I mentioned a while ago that I had flattened the sleeve cap of my Lisette Traveler dress. I did this for version 1 and version 2.
It's fairly simple to do, but before I show you what I did, should we talk about why in the world I wanted to mess around with sleeve caps?
When I pulled out the sleeve and saw the shape of the sleeve cap I knew what was going to happen:
1. When I lifted my arms, a folded ridge would occur at the shoulder. This is how a formally-fitting sleeve behaves.
2. My arm movement would be restricted. When I moved my arm, I would feel pulling on both the sleeve and the bodice.
The comfort level matters a lot more to me than the ridge at the shoulder line. And it's worth noting that in a looser fitting dress like this, the movement restriction will be much less than it would be in a tailored jacket.
There's a number 3, as would be discovered later on in the process:
3. I would have to ease in 2".
No shoulder ridge.
(I notice both photos do have the same pull line from the top button to the shoulder. I don't think that's worth looking at beyond determining whether the bodice is actually too narrow at that point or if a shoulder adjustment is needed.)
Some clarification: In my opinion, we don't have to look at the "shoulder ridge" as a sign of poor fit. Rather, it's a side effect of sleeve cap style. Each style has its trade-off.
There is a continuum from shapeless sack and totally free movement (see green sleeve) to closely conformed to the arm and restricted movement (see orange sleeve).
The green sleeve is super comfortable but, since it is not shaped at all to the shoulder, you will have extra folds of fabric in the sleeve when your arm is hanging straight down. Think of a simple tunic you might make from instructions in a kids' craft book, in which the pieces are basically squares.
The orange sleeve follows the contours of the shoulder nicely and fits the upper arm closely, but when you move, that closely fitting sleeve will pull at the bodice.
The neat thing is that you can have whatever sleeve cap shape you like and it will fit into your armscye as long as they are the same length. OR your sleeve cap length can be longer than your armhole length and you can ease in the difference (everybody's favorite thing.)
Note: It's not always a good idea to remove the ease in your sleevecap. If your sleeve is slim-fitting or if the shoulder seam is set inside the shoulder line, you might find you have no room for your shoulder joint. In that case, ease is totally justified. Plus, it sometimes just plain looks nice.
Another note: Being able to change your sleeve cap shape gives you lots of flexibility (no pun intended), but it's not a panacea. Check the size of your armscye. If it's too small, it will bind. If you have tightness or restriction, consider whether you need to adjust for square shoulders (raise shoulder seam and underarm seam). If your garment rises when you raise your arm, consider raising the underarm seam. (Oddly, experience tells me that a too-low underarm seam will also cause tightness across the top of the shoulder blade when moving the arms forward.)
In this case my objectives were:
1. Remove any ease in the sleeve cap.
2. Flatten the sleeve cap.
Here's what I did:
Step 1: Measure the length of the sleeve cap.
Step 2: Put the front and back bodice together at the shoulder to create the armscye.
***If your pattern has seam allowances included, remove that allowance at the shoulders, but not at the side seams (because the sleeve will also have seam allowances at the side seams).
Step 3: Measure the length of the armscye.
Step 4: Determine how much longer the sleeve cap is than the armscye. This is how much you will remove from the sleeve cap length.
In this case, the sleeve cap is 2" longer than the armscye, so I will remove 2" from the sleeve cap length.
Step 5: Use the measuring tape to create a new sleeve cap line.
I measaured out 17 1/4", because that is the length for my new, shorter sleeve cap.
Approximate the curves of the original sleeve cap, observing the different shapes of the back armscye and the front armscye. Flatten the top of the curve as much as desired.
Step 6: Sketch in the new line.
Step 7: Cut off the excess sleeve cap.
I redid my sleevecap alteration so I could take photos for you. On comparing this newest alteration to the one I used for my dresses, I can see I flattened the sleeve a little less this time around.