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Calculating the length of topgallant yards


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Maybe you guys could offer an opinion or an explanation.

 

Both Steel's “Elements of Mastmaiking, Sailmaking & Rigging” as well as Lee's “The Masting & Rigging of English Ships of War” indicate that for most if not all of the 1700's, topgallant yards are to be ½ of their respective topsail yards. Easy enough but.......

 

If you consult the tables of contemporary dimensions in either book the proportions shown in all of the examples range from .625 to as much as .74.

 

I have just rec'd my copy of Ian MCLaughlan's “Sloops of War” He devotes a whole a section in the back to the various sailplans. In it he gives 6-8 lists of spars for various sloops from the late 1600's through about 1750. The proportion of topgallant yards to topsail yards in the lists is pretty constant at about .7 But then he gives a list of proportions to be used to calculate the lengths if you cannot find an actual list for a specific vessel. His list of proportions recommends .5 which is not in line with the lists of actual spars he has on the same page.

 

This creates quite a difference in the look of the sailplan. It becomes so much squarer at the top. It's not a huge visual issue with bare yards, but when the sails are bent on it becomes a brand new day.

 

What am I missing?

 

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According Sutherland in his The ship-builders assistant : or, some essays towards compleating the art of marine architecture, (1711), the top-gallant yards are 1/2 the top-sail yards. 

 

R.C. Anderson citre a similar ratio in his The Rigging of Ships in the Days of the Spritsail Topmast, 1600-1720 (1927).

 

For French vessels during the 18th century, there is some interesting information in Marquardt's Eighteenth-century rigs & rigging (1992) where the top-gallant yard was 0.256 of the ship's length.  He also offered that Chapman used 0.7 the length of the main topsail yard for the main top-gallant on Swedish ships, He provides a ratio of the fore and main top-gallant yard to the corresponding topsail yard of 0.690 from Falconer (1769) for all rates, and several possible ratios for English ships between 1711 and 1756 - ranging from 1/2 of the main topmast (1711), 3/4 of the beam (merchant ships, 1711), 5/17 of the topsail yard (1735) and the common 1/2 the topsail yard (several listings).  These refer to proportions from Davis (1711), Sutherland (1711), Love (1735), Mountaine (1756) as well as Steel (1794), Falconer (1815 edition) and others.  See Marquardt pages 33-36 for the various tables.

 

Recalling always the vagaries of rigging at the time!  These were somewhat more of a guideline - frequently not meeting the approval of a given builder or skipper and adjusted for personal taste.

 

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That's my point exactly!!! Every source  more or less says 1/2. Now look at the Appendix II in Lee or the" Dimensions of Masts and Yards of the Royal Navy"

on page 53 of the 1794 edition of Steel.

 

The 100 gun ship in Steel has a main topsail yard of 73' & a topgallant of 48'9"38 that's a lot more than 1/2 it's a little more than 2/3. The 38 gun ship is 59 & 37.

 

In Lee the avg for the 1773 Establishment on page 198 is .656 on the main & .6632 on the fore. in the 1745 & 1754 establishments table it is .69 on the fore & main. Not a single example of a real ship has topgallant yards any smaller than .6

 

My question is why don't the table reflect the formulas. If I use the formulas I come up with very different results

 

Should I use the ratios as described in the text or in the examples?

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As Wayne suggested, theory and practice did not always coincide. I'm sure that a spar of roughly the right length was pressed into service on many an occasion. What size of ship and date have you in mind?

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I agree that in there were differences between the theory of masting and what you would find if you could visit the harbor. But what I am seeing is that while most of the masts and other yards seemed to follow the rules in most cases, the topgallant yard lengths listed for specific ship never and i mean never followed the rule.

 

The sail plan I am attempting to reconstruct would be for the Port Antonio purchased into the Royal navy about 1757. She was two masted. The placement of the masts is not suitable for a ketch, and the arrangement of the lower dead-eyes indicates she was a brig or snow and not a schooner of some kind. Given the date I think a snow more likely. I have incuded a paining by Clevely from 1759 of a what appears to be a similar vessel. Just add a handful of gunports in the waist and some sweep ports as well. She was 67'9" on the deck 22' beam, 9'9" deep and 144 tons. L+B+D =99'6" divided by 2 gives a main mast length of 50' which matches nicely with Steel and the other examples given the "Sloop of War". Lee's book does not have much to say about two masted ships.

 

The main yard is .9 times the mainmast 45' and we are still good. The topsail yard is about .72 of the main yard or about 32'5". This figure is supported by all of the tables, If the top-gallant should be 1/2 the topsail then we would use 16' or a couple of inches more. But look at the figures in Steels examples. His brig has a main yard of 42', close, a topsail yard of 31'6", still very close... and a top-gallant of 23'6"  which is a full 34% bigger than his own guidelines would indicate.

post-2745-0-66416700-1403098167_thumb.jpg

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Hello Michael,

 

That's a very interesting picture of that merchant snow which you have there!

 

Now just my two cents: First, I may be wrong, but are you sure the topgallant yard is given 1/2 of the topsail yard, instead of the main yard? If you look at your picture, it is immediately evident that the topgallant is very close of half the length of the main.

 

The main itself is always given as two times the breadth of the ship, so it would make more sense to relate everything on just one dimension instead of a complete sequence!

 

Secondly, I vaguely remember that when making such ratios, the shipwrights always spoke of the "live" length of the yard; to which they added the length of the yardarms: it is the part which is painted white from mid-19th century practice.

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Last night I found a 1794 copy of Steel on the Historic Naval Ships Association websitehttp://hnsa.org/doc/steel/index.htm%C2'> . It said:

 

PROPORTIONAL LENGTHS OF YARDS, IN THE ROYAL NAVY.

Main-yard, 8/9 of the main-mast.
Fore-yard, 7/8 of the main-yard.
Mizen-yard, 6/7 of the main-yard.
Main-topsail-yard, 5/7 of the main-yard.
Fore-topsail-yard, 7/8 of the main-topsail-yard.
Mizen-topsail-yard, 2/3 the main-topsail-yard.
Topgallant-yards to 74 gun ships, 2/3 all under, 3/5, of their topsail-yards.

Royal-yards, 1/2 of the topsail-yards.
Cross-jack-yard, the same as the fore-topsail-yard.
Spritsail-yard, the same as the fore-topsail-yard.
Spritsail-topsail-yard, the same as the fore-top-gallant-yard.
Studdingsail-yards, 4/7 of their booms.
Driver-yard, the same as the fore-topgallant-yard

 

 

This is different than my copy! And certainly different than Lee.  It works much better.

 

And lastly in the section on rigs and sail plans in Sloop of War, the author comments that it is almost impossible to determine with any certainty what the rig of a small vessel may have been. He says the brigs, sloops, snows and brigantines were re-rigged and re-rigged. Further he comments that although many 18th century small craft are recorded as brigantines, not a single set of spar lengths for a brigantine have come to light. It is only in the 19th century that there is documentary evidence for this rig.

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