Tuesday, June 12, 2012

Asha's Sawtooth Star Quilt: Part 3 - Piecing the Sawtooth Star Blocks

These are my Calculations:

The seam allowance calcs are the same as in the previous post:

    a+ = a*SQRT(2) + a
    a = .25 inch

Patch B is exactly the same dimensions as in the Double Snowball block:  half triangles made from a square of 2 7/8 inches.  Cut 4 squares (8 triangles) per block.

Patch D is a 4 1/2 inch square - 1 per block.

Patch E is a 5 3/16 inch square cut into 4 quarter triangles - 1 square (4 triangles) per block.  These need to be quarter triangles instead of half triangles because the grain edge will be the outside of the block.  It also keeps any printed pattern oriented correctly.

Patch F - These are the 2 1/2 inch squares in the corners that I forgot to label in my calcs;  cut 4 of these per block.

TIP:  Trim the Corners

I find that it makes it easier to align my triangular pieces if I trim the corners off:

For Patch B, Trim the corners perpendicular to the legs of the triangle at 2 1/2 inches.  This makes it easier to align  with Patch F.

For Patch E, trim the corners perpendicular to the hypotenuse such that the hypotenuse is 4 1/2 inches with the point of the right triangle lined up at the 2 1/4 inch midpoint.  Then trim the point of the right triangle parallel to the hypotenuse at 2 1/2 inches:

Another general benefit from trimming the corners off triangles is that since they are trimmed on grain, it's more easy to distinguish visually half triangles from quarter triangles:

Since there is inevitably some slop with cutting, the trimmed corners really help spot and compensate for these variances:

Assembly Order:

The first step is to assemble the Flying Geese units.  Flying Geese is the name given to the frequently occurring set of patches where the hypotenuses of two half triangles are attached to the legs of a larger quarter triangle (note:  this is a bias-to-bias seam) to create a rectangle.

There are a couple tricks and shortcuts for making Flying Geese units (described very well at The Quilter's Cache), none of which I was aware when I made this quilt.  So I just chain pieced them one at a time like any other patch.

I like to chain piece 2 blocks at at time so that I can leave one on the sewing machine while I press and assemble the next set.

 After the flying geese blocks are assembled, the next step is to attach them into the three strips of the block:

I like to press all my seams open initially, even when I intend to press them one direction or another later.  I think this helps prevent the problem of folded seams (this may be superstition on my part).

Before the next step of sewing the strips together, it is really helpful to press the seams in opposite directions where the corners are going to meet.  The general rule is to press into the darker fabric to minimize see-through.

This helps line up the intersection and hold it in place without pins.  (my pinning skills are so bad that I find that patches I've pinned have less likelihood of lining up correctly than the random chance of unpinned patches).

TIP: The Four-Patch Trick

I learned this handy trick when I was assembling the four-patch units in middle of the snail's trail blocks of my first quilt.

When you have four patches coming together at a point. push the topmost seam in opposite directions. Break the stitch or two that's holding them together with your seam-ripper.

Then press the seams in down in all four directions.  This trick noticeably flattens the bump caused by the excess fabric.

Note that in this example, I pressed in a counter clockwise direction.  To press in the other direction would have required removing more stitches (from the two other seams).  This is not plan A, but I've done it, and it doesn't seem to negatively affect the integrity of the seams, especially if I'm quilting through that point later.

Also, if see-through is a bigger consideration than block flatness, you might decide to press into the darker fabric, even if it means not doing the four-patch trick.

Another thing to consider with pressing this block is whether you plan on quilting along the seams (stitch in the ditch).  If so, leaving any seams pressed open would be inadvisable.

< Part 2

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