

Joined May 2012
1,175 Posts

Discussion
3 Views are GREAT, BUT ....
There are a BAZILLION three view drawings of aircraft around ... so abundant they almost cover the landscape like fallen snow.
For some of us, the problem is that almost ALL of them lack ANY measurements or even a simple scale that would help figure things out. Could somebody wack together an explanation how they go about working out the dimensions of these things? Also ... maybe someone could explain how to take a 3 view and turn it into a 1/24 (or 1/4, 1/32 ... or any other scale) model. I'd do it, but as anyone who has read my posts before ... I am FAR to "wordy" to do the job. If I write something as big as the rules of the road for this forum ... admin tells me they're gonna have to get a 40' box trailer to haul around the needed band width. 




Re rescaling three view drawings.
I have a CAD program, DesignCAD, which has a scaling option on it. I down load the three view, generally as a pdf file and copy it into the DesignCad screen. I get the real full scale dimensions from the web or other source and work out the scale needed to go from the pdf "picture" to the size I want. Then comes the work of cross checking the drawing to see if the fuselage length and other dimensions are correct or need correction. After that I start overlaying real lines on top of the rescaled pdf picture. This allows me to make sure things like the left wing is a copy of the right wing etc. At some point I can forget about the pdf and work on the CAD drawing alone. You can do the same thing in free drawing packages like Sketchup. There's a whole thread on using Sketchup for designing models http://www.rcgroups.com/forums/showt...6&goto=newpost Ivor 


Joined Jul 2013
78 Posts

Scaling Drawings
Scaling and changing scale of a drawing.
The basic method if using a full size dimensioned drawing is. 1, Full size dimension divided by the scale you want to work in e.g 1 divided by 24 will give you the size in scale eg 1/24 2, To reduce from one scale eg 1/24 to 1/72, apply correction factor 24 divide 72 = 0.3334, measure a length from large drawing and multiply by correction factor 1.000 multiply 0.3334= 0.3334 or 1/3 size of the original. 3, To enlarge from one scale to another eg 1/72 to 1/24 scale, measure length from drawing, apply correction factor 72 divide 24 = 3 or 3 times the orginal size. 4, To scale from a un known scale drawing, a few assumptions must be taken a' is the drawing is accurate b' ignore line thickness The size and shape from the full size aircraft needs to be known, from this you can determine if the drawing is near or far out, by comparing length to span. If drawing has a wing span of 101.5mm(decimal is easier to work in and assuming the span has been drawn correct scale) and the real aircraft is 25 feet you convert feet to mm, i.e (25x12)x25.4, so 101.5=25feet(101.5/25=4.06) therefore 1foot = 4.06mm on the drawing from this you can measure set parts e.g the length of the real aircraft is 12 feet 4 inchs, the drawing measures 55mm, 55mm divide 4.06=13.5 ft, the length could be wrong or the span is wrong. At this point you can redo the foot size by using the length as being correct and repeating the calculations, this may take several attempts to find a dimension that gives you the best result and true foot length in the drawing, it may also mean the the drawing is NOT worth continuing with due to the amount of errors. The above method is used to draw real aircraft from photographs(there is a book on how to do this I have yet to find it) using focus points, distance, perspective etc, but that is way over my head. Hopefully this is of help on the basic's. 



As a 3view is just that, a 3view, if I want to use one as the basis for my own plans, I import it into Google SketchUp, (free).
In SketchUp you can scale the 3view to any size you want, then construct your own 3D model on top. There is a big thread on using SketchUp with loads of help, tips, and methods  Using google Sketchup for modeling... With practical examples 


Joined Jul 2013
78 Posts

removed not relervent to thread




Generally I have to trust the 3view is reasonably accurate. Then there are plenty of sites showing some basic overall dimensions of the full size aircraft to determine what scale will give the model size required.
Quite often I will decide what wing span I want the model to be, and scale the 3view to suit. It may end up at some weird scale factor, (eg 6.335:1), where some may just pick 6:1 and accept the wing span. But then I don't do 'scale', I only build models that please me and fly how I want. Super scale accuracy, rivet counting, and original paint swatch accuracy, are for others to worry about. 


Joined Jul 2013
78 Posts

removed not relervent to thread




Quote:




United States, KY, Taylorsville
Joined Mar 2010
2,287 Posts

One thing that is very time saving is to 'box' a particular portion of the 3view. A tapered wing panel has a given span but the angle the LE and/or the TE makes with respect to a datum line never changes with respect to what scale is used. Therefore all you need to do is know, in this example, is the correct length of the root chord of the section of the wing. This works the same for tapering wing thicknesses, too!
I use the grid method for curves and such. Computer? COMPUTER? I don't need no stinkin' computer! (And neither do you!... although facility with CAD is handy) 


Joined Jul 2013
78 Posts

Yes what you say is true regards to angles they remain constant when scaling, as as you state as long as you have a known width e,g cord then a size can be determined for the required scale.
The problem comes as Oddshot has stated that there are numerious drawings out there which are good bad or indifferent of the same aircraft. To get the true shape/size of the original subject all of the material available must be used to get an accurate outline to start with, this is important if you are using it as research material, building models or full size replica's. 



My two cents,
To me, the main advantage of CAD is the ability to scale correctly and to get mirror images of the port and starboard sections, be it wing shape or tail or fuselage cross sections. Finding the correct shape is always a problem as dimensions show up differently in different texts, and port and starboard wings are drawn differently, or the side view is a slightly different scale than the plan view. CAD allows you to create a vector image of each view, then you can rescale so all the views are consistent with each other, and are correct, as best you know, to the real plane. Matching cross sections becomes easier when you can scale to the CAD three view as well. I frequently find myself looking at a fuselage section and trying to figure out what the draughtsman/woman would have done at the time, without CAD or a computer to generate a curve. This does help fill in the gaps. 



My method of transferring the 3 views into something relevant is quite primitive, but doesn't require a computer science major. What I do is put a piece of paper on the wall and then calculate the size plane I am looking to build and mark the paper to show those dimensions. IE, 50" wingspan. I then using a projector project the image onto the wall until it fits the dimension I was looking for and then trace the image onto the paper. I know this sounds Neanderthal, but I have scratch built two planes this way and it works.




That's not Neanderthal, it's a time honored tradition!

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