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errors in blueprints


BETAQDAVE
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    When the dimensions of a ship are given, they are stated as moulded dimensions.  For example, the New York Pilot Boat "Phantom" is listed on Model Shipways plans as shown here:

              Length overall (moulded) 76'-4" (Assuming that this is measured from the face of the stem to the stern end of the deck.)

              Beam moulded 19'-8" (Assuming this is the maximum width)

              Draught 10'-8" max.  (Assuming this is measured from the waterline to the bottom of the keel.)

    Here are some photos of the ship plans to help illustrate my confusion with several discrepancies that I have come across.

100_4325.thumb.JPG.545d07892c66c67300b8be05f016a724.JPG100_4326.thumb.JPG.c1b061a8218b2917d037bc50a4d394a2.JPG100_4329.thumb.JPG.4f74e95d3073899ff70edabcf470382b.JPG

     I have put notes on the plans where I have come across some errors, but the first and most glaring error (shown above) is that the overall length on all of all the deck and side elevation views measures about 1’-8” short of the previously stated dimension.  One might say that the error is in the reproduction of the print, but if you measure the beam dimension off of the same drawing of the deck plan, it is very close to the stated dimension. Stretching out the length of that drawing would now make the beam dimension incorrect!

 

    There is also a scale drawn below the waterline plan.  When I put my 1/8” architectural scale on this printed scale, (shown below) you can plainly see that they don't come close to matching either!

100_4323.thumb.JPG.5036ab17234f09a92db2d74343e85e4c.JPG

 

  If I put the same architectural scale on the waterline, profile elevation, or deck plan I have the same situation, and yet when measuring the beam section drawing below, the scale matches exactly!  

100_4324.thumb.JPG.cd7d4ac4f1c80d1f8ce3fc1f12f00e23.JPG

 

 

    Now that I have decided to build this ship @ 3/16” scale, I obviously need to have the plan enlarged some more.  However, all of the plans seem to be drawn at different scales.  If I enlarge one, the others also get enlarged the same amount.  So the error would continue, but just at a larger size.:default_wallbash:

     Having made the decision to use a somewhat modified bread and butter method of construction, the accuracy of the profile section drawing becomes quite important, and when my scale is used to measure this drawing you can see that it is right on the money. Oh but wait a just a minute here. That would mean that the ship is really wider than what the other drawings show!:o  This leaves me a little confused as to which drawings are drawn correctly and which ones are not.

     Oh, and by the way, this also brings up yet another question.  If the ship length is short.............. does this missing 1’-8” need to be added to the bow, the stern, or somewhere in between?:huh:

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Dave we were given quite a revealing presentation about 2 years ago by a modeler who had developed a plan, defined the materials set and wrote the construction manual for a model available on the market today. The creator related that it was an iterative process in which he saw numerous deviations in many aspects of his design. A number of the deviations were with the manufacturing process i.e compromises in parts for whatever reason. He took much heat from the community at large for the deviations.

 

Why do I bring this up? Older kits and their drawings suffer some of the same ills, possibly more. Supposedly prestigious archival drawings and renditions in some repositories have been challenged by researchers. I came across this on my abandoned build of the Corel HMS Unicorn. When a design is reduced to a kit there are so many ways things can get out of wack that it isn't even worth listing them. Presently, I am working on a 1980's era model, a very expensive one, and I am finding drawing errors, omissions and the like.

 

We all have become more astute at this pass time and have imposed higher standards on what we accept as "bible". My advice to you is to establish a datum with the body plan. Let the given dimensional data guide you on what you pick as the reference. Have the drawing scaled to meet those dimensional requirements. Redraw/recreate the profiles to the correct scale if you need. Corel Draw is a handy way to get you there as you can scan in the profiles and manipulate them. Of course there is always the research avenue to aid you in resolution of inconsistencies. Perhaps the Peabody Museum may have some drawings you may avail yourself to as I see a reference on the drawing to East Boston.

 

Joe

Edited by Thistle17
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Using published dimensions and checking plans can be tricky.

What was meant by length changed constantly over time.

Was it length of keel? Was length of keel "touch"? (17th C.)

Was length on gun deck (or main deck)? (18th C.) Was it

length between perpendiculars?  And where exactly are the perpendiculars placed?

There was a change in the mid 19th C. because I have Chapelle plans with notations

about "old" measurements and two locations at the bow.

 

In your place, I would drop back 10 and punt on the MS plans.

I would start with the plans the John Shedd and Co. probably used to develop theirs.

Howard Chapelle has plans for Phantom in HASS and thus 1/4" scale lines are available

from The Smithsonian.  I did not check, but usually these are builders plans and are inside the planking.

Some of The Smithsonian plans are off absolute scale by ~1% or so - and if you use your 3 in 1 to copy

and a drawing/paint program to scale - your scanner will not give your an accurate copy.  Mind requires

scans to be scaled up 102.5%

 

Given your proposed method - if you intend to fully copper the bottom, and do not wish to plank under it first,

the planking thickness can be added to the lines up to the copper line -if you were doing POF or POB or cross sectional (sliced bread) 

bread and butter.  For waterline bread and butter or solid hull, I do not think I would attempt the complex geometry that

adding the planking thickness would involve and would just plank it.

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I have come across all the issues identified above; but two critical are the reproduction printing process and the drawing program to begin with. I discovered the reproduction process when getting CAD drawings size D (22 x 34)reproduced for a build. The local printer did not reset the printer from a previous job and my drawings were printed at a 105% setting. Once discovered I took the drawings back and they zeroed the printer at 100% from then on on all my drawings I draw a 1 inch reference square and I tell the printer to verify the size on printing. I have not had a problem since. Also make sure the printer is using a large format printer capable of size E (34 x 44) drawings. Smaller machines when forced to a larger size often have distortion issues. Much like camera distortion in photographs.

 

The second issue is the CAD versus Drawing program. While a drawing program is exactly what it says it is to be used for....drawing. CAD programs are for engineering drawing to at least four decimal points or more if needed. The best example to explain he difference is comparing both to a road. A drawing line is the size across the road from berm to berm while the CAD program set a .5mm line weight is like the stripe down the centerline. Admittedly, CAD programs are more expensive with a steeper learning curve versus the drawing programs. The old adage comes into play " you get what you pay for" and if accuracy is of major concern one needs to start with a good CAD drawing. One can still have errors with CAD but that usually is now human operator error not the program. As technology has evolved with 3D printing and laser cutting machines for hobbyists, to appeal to more they can use drawing files to work with their machines which usually have some form of conversion program to work. 

 

As a parting comment I would say that we are building models that probably will sit in a case and never be measured for comparison to another and can only be as good as the reference material we are building from. My experience has been that all kits and plans have accuracy issues and common sense adjustments are required and enjoy the build process. 

 

 

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In times past, naval architects attempted to deal with paper distortions by the use of a graphic scale on the drawings.  All of Chapelle’s drawings include such a scale allowing measurements to be picked off the drawing.  As real ships built in the later Nineteenth Century were lofted, drawing distortions would be likely picked up and corrected then.  This lofting process means that when we build a model from a design drawing we are building an approximations of the real thing as we usually don’t know what changes were made in the mould loft. For example, the depth of the Great Lakes Schooner Clipper City was increased 18in during lofting.  Many of Chapelle’s drawings were drawn from lines lifted from half models in the Smithsonian’s watercraft collection that may be different from the real thing as hull lines could have been changed during subsequent lofting.

 

Roger

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  • 1 month later...
On 2/23/2018 at 11:59 AM, BETAQDAVE said:

    When the dimensions of a ship are given, they are stated as moulded dimensions.  For example, the New York Pilot Boat "Phantom" is listed on Model Shipways plans as shown here:

              Length overall (moulded) 76'-4" (Assuming that this is measured from the face of the stem to the stern end of the deck.)

              Beam moulded 19'-8" (Assuming this is the maximum width)

              Draught 10'-8" max.  (Assuming this is measured from the waterline to the bottom of the keel.)

    Here are some photos of the ship plans to help illustrate my confusion with several discrepancies that I have come across.

100_4325.thumb.JPG.545d07892c66c67300b8be05f016a724.JPG100_4326.thumb.JPG.c1b061a8218b2917d037bc50a4d394a2.JPG100_4329.thumb.JPG.4f74e95d3073899ff70edabcf470382b.JPG

     I have put notes on the plans where I have come across some errors, but the first and most glaring error (shown above) is that the overall length on all of all the deck and side elevation views measures about 1’-8” short of the previously stated dimension.  One might say that the error is in the reproduction of the print, but if you measure the beam dimension off of the same drawing of the deck plan, it is very close to the stated dimension. Stretching out the length of that drawing would now make the beam dimension incorrect!

 

    There is also a scale drawn below the waterline plan.  When I put my 1/8” architectural scale on this printed scale, (shown below) you can plainly see that they don't come close to matching either!

100_4323.thumb.JPG.5036ab17234f09a92db2d74343e85e4c.JPG

 

  If I put the same architectural scale on the waterline, profile elevation, or deck plan I have the same situation, and yet when measuring the beam section drawing below, the scale matches exactly!  

100_4324.thumb.JPG.cd7d4ac4f1c80d1f8ce3fc1f12f00e23.JPG

 

 

    Now that I have decided to build this ship @ 3/16” scale, I obviously need to have the plan enlarged some more.  However, all of the plans seem to be drawn at different scales.  If I enlarge one, the others also get enlarged the same amount.  So the error would continue, but just at a larger size.:default_wallbash:

     Having made the decision to use a somewhat modified bread and butter method of construction, the accuracy of the profile section drawing becomes quite important, and when my scale is used to measure this drawing you can see that it is right on the money. Oh but wait a just a minute here. That would mean that the ship is really wider than what the other drawings show!:o  This leaves me a little confused as to which drawings are drawn correctly and which ones are not.

     Oh, and by the way, this also brings up yet another question.  If the ship length is short.............. does this missing 1’-8” need to be added to the bow, the stern, or somewhere in between?:huh:

Looking great! I'll be keeping an eye on this one for sure :) Sargon

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