On a t-shirt or stretch dress, the shoulder carries heaps of weight. It is also generally cut directly across the stretch of the fabric, which means it is likely to distort.
To overcome this problem, most t-shirts include a stabiliser (stabilizer) in the shoulder seam. If you take a peak inside your t-shirts you will see this. It's a little extra something sewn into the seam at the shoulder.
There are a few different things / approaches to try.
Cotton tape / twill tape.
t-shirt dress was like sewing with liquid. The fabric was incredibly soft and stretchy! (It is very comfortable to wear.) So I included a cotton twill tape on the shoulder.
You will probably have seen this before in commercial t-shirts, although mine is sewn in with a straight stitch because I don't have access to an overlocker. I have stitched these to the seam allowance with straight stitch, and I have stitched them in with a zig zag, and when I had an overlocker, I have overlocked them in. In any case, they work the same way. This is probably my favourite for loose 2 way stretch fabric. General and appropriate advice is that you should pre-wash anything cotton because it might shrink. I will hand out that advice over and over again. Truthfully, I am a little lazy in this respect in real life, and occasionally have paid the price for that. But its easy enough to chuck your cotton tape in a lingerie bag and throw it in the machine with the rest. Cotton tape is very soft and comfortable to wear.
|You may be interested to know, that Hemline clear elastic has been described on seller websites as being resistant to salt, chlorine AND urine. Let that take a load off your mind.|
Here's one that's been overlocked in, on a commercial t-shirt. A quick and informal survey of my t-shirts showed this approach most of the time. Without an overlocker, just zigzag stitch the elastic in the seam allowance. Too easy. The elastic is about the same size as the seam length, possibly just a tiny bit tighter to hold but not pull the seam. It be firm but shouldn't gather at all.
Clear elastic can also be used to hold gathers, like on this sleeve.
I've seen it applied successfully to sleeves without seams by stretching a piece of elastic over the desired area, and zigzagging it on. Likewise, the same approach can be used create the gather over the bust on leotards, and to enhance a sweetheart neckline, on stretch or woven fabric.
I've also used it to support vertical gathering. When I made my stripey dress, I found the weight of the gathering was pulling the dress down. By adding a piece of clear elastic to the seam, I was able to bring it back up again. So that's handy to know.
Here, they've used a strip of self fabric, but cut vertically from 2 way stretch. It pretty much disappears into the seam, and given that it can be made off an off cut, would have the added bonus of being free. Can't fault that.
I have heard of people using woven selvedges as stay tape, although I haven't tried it myself. I would definitely want to pre-shrink those though.
Using a similar idea to binding the edges (tutorial here), a shirt may have a strip of stretch fabric folded over and chain stitched from the shoulder and across the back neckline as well. I've found this on quite a lot of shirts and it adds strength and stability to the back neckline as well.
And can be a design feature.
This is what it looks like from the top.
You could also bind just the shoulder seam allowance.
Other bits I've heard but not tried, include fusible interfacing (I believe stretch interfacing is available on a roll for this purpose) and stay tape. I'd be interested to know what others have found with this. Let me know!