Welcome to Big Wall Gear's open source D4 Portaledge Design.
...how to create your own curved tube portaledge frames, as well as new innovations such as the patterns for the single seam zipped fly with corner pockets that make for the most secure and versatile storm system ever.
It is worth reviewing portaledge design history, as often history repeats, sometimes with bad examples. For the past 30 years, the A5 block corner portaledge design has been 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 (2007 published info here), and has been copied by a number of manufacturers and 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design if machined corners are easy to obtain, though it has disadvantages (i.e, rigidity of frame) which have been superseded by the D4 design.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 bigwalls.net, also spawned a lot of DIY tutorials, like this one. The bigwalls.net sharing of information helped spawn a number of talented portaledge makers, including notable companies like Runout Customs, who made further improvements. Barry Ward, who wrote the original "How-To-Make" a double portaledge for A5, now lives in Durango makes the D4 full size portaledge. Links above provide pretty much everything you'd need to know to make your own A5 portaledge design. Start here: History of Portaledge Design.
Principles of portaledge design (or any self-assembling folding frame)
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.
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 (make models with tent poles and a $20 hardware-store bender).
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, eliminating the need for drawcord and making a very secure windproof ledge/fly system.
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.
ALL MATERIAL PRESENTED AS CREATIVE COMMONS OPEN SOURCE WITH ATTRIBUTION.
ASPECTS OF THE D4 DESIGN (partial list):