Just out of curiosity, what is everyone's preferred method for drafting a costume pattern? Butchering something that already fits and copying? Draping and pinning? Or drawing something on the fabric...going balls to the wall and hope what you cut out is the right shape?
I'd love to use the first method, but that never happens to something I'd be okay cutting up. The second only works occasionally. And the last approach I use for pretty much every costume I've made to date.
I do a combination of those things... Well, I generally don't butcher anything for a pattern. But I drape, I draft, and I alter existing. It just depends on what I'm working on and what needs done. If I already have a pattern that comes close to what I need, I'll mock it up and draw on all the details that are missing. This shows me where to cut it apart and create a new pattern.
I rarely do anything from scratch for myself anymore. I have so many patterns that SOMETHING in my drawer is close enough to what I need for me to get it the rest of the way there with very little work.
There are also certain flexible rules/guidelines when it comes to patterning:
Pants, Skirts, and sleeves are almost always drafted or altered from slopers or existing patterns.
Menswear is almost always drafted or altered from existing.
Women's tops...
For a lot of women's wear, there's no substitute for draping, so anyone woman that is serious about patterning their own stuff should invest in a good dress form. Not one of those adjustable ones either, like a good solid Superior, Wolf, or Modern. Alternatively, there's a company called My Twin Dress Forms that sells kits so you can make your own that matches your body
Order - My Twin Dressforms & Pantsforms, made in the exact shape of your body! A must for the serious sewer
This is really just the next step up from doing a duct tape or paper tape dummy (paper tape is better as it doesn't stretch out over time)
Clone Yourself A Fitting Assistant - Threads
One thing I always recommend for any patternmaker is to pick up a good reference book such as:
Amazon.com: Patternmaking for Fashion Design (3rd Edition) (9780321034236): Helen Joseph Armstrong: Books
These are filled with easy to access information on how to do things like turn a plain, one-piece, straight sleeve pattern into whatever other style you need.
Are you going to Dragon Con this year? Myself, Cathy of GSTQ fashions, and a couple others will be doing a panel in the costume track on patterning. We usually try to cover a few techniques that you can do with little training. It's at 1pm on Saturday.
I think I just published a novel...
In a related note:
My undergrad professor published this article.
http://costuming.dragoncon.org/media/duct_tape_draping_fclements.pdf
Actually a great tutorial for making corset patterns for yourself.