It is out of the scope of this tutorial to teach you to sew; however, if you have any trouble there are many onlinegroups consisting of friendly experts just itching to help. If you have any questions about sewing feel free to post a comment here or email me at kellyhogaboom AT gmail DOT com.
Step 1: Gather Ye Materials; Measure Your Waist
1 yard Gore-Tex or other waterproof fabric
1 yard 1 1/2" elastic
1 yard 1" elastic
1 yard 1 1/2" web
1 yard 1" web
4 buckle fittings, 1"
1 buckle fitting, 1 1/2"
Fittings / closures for pockets: snaps, zippers, buttons, velcro
1 yard lining fabric
Sewing machine & needle (use appropriate needle for material - a universal should work on most waterproof mediums)
Men's pants pattern, including waistband
Seam ripper (never sew without one)
Ironing board & iron
Cutting mat & blade
Lighter (to fray-check webbing ends)
Take the following measurements:
Length from waist to the knee
Step 2: Pretreat, Trace, & Cut Pattern
Trace and cut pattern. If this is your first time using a pants pattern, note you will only need the waistband and front pants pattern pieces.
After you trace, tissue-fit to estimate the length, offsetting for waistband coverage. If you are not used to making measurements for sewing garments, I recommend you cut the pattern long and correct later in construction.
You can see in the associated picture I am tracing the men's medium. I trace all my patterns using a tracing medium from Folkwear (NAYY) but you can use many things: tissue paper, tracing paper, plain paper (taping to a window for light may help), or tracing medium bought in the fabric sections of most retail shops (interfacing may be substituted).
Step 3: Cut Fabric & Test Stitching
Two front panels (remember these will be mirror-images of one another; fold the fabric and cut as one for a shortcut), as well as the following strips, 2" wide:
2" strip, 2 lengths of the finished width at thigh
2" strip, 2 lengths of the finished hem width
1" strip, 2 lengths of 40" long
As you cut your pieces please keep in mind that many waterproof fabrics don't "heal" well from pin or needle holes. For instance in the Gore-Tex I used the right side of the fabric (green) healed from a pin hole, but the coated (white) side did not. As you can see in my cutting picture I don't use pins to secure my pattern pieces to fabric - but I've been sewing a long time and only take this shortcut when I'm confident it will work.
Thread your machine and sew on scraps. In my second picture on this step you see me toying with stitch length and writing down settings - the "6" corresponds to the longest baste on my machine, 6 stitches per inch, while the "10" (10 sts per inch) is a shorter stitch appropriate for this project.
When you have, found the right settings, fold over the short raw ends of waistband and finish (third associated picture). Congratulations, you have just constructed your first garment seam!
Step 4: Assemble Straps (Belt, Thigh, Knee)
Cut lengths from elastics as following:
From 1 1/2" elastic, cut 1/3 of finished waist length
From 1" elastic, cut 2 pieces to 1/3 finished thigh circumference
From 1" elastic, cut 2 pieces to 1/3 finished knee circumference
You should have five lengths of elastic and ten lengths of webbing at this point. You will be making five straps: one waist strap, two thigh straps, and two knee straps. The straps will be composed of an elastic section flanked by webbing, the terminal ends of these secured to the buckle closures (oh, just look at the third picture already!).
Assemble each strap as follows:
Join webbing to ends of elastic. Secure with two rows of sturdy zig-zag stitch, as shown in the first step picture. To the remaining raw edges of webbing, thread and pin the appropriate fittings. Measure before you secure them: the final length of the straps, with elastic relaxed, should correspond to the waist, thigh, and knee measurements you took.
Step 5: Construct Garment Shell
Sew the crotch seam and reinforce (picture two). I used a mock flat-felled seam because real flat-felled are sort of tricky on curves. Fold over and sew the raw edges of outseams and inseams (picture three). Note I am not finishing the edges since Gore-Tex has minimal fraying.
Construct ties: I topstitched 1/4" channels in the 1" strips wrong sides together and carefully cut close to seams (pictures four and five). Cut ties into four 10" strips and knot ends.
Step 6: Step Six: Assemble Casings
For the knee or hem casing, sew the 2" strip that corresponds to thigh length, right sides together with a 1/4" seam allowance. Flip casing strip to backside of pants. Lay the knee strap through, making sure your closures face the way you want them and sew your remaining casing seam with 1/4" seam allowance, being careful not to catch the strap (picture two).
For the thigh casing, sew the 2" strip wrong sides together at the upper thigh. Lay thigh strap through and sew remaining long seam parallel to the strap.
Step 7: Waistband
Your pants are ready for biking! These pair sold out almost immediately after listing on Etsy.