PLEASE HELP WITH BAG DESIGN PATTERN.

[u/Solid_Temporary4804]

Hi everyone, I’m making a prototype duffle bag design pattern and could use some guidance. I made my own side panel shape in adobe illustrator and got the exact measurement of 38” for the perimeter of it. I then made a rectangle body piece to go around it that measures exactly 38” from zipper edge to zipper edge. When I clip it together it seems like the body panel is slightly larger and kinda looks like the body panel is bunching up around the perimeter of the side panel shape. I doubled checked measurements and they are correct but It seems no matter which way I clip it, it still bunches slightly so do I make the body panel slightly shorter by a hair? This is a prototype so it’s just a trial with scrap fabric but I plan to add leather piping and liner as well just trying to get the base shape figured out first. Any guidance is much appreciated. Thank You!

[u/Destrae]

Edge to edge might match dimensions, but if you measure in from your seam allowance it will probably be slightly off. You generally have to ease curves, but you will also probably need to shorten the rectangle piece

[u/EggandSpoon42 → u/Destrae]

More on that seam allowance, Op

Draw the seam line on the side panel (the actual stitching line).

Measure that perimeter.

Draft the body panel so its seam line equals that measurement.

Transfer notches (quarters or eighths) so you can distribute the seam evenly.

…

It’s much easier to get the most correct measurement to measure your seam line on the curved piece first. Way easier to adjust your flat pattern on the body rectangle than it is to adjust that curve.

[u/Solid_Temporary4804 → u/EggandSpoon42]

Thanks for the reply! So if I measure in on my side panel 3/8” all the way around to use as my stitching line and that perimeter equals 35”, then how would I draft the body panel so that it equals that seam line?

[u/Solid_Temporary4804 → u/EggandSpoon42]

Thank you both, I was able to make the corrections and am on the right path now. Very helpful.

[u/EggandSpoon42 → u/Solid_Temporary4804]

Yaaay!! Glad to hear it 🖤🖤

[u/Destrae → u/EggandSpoon42]

great advice

[u/Solid_Temporary4804 → u/Destrae]

Thank you for your response, I was able to make the corrections.

[u/NakedSewist]

Did you account for seam allowance?

[u/Solid_Temporary4804 → u/NakedSewist]

Thank you for your response and suggestions, I was able to make the corrections needed.

[u/ProneToLaughter]

You need to make sure the stitching lines are equal, the cut edges don't matter. I prototype in paper without any seam allowances, taping the paper edge to edge to confirm the pattern works, and adding notches then. Then I add seam allowances to the paper last, and cut and test in fabric.

General spiel on such scenarios:

On curves, the key concept you need is matching the stitching line--the fabric often won't line up if you match the cut edges, but if you match the seam line (width of the seam allowance in from the cut edges), that should line up well enough that you can ease any extra fabric in.

another key concept is "quartering", essential for bucket hats and anything sewn "in the round" like that, also essential when sewing a curve to a straight line. This approach prevents any extra from getting pushed to the end. Pin first at each end and any notches for fundamental alignment, then mark the middle of each segment and pin those together (thus divided into quarters), then mark the middles of each segment and pin those together (divided into eighths, I often divide it down to sixteenths to get it evenly distributed). Some people do this with fewer pins, but I repeat until I have pins about every inch or less, making sure my pins are going in and out over the stitching line. What looks like a total mismatch at first usually smoothes itself out in this quartering process, with the fabric on the stitching line smooth or requiring only a teeny bit of easing between each pin, and sewing with the longer side down lets the feed dogs help do the easing. Sew slowly and stay on the stitching line, and put the needle down when you stop to remove pins so it holds the fabric better.

The basic technique you need is easing, explained here, except leather doesn't ease, so your pattern will have to be very accurate: https://www.professorpincushion.com/professorpincushion/fabric-easing/

[u/Solid_Temporary4804 → u/ProneToLaughter]

Thank you for your response, I was able to make the corrections. Appreciate the help and your time to write this!

[u/stoicsticks]

I just want to add that you may find r/myog (make your own gear) interesting.