A few questions regarding drafting and construction of trousers

[Gerry]

"1927 Cone Mills develops the 10 oz. red selvage denim exclusively for the 501®  jeans. The denim is woven in 29" wide looms and is known as XX denim"

https://www.levistrauss.com/wp-content/uploads/2016/06/2016_CompanyTimeline_Long_F.pdf

The narrowness of the cloth explains the cutting method.

[DOG SALT]

Yes, I see that it would be a good educated guess that the early 501's were drafted from the sideseam inwards. I question this though, as one should not continue their studies based upon uncertain information. I agree that they probably were done that way though, it does make sense. There is some interesting info about this, jcsprowls from the old forum gives us "You mentioned you want to work with selvedge denim. The patterns for these look different than other 5-pk styles. The side seam is poker-straight, which means the grain is different than what you will find in a pattern book. This also means the crutch and inseam curves need to be different because the grain shift alters the degree of stretch in these areas." I wish he was around still so he could explain further. Maybe he is, idk. I didnt find his name when i looked it up here, though. Here is a link to that thread: https://web.archive.org/web/20150910002011/http://www.cutterandtailor.com/forum/index.php?showtopic=1157

On another note, I have been measuring the seat angles of some of my pants. I first measured by finding the center line (by lining up seams from hem to knee), squaring a line from there to make a horizontal one, and then measuring the seat from that line. Here are those measurements;

Levi's 501 ~1999 34x34: 65 deg
Wool ~1950 bdu pant 28x30: 63 deg
Carhartt double knee 34x30: 67 deg
OG-107 trouser 30x29: 66 deg
white oak 501 (modern) 32x30: 72 deg
Ralph Lauren cord trouser (modern): 78 deg

Some of these really seem off. 72 deg for a pair of jeans? 78 for corduroy trousers? I realized after taking these measurements that using this method has flaws. If the pants were not drafted from the center line, or if alterations had been done to one of the seams, the angles wouldnt be correct. 78 degrees really seems crazy for a pair of trousers, but that one was actually fairly accurately done. I squared from one of the corduroy ridges to find the horizontal line. I am still learning though, so maybe such a steep angle isnt so crazy for a pair of dress pants. Duffy's draft gives me 77 deg, which is pretty close to that.

Realizing the faults of this method of measure, I decided to try another method. This time I found the grain by threading a needle and thread between the threads of the fabric, following one thread in it. These measures were a bit different
Levi's 501 ~1999 34x34: 62 deg
white oak 501 (modern) 32x30: 68 deg
Naked & famous selvedge 30x30: 71 deg
Havent had time to measure the other pants with this method. There is a fault with this method I have found. If the pieces were not cut on the straight grain, these measurements would be off. I believe this may have actually happened with one of these pairs. The ~1999 501 I have was split down the back seam for alterations. using this method, the left panel gave me 71 deg, and the right 61 deg. Also with the selvedge denim, if these were drafted with the center line approach, the angle would be wrong. Maybe that could explain the steep angle of that pair.

I would think that a jean draft would have a seat angle of around 60-65 degrees as leggatt says in his book (the climax system) that 60 deg gives a good measure for riding pants, and 65 for walking pants. Not sure though. Im also not sure if any of this info is useful at all, as both methods I used have definite flaws. Leggatt also says that 78 deg, which is the same angle as the cord trousers, "would not allow for movement of the body in a sitting or stooping position." This doesnt seem to be the case with those trousers though. So either I measured wrong (unlikely with this pair), or leggatt is wrong. I will continue my search for info on this.

Also, if anyone has a full pdf of the climax system by leggatt, that would be greatly appreciated, as I have only seen a few pages of it. Here is a link to what I have seen from it: https://web.archive.org/web/20171226152238/http://www.cutterandtailor.com/forum/index.php?showtopic=392

[Gerry]

I'm glad you linked to the Leggatt scans Salt Dog, because I really had no idea what you were talking about at first. I now see that we have a different idea of what 'seat angle' is.

It appears to be another way of estimating ease. The smaller the angle, the more ease you're adding at the seat (in effect). As I mentioned earlier in this thread, we can measure seat ease. So why would we want to factor in guess work?

Thanks to Don McCunn, we also have a way of measuring additional rise required at the back. Again, bye bye guesswork.

Re selvedge jeans, the curves are obviously going to be different, simply because they travel out from the inseam more than they normally would. I'm guessing that what jcsprowls was getting at, is that this puts more of the material along the inside leg towards the bias. Meaning that it will stretch more over time.

Perhaps modern, bespoke jeans makers account for this with certain shaping. I very much doubt any such thought went into the design of Levi's 501s though. They were utilitarian, work garments. When working, miners had more important things to focus on that the cut of their trousers (the philistines).

As for poker straightness, just look at this photo of a pair of vintage Levi's:

https://federicodecalifornia.files.wordpress.com/2010/07/oldest-pair-501.jpg

Which comes from this site:

https://federicodecalifornia.wordpress.com/2010/07/07/levis-501-xx-california-denim-•-1850-1969/

Also the first photo (and following chart) seen here:

https://www.heddels.com/2016/11/vintage-levis-501-jeans-the-ultimate-collectors-guide/

[TTailor]

I have two editions of the Climax system but they are not scanned.
I could scan and send you a few pages, if you know what you want  but scanning the complete book is not something i have time to do.

[Gerry]

Some more Levi's stuff of interest:

https://www.youtube.com/watch?v=xmaqrw6GJPM

[DOG SALT]

Yes, I love looking at old levis. That video you linked I watched years ago and definitely was one that sparked my interest in levis. I see that old jeans are cut quite wide so drafting from the side seam really wouldn't mess the fit up much at all. With the seat angle, my understanding is that you can have whatever amount of ease you want at the seat, and the angle is what is changed for large/flat seats. I have seen many drafts measure from the seat angle-center front intersect to the horizontal seat line with 1/4 seat+4 seams+ease. So you could change that variable.

Terri, I really appreciate it! I think I would continue with the books I have been reading and after those, I may request some scans if I think there are some specific pages I think I might need from that book. I would never expect anyone to scan a whole book for me, hahah.

[Schneiderfrei]

Jcsprowls was really great.  He had said he was going to write a book, from his experience in industry, but he retired rather abruptly.  He is missed.

[Greger]

Might look at Trew pattern systems. Pressing them as trews are pressed, before sewing, would probably help.
Maybe I mean Jack Tars

[Schneiderfrei]

Trews are pants that have no side seam.

Still relatively popular in Scotland.

G

[Greger]

Think Jack Tars are similar.
Fold the pattern paper in half lengthways and draw the pattern. For straight side seams add the seam allowances (inlay, too) and cut. This can be adapted for jeans. Might want to press a curve in the side before sewing.

[Despos]

Didn't read all of this thread and it has changed course to discuss jeans. Will share what I do regarding 3 questions I read.

Adding all of the outlets on the inseam reduces or hollows the curve on the back part. This makes the back of the thigh cleaner and requires less iron work on the back part from seat to knee. The more curve on the backpart from knee to crotch, the sloppier the back is and harder to press.

Hesitate to isolate how I find the height of the back part at CB or the angle of the seat curve because both work in relation to the rest of my draft. It may not have the same effect if the proportions of your draft are  different. My method is super easy and have been doing this for decades without issue.

Place the long arm of the square on knee notch of the back part to the hip point of the seat and the top of the square on the top of the outseam which will be the waistline.
Small arm of the square extended towards the center back seam. Draw your line. That's all. Keep the back outseam and the waist line squared off. The height at center back is determined by and in relation to the angle of the outseam on the back part. If the pattern is open the height will be higher. If the back panel is closed the back height will be lower. The angle of the outseam is the most important element of fitting different seat shapes and postures. The height at the back is always corresponding to the amount the outseam is open or closed. There are a few tiny tweaks used for extreme postures but too esoteric and specific to explain.
I make the waistline convex from out seam to center back so it becomes straight after the darts are sewn. This prevents a dip in the waistline at the darts.

Seat seam angle is just as easy. Lay your ruler on the waist point of the top of the backpart and the other end on the knee notch, draw the seat line. That's it. A straight line from the top of the centerback seat line to the knee notch on the inseam of the back part.  It is self correcting because it is determined by the angle of the back outseam. Been doing this for decades without issue.

IMO this works because it keeps an organic balance of lines and angles between the outseam, back height and seat line.  It's fail proof if your outseam angle is correct for the body type. It's also backwards of the Duffy video on the first page.
Again a warning,  this works with the way I draft the front and back panels.

[Greger]

Thanks Despos.
Interesting too.

[TTailor]

I control the seat angle on my draft with pivoting the corner of my square from a point on the cb seat line that I have determined first and an additional measurement placed above the crotch line close to the outseam.  I know what number I use for "average, and what I might use for a full or flat seat.

I too draw my outseam with the square from knee through the hip point to the waist, and square off for the waistline. 
It really does all needs to work together with how the draft works, and the shape of the particular body!

[TSjursen]

Very interesting method, Despos. Not sure I fully understand the relationship between the different points in your method, would be very nice if you had time to post some pictures of the draft. By fixing the seat seam angle by way of the knee notch at the inseam, what happens if you have a very wide circumference at the knee? If you always fix the ease in the seat according to the width of the trousers at the knee I guess I agree that your method would work, but say you wanted it full in the seat and very tapered toward the bottom, would that not make the seat seam straighter with a smaller knee and more crooked with a wide knee? I usually make the seat seam more crooked in a slim trouser to get enough ease for sitting and walking, but can make it straighter and more clean fitting in the seat area in a wide trouser without reducing comfort for the wearer. I realize most tailors these days are more interested in getting a very clean and smart fitting seat, but personally I always recommend extra length in the seat seam to my customers if they do not object to the seat not fitting completely clean. Speaking of jeans, that is a part of what makes them so comfortable in wear: The extra length/more crooked seat seam, in addition to the very open legs (more length in the inseam). I also like to full on 1/4" to 1/2" at the back part along the side seam a little above the seat line if the fabric allows it. It makes the seat a bit full and wrinkly but this part will always be a tradeoff between cleanness and comfort in my opinion, especially in slim trousers.

[Hendrick]

Thank you all...

Despos, I will try this immediatly. I am currently doing a mens' slimfit stretch trouser in a bi-directional heavy stretch technical tricotine (much like jodphur fabric). I am never happy about how the roundness on the side of trousers gives length in stretch materials. I will keep you posted...