1930's mens work blouse - sleeve & armhole issues?

[Lieckio]

Hey everyone!

New to the forum, accidentally found this while reading about vintage sleeves and drafting. Seems like this place might have some people that could help me with some issues I am having, so I decided to make an account and make a bit of a topic about it here. If I posted in the wrong place (tried to read all the guides), do move this about to a proper place

I am an... intermediate? Competent amateur? when it comes to drafting - I have made a fair few clothes in the past as well as sold some professionally in the past. But I am originally a hatmaker and have mostly drafted, sewn and sold vintage style hats in the past. The drafting system I use for hats is wildly different from what is generally seen in clothing drafting, so I've had to do some learning on my own. This has caused some gaping holes in my knowledge of drafting clothing - and many guides and books (both period and modern) don't go into reasons why something is done the way it is done. Where as in hatmaking I understand the mathematics underlying the curves and shapes, with the complex world of flat drafting clothing I am mostly just confused and try to stick to the drafting guides with minimal adjustments.

It's probably useful to mention that I also work almost exclusively in digital format (Seamly 2D, Illustrator), as I have a large format plotter in my workshop and digital working methods allow me to churn out different sizes parametrically easily and fast.

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With the introduction behind me, let's talk about my current project & issue.

I've been commissioned to make a set of 1930's work blouses according to a period Finnish drafting guide. I've got 12 different sizes I need to make. I've got the original drafting guide for the blouse as well as the manufacturing guidelines and size table that is supposed to work as the basis for drafting these.

Now, I've read a few topics here and like some people have mentioned, there are some errors in the drafting guide that I have sorted out over the past 3 months I've been working with this. Sadly the drafting guide is also somewhat lacking - assuming knowledge I obviously don't have.

Let's start with the view of the finished draft as it's shown in the guide.



I am not sure what the drafting system used here is, as I have not found one exactly like it. My suspicion is that it is based on a Finnish drafting system from late 1920's as it shares some resemblance to this in principle.

While my draft does match the image above for the most part, there are few things I am strugling to understand.


1) Armhole shape, and sideseam drafting and trueing



Here's the shape of the armhole (and the sideseam). All the points in the image come from the draft guide, except point F1, which is my own addition (from the sleeve draft, to which I'll come to later). Point J is called point K in the original image, even though in the guide it is called J, so I've merely replaced it.

Now, the draft guide says the following about drafting the armhole:

"Draw the bottom and the front of the armhole curve 1 cm outside the guidelines."

This is done so in the example as well. However, I am totally unsure as to how to define the shape of the curve correctly, especially so that it matches the backpiece. The point 7 is said to be "halfway between U and E minus 1 centimeter".

However, the armhole curve in the front "cuts off" at a seemingly arbitrary spot, same goes for the backpiece curve. The length of the side seam is equal in both 7 - 6 and 7 -3 if I place the points in the sample draft at the same spot, but the curve is not a flush, matching curve. However, if I move the backpiece as is to the seemingly arbitrary spot of the sample draft, the curve matches. I suspect that the intersection point of the front and backpiece is somehow related and ought to be able to be calculated/drawn, it just isn't clear to me how. Below is image of what I'm trying to explain here.




From left to right: As drawn, moved to the seemingly arbitrary point, side seam aligned.

It seems to me that I am somehow to first draft the front curve, then match the side seams and from there to draft the back curve. However, it is very unclear to me at what point the front curve is parallel to the chest line and when it's parallel to the imaginery front vertical line. I have a suspicion that the point Y has something to do with all this, but it's not mentioned apart from the placement in the draft.

All this seems to me I could resolve, if I only understood where the parallels are (and why) and how am I to determine the side seam length.

The next issue is very much related to this;

2) Sleeve draft and balance points

The drafting guide only mentions this simple, yet cumbersome sentence for the sleeve draft:

"The sleeves are regular jacket sleeves, except the base/bottom/(cap height?) is short and wide and the under sleeve is long at the top"

This has proven to be quite troublesome, as there is a standard jacket sleeve draft available, but the description even when not translated into English doesn't seem to make much sense for us Finns either. The word used there doesn't make it clear if they are talking about a "short" cap height, or some bottom / base of the draft that I don't understand.

In any case, here's the image of the sleeve draft:



It uses the armhole circumference as it's base measurement. The sleeve draft guide tells me that the point F is "where the F -line in the front piece crosses the back armhole", which is halfway between points A and T in the body draft. I assumed this would also be where the back armhole curve crosses the vertical line J - U, but it doesn't seem to be so, but a few centimeters lower.

^{(In fact, now that I am looking at this, it could be that the whole armhole curve crosses the J-U line at F1 and the M - E line at Y, then moved one centimeter lower and forwards? Perhaps this would be the answer - I just need to figure out how to draw that on Illustrator)}

As I don't have image of how the original sleeve draft is supposed to look like - there isn't one - I 've resorted into disassembling few original period blouses to take a look at their sleeves. I have 4 different sleeves, none of which match with each other.



Here's a comparison of three of these sleeves. They are all made by a different manufacturer, so it makes sense they are different in shape and style slightly.

However, they are all "sports sleeves", so the armcap at least is lower than the provided jacket sleeve is.

I've tried a million ways to get a sleeve out of the draft that matches the armhole - but I keep failing. I've had some success lowering the sleeve cap height by increments (it's 1/4 of the armhole circumference in the draft) by 1, 2, 3 and 4 centimeters. I've done the same with D - B height, as it seemed to make sense but I have no idea if this is correct or not. I can get the length of the upper sleeve curve to be pretty good and it sits somewhat correctly. However, the issues arise when the undersleeve is to be matched with the lower armhole.

I've used the C point (2,5 cm above B in the sleeve draft, 2,5cm above the bottom of the armhole in the front draft) but it doesn't seem to produce a matching curve in the sleeve. With moving the G-point of the sleeve more towards D, I've gotten the length to match. The problem is is that the sleeve underarm seems to dip lower and at an different angle than that of the actual jacket armhole, causing some buckering/tension right around the C-point. The back balanse point to the top of the shoulder and down towards C seems to work pretty well, but as I get close to the C-point and try and fold the seam allowances and stitch them down, there is some pulling.

All in all, with the sleeve, I am getting a bit frustrated as I seem to have no idea how to draft a matching sleeve.

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So long story short, thank you if you've had the energy to read through this and I would be more than glad to receive tips, hints and advice on how to move forward with this project as it has ended up costing me a lot of time and energy and is getting - quite frankly - quite exhausting.

Not knowing enough of the basics to adjust my draft to fit the armhole and what is seemingly require of me is exhausting to say the least. 

[Lieckio]

I forgot to mention that in the side seam the points 3 and 6 are equal distance from the point S. Point S itself is 0,5cm to the left of where the line 7 - X crosses the waist line.

There are two pleats 4 cm apart in the upper back piece, and the "material for the pleats is drafted  to the right of point 3" according to the drafting guide. The dashed line shows the "final" line of the side seam with the pleats gathered.

[stoo23]

Hey, Hi Lieckio, welcome aboard.

I might edit your post slightly (and move the Intro' part to the Introduction section) but other than that, I think you have posted in the correct section

I'm sure there are members here that can help and offer assistance etc 

cheers

[Lieckio]

Thank you! What a wonderful forum you have here, been reading too many interesting topics and posts here today

I don't know how I missed the introduction part, I can post an introduction there too.

[Gerry]

I'm loath to give advice on cutting systems that I don't use, simply because I don't understand a lot of them myself. However, there are some general tips I can give you (I'm sure others will chime in with the specifics).

Rather than get caught up with the draft's details, you're probably best off making a toile, being sure to leave inlay at the armholes, side seams, shoulders and hem. Test the draft on a real subject, then mark on the pattern any adjustments made during the fitting.

As is the case here, when it comes to armholes a few guide points are calculated/marked, then the cutter uses their eye to attain the correct shape ('rock of eye'). Specialist templates are available for drawing armholes, which takes a lot of the guess work out of things. I've never used them, but I see cutters/tailors using them all the time and many tailoring suppliers sell them.

With a simple side seam, it's usual to draw the armhole from front to back (or vice versa) in one go, so that there's flow, hopefully giving a natural shape. It's possible that the suppression at the sides (effectively a dart turned into a seam) causes the front to drop a bit at the seam, hence the 'stepped' way things are displayed in the draft. If that's the case, then I'd still draw the main curve as one, then redraw the base of the front a little higher.

Either way, I'd still make a toile to sort out these issue in a real-life fitting. Leave inlay and you can figure out what is necessary to make the pattern work. Also create balance marks at waist position of the side seams, so that you have clear reference points for any adjustments at the armhole/hem ... or for general balance. At the end of the day, most drafts are just a quick way of getting up and running. The real work comes during fittings.

Ideally, side seams shouldn't be too visible. With a simple shirt, they would be right under the arm. As this is more of a jacket in concept, the seams are a tiny bit further back by the look of things. Use your eye. If you want to be super precise about things, measure the seam position relative to the back and the front as shown in the diagram, work out the ratio between the two and apply that to your draft. Again, a fitting will tell you what looks right and if inlay is left, you can pin the seam until it looks right.

[Gerry]

Re armhole circumference, you have to 'walk' a tape measure around the armhole's seamline to measure its total length: turn the tape measure on its side and edge it around the draft. The armhole seam of the sleeve - the top of the cap - needs to be at the very least the same length. A tiny bit is often added to account for cutting irregularities, ensuring that the sleeve fits, or a noticeable amount more is added to the cap length if the sleeve is to be gathered into the hole.

The height of the cap is irrelevant - that's more of a comfort/stylistic thing. If the length of the sleeve cap is too short/long compared with the armhole circumference, it's not going to fit.

[Lieckio]

Thank you for the replies!

Rather than get caught up with the draft's details, you're probably best off making a toile, being sure to leave inlay at the armholes, side seams, shoulders and hem. Test the draft on a real subject, then mark on the pattern any adjustments made during the fitting.

As is the case here, when it comes to armholes a few guide points are calculated/marked, then the cutter uses their eye to attain the correct shape ('rock of eye'). Specialist templates are available for drawing armholes, which takes a lot of the guess work out of things. I've never used them, but I see cutters/tailors using them all the time and many tailoring suppliers sell them.

I've made several toiles over the past few weeks - and I've done exactly that and have made some additions over time, which has allowed me to get somewhere close to the draft guide. The real trouble here is, that I do this all digitally, so I am hoping I could get the curves out directly from the software, rather than having to print them and then hand draw the armhole curves after that.

In fact, if I was making this for myself, I'd have half the problems done away with the fact that I could just modify a single size and make it fit to my measurements. However, I need to make 12 sizes of these according to a size table, so I am hoping I don't need to just eyeball it for all of them 

Here's my draft on top of the draft guide drawing.




You can ignore the height difference; the draft guide uses different back height than the size table. The neckhole lines and the side seams are more a place holder right now, as I am not sure if this is the correct way to match them - I've taken inspiration from the existing original pieces I disassembled.The guide drawing is also distorted a little, as I had to scan it from the archives and it was *tiny*.

With a simple side seam, it's usual to draw the armhole from front to back (or vice versa) in one go, so that there's flow, hopefully giving a natural shape. It's possible that the suppression at the sides (effectively a dart turned into a seam) causes the front to drop a bit at the seam, hence the 'stepped' way things are displayed in the draft. If that's the case, then I'd still draw the main curve as one, then redraw the base of the front a little higher.

Excellent point about thinking it as a dart! That does help me get my head around some of this.

I also aligned the original pieces according to the draft guide, just for comparison. You can see how different they all are from each other and from the draft guide.

At the end of the day, most drafts are just a quick way of getting up and running. The real work comes during fittings.

Ideally, side seams shouldn't be too visible. With a simple shirt, they would be right under the arm. As this is more of a jacket in concept, the seams are a tiny bit further back by the look of things. Use your eye. If you want to be super precise about things, measure the seam position relative to the back and the front as shown in the diagram, work out the ratio between the two and apply that to your draft. Again, a fitting will tell you what looks right and if inlay is left, you can pin the seam until it looks right.

I might have to do some of this with the side seam indeed, to get the curve and shape matching. I was really hoping there was a simple technique at work here to get the side seam aligned, then smoothing out the curvature/shape a little to get it to sit right would be somewhat easy.

But it seems to me that the armhole curve matching is actually relatively simple, having it align with the J - U line a few centimeters below F-point would seem to create a curve that matches the diagram without me having to go deep into triginometric mathematics. I am fairly happy with how the front of the armhole turns out in my work, so I don't worry about that too much.

Re armhole circumference, you have to 'walk' a tape measure around the armhole's seamline to measure its total length: turn the tape measure on its side and edge it around the draft. The armhole seam of the sleeve - the top of the cap - needs to be at the very least the same length. A tiny bit is often added to account for cutting irregularities, ensuring that the sleeve fits, or a noticeable amount more is added to the cap length if the sleeve is to be gathered into the hole.

Walking the tape measurement in the digital world is super simple - all I need to do is click the line and I get the exact measurement down to 4 decimals. The original sleeves have very minimal ease, only about 1 cm or slightly more - hard to say exactly, as the original pieces have stretched over the nearly 100 years that has passed. With the sleeve draft I posted, if I drop the sleeve cap by 4 centimeters (from 18,6 cm to 14,4 cm), I can get about the same ease. The undersleeve does not match though with this draff and the shape in general is very different from the original sleeve.

The height of the cap is irrelevant - that's more of a comfort/stylistic thing. If the length of the sleeve cap is too short/long compared with the armhole circumference, it's not going to fit.

In this case it's not necessarily irrelevant - I believe in the original text for the guide they mean that the sleeve cap height is lower (and thus, the sleeve wider), as it is intended to be a work blouse. The drafting guide for the sleeve is for a suit jacket originally, so the tall(er) sleeve cap allows it to sit more nicely with the hands down. With a work blouse you need to be able to raise your arms. At least, my understanding is that lower sleeve cap allows for the sleeve to "stand out" more from the body and less restricted movement of the arm.

The original sleeves have a sleece cap height of roughly 14 to 16 centimeters, but it seems to have absolutely no relation to the size of the blouse they came from, so I have no great hints there for what is intended. However, if I lay the assembled originals on the table, the shoulder seam continues almost parallel with the folded sleeve.

The issue with fitting the sleeve right now is less about the sleeve cap height I suspect. It seems to me, that the width from C to F might be too much in my draft. This in turn makees the line C - K not steep enough (K is 1/4 of A - F). This might be fine if the armhole was more of a U shape in the front, but as it hooks to the left about 2 cm to 2,5 cm more than more modern patterns do, the chest piece doesn't have enough material to allow for the sleeve to  gather there nicely for the seam to fold over itself neatly.

One thing I suspect I could tweak around with is to reduce the sleeve cap height by a more moderate 3 cm and also tweak the C - F length. Currently it is 1/2 of armhole circumference minus 1 cm. I feel that if I take any more length from it, it becomes too tight around the bicep, but I might have to try a different length.

Other option is to just lower the B - D distance even further. Currently it is 1/4 of the armhole circumference which I've again lowered a few centimeters to retain the relation with the sleeve cap height. But I am not sure if that is a correct method to do that. Also the original sleeves would suggest that lowering it any further does not provide correct results.

I've also considered that perhaps B to 1 should be less than the 2,5 cm it currently suggests in the draft. This however would create a even flatter line for the sleeve to meet the armhole curve, so I am unsure if that would be the solution. It might also be that the B to 1 needs to be longer than the 2,5 cm. That might also make it easier to match the undersleeve length to the original.

As you can see, I am somewhat lost here when it comes to how modifying the sleeve draft affects how it sits with the body of the blouse 




One further idea I came up with that I might have to try is as follows:

The drafting guide for the sleeve says to draw the front notch C at "2,5 cm above the bottom of the armhole", but this assumes that the armhole has not been lowered by 1 cm as the body draft tells me to do. If I raise the C notch to 3,5 cm from the bottom of the armhole (or to 2,5 cm above the chest line), it would allow for a gentler curve on the sleeve to match to the curve of the body piece. The lower sleeve could then be more curved like in the drafting guide for the sleeve and it could accomodate the shape easier. This would also move the sleeve seam further away from the side  seam, which seems to be more in line with how the originals were assembled.

I've also drawn here a new F1 point 2 cm below the original, but it has minimal effect on the curvature of the back armhole - certainly less than whatever mistakes I'm going to make when cutting the fabric. I reckon I'll have to make a toile to see if changing the back balance point to the lower one has any effect on the actual sleeve or not.

Anyways, this is turning into a bit of a ramble right now, so I'll just post the reply for now and mull and think about all this a bit longer

[Gerry]

I've made several toiles over the past few weeks - and I've done exactly that and have made some additions over time, which has allowed me to get somewhere close to the draft guide.

Apologies for not having read your post more thoroughly (I only glanced through, if I'm truthful).

In this case it's not necessarily irrelevant - I believe in the original text for the guide they mean that the sleeve cap height is lower (and thus, the sleeve wider), as it is intended to be a work blouse. The drafting guide for the sleeve is for a suit jacket originally, so the tall(er) sleeve cap allows it to sit more nicely with the hands down. With a work blouse you need to be able to raise your arms. At least, my understanding is that lower sleeve cap allows for the sleeve to "stand out" more from the body and less restricted movement of the arm.

I didn't mean that the height is irrelevant in this case, I meant that in general it's a secondary thing. As you say, a shorter cap gives more ease, but isn't as clean as a higher cap where the opposite is true (less mobility, but cleaner). Once the style has been chosen, then all we're concerned about is matching the cap length with the armhole circumference. In that sense, the cap height is irrelevant.

The issue with fitting the sleeve right now is less about the sleeve cap height I suspect. It seems to me, that the width from C to F might be too much in my draft. This in turn makees the line C - K not steep enough (K is 1/4 of A - F). This might be fine if the armhole was more of a U shape in the front, but as it hooks to the left about 2 cm to 2,5 cm more than more modern patterns do, the chest piece doesn't have enough material to allow for the sleeve to  gather there nicely for the seam to fold over itself neatly.

To state the obvious, do what's required to make it work. Make the armhole more U shaped; add that little more chest width. It doesn't matter what the original draft tells you to do. Body shapes are different now and require a different approach. For all we know, the original looked awful.   

As you can see, I am somewhat lost here when it comes to how modifying the sleeve draft affects how it sits with the body of the blouse 

I'd advise to watch some draping videos on youtube. They'll help you to get a better idea of how to fit a sleeve that isn't working for you. So long as there's plenty of inlay, you can pin the sleeve until it looks right (following basic draping principals for fitting).

At the end of the day, all ready-to-wear garments, and all sewing patterns, are tested on real individuals to finalise the patterns. As I said earlier, drafts are only there to get you up and running. The skill is in the fitting. If you're trying to figure out a drafting system that can do all that for you, you're on a hiding to nothing. Perhaps in the future, when body scanning takes out all the guess work, our current knowledge of cutting and fitting will be redundant. Until then though ...

[TTailor]

I will have a look through your questions but not til later this week as I am swamped at work.
One question is whether the draft you are using includes seam allowances, is it indicated anywhere?
Can you post the whole draft and the instructions?

I have used Seamly 2D as well.
I think drafting on paper is easier in some ways and can be a great help when trying to translate by drafting to a digital system.

[Lieckio]

Apologies for not having read your post more thoroughly (I only glanced through, if I'm truthful).

No need to apologize! I hope I am not coming across as annoyed by what you posted! On the contrary!

My brain is perhaps a bit overworked with this whole thing, which probably shows in what I'm typing here

I didn't mean that the height is irrelevant in this case, I meant that in general it's a secondary thing. As you say, a shorter cap gives more ease, but isn't as clean as a higher cap where the opposite is true (less mobility, but cleaner). Once the style has been chosen, then all we're concerned about is matching the cap length with the armhole circumference. In that sense, the cap height is irrelevant.

Ah, right, I misunderstood what you meant originally. I believe we agree and are on the same page in this point

I shall stress less about the cap height from now on, as long as the sleeve sits neatly.

To state the obvious, do what's required to make it work. Make the armhole more U shaped; add that little more chest width. It doesn't matter what the original draft tells you to do. Body shapes are different now and require a different approach. For all we know, the original looked awful.   

This is a fair point as well. I am tempted to modify the front piece shoulder line towards more of a U-shape, if I don't get the sleeve to fit all nicely with the these tricks. If not for anything else, but to see if there is a difference there.

I'd advise to watch some draping videos on youtube. They'll help you to get a better idea of how to fit a sleeve that isn't working for you. So long as there's plenty of inlay, you can pin the sleeve until it looks right (following basic draping principals for fitting).

I've been roaming Youtube and blogs for weeks now, trying to find some sensible videos and/or information about this but I don't seem to find anything that would actually tackle any of these issues I have. Or so far it has felt as if all the videos talk about some different issues that I am not having.

At the end of the day, all ready-to-wear garments, and all sewing patterns, are tested on real individuals to finalise the patterns. As I said earlier, drafts are only there to get you up and running. The skill is in the fitting. If you're trying to figure out a drafting system that can do all that for you, you're on a hiding to nothing. Perhaps in the future, when body scanning takes out all the guess work, our current knowledge of cutting and fitting will be redundant. Until then though ...

This is true, and I don't want to come across saying I need to make a perfect replica of the diagram in the drafting guide. I will eventually probably adjust some things, like the back/waist circumference and chest circumference to have a bit more extra space there for the modern body, as well as the shoulders.

Thing is, I've been commissioned to make replicas based on an existing size table, so there is only so much I feel I can do without going outside the "accuracy" of replicating the blouse.

I guess, to sum it up, I am trying to achieve at least one standard draft (basic... 1930's blouse block, I guess ) for my use that I can then use to make the required sizes and/or alter and customize as needed. Right now I have sort of a... partial pattern, where I don't fully understand the logic behind it. And if I alter this pattern that has errors in it, the errors tend to compound. And I can't do this separately for all the individual sizes unfortunately... I'll run out of time, or my health will give up before that

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I will have a look through your questions but not til later this week as I am swamped at work.
One question is whether the draft you are using includes seam allowances, is it indicated anywhere?

Thank you for taking the time!

The draft *probably* includes seam allowance of 0,6 to 0,8 cm, except on the waist seam and hem and the lines outside CF are hinting on the size of the hidden button placket etc. Those don't include the seam allowance.

The reason why I think it includes that seam allowance is that that would make sense based on my toiles - and there's two sentences hinting on that in the guide itself, though it's not exactly obvious (and the original writing is cumbersome to translate and understand even for a native speaker):

The edges are stitched with a narrow seam, seams [or stitching] about 0.5 cm, and the hem is 1.5 cm wide. Extra allowance is added to the seams as required by the fold and stitching.

Based on what I'm seeing in the originals is that there's a lap-felled seam that's about 0,6 to 0,8 cm wide and they've been stitched with a double needle stitching machine with the stitches going about 0,5 cm apart.

It does not however have all the extra seam allowance that a lap felled seam requires and frankly I am not sure if I am supposed to add that evenly to both sides or just one side. As apart from this, seam allowances are not mentioned anywhere else and I've yet to meet anyone who knows exactly what the standard practice of the period was in Finland.

Can you post the whole draft and the instructions?

I'd rather not, as I had to spend conciderable time searching for these in the National Archives and I'd rather "keep them to myself" so to speak. Also I am not exactly sure what the copyright status for them is, even if nobody really is going to sue me for copyright infringement here... I guess.

I could message the translated drafting guide to you privately though, if that helps?

[Gerry]

I've been roaming Youtube and blogs for weeks now, trying to find some sensible videos and/or information about this but I don't seem to find anything that would actually tackle any of these issues I have. Or so far it has felt as if all the videos talk about some different issues that I am not having.

I appreciate that the following is for a different type of sleeve (more vertical drop/longer cap), but the basic principles apply. In your case you already have the sleeve drafted, so it would be a matter of leaving significant inlay around the cap and pinning things as shown. It's just another way of tackling the problem (though I appreciate that draping is not for everyone).

https://www.youtube.com/watch?v=ECzlDBHa0qc

That aside, if you post some photos of you/someone wearing your toiles, that will better demonstrate the problems you're finding; and you'll be sure to get more input from the experienced fitters here.

[Lieckio]

I've been roaming Youtube and blogs for weeks now, trying to find some sensible videos and/or information about this but I don't seem to find anything that would actually tackle any of these issues I have. Or so far it has felt as if all the videos talk about some different issues that I am not having.

I appreciate that the following is for a different type of sleeve (more vertical drop/longer cap), but the basic principles apply. In your case you already have the sleeve drafted, so it would be a matter of leaving significant inlay around the cap and pinning things as shown. It's just another way of tackling the problem (though I appreciate that draping is not for everyone).

https://www.youtube.com/watch?v=ECzlDBHa0qc

That aside, if you post some photos of you/someone wearing your toiles, that will better demonstrate the problems you're finding; and you'll be sure to get more input from the experienced fitters here.

That's an excellent video! I'm going to have to take a look and see if I can get something like this to work!

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On another note, I found - purely by accident while browsing Pinterest - a sleeve draft that matches the originals almost 1:1. It is from a M. Müller & Sohn, but Pinterest being Pinterest I have no idea what book it is from.

I might have to email them and ask if they can tell me which book it is from so I can buy that for my collection.

EDIT: Well that was easy, it is HAKA Schnitt-konstruktionen Historische Schnitte, which is available at their webstore right here: HAKA Schnitt-konstruktionen Historische Schnitte

[TTailor]

I could message the translated drafting guide to you privately though, if that helps?

Sure, that would help.

[Lieckio]

I've sent the translation

[TTailor]

Just trying to parse through your questions and I printed out the information you sent.

"Draw the bottom and the front of the armhole curve 1 cm outside the guidelines."

This is done so in the example as well. However, I am totally unsure as to how to define the shape of the curve correctly, especially so that it matches the backpiece. The point 7 is said to be "halfway between U and E minus 1 centimeter".

Thats just to give you a lateral point between U and E

However, the armhole curve in the front "cuts off" at a seemingly arbitrary spot, same goes for the backpiece curve. The length of the side seam is equal in both 7 - 6 and 7 -3 if I place the points in the sample draft at the same spot, but the curve is not a flush, matching curve. However, if I move the backpiece as is to the seemingly arbitrary spot of the sample draft, the curve matches. I suspect that the intersection point of the front and backpiece is somehow related and ought to be able to be calculated/drawn, it just isn't clear to me how. Below is image of what I'm trying to explain here.

As for the side seams themselves, they need to be the same length for sewing and in the diagram the front point 7 looks like it might be slightly longer as it seems to be drawn up to the chest line.
It is possible that the front side seam is longer on purpose and it is eased to the back side seam to provide a bit more chest shaping. I have seen it mentioned in other old texts. Does it provide much shaping, who knows? 
Since there is waist suppression in the side seam, the drawn curves of the armhole just need to flow nicely when you place the side seams together as they will be sewn. On paper I would just place them together and check that the armhole run is drawn  nicely, coming down below the chest line as described in the text and curving in front of line M-E and above point Y. They don't tell you exactly where the armhole line crosses the vertical guideline because they just expect you will know how to draw a good shape.

on Seamly I think you will have to use a pivot tool to place the side seams together to see what the armhole run looks like and then modify the curve as needed (probably easier to do on paper first then calculate for Seamly).