Resizing to make a mask question....

If you've got a printer that enlarges and reduces by specific percentages, or access to a copy machine that does so, the arithmetic problem is pretty simple.  (If it wasn't, I wouldn't be able to do it.  The last math course I took was in high school, forty years ago.) 

It all depends on the fact that the concept of percentage is based on the number 100.  And working the problem will be easier (and less subject to mistakes) if you've got an electronic calculator that works in feet, inches, and fractions of an inch.  (Such gadgets used to be rare, but nowadays you can pick one up at Lowe's, Home Depot, or Wal-Mart for less than $10.00.  It will quickly turn into one of the most useful tools on your workbench.)

Let's use the example in New Hampshire's post.  The drawing on the instruction sheet is slightly larger than the model, so the drawing needs to be reduced to something less than 100%.  You want to reduce an object that's 5 15/16" long to 5 3/8".  So set up the equation:  5 3/8" over 5 15/16" equals X over 100.  (Sorry for the verbiage; this program doesn't do so well with mathematical stuff.)  According to my fourth-grade teacher (this was back in the days of the Old Math; things may well be different now), the way to find X in a problem like this is to "cross-multiply."  (The product of the numerator on the right and the denominator on the left is equal to the product of the numerator on the left and the denominator on the right.)  So 5 15/16" times X equals 5 3/8" times 100.  

Work those numbers on the calculator (like the one I keep by my computer):  5 3/8" times 100 equals 537 1/2".  Now divide 537 1/2" by 5 15/16".  The answer is 90.526315.  So 5 3/8" is 90.526315 percent of 5 15/16".  Copy the drawing on the instruction sheet at 91 percent (that's 90.526315 rounded to the nearest whole number), and the drawing should match the model.  (If it doesn't quite match, try 90% or 92%.  Not all copiers are perfectly accurate when it comes to such things.)

All that takes at least ten times as long to describe as it takes to do the actual calculation (with a calculator).  I wish I had a dollar for every hour I used to spend at the local copy center, pounding numbers into that little calculator (which, amazingly, still works these many years later) and transferring the answers into the copy machine (at a dime per copy).  Nowadays I just key the numbers into my Epson desktop printer/scanner/copier (about $125 at Sam's Club, and one of the best expenditures I've ever made).

Hope that helps.  Like I said, it's actually quite easy; it takes longer to read the explanation than to work the problem.  Good luck.

THANK YOU!  That indeed makes perfect sense and helps A LOT!  Again, THANK YOU!

I knew it had to be something simple.

Brian

I guess that's true.  Personally I've never been able to make myself "go metric"; I'm too accustomed to working with drawings, specifications, etc. that are based on the English system.  But for this particular purpose millimeters would work fine.

The Radio Shack "Decimal-Fractional Yard-Foot-Inch" calculator that I have in front of me cost me about $35.00 back in the late eighties.  My father, a retired architect, was in awe of it; he'd spent his career converting fractions of inches into decimals.  Shortly after buying that calculator I bought another one (slightly cheaper) that converted between English units and metric ones.  Some weeks ago I found a gadget that would do both (among many other functions) at Wal-Mart for $7.95.  I keep it in the workshop and the old Radio Shack one on the drafting table; both get a lot of use.

For a while some company or other was marketing a gadget called "Model Calc," a calculator specifically designed for modelers.  It had lots of scale conversion factors (including the oddball railroad ones, like HO, N, and Z) built into it as constant keys.  Haven't seen one of those in years; it was a nice idea, but nowadays there are plenty of cheaper calculators that will do all the same things.

nowadays there are plenty of cheaper calculators that will do all the same things.

And they beat the heck out of working it out on a slide rule!

Sometimes, the things we learned, that we thought we'd never use, are the things we need the most. 

sumpter250 wrote:

nowadays there are plenty of cheaper calculators that will do all the same things. I pretty much rely on the one that came free (so to speak) with Windows. Sometimes, the things we learned, that we thought we'd never use, are the things we need the most.

My parents forced (and "forced" is the operative word) me to take typing when I was in high school.  The class was a bore (I was the only boy in it - and that fact, in those days, didn't please me particularly), and the teacher, I think, was a borderline wino.  But I learned the keyboard, and though I consider my current typing skills marginal they're good enough to let me type my own stuff at the office.  (Among the many valuable pieces of advice I got from my university-professor father was:  "Never ask a secretary to do anything you can do yourself."  That's always been my policy, and I've never regretted it.) 

One math teacher, one physics teacher, my father (architect) and my brother (zoologist) all made valiant efforts to teach me the use of the slide rule - with remarkable lack of success.  

As one of the assignments in my introductory museum studies course nowadays I make the students write "artifact analysis" papers.  The assignment is to pick some historical artifact and write a paper that describes it in detail and analyzes what it is, where it came from, how it was used, and what its cultural and societal significance was.  A few years ago one of the students wrote his paper about a slide rule, which his grandfather had given him.  None of the other people in the class had ever seen such a thing.  A year or so later, a student did her paper about an LP phonograph record.  The students had seen such things, but few if any of them had ever actually heard a vinyl record.

I feel old.  Time to go to bed.

About ten years ago I showed my daughter one of these at my studio, and asked her what it was. She's eighteen now.

"That's an erase icon". But I guess at this point that even dates her!

It's funny about zooming in/out plans. It doesn't come as a surprise to me because I've been in the business of drawing things for 35 + years, but a "scale" drawing is usually anything but that. Usually it's really a configuration drawing, allowing a technician to assemble an item in it's correct configuration from other smaller assemblies. A good case in point is a frame house. The drawings certainly don't show where all the wood goes, they just show the end result. And they'll never show all of the possible conditions, the carpenter makes 'em up. Obviously an Airbus or the USS Vella Gulf don't go together that way, but it wasn't so long ago....

I use visual scaling whenever I blow-up plans. I have the luxury of free copies, so I can hit/miss, but I'll use math just to get in the ballpark, then tweek the final size by putting a scale to the copies. I recently used the side view from a decal sheet for a PBY Catalina with a "aftermarket" rudder to make a pattern for the new vertical control surface. The fuselage half of the model I am using is 10 1/8" long, so I ran a couple of enlargements until the copy measured that long too. When I placed the piece of plastic over the copy, nothing else matched except the OA length. Both hull steps, the position of the wing pedestal, you name it!

Bondoman,

That thing is a sanding block.  It is for wrapping small chunks of Flex i grit for sanding gentle curves around a shup's hull, or such.  I have had a couple of big Pink Pearl erasers in my tool box for man, many years now, and they don't look pretty anymore.
Rick

I recently received this email from a friend who is second mate on a containership. I have shared it with several other retired people to show what a good choice we made to get out of the business when we did.

"First, you have to keep the fathometer on all the time otherwise it sets off the alarms on the VDR.  (For you, Mr. Retiree, that would be the Voice Data Recorder.  The maritime "black box", and if the ship sinks the capsule it is enclosed in floats free via a hydrostatic release.)  It is not uncommon for the fathometer to sound a minor alarm several times a watch.  Very short, very minor sound.  It is the EPFS alarm and have now forgotten that acronym.  "Electronic Position Fixing Something", but it is not related to the GPS.  Some signal is not getting to it.  Who the hell knows.  (Remember when we used to "arm the lead?")  On the fathometer display itself, the EPFS alarm is also displayed

Away, this minor alarm goes beep, beep, beep for a few moments on the fathometer and the Lat and Long display on the radar changes color for the briefest of moments, in addition to the EPFS warning appearing in the "warning" section of the radar.  Again, it is not a GPS failure, though.  As mentioned above, this happens off and on through most watches and is no big deal.

A few nights ago the alarm goes on as usual, but does not go off.  The usual display on the radar goes off as well.  Next thing you know the alarms on the VHF radios, AIS and all the GMDSS units at the GMDSS console go off as well.  All the "DATA" displays on the radars are flashing spasmodically as well.  Whatever this alarm is, and now wont go off, has activated alarms on all the equipment, pretty much, on the bridge.  Again, whatever the hell this is all about, it is not about the GPS.  Hell, the GMDSS has it's own GPS units.

While the fathometer audio alarm is a gentle, soft alarm, the rest of this trash is piercing and I can not silence any of them, only the fathometer.  Had the ship been in Asia, shoulder to shoulder with traffic, it would have been a pain in the ***.  Whatever this alarm is to the fathometer, why is this signal going to all the rest of the equipment that has no "connection" to the fathometer?  Just because they can, I guess.  Everything is integrated now, you know.   I had to endure this for about 20 minutes until whatever EPFS signal was missing was restored.  

Might have been able to have silenced everything just by turning off the fathometer, but that, in turn, sets off another set of alarms on the VDR.  This is the maritime industry in the 21^st century.  Glad I won't live long enough to see it in the 22^nd century."

Oh, for the days when you could go anywhere in the world with this, plus a stack of HO 214s and a Nautical Almanac.

Fred 

Fred, if I'm not mistaken, those four objects on your modeling bench from right to left are a scriber, a cutting straightedge, a protractor and an optivisor, correct?

I glanced through the paper this am over the first cuppa, and saw where two nuclear subs collided. THAT must have set off some bells and whistles....