Thursday, January 24, 2013

The Net Effect of Changing Length Above The Armscye (When You're Knitting Flat a Bottom-Up Sweater) with Set In Sleeves

You know I'm all about the fit and the fittedness. You may also know I'm making a retro-sweater that's supposed to fit slimly. And you can't help but to know how I'm really short in the waist and particularly from above my breasts/armsyce to the shoulder. 
Princess Jumper and Photo by Susan Crawford
Perhaps, from the pic above, you will agree that the fussy stitch pattern (let me assure you, it's fussy), which starts above the breasts, must be the perfect length or the sweater's gonna look all kinds of amateur. (One risk is that the stitch pattern could encroach towards the full bust in a kind of visual reverse of an empire seam that doesn't actually fit under the bust at the rib cage).

Which leads me to the part of this post wherein I tell you how I - when first I began knitting this - deliberately altered the length above the armsyce on the front and back pieces of this sweater without adequately considering (until I started knitting a sleeve) the shaping alterations it would require in the sleeve cap. Oh my.

Quick info: The sweater calls for an armscye depth of 8.25 inches to the shoulder. My dimensions require 6.75 inches (at the large end). 

Let's start by thanking Gail, the knitter who is metaphorically holding my hand while I figure this out and who also happened to be able to direct me to this shockingly fantastic post, even though I searched via 63 different terms to locate something that might have been half as useful, only to come up with zilch. I warn you. It's a pretty scary article. (Note: You have to understand the Pythagorean Theorum which, let's face it, I can barely spell.)

Very, very briefly, the concept is that:
  • The required size and shape of a sleeve cap is entirely - and utterly irritatingly - contingent on the length of the armhole. (Sewists, you know that.) 
  • Furthermore, the width of the sleeve (specifically its angle), just below the start of the sleeve cap, is mysteriously related to the shape and depth of the armscye and this is one of the many factors that determines how you shape said sleeve cap. 
  • Pivotally, one must determine the angles, altitudes and lengths of the front and back armscye curves and then mathematically reflect them in the shaping of the sleeve cap. The cap is made of concave, moving into convex, curves on either side of a bisecting line (which we can view and calculate as straight edges of triangles, hence Mr. Pythagoras). Until you've calculated one element, you can't determine the other. And till you've determined the other, you can't exactly knit it.

Are you feeling a little overwhelmed? Take a moment to absorb that info, assuming it's never occurred to you either. Then be very glad you're not 3/4 of the way through this sweater having just come to the realization.

This, my friends, is the reason that picking up stitches at the armhole and knitting sleeves in the round (with sleeve cap short rows!) was invented. But it's not the best method when you're working with a vintage design because it doesn't look particularly vintage. Note that the article I've linked to above gives you all kinds of mathy tips to short row when a pattern calls for the flat, sleeve cap method (but you've got to be careful or you'll get a dreaded short-row poof - like you find in a heel or a bust curve).

In truth, aside from my utter confusion, I'm in just about the best position I could be in. Why?
  • I've knitted the body in 2 separate pieces (as the pattern calls for) and all of the stitches on the front and back pieces, at the shoulder (this is bottom up, flat knitting) are on stitch holders. (Side note: Due to other math glitches, I appear to have too little length at either side of the back at each shoulder. But I can adjust this easily before moving forward with the sleeve.)
  • Mercifully, I figured out I was going to have an issue before I started knitting the sleeve cap on the first sleeve so it's likely that I won't have to rip anything back.
I'm  having difficulty absorbing the complexity of the trigonometry and calculus involved in adjusting the shape and height of my sleeve cap to suit the changes I so innocently made on the front and back pieces. Note: Yeah, I was cavalier, but I did measure the bodice pieces to fit my body. And, after that, I did undertake the significant work to reorg the crazy stitch pattern to reflect the changes I needed to make. Point is, cavalier does not equal lazy (just stupid, in light of the fact that I've already dealt with this situation on a tailored jacket or two).

I'm sorting this out, she says like a deer caught in the headlights, and I will post on the details of my corrective alteration, as soon as I come up with it. (That statement fills me with hope.)
In the meanwhile, have a look at the pretty bodice pieces, such as they are at the moment:
 
Today's questions: Have you ever knit flat sleeves in a bottom up, flat pattern, and determined that you needed to change the length of the sweater above the armscye? How did you deal with the resulting change in sleeve cap shaping i.e. scary math or winging it? How did that work out for you, either way? If you've got any words of encouragement, I'm happy to take them.

30 comments:

  1. Aww, thank you! Sorry I gave you a mathy headache.

    If you had been in my Montessori elementary classroom, I would have had just the lesson to help you wrap your head around the Pythagorean Theorem - it's really quite amazing!

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    1. I really find that hard to believe :-)

      I am obsessed with resolving this. Seriously, I've had a headache for 36 hours from the sheer force of thinking.

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  2. I've had the problem a couple of times. Once I didn't realize the sleeve cap was too long until I'd knit both sleeves so I just sewed it in and left the extra inch as a sort of shoulder pad. It was the eighties I got away with it. The second time when I realized I had too much cap on the first sleeve I just took note of how many rows needed to come out, ripped the whole cap out and winged it. Came out fine, but not much help to you.

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    1. Ha! Well, all's well that ends well.

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  3. That's a fabulous description of how to accomplish it mathematically, and you've shown that you are up to any challenge, but...why not just keep the initial sleeve bindoffs, keep the original cap shaping, but recalculate the rate of decreases? If you've shortened the armhole, you should have fewer rows to accomplish the same number of decreases that the pattern calls for. Multiplying row gauge times inches removed should tell you exactly how many fewer rows you have to work with. Or am I missing some critical detail by wanting to avoid trig, calculus or Pythagorean theory? :). Karen

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    1. Thanks Karen. I'm thrilled if it makes even partial sense to someone else. I agree with your rationale and my goal is to try to keep the same math up to the inflection point (where the curve goes from convex to concave at the bell). But the idea is that, when you change the length of the outer curve, you have to change the shape and angle of the sleeve curve. And that's where things get less knowable.

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  4. WOW! I love your progress so far. And, I've never knitted a sweater so I'm absolutely no help at all. But, I do love the yarn choice and color - fantastic. I have faith that you will come away with a wonderful garment - good luck and I'm learning a heck of a lot from the commenters!

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    1. Thanks! I look at my progress so far and all I can see is the thing I haven't figured out yet. Hmmm...

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  5. This is a subject dear to my heart (and career). So dear, that I can calculate sleeve caps in my sleep. Email me if you want math help.

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    1. Oh, how awesome (for me). Thank you. I know we've emailed but I can't find your address. Will you email it to me or leave it in a comment here? I'm at kristinm100 at yahoo dot ca.

      I have a litany of emails to Gail (and to Susan Crawford, the designer). Maybe on the basis of that info I've compiled, you will be able to provide advice.

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    2. alexandrav at gmail

      I'm on weird hours, so you may not get an immediate reply.

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    3. OK, I've emailed a hideously long and complicated thing. I really hope you can make sense of it. Thank you so much!!

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  6. Wow. This may be why I stick to socks! LOL I seriously have a growing list of your posts that I've bookmarked under the heading "For My Next Sweater".

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    1. True story: I almost said fuck it and started a new pair of socks. But my goal is to make my next pair of socks simultaneously on one needle using magic loop. Something I've never attempted. At which point I actually started to laugh. Only I would decide to leave a project I don't understand to start a new project using a method I have no understanding of. Esp. when my other craft time this weekend will be spent trying to fit a freakin' tailored suit jacket. Egad.

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    2. LOL File this under: it might be time to find the local chapter of overachievers anonymous. ;-)

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    3. I know. And after this weekend of jacket fitting, I'm ready to curl up in a ball.

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  7. Oh wow! I thought making a baby booty was an accomplishment!! (It is actually, for me!)

    hahaha, serious... such time and beautiful work, well worth every hour spent!

    Much love, bundana x

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    1. It is an accomplishment! And it keeps baby feet toasty! Thanks C x

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  8. Wow. I've bookmarked this post for Martin as he's been running into issues with the sleeve/armscye interface in adjusting his shirt design. It figures there's a mathematical relationship.

    I just read on Mater's blog that you read 175 blogs a day. Is that really true ?!?

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    1. Susan: Hand knitted fabric works extremely differently than woven fabric when it comes to sleeves and their insertion. Of course, there are intersections when it comes to drafting the right sleeve shape for the armsyce. But it's a more complicated process, I suspect, when designing a woven shirt. Really, he should have access to some very kick-ass drafting books given the challenge he's about to take on.

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  9. He does have several, and we've ordered more, but I just assumed that a mathematical shape relationship would hold regardless of the material. Am I wrong about that? I'm going to study Gail's post anyway even if it doesn't fully apply.

    There's a sloper dilemma we're dealing with too, since we didn't invest in an "average" form. Martin is the sloper, and he's close to an average size 42, but his neck circumference is larger and his waist is narrower. The CAD grading function just adds horizontal and vertical increments based on rules for a particular sloper, so Martin's unique dimensions would proportionally scale up and down with grading. We are wondering whether it's best to adjust the sloper design to be more average before grading, or just use Martin as the sloper and provide good instructions on adjustments, since the average sloper grading doesn't necessarily fit either.

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    1. There are def elements that hold, for ex. the general shape of a symmetrical sleeve (though the best drafted sleeves for wovens are not symmetrical to account for their lack of stretch and the increased length of the front armscye) and the need to ensure that the length of the sleeve from armpit to top is the same as that of the armsyce.

      Thing is that hand-knitted fabric (and then, in its own way, machine knitted fabric) have different fitting properties because they have so much relative give.

      Practically, they're different beasts.

      Martin really has to check out this blog and join her forum, if he hasn't already. This woman is a commercial pattern drafter and clothing designer (for others) and what she talks about will be very germane to what you're trying to work out: http://fashion-incubator.com/

      Kathleen's book would be invaluable to you, I suspect.

      I don't know what will be easier to grade or to manufacture - and what will be more cost effective - Martin's sloper shape or something more average - but I think that's got to weigh into the decision. This is, on some level, about sustainable business.

      Having invested in that beautiful dress form, I hope you get lots of use from it, even if only to fit shirts for Martin himself. Of course, once you decide to be clothiers, I wonder how many shirts either of you will be making for yourselves :-)

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    2. Oh good, I'm glad to know you recommend Kathleen. I'd already found her and ordered the book & applied to join the forum. Her post on sleeve cap ease being bogus was really interesting and informative. Basically Martin drapes to himself but it's nice knowing the technical reasons why his sleeve cap shape matches hers.

      We're not planning to sell constructed garments, just the patterns, assuming we can figure it out. (We successfully digitized our first shape this morning. So exciting!) Martin will get to wear the samples, as a bonus.

      As for the sloper, once we figure out the CAD process it should be possible to offer Martin and a more average variation. Since we're printing one at a time we might even be able to offer custom patterns adjusted to specific measurements. We'll see.

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    3. Glad to hear it! I know she has a very good reputation.

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  10. Oh you really have a knack for making my head spin. I fudged the sleeves on my Milena cardigan because I lengthened the armholes. But it wasn't too hard cos they were just short row sleeves. My brain is so lazy that I hope I never encounter this problem lol :P (Surely I will though!)

    Good luck! :)

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    1. Honestly, Jo, I've had a headache since Thursday. And you are NOT lazy!

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  11. As mentioned in a comment to you on my blog ...this post blew me away. I got caught up in a web of Knitty technical articles and then lost the ability to read!

    It all seems so complicated.

    And here I was worrying about whether or not to try and knit a top with splitty 2ply yarn!

    Thanks, Kristin, for putting it into perspective. ;-)

    You'll sort it out. You always do.

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    1. Gotta go check out your blog comment reply. Whenever I read your posts I am so impressed by the the care you take to ensure fit is spot on and that the properties of the pattern are well-executed. I am sure you would go at least this far under the same circumstances. At least you're game to rip things back :-)

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  12. I think I'd be weeping if I were you. This makes my head hurt too.

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    1. Sorry! I assure you, I'm not jumping into this kettle of fish again anytime soon :-)

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