How can I make this bag (quilted on the top with foam) more substanial?
 

This is the second bag I made...the first one will not be seen...lol.
Anyway, the construction was ok but I don't like the way it turned out. I quilted the top with foam and used vinyl on the bottom, and I don't like that the vinyl folds in on the bottom. I used vinyl because I thought it would make the bag a little more substantial. I also don't like the baggy inside. When sewing the lining I used a 5/8 seam allowance instead of 1/4 inch so that the bag may be less baggy and I used a lightweight water-resistant canvas thinking that would add weight. I probably would have been better off using thick fusible fleece.

Would love any suggestions. Thank you!

I would iron heavy-weight interfacing to the back of the main body fabric before quilting it with a really close up and down lines design. Both of those things will give it more strength and stability. I would leave the seam allowance without the interfacing so it will be easier to sew the bag together. Get what I mean?
The fabric itself would drag down the sides using that heavy of a fabric. I see why you chose it though. It is really pretty.

I think once you have put your stuff in this bag, the bottom will fill out. What a beautiful bag!

Have you tried putting things into the bag to see how the lining fits? Bosal foam interfacing is heavier than Soft and Stable. It could be that the heavy fabric is weighing down the interfacing. More quilting will also make a sturdier bag. Did you use the foam interfacing on the vinyl too? If not, the heaviness of the top quilted part may be causing the vinyl to sag. Also, be very careful sewing vinyl. Too short or tight a stitch can cause it to tear when pressure (or in this case, weight from whatever you are putting in the bag) just like the serrated edge on a box of plastic wrap.

I have had the same problem with linings and usually 'dry fit' and tweak the lining before sewing it all together. I have sometimes quilted the foam interfacing to the lining and then made the outer to fit over top. Sort of backwards but it works better for some projects.

It's a beautiful bag and agree with the comments re: stability etc.

It really is a fun summer bag ... do don't beat yourself up with disappointment!

Thinking the same as some of the others ... load it up and see how you feel about it. Sometimes I like the bags that have some give to them, as yours does, rather than being too stand-up-straight-and-sturdy!!

For the linings ... sometimes I get it straight and in place, pinning well, then run a few lines of stitching on the bottom. Around the box base or just straight rows across the bottom or even just one line across the length. It's kind of awkward to squash the bag all down to get it into the sewing machine and then stitch, so that often determines what and how much i do. But this can hold your lining in place a bit better.

Noticed that you do not have pockets in your lining or on the outside. Another way to get a bit more stability would be to quilt the outside and lining all as one sandwich, as you would a quilt. Then stitch it together. Yes, this gives raw side seams ... but you can either stitch it to the outside or inside, then finish with a binding. Likewise, this method would require a binding around the top.