Gaff sails and backstay rigging rules

[Michelnou]

Sailboats including gaff sails like schooners, clippers or brigs require free space behind the masts to allow booms and gaffs to move on each side without hitting obstacles.

Yet, it is necessary to apply forces with ropes, on the masts, towards the stern to secure their fixing and position.

That is why I am looking for the backstay rigging rules, for these particular ships, which can allow both the mechanical support of the mast and the free moving of gaff and boom.

 

I suppose that these rules will broach,

- the height, in relation to the deck, of the link between mast and backstay,

- and either the angle between the backstay and the mast, either the maximal distance between the mast and the tie of the stay on the deck.

 

I thank you to provide to me knowledge on this particular subject.

Mike

[allanyed]

For the main back stays, these are usually flying back stays that are set up with blocks to allow one side or the other to be "let go" in order to swing the boom. 

Allan

 

[Michelnou]

From a practical point of view, can you specify the blocks used to build the tackle, that is to say the deck's block and the upper block (single or double or else).

I imagine that the deck's block is fastened to an eyepin glued in the deck.

Thank you

Mike

[Bob Cleek]

The answer to your question depends upon the particular vessel and is dependent in large part to the size of the vessel. Smaller vessels may run the fall of a running backstay to a turning block fastened to the deck and then aft to a lever which tensions the backstay when it is thrown down. On larger vessels, a purchase is rigged which may be arranged in any number of ways, but generally with the weight of the blocks kept as low as possible. Running backs may also have a hook at their lower end to which a tackle can be attached. Unhooking the backstay then permits it to be run forward and lashed to the after shroud to keep it out of the way when not in use.

 

If you could post a picture or sailplan of the vessel, you'd probably get the best answer that way. 

 

[allanyed]

Michel,

The attached first page is a sketch of the backstay rigging for a 65 foot schooner.  Note that the block and cleat in this sketch are inboard.  The eye is in the cap rail or alternatively may be secured to the deck. The next three pages by Jennison may help in much of your rigging.   As Bob mentioned not all vessels were rigged the same.  A great reference for schooners of the late 18th century is Chapelle's American Fishing Schooners. One caveat is that while this book is loaded with details, it has no useful index and I find myself scouring it every time I need to find a detail.  The rigging subjects are "somewhat" in alphabetical order in the book but a pain in the neck to find anything quickly.  On the plus side, I find every time I use it, I get a LITTLE more used to how he laid out the items. 

Allan

 

[Michelnou]

I thank you for these informations.

In fact, I must clarify the features of the ship. She is a Baltimore clipper, built about 1780-1820. This schooner was not a big ship : deck length about 65 feet, 2 masts with gaff sails, 2 square sails with 3 yards on fore mast , bowsprit and jibs, racked masts, flush deck, 6 guns and a "Long Tom", certainly designed for a small crew.

The model's plans seem to be drawed with a scale about 1/45.

Mike

 

[Roger Pellett]

With their heavily raked masts would these vessels have needed backstays?

 

 

[Bob Cleek]

1 hour ago, Roger Pellett said:

With their heavily raked masts would these vessels have needed backstays?

 

 

Probably not. Some may have carried them for temporary rigging, particularly from the the point(s) where square sail yards crossed the mast to prevent the mast bowing when running in heavy weather.

[druxey]

All supporting rigging is strongest in 'tripod' configuration, so I supposed fore stays and shrouds would probably do it. However, I suspect running backstays added would make for 'belt and braces' - literally! - in severe weather conditions.

[Geowolf]

4 hours ago, Michelnou said:

I thank you for these informations.

In fact, I must clarify the features of the ship. She is a Baltimore clipper, built about 1780-1820. This schooner was not a big ship : deck length about 65 feet, 2 masts with gaff sails, 2 square sails with 3 yards on fore mast , bowsprit and jibs, racked masts, flush deck, 6 guns and a "Long Tom", certainly designed for a small crew.

The model's plans seem to be drawed with a scale about 1/45.

Mike

 

hi Michel,

 

this sail is very very close to Albatros kit from Constructo, my first model; if you need info about rigging i can try to scan it and share a Google Drive

Sure you're a lot more experienced builder, i only speak some simple comments about ropes, strengh, etc; for my experience, all ropes are working togheter, if you streches a particular rope, maybe other one will remain flaccid; the masts are flexible so the forces are transmitted by the ropes from one mast to the other. For me, the best way is to locate the opposite ropes and forces, and strengh in opposite mode with the same force to assure the forces are cancelled 😄.

 

An old picture of my Albatros, and best regards!

[Roger Pellett]

American small fast sailing vessels of the period in question were notorious for being lightly rigged.  There are contemporary paintings of Chesapeake Bay Pilot Boats with masts that are completely unstayed no shrouds or stays.  The Baltimore Clippers were decendents of these small high speed Schooners.

 

There is an Admiralty drawing of a rigged longboat in W.E. May’s book on ships boats.  This sloop rigged boat with raked mast has no backstays

Edited November 25, 2020 by Roger Pellett

[Roger Pellett]

The Pride of Baltimore has a running main topmast backstay that would be tensioned when the gaff topsail is set.  She does not have a backstays leading to the top of the main mast.  Under working sail, without the gaff topsail set,  she is, therefore, capable of sailing without a backstay.

 

She is actually Pride of Baltimore II, the first Pride was lost off the Barbados in 1986.  In designing the second Pride, naval Architect Thomas Gillmer modified the underwater hull lines to increase stability but did not change her rig to add backstays.

 

Another example would be the Schooner Yacht America.  Her heavily raked masts were not fitted with backstays.

 

Roger

Edited November 26, 2020 by Roger Pellett

[Bob Cleek]

2 hours ago, Roger Pellett said:

Another example would be the Schooner Yacht America.  Her heavily raked masts were not fitted with backstays.

 

Nor the famed Danish spidsgatter racers with their uncommonly high and large rigs and carry no backstays at all !

 

Edited November 26, 2020 by Bob Cleek

[mnl]

The Star has no permanent backstay. You can see the runners coming down about halfway down the cockpit. Upwind it is used to control the shape of the mast and hence the shape of the sail. The mast has prebend so if you pull on the intermediate backstay it will add draft to the main and increase power. If you pull on the upper it will twist off the top of the main and depower the main. The main by itself will hold the rig up.

Even on a fairly close reach the leeward backstay has to be released so the main can go out.

 

Downwind it is an entirely different story. The backstays hold the rig up if there is any breeze. Jibing can be character building as you have to pull the leeward backstay in as the boom comes to the centerline on the boat and them the new leeward backstay has to be let off so the boom came go out. In twenty knots this happens quickly and if you make a mistake the rig goes over the front of the boat.

Edited November 27, 2020 by mnl
Fixing autocorrect

[mnl]

Prebend, not pretend.

[mnl]

A Star going downwind. Note how the rig is allowed to go forward. 

[Dr PR]

I have been following this thread with interest.

 

Most of the Baltimore schooners in Chapelle's The Baltimore Clipper do have one or two backstays rigged high on the fore and main top masts and leading down to the channels (aft of the shrouds) where they were rigged with deadeyes (often smaller than the deadeyes for the shrouds) or just eyes with lanyards to hold them taut. Because these ships had extreme rake to the masts the channels were not far aft of the masts and the back stays were almost vertical. This allowed the fore boom (if any) and main boom to swing fairly wide, and the gaffs could swing far out to spread the sails for catching following winds.

 

However, in some cases the main mast had a backstay that ran far aft to the bulwark. These had a tackle with one block anchored to the deck (or hooked to an eyebolt in the deck) and the other on the stay. The running part was attached on one end to a block and the free end was secured to a cleat or belaying pin on the bulwark. When running with the wind the windward backstay was pulled taut to take the strain and the leeward was slacked (and even unhooked) to allow the main sail to swing wide to catch the wind.

 

****

 

The mainstays were rigged in several ways. The simplest was just a stay that ran from the main top to the fore top above the fore gaff. That way the stay did not interfere with the gaff. The forestays took the load on the main mast.

 

Some plans show fixed dual mainstays (or mainstay and preventer) that ran from the main top to knightheads on deck forward (larger ships) or aft (smaller ships) of the fore mast. In these cases the fore gaff sail (or foresail) did not have a boom, but had port and starboard sheets to the clew (lower aft corner of the sail). When tacking the foresail was hauled over the mainstays with the sheets. They often had a brail to haul the clew to the fore top to help pull it over the mainstays.

 

A third and apparently common method of rigging the mainstays was as mentioned above. Two stays ran from the main top forward to the port and starboard bulwarks forward of the fore mast. They were rigged with a tackle with one block anchored to the deck (or hooked to an eyebolt in the deck) and the other on the stay. The running part was attached on one end to a block and the free end was secured to a cleat or belaying pin on the bulwark. When the ship was tacking into the wind (the force of the wind pushing aft on the sails and mast). the windward side mainstay was pulled tight to take the strain on the mast and the lee side was slackened to allow the fore gaff sail to swing wide to catch the wind from the jib.

 

****

 

With the tackle rigged backstays and mainstays  a change of course or wind required adjusting the stays so the windward stays took the forces on the mast (the leeward stays did not carry a load so they could be slackened to allow more freedom of movement for the gaff sails.

 

****

 

All of these arrangements seem to be used in modern schooners. If you examine photos closely you can see the same ship with mainstays and backstays all rigged taut  or the lee sides slacked when under sail, and not rigged at all when motoring in and out of port with sails furled.

Edited November 27, 2020 by Dr PR

[Bob Cleek]

On 11/26/2020 at 5:16 PM, mnl said:

A Star going downwind. Note how the rig is allowed to go forward. 

 

Well, yeah, but you'd expect that with a Polish crew!    

 

(I hope I didn't offend anyone with a Polish joke!)

 

[Dr PR]

John Leather's The Gaff Rig Handbook has information and drawings for fore and aft rigs. Some of the information applies to 19th century ships,  but there is a lot of information about 20th-21st century vessels, including racing yachts. It has quite a bit of the history of gaff rigs,  but not very many actual sail plans and rigging diagrams.

[mnl]

On 11/27/2020 at 10:14 PM, Bob Cleek said:

 

Well, yeah, but you'd expect that with a Polish crew!    

 

(I hope I didn't offend anyone with a Polish joke!)

 

Well they might have been able to let it a little farther forward. Forward is fast, at least until the rig comes down. The idea is the sail becomes an airfoil from top to bottom. 

[mnl]

It is all a matter of engineering. The first consideration is unless the spar is really strong you don’t want much load at the partners. That represents a big stress concentration and will break it if the load goes up too much. Say if you are running and get hit with a big puff. Then it is supporting the rest of the rig to keep it in column. This assumes a wooden spar, I have rarely seen any of those pictured with prebend. I also think the load cases work much better if the spar is more or less in compression. Again, think about the case of getting hit with a big puff.

 

Now that the spar is supported and in column, get everything that you need to out of the way so you can trim the sails. What works to weather may not on a reach, and you may need something completely different far off the breeze. The load paths continually change as the apparent wind angle changes. 

Edited December 1, 2020 by mnl