For a simple fur trade era mountainman work shirt, it's just a series of rectangles.
For the body, measure from your shoulder to your bum. Then take your chest measurement and add six inches. Cut a long rectangle with the width being half of your total chest measurement and the length being twice your shoulder to bum measurement. This makes the front and back of the body. Fold it in half across the width and mark the centre (this is where you'll be making the neck hole).
For the sleeves, measure round your arm at the top and add eight inches. Measure from your shoulder down to your knuckles with your arm down by your side.
Cut two pieces the length of your arm by the thickness plus the added bit. That will give you two sleeve lengths. Fold these in half lengthways and mark the fold at one end.
Line up the shoulder mark on the body and the shoulder mark on the sleeve. These should be right sides together. Sew the sleeves onto the body.
Then fold over the body and sew down the sides of the body to the bottom. Do this on both sides.
Measure your neck and cut a hole across the fold in the top of the tunic. Then slash down the middle for six inches or so. (This will ensure you can get your head through the hole.)
Try it on over your head for body fit. Gather the sleeves round your wrists (allow a bit slack so your hands will go through) and mark a line from the wrist to the armpit. Cut off the excess material and sew the sleeves from the armpit down to the cuff (do it inside out of course). Turn it the right way out and try it on. If it fits OK, make a simple collar so it goes round the slit you made in the body. Add a button to the neck so the slash closes and that's basically it.
Having said all that, linen would be more appropriate for a work shirt as woolen blanket is hot and heavy. The method is the same though.
When you are finished with the fit, overstitch all the raw edges to keep them from fraying.
Mountainmen would either make these themselves, or if they had a native wife, would get them to do it. The style is Indian and they would not have had the skills to do European tailored fitted sleeves. The fitted shirts would have been bought at the annual rondezvous but would have worn out during the season, so the above style would be period correct for a trapper/mountainman.
Eric
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