Full length Battens-2a: Girths

Posted on November 18, 2013 by Joe Cooper

Here is a bit more detail concerning the girths mentioned in Full Length Battens:-1.

As noted in Full Battens:-1, the Girth is the distance across a sail from the “same” points the luff and leech.

A quick glossary:

Girths: the distance across a sail from a POINT on the luff to the corresponding POINT the leech.

Point: the spot on the luff and leech of a sail corresponding to one of the following: 25, 50, 75 or 875. percent up from the foot. You need two points to get a girth

Girths are universally described as: (Reading up from the foot of the sail)

MGL–Mainsail Girth Lower: The girth at the bottom 25% POINTS

MGM–Mainsail Girth Middle–the width at the 50% POINTS

MGU–Mid Girth Upper–the girth at the 75% POINTS

MGT–Mainsail Girth Top–the girth at 87.5% POINTS

The most common way to start measuring the girths on your mainsail is to lay it out flat on the ground.

Lay the sail out flat on the ground.

This exercise works better with two or three people, in fact for race boat programs, modest ones where not every one knows everything….. it is a nice little team building exercise for the winter. You can measure all of the sails so every one on board has an idea of what sizes the sails are. In this case though I used a screw driver pushed through the cunningham eye into the grass.

Secure the tack with, in this case, a screwdriver pressed into the soil.

Take the head of the sail and fold it down to the tack. Jiggle the luff so that the top and bottom of the sail are straight like folding a sheet or towel and make a mark where the fold is. This is the MGM luff POINT

Fold the sail so the head comes down to where the tack is.

Make sure the two corners, the head and tack and then the head and clew are even.

The corners of the head and the tack need to be overlapped on top of each other.

Mark the fold in the sail with a pencil, a regular #2 is fine.

Make a pencil mark on the sail under the fold.

If you merely want the MGM, fold the head over to the clew, straighten out the leech and mark where the fold is on the leech.

Next take the head over to the clew and lign the corners up as for the tack.

Next take the head over to the clew and line up the corners as for the tack.

At this point, you can if you wish unfold the sail and lay a tape across the sail between the luff point and the leech point. You now have the Mainsail Mid Girth, MGM or 50% girth usually spoken as “the mid girth.” As a practical matter when measuring sails it is better to mark all the points along one edge first then do all the corresponding points on the other edge.

The MGM is measured from the mid point luff to mid point leech.

To get the 3/4 and .875 girths, fold the head back to the MGM point as shown below.The picture below shows the 75% girth position on the leech. When you measure the 75% girth point(s) on the luff and leech you can measure across the sail and you now have your 75% girth or MGU, Mainsail Upper Girth.

With the sail folded in its original half, fold the head back so that the head meets the MGM fold. This determines the 3/4 girth, MGU

By continuing to fold the sail back and forth, you can also get the .875% girth too, as necessary

Fold the sail back one more time to get the .875% girth too, as necessary

From the 75% fold, fold the head back one more time to get the .875% point, as necessary. If you do the same drill with first the tack and then the clew folded to the half way fold you will get the dimension for the MGL, Mainsail Girth Lower.

It takes all of 15-20 minutes, to do this from pulling the sail out of the bag to getting it back into the bag and recording the dimensions but this does depend on the size of the sail, where you are doing it and how many people are involved.

Remember that to meet MOST racing rating rules the girths must meet the lengths equal to the percentage of the foot as outlined in Full Battens-2 Scroll down about half way.

Sailmakers use all of this information regardless of what kind of mainsail they are designing. For cruising boats, you and the sailmaker need this information in order to make the sail so it does not overlap the backstay too much UNLESS this is something you have discussed with them.[ See here: Scroll down to the bottom two images]. It is necessary too for in boom mainsails because these booms are very precise on how much roach a sail can have-Too much and it will not roll properly. The roller booms come with a 30 (or so) page manual for the sailmakers. With the advent of battens for in-mast sails girths come into play too. For race sails, even for Wednesday night racing, of course you want the sail to be legal.

If you are taking the measurements off the boat yourself one thing they may ask for is the distance from the gooseneck, aft and parallel with the boom, to the backstay. In other words the position on the backstay where the boom would intersect the backstay ( if it was that long) If this distance does not have its own check box in the measuring form, make a note in the “comments” section of the form. These dimensions give the sail designer a triangle that outlines the area in which the sail might fit, unless you have come to terms with them for something else-Like a oversized roach. In other words a triangle with sides: Luff, the distance from head to boom/backstay intersect AND distance boom /backstay intersect. With this information the sail designer can place the backstay on the design software and so know where the girths are going to be relative to the backstay.

One last detail regarding girths….

Girths can obviously have an impact on how much ROACH a sail has, BUT remember that the sail designer needs to take into account mast bend too. Sails have shaping in the luff and on a mainsail it is generally called luff ROUND, or sometimes positive, because it protrudes forward. The opposite is hollow, or negative.

In this picture of the Laser sail, you can see the luff ROUND outside the straight line between the head and tack.

The relationship between ROACH and LUFF ROUND varies depending on many things but boat type, rig type, fractional Vs. masthead, degree of mast bend on either are some of the main ones. At the end of the day, the girths are one of the variables a sailmaker uses when determining how to design a sail and they have an impact on the sails roach. And the roach has an impact on whether or not the sail needs, or requires full length battens and if so what kind of sliders and related hardware is desirable.

These measuring protocols are the same for head sails and spinnakers. Remember this when we get to Code zeros in a while.

Full Length Battens-1: What they do, don’t do and why

Posted on November 16, 2013 by Joe Cooper

A very common opinion regarding Full Length Battens is that they improve performance. Let’s look at that theory for a moment.

The square head main provides more area but something more too-Read on.

A mainsail with FLB has either has been refitted with Full Length Battens (FLB) or it is built from scratch as a new sail with FLB’s. There are a couple of things that happen in these two scenarios that lead to the “better performance” theory.

If an old main is retro-fit with FLB, one assumes there is a reason for it and it is usually to “improve the shape” often in conjunction with the owner’s desire to get another couple of seasons out of an old sail. We know that a sail’s shape degrades over time/use. Typically the original designed-in shape migrates to the aft part of the sail,or aft of where one would like it to be for optimum performance. The of course happens over time and so more or less creeps up on you. The observant owner will note that the shape IS migrating but more commonly he/she sees boats he used to be able to beat, sail past him, either racing or “not racing” if such a condition does in fact exist with two boats within sight of each other….. After the FLB retro fit, ideally done in such a way to “push” the shaping back towards where it needs to be, commonly the sail is now “faster” than before. After all that is what the owner spent a not small amount of money on.

Most sail boats are constrained either by the backstay or a rating rule or often both. This Sabre 38 main just overlaps the backstay at the top batten by about 4 inches. See the profile picture below

Thus there is a connection in the owners mind that FLB are faster than Non-FLB…

So the meme is that FLB are faster. Well kind of.

What happens if a new sail is ordered WITH full length battens? A few things:

Today there is a much greater likelihood that the roach on a mainsail designed within the past 10 years or so is going to larger than one from before that time. Sail making design uses lots of input from “racing” sails even when designing non-race sails and it is my experience that when an owner comes to replacing a sail for the same boat, and with Hood it might have been a fifteen or twenty year old sail, that the roach on the new sail is significantly greater than the old sail. More sail area never hurt any boat in the search for speed.

This sail has full length battens but could easily support the roach with “regular” battens

Second, simply having a new sail you are going to be faster than with an old sail-Just ask any one design sailor. Connected to this is the improvement in sail making materials, both Dacron and the rest of the fibers and manufacturing techniques for laminated sails.

Third, the above cited “improvements” in shaping ideas (and more powerful and detailed sail design software) can also come from a sail designer with a greater or different, skill, experience, attitude to designing a sail.

Another way to look at this question is to study for instance the J-105’s. They are a very competitive one design class with fleets all over the place. If one postulates that FLB ARE faster, then in theory all J-105’s would have full length battens. BUT even though the batten length is not restricted, or even mentioned in this class at least according to the class rules of 12 Feb 2012, section 6 to 6.4.1 Mainsails, if FLB WERE faster, then one would expect to see, in such a close racing fleet as the 105’s, all boats using FLB. But they are not. So what does this say about the performance of FPB? Are the FLB really “faster”?

Thus we now have a new sail with superior (compared to 10, 15, 20 years ago) shape holding properties. It is “bigger”, is almost certainly of a different design. AND it also has full length battens.

But which characteristic is making the sail faster? Is it the material, design(er), the extra roach, the newness of the sail and performance of the material or the battens?

Another detail to contemplate here is that the real advantage of FLB is the ability to support a bigger roach. This is doable in the majority of the boats on the market in the production arena but it is constrained by at least two things: Backstays and rating rules.

This Apogee 50 is used for cruising AND racing upgraded this older Hood Main. The new one was made to the largest possible "girths" and so is much bigger than this one

This Apogee 50 is used for cruising AND racing upgraded this older Hood Main which was about 12-13 years old and had seen lots ocean cruising miles. It was not designed with “girths” in mind. The new mainsail was made to the largest possible girths (for DH racing) and so is bigger than the old one pictured above..

Rating rules: as anyone who races even casually is aware one needs a handicap rating for their boat. One of the items in a rating is of course how big the sails are. A mainsail is measured not only by the P and the E but by at least one and up to as many as four so called “girths”. Briefly a girth is a dimension from a specified point on the luff, at a minimum 50% of the luff length across the width of the sail to the corresponding position on the leech that is 50% between the head and clew. Boats that are raced regularly are measured at 25%, 50%, 75% and sometimes 87.5% locations, reading up from the foot. At each measurement point the mainsail cannot be wider than a percentage of the foot. The current versions of these width percentages are:

MGT: The 7/8 point– 0.22% of E

MGU: next one down, ¾ points– 0.38% of E

MGM: Middle 50%–0.67% of E

MGL: the bottom ¼ points—0.89% of E.

Try this math on your own mainsail. There is a formula in the ORR rule for calculating the actual area including roach, if you have these measurements. Calculate the mainsail area: P x E x 0.5 which gives the basic triangle area. The inclusion of the girths gives the actual area. As a rule of thumb actual area is abut 20% more area than the basic triangle area.

The width of the mainsail on the majority of boats is constrained by either the backstay or a rating requirement. This mainsail for a Sabre 38 is built to the maximum girths permitted by the PHRF of New England. If you look carefully, the upper leech is just overlapping the backstay by an about 4 inches.

The width of the mainsail on the majority of boats is constrained by either the backstay or a rating requirement. This Sabre 38 mainsail is built to the maximum girths permitted by the PHRF of New England. If you look carefully, the upper leech adjacent to the top batten, is just overlapping the backstay by about 4 inches.

Generally speaking these girth requirements constrain the width of the average mainsail to what we all commonly see on boats unless they are multi-hulls or open class offshore race boats, or high performance skiffs of the Sydney Harbor 18 footer type. That is a pretty basic triangle, like the one on the Sabre pictured above.

Backstays: The next item that constrains boats from having really big roaches is the backstay. Yes some boats come out of the box with provision for large roach mainsail and I am thinking of the Quest line of performance cruisers and race boats, designed by Rodger Martin and built by Holby Marine thru the 1990’s. They and others have girth restraints that allow for a wider main than those cited above, but the general rule for the vast majority of boats confirm to the cited percentages.

This cruising main has a very conservative roach, almost nothing. The owners commissioned a new sail and specified a much larger roach, so big in fact that when tacking they had to lower the mainsail a few feet. Notice the backstay is very close to the end of the boom which limits the roach/upper girths if you do not want the roach to hit the backstay.

The interesting thing is these “regular” girths, from the formulas above, keep the roach of the mainsail on most boats to just about where the backstay is plus or minus a few inches usually.

A large roach mainsail for a cruising boat. The roach is so big the mainsail must be lowered to tack, this at the owners request.

A (new) large roach mainsail for the cruising boat pictured above. The roach is so big the mainsail must be lowered to tack, this at the owners request. The backstay is indicated by the red line that terminates in the bottom right hand corner of the image.

Some cruising boats, most prominently the Deerfoot range of fast offshore cruising boats pioneered by the Dashews have much larger roaches BUT their rig layout, allows for this. The backstay is a long way aft of the end of the boom, so the roach can be big without fouling the backstay.

So bearing in mind all the foregoing, as to the question as to when FLB’s “might” be faster, one has to get outside the scope of “normal” racing rules, PHRF, IRC, ORR and so on and look at open class boats and other high performance boats-Aussie and Kiwi skiffs, most performance multi-hulls and so on. Here we find a mainsail, that has FLB but most commonly another feature not seen on the usual production cruiser racer or plain cruising boats-Square head mainsails.

The yellow line leading from the head, at the bottom of the image, to the clew at the top, is the straight line leech. All the sail to the image left of this line is roach. This of course requires considerable detail (read cost) in making sure the sail will be robust enough for hard offshore work typical of Deer foot owners. The blue line at the head is part of the tackle for the leech line which leads over the head of the sail so it can be adjusted at the tack.

The so called Square Head mainsail seen in the image at the top of this essay, takes advantage of the unrestricted nature of the sail area calculus of open class offshore boats and the various skiff classes’ by providing certainly more sail area, but also reducing drag at the top of the mast. This topic we will take up in Full Length Battens-3

Full length Battens

Image

YES, NO, MAYBE, WHY?

The subject of full length battens and whether or not you and your boat need them is one of the longer discussions sailmakers and their customers have. Like much else around the boat, there are plusses & minuses and maybes’ and what if’s. This series is intended to outline the various issues to be contemplated when you get the idea to have full length battens on your boat or new sail.

Briefly

What they can do:

A Class 40 with a so called Square Head mainsail

a) Full length battens can support a more pronounced roach than a sail without full length battens.

b) They can be retrofitted to revive the shape in an older sail

c) They can make the mainsail “smoother” minimizing bumps, creases or hard spots at the forward end of short battens

d) Maybe easier to flake and fold

Side rails to attach lazy jacks to.

e) They can make capturing the sail as it is lowered less of a dance IF the boat has either a Dutchman OR a dedicated Lazy Jack’s system designed for the sail

f) Reduce drag at the top of the spar, square head only

g) They make the sound of the sail flapping less loud which has its own many benefits above the longevity of the sail fabric.

Issues to consider:

a) Make the sail jump into its kennel all by itself–NOT

b) Rating issues (if you do any kind of racing, an “oversized” mainsail will get a new handicap allowing for the perceived speed gain) with oversize roach, except when purely cruising or sailing open classes.

c) Are they really faster as some have remarked?

d) In the case of the large roach/square head sail the compression on the luff from the batten is considerable.

e) Chafe esp. with aft swept spreaders. Also the batten pocket OR sail will chafe where the batten crosses the lee rigging when sailing down wind. It is perfectly possible to saw a hole through a sail overnight (I have inspected a sail so damaged) if this is not either addressed on the boat or in the construction phase of the sail.

f) Whether to employ luff loading batten pockets or not. By this device the battens are inserted in the luff end of the sail with the leech end sewn shut thus making it really hard, as in you must really try to shake the batten out of the back of the sail. Much harder but not impossible.

g) The larger the boat (mainsail) the more likely the sail needs low friction track and cars.

h) Additional costs related to the detailing on the sail and the cost of the hardware.

A selection of available batten hardware

i) Value versus regular length battens

j) Potential for damage when sailing-Like an all standing gybe where the sail lands up against the formerly windward runner usually with a great shock.

k) The material from which the battens are made, there are mainly three flavors.

l) Carrying spare (battens and parts) on voyages including the stowage on board, the shipping if necessary, the ease with which a long batten can be removed from the sail if the batten breaks

Batten sliding systems

There are two categories:

Those using a dedicated track and
Ronstan track and car system
Those that do not have a dedicated track but rather the “cars” run in the mast’s original track/groove.

Within “A”: there are two sub-decisions, ball bearing cars and slider cars without bearings.

Within “B” there is one variation from the almost universal use of simply some kind of slippery plastic and that is a car that has bearings incorporated into the car itself. I am aware of only two products that fit this last description.

Components

There are three components to the fully battened system.

The “cars” these may be simply a beefier version of the sail slug/slide the sailmakers might use anyway on a small boat’s mainsail. OR on bigger installations with ball bearing cars they are substantial pieces of engineering.
The “batten box”, aka batten receptacle. The device into which the forward end of the batten is captured. This is in turn attached to the car by:
Toggle”, aka universal. This can be as simple as webbing on a small sail or as complex as an unlimited multi axis universal ball joint on bigger hardware/boats.

There are of course all manner of small parts, screws bolts, nut, balls or slider inserts that are included in the various parts outlined above, but you get the idea

Do I want them or not?

Considering all the above the rational human would surely ask him/herself do I really want this headache versus what will I gain from having full length battens?

Read on.

Storm Jibs and Solent Stays

Posted on May 28, 2013 by Joe Cooper

Regular readers will know of my enthusiasm for Solent stays as a great “Gear Change” for most conventional sailing boats. The Solent is particularly effective if the boat in question has a low aspect-ratio rig. That is the height divided by the J-this distance is roughly the forward side of mast at deck level forward to the head-stay fitting on the deck. So for instance a spar height (commonly referred to by riggers, mast makers & sailmakers as the “I”) of say 45 feet and a J of 15, is a three: one aspect ratio. A boat with a 47’ x 12’ rig is close to 4:1 aspect ratio.

And yes a tall skinny sail is just fine more or less—When sailing up wind close hauled—Only. For the average cruising boat high aspect-ratio sails are not so good. This has to do with both the strain on the head of the sail: the top of the sail tends to go very round in the head pretty quickly and more importantly, when the sheet is eased, the top of the sail twists off dramatically. When adding foresails to the inventory, an owner would be well advised to consider the aspect ratio of the where the sail is to set.

Quest 30 arriving in Newport. Headsail in use is the primary sail on the furler. You can see that the sail is relatively tall and skinny

With this in mind I have been working on just such a problem over the past month or so. A mate of mine is preparing his Quest 30 for the Bermuda 1-2—a solo race to Bermuda from Newport, RI then a DH race back from Bermuda to Newport. The Quest has an “I” of 41.0 feet and a “J” of 10.7 feet so again close to 4:1. Since the boat is to be sailing the ocean, simply relying on only one headsail on the furler to sail across the most likely spectrum of winds between Newport and Bermuda in June is not a sound seaman like option. Especially with this type of furler which is merely a furler, not a reefing headstay.

The boat does not readily allow of a Solent set up, in the classic fashion–Roughly parallel to the headstay and a foot aft. Thus I had to design a system for setting a small sail that ended up being a Solent hybrid. A cross between a “cutter” stay and a Solent. In this case the bottom of the stay lands very close to the stem head of the boat, like a Solent stay would. BUT the top of the stay lands at the second (top) spreader in the way a conventional Cutter stay might. There are a few reasons for this.

Primarily the fact that the spar had already the fittings necessary for a stay, runners, a sheave box and the halyard all at the top spreader-See image above.

So there were a lot of the basics for a stay on which a small sail could be set, with out re-designing the entire mast and deck layout. Overall my goal was:

Design a system that could be deployed easily quickly and with the least amount of ruckus given that when it is going to be used, it will be blowing at least 25 kts.
Ideally the installation made use of the various equipment already installed and available on the boat-We did not have time or inclination to get into the boat building business.
Do it in a way that was cost effective, the more so since the entire staysail arrangement would only be rigged up on the spar and deck and perhaps not even deployed at all, every two years for the Bermuda 1-2. The rest of the time it will live in a bag in a locker somewhere.
Get it all designed, fabricated, installed and sea trialed as soon as could be done so any adjustments could be done in a timely given the start of the B-12 is 08 June.

There was also a fitting on the fore deck, very well secured to the aft edge of the anchor well, as is common however using this was not viable for several reasons I will get to.

I know this boat, intimately as it turns out:(I sailed this boat to Plymouth, UK in April 1996 so the then owner could sail it back in the OSTAR-But that is another story) So my first question was to look at the rest of the sail inventory to discover what headsails were to be carried in the race?

The primary headsail is a 105% or so slightly high clewed jib set on a roller.
The mainsail has three reefs. The head of the mainsail is below the top spreader when the third reef is set-Watch for this detail later-on in this post.
There is a small sail called a storm jib, but having used this sail on the boat, I know it is a useless in practice. It is the wrong geometry completely.
The boat has water ballast. This is in effect another gear/reef. As the wind comes on, rather than reefing, filling the water tanks is the equivalent of reducing sail.

The primary 105% furling headsail sets on a furler at the stem head, like normal, but not on a “normal” Harken type furler with a foil. It sets on a Facnor 4500 foil-less furler. As the images below show, the furler is very simple:

There is a stay made from 1×19 wire as is pretty normal. The tack of the sail attaches to the drum–You can see the horizontal pin with the key ring and light line holding it to the boat in the above picture. The drum is driven by an endless loop line (led aft) that rotates the drum and so the wire: the head swivel rotates freely. The sail is attached to the stay by the soft hanks made of Velcro.

The sail is attached to the stay by “soft hanks” made of webbing and velcro

The idea here is to get the best of two worlds. A sail that can be furled, most of the time, BUT when it needs to be removed, it can be unrolled and lowered to the deck like a sail, with, well hanks-Just like the old days-So the sail is not going to blow all over the foredeck life lines and end up in the water.

The furler for the primary headsail is an foil-less furler. The Jib uses soft hanks connected over the wire stay. The grey cylinder is the top swivel

The white material aft of the drum attached to the tackle is a strop we fabricated to pass through the deck and connect to the headstay pin. To minimize chafe we installed a through-hull fitting into the deck for the strop to pass through. We attached a Wichard eye to the headstay pin and secured the strop to the eye with a soft shackle–The image seen below is a light line we used to line up the hole through the deck to the headstay pin.

To anchor the bottom end of the stay, we threaded an eye to the aft end of the pin holding the headstay to the boat. The light line is a guide we used to line up the angle of the stay through the deck with the eye fitting so we could get the right location in the deck for the stay strop to pass thru.

BUT

In practice I cannot see unrolling this sail lowering it, (the material is pretty stiff and the sail has vertical battens-as seen in the top picture sailing into Newport Harbor), lowering it to the deck, removing the battens, flaking the sail, getting it in a bag, releasing the hanks, pulling the tack pin out, un-shackling the head of the sail from the swivel, without losing the shackle, getting the whole show below without losing anything over board, including yourself, getting banged up yourself and then finally reversing the process with another small sail.

I cannot see that process talking less than an half an hour per sail even on a 30 footer.

So as a practical matter, the primary headsail would be furled up and a smaller sail set so the boat needed an inside stay.

A quick scan of the possibilities indicated that the best option would be to have a sail set from the top spreaders and landing just aft of the head-stay. Some of the issues to do with this that needed to be addressed included:

The main furler is installed below decks in the anchor well, so immediately aft of the forestay, there is nothing meaty enough to land a stay on.
Since the sail would go to the top spreaders, the rig would need running back-stays
If the small sail was to be set on the foredeck, at the aft end of the anchor locker, then the aspect ratio would be too tall and skinny-Not good geometry for a hard air sail, to be used in the ocean. The aspect ration of this triangle is over 3.5:1-too tall and skinny.

The pad eye in the foredeck was too far aft to either make for a good shaped sail nor would it be big enough, as can be seen in the picture below.

This image shows the location of the one pad eye aft of the stem, at the aft end of the anchor locker. (far left of picture) This was unsuitable because to install the stay tensioning tackle properly would have needed another couple of pad eyes AND the sail would be too small AND not very good geometry–Too high aspect. The results of what we did-Install a tackle and stay just abaft the stem-head, can be seen in this image.

“Normally” inside stays for most cruising boats today (although I am apparently single-handedly changing this), of any flavor use some kind of mechanical ratchet crank device or a Hy-Field lever. Both of these options are:

Heavy, difficult to handle, very difficult to tension after a while when everything as stretched in, and being heavy are awkward to man-handle around the foredeck when needed. They cannot be removed in a hurry as circumstances dictate.

A Wichard hand crank adjuster on the Solent stay on a 44 footer, using a wire stay-This particular wire stay has been replaced by a textile stay that weights 5 pounds. Handling the crank, stay and a sail is way too much work and being heavy throws a lot of inertia around in the seaway that will be in evidence when this equipment is in use.

At the end of the day I designed a set up as follows:

Textile stay fabricated from a Spectra fiber product known to Hall Rigging, who made it for me, as Fiber wire.

The Fiber Wire stay. The keys are to give idea of scale. The “T” fitting is visible on the right hand side

This stay attached to the spar using a T fitting, seen above

The bottom end of the stay was tensioned by a 4:1 tackle running through Antal thimbles.

The stay is tensioned by a 4:1 tackle running through Antal thimbles

The tensioning line is dead ended on the port side and runs aft, through the pad eye on the starboard side to a clutch in front of another Antal thimble and from there the tail is long enough to go to any winch.

The stay is tensioned by a 4:1 tackle running through Antal thimbles. Since the line is not required to be adjusted all the time, the thimbles are perfect. They are light, strong, in-expensive in general and particularly when compared to a ball bearing block of equal strength, the latter by perhaps a factor of 10:1.
The knobby ball of cordage connecting the stay to the top thimble is a “soft shackle” an increasingly widely used device for attaching anything to something else, as one would with a stainless shackle

There are a pair of running backstays connected to the spar.

The running backstays are attached to the mast just below the upper spreaders and opposite the point where the inside stay connects to the spar. This is high enough that with the third ref in, the head of the sail is below the runners. The end of the boom is far enough forward that both runners can be set up and the boat can be gybed and tacked without handling the runners. An extra insurance policy on hard conditions.

These are tensioned by a 2:1 tackle led through Antal thimbles, to a clutch, thimble and again with enough tail to get to any winch.

I used himbles again on the flying part of the runners: They are light (does not hurt so much when it hits you in the head….)strong & inexpensive-A trifecta that is hard to beat.

The running backstays are led through a thimble secured on the transom and forward through a clutch to another thimble permitting any winch to be used to tension them

The serendipitous aspect of the runners and where they land in the spar is that with the third reef in the mainsail the head of the sail is below where the runners attach to the mast AND the runners are sufficiently aft of the end of the boom, so BOTH runners can be set up when it is really howling and the boat can be tacked or gybed without attending to the runners. In this configuration the assumption is the inside stay will be deployed so the spar has another level of security to defend against damage.

The runner tails are dead ended on the same chain plate as the standing backstay, led up through the flying part of the runners, back to a thimble and forward through a clutch, thimble and so to any winch available.

Sails-Mainsail, measuring-E dimension

Posted on July 18, 2012 by Joe Cooper

In a previous post I discussed the “P” dimension and the parameters surrounding the correct luff length; This post discusses the “E” dimension.
The “E” dimension is the second dimension (the first being “P”) that the boat’s designer uses in order to arrive at a mainsail size that he wants, in order for the boat to do what the person who commissioned the boat wants to do.

The “E” is for the purposes of 99% of the folks reading this essay, the distance from the aft face of the mast, aft along the boom, with the boom at right angles to the mast, to the inside (forward) edge of a contrasting colored band at the aft end of the boom”. For the other 1%, there are some minute variations on this definition, under the ORR rule.

Again, like the P dimension, the E is NOT the foot length of the actual sail and it is NOT the actual boom length. The reason the P and the E are not the actual sail edge length has to to do with two primary issues. One is the hardware (on the mast and boom) by which the sail is physically attached to the spars and two, in most cases there is a deduction for stretch that sailmakers take or apply to a sail when designing it. This deduction is commonly different for each edge too.
As for the “P” let’s start with the “Black Bands.”

Some of these bands look like this.

Black band at the aft end of a Selden boom on a Caliber 40

And here (below) although the paint or black tape is wearing off in this picture:

Black band at the clew end of the boom, Cal 36

Notice too in the above picture there is some space aft of the black band that “could” be used for sail outhaul. On the boom in the top picture the outhaul mechanism is fully extended, “two blocked”, as we might say, and the (bearing surface of the) shackle is just at the band.

And sometimes there is NO band. As here:

Finding a boat without bands is pretty common, as on this Bristol 29-9

This next picture shows a detail than can be tricky:

Black band at the clew on a 30 footer

Observe (in the above picture) just aft of the stainless fitting with the halyard attached, in the boom tunnel, there are a couple of unidentifiable fittings? These are the swages connecting the outhaul wire to the outhaul fitting. There is just enough room aft of the black band to apply some more tension before the swage gets sucked into the sheaves, like is happening on the boom shown below.

Sabre 38 clew band and outhaul mechanism. On this boat the swage is pulled right into the sheave with the shackle at the band. See how the swage is bending?

So to recap:

The E is NOT the sail’s foot length

It is NOT how long the Boom is

It is the distance from the aft face of the mast, aft, to the forward edge of a colored band on the boom.

It is not uncommon for there to not be a colored band particularly on “cruising ” boats rigs.

I will discuss the particulars of four other sail making details in a future post.

Tack Set Back, Tack Set UP, Reef ring set back & Clew set up

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Category Archives: SAILS