Making Squares in
Squares
Using Half Square Triangles
In Lesson #5, you learned how
to make a
Square in a Square by adding small squares to the corners
of a larger block.
This lesson will show you have
you can add continuous squares to a block by using Half Square
Triangles.
Brace Yourself - There will be
math!
Look at the picture on the top
of the page. There is one center square, and it is surrounded
by four half square triangles.
The is another "round" of half
square triangles after that, which you can see in the picture below.
We learned how to construct
Half Square
Triangles in Lesson #3. You learned that you cut a
square on the diagonal to make a half square triangle.
Your
must use half square triangles so that the small sides will be on
the grain. As you can see from the picture the small
sides of the triangle, no matter how many rounds you add, will
always be the outside edges of the block after each round.
What you are going to learn
in this lesson is how to do the math so you know how big to cut the
squares (that you are going to cut on the diagonal).
When you have a 45 degree
triangle (with two equal sides, and one longer side, an isosceles
triangle ),
you can figure out how long the hypotenuse will be if you know the
measurement of one of the smaller sides. The long side will be
the measurement of the small side x 1.4142 inches.
If you know the measurement of
the long side (hypotenuse), you can figure out the measurement of
the smaller side by doing the opposite- dividing the
measurement of the long side by 1.4142.
Since we want our triangle to
fit the square, we already know the measurement of the long
side of the triangle. So we just need to do the math to figure
out the short side.
In addition: We
learned in the
Triangle Lesson that when you join the pieces, you are going to
have to add 3/8 inch for the seam allowance (raw)
So, in determining the square
size, we just do the division, and then add the 3/8 inch to that.
Let's say we are starting with
a 4-inch square. We will divide 4 inches by 1.4142, which
comes out to 2.82. Now we add 3/8 inch (.375).
That comes out to 3.195.
You can round that off to the
nearest 1/4 inch. You may want to round up, since you are
going to have to trim each round anyway. So 3.195 becomes 3.2
or 3.25 which is 3 1/4 inches.
That is the size of the square
you make, and then cut diagonally. You need 4 squares, so you
will have to do it twice.
Now for the trimming:
Once of the easiest ways to trim is with the Triangular shaped Easy
Angle Ruler.
In this picture above, the long
side of the Easy Angle ruler is put on the edge of the fabric
to be trimmed. You want to leave 1/4 inch seam allowance (so
as not to cut off the points). You should be able to see that
in the picture.
On the ruler you will have a
couple diagonal lines that you can match up with the corner of your
square.
Trim by making straight
cut right up the side of the block.
If you don't have the Easy
Angle ruler, you can use any ruler and just line it up with the
straight lines of the block, keeping the 1/4 inch seam allowance.
Here
is another tip that will help you. You sew the triangles
on opposite sides first, and press. It will be easier to sew
on the last two triangles if you trim the first two triangles as
show in the picture. Just cut straight along the edge of the
fabric.
Also, if you can't visually
center the two pieces together, fold them in half and finger press
them, or use an iron. 100% cotton has a memory, and just
finger pressing them will usually leave enough of a mark.
Another reason you want to center the blocks is
so that the triangles are even. If you look at the blue block,
you can see how the points are suppose to line up. See the
horizontal line in the middle of the block? The white color is
the back of the triangles, which have been placed on the blue Batik
fabric.
The
Snail's
Tail Challenge Block has three rounds of squares. If this
lesson was a little hard to understand, see if this page will help.
The Square in a Square Block
has lots of design possibilities. If you practice this block,
and learn the math, you have advanced to the next level!