Need some help in calculating please!
 

I need to make some blocks similar to the below - finished size 10 X 16 so unfinished 10-1/2 x 16-1/2. I would like to make these similar to the technique in HST's where you align 2 (right sides together) up, seam diagonally corner to corner 1/4 " on each side of the center of that, then cut on the center line and end up with 2 units. BUT I don't know how to calculate what sizes my initial cuts should be to get the result I need.
Can one of you please help me ? Ultimately I just need to know the dimensions but the formula would be awesome :)
Thanks in advance.

(This is a rough sketch, i know I probably didn't get all my lines in exactly the right spot but I hope you get the idea :) )
[ATTACH=CONFIG]482701[/ATTACH]

I am watching to see the answer as I am also math challenged. my best guess would be to add 7/8 but with that wonky triangle i would bet you have to add more.

I just tried it and it does not work the pieces after sewing look like a kite shape i will try to see if I can take a pic took the pics and as usual can not find them on the computer

Yep Nancy - I just tried the same thing with paper...it does look like a kite lol. drats. but thank you!

I only know of two ways to make that rectangular unit - possible three:

Sew strips together and then cut out the unit.

Sew two triangles together. Be sure to mark the end points of the seams - match them up before sewing -you will have tails sticking out when the triangles are correctly lined up.

Paper piece.

The way you want to do it - you get the kite piece as sewwhat85 just said.

double drats! Thanks bear. I had this idea for a quilt back - i think i'll go for another idea now lol.

Had this same problem a few weeks ago. I gave up on the pattern. I found this while seqrching for a solution.

http://www.quiltdesignnw.com/PDF/HRT_2x4.pdf

tapper, I like your link.

The half square triangle formula won't work because the finished unit is a rectangle. EQ says to cut strips for those patches at 17-1/8" x 10-11/16", then slice in half along the diagonal to create the two right triangles. If you want to construct the block by sewing two rectangles together, I would bump the dimensions up to 17-1/2" x 11" and cut two rectangles that size out of scrap, sew them together, cut down the middle, press and then see how big the unit is. You may need to sliver trim to achieve the 10-1/2" x 16-1/2" unfinished size, or increase the dimensions of your rectangles until you get there.

The link provided contains some great information. I saved it -- just hope I can find it again when I need it!

This is an update to my previous post. After some more head scratching, it seems that creating the half right triangle unit by sewing two rectangles together is not doable. I will try to explain...

In the drawing below, the innermost rectangle represents the finished 10" x 16" block. The next rectangle drawn closely to the first represents dimensions of 10-1/2" x 16-1/2", reflecting the inclusion of the 1/4" seam allowance all the way around.

Already you can see that the angle from the finished rectangle to the rectangle with the seam allowances is not a 45-degree angle. The red rectangle represents what the angle would be if you were to take two oversized rectangles, sew, cut, press and trim. Except trimming is impossible because, again, it's not a 45-degree angle that shoots straight into the corner.

[ATTACH=CONFIG]482734[/ATTACH]
When trimming half square triangles, you can align the 45-degree line of your ruler on the sewn line and trim them because that important guideline is available on the ruler to make it accurate. There is no guideline on our rulers for this one.

It seems that your best bet is to cut rectangles, slice them in half on the diagonal then sew the pairs together on the diagonal. You will be sewing on the bias, but if you handle them carefully, you should be able to control the stretch. If you construct your blocks this way, you may have to mark your 1/4" seam allowances to figure out where your match points are because the fabric pieces will need to be offset for sewing in order to yield a finished rectangle.

You can also paper piece but that might be more difficult since the pieces will be so big.

Hope this helps and is not too confusing.

This article explains the HRT (half rectangle triangle) problem very nicely with several options. http://www.quiltdesignnw.com/PDF/HRT_2x4.pdf

Plan B is in place. Thanls everyone :)

https://www.youtube.com/watch?v=Mr_k8L-pbfA

Deb Tucker makes a lot of great quilting ruler tools. I love the one for squaring up HST's and making flying geese. Here's one to make Square Rectangles. I've not tried it yet, but it looks pretty good to me.

Excellent article.

As far as I can determine, the tools mentioned will only work for rectangles that finish to a 1:2 ratio - that is 1x2, 2x4, 4x8, etc. (the angles with that are approximately: 63.43, 90, and 26.56 degrees)

Your 10 x 16 rectangle is certainly doable. I would draw the 10 x 16 rectangle on whatever it will fit on - divide it diagonally - paste the pieces on heavy paper (or template plastic, if one can get it large enough) - and then add 1/4 inch seam allowances to that.

For a right triangle with 10 and 16 inch legs, the angles will be approximately: 32, 90, and 58 degrees.

A 30,60,90 degree ruler will give a ratio of height of 1.73 (square root of 3, to be exact) to 1
A 45, 45, 90 degree ruler will give a ratio of height of 1 to a width of 1
A Tri Rec ruler will give a ratio of height of 2 to a width of 1

Half SQUARE triangles are just that, they are square. You are getting into the shape of a rectangle. PP would be the best idea especially since they are made from large pieces.

These might help:
http://themodernquiltguild.wordpress...apes-tutorial/

http://thebusybeequiltshop.blogspot....-tutorial.html

LOL! Sorry but that made me laugh. I remember when I discovered this a few years ago. I just sat there stunned that it hadn't worked.:)

I think a lot of us tried that - with a kite as a result!

I'd go with paper piecing personally. But then again, I look at every block pattern to see if I can pp it!

Bonnie Hunter shared this technique on her Facebook page back on July 6. This might be what you need.
http://www.pinterest.com/pin/41869471510873623/

OMG!! That first one from The Modern Quilt Guild is IT!! How simple and easy could it possibly be! No restrictions on size or proportion, nothing. I'm in heaven!! :D

I have a decades old habit of designing quilts before I ever consider how to actually construct them. That MQG link just moved three designs from the 'dream on' file to the 'reality' file! Set them free, just like that. Thank you so much, yngldy, I'll be indebted to you and the MQG forevermore.