Open Source D4 Ledge Design (more links within these links):

Welcome to Big Wall Gear's open source D4 Portaledge Design.

How to create your own curved tube portaledge frames, the lightest, most compact, and strongest ledge system, as well as stormproof  D4 innovations such as the single seam corner-pocket zipped fly that make for the most secure and versatile storm system ever. More information will be added as I organise my notes and notebooks--feel free to contact me for any particular John Middendorf D4 open source design you are interested in.

  NOTES ON THE A5 Design:   (2007 published info here), 

It is worth reviewing portaledge design history, as often history repeats, sometimes with less-optimal  examples. For 30 years, the A5 block corner portaledge I originally designed in 1987 became the standard.  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.  All the information to make the A5 Design have been available for decades and has helped dozens of home builders.  The A5 "block corner" design  is still a viable design if machined corners are easy to obtain, though it has disadvantages (i.e, rigidity of frame) which have been superseded by the D4 design.  The A5 single seam rainfly info, also published on,  also spawned a lot of DIY tutorials, like this one.  The A5 Design has been the de-facto state-of-the-art portaledge design from 1987-2017, used by the major manufacturers and a number of collaborators, and has been used on pretty much every cutting edge big wall ascent for the past 30 years.  A proven design with lots of bits and bobs on the details published here and there, for example: Full A5 Alpine Double patterns (which has been used to build stellar versions such as the Runout Customs ledges as well as many homemade ones.    Supertopo and various forums might have additional DIY info. 

A5 development documented here:   History of Portaledge Design.  

If you are interested in the simplest and strong design, I recommend this simple D4-inspired design of a simple curved corner ledge:

-->SIMPLE DIY PORTALEDGE --with 3 "How-To" videos

Optimal PORTALEDGE DESIGN is the D4 Design (supersedes the A5 Design)


ASPECTS OF THE D4 DESIGN (partial list):







Principles of  the D4 Design self-assembling portaledge design:

by John Middendorf A5/D4 Portaledge Designer

1. Frame needs to be rigid (I.e. no hinges or open corners--any play results in a wobbly platform).

2. For optimal strength-to-weight ratio, use multiple size tubes (outside diameter) in your design--the hybrid-diameter frame--use larger diameter in areas of greater stress to create the most rigid frame.  Understand strength and deflection formulas to determine tube sizing for a particular frame size and shape.

3. Consider deflection as a primary design criteria--based on your choice of material (modulus), strength will follow.  A rigid, non-flexing frame makes for the strongest, most stable platform.  All other A5 frame innovations also apply.

4. Curved tubular corners offer more frame rigidity than block corners, as well as offering lighter and more versatile designs and optimal shapes. As a design gets more rounded, the overall hoop strength increases.

5. The folding configuration is the other main design criteria.  Design for compact folding (all tubes same length), and for unfolding patterns.  A simple rectangular shape is simplest, but the delta shape is more stable.

6. The D4 overlapping-tube "Bullet Joiners" (patent applied for, now open source) have been proven excellent for ease-of-setup, strength/weight, and simplicity (continuous shock-corded frame) are the ideal joiner system for a collapsable folding frame.

7. The fly cover can be designed with with minimal seams, and with zipper openings and the D4 "corner-pocket" system (drawcord-free) and making the most windproof ledge/fly system, while being versatile by allowing full airing of ledge without sacrificing security when zipped.

8. Frame suspended ledges feel more solid than fabric (fin) suspended ledges.  The reason is the fabric shifts in its sleeve for fabric supported systems, and the frame flexes accordingly as the stresses shift.

9. Many A5 innovations also apply and many details brought forward with the D4 design.

If you are interested in the D4 design, I recommend you begin by making models with tent poles.  You can buy a plumbing tube bender from your local hardware store and with a bit of craft make scale models of any curved corner design.  D4's have been made in 4-piece, 6-piece, and 8-piece designs, but the basic principle is universal: the tubes will be continuously shock-corded together and all close to the same length.  Making a scale model will help you understand efficient folding patterns, another one of the many innovations of the D4 Design.