Thursday, January 28, 2016

Zip A Bag Chapter 10: Diamond-Front Backpack

A very long post today.

But I am very excited to share today's bag with you, because there are TWO zippers in it, with TWO different functions!

Zipper #1 opens and closes the bag itself - and it is exactly the same fully-open installation as we learned in the previous post's pouch (say that fast 10 times).

Zipper #2 separates the carrying strap into two narrower straps, 

allowing the bag to be carried cross-body,

on one shoulder,

or both.

Before we look at the zipper installation, let's talk about the structure of this bag, so you'll know how to draft and cut the necessary fabric pieces for it.

First of all, it's a bucket-style bag. This means you'll need 
  • a base - mine was a rounded rectangle. 
  • a rectangle for the body, which is sewn into a cylinder. The height of the rectangle is the height of the bag. The width of the rectangle is the perimeter of the base. 

Repeat these two shapes in the lining layer. I pieced two fabrics together in the body rectangle of mine - the coordinating grey upper band to face the zipper, and the contrasting yellow lower band. I also added two pockets for functionality: a large patch pocket on the front face,

and a zippered welt pocket on the back face.

For the outer bag layer, I used a light grey vinyl and Jessica Jones' Navy Loop Timewarp barkcloth by Cloud9 Fabrics. That same vinyl is used for the straps.

Finally, I used two zippers for the bag - one for the strap (20") and a separating zipper for the top opening (the zipper's length is a little over half the width of the body rectangle.) A third zipper was used for the internal welt pocket.

STAGE 1: Visualize
I cannot say enough about the importance of visualizing in sewing.

I suspect lots of folks don't enjoy visualizing. They'd much prefer the thrill of going "blind" into someone else's pattern, dutifully following instructions and then being elated when they successfully arrive at the finished product. I can totally understand - it's extremely exciting, and a bit like magic, going from Step 1 to Step 2 to Step 3 to . . . Step 96, and suddenly, they've got An Awesome Bag or An Amazing Dress.

However, I also suspect that there are those among us who have been intimidated by a pattern that seemed difficult, and which they therefore passed over, because they couldn't imagine how they in particular could get from Step 1 to Step 96 and produce That Bag or That Dress. That Bag or That Dress, they reasoned, seemed way beyond what they'd ever made, way beyond their skill level, way beyond anything in the realm of the familiar.


If they would but visualize, they could make anything.
Because while the end product may not be familiar, visualizing helps you to get from Here to There along pathways that are. 

Okay, let's conduct an experiment.

This bag

is the same as this pouch

but with straps.

You don't believe me.

I shall attempt to prove it to you by visualizing.

First, visualize this pouch much taller.

Now imagine its base turned 90 degrees, so that its longer axis is perpendicular to the zipper.

Now imagine that fabric tab extended into a carrying strap

that inserts into the base seam of the bag.

And finally, imagine the front part of the pouch folded downward so the zipper pull almost touches the base seam.


I rest my case.

STAGE 2: Install the main zipper
Remember that this zipper is a fully-open-style zipper, which you can now install in your sleep.


The green arrows show the head end of the zipper. In the pouch, we curved the head ends of the zipper tape into the SA (blue circle), one side at a time.,

and then brought them together when we sewed the side seam.

In today's bag, we're going to curve both sides of the zipper tape at the same time, with their heads together at the midline of the body. 
In the photo below, there is a long, straight strip of vinyl grey that will form the top edge of the bag opening. I bent it to fit into the photo frame, but in subsequent photos, you'll see it straightened out. In the middle of the strip, curve/fold the heads of the zipper tape into the SA, as shown. The heads themselves will not touch - there is a space of about 1/2" between them, to prevent bunching at the meeting point when the zipper is closed. Baste the zipper tapes to one long edge of the vinyl strip.

Now with RS together, baste the other edge of the vinyl strip to the top edge of the fabric body.

Flip the vinyl strip up and edge-stitch on its RS to secure in place.

We'll next need to face that zipper with the lining fabric. 

This is the big-picture sequence:
  1. sew the side seams of the outer body to create a cylinder. Do the same for the lining body. Then
  2. sew the lining and outer cylinders together around their top openings, facing the zipper in the process. 

Side notes:
  • See those two upside-down zipper tapes? When you face them with the lining fabric, their SA will get tucked into the seam and the zipper coils will flip upward. 
  • See those metal stops? They are not cool. Normally, if I'd had a long enough zipper, I'd have tucked the head ends of the zipper tape into the seam, including the bits with the metal stops. Unfortunately, this zipper was barely long enough for the opening, so I had to use every last mm of it and let the stops peek out. Boo. Hiss.

Returning now to the construction sequence: 

(i)   Make an outer cylinder.

(ii)  Make a lining cylinder.

(iii) Turn one cylinder WS out and the other RS out. 

(iv) Insert the latter into the former so their RS are in contact. 

(v) Stitch their upper circumferences together, sandwiching the zipper tape between them, and facing the zipper in the process. Because you sewed the side seams of each cylinder separately, their ugly raw SA will now be hidden away between the cylinder layers. Yay.

(vi) Turn the entire double-layered cylinder RS out and edge-stitch around the opening. 

STAGE 3: Attach the base
Turn the half-finished bag WS out again. Working first with the outer layer:

(i)  Attach the outer base to the bottom opening of the outer cylinder, being careful to push the lining cylinder out of the way. I added piping to mine. 

 (ii)  Insert two buckle anchors into the base seam, for the straps to lock into.

(iii)  Sew the lining base to the lining cylinder, pushing the outer fabric layers out of the way. Leave a gap for turning the entire bag RS out later. 
You will now have two individual completed bags, connected only around their main opening.

(iv)  Turn the entire bag RS out through the seam gap and hand-stitch the gap shut. 

STAGE 4: Make the strap
Warning: the how-tos in this stage are going to look a bit skimpy, only because we'll be revising this strap again in detail in the next post.

We're essentially going to sew a strap around each side of the zipper tape, and then when the zipper unzips, you'll get two separate straps. 

So take two strips of fabric 

sandwich one side of the zipper tape between their RS, 

and sew.

Fold the fabric strips RS out and finish their other long edges by tucking in their SA to the WS and edge-stitching. Then repeat with two new fabric strips on the other side of the zipper tape. If that made no sense to you at all, fear not - the next tutorial will bring you through those steps in photos.

Anyway, the finished outcome will be one narrow strap on either side of the zipper coils, as shown. 

I am more interested today to bring your attention to the bit where the zipper pull rests at the end of the coils.

The straps join only partway along their length, so that even when zipped together, their ends are separated into two base anchors 

for its backpack strap configuration.

and when completely unzipped, separates fully into two individual straps.

The head ends of the zipper tape must therefore be curved into the SA of the fabric straps the same way that the main (dark blue) zipper's curved into the SA of the bag opening.

STAGE 5: Attach the strap
Zip up the bag opening and fold it into a diamond shape as shown. The strap will attach to the tail end of the zipper through a collar.

The collar is just a cylinder which fits snugly over the end of the strap. We'll sew the collar to the strap first, then attach the other end of the collar to the bag.

Make a tube and fit it WS out over the tail end of the zipper. I pulled my collar low enough for the stitches to avoid the chunky retainer box. Sew through all layers, then flip the collar RS out over the end of the strap.

Now insert the other end over the tail end of the bag zipper. Tuck in the collar's SA to its WS,

and edge-stitch to secure in place. 

This is what the finished collar looks like.

Here's an additional feature I added - an oversize pull tab

with a magnetic snap.

If you want to include this in your bag, you will need to install the magnetic snap while you can still freely manipulate just the outer layer without getting tangled in the lining layer i.e. before sewing the lining base to the lining cylinder in Stage 3.

Otherwise, here's another variation I found on Pinterest - it uses a snap hook whose anchor is sewn into the base seam. 

Finally, here is the finished bag.

I punched holes in the free ends of the straps for adjusting their lengths through the fixed buckles anchored to the base. 

So there - a diamond-front backpack which is really just your oversized fully-open pouch with a strap.

Not as difficult as it looked, right? 


  1. Well... what looks so complicated really isn't, is it? :) Love it!

  2. You do such beautiful work. What kind of machine do you use?

  3. Thank you for this instruktion. It looks very good. It is challenge.

  4. Amazing!
    I love all your tutorials!
    Thank you so much for sharing!

  5. This was so much more straightforward than I expected. There are a couple of things that I've been wondering about. I know you don't have an industrial sewing machine and I'm curious how you get your machine to sew across two layers of vinyl, two layers of piping fabric, and the strap anchor at that base seam allowance. My machine has struggled sewing through a strap and two layers of home dec fabric, and it's a good quality, metal frame/body Janome. The other thing I'd love to know more about is how you hold the folded in seam allowance on each strap when you are topstitching them together (like on the ends of the straps that buckle into the strap anchors). Every time I do this, my edges wobble around and never line up perfectly to look neat and professional. I presume you can't press the fold into vinyl, like you can with fabric. Do you just have the magic touch, or is there some nifty technique?

  6. Wow such a gorgeous bag, it seems so simple when you explain it like that (but I'm sure it won't be that easy when it comes to sewing time LOL!).

  7. Thank you so much for explaining the different types of zippered bags. Your tutorials are clear and easy to follow. I have read many bag making books, but your tutorials are always better! I can't wait to make this convertible back pack.

    I response to Katie M's question about how to keep the seam allowance together while topstitching, I usually cheat and use double sided wonder tape to hold the fabric in place:

    Also, you might try a different needle if your machine is struggling to get through the many layers. I often use a 100/16 leather or topstitching needle to get through several layers of thick canvas, vinyl, etc. Increasing the stitch length helps as well.

    1. Thans SalsaStarr. These are helpful tips. I have Wonder Tape, but I need to get some leather/topstitching needles.

    2. Katie: See the next post for needles. Also try the jeans/denim needle for canvas. I have used topstitching needles, but they are better for literally topstitching with thick thread on thinner layers/materials because their shafts are not as thick as denim. To topstitch on denim or vinyl, for instance, I don't use a topstitching needle - I use a denim or leather needle, resp. In other words, use the needle for the fabric (denim/leather), not the function (topstitching) when dealing with bulk and layers.

  8. Olá, você é muito talentosa, queria muito fazer uma, mais não sei em que ,medidas colocar.. Você poderia por gentileza me dar dicas das medidas em que você utilizou pra faze-lá, ficou extremamente perfeita. Parabéns!!!!! Desde já agradeço sua resposta. <3


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