As far as my research indicates the screen used cloak was
not cut on the bias. The purpose of a bias cut for clothing is to allow fabrics that don't normally stretch along the grain to suddenly have the ability to stretch due to being cut at a 45 degree angle to the warp and weft threads. The other benefit is that they tend to drape better on the body, but that's really only necessary for more form fit clothing, not something as wide and as flowing as a cape or cloak. One of the reasons the costume designers often choose wool for cloaks and robes is the fact that it has such a beautiful natural drape that it wouldn't require a bias cut, where with a cotton fabric, for example, you
might opt for it in order to get a better drape.
The fabric used on the screen used cloaks had stretch and I know this because of the loose weave (as shown in the film with light passing through it very easily) and the fact that if you look at the costume in exhibition photos, the ones from MOM show the hem being at the ankles of the display. In later exhibitions the cloak is training behind the mannequin like a wedding dress, which it didn't do at all in the film. This is not due to a shorter mannequin being used. This is due to the fabric stretching out of shape because of the weight and loose weave. Gravity works against the material and the longer it's displayed vertically the more it will stretch out of shape. All of the cloaks I made from my accurate fabric had this same problem.
The other indicator of a bias cut is that over time the bottom hem of a garment will become wavy and not as bell shaped (in the instance of the hooded cloak) because as the fibers of the weave relax they will hang more unevenly and continue to stretch. In the film the hem is nice and curved, but looking at photos of it on display, had Mark worn it like that he would have tripped over the length due to the uneven hem- a result of the loose fabric weave. Also keep in mind that I saw the screen used costume in person with my own eyes in 2016 while on exhibit.
The other issue with bias cut is that it takes up much, much more fabric. Given that Mark Hamill and Colin Skeaping are about average height it's not like they needed to cut on the bias in order to get the width necessary if the bolt was too narrow. The cloaks were cut along the grain and the angle of where the two front halves meet the back are angled, but this isn't necessarily the same as a bias cut. Bias cuts wrap around the body tightly, draping close. As mentioned earlier this cloak also doesn't have a "spine" seam running up the center back the way Obi-Wan's robe and all the Prequel Era Jedi Robes do. There are two front panels, one back panel, and the hood has a front facing cut into the hem about 5 inches deep. This was also used for the Emperor's hood in ROTJ. All the hems are blind so they don't show. The inside of the cloak body seams are also French seams (like the Prequel Era Robes) to hide the raw edges of the material on the inside. Otherwise you'd see them serged and that's not the case. In the photo below (credit to Kay Dee's references) you can see the french seam/ flat felled seam.
View attachment 1696792
As far as how much material is necessary that will depend mostly on your height but for my personal cloaks I use about 8 yards or so. I'm 6 ft. 2". Keep in mind that the side seams of the front halves that attach to the one piece back don't fall exactly at the sides of the body like you'd see the side seams on a pair of pants. They sit farther back on the shoulders as indicated in this screencap from the movie. This means the shoulder portion of the back is cut a bit narrower and the front panels are cut a bit wider on the shoulder portion. I custom made my pattern from scratch. You could certainly use those existing patterns linked above by
PoopaPapaPalps and I think they would give you a good base to work off of but you're going to have to modify them.
View attachment 1696798
If it helps at all the following is a link to my shop with all of the Luke related fabrics I could source. I have been able to source them for every cloth outfit he wears in the OT: Farmboy (with Pancho), Dagobah Shirt, Bespin, Jedi, X-Wing Flight Suit with Jacket, Endor pancho, Medical Fatigues, Sandstorm, Yavin Ceremony, Hoth. All high quality, high fashion fabrics.
Our fabrics are sourced from all over the world to provide you with a nearly one stop shop to make perfect replicas of your favorite film costumes. We don't settle for mediocre fabrics, so why should you?
www.threadlair.com
The following images are of the cloak I made for Adam Savage and due to the width of the fabric I had to make it with the center seam up the back in order to get the drape wide enough. There was no way around it. At the time I made this I thought there were two versions of the hood. One with center seam (which is what I made for Adam) and the other without. It was later revealed (with better reference images) that there was one version which had a center seam.
View attachment 1696793View attachment 1696794View attachment 1696795View attachment 1696796
Here are some shots of the material up close:
View attachment 1696800View attachment 1696801View attachment 1696802View attachment 1696803View attachment 1696804
