Why masts are square at the top?

[Tommy Vercetti]

Hi, I'm quite new to ships and I was wondering if someone could explain how masts are done exactly on old full rigged ships. I was checking some general plans on masts on the internet but I still don't quite understand. In general, I found that the mast is round until some point and then it is somehow squared off on the top, but if I understand correctly it is first trimmed in octagon before being squared. Can someone explain why it's constructed like this, please? And is it the same for topmast and topgallant mast? Also, if anyone can point me to some good plans on masts, would be be much appreciated. Thanks!

[druxey]

Good question. Real wooden masts and spars are first cut to a square cross-section, then octagonal, then sixteen sided before being rounded off. Some sections are left square so that other things (such as mast caps) attached to them can't skew around.

[Mark P]

Good Evening Tommy;

 

Masting ships is quite a wide topic, and the exact reply depends upon the period in which you are interested. If you are prepared to purchase some good books to learn from, then I strongly recommend the following:

 

For merchants ships, look for 'Masting and Rigging the Clipper ship and Ocean Carrier', by Harold Underhill.

 

For English warships, look for 'The Masting and Rigging of English Ships of War', by James Lees.

 

There are other books for ships of other nations.

 

All the best,

 

Mark P

[barkeater]

Tommy,

As Mark noted masts are quite a wide topic and different masts and yards show different shapes. They also changed over time. If your question is in regard to mast caps, the following illustration from Petersson's "Rigging Period Ship Models" may be helpful. Here the main mast is squared off to sit into the mast cap. The top mast is first square to sit on the trestle tree, then becomes octagonal before being rounded off to fit through the mast cap. 

Richard

[Dr PR]

Tommy,

 

Good question.

 

First, although there was a general "right way" to build masts that was passed down from generation to generation of ship builders over the centuries (word of mouth - no Internet), ship builders were also artisans who took pride in their work. And whoever commissioned/purchased the ship (merchant or Navy) set limits to the cost (time and materials). Consequently there were a lot of variations on the basic "right way."

 

One of the problems with wooden masts is that trees could not be found that were tall and straight enough for really tall masts. So they were created in two or three parts, with each part "stepped" as in the Petersson illustration Barkeater posted above. This area where the two masts ran parallel was called the "doubling." They also needed platforms for sailors to stand on while working aloft. So the "top" was created where two masts were joined and the associated rigging attached.

 

Just below the "top" the mast was round typically, although this is a very oversimplified statement! But at the top some structure was necessary to support the lower part of the upper mast and fasten it in place. The point where the mast changes from round to square is called the "hounds." Please do not ask anyone to explain why!

 

But at the hounds several pieces of timber were attached to create the foundation for the top. Two fore-and-aft wooden boards (rectangular cross section) or "trestletrees" were attached on either side of the lower mast. Note: In the Petersson illustration forward is to the left for most, but not all, ships. To make the trestletrees fit tightly the mast was carved square. These two trestletrees formed the sides of a pocket the upper mast fit into. You can see these in Petersson's illustration. The square mast section prevented the trestletrees from trying to rotate around the mast.

 

Two or more "crosstrees" (also rectangular cross section) were attached behind the lower mast top and forward of the upper mast bottom or "foot." You can see these in Petersson's illustration. Again, having these parts of the masts carved square made the cross trees fit tightly. On the higher masts the cross trees were all that were provided. But on lower mast tops of larger ships a platform was sometimes built on top of the crosstrees.

 

OK, we have described the lower part of the doubling where the two masts ran parallel.  The top of the doubling was the "cap". This is the rectangular wooden piece at the top of the lower mast in Petersson's illustration. The hole for the lower mast was square. This was to ensure that the top couldn't rotate around the  mast. So, with the lower part of the lower mast doubling square to accommodate the trestletrees and crosstrees and the upper part square to fit the cap, it was easiest to just make the entire part of the lower mast doubling square. Of course, it really isn't that simple.

 

The hole in the cap where the upper mast fit was round  and the upper mast tapered above the cap. Below the cap it was typically cylindrical, or maybe octagonal, but slightly smaller diameter than the hole in the cap. The bottom or "foot" of the mast was square and sized to fit into the pocket formed by the trestletrees and crosstrees. This was so the upper mast could be lowered and raised through the hole in the cap and the pocket between the trestletrees and crosstrees. The whole thing was designed to be taken apart and rebuilt at sea!  And that is a long story!

 

Then you must add to this the variations in design that resulted from cost conscious jobs and the very elaborate variations where elegance was more important than cost. In other words, on fancy ships the upper part of the lower mast and lower part of the upper mast were often carved octagonal, or square with octagonal sections, etc. "Tricked out" in modern terminology.

 

If you really want to know how masts were assembled and repaired get one or both of these two references. They explain how ships were built and operated in the age of sail - from the horses mouth!:

 

"The Young Sea Officer's Sheet Anchor" by Darcy Lever (1808) and updated for the US Navy by George Blunt in 1858. Everything you ever wanted to know and a lot more!

 

"The Art of Rigging" by George Biddlecombe (1925), a republication of David Steele's "The elements and Practice of Rigging and Seamanship" (1794).

 

You can also find Steele's original work on line in PDF form.

 

For mast plans and a LOT more look at James Lees' "The Masting and Rigging of English Ships of War 1625-1860", Naval Institute Press, 1984. But it is specific for British ships (a strong influence on American practice), and says little about smaller rigs, especially fore and aft rigs of schooners, cutters and such.

 

A very good general reference (get this if you don't get anything else) is Wolfram zu Mondfeldt's "Historic Ship Models", Sterling Publishing Co., New York, 1989. Again, everything you wanted to know and a lot more. He explains the historical development of a lot of the parts of sailing ships.

 

Harold Underhill's "Masting and Rigging of the Clipper Ship & Ocean Carrier", Brown, Son and Ferguson, Ltd., Glasgow, 1972 (mentioned above) is the best written and most useful reference I have sound for sailing ships, especially for understanding the arcane terminology. However, he describes ships of the late 1800s and early 1900s, so it is of less usefulness for earlier ships.

 

If this isn't enough just ask and we can supply references to a dozen or more other useful books!

Edited December 2, 2021 by Dr PR

[Gregory]

18 hours ago, Tommy Vercetti said:

I found that the mast is round until some point and then it is somehow squared off on the top,

Just to show that things were even more complicated, and to emphasize what Dr PR said about finding suitable timber for a tall round mast,

large main masts would have been laminated like this, from Mondfeld:

 

[allanyed]

The above mentioned books are great if you have them but there are a lot of contemporary drawings on the RMG Collections website on masts and yards that can be downloaded for free in low resolution.  There also a number of high resolution contemporary drawings from RMG on the Wiki Commons site for various ship sizes and eras.  Most of the  high res are about 75 mb so cannot be loaded here.   Two  examples from 1780 that are only about 30mb each follow.   

Allan

 

[Gregory]

Here is a link where you can click through some of the high res images:

 

Built up Yards & Masts

[mtaylor]

14 hours ago, Dr PR said:

 

 

Just below the "top" the mast was round typically, although this is a very oversimplified statement! But at the top some structure was necessary to support the lower part of the upper mast and fasten it in place. The point where the mast changes from round to square is called the "hounds." Please do not ask anyone to explain why!

 

Good on not asking "why"... I've made that deep dive into the Internet some time ago and ended up in many places.   Some were not a good place to be.

[wefalck]

The original question was 'why are they square', I believe, but nobody seems to have answered that yet: for the simple mechanical reason that the caps and cross-trees do not turn around the tops, when the standing rigging of upper masts is set.

[Tommy Vercetti]

Thank you a lot for your invaluable feedback. I've learned a lot! Will dig deeper into the books and materials you guys recommended.

[druxey]

Wefalck: um, see response #2!

[wefalck]

Sorry, missed that 🤭