To be specific, I am going to create a dart in the armhole. The armhole is one curve from lower point in the side, to shoulder, via a couple of “helping” points. The center of the dart is a point on the curve. And then I want to go up and down 1,5 cm from the center point of the dart by following the armhole curve.

I am struggling to do so. I see how I can make fractions of a curve from the curve’s start point, and I could for sure do something like Length(Curve total) - length(startpoint to centerpoint dart) and then +/- 1,5, but I can’t seem to find a way to calculate, or find, the length of the curve to the center dart point.

Can someone guide me trough this, or point me to a tutorial?

This is a difficult one to explain, but I’ll give it a try. I use the ‘Slash and Spread’ method. I create the dart in the centre of the shoulder seam and I mark the point on the sleeve where I’d like the dart to be, as you have. And then, using the Rotate tool and selecting all the points from the point in the sleeve, including the curve, all the way to the nearest edge of the dart on the shoulder. I select the point of the dart where I’d like to rotate it from as the pivot point and then enter the formula to match up the nearest edge of the dart with the furthest edge of the dart.

This will rotate everything so that the curve remains true once the dart is in place and closes up the dart in the shoulder. Then you just need to draw in the lines of the dart from the centre to the edges of the curves.

It takes a little practice to get the original dart to close exactly, so what I do is I drag it until it’s as close as possible, finish the rotate (save my work before and after) and then go back into the options to play with the formula to get it exact.

Please let me know if this explanation helps. If not, I’ll try a small video

Thank you for the explanation, @Grace! I will try this a couple of times to see if I can make it work! No need for a video yet - I need my practice with the program But I am kind of happy that there not was an easy fix to this, as I really tried to make it work by myself. Which means I am not stupid which is always good to recognize

A small note about the formula for the rotation… In the formula, select Angle of Line and then select the one line and subtract the other line of the original dart from it. If it doesn’t work, then switch the formula, start with the 2nd line & subtract the 1st line from it.