Friday, March 13, 2009

Mirrored sideseams

On the Patternmasterusers chat list on Yahoo, we've been discussing these undesireable wrinkles that frequently occur just behind and below the back armhole of PMB garments, especially on Princess styles. I mentioned that, on my patterns, the Princess style creates a 'gap' between the front and side front patterns at bust level and that this loss of bust width is compensated for by increasing the width of the back pattern at underarm. But this changes the shape of the back sideseam...I've talked about sideseams before.

But hours later, I'm still thinking about those wrinkles of fabric at the side/back armhole area. So I opened PMB and drafted and compared a few patterns...not even Princess ones, but just the basic Torso. I used my own measurement chart with ZERO ease at bust, waist and hip. I set the SS position to ZERO at bust, waist and hip. Below, you can see what I would get.

If I aligned the back to the front at the underarm points, you can see that the back pattern extends lower at the hem than the front pattern. But think of it (and look at it) this way: When I align the front and back at the hems, you can see that the back armhole level is HIGHER than the front armhole level. And this is because the sideseams are NOT mirror images.

Now, I can imagine that because this back armhole is higher than the front armhole, once the sideseams are sewn and the sleeve is sewn in, it is likely that this higher back armhole will be 'forced' downward on the body, creating folds. The balance of the patterns is off.

With the sideseam positions set at ZERO as above, the HEIGHT of the back armhole is 8.471".
The HEIGHT of the front armhole is 7.743" (as measured straight up).

But look at what happens if the SS tools are used to 'force' the front and back sideseams to become mirror images: When the Front and Back patterns are aligned at the hem, there is only a tiny difference in the heights of the front and back armholes...and it is the FRONT that is higher, not the back!

To force the sideseams to become mirror images, I used a Side/Arm Position of (-1) and a Side/Hip Position of (+.5). As you can tell by the size of those waist darts, the S/W position is still in the ZERO position, but that setting only affects the size of the waist darts, not the placement of the waist at side seam.

With the sideseam in this position and the front and back sideseams having mirrored shapes, the HEIGHT of the back armhole is now 8.954" and the front armhole is now 7.326" tall.

This means that moving the sideseam as I have had changed the balance of my patterns...I have gained 0.483" in back armhole height, and lost 0.417" of front armhole height!

I am thinking that the taller back armholes combined with the shorter front one is less likely to result in the folds of excess fabric that are fequently seen on PMB garments in back. Not a scientific study or anything...purely conjecture!

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