I am working on a sofa and chair for a customer. Right now, there are semi attached 'flap' looking cushions on the back and on the arms. The customer wants to change this to just a tight back look, and get rid of the flap on the arms as well. I havent' really built up the foam from scratch before-normally just use existing as pattern/or idea of where to go from there. Do I just get a regular sheet of foam and cover it (after removing existing foam? Do I need a special curved foam or somethint? I'm more concerned about the back and giving the proper support, but not sure of the correct way to go about this for the arms either. Right now there is a lower cushion, and and semi loose cushion on top.
http://i1185.photobucket.com/albums/z348/heskett6/chair416007.jpg
http://i1185.photobucket.com/albums/z348/heskett6/chair416002.jpg
http://i1185.photobucket.com/albums/z348/heskett6/chair416006.jpg
You should be able to remove the existing arm foam, and wrap the arm with some 2" foam and batting. You will probably have to form pleats around the front show-wood.
The back shouldn't be too hard. Maybe some 4" foam with batting pulled down to form the curved edge along the top.
These adjustments will probably effect the dimensions of the seat cushion.
On the back I would let the customer try several different thicknesses and densities of foam to see what is comfortable for them. They don't want to sit too far back or feel like its pushing them out of the chair.
Kody is right. When you start re-styling a piece of furniture, it's easy to lose the comfort of the original design in an effort to achieve a new look.
These pillow backs are generally pretty soft. If your going to make it a one piece back use soft foam. Make it the same thickness as the existing back. No special foam is needed. At the top of the foam trim it to fit, glue some thin fabric 2-3" on the foam and staple this to the frame. This will give you a nice edge. Just tuck the sides and bottom in and your all set. Make them a couple inches larger so they tuck in nice. The arms are basically the same idea. Pleats like sofa mentioned will be needed. again glue some thin fabric on the top edge like on the back.
I just re-read your post, and see that you have a sofa also. Are you planning on one long solid inside back? Or 3 sections?
With 3 sections, you could divide the sections with welt, and sew a pull to the inside of them.
Thanks so much everyone!!! This forum has been such a big help to me during my first year in this business :)