Converting pattern non-stretch to stretch

Has anyone had success converting patterns for non-stretch fabric to
stretch fabric? The pattern I'm considering is for a 3+ piece-cup bra
(the + being a side shaper panel). Just the cups need converting, not
the frame. I kind of wondered whether it might be doable with
Photoshop using the "Image Size" tool. Basically
1) Scan each pattern piece (minus seam allowances) with the grain line
vertical and crop until each side of the window touches the pattern.
Read the length and width measurements.
2) Determine the fabric's percentage of stretch lengthwise and
crosswise. Compute the desired finished measurements and input
3) Photoshop will redraw the image with the proper proportions. Add
SA's back on.
Does this sound right?
One big question is whether the fabric will stretch to its maximum
when worn normally. (Do people who work with stretch know of any rule
of thumb?) The purpose of this is so that the garment provides more
"give." At a guess I think I should assume about 85% of maximum.
Does anyone recommend higher or lower? Does anyone think I should
only stick to 4-way stretch fabrics, the kind that are guaranteed to
have the identical stretch even in diagonal directions? I have no
clue about that...
Any thoughts appreciated!!
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Dear Pora,
If you enlarge or reduce just the cups, the pieces won't fit into the original pieces. Am I to understand that all you want to do is add a side stretch panel? If so, all you do is draw the width of the side panel onto the upper cup and lower cups, and cut this off the cups. Add seam allowances and notches, so that you know how to sew it back together.
When I was teaching (now retired), drafting a bra was the last lesson. A bra, like all other women's garments, is drafted from the model's sloper. I think I still have the workbook pages somewhere. If you're interested, please e-mail me privately and I'll send them to you.
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No no. I want to do the cups in stretch fabric like lycra. Right now the pattern is for completely non-stretch, like simplex or lace. Not fitting into the frame shouldn't be an issue, since they'll stretch to match along the wire line.
Now that I'm making more sense do you foresee problems with my method? Obviously the pieces need to be smaller, but by how much? And if the fabric stretches differently in the various directions, this makes redrawing the pieces impossible for me without, say, Photoshop.
If so, all you do is draw the width of the side
Thanks Teri. Although I've got a manual, it does not include drafting from a sloper. (Beverly Johnson's Bra Maker's Manual is on my birthday list ;-) )
Reply to
Dear Pora,
Your method seems a bit complicated. Why not do a test, using the spandex for the cups, and see what happens. The spandex is a certain percentage of the total fabric. I would determine the percentage of spandex (probably around 10 percent), and reduce the cups by that amount. And you're right; I think it will stretch to fit the side panels without changing anything else.
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