Technique questions for making gas tank (top tube bag)

[ljracer]

Hi there!

I just started trying to make my own gas tank bags.  I've made a few now and was hoping for some advice on construction techniques.  In general all the straight lines are easy!  I'm finding I'm having lots of trouble sewing the corners and especially with side panel stiffeners in place.

Does anyone have any recommended order of operations about which panels to do and how to put together?  I'm generally sewing them inside out but find I have to do/ and redo the corners a lot to try and get them to come out even.

Attached is one of my better ones.  I know I could go buy one; but I like making stuff.  I've been mostly using XPAC outer and silnylon inner.

thanks in advance for any feedback/input.

[brankulo]

it takes a little practice, to get the corners and curves right. side panel stiffeners go in last after everything is sewn together.

[Smo]

I make a sleeve for the side stiffeners to go into, then put them in when the bag is complete (and turned right-side-out).

Sewing curves will be easier if you use a smaller seam allowance - I use 1/4" for small bags with curves.

[ljracer]

Thanks for the responses!

[LittleOldLady]

I'm not a bike bag expert, but I've sewn for years and have some experience in making other types of bags.   It takes a bit of fiddling to get the corners right.  When working with heavy material I usually sew up to the corner, back stitch,and cut the thread.  Then I turn the bag, rearrange the layers and put the needle down at where the next side starts at the corner just sewn.  Then I tack the thread and sew the next side.  This usually gives me a nice corner.  I use a very light weight batting rather than stiffeners.  I suspect the weight is about the same and I like working with it better and the stability of the bag is excellent. 
And I understand liking to make your own stuff!