Purpose of shifting- and breast backstays

Essentially, as I understand it, the breast backstay was part of the permanent standing rigging; it was set up like the other backstays, but further forward, abreast the mast.  Its function was the same as that of the other standing backstays:  to provide support for the topmast.

The shifting backstay was a temporary line, set up, with block and tackle at its lower end, when the ship was working to windward in a particularly strong breeze. 

Here's what James Lees, in his Masting and Rigging of English Ships of War, 1660-1865, has to say about both:

"Breast backstays had their upper and lower ends set up in the usual fashion [i.e., like the regular standing backstays], but according to models in the National Maritime Museum, very few English ships were fitted with them.  The standing backstay seems to have served the same purpose by having the foremost backstay well forward along the channels.  I have seen contemporary models - one of the 1719 Establishement and one of the 1733 Establishement - carrying a breast backstay, and then not found any again until 1839.  When fitted, they ran abreast of the mast.  Personally, I would not fit them unless they were shownon a painting or print of a model I intended to make, and then would only fit them after 1719....

"Shifting backstay size is given in the rigging tables, but this would not be seen generally as it was only used to give additional stay to the mast when sailing , and would be unrove in port or whenever it was thought fit.  A pendant, half as long again as the burton pendant, was fitted however.  A thimble was spliced into the lower end, while the upper end fitted the same as the burton pendant. 

"Shifting backstay falls consisted of a long-tackle block hoooked in the thimble of the pendant, and a single block hooked in the fore channels or to an eyebolt in the deck."

Breast backstays were set up to provide additional support to the topmasts when sailing. They led to the middle of the channels and were set up with blocks and tackles as opposed to the deadeyes and lanyards as used for the standing backstays.

I think confusingly  there are also breast running backstays referred to in various books on rigging.

I understand that the name 'shifting' backstay derives from its purpose of being moved from one side of the ship to the other, again to provide additional support in particular sailing conditions. These also had tackles as opposed to deadeyes and lanyards, and would be unrove when in port.

Longridge describes both breast and shifting backstays in his 'Anatomy of Nelson's Ships' and indicates their set up but without describing their purpose.

So I think the simple answer is a 'belt and braces' job to provide additional support in particular sailing conditions.

 

Actually, shifting backstays does not move from one side of the ship to another.   They usually go down the back of the mast, sometimes right down the middle of the ship.   But always symmetrical.   The main cable of theshifting backstay is permanently attached to the hull on the one end,  and to the top of the top mast in the usual fashion of any top back stays.   

What disinguishes a shift backstay is that it also has a third attachment to the mast somewhere along the length of the top mast.   This third attachment comes in the form of a cable loop that loops around the stay itself and the mast.    This loop can be shifted up or down along the length of the mast, thus the name shifting backstays.

The purpose of the shifting backstay is to relieve the strain on the mast when te topsail is reefed.    Consider when the sail is fully spread.   In this case, the topmast yard is at its highest position and thus located near the cap of the top mast.    The force acting upon the sail is thus transmistted almost directly into the mast top, and from there, down to the hull through the mast's collection of shrouds and normal stays.   The mast itself only has to hold up the yard.   It does not have to withstand very mush of the lateral forces of the sail.   Those are all taken up almost directly by the stays and shrouds.

Now consider when the top sail is double reefed.   In this case, the topsail yard must be lowered about half way down the top mast to accommodate the shortened sail.   Now the force of the sailing is transmitted to the middle of the topmast far away from any direct support the mast may have.    Here the top mast is not supported by anything but its own strength.     The mast is thus placed under great strain whenever the topmast yard is lowered halfway to accommodate a double reef.  

This is why topmast shifting stays were invented.    Shifting stays adds a third, shifting attachement to the stay.   This stay travels up and down with the top mast yard to relieve the stress on the mast as the yard is raised or lowered to accommodate reefing.   

Both shifting (travelling) and breast backstays provided additional support to the standing (stationary) rigging but were set up as running (moving) rigging to avoid interferences with other moving parts of the rig.

Travelling Backsay

As mentioned in a prior thread entry, the travelling backstay could be used to provide an assymetrical backstay configuration for the masts. They were adjustable to reduce the the limits on boom or yard traverse which would be imposed if rigged as standing rigging.  Rather than being physically shifted from port to stbd. or vice versa, the leeward line would be eased (and probably relocated - but on the same side of the vessel) and the windward line taken in, as opposed to transferring the line back and forth (a difficult proposition considering stays, staysail sheets, etc. in the way). The need for slacking and possibly moving the lines was to avoid interference with other rigging components, the leeward shrouds go slack anyway. I've sailed on a schooner with traveling backstays for the main. the most annoying exercise in a tack was manhandling the heavy line and blocks from station to station. On a jibe it could be harrowing.

On a square rigger, the traveling backstay also could be adjustable to allow the point of support to move up and down the topmast to coincide with the yard position as the topsail was reefed. The travelling backstay was attached at the topmast top and had a traveller attached just above the parrels which circled the mast and backstay and would slide up and down the mast with the topsail yard. The length of the backstay had to be adjusted as the yard was lowered to the multiple reefed postions. 

Breast Backstay

If set up standing (stationary), the breast backstays would limit the traverse of the yard and limit how close to the wind the associated square sail could be set. The breast backstays had to be running (adjustable) to allow shifting of an outrigger (a board with slots in the end) in the main top from one side to the other. The outrigger displaced the breast backstay to windward to provide a greater angle (and more lateral support-same funtion as shroud spreaders on modern boat)  to the topmast. The leeward breast stay had to be retracted (into the plane of the standing shrouds) and the windward stay extended by shifting the ourigger to windward, which allowed the yard to swing closer to the wind.

As has been mentioned,these lines had no use when the sails were furled and would not have to be present unless the model is rigged under full sail. 

These terms undoubtedly were given slightly different definitions at different times and in different countries.  Insofar as British practice is concerned I'll trust Mr. Lees, who knows far more about the subject than any of us.  (He doesn't suggest even faintly that any form of backstay got shifted from one side of the ship to the other - though I guess that would, with considerable effort, have been possible.  He does say - and contemporary texts and models confirm - that the lower end of the shifting backstay was set up with block and tackle rather than with deadeyes and lanyards.) 

The Lees book contains no reference to anything called a "topmast shifting stay."  Chuckfan's description of it seems to fit what I'm accustomed to calling the middle staysail stay.  The middle staysail, which Mr. Lees says was introduced about 1773 (he's talking strictly about British practice), filled in the space between the main topmast staysail and the main topgallant staysail.  It ran along a special stay, which, though it probably did supply a little additional support to the main topmast, was smaller in diameter than the main topmast stay. 

The lower end of the middle staysail stay was seized to a thimble in a grommet that ran up and down the fore topmast, under the fore topsail yard parrel.  (The middle staysail couldn't be set properly with the fore topsail yard in the lowered position.)  The upper end of the middle staysail stay ran through a cheek block on the main topmast head; the bitter end of it was seized to a double block.  The middle staysail stay obviously had to change in length when the grommet moved up and down the fore topmast.  This was accomplished by means of a simple tackle, which started at a single block on one of the main trestletrees, then ran through the double block in the end of the stay, then down through the single block, then up through the double block again and down to the deck.  The grommet sliding on the fore topmast was controlled by a "tricing line" running up to the fore topmast crosstree and a "downhauler" running from the (uppermost corner) of the sail, through a couple of hanks (to discourage it from getting tangled up), through a single block at the tack (the forward upper corner) of the sail, and down to the deck.

That's quite a lot of gear for one not-especially-important sail; that may explain why staysail gear is usually omitted from models.  One sees relatively few models, other than those whose sails are set, with staysail gear.  It actually isn't especially difficult to rig, and it's rather interesting.

I understand that in Falconer's Dictionary of the Marine, reference is made to 'the third type of backstay takes its name from being shifted from one side to the other as ocassion requires'.

Further reference is made by J.H. Roding in his 'Allgemeines Worterbuch der marine, Hamburg 1793-98: ' A shifting backstay was an additional backstay, set up in conditions of strong wind or heavy rolling on the luff side and moved as necessary when the vessel tacked.'

I obviously cannot gainsay anyone on the subject, merely offer this as an explanation of the term..How it was developed, and used on particular vessels, its eventual permanency, or otherwise, I don't know.

Certainly as far as setting one up on HMS Victory - I followed Dr Longridge. His description is that they are clenched round the topmast head above the standing  backstays, - the lower block of the tackle being hooked to an eyebolt in the after end of the channel, but can be readily shifted should the ocassion arise.

Can't argue with Falconer.  Moving a backstay from one side of the ship to the other would be quite a project; somebody would have to haul the entire length of it up to the topmast head and drop it down on the other side, so it would clear all the stays and other gear between the masts.  But it sounds like they did it.

I often wonder if modern modelers and authors sometimes attribute just a little too much consistency, in both practices and terminology, to seamen of earlier centuries.  My guess is that their vocabulary was no more chiseled in granite than ours is today.   I suspect "shifting backstay," "traveling backstay," and "running backstay" were used interchangeably at various periods.  And setting up a rigging line,  requires the skilled work of a few skilled seamen for a few minutes or, if it involves such things as worming, parceling, and serving, an hour or so.  I doubt that the commanding officers of eighteenth-century warships gave a lot of thought to what the books said about the "correct" way to rig all those lines.  What matttered was what worked.  I'm not about to argue with any feature of the rigging of a ship model that can be supported with historical documentation of any sort.