Sewing Round-Bottomed Stuff-Sacs

[Nomad]

Made a stuff-sac a while back, originally for a 12cm Zebra, but ended up being used for water bottle and nesting cup. It's made from thickish cotton canvas (black, for blacking out darkrooms, as it happens), and I made it with a round bottom so that it would be a better fit around the billy/bottle.

I found that doing the round bit at the bottom was a real pain. I had almost got to the end and found that one layer was 'longer' than the other, resulting in excess material. Had to unpick it all and try again, and still found it pretty awkward. I tried sewing it freehand on the machine with pins to keep the bits aligned, and with contrasting thread hand sewn in long stitches to hold the bits together while machine sewing.

It's evidently some issue with the diameter being fixed by the vertical part of the main body of the pouch, and trying to get the round bit positioned so that the right diameter is sewn into on that. In my first attempt, I got the path of the stitching wrong on the round bit, resulting in that ending up a smaller diameter and leaving excess material on the main part.

Is there a trick or a knack to making these, or is it just a case of making a few duffers until it starts to work?

 

[John Fenna]

I make square bottomed stuff sacks and pouches....

 

[Philster]

I have similar issues as you - there's always a bit of one piece "extra" as you reach the end! It annoys me but doesn't seem that noticeable in use.

 

[tombear]

I sew the bottom seam first and then the side seam after trimming off the excess I deliberately built into the pattern. It's a bit wasteful but I was sick of there being a gap, or puckering. Start sewing round the after whatever seam allowance you want. I tend to flat fell or roll the seams to make them stronger and less prone to fraying.

atb

Tom

 

[Toddy]

Pins. Trust me, pins are a good thing.

Seriously though. Sew the side seam and finish making the tube. Then mark (scrap of soap, a pin, a pen mark) where the half way sides lie, then do the quarters and then the eights. Just fold the tube flat for the first two, then match those to give the quarters. The eighths lie evenly between those four marks.
Now do the same with your base(s).
Then match the marks up and pin them in place; halves, quarters, eighths. (if it's awfully big, go to sixteenths too)

You ought to be able to see then whether your base is too wide or too skimpy and adjust accordingly.
Hopefully it'll be neither and the sewing will work it's way around neatly

If you're still a bit uncertain, then once it's pinned just run a tacking thread around and ease things as you go.

cheers,
Toddy

 

[petrochemicals]

As mary says pins are you best friend, also use a currved surface, suck as an ikea cutlery drainer, or rolling pin makes the two curved surfaces lay more flatly, it isn't the part you are working on but the fact that the material infront and behind is being made to lay flat when it doesn't wish too!

 

[bilmo-p5]

Pins or these.

Square bottom bags are probably easiest. Octagonal or hex bottoms are also easier sewing

 

[twyforge]

In making stuffsacks for both my DIY hammock and hobo stove kit from rip-stop, I came across no problems by having carefully calculated exactly how much material was needed for the side walls using 2πr. If you make that calculation and then add seam allowance I find it all comes together fine if you pin and sew using the guide on the sewing machine table.

 

[Zingmo]

Pins or these.

Square bottom bags are probably easiest. Octagonal or hex bottoms are also easier sewing

That's a top tip about using clips. And a really neat little tutorial. Thanks for that.

My approach was to just eyeball all the cutting without measuring anything. Then have a jolly little laugh as the base proved to be too big. Then unpick it all muttering that it's all good practice. Try again this time with measuring and mathematics to calculate how big to cut the base. Sew it all but this time finish the seam with a Victor Meldrew impersonation. Unpick again listening to wifey going on about seam allowances. Look at clock and think "this was supposed to be a quick job". Pick an item of crockery to draw round that looks much smaller than you need and cut the base a third time. Sew it together. This time you need some really special words when you find you are short by 3mm! Allow your belligerent nature to take over and unpick a third time while wondering if somehow this canvas is possessed. Then finally sew it up giving a primordial roar of victory as you turn it inside out.

I just need to find something that fits in it now!



Note to self - get pins.

Z

 

[Zingmo]

Here it is...



Z

 

[neilwragg]

I agree, if you use (2πr) 2 x pi x radius and a circular cutter to get the base, factor in a, for example 1cm seam, and it will magically fit your tube.
I make bags for stoves and Kelly kettles etc from leather and canvas and after a few you will have it dialled!

 

[Toddy]

Thing with leather though is that though it can stretch, it doesn't do it the way the bias cut on fabric does.
If you cut a circle from fabric then it's all on some kind of bias right round it's edge.
That's why marking and matching points works. Doesn't matter whether you pin or clip or tack, you need something to hold the straight edge agin the curved at regular points. Otherwise, especially when using a machine, fabric creep sets in and all your careful measurement eases out of true.

M

 

[tombear]

Oh yeah, I should have mentioned I only hand sew, quite small back stitches with a double stitch every inch or so with the thickest thread that will serve. I got a huge roll of 1mm 100% linen cheap off eBay that works for most things, can be easily waxed for leather. And yes, copious amounts of glass bead headed pins, normal ones are too fiddly for my sausage fingers. One of the boys who is particularly cack handed uses modellers T shaped pins if I don't spot him ( good ones are hard to find, cheap ones bend as soon as you push them into MDF).

Synthetics get singed to seal them to stop fraying. If I'm in a hurry the seam allowance is then rolled up and whip stitched through the original line of stitching, doubling every inch of so. Otherwise I flat fell the seam or fold both sides in towards each other and whip or use running stitch to hold them together. You could tape the seams, bias binding is cheap in most charity shops and I've ended up with a stash if it, but I hardly ever do.

ATB

Tom

PS. And please make sure the material is pre shrunk before you sew it, some doesn't need it of course, some already has been but if its not then you may get a nasty surprise when you wash it the first time . Sorry to those who already know how to suck duck eggs...

 

[Nomad]

Thanks for all the responses, folks. Next time I get the urge to make something, I think I'll try the square bottom method - easy sewing (in straight lines) is something that appeals to me.

And I'll no doubt return to the round bottom type at some point - I get the feeling I was on the right track, but that my technique needs to improve.

 

[Seagull]

The use of marking points, is the best option. Edge turnover really needs to be minimal for things like heavy canvas.
Pinning is used by those with an awful lot more patience than myself. A large span Office stapler is my preferred means of laying-in the tackings.
Ceeg