Drafting a sleeve

I realized as I was working on documenting my HSF UFO project, that the write up is already getting long and I should probably break it out into parts.  I don't want to give away what I'm working on (other than it's 18th century!) so the drafting of the sleeve seems like a good part to piece out.  (Hehe, piece out...)

Anyway, to start on creating my own sleeve I always make a line dead in the center of the muslin.  From there, I measure out half my wrist measurement and my underarm measurement on either side of the line.  It ends up looking like the orange lines on this piece of muslin:

 The left is the "top" of the sleeve and the right, where the smaller line is, is the very bottom of the sleeve.  However, I need to do a "curvy" top for the sleeve - not a trapezoid- and I want the sleeve to only come below the elbow.  So, I do this:

 The two purple markings mark the measurement from my underarm to just below the elbow (10").  The top marking is made exactly 2" below the original orange line.  2" is roughly the difference between the measurement going from my underarm to just below my elbow (10") and the measurement going from where I'd like the top of the sleeve to hit on my shoulder going down to just below the inside of my elbow (~12"). 

 Using these new lines, I remark the top line out as a guiding line.   I also remark the bottom line, but at the just below the elbow measurement.  It's not in the above picture but you can see the purple line in the below photo.

 In green (I know, it's hard to see.  Sorry!), I've marked from the new top purple line to the new bottom purple line for the sides of the sleeve.  I've also drawn a rather bad bell curve across the top.   It's not that big a deal if it is bad, the point is to keep the line "low" about an inch or two in and then curve up to the original "top of the line" (orange in this case) at the dead center.   As long as one side looks okay, you just cut out the "good" side, fold the new pattern at the center line, and cut around the good side to get a symmetrical sleeve pattern like this:

 Now, this is a perfectly fine pattern in itself for any generic elbow length sleeve.   I use this style all the time for everything from Medieval right on up to modern sewing.  If you want it longer, just use the original wrist measurement and draw the side seam lines from the new purple line down to the edge of the old orange line.  That's it.  

But I don't want a generic elbow length sleeve.  I want a reasonable approximation of an 18th Century sleeve.  Most of the 18th Century sleeves that I was looking at have the top of the sleeve towards one side rather than in the middle as I do.  This means moving the underarm part of the sleeve to one side.  

 The (angry looking) pink line starts about halfway between the edge of the sleeve and the orange middle of the sleeve.   I'm following the green edge to create a simple new shape for the sleeve.  Once I've cut along the pink line, I move that piece over the other side, matching green lines together, like below:

 It's okay that it looks a bit angular here.  We'll fix that as we trace around this sleeve in aqua.  See?

 However, the sleeve still doesn't look quite right.  I need a deep underarm and, according the extant piece, the sleeve should have some sort of elbow flap.  So, in purple (ignore the yellow if you can see it) I kept the edges the same but made the underarm a but of a deeper curve.  I also added a small elbow flap.  The curve for the elbow flap is determined by where the center of the top of the sleeve is.  In this case, if you look at the top of the bell curve, you'll see a purple line.  This happened to be exactly 4 1/2" in from the edge of the sleeve.  I measured down from that line and made another purple mark.  This one is where I wanted the elbow flap to be at it's curviest.  

 Below is a comparison of the sleeve from Janet Arnold and the sleeve I drew.  The top of the sleeve in the book is much curvier but I don't like puffy sleeves on 18th C dresses/jackets/outfits so I kept mine much more shallow. 

Other than that, the pattern matches so now I have a reasonably period correct 18th century sleeve pattern to work with!  Feel free to ask questions.