This Gambeson is designed for simple construction. It consists of two pieces and can be modified or altered to personal preference. I like to enter from the side with ties used to close on my right side. This basic pattern could also be designed with a typical jacket opening slit down the front. I just like to keep one piece of continuos padding underneath the breastplate so that it does not bind or pinch beneath the plate. I also uses heavy cloth ties so that I don't get any buckles or fasteners mashed into my body underneath a plate impact.
First you will need to determine your critical measurements:
Measure the distance from the top of your shoulder utilizing a cloth measuring tape to the length that you want. I like mine about mid thigh.
Measure your chest from the widest point to directly underneath each arm. This is how wide to make the Gambeson.
Next you will use paper to pattern the arm and neck openings for the front pattern.
With the basic length and width measurements cut a piece of butcher paper, newspaper, brown paper trash bag ect., Cut this piece of paper extra long and wide so that you can add the attachment tabs and closing flap.
Fashion the front opening large enough to fit your head through. This should describe an arc cut low enough so that when you tilt your head down you will not feel a choking sensation. Also, consider any Gorget that may be used underneath.
Next trace only one arm opening (you can fold your pattern in half lengthwise so that the dimensions will be exactly the same on both sides). You will want to take care to have a large enough opening so that your arms are not restricted when they are rotated through a complete range of motion. Try to put your elbows together in front of your chest. This mimicks the motion that you will do when delivering a sword blow and holding your shield in position in front of your body. Mark where you want the seam to start and end beneath the Gambeson arm opening. This is indicated by the cross hatched areas on the side of the Gambeson patterns. This will be where the two halves are sewn together. Again check for range of motion. Lean left and right. Observe where your body flexes, this is where to end the seam. You don't want your legs to be limited in movement by your Gambeson.
Repeat the same procedure for the back piece. The neck opening will be smaller in the back. The arm openings will be slightly smaller in the back to cover the back of the shoulder.
The cross hatched tabs are where you sew the two sides of the gambeson together. I put the back part under the front part and sew dirctly on top of the back piece making no attempt to fold back anything. Note the right side is not sewn. It gets tied after putting the gambeson on. Additional info about sewing: Get some heavy needles for mom's sewing machine, tell the folks at the cloth store that you will be sewing a heavy blanket. If you are using a moving blanket or some other prepared quilt. Immediately after cutting into it run a single stitch around the entire perimeter. This will prevent the thing from losing its quilt stitches.
Materials: You can use moving blanket if you can find one made of good material. It's just that the finished product looks like well Ymoving blanket! Highly recommend that you use heavy cotton duck material with Quilt batting for filler. The finished garment will look much nicer and you can pick exactly what color you want. You also get to choose the pattern of quilting. You can choose squares, diamonds, or waves. (I just saw some excellent examples of Celtic quilt patterns in the movie Elizabeth, Hmmmm) For the seam edges I like to use Quilt tape. Get the widest you can find At least 1". When sewing this stuff sew it one side at a time finishing with the front (the pretty side). Also run Quilt tape around the perimeter of both sides of both pieces. This locks in all the stuffing and looks very nice. I also use para cord for my ties on both sides, I'm in the military so its very cheap, indestructible, does not rot etc., For the purists you can look for natural fiber, or use leather, just good luck when you have to wash the thing!
If you want to make arms for this you are basically on your own. I use a long sleeve shirt and neoprene elbow pads. I find that I'm hot and encumbered enough under breastplate and gambeson so I radiate heat thru the pits and arms. Basically pattern this in the same way leaving an opening at the elbow and armpit. Be careful not to bind at the elbow or you will limit your range of motion. Critical measurements for this will be the length of the arm from the end of the gambesons shoulder to the wrist, diameter of your bicep at its thickest point, and the diameter of your forearm at its thickest point. Take your time with paper before you cut cloth and this should work well. It will lay out as a trapezoid with a hole in the center.