BASE Article #2 - Freefall BASE Deployment Systems

BASE Article #2 - Freefall BASE Deployment Systems

Post by Walt App » Fri, 21 Apr 1995 04:00:00


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.
==================================================================

Freefall BASE Deployment Systems
--------------------------------

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:

   o A BASE pilot chute and bridle,
   o A tailpocket (on ram-air parachutes),
   o Deep or multiple brake settings (on ram-air parachutes),
   o A low-drag (usually mesh) slider (on ram-air parachutes),
   o 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.

   o Most BASE pilot chutes do not have handles; they are designed
     to be hand-held during launch and freefall--not stowed in a
     pouch.

   o 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 *** 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
...

read more »

 
 
 

BASE Article #2 - Freefall BASE Deployment Systems

Post by Chris Jenki » Sat, 22 Apr 1995 04:00:00

Quote:
Walt Appel writes:
>>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.

I don't know whether I'll *ever* be ready to do a base jump, but it's great
to see someone bothering to post this information/opinion which I'm sure
will of invaluable help for anyone wishing to go for it!!

Found it great to read and informative anyway!

Thanks Walt!

---
Chris Jenkins           "For once you have tasted flight you will walk
                         with your eyes turned skywards, for there you
                         have been and there you long to return"
B 10511

Keep smiling

:-)

 
 
 

BASE Article #2 - Freefall BASE Deployment Systems

Post by John2wal » Sun, 23 Apr 1995 04:00:00

Great article Walt.
Appreciated your help at last Bridge Day.  We had no idea what to do and
you helped us survive.  Incidently, Walt might not post this but he sells
great Base Pilot chutes (even if they are a little brightly colored).
See Yah!
Johnny