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Use of Proportional Dividers their use in this Hobby


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Okay after quite a while of waiting I came across a very good deal on a nice German made proportional divider just got it today. it is made really well so I told myself wait a minute how do you use this thing in this hobby?. I looked on here found some uses but still not enough info for me, I went online through Google and other search engines mainly found info on their use in the artistic uses not much in wooden ship building. is there a instructional on the use of this tool at least a more precise one just for this art form?

doc

 

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I use them to calculate the widths of hull planking. Set the knob at say 5, and the width of the points at the small end will be 1/5 the width between the points at the long end.

 

So, for instance, I can measure a space for 5 hull planks with the points at the long end and then flip the divider to the short end to get the width of each plank within that 5 plank band at each frame.

 

Russ

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While I've had proportional dividers in my kit for years, I confess that I've very rarely used them. I use a drawn proportional radiating scale on paper. Much cheaper! Just find the spot along the converging outer lines that equals the space you want to divide up - in regular or irregular fashion - and mark off the divisions on a strip of paper at right angles to the radiating lines. The marks are then transferred to wherever you want them. (The example shown is for dividing a square into an octagon.)

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I thought proportional dividers were used to change the scale of your drawings to the scale of your build. Say for example your drawings are in 1/8th scale and you want to make your model in 1/4 scale. You then set the dividing screw to 2 I suppose and that doubles the size of your measurements. However todays photocopiers are so accurate that dividers are sorta obsolete. The guy at Staples gave me a pocket calculator to do the calculations to go from any scale to any other scale. I still want a set. I also have a shipmodeling book that shows how to make a set from brass, but I'm too lazy for that. BILL

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Same as with many of the other comments - have a pair (with the intention to use them for planking)  but they haven't seen the light of day :)  Tick strips have replaced that idea - Druxey, great idea on the radiating lines; just need to be very careful in producing a set to ensure accuracy?

 

cheers

 

Pat

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Sorry, but I think proportional dividers are useless in most cases.

What you are doing is take a measurement with this tool, slide and set a scale and transfer the measurement at the other end. Sounds simple?

 

The problem is that you cannot measure plank widths very well with two points, and then you are adding errors by setting the scale (which usually is a rather small slider), and again using the points to indicate where you want to make the cut.

 

Why not simply measure the plank width, for example, using vernier calipers, multiply that number by the scaling factor (using a calculator) and come up with the precise number you are looking for? For multiple planks and locations, I set up a quick table of the measurements and the converted numbers next to it.

You can then sand or file the plank width to those numbers again using the vernier calipers to verify what you are doing.

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A great Tool as with every thing spend time learning how to use them. The point on the end is much more accurate than a pencil line.  Take the over all length of your Tick strip,  set PD to # of planks needed set wide end to over all length of Tick strip now turn PD's over and march down the Bulkhead and presto your plank widths marked out for you. No more transfering Tick strip marks to bulkheads.  

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I also use them to divide up lengths into equal parts. For example, finding the quarters on a mast, or the spaces between ledges marked out on a carling. It is fiddly to set the screw at exactly the right place, so I always double check on a piece of paper. If I set it at 3, for example, I mark out a line on a piece of paper, and walk the dividers down the line three times. If it exactly lands on the end mark of the line you are set; if not, adjust slightly and try again. I find this infinitely easier than doing the math to divide a length, or the old draftsman trick of laying a scale diagonally across two lines to match even divisions on the scale.

 

Recently, I also used this to set off the diameters of masts at the various quarters. I set the proportional dividers to 2, and used the long legs to measure the correct diameter against an accurate decimal inch ruler. I could then use the short legs to mark half the diameter on either side of the center line. Much faster than dividing the diameter mathematically, and then try to set it off on either side.

 

When you realize that these ships were designed extensively with proportional systems and rules, it is kind of fun to play with the idea of proportions as you construct.

 

Mark

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I probably use my proportional divider (just like the one pictured) equal to or more than any other tool at my disposal.  I hardly ever use ruler measurements.  Anything off of the plan, or for that matter off of the ship being built, is done using these as well as a multitude of other things.

 

I can't tell you how many times I need to find an accurate midpoint or just to transfer a specific dimension from one place to another.  Planking has already been stated.  With a good pair (mine cost $80) the measurements are spot on.  I seem to find more uses as time goes by.

 

Each person has to figure out what works for them, but for me I find these simplify my life greatly - and to a greater accuracy.

 

Mark

Edited by kruginmi
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Of course, these are nice old-fashioned and very maritime looking tools. Would like to have one, but there is not much point investing somewhere between 50 and 100 EUR for a tool that in practices wouldn't have much use for me. A divider with lockable legs is a very useful tool for marking out equal distances and the likes and the proportionality function can be easily replaced by a vernier caliper together with a pocket calculator.

 

For marking out equal distance along a curved line, such as along a frame for plank widths, I would prefer the paper-strip methods described by others above. It avoids the building up of errors by measuring from succeeding end-points.

 

At the small scales I am working in the proportional dividers would also be far to clumsy.

 

wefalck 

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Mark,

 

I couldn't agree more.  Unless I have a very specific measurement need I use my proportional dividers to transfer dimensions from plans to wood or template, find midpoints been model features, etc.  As with most tools paying for quality yields accurate, repeatable results time and time again.

 

Cheers,

 

Elia

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  • 2 weeks later...

Gaetan: I agree that a top-grade set of dividers such as the one in your pictures can be very useful in certain circumstances. My own decimal set, with rack and pinion, also have the points cranked to a right-angle, so that you can lay the dividers horizontally. However, for most model-making applications the radiating scale and tick strip are more practical, I find.

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My own decimal set, with rack and pinion, also have the points cranked to a right-angle, so that you can lay the dividers horizontally.

Hello Druxey, is is possible to show a picture of what you describe. I am having a difficult time visualizing it for some reason.

I have a good quality set that I acquired many years ago, Sometimes I have noted a little creep when opening and closing them over a period of drawing. There are the register pins to reset them when closing but still it was annoying.

 

Michael

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Michael: you would need to maintain the geometry of the points in order for the calibration to remain accurate.

 

Elia: the rack and pinion move the pivot unit, so that it adjusts the proportionality. If you need to re-calibrate the instrument, you would need to loosen and slide the points - a fiddly task to avoid doing, if possible!

 

As a P.S., I've only ever seen one other set with this cranked style of point, so assume that they are rare. And, as I noted before, I seldom use them; so they remain fairly pristine!

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