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Sebastien Underwear Set & Swimsuit Sewing Pattern - Boy 3/12Y - Ikatee

Sebastien Underwear Set & Swimsuit Sewing Pattern - Boy 3/12Y - Ikatee

Regular price $28.00 CAD
Regular price Sale price $28.00 CAD
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Underwear set + Swimsuit - Paper Sewing Pattern & Guidebook

Underwear set + swimsuit pattern for boys 

Underwear : tank-top and shorty and a swimsuit boxershorty
Underwear : Ribbing at armholes and neckline, fancy elastic at waistband, gusset at shorty front with full lining and enclosed seams, and dart at gusset. No seam at back, side seams.

Swimsuit : seams at crotches, no side seams, elastic into waistband, full lining 

Sewing level :   easy to intermediate

What you will learn with this sewing pattern:

how to sew ribbing, how to assemble a gusset with lining and enclosed seams, how to sew elastics, how to assemble a full lining at swimsuit.

Age range :   3, 4, 5, 6, 7, 8, 9 10, 11, 12 years

See the size guide

Specificities regarding underwear and swimwear

Underwear and swimwear must be very close to the body (for swimsuit, panties or boxers in particular because they are small parts for which the height is less important than the build and the age of the child ....) it is recommended not to take an age above the real age of the child. For example, as long as a child has not reached 7 years, make small pieces of swimwear and underwear in 6 years. If in doubt, it is better to take the size below than the size above.

Material suggestions: 

Underwear : jersey with or without elastan, ribbing.  
Swimsuit : jersey in polyamide or polyester with lycra (around 20% of lycra). For the lining : use main fabric or special polyester moss crepe

Trims : 

  • basic or fancy elastic 3 to 4 cm wide for underwear short
  • elastic 2 cm wide for the swimwear shorty
  • fully voluminous polyester thread (multi-fibers) and polyester basic thread
  • special needle for jersey and evene microtex needle for swimsuit is better
  • double needle for hems (if you do not have one, it is possible to replace all the points made with a double needle by a zig-zag stitch) - prefer the special needle for jersey 
  • Wonder clips (better than pins for the swimsuit fabric)
  • double training foot for sewing machine

Video Tutorial in free access here

Supplies and trims :

Age 3 4 5 6 7 8 9 10 11 12
Height in cm 98 104 110 116 122 128 134 140 146 152
Fabric 1 in 140cm  Underwear - top 40 45 45 50 50 50 55 55 60 60

Fabric 1 or 2  in 140cm 
Underwear - boxershorts 25 25 25 25 25 25 25 30 30 30
Ribbing (70cm wide)

Underwear - top
15 15 15 15 15 15 15 15 15 15
Elastic Underwear 3-4cm wide 50 52 54 55,5 57 58,5 60 61,5 63 64,5
Fabric 3 - 140cm wide Swimsuit outer fabric 20 20 20 25 25 25 25 25 30 30
If belt in other colour 10 10 10 10 10 10 10 10 10 10
Fabric 3 or 4 - 140cm wide swimsuit lining 20 20 20 25 25 25 25 25 30 30
Elastic 2 to 2,5cm wide 50 52 54 55,5 57 58,5 60 61,5 63 64,5


Use of the ©ikatee sewing pattern:

All ©ikatee sewing pattern are the property of Ikatee SAS or its partners.

Copying parts of the web site or its contents is strictly forbidden and might be considered as forgery.

Using the sewing pattern outside of home use, as well as reselling our sewing patterns or garments made from ©Ikatee sewing patterns is strictly forbidden. 

All designs and patterns are protected. This product is for your personal use only. You are not permitted to share, resell or give this pattern or its content, in any form to anyone else. No material may be reproduced in part or whole. Any commercial and industrial use is strictly prohibited. All rights reserved.

Care Instructions

It is recommended that all of our fabric be washed in cool/cold water, no chlorine bleach or fabric softeners, phosphate free soap,  tumble dry low with like colors or to maximize longevity, line dry.

Thread Colour Matching Service

We offer in house thread colour matching service! CLICK HERE

Simply add the thread of choice to your order 

If you have more than 1 textile in your cart, please make note of which textile you want the thread to match and the warehouse will choose the best suitable thread for your fabric.

Shipping + Ordering




ALL FABRIC  IS SOLD PER HALF METER OR PER HALF YARD INCREMENTS (see listing description for the detailed information) QTY 1 = 1/2 meter or 1/2 yard, QTY 2 = 1 meter or 1 yard ETC.*

When a free shipping promotion is active it will appear under shipping options at check out (subject to change at any time) 



PDF sales are final sale & non-refundable.

Oversized packages: if you order is oversized / large some additional shipping charges may apply - your order wont be shipped until your additional shipping changes have been paid. Thanks!


We are online only - not open to the public!

We offer LOCAL PICKUP in Iroquois, ON - please use code "LOCALPICKUP" at checkout and we will arrange pick up as soon as your order is ready!   


Please contact us at if you have any questions. We try to be a quick as possible in replying within a few hours during the work day.  It might take a bit longer on weekends or the holidays.

 For more detailed information click here


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Sebastien Underwear Set & Swimsuit Sewing Pattern - Boy 3/12Y - Ikatee
Sebastien Underwear Set & Swimsuit Sewing Pattern - Boy 3/12Y - IkateeIKATEE-Seb-3/12
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