After last week Bias: Definitive Essential Foolproof Guide post, today I want to go practical: how can I bias cut a rectangle, having only its measurements?
Math is closely related to sewing and I feel like a lot of self-taught sewists try to skip this part, but I think it’s a huge mistake: math is FUN – and I’m going to teach you a quick and practical trick!
Let’s talk about Pythagoras Theorem!
One of the features of The Sheer Plaid Top (my first pattern to be sold – actually under testing – release date February, 1st) is a softly draping collar, bias cut without a pattern piece, only having its measures…
I received so many questions about how to do that, that I realized it wasn’t as obvious as I though!!
Let’s clarify, and I hope that, when you’re finished reading this post, you’ll catch how easy is to bias cut a rectangle!
Bias Cut – Practical Trick
As we know that bias is at 45 degrees to a fabric’s warp and weft threads, then we can use Pythagorean’s rules about triangles!
Look at my example photo: as you can see, my meter stick is placed exactly along the bias (hypotenuse of our right-angle triangle isosceles), because the width (A) and the height (B) of the same triangle (where I put my measure tapes) are the same length.
Believe me or not, if you know your hypotenuse length (=our bias length), you can calculate width (A) and height (B) with this easy formula:
where square root of 2 is ALWAYS 1.4142135
Ok, let’s simplify for those who don’t eat bread and math for breakfast!
Our example bias piece will be 25 cm long, 3 cm height, so:
- Measure from your fabrics angle between crosswise direction (A) and selvedge (B) the same measurement, that is:
25/1,4142135= 17,7 cm
- Fold your fabric along the bias line (you can help yourself with some pin, of a chalk line…)
- Measure desired height at right angles to the bias (3 in our example)
and cut again!
- Finally, cut out your strip heads, just to have a rectangular (and not trapezoidal) shape:
Is that hard to do? Not really…
Hard to remember? You don’t have to, simply …pin this post 🙂
That’s all for today, stay tuned to discover what comes next…