Math and DpP questions
 

I've made a couple of disappearing 9 patch quilts, but they were I Spy quilts. So they were just whatever size they turned out to be as kids don't care.

Now, I want to make some to a specific size for lap quilts that our guild makes for nursing homes. The size I need to make is 38" to 40" by 44" to 48".

My brain gets flaky as I start adding up the 1/4 inches. After you sew the basic block, you've lost 12 quarter inches in the seams. So you are losing 1/2" to width and length. So now, if you started with a 15" block, you now have a 14 1/2" block.

If you do the basic cut across the middles, you lose a quarter inch in each direction and now have a 14 1/4" block.

Is that correct? So, if you are doing the basic D9P, no matter the starting size of the block, you are going to end up 3/4 inches less that you started with.

Did I figure that correctly?

bkay

Too much math for me. I'm sure there is a chart showing the finished size of DNP blocks.

I agree with the idea that no matter the starting size of the squares, the "loss" will be the "same" no matter what.

To make it easy on yourself, cut 9 squares .
sew them together, and then measure what you have

Then cut the 9-patch unit apart,
sew the four pieces together, and then measure what you have.

Then remember to subtract 1/2 inch for seam allowances for the "finished size" of the unit.

Without actually going downstairs and checking it out for myself, my guess is that the finished size unit will be two inches "lost" in seam allowances.


Let's try that with nine 5 inch squares.

After sewing them together into the basic 9-patch, it measures 14 x 14 inches. (13.5 x 13.5 inches "finished" size)

After cutting in apart, and sewing the four units together, it measures 13.5 inches (13 inches "finished" size)


Try it with some scrap fabric and see how it turns out.

Leah Day has a chart, but it just uses pre-determined sizes, like crib, twin, full, queen and king.

Thanks, I did figure out that I can't use my 5" accuquilt die.

This may help. https://questioningquilter.com/chart/

An illustration might help.

I used 2-1/2 inch squares because that is what would fit my scanner.

The result is the same no matter what size squares one starts with - 2 inches is used/lost in seam allowances.

I agree with bear. Your finished block will be 2” less than the original cut.

Thanks, I book marked that page.

bk

Thanks, now I just have to decide exactly what size to start with.that's not going to be too fussy to keep accurate.

I was at a sit and sew on Tuesday and stumbled on a great fabric (guild owned), then another for the backing and I already had a purple for the third color. I think it will be a really bright, cheerful lap quilt. It's not quite light where I am, so I'll post a photo later today.

Thanks so much for your help..

bkay

I don't know about the math, but what I do when the quilt body doesn't fit what I need, I add one or more sashings and a border to fill in. Sometimes I'll have more sashings on the top and bottom to make it longer also. Just a thought.