Readers, these are our final calculations. They may seam a little complicated now, but once we will be doing our real measuring session it will all become clear and easy. I will organize calculations on one sheet with measurements, so you will have only a few clear steps.
The purpose of this post is to explain the logic behind this patternmaking approach, as well as to close the darts chapter with final calculation.
WHAT WE DID BEFORE
- we measured depth (intake) and length of front, side and back darts.
- we checked the sum of all dart intakes against the difference between the hip and waist circumference (in ideal world these two values should be equal)
- we clarified some terminology: dart depth for the measured value, and dart intake for the final calculated value (we differentiate this terms only for our process, normally they mean the same thing)
WHAT WE NEED TO DO
- calculate relative error (a concept from high school math that helps reduce measurement error)
- calculate final dart intakes taking into consideration the relative error calculation. To simplify calculations, I use abbreviations which appear in brackets next to the corresponding term.
Do bear with me, it is still simple I promise.
RELATIVE ERROR (or how to reduce measurement error for darts)
Er = DI / DD
FINAL DART INTAKES
All we need to do now is multiply the measured dart depth (FD, BD, SD) for each dart by the calculated relative error (Er). FI, BI, SI stand for the corresponding front, back and side intake.
FI = FD x Er
BI = BD x Er
SI = SD x Er
We are finished with all the measurements, readers! I hope I managed to write it in an easy and coherent manner, however, if you notice any errors or typos please do let me know in a comment. What's left before the final drafting is determine the side seam placement, or, in other words, the front and back width. I'll be happy to answer your questions about darts, and if you want, I can add a post about the logic behind splitting the darts into two or more. Just let me know
Previous Straight Skirt Draft Along (SSDA) posts:
SSDA 9: Side Seam Placement and the Front/Back Width Controversy
SSDA 10: The Measuring Session Summarized
SSDA 11: Drafting the Skirt
SSDA 12: Making a Toile and Analyzing the Fit