Scale size questions

[Desertanimal]

Is there a quick method you guys and gals use when scratch building an item to figure out the size? 
I use a scale calculator online right now. Down side to do that is I need to find my phone, open the web etc. 

I’m fairly good with math but for some reason this scale thing gets twisted in my head. 
As an example I’m working in 1:12 on the sailing pram. I wanted to know what 1” was. Found out it’s just shy of 3/32 and close to 2mm. I thought hmm, I should write that down so I’ve got a cheat sheet of common sizes. 

Is there an easier way? 
 

Thanks!

 Chris

Edited June 5 by Desertanimal

[tmj]

You need to know the actual size of the real subject that you are modeling in scale. In your case, if I understand your question properly, 1:12 means that every part you make should be 1/12th the size of the real subject's part. For example, if you wanted to know how long a 100-foot-long item would be if modeled at 1:12 scale you would simply divide 100 by 12. The length would be 8.3333 feet in length.   

[Desertanimal]

Haha 👍

 I do believe you just solved it for me. I didn’t realize I could replace the “1” with the item I’m working on! Units are the same regardless, mm, inches, whatever. I just need convert the decimal to whatever I’m working in.
 

Thanks !!

[robert952]

Sounds like you have solved the matter. However, to add to the tool kit, I used an app called Scale Converter by Scalar Pink.  Available on Google app store.  It doesn't solve the problem of having to find your phone. However, it is self contained and doesn't require a web connection to use. It does other functions I have found useful including mm to inch, and decimal to fractions.  

[Desertanimal]

That actually sounds pretty helpful. Especially since I’ll switch units willy nilly, whatever fits the situation best. 
 

Unfortunately doesn’t look like it’s available for Apple. I’ve loaded one by woodland scenics. It’s not rated very well but they’re pretty simple. 

Edited June 5 by Desertanimal

[wefalck]

Well, in old days I had small pocket calculator on the bench. Now, that the iPhone is always near me, I use its calculator - that's the simplest and fastest option. For converting imperial into metric measures or vice versa, you just need to remember that 1" = 25,4 mm. Converting metric measures into fractions of an inch is not straightforward on normal calculators, while the opposite is easy.

[druxey]

A good ol' fashioned scale rule works for me most of the time!

[tmj]

8 hours ago, wefalck said:

Converting metric measures into fractions of an inch is not straightforward on normal calculators, while the opposite is easy.

I personally never use fractions, ever... only decimals even with the metric system. Fractions are sloppy, 4 place decimals are extremely accurate.  

[tmj]

8 hours ago, druxey said:

A good ol' fashioned scale rule works for me most of the time!

Hello David!

I have a question that might be beneficial to all parties involved within this topic. Scale rules, calipers, tape measures, CMM machines, lasers... whatever measuring devises one wishes to use. 

I personally struggle with line thicknesses when trying to take accurate measurements from printed drawings, blueprints, etc. 'especially' when the ink on those drawings varies in thickness, ever so slightly, from one area of the drawing to another. I'm not sure if I should shoot for taking dimensions from the 'perceived' middle of the lines, inside of the lines, or the outer most boundaries of those lines. I like to measure with calipers and then transfer those measured dimensions to CAD drawings, however. When doing this, those slight variations in line width often tend to cause problems with creating smooth geometry within my cad work. I discovered this back when I first started the design work for my 'Hancock' build (still at it, haven't given up, just a slow go). I've found a way to fix this, visually, but in such it always bugs me not knowing if I'm actually pulling the proper dimensions, or not, via my smooth looking visual modifications that correct the once awkward and slightly crooked looking CAD geometry. I know that I'm probably splitting a lot of hairs here, but in such I'm also curious as to just how one should best approach taking accurate dimensions from hand drafted drawings without encountering errors due to line width variations?         

[druxey]

That's a great question. The best plans are drawn with hair's width lines.This minimises the issue that you mention. Of course, in CAD you can magnify to a size that will drive you crazy! If you want to go the CAD route, might I suggest that the base drawing be redrawn from the 'fat line' plan first, then imported? There will always be some compromises, or you will lose your mind.

[Cmm4000]

I know this has probably been posted before these are awesome.

https://www.blocklayer.com/scale-ruler

[tmj]

5 minutes ago, druxey said:

Of course, in CAD you can magnify to a size that will drive you crazy! If you want to go the CAD route, might I suggest that the base drawing be redrawn from the 'fat line' plan first, then imported? There will always be some compromises, or you will lose your mind.

You are quite correct. The first couple of months, after starting my frame drafts for the Hancock, I was losing my mind on a regular basis. I'd get frustrated, delete my work then start over again, time and time again. I've lost count on how many times I started over with a clean slate. I finally came to the conclusion that I was being a bit too anal about being 100% accurate and started keeping my work and making adjustments as needed, be it truly accurate or not. Maybe my work will be off a few scale inches in length, breadth, and this/that and the other, here and there, but "What the Heck." It became time that I either had to stop trying to be completely accurate and start focusing on just getting things as close as I can, otherwise I'd never finish my design nor begin to actually start building a model. I'll blame this behavior on my 40-year background and career where .005" could mean the difference between "Go, or 'No Go'!" From now on I'll just try to stay as close as I reasonably can and simply focus on a nice-looking design. If something is off a bit, nobody will ever know but 'me'!

Okay, I've highjacked this thread for long enough. Time to return it to its original owner...       

[druxey]

Yes, please stay sane. I can work to ½" a scale inch at 1:48 scale. That's 1/96" or just over 1/100". Not .005", for sure but that's the difference between the two states of mind.

[Dr PR]

For older wooden vessels no one will ever know what their dimensions really were. They were built from experience, not accurate drawings. This is especially true for the hulls. They were built on the ways piece by piece and often the parts were hammered into place to fit with all the other pieces. The frames were fared with battens, not rulers, and certainly no two hulls were the same dimensions exactly.

 

So don't sweat the small stuff!

 

There is one trick that I have learned. For things that have straight lines or regular arcs/curves the designer/builder was working in some type of measurement units (inches, millimeters, etc.). You don't make something like a cabinet, deck house or hatch by just slapping together random pieces. So if the measurement you get from your drawings comes out to 10.082 units, it is probable that it should be 10.000 units. When I was making my CAD drawings for the USS Oklahoma City CLG-5 I found that the designers worked in common fractions of an inch - 1/16, 1/8, 1/4, 1/2, etc. So when photoguesstimating dimensions from photographs I just rounded off to the nearest fraction and things fit together pretty good in the drawing.

 

A real problem here is that an older European vessel may have been designed to the inch/foot, but was it the English inch, or the French, Dutch, Danish, Swedish ... inch? They were all different!

 

Another trick you can use when you don't know the actual real world dimensions is to use "relative units." For example, in a drawing/photo make the hull length at the waterline 100 units. Then measure things relative to the hull length. How many relative units back from the bow was the fore mast, main mast, etc.? How tall were the masts in relative units? Just make your CAD drawing in relative units and everything will be in proportion. Then, if you learn the actual dimensions of any part you can rescale the drawing to make that part the right size in real world units, and everything else will also be the right size.

[wefalck]

The problem will be exacerbated when you work from scanned original drawings. Every line that is not absolutely aligned to the axis of the scanner will become a fuzzy, jagged something.

 

There are a few strategies to overcome the problems discussed above:

 

- never ever use chain measurement. By way of example, it you have a row of identical boxes fitted to each other, don't measure each individual box, but measure the overall length and divide it by the number of boxes to give you their dimensions. 

 

- Similarly, when drawing plans for a ship, do not start from the details, but from the overall dimensions and fit the parts in. The percentage lengths mentioned by Dr PR above go this way.

 

- Think about the practicalities of building: what materials and what tools do I have available or can obtain; dimension parts accordingly, if the deviation would not really by visible.

 

- Think also which part would the easiest to make fit to other parts; say you have to make a flange for a pipe, in which case you may fit the inner diameter of the flange to the available wire/round stock; the inverse, could be also the case for bigger parts, where it may be easier to turn the pipe to the diameter of a flange for which you had a drill for the whole; etc.

 

- Unless I would make a drawing for publication, I tend to make no real drawings for parts, but rather (computer) sketches to which I add the measured/calculated dimensions; I then work from the numbers, rather than taking off another set of measurements from a drawing.

 

- Work from parts with well-known dimensions; say, you need to construct a shell-locker, then start with the dimensions of the shell, which typically are very well documented in the literature of the time, etc.

 

[davyboy]

Quite an interesting read. I work in Imperial at 1:48th scale. A foot is 0.250"at 1:48th,an inch at 1:48th scale is 0.021",actually it is 0.0002" less but I use the 0.021" as I'm building a model ship from wood not a million Franc watch.  Easy enough to work out whatever scale one uses in imperial or metric I guess.

 

Dave