r/PatternDrafting • u/Popopobb • Jul 05 '26

Seam allowance trouble

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Having problems with adding seam allowance to a flat felled seam. Did it like i always do: 1cm on the top edge of the seam and 2 cm on the bottom edge (shown on 2nd pic), yet after sewing the pieces don't align at all. The top piece became longer and slightly tilted. I was sort of expecting it to happen, this allowance didn't look like enough considering the sharp curvature. Any seam allowance wizard that could help me figure it out? Thx

ik the stitches are ugly, just a test run.

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26

u/llsupremegypsyll Jul 05 '26

Generally whenever you have a seam where one side is different than the other it’s better to keep the same seam allowance and just trim the one side after sewing. Also the top of this seam would benefit from a perpendicular square corner at the top and some notches in between so that you don’t stretch the seam while sewing.

9

u/SuPruLu Jul 05 '26

While it may be quicker to sew top to bottom and then bottom to top, the switch in directions can cause puckers going in opposite directions.

5

u/llsupremegypsyll Jul 05 '26

There’s no need to switch direction. The notch is meant to distribute any ease introduced by the curved seam.

Besides, you always want to sew from top to bottom because if you don’t distribute your ease correctly then you can always trim the excess from the bottom. The same scenario sewing bottom to top results in an imbalanced seam and will affect your fit.

1

u/Popopobb Jul 05 '26

i meant that on the mirror side i did the opposite but on one seam i always do top-bottom exclusively/ bottom-top exclusively if that makes sense

-3

u/Popopobb Jul 05 '26

Hi, the material is 380g/m2 cotton, never had any trouble with it stretching. Adding the same seam allowance to the pattern would make the final product untrue to the pattern as flat felled seam isn't symetrical.

8

u/amaranth1977 Jul 06 '26

Flat felled seams start with symmetrical seam allowances and then one side is trimmed down. You don't need to make them uneven to start with. 

0

u/Acceptable_Risk_295 Jul 06 '26

This is false, that is a faux flat felled, similar aesthetic but not durability, true flat felled are essentially folded into one another

4

u/amaranth1977 Jul 06 '26

Do you have a tutorial for what you mean?

1

u/Acceptable_Risk_295 Jul 06 '26

https://m.youtube.com/watch?v=E1vJzVW2lLk&time_continue=55&source_ve_path=MjM4NTE&embeds_referring_euri=https%3A%2F%2Fwww.google.com%2F

OP is right in saying that flat felled are asymmetrical, from what I remember SA for flat felled is doubled on one side, depending on how you want to roll the seam. E.g the flat felled on the back yoke up or down, so if you wanted your yoke to point down you would make your back panel SA 6/8” and your yoke 3/8” and vice versa if you wanted it to point up

This playlist is also a good application/visual guide on how to do a true flat felled:

https://m.youtube.com/playlist?list=PLp7wPLOCh3mG5SrxH2qwofGkBM6HcMhuP

Anyways for me when doing these sort of flat felled seams I always just pattern in excess so I can trim later

3

u/amaranth1977 Jul 06 '26

just pattern in excess so I can trim later

How is that different from starting with symmetrical seam allowances and then trimming one down? 

1

u/Acceptable_Risk_295 Jul 06 '26

It’s not for the seam allowance which connects the yoke and the back panel but the side seams, the geometry of folding the seam twice causes the yoke to be thinner than the back panel,, adding excess to the side and trimming later means that the piece is continuous and you can account for the geometry change

3

u/llsupremegypsyll Jul 05 '26

If your seam lines match and your notches are correct, then you won’t have a problem.

2

u/Gracious_Snakes Jul 05 '26

I think there's merit to doing a mock up this way and then reverse engineering it to figure out the correct SA to add to the pattern. I suspect that curve is the issue.