How To Calculate Mast, Yard dimensions

by Norman Braslow
(Bellevue, WA)

I have a remarkable model of a medium type clipper (launched in 1865) designed by John McDonald, called Pactolus. Not a famous ship, I am afraid. However, she was featured in a book entitled, A landlubber's log of his voyage around Cape Horn: being a journal kept during a four months' voyage on an American merchantman, bound from Philadelphia to San Francisco, published by one Morton McMichael in 1882. This McMichael fellow was so enamored of the ship that about 1900 he began building a model of her, but for some unfathomable reason made her hugealmost exactly 7 feet from billethead to taffrail. I have a marvelous print of an underwriters painting of her, courtesy of the San Francisco Maritime Museum.

By a roundabout way, most of the details are unknown to me, I got her when I was about 13 years old from my grandfather. When I got her, her hull was complete and her main deck, the main cabin, and her masts. No forecastle or poop deck, no aft cabins, no yards. Unaccountably, McMichael used white calk for the deck, wired her for electricity, and put about an inch or so of tar between the bottom of hold planks and the bottom of the ship.

I got the decks finished, clenched my teeth and put white calk down to match the main deck. She is NOT museum quality?she is folk art quality. Good, but not that good. (For example, some of the deck planks run the entire length of the main deck, no joints). I have resolved to maintain that level.

As I mentioned, she had no yards when I got her. I am going nuts trying to determine the proper dimensions and in particular the length. Not a clipper as she was more heavily sparred (per general authorities for post classic clippers), than a clipper, but not a Down Easter, as she was about 5 years too early according to Lubbock. I understand that the length of the yards, starting at the lower courses, were in general based on the beam at the mast?I think. Those numbers are fore to aft, 14 ¾, 14 ¾, and 13 at the mizzen. I recall the formulae as twice the beam, the royal yard one half of the main yard, and the intervening yards just slightly outboard of a line drawn from the tip of the main yard to the tip of the royal yard. She carries nothing above her royal yards, but does have split topsails, so there are 5 yards.

Could you give me any idea as to the proper length of the yards? Is that formulation more or less acceptable for a ship of her time? And the jibboom, spanker boom, spanker gaff and monkey gaff? I have been warned that those underwriters paintings, done for insurance purposes, may not be totally reliable as far as the detailed proportions go.

Finally, what competent authority should I use for her general rigging gear? And her other deck furniture, as pumps, fife rails, capstans, etc.

I have to get her done so my wife won't kill me.

Thanks for your help.

Norman Braslow

My email is

SMH Responds

You have provided me with a fascinating morning researching the history of the Paclotus (I believe that is the correct spelling) which it turns out has been the name for at least three ships, the clipper you are working on, the original HMS Paclotus, a 38-gun Fifth Rate British Frigate built in 1813 at Deptford in the UK. Interestingly enough, this frigate was involved in the shelling of Stonington, Connecticut in 1814. She was decommissioned in 1817.

The second HMS Paclotus was Built at Armstrong, Elswick, laid down May 1896, completed September 1898. She was a Pelorus class cruiser of the Royal Navy. This 2.135 ton cruiser was sold for scrap Oct. 21, 1921.

The information on the Clipper Paclotus indicates she was one of 30 ships designed by John McDonald in Bath, Maine (from his death notice in the New York Times Jan. 7, 1897.

There is little available in my resources regarding yard dimensions and the medium clipper was one of a diverse number of fast traders built in the mid-19th century (medium or half-traders, brigantines and schooners, generalizing about their appearance is nearly impossible. They ranged in length from 150-to-250 feet to a maximum (The Great Republic) at 302-feet.

It continues to amaze me what I can find out on a topic right here at my desk. In researching yard and mast I came across the website Global Security.

Under its Military Menu; Tactics in the Age of Sail, there is an extensive description of sailing ships contained this interesting formula:

It is difficult to say what changes in the proportions of masts and yards took place in English ships between the early 17th and the 19th centuries.
The difficulty arises largely not only from insufficient knowledge of the earlier period, but from the fact that a scale was fixed only after trials, and by degrees. The topmasts are ever half so long as the masts into which they belong; but there is no absolute proportion in these, and the like things, for if a man will have his mast short, he may the bolder make his topmast long.

It can be taken as an axiom at once that the main-yard will be somewhere about twice the beam of the ship. Long yards give the best results, low
down. Higher up, it is different. For easing the ship, it is well to shelve in considerably. The main royal yard can be taken as being just about as long as the beam.

In some respects the change was certainly slight. In the early 17th century, in England at least, the length of the mainmast was fixed by taking
four-fifths of the breadth of the ship and multiplying by three.
Two centuries later the method was to take the length of the lower deck and the extreme breadth, add them together, and divide by two. If we take a 74-gun ship of about the year 1820, which was 176 ft. long on the lower deck and 48 ft. 8 in. wide, she would have, by the system then used, a
mainmast of 112 ft. Manwayrings system would have given her one of 117 ft.

It would be well worth your time to wonder through the 16 links on this site and the references they list.

I did find where the Clipper Paclotus was involved in a National Geographic Society survey detailed in the Alaska Digital Archive with some exceptionally clear pictures:
Go to Alaska Digital Archive

I apologize for not being better versed in my “Manual of Seamanship”, but it has been 50 years since I was in the Navy.

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Nov 18, 2009
Reply to SMH
by: Braslow


Thank you for all your work--I hope you enjoyed your Pactolus voyage!

First, when I read that there were pictures of her Pactolus's decks, I was thrilled. However, the Pactolus in that 1917 expedition in Alaska was the bark Pactolus also desiged by McDonald. The clipper Pactolus was lost off Hogg Island, Virginia in 1907, so even though I could not identify the Pactolus in the pictures as a ship or a bark, no question it was the bark. The bark Pactolus ended up in the Napa River, I think, as a hulk about 1930.

Several sources, including McMichael, state that the clipper (or medium built clipper) Pactolus was heavily sparred. I'll make a leap of faith and make her main yards a bit over twice the beam, and make the royals a bit more than half of the main yard.

Thank goodness the masts are there, so that issue is not a problem.

It seems that there will be no competent authority to challenge my leap of faith, as long as I keep the yards within reason and she looks ok.

Thanks again, Braslow

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