Finding straight on raw fabric

[jbo_c]

I'm about to start work on my third DIY hammock and want to do a little more professional job than on my previous two. For my first 'upgrade' I wanted to make sure the edges are square when I start(I know. But it has to do with mindset.). I trimmed across the fabric using one of the ripstop pieces as a guide thinking this would be the best idea, but it's the crookedest looking thing I've ever seen.

How do you make sure you are square to the edges of the fabric?

Jbo

[Ramblinrev]

This is a more complicated question than you think it is.

You need to be concerned about two (2) aspects. One is the line perpendicular to the selvage (the finished edge running the long way of the fabric.) Each full width has two selvages, one on each side. The second dynamic you need to pay attention to is the "grain" of the fabric. The grain is the straight lines the threads make when they are woven. The two rarely match up. It happens on occasion but rarely.

Here's the difference it makes. Tension in the direction of the threads is a stable tension. At least for the most part. Tension which pulls the threads askew is called bias tension. It is not stable. If you assume the perpendicular line to the selvage is the "straight" you will almost inevitably end up with the end cut on the bias and the fabric is be stretchy and hard to work with. Unless of course you want the fabric bias cut.

So... to answer your question having given you TMI. Most patterns have you line up the grain of the fabric. If you want a good solid stable piece the grain is what is improtant. A rolled hem will be easier to sew if you follow the grain because that's the way the fabric wants to go. If the end is cut on the bias, the roll will want to pucker and pull and you will be fighting the fabric.

Now to complicate things even more... trying to follow the ripstop across is very difficult to do precisely because the threads of the fabric will wriggle and squirm while being woven and cut.

The general rule of thumb _I_ use is this. If I am cutting out all the edges of the a pattern piece I say phooey on trying to make the piece square. If I am using the end as an edge of the piece then I will notch the selvage and rip the fabric across the width. That follows the width of the grain. If you _really_ want the fabric to be square in form and grain then you need to block the fabric. Talk about a PITA!!! Particularly with a large hammock sized piece.

Edit: another way of cutting on the grain is to use VERY SHARP scissors and open them to a small "V". Using the "V" slide the scissors thorugh the fabric. (don't cut... no up and down). That will follow the grain without leaving the collateral damage that ripping the fabric does. But the scissors ahve to be SHARP!

In short... The grain is probably what you want to follow rather than the perpendicular if that makes sense.

[warbonnetguy]

use a carpenter's square and a straight edge

[Ramblinrev]

Yeah... just skip my dissertation and do that..

[Frawg]

Yeah... just skip my dissertation and do that..

I thought your dissertation was pretty instructive -- even saved it in my "sewing" folder for reference.

I use a drywall T-square, btw. Has the square and a nice 4 foot straight edge.

[Ramblinrev]

I thought your dissertation was pretty instructive -- even saved it in my "sewing" folder for reference.

If one simply wants 4 yards of fabric and the grain on the ends don't matter (which is where I would put the vast majority of the projects most DIY folks do) then I think a square is fine. After all that's essentially how the fabric shop does it. I am still apt to simply rip the fabric because if the end grain is not really all that critical then the perpendicular is not really all that critical and I don't have the space to lay out the fabric and a square. On the rare occasion where the end grain IS critical then I end up trying to zip it with my pitifully dull scissors. But those instances are very rare

[Spock]

Aother way to square your fabric before cutting is to use a straight edge and chalk to follow a ripstop line across the fabric from selvage to selvage, then pin one selvage straight (on a cutting board or some suitable surface). Then use a square or just the old 3-4-5 ratio to establish the true perpendicular to the selvage beginning where your chalk line starts on the pinned selvage. Then, just pull the fabric gently from one corner opposite the pinned selvage until the chalked line is true to the square you determined. Then immediately lay out your pattern and cut. Otherwise it will get out of true again just from handling. This works only on uncoated fabric. If coated fabric is not true, there is nothing you can do.

[Merganser]

I've tried doing this just eyeballing the ripstop lines and squaring it up. I always wind up cussing about how hard it is to follow those lines. Highlighting one should have been an obvious solution. That's what I'll be doing next time... Go Spock!

[Ramblinrev]

I've tried doing this just eyeballing the ripstop lines and squaring it up. I always wind up cussing about how hard it is to follow those lines. Highlighting one should have been an obvious solution. That's what I'll be doing next time... Go Spock!

You are still likely to find the ripstop lines do not run perpendicular to the selvage. For the vast majority of projects it probably doesn't matter.