Cathedral rose afghan

[Dianet]

When you add the 8 pentagons is it suppose to curve

[bgs]

Study the photo that hopefully came with your pattern.  If this is it the photo shows 8 pentagons making a ring  around a circular piece.  I dont have the pattern so this is just  my observation of the photo.  This afghan is round so its going to curve but it should lay flat.

Edited July 12, 2022 by bgs

[bgs]

I checked here under project pages and comments and saw you are joining 8 pentagons to to an octagon to form the ring.  If you arent a member Ravelry is free to join. Some had issues with it not laying flat and made notes on how they fixed it.

Edited July 12, 2022 by bgs

[Granny Square]

Welcome to the 'ville!  I don't have this pattern, but I would hope the pattern would tell you?  It's always a good idea to read thru a pattern before starting it, to make sure you understand how it goes together.

Here is a link to that pattern on Ravelry, at the top click on 'projects' and there is a selection near the top that says 'filter these projects', then 'select filters' and choose 'all helpful projects'.  Often with tricky patterns people will write down 'on row 16, I did this instead of that to make x lie flat' for example, so you might find the solution of your curve problem if it happened to someone else.

I make a lot of things in the round, and dealing with circle geometry is something I run into all the time; I assume by 'curve' you mean something is either cupping or ruffling.  This happens when your stitch height is different from the designers', because there is a specific ratio that must be obeyed for a round thing to lie flat, you know that pi x diameter = circumference and all that.

In general, if your circle is ruffling at the edges, the circumference is too big for the diameter, so you have to either reduce the circumference (remove stitches) or increase the diameter by adding rounds, or by  making taller stitches.

If it is cupping (making a bubble), the diameter is too great for the circumference, so you need to make shorter stitches, remove rounds or add stitches.  

Oops, just as I was about to hit post, Bgs posted the same thing about checking Ravelry projects.  (nice to be playing post tag again Bgs!)

[bgs]

1 hour ago, Granny Square said:

Welcome to the 'ville!  I don't have this pattern, but I would hope the pattern would tell you?  It's always a good idea to read thru a pattern before starting it, to make sure you understand how it goes together.

Here is a link to that pattern on Ravelry, at the top click on 'projects' and there is a selection near the top that says 'filter these projects', then 'select filters' and choose 'all helpful projects'.  Often with tricky patterns people will write down 'on row 16, I did this instead of that to make x lie flat' for example, so you might find the solution of your curve problem if it happened to someone else.

I make a lot of things in the round, and dealing with circle geometry is something I run into all the time; I assume by 'curve' you mean something is either cupping or ruffling.  This happens when your stitch height is different from the designers', because there is a specific ratio that must be obeyed for a round thing to lie flat, you know that pi x diameter = circumference and all that.

In general, if your circle is ruffling at the edges, the circumference is too big for the diameter, so you have to either reduce the circumference (remove stitches) or increase the diameter by adding rounds, or by  making taller stitches.

If it is cupping (making a bubble), the diameter is too great for the circumference, so you need to make shorter stitches, remove rounds or add stitches.  

Oops, just as I was about to hit post, Bgs posted the same thing about checking Ravelry projects.  (nice to be playing post tag again Bgs!)

So glad you are here to explain the math behind it!   This photo shows issues with the pentagon ring then hexagon rings not laying flat.  

Edited July 12, 2022 by bgs

[bgs]

There is a pattern correction that can be downloaded here. More discussion here with references to a cal for the afghan here on Crochetville.  Unfortunately the links back to Crochetville no longer work.

[bgs]

Found the CAL.  Lots to read thru for help.  Go to page 6 and scroll down to read diamonds solution for cupping.