...and here's how I did it:

In reading through the article, Bras in the 15^th Century?  A Preliminary Report, by Beatrix Nutz, I noted that the linen of the extant bra was of two different weights/thread counts.  The main part of the bra was made using a courser linen, the cups of a somewhat finer linen. I chose to recreate this third version using similar weights of linen to the extant one.

A breakthrough came after the second version had been made.  I wanted the cups to fit better and was having difficulty achieving the correct silhouette.  I decided to use a modern bra as a pattern, cutting out a cup and creating a two-piece cup pattern.  I labeled the pieces to avoid confusion.

Front.

                                                                            Back.

The cups are marked T for Top, C for Center seam, IE for Inner Edge, OE for Outer Edge, and B for bottom.  This made piecing the cups much much easier.
                                                       
 The cups were sewn together using a backstitch, and felled to itself as opposed to the fabric of the cup. 

The inside after stitching the cup to the outside.

Snipping through the panel...

The panel is trimmed.

Hemming the inside.

Ready to finish the center seam.

Center seam with rolled hem.

I also noted that the two cups of the extant bra touch at one point, and carefully sewed that area appropriately.  The original also had needlelace decorating the V-shape between the cups, so that is another addition to this version, using  waxed linen yarn. 

I had trouble with how to make the sprang more “solid” across the top of my second version.  I created a firmer edge with a buttonhole stitch, but that was not quite right.

Then I had a breakthrough.  I had been seen the below image before and never really processed it.  Then I looked more closely.  A flat fingerloop braid, with needlelace done along one edge, attached to the sprang.  This detail is visible on the lower right of the image:

This is a different supportive garment from the same find, but it seems appropriate to conclude that the same technique could have been used along the top edge of the “long-line” bra. 

The sprang for this bra was done in a simple pattern using linen yarn.  It is one-half of a sprang piece, cut in half and knotted to prevent unraveling.

Newest Lengberg Bra

I have finally finished another bra based on the "longline" bra found in Lengberg Castle in Austria.  This one includes the sprang insert, with flat fingerloop braids and needlelace.  My work is interpretive, since the original bra no longer has the sprang insert.

This bra is entirely handsewn using waxed linen thread. The body of the bra was made using a courser, thicker linen, with the cups being made using a somewhat finer linen, as the original was made.  

Here is a closeup of the insert as it is on me.  Needlelace decorates the edge of the cups and connects the flat fingerloop braids to the sprang. The flat fingerloop braids provide essential structure to the sprang edge. 

The bra shown flat.

The inside of the bra. Notice the gathered sprang at the point. This was my best solution to the shape between the cups. 

The back. The seam down the back was a fix done to allow the bra to fit more snugly. The laces are round fingerloop braids made with linen thread. The sprang, fingerloop braids, and needlelace are also linen thread.

I've made new sprang for the insert, and it looks much nicer:

The sprang lies nicely and is prettier too.  The pattern is from the blog squirrel!http://www.exhaliastudios.com/squirrel/this-sprang-has-sprung/