Okay, you may be looking at these super tight swim trunks and thinking 'eeew,' my boys would never wear those, neither would I let them! If that's the case, I totally understand. I had never seen swim jammers until my boys were on a swim team last year and even then I thought they were pretty inappropriate at first. Which brings up the question, why do we let our girls wear skin tight and comparably skimpy swimwear without a second thought? But I digress... if your boys are not on a swim team you may like my DIY Boardshorts post better.
But I have 2 boys on a swim team, and I recently discovered how much $$$ I can save by sewing the boys jammers. They are totally not complicated. Think leggings made shorter in swimsuit fabric. In fact, I used a girl's legging pattern and swimsuit fabric and elastic from The Fabric Fairy.
With one yard of camo swimsuit fabric (around $10) and less than 2 yards of swim elastic (.45 per yard) I have already made both boys camo jammers. Woo hoo! FYI, that was their fabric choice, not mine. I have to compromise sometimes.
I have learned that the trick to making these fit right is measuring the body and the pattern first. I traced and cut out the legging size that matched my boy's height (cutting it off at the length I wanted). I carefully measured the front and back piece where I imagined his hips would be - without the seam allowances. Then I added these numbers together and multiplied it by 2 (for 2 fronts and 2 backs) After measuring my skinny boy's hips I found that the leggings would be 8 cm too large.
So I made an accordion fold lengthwise to remove 2 cm from each pattern piece. That would remove 8 cm from the shorts total.
I also cut the elastic to fit his waist exactly, ignoring the pattern's instructions.
And they fit! You'll have to use a stretch stitch or serger, just like working with other knit fabrics, but I think you'll be surprised by how easy and fast these are to sew.
And if your boys have never worn jammers before, they'll be surprised by how much faster they can swim. :)