A5 Portaledge Design: the state-of-the-art portaledge design from 1987-2017, developed by John Middendorf 1987-1998.
NOTES ON THE A5 Design:
The A5 Design was the de-facto state-of-the-art portaledge design from 1987-2017, copied by the major manufacturers, and was the portaledge of choice on pretty much every cutting edge big wall ascent for all those years. It is worth reviewing portaledge design history, as often history repeats, sometimes with less-optimal examples. The A5 "block corner" portaledge I originally designed in 1987 was the first truly stormproof portaledge with strong frame and burly storm cover, and was key to a new standard of big wall alpine climbs.
To make your own A5 design, the hardest part is finding an affordable source of block corners, as the tolerances on the block corners need to be precise for the frame to function well. Info on the A5 design was originally shared on bigwalls.net BigWallForum in the early 2000's, and spawned a lot of online DIY tutorials, like this one for the fly and this one for the frame (but do not make open block corners!). I have also helped dozens of home builders and manufacturers to design and make their own portaledges.
The A5 "block corner" design is still a viable design if machined corners are easy to obtain, though it has disadvantages (i.e, less rigidity of frame compared to hybrid-diameter, curved corner frames).
The A5 Design has now been superseded by the D4 design.
ENGINEERING ANALYSIS : A5 vs D4 designs
The A5 Alpine Double design used 6061-T6 tubing, with a 1.125" Outside Diameter, and 0.058" wall thickness, and was engineered for a compact 40" x 75" two-person portaledge frame (the ledge Xaver and I used on Great Trango for 18 days and nights was this size). Metolius and the BD Cliff Cabana ("A5 block-corner designs") also use this size, but it is not the right outside diameter tube for these larger frames, so those companies had to add a "spreader bar" stiffener, a sign of patched design. Over the years, I have helped dozens of homebuilders (including small manufacturers like Runout Customs) make their own A5 design portaledge, but I no longer recommend the "block corner" frame design, as was introduced with the first A5 portaledge in 1987. The better design is to use strong, curved tube corners, using the appropriate radius thin-wall bending tool. This makes for a more rigid (less flexy) ledge frame, and is easier to build with the only specialised tool being a good thin-wall tube bender.
A5 revolutionised the tools for Big Wall climbing in the 80's and 90's: A5 PORTALEDGE PHOTOS ON EXTREME WALLS