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Tips & Techniques > Perfect swimsuit and underwear leg elastic.

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Posted by: BrianSews

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Member since: 2/16/08
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Posted on: 3/17/09 7:47 PM
Review Rating: Helpful by 8 people   Very Helpful by 57 people   
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The function of elastic on a swimsuit is to hold the garment edges to your body while you move, hopefully without cutting into your skin.

In sewing swimsuits and underwear I used to do the technique where you measure your leg and subtract a few inches for your elastic length. Then sew the elastic into a loop and pin it in quarters onto the inside of the leg opening. This worked for getting the elastic on the leg evenly but actually failed to function properly at holding my swimsuit in place and looking nice.

Elastic actually only need to be tight in the lower crotch area, between your legs. This is the spot where you want full security and no gaping when you move, sit, squat, climb stairs, play volleyball or whatever. Tight elastic on your butt or thigh cuts in to the flesh making your suit look too small or you look too big no matter what size you are. Plus your suit will lay so much nicer if the fabric isn't being gathered by elastic in those areas. Think nice smooth curves!

I've found a better way. Like most techniques it requires a little practice but it really pays off. It's all about redistributing the stretch of the leg openings to where you need it. To attach elastic you can use a serger or zigzag. I prefer zigzag for easier control and serger for speed. I always remember to exercise my elastic before I use it, stretching it out at least three or four times. I mark on my suit about two inches on either side of the bottom crotch seam, you will need to experiment to determine how much to mark since we're all different sizes.

Start sewing your elastic outside this area stretching it just slightly as you sew. If you leave a small lip of fabric on the edge of the elastic the stitching will tend to curl that fabric up over the edge creating a very nice finished look when you turn it under and top stitch. When you approach your mark give it some good stretch. I usually stretch it to the maximum so this area really cinches in. Resume light tension when the other mark is reached. When I meet up with the other end of elastic I cut off so that the raw ends match up with NO overlap. I then zigzag the ends together which creates a flat transition and no lump on the outside.

If you practice you'll notice that even though you don't measure the same length of elastic for each leg both legs will match. Turn your elastic under and top stitch while stretching as necessary. I like to stitch from the back so I can sew exactly on the edge of the elastic.

Try it, you'll like it!

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kkitty said... (8/22/16 0:09 AM) Reply
Hello! Thanks do much. I am going to buy my sewing and serger machines, I love make swimsuits, Could you please give me advise, which brand and model I should choose. Thank you again :)
SewMentalMama said... (5/25/15 5:44 PM) Reply
This tip has saved me a trip to buy clear elastic and has made me 'want' to sew swimwear for the first time ever, Thank you! I've just Blogged the swimsuit I sewed using this tip.
EcoThreads said... (6/14/12 1:13 PM) Reply
Thanks so much for this explanation! Ive sewed 3 underwear & a swimsuit for my daughter and was getting so frustrated trying to get the plastic elastic to work (good to know I should've just dumped it and went with regular elastic). I was ending up with stretched out looking leg holes or too tight leg holes. Your method came out much nicer and laid flat. thank ya!
Beryl Koster said... (3/17/12 1:11 AM) Reply
Thankyou, this is exactly where I am at! And yes, the crotch area can look a bit untidy with overlaped elastic, let alone bulky to sew.
Silvanahappy said... (6/12/11 8:01 PM) Reply
Hi, I want to make a swimsuit with more professional look. To make the double sewing I need a serger or I need a coverstitch? thank you so much :-)
Miss Fairchild said... (4/1/09 8:41 AM) Reply
Great tip! I'll have to try this.
brrmm said... (3/28/09 6:41 PM) Reply
Hi RB, what sort of stich do you use for your top stitch? Just interested cause your work always looks very professional. Also when you butt (pardon the pun!) the elastic together does it sort of come apart - whenever I've tried this it does. How do you make sure it stays together?? Cheers!
Judy Kski said... (3/23/09 12:52 PM) Reply
I really appreciate that you took the time to write such a great tip to share with everyone. I will definitely use this the next time I sew a pair of underwear. Thanks!
Mebber said... (3/19/09 11:29 PM) Reply
Great technique- thanks for sharing. Puts me back in the swimsuit sew...
lady a said... (3/19/09 10:30 PM) Reply
will try putting elastic on underwear this way. sounds sensible and much easier.
TracyaR said... (3/19/09 8:23 PM) Reply
Wonderful tip ... I love the idea of only catching the elastic on the zig and not the zag. Hope you do a photo tutorial but your words are very clear. Thanks!
BrianSews said... (3/19/09 9:16 AM) Reply
One of the advantages of using a zigzag stitch to attach your elastic is that if you need to redo it it's much easier to remove then serger attached. Also, I don't use zigzag to topstitch after I fold the elastic under. If you stretch as you topstitch and make sure your stitches fall on the the folded under elastic the straight stitches will have plenty of give. I think zigzag stitching on the outside of garments look very home made and I do whatever I can to avoid them. Most instructions I've noticed show zigzag topstitching...
Kathy in NM said... (3/18/09 9:31 PM) Reply
Thanks for the additional info. I have a suit cut out waiting to be sewn. I'll try your method on the legs, with a bit more stretch to cover the cheeks, and less in front. Along with exercising the elastic, and stitching only partially on the elastic. This seems to make so much more sense than measuring.
DaisyEsq said... (3/18/09 4:49 PM) Reply
Thank you for your clearly written and informative tip. If at all possible, I would also like to see photos of your next leg elastic project.
Rhoda K said... (3/18/09 4:48 PM) Reply
Your tip definitely makes sense. I read something similar when putting a neck binding on a t-shirt. I'll definitely give this a try. Thanks for sharing.
Sewjourner2134 said... (3/18/09 12:30 PM) Reply
Thanks!! I always have trouble with the elastic on bathing suits. I'm working on another one and want to try this method, but will have to wait til I get home cause I'm at work!!
BrianSews said... (3/18/09 9:28 AM) Reply
I promise next time I sew up some leg elastic I will take photos! That could turn into a full fledged tutorial instead of a simple tip and might be worth a rewrite. For those who already apply elastic in leg openings the the idea is to think about where more cinching/tightness is wanted, and where it's not.
mhk3boys said... (3/18/09 9:07 AM) Reply
Thanks for the advice, I will try this also.
Monique said... (3/18/09 8:26 AM) Reply
Thank you so much for sharing your experience. I would also like to see pictures of your technique.
BrianSews said... (3/17/09 10:25 PM) Reply
Hmm... I think you can still zigzag 1/4" together when you butt it end to end, shorten the stitch length for sure. I might even turn my machine by hand to keep it under control. It's not necessary to have tons of stitching to hold the ends together, infact too many stitches could weaken the ends your joining. Any smaller then 1/4" and I think you'd need to overlap it. I can't profess to lots of experience at smaller then 3/8" however.
SewLil said... (3/17/09 10:06 PM) Reply
Whoops, me too LOL.
SewLil said... (3/17/09 10:04 PM) Reply
I'm going to try it although I will still use the elastic measurements provided in the pattern. My biggest gripe is that lump that's created where the elastic overlaps as well as trying to sew the overlap! How do you do that with 1/4" elastic!! I agree that clear elastic doesn't work for crap on this type of garment. It makes total sense that you would stretch more where you need it, in my case, the butt. Thanks for your tip. I'm working on leotards as we speak. I only have the legs left to do.
christine A said... (3/17/09 8:39 PM) Reply
I am a visual learner. Could you post a picture of each step? Thanks for the wonderful review.
BrianSews said... (3/17/09 8:27 PM) Reply
Good questions! I have found that for legs I like 3/8" polyester elastic. It's cheap, strong, and lasts. You'll see it at Walmart, 6 yards for like $1.25. When I zigzag I allow the needle to zag off the edge so only the left side is catching the elastic. If your elastic is loosing stretch recover then lengthen your stitch and consider a different elastic. This polyester stuff seems to do fine with a lot of stitching and can handle chlorine and the accidental clothes dryer session. Clear swimwear style elastic is not very effective or secure by my standards and is hard to work with, I avoid it. Exercising elastic is essential. You can actually feel and see the difference before and after. Give it a really good abusive pulling for best results.
Kathy in NM said... (3/17/09 8:12 PM) Reply
Helpful hint! What type of elastic do you use? Often elastic seems to stay stretched after stitching with a zigzag, and therefore being too large. Does the "exercising" help with this issue?
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