Step 1: The History
Historically in Europe it would have been made from wool or if your were fabulously wealthy linen, cotton or even silk. This may apply in Asia, I do not know.
Many argue that the lozenge or diamond pattern quilting is not historically accurate, but I'm not so sure, I've seen a chess piece from the Isle of Lewis that clearly depict a diamond pattern and the pieces carved there demonstrate a high degree of accuracy. Additionally the Bayeux Tapestry show something that may be diamond pattern, the diamond pattern is logical since it holds the batting in place very well.
Regardless of historical influence, diamond pattern sewn padded material is readily available at most fabric stores and is acceptable to average observer as not dispelling the illusion of authenticity.
If you must be historically accurate this is not the project for you, I have no primary evidence but would be happy to hear from someone who does.
Step 2: Disclaimer and Advice
IF YOU ARE USING SOMEONE ELSES SEWING MACHINE MAKE SURE YOU ASK PERMISSION TO INCLUDE YOUR PARENTS IF APPLICABLE.
ON MY FIRST SEWING PROJECT I SEWED MY THUMB TO A PIECE OF LEATHER WITH MY MOTHERS UPOSTERY MACHINE, I SCREWED UP THE MACHINES TIMING AND HAD TO PICK THE STICHES OUT OF MY THUMB ALONG WITH A BROKEN NEEDLE. IT REALLY HURT A LOT AND TOOK ME FIFTEEN YEARS TO OVERCOME MY FEAR AND MEMORIES.
GET LESSONS, GET HELP DON'T GET HURT.
Step 3: The Patterns, Tools and Materials
Dimensions fit a anyone who wears a Large to X Large T-Shirt
Long sleeves are optional as is overall length and riders cut, the riders cut facilitates stepping up to the stirrup and swinging your leg over a saddle. Cutting the length to groin level will also do this.
For this Instructable we will be making a gambeson which will finish just below the knee of a 5'10 male with lots of room for movement for archery, foot combat or riding on horseback, anything else and your on your own as to whether or not it will work.
What you need is:
4 yards of 40-42 inch wide material (whatever colour you like)
2-3 packages of Bias tape (whatever colour)
1 spool of thread which matches your bias thread and optionally a spool that matches the color of the padded material. Get the heaviest strongest thread you can find, ask for stuff to make sports uniforms with.
1 pack denim needles, anything else will break at the worse possible time.
1 tough sewing machine that can sew through 4 layers of trigger and two layers of batting as well as bias tape.
1 pair very sharp strong scissors, you can get by with normal scissors but you may have to cut layers separately. I use shop shears, as a rule really good scissors and shears are expensive that's just the way things are and why your mother freaked out when you cut anything with her "good" scissors.
Step 4: Laying Out the Material and the First Cut.
Fold the clothe in half across the width then in half along the length.
NOTE - I don't use pins, I learned to sew large things first after I overcame my fear and when my need for a tent was great, so I learned to roll seams with my fingers. My wife uses pins. The difference is I am faster but not as accurate as she is. If you want to use pins that's fine but I don't. Fin.
Once you've made the two folds the edges should be on one side and the centers of the clothe should be on the other edge and the top, if it's not try again the object is to cut the left and right side as well as the front and back with one cut.
Try this on a piece of paper first if there is any question in your mind, if it comes out looking like the picture at the bottom of the pattern page when you unfold it, you got it right, if not try again. Since the material will cost you between $40 and $50 be sure of what you're doing.
When you are sure that you've got it, and I mean REALLY REALLY SURE then line out the pattern on the clothe as shown.
Check it again, and then cut. When you done it should look like the picture on the bottom of the previous page, if it doesn't don't panic you can probably save it by sewing it on the mistake line, either in the center or on the top.
Step 5: The Collar
Jersey material which T-Shirts are made of stretch, padded material usually doesn't. So we add a relief cut which gives the collar the "keyhole" shape that it is named for. Some collars were nothing more then a rolled slit or square shaped and might or might not have had relief cuts, I like the "Keyhole" appearance when trimmed so I'm doing that one here. I made add other collars if the demand is there.
So make the back cut first. You'll do this by cutting the back and the front at the same time, this isn't a problem since you'll make another cut to enlarge the front and then add the relief cut.
Step 6: The Sleeve Extension
t I like sleeves which come to mid forearm, they don't interfere with my sword arm, my armor or my gauntlets, but the fellow who wanted these also shoots archery as well as fighting and riding horses (Sheesh and they say I'm demanding) so anyway he wanted long sleeves so I measured him from wrist to wrist, subtracted the width of the cloth and divided the remainder by two, that gave me the length of the extensions I'd need to add. Some folks like a vest style with no sleeves, others like detachable sleeves but those are for the later period Jupon which I'll probably get to sometime next year at my current rate (no kidding I've got a bunch of stuff I want to record and preserve here)
When you figure out the extension length, use that as one dimension and the width of the sleeve from Step 4 as your two measurements.
If you want bias tape then this is the time to measure it also for the cuff
Then measure your bias tape for your hem and the collar, cut all to size
Step 7: Sewing
Optional but good idea, sew all edges to prevent unraveling and help in alignment, if your using pins, a surger or both this isn't going to be a problem for you. If your doing it my way by hand then sew the edges you'll be better for the extra work. Then . . .
First sew the bias tape to the cuff side of the extension
Second sew the bias tape to the hems
Third sew the bias tape to the collar (this is the pain in the butt step)
Fourth sew the bottom edge of the sleeve, follow it around to sew the sides until you reach the hem, repeat for other side.
Turn it outside out and TAH-DAH you've got a gambeson.
Oh wait, he wanted a "Rider" cut, OK go on to the next step.
Step 8: The Rider Cut and Finish
To make the "Rider" cut simply have the individual try on the gambeson and determine where their inseam is, drop down about four inches and draw the line for the cut to the bottom of the garment.
Cut it in front and back then add bias tape to finish.
and your done go hit something with a sword, or better yet a hammer, there's just something about hitting something with a hammer that is fundamentally good. . . . Maces are good too!