In the meantime, I found one of my son's old sleeping bags in the wardrobe yesterday and remembered making one for him a couple of years ago. He was so wedded to his sleeping bags that he wanted to continue using one despite having grown out of the 18months to 3 years version. You can get these bags for age 3 to 6 years, which is the next size up but these are hard to find and harder still to finance. I found a couple of winter-weight ones in an NCT sale and used these as a template for a nice light summer one for him. Which he only used twice but that's another story.
Anyway, if you'd like to save some money by making your own third-size sleeping bags and if you are a slightly-more-than-novice seamstress, then here's what I did:
I drew around the original bag on a piece of wallpaper. You won't need to do this because I have made a rough template for you which you can transfer onto wallpaper using the measurements given. I haven't included seam allowances and the measurements don't have to be completely exact - this is a sleeping bag, not a couture jacket! It is probably easiest to draw the centre back/front line first (118cm) and then draw the rest around that line. I've put both the back and front necklines on the same pattern but you will want to make the back pattern first, then copy it onto another piece of wallpaper (I just cut out the template and drew around it - like I said, it doesn't have to be exact to the millimetre). The measurements are not hugely clear from the pictures so I shall list them at the end of this post.
You now have two paper patterns, neither of which has any seam allowances.
To make the sleeping bag I used one old flannelette sheet for the inner layer (in US terminology, a flannel sheet) and an even older cotton one for the outer layer. By using old sheets you are not only recycling, you are also removing the need to pre-wash and pre-shrink your fabrics (generally a must-do when you are sewing two different fabrics together). For winter-wear, you can use terry towelling for the inner layer, or even have two cotton sheets sandwiching a layer of batting.
Cut out the back first. Fold the fabric in half lengthwise and iron it. Then carefully place the pattern with the long straight centre-back line on the fold. If using scissors to cut out, pin the pattern in place. If using a rotary cutter, you only need to hold it in place with pattern weights or coins. The next picture shows the cutting lines in pink. You don't need to leave a seam allowance on the necklines or armholes. Obviously there is no seam allowance along the fold
For the front, you place the long straight centre-front line along the grain of the fabric. When you cut out this piece you need to leave a seam allowance of about 3cm along the centre-front line. This is so you can insert a zipper. By cutting on the folded fabric, you get the two pieces you need to form the front.
I first attached the zipper to left and right fronts of the bag outer using the centred zipper technique, before seaming down from the zipper to join the outer left and right fronts. I then seamed the same length on the inner left and right fronts and pressed the seam open, right up to the neckline - this was so that I could sew the inner to the zip later on.
Then I assembled the inner and outer bags separately by joining the shoulder seams and then the side and bottom seams in one operation. Do this for both bags. I didn't bother top-stitching the seams because time was very short, but I did press them. I then put the two bags together, with the wrong sides facing each other. I cut some binding for the armholes and the neckline simply because I never have bias-binding around when I need it. I attached the binding going from front to back and then I handstitched the inner to the zipper. The original bag had a small length of elastic sewn to the inner about 12cm under the armholes to gather the bag in around the child's waist. My son wasn't keen on this so I omitted it from my version. I can see, however, that the bag would be warmer with the addition of the elastic so I leave that one up to you. If you do want to add it, cut two strips about 10-12 cm long, centre them across the side seams and attach using a 3-step zigzag.
To pretty it up I cut out some Thomas the Tank Engine motifs from some quilting cotton in the stash and appliqued them onto the bag. This is what I generally do when I am anxious that my son will like something I've made for him.
Measurements (these are all for ONE HALF of the back or front of the bag!)
Bag length - 118cm; width at bottom - 28cm; armscye - 18.5; shoulder seam - 11.5cm; neckline width at top - 6cm; neckline drops 1.75cm at the centre back; front neckline drops 11cm from back neckline to bottom of v.
Any problems or suggested improvements, just email me or leave a comment.