The A5 was the first portaledge to have a frame truly engineered so it was able to support climbers in many different loading situations in any storm--prior ledge frame designs were not robust and often failed in extreme situations.
The A5 Double Ledge was the first commercially available portaledge that could support two people. There were a few attempts at 2-person ledge designs prior to the A5, but none lasted.
The "Shark Fin" is a divider system created for the two-person ledge. It made a division between the two sides of the ledge, creating a comfortable sleeping platform for each person and a more distributed payload.
A5 Haulbags were the most innovative of the time, and all current haulbags "borrow" ideas from A5, including the "tuckaway" shoulder straps (an A5 first), the waterproof closure, the offset clip-in, and many other innovations.
Other features you see on all ledges today were A5 original innovations, such as the cam buckle suspension system--the first reliable adjustment system for all weather, bed tensioners, and the adjustable fly pole.
John Middendorf adapted a design originally coming from TeePees to make a fly which only had one sewn vertical seam. Prior ledge fly designs all had six seams, which increased the likelihood of leaks.
The A5 ledges were truly the world's first truly stormproof ledges -- the expedition fly was built with doors and vents, making a comfortable base for intense adventures. A5 Portaledges enabled a huge boom in big wall standards in the 1990's because for the first time, climbers were able to withstand Himalayan type storms.
When John Middendorf created the first truly stormproof Portaledge in the 1980's and 1990's, a huge boom in big wall standards arose as climbers could withstand severe storms on the world's most remote big walls for the first time. John sold his company in 1998 and since then, his 1990's design has become the standard for all the major Portaledge manufacturers today. John then pursued other interests, including five years as a Grand Canyon river kayak and raft guide, where he met his wife Jeni. In 2016, while climbing with his family at Arapiles, John was approached by a big wall climber who asked why no one still made the strong, stormproof, and lightweight ledges like A5 used to make, and the conception for D4 was born. In the past year, using FEA tools along with ideas that had simmering for 20 years, John has created a revolutionary design, with over five significant cutting-edge innovations, and sure to become the new paradigm in Portaledge technology, as the new design is lighter, stronger, easier to setup and deploy, and much more versatile than the current designs on the market.
The D4 frame has been redesigned using FEA computer tools, and uses multiple diameters of tubing to make for a stronger, lighter, and more rigid ledge. Full Size (82" x 46.5") yet no spreader bar is needed! These ledges are so strong, there is literally no flex even when set up in a tree with only one point of contact.
The four-point suspension allows for easier adjustment and a more stable platform--the new D4 system is a 4-point equalising suspension with each of the four fins distributing the load, creating more stability in typical off-center big wall loading situations. Weight is saved, fewer straps to tangle during set-up, and adjustments are easy for every big wall and tree bivy situation. UPDATE: we have switched back to a 6-point design--please read the Kickstarter updates for more on the ongoing evolution of the D4 design.
John Middendorf, the inventor of the D4 portaledge, pioneered the world's first Stormproof portaledges back in the 80's and 90's with his A5 Adventures company. One of the solutions he came up with to make a rigid ledge back then was the "Block Corner" design, which is seen on virtually every portaledge manufactured by other companies today. The new curved corners is a superior solution, offering more strength, lighter weight, and most importantly, increased rigidity of the overall frame.
The D4 portaledge is the most compact folding ledge design, and even the haul sack has been re-invented to make packing up, and most importantly, deploying the portaledge tons easier, even in high wind situations. The zippered haulsack enables packing up to be simple and easy, while also ensuring an organised deployment. This unique design also allows for the portaledge to be optionally integrated with the fly (which fits in a separate pocket) as the system is packed up, for full stormproof deployments in minutes. Poised in readiness!
We are continually refining and improving our design, and personally testing each iteration. Currently we are building a series of prototypes that are going out with some of the world's best climbers, including Marek Reganowicz (who spent 25 nights in the first D4 Prototype on extreme walls in the Canadin Arctic), Mike Libecki (for a Greenland trip), Twid Turner (for an Alaskan wall), and even the El Cap master, PPTP, who is known for his abuse of ledges (he hauls them fully assembled up the walls). We are also supplying TheTreeProjects with the D4 Portaledge for their tree camping adventures, so will be covering the whole range of vertical camping experiences in our development and product testing.
For more information about the design, including technical information on how the frame is designed, please visit the Supertopo thread, Good Bye Spreader Bars (and plug for the new D4 Portaledge) here: Supertopo D4 Portaledge Design Thread .