How to Make a Sleeveless Dress or Top Using a Pattern that has Sleeves
Simplicity 2927 (now out-of-print) is a good example. I know because I have used it twice. The first go was my first dress made from scratch in 2007. I used the long sleeves and (after some considerable taking in) it fits okay. It looks terrible to me, but that's first sewing projects for you. : )
Last year I made it sleeveless. It looks better because my sewing has improved. I still had to take it in. When I tried the dress on I found that the shoulders on its yoke stuck up. Why? I thought it must be because I didn't use interfacing so the fabric must have stretched out of shape, but now I have Pattern-making for Fashion Design 5th Ed. by Helen Joseph-Armstrong, I have learned that it was because the shoulder's needed contouring. I.e. they needed the shoulder seam to have 1/8" (3mm) taken off at the shoulder end, tapering back to the original measurement at the shoulder tip.
The Side SeamsAs your dress pattern is drafted to have sleeves, it has ease at the side seams so that you can raise your arms. When you make a sleeveless version, you have to take it in at the side seams. The best way to do this is to try the dress on and pin fit it.
The ArmholesAlso, now that the dress is narrower, the armhole will be closer to you and will probably be a very uncomfortable shape if you intend to use your arms at all. The front of the armholes will need scooping out. With the dress on, lower your arms, reach forward, and you will see the creases at the front armhole (not to mention feel the dress being very uncomfortable). With dressmaker's chalk, draw a rough line of where the armhole should be to be comfortable. Then thread trace it. Now you can sew the armhole facing on along that line. The adjustment will probably be the same for the other armhole. When you have finished the armholes this way, they should be much more comfortable and much more practical!
I hope that helps!
Until next time, happy sewing!
The Sewing Corner
P.S. I refitting the sleeve in my blouse and if fits much better now (although I have found some more fitting issues -- apparently I have uneven shoulders). It's amazing what a difference the sleeves make! Even being rotated my 1/2" makes all the difference. : )