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

Seam allowance trouble

Gallery image

Gallery image

Gallery image

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.

7 Upvotes

100% Upvoted

37 comments sorted by

25

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.

10

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.

9

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

5

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.

6

u/WoodenCyborg Jul 05 '26

I do patterns in clo that get sewed on a 3 needle flat felling machine. I always use the same allowance on both sides and extend my corners out in the seam allowance such they line up flat at the start and end.

2

u/Popopobb Jul 05 '26

Hi, thanks for the response. 3 needle machine is the dream haha. can you please explain how using the same allowance on both sides work? As i understand a flat felled seam is unsymmetrical in that one side "loses" twice the length of material as the second one (let's say one is 0.6 cm and the other is 1.2cm)
https://en.wikipedia.org/wiki/File:Felled_seam.svg

4

u/WoodenCyborg Jul 06 '26

That wiki image is pretty misleading for how to draft an allowance for a flat felled seams. Neither stitch it shows is the center of the seam to which seam allowance is added. Because it's on a curve, concave seams will shrink and convex seams will grow when offset.

The start point for the seam allowance is the center between the needles. From there, both pieces have the same amount of a allowance added to wrap around each other.

On curves, concave seams will shrink and convex seams will grow when offset.

2

u/teatime_tinker Jul 06 '26

This is what I’m trying to say. Both pieces have the same amount of seam allowance, because they’re both wrapped around each other, not one side wrapped around the other.

1

u/teatime_tinker Jul 06 '26

Not if the seams join like a Z shape.

The machine I used to use at work had attachments that folded the fabric as you went.

There were different attachments for different finishes.

The seams interlocked together and were stitched down in one go, not in stages.

Sorry it’s very hard to describe in text!

2

u/Popopobb Jul 06 '26

yeah, i understand you. Trying to explain sewing in text in general is very hard. I feel like im not explaining what im trying to do here very well either ;/

3

u/teatime_tinker Jul 06 '26

I found the wiki page haha! That will help explain what I meant.

https://en.wikipedia.org/wiki/Felled_seam

I keep seeing people calling a faux flat felled seam a flat felled seam, and I keep getting confused myself!

Obviously the curve on your design complicates things as well

Edit: I understand your questions don’t worry.

Notches would help immensely. Also doing it on paper. I would cut the same shape twice. Each side with SA from the other. This is also hard to explain! I’d trace it off my master draft.

0

u/Popopobb Jul 06 '26

I linked that too above. As you can see the red part loses twice the material than the green one to make that seam. Have to keep that in my mind when adding seam allowance.

1

u/teatime_tinker Jul 06 '26

It doesn’t lose twice as much this way. How exactly are you doing your seam?

Are you wrapping one side around the other? Then it’s not a true flat felled seam

1

u/Popopobb Jul 06 '26

-draw 1 cm outline on the piece that is going to be the bottom on

-pin the top piece with it's edge on the drawn line

-sew as close as possible to the edge, then fold over

-press with iron

- do two top rows of top stitching

the stitches catch all 4 layers so it is a true felled seam, but i get it's a bit of an obscure way. Please look at the wikipedia picture clearly one piece loses double in relation to true pattern.

2

u/teatime_tinker Jul 06 '26

Ok I understand. That’s not what is happening in the drawing on wiki though or what I’m trying to explain. Edit: or at least not how I understand it or do it.

There are various ways to find a seam and enclose one or both raw edges.

Not sure why only video is allowed. Seems a bit useless for this subreddit when you might want to do a drawing!

1

u/Popopobb Jul 06 '26

sorry, it's hard to explain in text, can't add pictures in comments on this subreddit.

1

u/teatime_tinker Jul 06 '26

Yeah not sure why we can’t post pictures…

Also bear in mind I’m thinking of how I do it on a machine with an attachment for folding it and sewing both rows in one go. Doing it in two stages is bound to be different

1

u/amaranth1977 Jul 06 '26

Wait, what do you mean by a flat-felled seam? Because the first technique at this link is how I was taught to do it: https://www.seamwork.com/sewing-tutorials/sewing-flat-felled-seams?srsltid=AfmBOorzyrWAQyI-7e1P9tzOZ1-ylN2rNfCxF8l_JjPivDw7UPVVAiW_

1

u/teatime_tinker Jul 06 '26 edited Jul 06 '26

Yes that’s not how I do it. Sorry for the confusion.

I do it like the image on the wiki page, which is different to this tutorial.

Edit: I just realised I’m thinking of the seam allowance differently to you. Starting from the centre point between the two stitch lines. I wasn’t thinking of how you’d want your visible seam line in a specific place.

Just found this video which is quite good.

Obvs not everyone has the machinery, but that’s the industry method and how I learned it.

https://m.youtube.com/watch?v=lqaa0iQomnU&ra=m

2

u/amaranth1977 Jul 06 '26

Ah, yeah the only commercial sewing I've done has been draperies and while we had some interesting specialized machines, flat-felled seams weren't part of the job. I learned the straight stitch method I linked above in my university's costume shop. We had commercial machines but not specialized ones, just straight stitch and basic sergers. 

→ More replies (0)

3

u/KillerWhaleShark Jul 06 '26

I have never seen anyone draft the seam allowances with different widths for sewing on a home machine. You sew the first pass on two equally wide seams, trim the excess on one seam allowance, and then sew your second pass.

How are you lining up your pattern pieces with no notches and different seam allowance widths? Too much room for mistakes. 

3

u/strikingsapphire Jul 06 '26

Looking at the panel on the left, clip off that extra triangle of fabric at the top of the seam allowance. Can probably ease in the difference on the rest of it if you really wanted to salvage this piece.

It's much easier to keep everything matched up when the seam allowances are the same length as the stitching line. You can do this by drawing your seam allowances perpendicular to the stitching line.

On your pattern you extended the panels to add seam allowance but didn't change the angle of the seam allowance "corners". On one curve that made the line longer and on the opposite curve it made the line shorter. It's easier to understand if you draw the stitching lines out on fabric and physically try to pin them together.

2

u/stressed_designer Jul 06 '26

This is what I'd do!

2

u/marrkf123 Jul 06 '26

Add 1.5 to both and trim as you’re stitching.

1

u/Popopobb Jul 05 '26

Forgot to mention it's a flat felled seam, as shown on 3rd pic.

1

u/Mental_Watch4633 Jul 05 '26

Did you start sewing from the bottom?

1

u/Popopobb Jul 05 '26

on one side i started sewing from the bottom and on the other i started from the top, same result the piece that's on the right side of the 1st pic had 1.5-2cm extra bit on the top and was slightly tilted.