Umbra: FreeSewing's Underwear
Designer Notes
Umbra is a comfortable and flexible underwear briefs design that aims to be inclusive for as many people as possible.
Umbra is based on some experiments, prototypes and measurements of my favourite underwear.
Umbra is especially designed for diverse users. You can easily add several useful modifications, even if some of them are not directly supported by the software.
Some features of Umbra are as follows:
- It can be sewn so that no (potentially itchy) seam allowance touches the skin, which helps people with sensitive skin and those with autism. The crotch and side seams are placed on the inside between the front part layers and any elastics on the waist and leg openings can be put on the outside, if so desired.
- It can be sewn with or without a bulge. You can even draft the design twice, and cut the front lining without bulge and the main fabric front part with one, and you’ll be able to create a front pocket with plenty of space.
- Rise, back exposure, front exposure and gusset width are controlled separately, so you can create e.g. very comfortable thongs with enough room in the front, or many other designs.
Umbra is based on code from Uma by Natalia Sayang and Joost De Cock, but has been heavily modified in its construction and default style. Some key differences are:
- Umbra doesn’t have a separate gusset part and instead adds lining to the whole front piece.
- The hip measurements are being taken into account to better determine the waistband size.
- The height of the underwear is based on the usually more accurate Cross Seam measurement instead of the Waist to upper leg measurement.
- The positions of the side and crotch seams can be adjusted freely, even with a bulge selected.
- The back part has a smoother, more comfortable curve and provides greater coverage by default and at maximum.
Jonathan
Be sure to adjust the “horizontal fabric stretch” and “vertical fabric stretch” options according to your fabric. The default stretch values are rather low. If your pattern appears huge compared to store-bought underwear, they probably use much more stretch.
If you wish to adapt Umbra to a swimwear bottom, it should be easy to do so. Simply use swimwear fabric and, if desired, sew on a folded over piece of fabric with two holes instead of a waistband elastic, to create a drawstring.
What You Need
To make Umbra, you will need the following:
- Basic sewing supplies
- About 0.7 meters (0.8 yards) of a suitable fabric
- About 3 meters (3.3 yards) of underwear elastic, such as picot elastic or fold over elastic
Binding methods may affect the seam allowance
If using fold over elastic (FOE) or doing knit binding, you may wish to trim away the seam allowance at the legs and waist before cutting. If you keep the seam allowance, the finished product will have a slightly higher waist and slightly smaller leg openings.
A serger/overlock is nice, but optional
As with all knitwear and stretch fabrics, a serger/overlock will make your life easier. If you do not have one of those, don’t despair. You don’t really need it. You can just sew Umbra with a zigzag stitch or with various other stretch stitches.
Fabric Options
You need a fabric with plenty of horizontal and vertical stretch (sometimes called “four-way stretch”) for this pattern. Preferably something that is comfortable, soft, and breathable.
Recommended fabrics include stretch jerseys, stretch mesh, stretch knits, or most fabrics with at least 5% spandex. For example, modal (rayon) jersey with spandex.
To test the stretch of your fabric, hold a known length of fabric against a rule. Then measure the length you can stretch that length of fabric to. For example if you can stretch a length of fabric from 10 cm to 18 cm, that fabric has a max stretch of 80%. If you can only stretch it to 13 cm, the stretch factor would be 30%. Measure the stretch in both directions (horizontal and vertical).
Good underwear fabric should have a max stretch of at least 60-80%. Store-bought underwear often has fabric with a stretch factor of around 150% (which means it can be stretched to 2.5 times the original length). If your fabric has a stretch of only around 30%, it’s probably pure cotton and less suitable for underwear.
Be sure to adjust the “horizontal fabric stretch” and “vertical fabric stretch” options according to your fabric. Do not enter the max fabric stretch, enter the stretch you want the fabric to be when worn.
If you have fabric with over 100% stretch, a good value for the horizontal stretch is 30%-50%. If you have fabric with around 80% stretch, a good default value for the horizontal stretch is 30%. If your fabric has 30% stretch, choose 15% horizontal stretch or less. If you want to use zipper pockets, go with a low stretch as the zippers can’t stretch themselves.
Fabric will wear out fast if you wear it near its maximum stretch, it will also be very uncomfortable.
Note that the thickness of the fabric also affects the stretch you should enter. Go with lower stretch for thicker fabric.
The vertical stretch can be much lower than the horizontal stretch. If you use a fabric that stretches more in one direction, use that for the horizontal direction. A good general value for the vertical stretch is around 5%. If it is too high, the fabric may press uncomfortably against your crotch area.
- If you use a different fabric for the lining, make sure it has around the same stretch as the outer fabric.
- If you use the same fabric for the lining, make sure to mark the lining piece, as otherwise both pieces may get confused easily during sewing.
Cutting Instructions
Umbra consists of a back piece and a lined front piece. This is the cut list:
- Main fabric
- Cut 1 front
- Cut 1 back
- Lining fabric
- Cut 1 front
If you use a serger, you can cut away excess fabric with the knife, so use standard seam allowance.
If you don’t have a serger, I recommend using an overlook foot and a flexible overedge / fake overlock stitch with a seam allowance equal to the width of that stitch (usually 5 mm).
If you want to finish the leg openings with fold over elastics, you may want to skip the seam allowance for the leg opening on all parts.
- Umbra is a great scrap buster. If you have fabric scraps from making a Teagan t-shirt or anything from a jersey fabric that has good stretch, this is a good way to use those up. If you only have smaller pieces, instead of cutting the pieces on the fold, you can cut both halves separately and sew them together. However, this introduces additional seams.
- You can use the same fabric for the whole garment, including the front lining. Some people prefer using softer fabrics or different materials for the lining.