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BASE Jumping: Articles: Gear: BASE Canopies

BASE Canopies updated

by BASEwiki

BASE canopies have come a long way since the first skydives were done under round parachutes, and it is beyond the scope of this article to provide a full history of the development of canopy flight. So let’s take off where skydiving left us…

The first BASE jumps were done with slow and docile skydiving canopies, often seven cells because of their opening and flight characteristics. A popular early BASE canopy was the Raven by Precision Aerodynamics. Occasionally one still sees BASE jumpers jumping a raven, but often only at forgiving sites involving water landings.

As the sport grew, BASE specific manufacturers started designing canopies solely for BASE. The focus was on accuracy performance, stability in turbulence, and heading characteristics. The canopies were reinforced to deal with hard slider-down openings, and came standard with a tailpocket. Since about 1998 all BASE canopies come standard with a tailgate, and often the lines designed to go into the tailgate are of a different color.

Vents and valves

Many modern BASE canopies are “vented” on the bottom skin. A vented canopy is generally recommended for a jumper who intends to jump slider-down or slider off on a regular basis.

Vents are small meshed-in openings on the bottom skin, usually near the nose, which serve two primary functions. First, they give faster top skin inflation. A ram-air parachute catches air and begins to fly in two stages: first, the bottom skin catches the air, snapping quickly open and decelerating the jumper; and second, the canopy inflates, the top skin takes shape, and the parachute begins to fly as a wing.

Vents reduce the time between the first and second stages, giving the jumper a flying canopy sooner — a characteristic which is particularly desirable in the event of an off-heading opening. Second, vents help keep the canopy inflated even when it is decending in or near a stall, for instance during a steep accuracy approach or when the canopy is nose-in during an object strike. In such scenarios, vents help maintain a reasonable decent rate and predictable flight, reducing the risk of injury.

Early vented canopies lacked any device to prevent air spilling out of the canopy through the same openings designed to allow it in. These canopies, though still in common use today, tended to have a lower glide ratio and poor flare as a result. Newer vented canopies include a valve of some sort which prevents air from spilling out through the vents.

One thing to keep in mind is that even valves are not leak-proof. Hence, there is a degradation in performance especially in the flare “department”. Also, there are some conventional canopies that pressurize better than some valved ones. The most important thing to keep in mind is not to get a false sense of security because you are jumping a valved/vented canopy.

There have been experiments with canopies that have a valved nose. In principle, this could also help keep the canopy inflated during an object strike. In practice, deflating such a canopy after landing can be difficult. Aside from the danger of being pulled around a tricky landing area by a still-inflated canopy, a quick getaway is sometimes desirable and could be complicated by a canopy that won’t deflate.

Zero-porosity “foreskin”

Most modern skydiving canopies are built from fabric which has been coated to give extremely low porosity and permeability — “zero-porosity” fabric. Zero-porosity fabric has largely failed to catch on in the BASE community for the same reasons that lead jumpers to curse it in the skydiving world. Canopies built from such fabric can be difficult to pack; they are slippery, and have a tendency to “breathe” when not controlled carefully. In skydiving, this is a nuisance. In BASE, meticulous packjobs are more important, and a canopy which is hard to pack can be dangerous.

Manufacturers have responded with hybrid canopies which are built primarily from the 0–3 cfm (cubic feet per minute) fabric which is more common in BASE canopies, but with the front half of the top skin constructed from zero-porosity fabric. The goal is to give these canopies many of the desirable flight characteristics of zero-porosity canopies without sacrificing ease of packing.

What to buy

It is impossible to tell what canopy to buy. As with most products in BASE, if there was a bad canopy out there, people in the BASE community would share this information quickly enough. That means that these days all available BASE canopies will do a great job. Canopies do vary in flight characteristics; the best canopy for you is probably the one that does what you expect it to do.

Look for a BASE canopy from a well known manufacturer. Get a wingloading between .65 and .75 making sure you keep your body weight plus clothing, helmet and armor in mind. It is highly recommended to get a vented canopy.

Some manufacturers allow you to jump a demo canopy at forgiving sites like the Potato Bridge. This can be a good way to find a canopy you like.

Comparing canopies

Many BASE jumpers have only put a few jumps on a small number of canopies, and continue to recommend that the one canopy they jump is the best one. Unfortunately, the number of people that have done sufficient jumps on enough different canopies to arrive at a reliable comparison is small.

If you do decide to compare some canopies, here are some things to consider.
  • What is the heading reputation of the canopy? Some canopies are more prone to heading problems than others.
  • How much forward speed do you have with a proper deep brake setting Some canopies require more forward speed than others to avoid stalling the canopy.
  • How well can you steer the canopy on risers, especially with both brakes still stowed? This is going to help you avoid an object strike some day, so you want good riser control, meaning you can turn the canopy around without consuming much horizontal and vertical distance.
  • How well can your canopy fly backward, both on risers and on toggles? Is it graceful, or more a chaotic stall with gravity taking over?
  • What is your glide range? Can you reach a far landing area by gliding at a shallow angle, and can you sink it straight in as well?
  • How well does it flare? You’re going to land your canopy in some rough landing areas, and the ability to tippy-toe your landings will save your femur one day.

Wing Loading

Wing loading (WL) is the ratio of the weight of the jumper plus gear measured in pounds and the square footage of the canopy measured in square feet. Unlike in the skydiving environment, where usually experienced skydivers jump canopies at higher WL than novices, in BASE usually the WL is more consistent across pilots, regardless of the experience level.

BASE canopies can be flown as low as 0.5 to as high as 1.0 WL. Going outside these limits is not recommended. However those are considered extreme limits not to be used on regular jumps. Flying a canopy at very low WL (<0.6) will result in poor inflation, sluggish control responses, and reduced flare power. Flying at high WL (>0.8) is also counterproductive because the canopy might be too twitchy in flight and hard to land due to the added airspeed and higher stall point, among other things.

Also at high WL the canopy might be subjected to additional stress from the openings. It is my opinion that the golden range for the WL of a modern BASE canopy is 0.65–0.75. Deciding which side of the range to choose is a matter of personal preferences. I personally like my BASE canopies at 0.70, other jumpers might prefer a bit lower while other a bit higher. A rule of thumb is to start at 0.70 and see if you need a bit more penetration and responsiveness.

Lately I have seen a trend of going bigger, i.e. lower wing loading. I have taken FJC freshly graduated jumpers on objects and their canopy size was in my opinion borderline unsafe. Bigger is NOT always better. If you do not have the skills to fly and land on a dime a BASE canopy at 0.70 then you should reconsider your participation into the sport altogether. There are many instances where a little performance is desired and too low of a WL will rob this performance away.

I rarely fly in full flight on a BASE jump but it is nice to know I have some extra speed and penetration when needed. If my WL was too low, this speed and penetration would be non-existent and I know for a fact I saved myself from some possible dire consequences a few times because I was able to out-fly obstacles in head winds or to turn quickly and this thanks to my WL.

In the end be very skeptical when someone recommends you anything lower than a 0.65 WL and again if this recommendation is in part due to your canopy skills, reconsider BASE jumping until those skills are adequate.

Submitted by BASEwiki on 2007-06-11 | Last Modified by sangiro on 2010-04-16

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