links would restrict riser travel when steering with rear risers.
My personal preference is to remove the slider entirely for short delays. This doesn't seem to offer any real advantage except for a slightly neater pack job, but leaving the slider on doesn't serve any function, so I remove it.
For delays of 3 seconds or more, jumping "slider up" with a mesh slider is very common. A mesh slider is like a skydiving slider, also called a sail slider, except that it uses a nylon mesh material in place of F-111 or zero-porosity ripstop nylon. A mesh slider allows much faster inflation of a ram-air canopy than a sail slider, but still slows the opening to a tolerable speed.
When BASE jumping with a high-aspect ratio (roughly 2.5-to-1 or higher) canopy, mesh slider up seems to give the most reliable deployment. Some high-aspect ratio canopies seem to have a tendency toward lineover malfunctions when packed slider down. In general, high-aspect ratio canopies are not well-suited for most BASE jumps-- especially low jumps because they do not open as consistently on heading as the lower aspect ratio canopies.
Container Closure
Skydiving main containers on systems using a hand-deploy pilot chute are normally closed with a curved a stainless steel pin attached to the bridle. In recent years, velcro-closed containers have become very popular among BASE jumpers. The velcro closure, which will be discussed in detail in a future article, gives consistently reliable performance and needs no special attention.
Pin closures, on the other hand, warrant careful inspection before use on a BASE jump. The reason is that the amount of force required to pull the pin through the closing loop varies significantly--not only from container to container, but it varies a great deal depending on whether you are wearing the rig or not. Try this exercise: adjust your main closing loop so that the closing pin slides easily through the loop, requiring light-to- moderate tension, when the rig is on the floor. Now put the rig on and tighten the chest and leg straps. You will find the amount of force required to slide the pin has increased a great deal. Before BASE jumping with a pin-closed container, but sure that only light-to-moderate tension is required to slide the pin through the closing loop *when you are wearing the rig with the straps tightened normally*.
Examples
Most of my jumps are 1 second delays from under 500 feet. I normally use a 46-inch diameter zero porosity pilot chute and a nine-foot bridle. My usual canopy, a fairly new Super Raven 4, has a tailpocket with velcro closure and no stow bands. I have never jumped with a slider on the canopy and pack it in a velcro-closed BASE rig. I get quick, on-heading openings. The Super Raven 4 has an aspect ratio of about 2.25-to-1. 2.0-to-1 would be better, but the canopy does perform quite well.
On one BASE jump with a planned 10 second delay, I used an old Raven 4, mesh slider up, a skydiving deployment bag, and a large skydiving pilot chute (not collapsible!) and bridle. The harness/container system was a Jump Shack SST Racer. My reasons for selecting this seemingly odd deployment system was as follows. The landing area at the jump site was rough, so I did not want to risk damaging my Super Raven 4. The older Raven 4 was in good condition, but the fabric was fairly porous because of the number of jumps on it. To ensure a reasonably fast opening, I installed a mesh slider. Concerned that the mesh slider might give an unacceptably hard opening after a 10 second delay, I decided to use a skydiving deployment bag instead of the tailpocket that is on the canopy. This slowed down the opening to a comfortable speed. Unfortunately, the deployment bag also led to an off-heading opening but I was able to correct it easily.
The New River Gorge Bridge is 876 feet high. For Bridge Day jumps I typically use a 42 inch diameter zero porosity pilot chute, a 9 foot bridle, a mesh-slider up Raven 4, and a Jump Shack SST Racer. Not being eager to be considered a "real man", I usually take a 2 to 3 second delay and get a reasonably fast, reliable opening.
As you can see from these examples, you need to choose a deployment system that will deliver the performance you need for each jump.
BASE Article #2 - Freefall Deployment Systems
From: ftr@sam.neosoft.com (Walt Appel)
Newsgroups: rec.skydiving
Subject: BASE Article #2 - Freefall BASE Deployment Systems
Date: Thu, 20 Apr 1995 18:53:53 UNDEFINED
This is the second in a series of articles that I am posting about BASE jumping. It gives an overview of freefall BASE deployment systems and their components. Future articles will include more discussion on equipment, techniques, and general info. I will also discuss sources for gear and information.
Feel free to e-mail me, but don't ask me to recommend specific sites. I will not recommend specific sites, nor do I recommend BASE jumping. BASE, even though it has evolved a great deal over the past few years, is still somewhat experimental and I consider it to be an extremely dangerous activity. I am posting these articles because the lessons that have been learned about BASE have cost us dearly. I do not want to see anyone hurt or killed because they were unknowingly re-inventing the sport.
In case, you're wondering about my background in BASE, I have made 55 BASE jumps, mostly freefalls from under 500 ft, from a variety of sites. I make and sell BASE accessories, e.g., pilot chutes, bridles, mesh sliders, etc., and I have been on the Bridge Day staff for the past few years.
Disclaimer: I am not now, nor will I ever be, the final word on BASE jumping. Nobody is the ultimate authority.
BASE is an extremely dangerous activity. In my opinion, the best way to reduce your chances of injury or death is to talk with as many expereienced BASE jumpers as you can, learn as much as possible, *think* about it, and jump in a way that makes sense to you. This article is written from one person's point of view (mine) and you'd be nuts to consider it the best or only point of view. There is a lot more to BASE than any series of articles can present. Use the information only as a starting point.
In contrast to a freefall skydiving deployment system, the performance requirements for a BASE deployment system can easily vary from one jump site to the next.
I cannot overemphasize the point that you need to evaluate the suitability of your deployment system for every single BASE jump you intend to make. The reason is that the amount of altitude that you can spend freefalling and deploying your canopy varies from site to site.
For any given BASE jump you need to use a deployment system that will give you an opening altitude sufficient to reach the landing area under existing conditions. BASE jumpers do this by selecting a combination of deployment system components that will meet their needs for the jump at hand.
A deployment system consists of the devices that control or affect parachute extraction and/or inflation. The devices commonly found in BASE freefall deployment systems are:
# A BASE pilot chute and bridle,
# A tailpocket (on ram-air parachutes),
# Deep or multiple brake settings (on ram-air parachutes),
# A low-drag (usually mesh) slider (on ram-air parachutes),
# The container closure.
What you don't see very often in freefall BASE deployment systems, with the exception of the very highest BASE jumps, are deployment bags. There is a variety of reasons for this, but of primary importance is the need for an on-heading opening. Free-packing seems to give consistently better results than deployment bags.
BASE Pilot Chutes and Bridles
BASE pilot chutes are designed to provide sufficient drag and snatch force to quickly open a container and fully extract the parachute at low airspeeds--much lower airspeeds than encountered in skydiving deployments. These pilot chutes may be made of either F-111 or zero-porosity fabric. F-111 BASE pilot chutes range in size from about 40 to 54 inches in diameter. Zero- porosity BASE pilot chutes range from about 36 to 48 inches in diameter. There are differences between BASE pilot chutes and skydiving pilot chutes other than the obvious size difference.
# Most BASE pilot chutes do not have handles; they are designed to be hand-held during launch and freefall--not stowed in a pouch.
# BASE pilot chutes generally use mesh with much larger holes than the mesh found in skydiving pilot chutes, and are typically built with much stronger reinforcement.
The choice of pilot chute to be used on a given BASE jump usually depends on the planned freefall duration. For delays of 2 seconds less, I usually use a 46" zero-porosity pilot chute, which produces roughly as much drag as a 52" F-111 pilot chute, but is less bulky. For delays of 2 to 4 seconds, I usually use a 42" zero porosity pilot chute, which is roughly the equivalent of a 45" or 46" F-111 pilot chute.
With the exception of the container closure, the bridle for a BASE pilot chute is the least-changed component of a freefall deployment system. BASE jumpers use a 9' bridle to help ensure that their pilot chute can easily clear their burble. These bridles are typically made of MIL-T-5038 Type IV nylon webbing, usually called "1 inch square weave". This is commonly used for skydiving bridles also.
I want to emphasize the importance of using an appropriate BASE pilot chute and a BASE bridle. I can think of two jumpers who died because they were using skydiving pilot chutes and bridles on BASE jumps. The pilot chute and bridle comprise what is probably the most important component of a freefall BASE deployment system.
Tailpockets
A tailpocket is a rectangular pouch sewn onto the center of a ram-air canopy's trailing edge. It is used to stow the suspension lines. Tailpockets, also used widely in CRW canopies, are usually made of parapack and closed with velcro, but I have seen some made of spandex. They may or may not have rubber bands for stowing the lines. The advantages of using a tailpocket instead of a deployment bag are quicker deployments and less possibility of line twist or an off-heading opening, because there is *no* possibility of "bag spin" or "bag lock".
Interestingly, I have seen a "nose pocket" used on a round reserve that was being BASE jumped. It worked well, but the typical line-stowage for round canopies is in the pack tray of the container.
Deep Brake Settings
Many hard-core BASE jumpers have deep brake settings or even multiple brake settings in their canopy's steering lines. They are a standard item on canopies designed specifically for BASE jumping. The reason is that deep brake settings reduce the forward speed during and after inflation. One worst-case scenario dreaded by all BASE jumpers is the 180 degree off-heading opening, i.e., the canopy opens facing directly toward the object. In this case the standard brake settings for skydiving canopies (roughly half brakes) may result in an object strike, which can be lethal. I have seen deep brake settings save a friend from an object strike. After a 1-2 second delay from a 350' cliff, his canopy opened toward the cliff face. Because of his deep brake settings, he had time to steer away from the wall. With skydiving brake settings he almost certainly would have hit the wall and gotten hurt or killed. I have had a 180 degree off-heading opening after jumping off a 215' cliff. I didn't have deep brake settings, but fortunately the wall was overhung enough that I was able to steer away from it. Deep brake setting are very smart for jumping off walls, but aren't really necessary for bridges, or antennas when jumping in good wind conditions.
Sliders (Ram-air Canopies)
Most short-delay freefall BASE jumps, i.e., jumps having delays of less than two seconds, are done with the slider left down at the connector links ("slider down"), or with the slider removed entirely. Normally, when a slider is left down, it is secured to the *front* connector links by passing nylon cord or webbing through each front slider grommet and the corresponding connector link, and tying the loop securely. The rear slider grommets and connector links are not secured. Tying the slider down prevents it from being pushed up the line groups during inflation. The reason for securing the front slider grommets and links only is that securing the rear slider grommets and connector links would restrict riser travel when steering with rear risers.
My personal preference is to remove the slider entirely for short delays. This doesn't seem to offer any real advantage except for a slightly neater pack job, but leaving the slider on doesn't serve any function, so I remove it.
For delays of 3 seconds or more, jumping "slider up" with a mesh slider is very common. A mesh slider is like a skydiving slider, also called a sail slider, except that it uses a nylon mesh material in place of F-111 or zero-porosity ripstop nylon. A mesh slider allows much faster inflation of a ram-air canopy than a sail slider, but still slows the opening to a tolerable speed.
When BASE jumping with a high-aspect ratio (roughly 2.5-to-1 or higher) canopy, mesh slider up seems to give the most reliable deployment. Some high-aspect ratio canopies seem to have a tendency toward lineover malfunctions when packed slider down. In general, high-aspect ratio canopies are not well-suited for most BASE jumps-- especially low jumps because they do not open as consistently on heading as the lower aspect ratio canopies.
Container Closure
Skydiving main containers on systems using a hand-deploy pilot chute are normally closed with a curved a stainless steel pin attached to the bridle. In recent years, velcro-closed containers have become very popular among BASE jumpers. The velcro closure, which will be discussed in detail in a future article, gives consistently reliable performance and needs no special attention.
Pin closures, on the other hand, warrant careful inspection before use on a BASE jump. The reason is that the amount of force required to pull the pin through the closing loop varies significantly--not only from container to container, but it varies a great deal depending on whether you are wearing the rig or not. Try this exercise: adjust your main closing loop so that the closing pin slides easily through the loop, requiring light-to- moderate tension, when the rig is on the floor. Now put the rig on and tighten the chest and leg straps. You will find the amount of force required to slide the pin has increased a great deal. Before BASE jumping with a pin-closed container, but sure that only light-to-moderate tension is required to slide the pin through the closing loop *when you are wearing the rig with the straps tightened normally*.
Examples
Most of my jumps are 1 second delays from under 500 feet. I normally use a 46-inch diameter zero porosity pilot chute and a nine-foot bridle. My usual canopy, a fairly new Super Raven 4, has a tailpocket with velcro closure and no stow bands. I have never jumped with a slider on the canopy and pack it in a velcro-closed BASE rig. I get quick, on-heading openings. The Super Raven 4 has an aspect ratio of about 2.25-to-1. 2.0-to-1 would be better, but the canopy does perform quite well.
On one BASE jump with a planned 10 second delay, I used an old Raven 4, mesh slider up, a skydiving deployment bag, and a large skydiving pilot chute (not collapsible!) and bridle. The harness/container system was a Jump Shack SST Racer. My reasons for selecting this seemingly odd deployment system was as follows. The landing area at the jump site was rough, so I did not want to risk damaging my Super Raven 4. The older Raven 4 was in good condition, but the fabric was fairly porous because of the number of jumps on it. To ensure a reasonably fast opening, I installed a mesh slider. Concerned that the mesh slider might give an unacceptably hard opening after a 10 second delay, I decided to use a skydiving deployment bag instead of the tailpocket that is on the canopy. This slowed down the opening to a comfortable speed. Unfortunately, the deployment bag also led to an off-heading opening but I was able to correct it easily.
The New River Gorge Bridge is 876 feet high. For Bridge Day jumps I typically use a 42 inch diameter zero porosity pilot chute, a 9 foot bridle, a mesh-slider up Raven 4, and a Jump Shack SST Racer. Not being eager to be considered a "real man", I usually take a 2 to 3 second delay and get a reasonably fast, reliable opening.
As you can see from these examples, you need to choose a deployment system that will deliver the performance you need for each jump.