Seat seam is pulling into the gap:
Image1: because of an erect posture that wasn’t considered in cutting, the undersides are showing a surplus length and the seat seam is pulling in the gap as a consequence of a too short rise of the topsides.
The Origin of the Error:
The error shown is all too commonly seen. The undersides have too much length in the gluteal area, piling up below the waist seam and unpleasantly pull the seat seam forward into the gap area.
A perfunctory view will cause some colleagues to assume, the undersides just have a bit too much length for comfort, which gets more obvious because of the erect posture and can be removed by widening the crotch point.
This view is quite right. The customer’s posture, which is slightly erect, and the underdeveloped buttocks were not regarded sufficiently when cutting. Otherwise cutting and assembling would have been executed completely differently.
But it’s easy to recognise this fault on a finished pair of trousers. It’s much more difficult to recognize the customers posture, waist-, hip-, and leg form before cutting and assembling, and taking it into account. Additionally, some basic considerations concerning the trousers have to be discussed and decided with the customer:
For waistband trousers it has to be regarded whether:
a) it will be worn exclusively with a belt,
b) suspenders should be used additionally and the belt is just for embellishment,
c) the customer prefers only good looking but less comfortable “just for standing” trousers,
d) or if he prefers a trouser that is comfortable while sitting, but will show some length when walking or standing.
The customer has an erect posture and a slightly forward hip. Using a normal pattern template the pattern should have been altered according to the sketch. In this case probably a pattern template with a crooked seat angle was used causing the additional length in the gluteal region.
In the waist area the trousers are “blocked”.* That is to say, the seat seam, the darts and the side seams were not drawn hollow enough for the customer’s waist form, which causes the additional length to pile up below the waist seam.
Looking at the front view we could diagnose, that the topside is lacking length at its centre and the trousers are pulled up towards the front.
The normal topside pattern is slashed at half the rise from the fly line, almost to the side seam and hinged open for 1— 1.5 cm at L1-L2. This raises the waistline at B1 for the same amount and makes the fly line go inward moderately at B1 at the same time. Thus the trousers get the necessary length for (across) the trunk area. (for the rise?).
The undersides must be shorter at the seat seam. That’s why the pattern gets folded horizontally at halve the rise for 2— 3 cm at G1-G2, or gets slashed and put on top of each other for the same amount. The technical alterations can be seen in the alteration sketch:
a) the underside is pivoted as a whole,
b) the seat seam is straighter towards the top and has to be widened therefore in a finished pair of trousers (when altering a finished pair of trousers),
c) at the same time the undersides is shorter at B3,
d) to keep the correct waist width the side seam must be decreased gradually for the same amount at B6 and
e) the seat seam is to be drawn a bit concave towards the top according to the body form,
f) the crotch point must be widened for 2 cm at S3 to achieve the correct diameter.
Image 2; The topsides need more length;
the normal pattern is therefore “blocked” at the half rise.*
Image 3; To the normal pattern of the undersides,
the seat seam is reduced by 2—3 cm at half the seat height, so the undersides are straighter.
The topsides and undersides certainly require sufficient ironwork.
In a finished pair of trousers, the aim is to do the alterations as quickly and simply as possible yet at the same time achieving correct results:
There must be at least some inlay at the seat seam, because it needs widening there for 2— 3 cm. The waistline is shortened at B3 and decreased at B6.
These trousers also lack sufficient iron work, which cannot be avoided in trousers with narrow legs, even when they are cut correctly.
For the prominent calves, the undersides need sufficient ironwork at the inseam and the side seam; the seat seam must be stretched heavily as well.
* With thanks to Schneidergott for this explanation.
"Abgesperrt" means "blocked" in older texts. In this particular case the waistband doesn't allow the cloth/back trouser to go up, so everything is pushed downwards.
"Gesperrt" or "sperren" of a pattern means "to open (-ed up)".
"Kneifen" for that matter means the opposite, you close/ overlap a part of a pattern.
Edited by Schneiderfrei, 25 June 2015 - 09:52 AM.