Project 002 — Drafting a Flat Brim Sunhat
This post may be truncated in email readers but the full post is available on Substack. Happy drafting!
Hello my sewing mathy friends! Today, we're going to ease in to drafting with circles by drafting a flat brim sunhat, or stovepipe hat. In case you missed it, last week I shared how to measure for a hat and methods for drafting using paper and digitally, using Adobe Illustrator. Check out that post here:
I made my first stove pipe hat many years ago (about 25?) when my little brother requested a Cat in the Hat style hat. He had a, let's say, "unique" style of dressing. I used felt so that I didn't have to finish any seams and drafted a simple hat using circles. And, because it wouldn't be a true Cat in the Hat style without it, the sides of the hat were very tall and striped.
A stove pipe hat has just three pattern pieces: a circle for the crown, a rectangle for the side and a ring for the brim. This design is the most (literally) straightforward of the hat drafting we’re exploring. The crown is a circle (as opposed to an oval). The side is a rectangle, with no tapering. And the brim is a ring, composed of two circles. Let’s dive in!
Today's lesson
To draft this hat, we’ll start at the Crown and work our way down to the Brim.
Part 1: Collect information (Write down all the measurements, ease, seam allowance, etc.)
Part 2: Draft the Crown
Part 3: Draft the Side
Part 4: Draft the Brim
Part 5: Download the worksheet and watch the video of how to draft this hat in Adobe Illustrator
Part 1 Collect Information
To make your own custom fit hat, you’ll want to gather a few measurements. Read last week’s post for more info on measuring yourself for a hat. Also, we’ll be using our old Circumference and Diameter formula to draft the circles. So, keep in mind that Circumference = π * Diameter = 2π *Radius. Also, the Diameter = 2 *Radius.
I’ve assigned a representative letter to each number we’ll need. I’ll use these letters to write the drafting formulas. When drafting your hat, you’ll replace the letters with your own numbers.
A Head circumference
B Ease at crown This is personal choice. I recommend measuring the inside of a hat that you like the fit of and then subtract your head circumference to find the ease you like.
C Seam allowance Designer’s choice
D Side Height 3-4” is pretty standard. Again, you can measure a RTW hat you like to help choose this number.
E Brim radius This is how far the finished brim will stick out from the head. A Cat in the Hat style has a small brim. Or, go larger for a more traditional or dramatic sun hat.
One crucial thing to understand about this design is HOW all the pattern pieces fit together. The Finished Head Circumference (let’s call it FHC for short) (which is the A Head Circumference plus B Ease at Crown) is used in every pattern piece. The FHC is the finished size at the top and the base of the hat. In the image above, the FHC is represented as a red dashed line. It’s also length of the seam line for the Crown, the top and bottom of the Side piece and the inside of the Brim. A very popular number!
Part 2 Draft the Crown
The crown is just a circle with seam allowance added. To draft the crown, we will use the FHC to find the Diameter of the circle and then add the seam allowance. We will need A Head Circumference, B Ease at Crown and C Seam Allowance.
As we discussed last week, if you are drafting on paper, you’ll use the Radius of the circle. If you are drafting digitally, you’ll use the Diameter.
Remember that the Finished Crown Circumference = A Head Circumference + B Ease at Crown, in short FCH = A+B.
So using our circle formulas, the Finished Diameter of our Crown is (A+B)/π. A circle with this diameter is the Seam Line for the hat. To make it a finished pattern piece and create the Cutting Line, we need to add C Seam Allowance. So, the Pattern Piece Diameter = (A+B)/π + 2C.
If you need the radius, you can solve for the diameter and then divide by 2. Or, solve for Pattern Piece Radius = (A+B)/2π + C. (For the radius formula, you only need to add the seam allowance one time, because it’s half of the circle.)
When drafting the circle, I also recommend marking the quarter points of the circle to help guide you when constructing the hat.
In case it’s helpful, here’s an example of how to calculate the Crown. When calculating with π, we end up rounding numbers. I wouldn’t bother going farther than three decimal places.
Calculating the Crown Example
A = 22”, B = .75”, C=.375”
Diameter = (A+B)/π + 2C = (22.75)/π + 2x.375 = 7.245 + .75 = 7.995
Radius = (A+B)/2π + C = (22.75)/2π + .375 = 3.62 + .375 = 4
Part 3 Draft the Side
To draft the side pattern piece, we will use A Head Circumference, B Ease at Crown, C Seam Allowance and D Crown Depth. The side pattern piece is a rectangle with the width equal to the FHC and the length equal to D Crown Depth, plus the seam allowance added to all sides.
The formulas are:
Hat Side Width = A + B + 2 * C
Hat Side Length = D + 2 * C
Part 4 Draft the Brim
The brim pattern piece is a circular ring, essential a donut shape. Yum! The interior circle has a seam line that is equal to the crown seam line. To draft the Brim pattern piece, we will use A Head Circumference, B Ease at Crown, C Seam Allowance and E Brim Radius.
One way to draft this pattern piece is to draw a circle with Diameter = (A+B)/π. Then expand that circle by E. That second circle has the diameter (A+B)/π +2*E. Finally, add the seam allowances to the inside of the first circle and the outside of the second circle.
Or, if you want to be a little more straightforward, you can draw two circles with the seam allowance already included.
Brim Exterior Diameter = (A+B)/π +2xE +2xC
In this formula, we calculate the diameter of the FHC then add the Brim Radius and Seam Allowance, (twice because it’s the diameter).
Brim Interior Diameter = (A+B)/π - 2xC
In this formula, we calculate the diameter of the FHC then SUBTRACT Seam Allowance, (twice because it’s the diameter).
The crucial (and I think cool) part of this formula is that we actually SUBTRACT the seam allowance from the interior circle. Btw, I talked more about seam line vs cutting line when drafting curves in last week’s post.
Part 5 Worksheet & Digital Drafting Example
I couldn’t resist putting together a PDF worksheet that you can use to draft this style of hat. Click below to download the one page worksheet which includes the Notes/Measurements needed and the formulas for each pattern piece.
Click here to watch the video on Vimeo
Finally, I made a video showing how I would draft this pattern in Adobe Illustrator. In the video, I use the ellipse and rectangle tools to draw the pattern. Plus the Align and Pathfinder palettes. And, I show how to create a seam line. Fun stuff!
I hope you enjoyed this post! It was fun to play around with these formulas, especially for the donut shaped brim. You can use this design to make a costume hat or to make a flat brim sunhat. With this flat style brim, the bigger the brim radius gets, the floppier and wavier the edge of the brim will be. Next week, we’ll draft a bucket hat with a brim that is more tapered like a cone.
Happy mathing!
Beth
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This is brilliant, thank you!