Research and updates on drafting tools for ship building.


Visit to the Royal Maritime Museum

July 2017

While visiting friends in London, I was lucky enough to have time to sneak away and visit the Royal Maritime Museum in Greenwich. Most of my adventure there was spent in the library where I was researching my latest model boat building project, the yacht America (c. 1851).

While waiting for the drawings to be retrieved from the archive, I thumbed through their shelved books. A fairly extensive collection of books on model boat building was great to see, although I was disappointed that it did not include a copy of the Fully Framed Model, HMS Swan Class Sloops by David Antscherl, with whom I’ve taken several wonderful classes with.

Also searched the Maritime’s museum archive for references to Copenhagen or other naval drafting curves, but found very little additional information other than I had already come across either with google or at the New York Public Library.

But when wandering one of their exhibits, I came across this display and hurriedly snapped a picture before the security guard could chastise me for taking photographs. Labeled only as “drafting tools”, it was a pleasant surprise to find.

Royal Museum (click image to enlarge)

Pieces one through six (and perhaps 14) have shapes similar to Copenhagen curves.

The shapes labeled seven, eight and nine are similar to Dixon Kemp’s curves, although these appear more teardrop than pear shaped. Ten through 16 look like french curves, although they seem to be more broad curvatures with less sweep than typical.

Drafting triangles are labeled 17 through 19 and, unfortunately, are pretty unremarkable as they look very similar to ones you can buy today in your local art supply store, save that they are made of wood and not plastic.


Comparing Curve #54

July 2017

There seems no definitive origin of Copenhagen curves, other than obviously being attributed to the city in which they must have been developed. Collections of curves from ship builders in 1800s seem to show that curves were made on an as needed basis as templates for various ships being designed and built. So it’s surprising to me that sets of curves seem to have the same number of pieces and similar curvatures across different manufacturers.

At the same time, it doesn’t seem reasonable how there isn’t a standard so that a curve used by one draftsman didn’t have the same shape as another draftsman sitting next to each other at the same firm. Although given that the curves were used to just connect the various points of timbers along the plans, perhaps it wasn’t so necessary other than to give the actual ship builder a general sense of the curvature of the boat being built.

Here are five #54 curves from my collections of Copenhagen Ship’s Curves sets:

Five different number 54 (click image to enlarge)

When stacked, it’s easy to notice that they are all different:

Number 54 stacked (click image to enlarge)

For a more detailed view of the differences:

Number 54 outlines compared (click image to enlarge)


Radius Curves

July 2017

Often confused with Copenhagen curves, radius curves are just that: segments of a full circle with a consistent radius for their entire curvature. Sometimes referred to as railroad or highway curves, I’ve seen sets labeled either with the actual radius of the circle (usually in inches) or with radius already scaled (usually in feet).

This is not to say that radius curves weren’t used in maritime design; they are, in fact, quite helpful in nautical drafting. And in this context, there seem to be references to them as “ships curves”, in addition to their other transportation origins. Hence the confusion with Copenhagen ships curves.

The most comprehensive set I’ve found is a set of 125 different curves with an asset tag from the California Highway Department. Beyond its size, the set is quite heavy and weighs in, with box, at a hefty 25 lbs (11 kg).

California Radius Curves (click image to enlarge)

Other sets I’ve found are considerably smaller in number (and weight) with only some 30 curves:

Radius Curve Set (click image to enlarge)

While looking less used, I suspect that these sets made out of wood are, in fact, older than the others.

Wooden Radius Curves (click image to enlarge)

Wooden Radius Curves (click image to enlarge)


Dixon Kemp's 'Pear-shaped' Curves

June 2017

Dixon Kemp (1830-1899) was a naval architect and prolific writer having published 4 books1,2, each of 700+ pages. The only book of his which contains drawings of the ‘pear-shaped’ curves is a book he co-authored with Adrian Neison, Practical Boat Building for Amatuers.3 G. Christopher Davies was added as an author in one of the later editions.

New York Public Library has two copies, one from 1882 and another from 1901. The description is short and to the point:

There are usually eight pear-shaped curves to a set; the largest 1-ft By 7 in., and the smallest 3-1/2-in by 1-1/2in.

Pear-shaped Curves (click image to enlarge)

It is curious that although he mentions a set of 8 curves, this drawing from Practical Boat Building only shows 5. Although one would hope that a chapter on drafting would include scaled figures, when scaled to a height of 12”, the width of the largest curve is about 6.65” in one edition and about 6.85” in the other. This leads me to believe that it’s actually the printing process or how the pages expanded and contracted over the years that generates the incorrect scale.

One of the most interesting (and definitely the most amusing) summaries of nautical curves that I’ve found is from Howard Chapelle’s 1939 book titled Yacht Designing and Planning for Yachtsmen, Students, & Amateurs.

Curves and sweeps are usually obtainable in sets and are made of wood, hard rubber or celluloid; the last is best, and most expensive. The English curves, such as Stanley’s “Dixon Kemp” pear-shaped curves, are excellent. The “Copenhagen” curves are much used, though more curves are required to make a set than with the “Dixon Kemp” model. The long curves in “Copenhagen” set are called “sweeps” and replace battens to some extent but are expensive and require much practice to use properly. However, they are very handy when tracing as they save much time since ducks do not have to be set. There is great difficulty in obtaining fair sweeps and usually the draftsman must refair them with a file. A set of “Copenhagen” curves usually numbers between 40 and 50 pieces, including sweeps; it is best to purchase each one as the sets contain many curves and sweeps that are very rarely of use. “Dixon Kemp” curves, number 5 to a set, in two sizes. Some English firms sell special sets of “Copenhagen” curves, of wood, specifically selected for yacht design; the cost is usually low. “French” curves, such as are used in mechanical drafting, are useless for marine drafting, with but one or two exceptions. The sketches show some useful curves and sweeps selected for yacht design.4

Beyond his flair for the dramatic (ie French curves are useless in marine drafting), Chapelle’s causal-style leaves many questions unanswered: what are the one or two cases where French curves aren’t useless? what about the Dixon Kemp model allows it to use fewer curves? which curves are rarely used? or most used?

This also is the only reference I have been able to find which attributes the pear-shaped curves to Dixon Kemp, although there is no indication from Kemp that he originated them. And I can only assume ‘Stanley’ is a reference to the company which produced them.

Sweeps and Curves (click image to enlarge)

This drawing includes a scale so when enlarged to full size, the largest pear-shaped curve measures nearly exactly 12” x 7”5. While unfortunate, but not surprising given other curve comparisons, the curves’ shapes do not match. This is even when we stretch the drawing in Practical Boating (blue) to have the same dimensions and then superimposing it on the curves as drawn by Chapelle. The latter, however, are suspect in design since they are nearly symmetrical in shape, something that would not be helpful when used for drafting; flipping over the curve would make the other edge is redundant.

Dixon Kemp Curve Comparison (click image to enlarge)

I’d like to also highlight another passage from Practical Boat Building, because of nothing more than it made me smile when I read it. Whether it be from Kemp or Neison, I liked the cheerful disposition (especially in comparison to Chapelle):

He [the amateur] mus obtain a complete set of instruments. This all amatuers are advised to do, if they can afford it, and they will in return find much amusement and plenty of opportunity for study and research in the highly interesting study of naval architecture.

  1. Kemp, Dixon. 1885. Yacht architecture: a treatise on the laws which govern the resistance of bodies moving in water, propulsion by steam and sail; yacht designing; and yacht building. First edition, 1885.

  2. Kemp, Dixon. Manual of Yachting and Boating. First edition, 18xx.

  3. Neison, Adriane and Dixon, Kemp. Practical Boat Building for Amateurs: Full Instructions for Designing and Building Punts, Skiffs, Canoes, Sailing Boats & c. First edition, 1880.

  4. Chapelle, Howard. Yacht Designing and Planning for Yachtsmen, Students, & Amateurs. First edition, 1939.

  5. As measured, it is 12.015” x 6.954”. Given that the line width of the scaled-up drawing is 0.100”, the actual dimensions as described in Practical Boat Building for Amateurs is well within the margin of error. 


Ship Curves One

June 2017

The “Ship Curves One” is just a single piece of acrylic, but it contains over a dozen small ship curve shapes. Passed along to me by an accomplished ship modeler (and an amazing teacher), the design comes from a curve that he found in an old drafting studio. Beyond that, its origins are unknown but it definitely has proven a valuable tool.

Ship Curves One Prototype (click image to enlarge)

I have found it most helpful for drawings that have been scaled down to less than 8” in length.


Sets of Copenhagen Ship Curves

May 2017

Collections of curves used for naval drafting have existed since the early 1800s, with most of the curvatures being created to fit the drafting need at hand. Eventually, drafting supply companies came up with sets for sale, with the earliest mention I’ve found is in the 21st edition of the Keuffel & Esser catalog from 1890.

By 1921, Keuffel & Esser produced sets that consisted of 56 pieces. I picked up the first of my Keuffel & Esser sets at an estate sale but it only contained 32 pieces:

K&E Set 1 (click image to enlarge)

The second K&E set I purhcased on ebay in 2016 had all 56:

K&E Set 2 (click image to enlarge)

The next set I have is made by Charvoz. Although listed on ebay as a set made in Japan, I’ve actually found references of it as a German-based company. And some of their other drafting products (compass sets, slide rules, etc), have a “Made in the USA” tag on them:

Charvoz (click image to enlarge)

Another set I found is just of a few curves marked with the Dietzgen logo on them:

Dietzgen (click image to enlarge)

The remaining two sets I purchased on ebay are made by an unknown manufacturer as all the curves have on them are the curve number stamped in red. Both are complete with 55 curves.

Mystery Manufacturer (click image to enlarge)

Mystery Manufacturer (click image to enlarge)

The wooden curves were made by (and probably exclusively used by) the Fairfield Shipbuilding and Engineering Company. This is the only set I’ve found made of wood, other than the antique collections and the display ath the Royal Museum.

Fairfield Shipbuilding and Engineering Company (click image to enlarge)