Flat Hat

albert's picture

I am working on a hat while waiting for my yarn delivery from Knitpicks. I would like it to have a flat top. I know this has come up in the past here, so can anyone advise me on how to do the flat top? Thanks, folks.

Comments

Basic Geometry to the

Basic Geometry to the Rescue!

It has to do with your gauge and the formula for the
circumference of a circle:

Circumference = Pi times Diameter

If you want a hat that's 22 inches in circumference,
the diameter will be 7 inches (and the radius will be
3.5 inches).

If you think of the top of the hat as a series of
concentric circles, you can calculate how many stitches
you need in each circle (row) to keep the hat flat.

I usually knit hats from the top down using two circular
needles or the magic loop method, and start with 12 stitches
that are single crocheted through a slip knot. Elizabeth
Zimmerman refers to this technique as "Emily Ockers Cast-on"

I also usually put my increases in every other row.

Each Row contributes twice the row gauge to the diameter
(or you can think of the radius of the circle growing by
the row gauge on each round).

Let's assume you have a stitch gauge of 5 stitches per inch
and a row gauge of 7 stitches per inch. You're going to have
to knit 25 rows to get the desired circumference.

The 12 starting stitches represent 3 rows, (the slip knot
being the first row).

Let a small "O" represent the slip knot, and parentheses
the circular row.

So you're here: (o)

If you knit all around you're here: ((o))

The question now is, how many stitches do I need for the
next row to keep the hat flat? Since we're only increasing
in every other row, let's calculate the circumference based
on the rows in which we do not increase:

The next (increase) row is represented by (((o)))
and the row that we will calculate is represented by ((((o))))
or 9 rows.

If we use a value of 22/7 for pi, and the formula referenced
above, we get:

22/7 times 9/7

Pi times 9 rows times 1/7 inch per row or
4.04 inches. Multiply this by 5 stitches per inch and
you get 20 stitches, so you would increase 8 stitches evenly.

The next increase row would be

pi times 11/7 or 4.93 inches, 24.69 (call it 25) stitches
so you would increase 5 stitches evenly.

The next increase row would be
pi times 13/7 or 5.83 inches, 29.18 (call it 29) stitches
so you would increase 4 stitches evenly.

For the following increase rows:

pi * 15/7 = 6.73 inches, 33.67 stitches (34): increase 5
pi * 17/7 = 7.63 inches, 38.16 stitches (38): increase 4
pi * 19/7 = 8.53 inches, 42.65 stitches (43): increase 5

pi * 21/7 = 9.43 inches, 47.14 stitches (47): increase 4
pi * 23/7 = 10.32 inches, 51.63 stitches (52): increase 5
pi * 25/7 = 11.22 inches, 56.12 stitches (56): increase 4
pi * 27/7 = 12.12 inches, 60.61 stitches (61): increase 5
pi * 29/7 = 13.02 inches, 65.10 stitches (65): increase 4

pi * 31/7 = 13.91 inches, 69.59 stitches (70): increase 5
pi * 33/7 = 14.81 inches, 74.08 stitches (74): increase 4
pi * 35/7 = 15.71 inches, 78.57 stitches (79): increase 5
pi * 37/7 = 16.61 inches, 83.06 stitches (83): increase 4
pi * 39/7 = 17.51 inches, 87.55 stitches (88): increase 5

pi * 41/7 = 18.41 inches, 92.04 stitches (92): increase 4
pi * 43/7 = 19.30 inches, 96.53 stitches (97): increase 5
pi * 45/7 = 20.20 inches, 101.02 stitches (101): increase 4
pi * 47/7 = 21.10 inches, 105.51 stitches (106): increase 5
pi * 49/7 = 22.00 inches, 110.00 stitches (110): increase 4

At this point you've reached your desired circumference and
can knit the rise.

Notice the regular pattern in the increases.

BuduR's picture

my head just exploded.

my head just exploded. *wanders off to take more nyquil*
MWK's Token Estrogen-American

Really, it's not rocket

Really, it's not rocket science, just arithmetic!

scenter's picture

Relax, it's not the first

Relax, it's not the first time her head exploded over math, she recovers well. It is a mind expanding experience :-)

BuduR's picture

hahahaha, so true! And to

hahahaha, so true! And to think, in school math was my best subject. I loved math so much that I even minored in Accounting. (Monty Pythons "Lion Tamer" skit is sooooo true accounting makes you dull dull dull)
MWK's Token Estrogen-American

BuduR's picture

hahah most days I have to

hahah most days I have to use my row counter to figure out if school is delayed by 2 hours what time I have to get the kids there!
MWK's Token Estrogen-American

Tallguy's picture

Yes, looped, that is a very

Yes, looped, that is a very comprehensive and clear explanation of how it works. It’s a lot more math than many knitters want to deal with, but allows one to explore variations on a theme here.

EZ says to increase 4 stitches EVERY round, or 8 stitches every OTHER round. In garter stitch, this would work very well. But I find that in stocking stitch, it’s not quite accurate because of the different gauge (that word again). So you have to do a correction frequently to compensate for the slight difference – hence the alternating 4-5 increases would work really well.

There is a KAL hosted by the Pandaman in which he takes the garter stitch Baby Surprise Jacket developed by EZ and doing it in stocking stitch. So there is a little math and compensating stitches necessary to make it work this way and still lay flat. It’s fun to try something a little different from the routine!

purlyman's picture

Hi Albert, There's a very

Hi Albert,

There's a very fun and interesting 6-triangle flat top that you could try. You can see what it looks like at http://www.menwhoknit.com/community/?q=node/3550. Let me know if you want the pattern. The other way to do it is to divide what you have into 10 even sections (so if you have 90 stitches on your needle, you'll have 10 sections of 9 stitches each), and then decrease on stitch per section every other round. Once you decrease down to 10 stitches, don't go around again and just thread the yarn through the 10 stitches and pull it shut! I've used that a lot recently. Works well. There are surely other ways to do it too! Good luck!

Frank.