Mast bend and mainsail shape

Bending the mast is a fast and simple way of managing the power on your sail boat

As discussed here mast-rake and mast bend are two different aspects of mast “tune” that affect the boats balance and so feel and ultimately performance. This essay discusses mast BEND. There is an element of headsail shaping connected to mast bend but we will get to that in future posts.There are other tools in the mainsail shaping tool box, but this essay is about mast bend

The Basics:

More wind requires a flatter sail

Less wind prefers a fuller sail.

Mainsails have shaping both across the sail (broad seaming) and at the luff, known as Luff Curve

This “curve” is intimately connected with the characteristics of the mast, and so, of the boat. There are differences in the amount of luff curve required between masthead and fractional rigs, masts with spreaders in line–that is to say where the cap shrouds are perpendicular to the mast-Or with “swept back” spreaders, such as many newer boats have.

Some Definitions:

Chord: Is an imaginary line between the luff and the leech

Depth: (and draft, camber & shape-They are quite synonymous and generally used interchangeably by Sailmakers in their jargon) is that distance, perpendicular to the chord line, at which the sail’s surface is furthest away from the chord line.

In the sketch below:

The line ZZ is the chord line.

The portion “C” is the chord LENGTH on the sail.

The distance “a” is the chord DEPTH (draft camber shape…).

The distance “b” is the POSITION of the draft measured aft of the leading edge of the foil which is in this case to the right of the image. Thus a/c is the draft and b/c is it’s position.

Chord (length) draft and location of draft are all depicted in this image.

Chord (length) draft and location of draft are all depicted in this image.

Power: over and under (powered)

Power (force, energy …wind speed) is what gives the sensations you feel thru the wheel or tiller and via the heel angle of the boat. With headsails, managing the power is relatively easy: Too much power, then put up the small (er) one-Or more likely today either partially roll up the genoa or roll it up all the way and motor-sail.

Sail size and shape:

Having the right (sized) sails of the right shape for the conditions is, for those who prefer to sail for the sensations of how the boat feels thru the tiller/wheel, a key part of this sensation. Too much sail and/or sails that are too full makes the helm feel heavy and generates too much weather helm. In this condition the boat heels more than you want and always inclined to want to round up. This is of course unpleasant, occasionally quite noisy, slow and not infrequently intimidating for some on board.

The sensations of being underpowered are less dramatic, noisy, violent and so less intimidating.

Power on a sailing boat comes of course from the sails. Having the right shape in the sails is therefore key to getting the boat to “feel good” and sail well.

Managing the power

One tool in the box of adjustments available to sailors is adjusting the camber of the mainsail-What many folks refer to as the belly of the sail. Camber is the “depth” of a sail at a given point on the sail. (NB when we/you say the sail is blown out, usually this refers to the draft being further than 50% aft on the sail)

This picture shows me and a high school intern measuring the draft amount and location on a 420 mainsail strung up in the loft.

This picture shows me and a high school intern measuring the draft , the amount and its location on a 420 mainsail strung up in the loft.

The camber on any foil is expressed as an amount, at a location. So you might hear Sailmakers say something like…”it was 8% at 35% aft.” This means that what they were looking at was 8% of the fore and aft span (of the chord line) perpendicular from that line and that position was 35% aft, from the luff. Translated: the sail was 8% deep at 35% aft.

Another picture of working with Tristan discussing issues surrounding sail shape: Chord, draft position and so on.

Working with the intern and discussing issues surrounding sail shape: Chord, draft position and so on. This sail looks quite full because the mast is not bent.

So for example if the chord span (“c” above) was 10 feet and 8% of 10 feet is 9.6 inches so the sail surface was (“a” above) 9.6 inches away from the Chord line, and this point is (“b” above) 3 and a-half feet aft along the span from the leading edge.

So far so good?

Luff round

Now sails are not just triangular (Yes, mainsails have roach but many/most “cruising boat” sails have very little), the point is they are curved at the luff too. This is called, no surprise, “luff curve or luff round”. How much curve and at what position on the luff and how these points is determined are all components of the sail’s design.

On this J 30 main, the area of the sail to the left of the left hand tape is called  luff round. There is a lot of it on a J 30 because they have relatively bendy masts, especially above the hounds.

On this J-30 main, the area of the sail to the left of the left hand tape is called luff round. There is a lot of it on a J-30 because they have relatively bendy masts, especially above the hounds.

Luff round and mast bend are intimately connected. If the luff curve and the mast bend “match” is correct, you have a 6-speed stick shift gearbox. If the mainsail luff curve and the mast bend are not mated, pretty closely, then you have a 1953 shift on the column three speed with no fluid in the transmission, as it were. It is really critical and the more performance oriented the boat the more critical it becomes. AND this is why having a back stay adjuster (and knowing how and when to use it) is a great thing to know, if you like sailing your boat, as opposed to being on while it is sailing.

Sketch of a mainsail set on a straight mast

Sketch of a mainsail set on a straight mast

Briefly stated, when you bend the mast, you can flatten the mainsail. A flatter sail is to be preferred in more wind. Flatter sails reduce power in the sail, that is reducing load on the tiller/wheel. When you bend the mast, in windier conditions you will feel the helm go lighter, all other things being equal.

Mast bend flattens the mainsail

Mast bend flattens the mainsail. When the mast is straight …”straight mast” the sail is fuller. When the mast is bent, as at point “a”, the luff curve gets pulled forward and so flattens the sail.

 

Mast bend on the 12 meter Australlia ion 1980

Mast bend on the 12 meter Australlia in 1980. The defender, Freedom is to weather.

The picture above shows the 12 meters Australia and Freedom coming off the starting line in one of the 1980 races for the America’s Cup. The Australians had fabricated a fiberglass top to one of their spars that would bend much more dramatically than an aluminium one. The top of the mast was controllable, apart from the regular topmast backstay, by “jumpers” and “diamonds” all controlled by hydraulics in the mainsheet trimmers cockpit. It gave the boat the abiity to have more mainsail and the rounder shape to the top of the mast was more efficient. In under about 9 kts of wind we were faster than Freedom. We won one race and were in front by 20 minutes when the time limit expired.

The large roach not withstanding, study the luff on the let. IT has a degree of "luff curve". This will match the mast bend on the boat and so be used to de-power the sail.

The large roach not withstanding, study the luff on the left. It has a degree of “luff curve” about 6 inches to my eye. This will match the mast bend on the boat and so be used to de-power the sail.

If you do not have any mechanism to bend the mast, consider adding a way to do so. For almost all boats there are a variety of pretty simple solutions.  If you cannot find one or need help, contact me….It is not impossible that the money spent on such a set up will be good value with respect to making the boat more agreeable to sail in breeze and so less uncomfortable for all hands.

 

 

 

Mast bend, the use of the backstay, OR topmast running backstays, to adjust the shape of mainsail and headsail.

 

Running backstays, commonly called simply “runners” are used not only to oppose the cutter stay on boats so rigged, they can also be used as a fine tune for mast, and so, sail shape.

During the course of the series on Full Length Battens, I received an email question from a fellow named Chris who owns a Condor 40 Trimaran. This post is more of a one way monologue with me answering his question rather than the usual essay but the information is all valid regardless.

This fellow is asking basically a sail shaping question.

His note to me in italic red, my comments in bold black. His question in blue italics.

Very interesting article Joe. On my condor-40 tri I have no back stay (Cooper comments: Not in the sense mono-hull owners recognize a backstay. He has two, one on each side so, among other things, his mainsail can have a big(er) roach unencumbered by a single standing backstay) and my spreaders are swept back however they are set up supporting diamond wires never connecting to the deck. (Cooper comments: These are known as Diamonds and are rarely seen on most normal “yachts”-Multi hulls and various skiff classes, yes, for all sorts of reasons.)

My side stays (Cooper comments: What mono-hull sailors would recognize as the “cap shrouds”) run from the top of the mast to the amas and are aft of the mast base eliminating the need for a fixed back stay. I do have running back stays (Cooper comments: Language or choice of words is important here: What he calls “running backstays” are almost certainly “TOPMAST running backstays”, again to do with the roach-see above)  that are combined with an intermediate running back stay. Both runners are adjusted via a 2-1 purchase and then a 2 speed wench. The intermediate runners also have their own adjustment via an 8-1 car assembly on the cabin top. All very slick. My question since these are new to me is how do I know how much tension to load the primary and secondary running back stays? And with my wide boat I have bunji cord that pulls the unburdened back stay far to the side so it does not chafe the sail in most points of sail. Thanks in advance. Oh yes Happy Thanksgiving today.

End of his note to me.

A closer look at the type of detail Chris is describing-Topmast runners AND lower or check stays attached to the topmast backstays

A closer look at the type of detail Chris is describing-Topmast runners AND lower or check stays attached to the topmast backstays. You can see the adjustment tackle on the lower, intermediate “check” stay. Because this boat is small, a Mini 650, it is possible to adjust this stay using this tackle most of the time.

I understood/understand the bulk of his description on the runners. What I did not quite get is this statement:

“The intermediate runners also have their own adjustment via an 8-1 car assembly on the cabin top”.

If the intermediates runners are connected to the topmast runners like the arrangement on the Mini pictured above…How do the lower ones, the intermediates, get to the cabin top? Do they for instance go into the mast then down and out and aft, like a halyard? This would give you the option of adjusting the intermediates while not adjusting the topmast stay. This has done on occasion on mono-hulls, although it is losing because it is not every accurate because the spar can still move around the sheave in the mast. Ideally the runners and backstays connect directly to the spar so that once adjusted it stays adjusted.

Regardless this is the answer to your question:

Both runners are involved in sail trim, the overdrive or the “final gear” part of the overall sail trim as follows.

The topmast backstays will control the head-stay sag and mast bend  like the “regular” backstay on a mono-hull. And likewise the check stays (or lower runners or intermediate runners-Depends on what country the speaker is from…) will control the mast bend in the middle of the spar.

This shows the mainsail shape of a 45 footer, prior to being "set-up" for the (increasing) wind conditions. Follow alopng as the other images in this sequence show the mainsail getting flatter and smoother by use of the topmast backstay

This shows the mainsail shape of a 45 footer, prior to being “set-up” for the (increasing) wind conditions. The other image below shows the mainsail getting flatter and smoother by use of the topmast backstay. Here the sail is too full and there is not enough luff tension-Cunningham set up. The stings floating around are the lazyjacks.

 

Via these two adjustments the topmast backstay will tension the head-stay reducing stay sag and improving pointing and making the sail flatter. They can also contribute to the mast bend if the mast is so designed.

This is the final set up for this mainsail on this trial. IT is starting to blow back because the breeze went from 11kts. to about 16/17kts. in the time we were getting set up and the headsail had not been adjusted too match the harder breeze.

This is the final set up for this mainsail on this trial. You can see how the sail is flatter then in the previous image.It is starting to blow back because the breeze went from 11 kts. to about 16-17 kts. in the time we were getting set up and the headsail had not been adjusted too match the harder breeze. The bulk of this flattening was by virtue more backstay tension

The intermediate runner controls the mast bend in the middle of the spar. If the runner is tight, the mast will be straight. If the intermediate is not as tight the mast will bend a bit and so flatten the mainsail too.

Try this: At the dock one day set up the runners to what looks/feels like “normal”. Go forward and look up the mast to see what kind of bend there is, especially around the middle of the mast, where the intermediates connect.

TIP: You can usually reference this bend by securing the main halyard to the tack fitting and then putting a reasonable amount of tension on the halyard, to keep it tight and straight. Then measure the fore and aft length dimension of the spar. When doing these sightings, relate the fore and aft dimension of the spar to the distance between the back of the spar and the halyard. If it is, by eyeball about the same as the mast dimension then that is known as one diameter. So if the spar is 6 inches F&A, then you have 6 inches of mast bend at that point minus the amount the halyard is aft on the tack fitting.

This will give some idea of the idea behind sighting up the spar to determine mast bend.

This will give some idea of the idea behind sighting up the spar to determine mast bend.

Then go forward and wiggle the head-stay, to get a sense of how tight it is.

Return aft and tension the runners again so that there is a difference in the feel/load. Repeat steps above, sight the spar and feel the head-stay

If you are OK with it, go and tension the runners again to “Max” and repeat the sightings and wiggle.

THEN adjust the lower runner through, I am guessing, the tackle you refer to on the cabin top.

The question about “How much to load them” has a couple of answers.

1. You can go sailing in a variety of winds and adjust the settings until the boat feels best in that wind sped.

2. You can wind them up pretty tight and forget it-You probably will not pull anything off the deck, but it is always possible

3. You can spend a chunk of change on a digital load meter and put that on the runners or the headstay. Most of the high end sailing instrument makers have such a device that works with Navtec fittings. Personaly I would use the eyeball method.

In the big picture backstays (or a single normal backstay on a mono-hull)can be used to adjust the mainsail shape via the mast bend (in conjunction with intermediate runners if installed) and the head-stay sag. All of which are fine tune adjustments rather like the over drive on a car. How much load is applied varies with the basic shape of the sail the flexibility of the rig and a host of other variables.

Easy upgrades for short handed sailing

 

The link below goes to Wind Check magazine. You may know I write a monthly column for them. For this winter, they wanted me to write about some simple easy things owners might do over the winter to improve their lot when sailing, as most boats are, Short Handed.

Well I started out to do the 2 x the regular column (which is about 1,000 words) that they asked for, so about 2,000 words. At about 5,000 words I hove to and thought about the subject for a bit. In order to get in all the simple cheap(ish) easy things AND do justice to the two most important aspects of any sailing, this whole idea needed to be bigger. I think that in any sailing but short handed in particular, one must be really comfortable with handling the sails. This includes, for the mainsail, hoisting, lowering, reefing, shaking out the reef, and putting the sail away and cover on. Then there is the issue of roller furling headsails and their part in the big picture, then smaller sails for use when the breeze is over about 15  knots, down wind sails, and well you see where this was going. Each sail and method of handling it might be its own stand alone piece in one edition of the magazine.

I sent Chris Gill, the Editor at WindCheck a note suggesting he/we make this into a 3 or 4 part series so we can really get into the meat of the matter. We volleyed emails back and forth for half an hour and ended up with at least three and maybe four part series on the subject.

So this first part is some of the simple things one can do.  The other pieces will come along further into the winter, but early enough that you can still get a good deal on stuff at the boat shop if you find something you like.

I invite you to read it and study it. It is all from long experience, learned, often at 0230 on a cold raining dark and stormy night somewhere in the middle of nowhere blowing the blazes with something or another broke or looking to break.

Full Length Battens-4: The Hardware.

 

I hope the earlier essays have covered the issues surrounding the full batten question from the sail performance, efficiency & speed perspective.

The ease, or lack of it, with which a FB mainsail can be operated during the various maneuvers a crew must make while at sea full battens offer these advantages:

On boats with aft sweep to the spreaders, it is important to have the area where the batten pocket bears on the rigging to be reinforced with sacrificial chafe protection.

On boats with aft sweep to the spreaders, it is important to have the area where the batten pocket bears on the rigging to be reinforced with sacrificial chafe protection. This image shows just such protection on the pocket of a Deerfoot 60 mainsail Hood built. While chafe protection is a good detail to have on your sail when going of into the open ocean, it is more important on FLB sails due to the grinding effect the batten imparts on the stays, or anything else the batten and sail are bearing on.

 

  • The mainsail is much quieter when flogging the battens reduce the frequency at which the sail flaps-This is because the stiffness and mass of the batten resists the wind force more than a mere “cloth.”
  • The effect of the batten separating-pushing the luff from the leech makes it easier to get a hand full of sail and to some degree put it where you want it, particularly if there is some kind of boom bag for the sail to settle in.
  • Full battens are more effective at keeping the sail constrained between lazy jacks, even more so if the lazy jacks are located with respect to where the reef points and the batten’s leech ends are.

The real trick that makes ALL of this work as an integrated system is to mate the hardware to the boat, the sail and the intended use of the boat. This requires a combination of learning about the pluses and minuses of each version plus some other contemplation: Much of this information can be supplied by the sail makers and or rigger, but as with any business, they most likely have their own favorite hardware, mainly because they are used to in.

In no particular order some of the details to decide or to think about before even picking up the phone are:

  • Track or no track and
  • Ball bearings or no ball bearings.
  • Number of battens
  • Will the battens be installed from the Leech OR the luff
  • How the batten pockets will made to will resist chafe
  • How the sail is to be captured when it falls down
  • What you are realistically going to do with the boat/sails/battens–The further offshore you go, the higher value the most friction free gear you can get will be.
  • Stack height
  • Reefing details
Making sure the reefing system is coordinated with, in particular, the placement of the battens and cars is one of the  important details to get right.

Making sure the reefing system is coordinated with, in particular, the placement of the battens and cars is one of the important details to get right.

This installment will begin to cover the available hardware for making the most of the benefits of the full batten sail which are to my mind “ease of handling”. It should be noted that the bulk of the following information pertains to the hardware I have seen and or had experience with in the US.  Regardless of hardware the principles are the same.

First off a definition is in order for the idea of “ease of handling”

For this discussion ease of handling includes:

  • Any hardware-Tracks cars batten boxes etc.
  • Or sub-system-Lazy jacks boom bags etc.
  • Or technique, practice skill in handling the boat during sail handling activities

OR

  • That which makes the manhandling of the mainsail on the boom easier and/or less stressful, and/or safer, whether hoisting, lowering, reefing or unreefing.

Reefing in a seaway is potentially one of the most hazardous parts of sailing a boat. The crew is, often out of the cockpit, it is blowing, often quite hard, there is a sea running perhaps quite large and there is the personal  stress factor, both on the part of the crew member doing the work and the master worrying about his crew….

wx map 13 April 13

When your weather map looks like this you better be sure that all the gear, especially the sail handling gear, on your boat works 100%, is easy to work, fast,simple and tested.

Traditionally one of the hardest parts of dealing with a mainsail is the friction generated mainly by the slides operating in the track. This is closely followed with what to do with the bunt of the sail after the reef is secured. On modest sized boats this is not so much a problem. If the “Depth” of the reef is say 4,5,6,7 feet- and boat that has three reefs at 7 feet apart might have a rig close to 45-50+ high feet, so perhaps a 40 footer. Depending on all manner of variables it may be sufficient to let the bunt flap to leeward, although personally I would roll it up and tie it off. Boats with a larger gap between reefs of course get progressively larger; the size of everything goes up as do the loads and the weight of everything. The requirements, desirability and the cost (all equaling value) of using low(er) friction luff sliders increases with the size of the boat, the sail and owner’s horizons.

As if this writing, I identify the following categories of luff slide hardware-And yes all of it can be used with a conventional sail with just leech battens too. These categories are:

CARS/SLIDES: With ball bearings and without.

This is a Harken ball bearing car for the batten box to attach to. Originally the red dummy track was used to keep the balls in the car. This has been improved on now so that the balls are held captive in the cars, minimizing one of the great arguments against ball bearing cars.

This is a Harken ball bearing car for the batten box to attach to. Originally the red dummy track was used to keep the balls in the car. This has been improved on now so that the balls are held captive in the cars, minimizing one of the great arguments against ball bearing cars.

Antal track slider & Toggle with Antal leech loading batten box.

This is Antal track slider & Toggle with Antal leech loading batten box.

TRACK: Those that employ a dedicated track that needs to be installed into the existing mast groove with track. AND NO (dedicated) TRACK-Those systems whose sliders operate in the mast’s groove.

Dedicated track requiring attachment to the spar is a hallmark of a high end ball bearing system

Dedicated track requiring attachment to the spar is a hallmark of a high end ball bearing system

BATTEN BOXES: Those that are adjustable, to tension the batten in the sail and those that merely accept the batten and the batten tension is applied elsewhere, usually from a lashing or Velcro arrangement on the leech.

Batten boxes come in almost as many flavors as the systems themselves. Top two items, L-R: Antal slider with leech load box, Tides Marine slider with their leech loading box.  Bottom three, L-R Sailman box and slider from Bainbridge, Rutgertson box and slider and a Battslide brand box with toggle.

Batten boxes come in almost as many flavors as the systems themselves.
Top two items, L-R: Antal slider with leech load box, Tides Marine slider with their leech loading box.
Bottom three, L-R
Sailman box and slider from Bainbridge. A Rutgertson box and slider
and a Battslide brand box with toggle. This toggle would fit into the Harken batten car, shown above, in the red dummy track and all of the others reference here except Dutchman.  Not shown is another box called PNP, roughly similar to the bottom three.

 

This detail shows a leech loading batten pocket tensioning mechanism. BUT not only should the leech tensioning method tension the batten, it needs to be engineered in a way that makes it really hard to loose the batten out the end, as when flogging the sail in hard wind while reefing or attending to some drama aboard. This is a good reason for the luff loading battens with adjustable boxes. Adjusting the tension on the batten is a lot easier too-You do not need to be scrambling around up on the boom to get to the leech of the sail, rather you can stand at the mast and use typically a hex socket or sometimes a screwdriver.

This detail shows a leech loading batten pocket tensioning mechanism. Not only should the leech tensioning method tension the batten, it needs to be engineered in a way that makes it really hard to loose the batten out the end, as when flogging the sail in hard wind while reefing or attending to some drama aboard. This is a good reason for the luff loading battens with adjustable boxes. Adjusting the tension on the batten is a lot easier too-You do not need to be scrambling around up on the boom to get to the leech of the sail, rather you can stand at the mast and use typically a hex socket or sometimes a screwdriver. In this image you can see a length of light spectra lashing , far right, secured through the batten end and around the webbing strap. The batten is tensioned by a lashing (not installed yet) passing through the webbing and the grommet on the flap, to the left.

TOGGLES: These are usually metal devices that connect the batten box to the luff car. They are superior to merely webbing the batten pocket to the car because they maintain a separate specified rigid distance between the sails edge and the car. For the batten box to slider connection a more or less standard M10 and M12 threads on the studs entering into a matching female on the box. The boxes in the image above the one of the leech loading pocket detail, are all connected to their respective slides by the toggle.

Virtually all toggles are a variation of this version on a Rutgereson roller slide.

Virtually all toggles are a variation of this version on a Rutgereson roller slide. Most batten boxes have a matching M10 or M12 female into which the stud threads. This slider BTW is one of the crossovers in that the ball bearings are in the wheels, which bear on the outside of the mast tunnel-No dedicated track required.

CROSS OVERS: There are at least a couple of products that offer in-mast sliders that require no dedicated track and have ball bearings or some kind of roller on the slider.

This is one of the most elegant cross-overs-The Ronstan Ballslide. They come in two sizes a 6 and an 8

This is one of the most elegant cross-overs-The Ronstan Ballslide. They come in two sizes a 6 and an 8. You can see the “feet” held in place by the screw, on the left of the image and the balls in their cavity. If memory serves the numbers refer to the diameter of the balls.

 

 

Ronstan ball slides on a Sabre 30. Perhaps a tad over kill for some, but the owner wanted to be able to reef the main from the cockpit. He reports being able to exactly that. In order to achieve this for him I had to rework a chunk of the reefing system on the boat. All done remotely-He In Michigan & me in Newport.

Ronstan ball slides on a Sabre 30. Perhaps a tad over kill for some, but the owner wanted to be able to reef the main from the cockpit. In order to do that, incorporating all the inherent friction from such a reefing arrangement he needed a low friction solution at the luff. In order to achieve this for him I had to rework a chunk of the reefing system on the boat. All done remotely-He In Michigan & me in Newport. A particular advantage of the Ballslide system is the ability to simply remove the sail from the mast with out worrying about the carriage carriers. In fairness most of the Ball bearing systems with track now do this too but not having to install a track is something many find attractive.

 

 

This image does not do justice to the Selden system. On the other hand since you need a new spar tube, it is not the most marketable system. The cars operate INSIDE the spar in a cavity extruded into the spar and are introduced through the black fitting seen here.

This image does not do justice to the Selden system. On the other hand since you need a new spar tube, it is not the most marketable system. The cars operate INSIDE the spar in a cavity extruded into the spar and are introduced through the black fitting seen here.

CARS/SLIDES: WITH ball bearings:

HARKEN: It will be no surprise that most people’s first thoughts turn to Harken, at least in the US, when the phrases “boat gear” and “ball bearings” are used in the same sentence. The brothers Harken have cars and sliders, ball bearing and not, plus the required track for every size of boat from small, like a J-32 to 90 feet and/or 140 sq. meters, about 1500 sq. feet.

A very typical combination of Harken ball bearing car with a Battslide box.

A very typical combination of Harken ball bearing car with a Battslide box. The Battslide box shown here has been superseded by a later generation with improvements on how to get the batten in and tensioning details. Battslide boxes are manufactured by Schaefer.

RONSTAN: In some quarters, perhaps expats, like me, familiar with Australian sailing equipment, recognize the Ronstan name too. Like Harken, Ronstan has track and car systems for boats as as small as 40 FEET up to 45 METERS.To be fair to Harken, they too offer custom solutions for boats over 90 feet

This is a one combination of the Ronstan equipment

This is a one combination of the Ronstan equipment. The sticker says Frederickson because that was the name of the company before Ronstan purchased them a few years ago.

FACNOR: Followers of French boats would recognize the Facnor name in reference to headsail roller furling and not associate them with roller bearing mainsail luff track hardware. The Facnor equipment is nicely made and revolves around one track size, with the cars getting progressively bigger for larger sail/boat applications. They offer systems suitable for sails up to 130 square meters.or roughly 1,400 square feet.

Facnor track car toggle/Stud with a Sailman box.

Facnor track car toggle/Stud with a Sailman box. The track size stays the same but the cars get progressively bigger for bigger loads.

 

SELDEN: offers a hybrid in their MDS system. This however requires a new spar tube since the Selden cars run inside a special cavity extruded into the tube, so rather impractical unless you are getting a new mast or boat as in fact this owner was doing-A Saga 43 in this case. Selden also has a track and ball bearing system called RCB in two sizes. Selden calibrates the correct equipment based on the boat’s displacement. This system is interesting because it has a novel way of easily disconnecting the sail from the cars, the latter thus stay on the spar.

These four all use a dedicated track.

TRACK ATTACHMENT: There are four ways to attach the track to the spar. Either fasten the track to the spar with the appropriate sized metal thread fasteners. Use the connection slugs offered by the equipment maker, slide the tack into the mast groove-Tides and Dutchman or glue it on, for Carbon  spar applications

RONSTAN: has a cross over product called a Ballslide that has recirculating ball bearings in the car and a variety of screw-in shapes they call “feet” that will, at least in my experience, fit any mast groove one is likely to find. This is one of the hybrid products.

RUTGERSON: Another hybrid slider with ball bearings, albeit really small ones, is from a long established Swedish sailing hardware firm called Rutgerson. Their products are distributed in the US by Challenge Sail cloth, another supplier of sail making bits and pieces to the trade. The Rutgerson cars/sliders look like a beach or moon buggy and the bearings are in the wheels of the buggy.

DUTCHMAN SYSTEMS: From the folks who brought you The Dutchman flaking system, is their entry in the luff track stakes. The Dutchman has two versions. A dedicated track option and a track-less roller bearing cars option. The later has a similar “Beach Buggy” looking batten slider, see below.

CARS/SLIDES WITHOUT ball bearings:

BAINBRIDGE- ALLSLIP: At the simple end of the spectrum there are “regular” luff slides that can operate in the masts own luff groove and do not need a dedicated track. The most common slides one step up from merely using the slide the sailmaker would use regardless of whether the sail had FLB or not, are called Allslip Slides. They are marketed in the US through Bainbridge, one of the main suppliers to sailmakers of the nuts and bolts of every-day sail making as well sailcloth. Allslip slides are made from a low friction plastic, not nylon as the bulk of the rest of the luff slides are.

A Bainbridge Allslip slide with a stud to a PNP batten box.

A Bainbridge Allslip slide with a stud to a PNP batten box. When using Allslips, there needs a toggle with a slightly different front end, where it connects to the handle on the slider.Regardless of the connection to the slider the box connection will use an M10 or M12 thread.

Bainbridge also offers their own integrated FB line they call Sailman. Sailman consists of a range of slides, toggles and boxes for three varying sizes of boat or sail area.  The toggles they use in the Sailman can also be used with the Allslip slides. This feature works particularly well with Selden spars whose luff groove profiles are unique to their mast sections.

TIDES TRACK: A company based in Florida called Tides Marine, that is in the slippery plastic business, offers a high value product.  This is an extruded low friction plastic that comes rolled up in a spool, like a garden hose thus minimizing shipping costs. The requisite number and type of slides go to the sail maker. The track mates to your existing mast track, particulars of which are determined by a set of templates they send you or their dealers have. Propriety stainless steel slides that work only in their track (and others slides do not…) are available in three sizes of height: Intermediate, batten or reef slides and head slides. They are roughly 1”, 2” and 3” tall respectively.  Tides offer their own batten “boxes” aka receptacles but these are leech loading only.

DUTCHMAN SYSTEMS: The ever enterprising Martin Van Breems is also in this arena with two products. One is similar to the Ronstan Ball slide and the other is a track system product similar to Tides System using a low friction plastic proprietary extruded track and dedicated sliders. The Ball slide version incorporates small SS balls in wheels that run on the outside of the spar’s groove to accept the compression from the FLB and look largely like the Rutgerson moon buggy design.

The main difference between the Dutchman dedicated track version and Tides product is the Tides slides run INSIDE their track and the Dutchman system runs on the OUTSIDE of their track. The second important difference is the Dutchman track system hardware is unique to Dutchman.Thus no other cars or sliders will fit on the track and they do not have the ability to use third party toggles or batten boxes.

ANTAL: is a prominent Italian manufacturer of all sorts of sailboat hardware hardware. They have a dedicated track with slider system. These sliders have a low friction fiber composite insert. Antal also has roller bearing cars at the upper end of their range. They too come in a variety of sizes suitable for smaller boats up to 100 feet. They offer their own propriety batten boxes. Their batten sliders come with the virtual industry standard 10 mm and 12 mm threaded studs.

SCHAEFER MARINE: also has an offering in this non-ball bearing field. They have a selection of “normal” sliders, toggle connectors and the very widely used original Battslide batten boxes. They also have a dedicated track one can install but I have never seen the advantage of this unless the spars extruded track is damaged in some way. They offer a wide cross section of sliders to fit probably all mast sections built in the US in the past 50 years, With and with out “rigid” toggles, but attached by shackles to the slider. Thus their products is frequently seen on smaller boats where the proportional cost of Full Length battens and related hardware is a bigger percentage than on a larger boat.

 

Next up: The Battens followed by “all the things you didn”t know, you didn’t know…

 

 

 

 

Full Length Battens-3: Square Head mainsails

 

The Square Head Mainsail–on to advantage side of the equation:

The Square Head mainsail is the default style for the Class 40 short handed offshore race boats.

The Square Head mainsail is the default style for the Class 40 short handed offshore race boats. Don Miller Photography image

The previous few essays have focused on the limiting issues surrounding full length battens including, for the vast majority of the normal boats that most of us sail, the backstay.

Briefly I have proposed that:

  • There is not really solid empirical evidence that one sail with FLB is faster than the SAME sail with leech battens on the same class of boat and assuming that both boats are prepared to be as identical as possible.
  • The Cost of FLB may outweigh the Value a lot of the time
  • I will get to the “sail handling” aspect of FLB further along in the series. This area is in fact one of the areas that does offer increased value for the owner via ease of handling the sail: Hoisting lowering reefing.

For now I am going to concentrate on the most obvious advantage and a much lesser known aspect of full battens in general and the Square Top mainsail in particular.

In my experience virtually all discussions with sailors regarding sail shape is one sided, in that it revolves around the sail’s shape and so the implied concept is aerodynamic lift. I cannot immediately recall any discussion where the other side of the lift equation is even mentioned let alone discussed: DRAG.

Drag is everywhere on a sail boat:

Someone with more time on their hands than me could calculate the amount of drag on this boat

Someone with more time on their hands than me could calculate the amount of drag on this boat

The actual hull topsides

Cabin profile

Rigging

The sail’s surface

The width of the roller furler or furled headsail when sailing with a staysail

The furling drum

The anchor

Rails, life lines stanchions

The dinghy stowed on the bow or in Davits

Cruising boats carry lots of kit and it is all drag.

Cruising boats carry lots of kit and it is all drag.

Halyards

Dodger

Life raft on the cabin top

Bimini

People standing up- This is why most good race boats have the guys all sitting together in breeze or laying low in light air.

Radar either tower astern or on mast

Radar reflectors…..You get the picture.

What is missing from this list?

It is one of the reasons why the square head sail has emerged over the past few years.

We have discussed the usual limiting factor for the size of the roach on most boats is the backstay, closely followed by adherence to a handicap racing rule.

Enter the “open” class boats, in particular the solo offshore race boats. This cohort encompasses the Mini 650 class, the older open 40’s and the much more successful, as a class, Class 40’s, the open 50 and 60 foot mono-hulls and their multi-hulled cousins and in some parts of the world open class skiffs like the Aussie 18 footers.

None of these classes (I am not 100% certain about the 18’s) have any restrictions of sail size or shape, only number and type depending on the individual class and the race.

If Bigger (more area) is Better, so the square top sail is born.

The one element missing in this discussion so far is the mast.

The mast, the square top sail and full length battens are all interconnected.

 The Twitter version:

The mast is drag

The square top sail minimizes that drag

The ST cannot work without full length battens

ESPECIALLY in this case, the FLB need a low friction track because of the great compression generated by the ST sail.

The NPR version:

Because it is sticking up in the air, the mast is 100% drag, at least for the purposes of this essay-Ignore the wing masts and wing sails please.

Over the span (the fore and aft width of the sail-the girth.) the drag from the mast is reduced because the air is smoothed out by flowing across the sail.

As the sail ascends into the air on 99% of boats it gets narrower, again almost universally due to tradition as manifest in the backstay.

This image gives a good visual of the issue at hand-Namely the top 3-4 feet of mainisail-on a 40 footer-is not contributing to reducing the drag from the mast.

This image gives a good visual of the issue at hand-Namely the top 3-4 feet of mainsail-on a 40 footer-is not contributing to reducing the drag from the mast.

At a point that varies for all sorts of reasons this reduction in drag is reduced. The drag from the mast starts to increase.

The point is that usually within a few feet of the top of the spar and for a rule of thumb it can be where the girth of the sail is less than about 4 or 5 times the local for and aft length of the mast, the amount of drag over comes the amount of lift generated by the sail.

For instance, let’s say the mast is 6 inches fore and aft. 4 or 5 times 6 inches is 24-30 inches. So in this example the drag starts to increase, dramatically, at that point on the sail where the girth is less than 24-30 inches wide fore and aft because there is not enough girth in the sail to smooth out the turbulence created by the wind hitting the mast.

This image shows the ration of the mast for and aft length to the width (girth) of the sail as the sail approaches the mast head. 4 or 5 to 1 puts the equal girth n this main at a little lower than half the distance between the mail head and the top batten. I enlarged the image and used a metric rule against the screen to determine this.

This beam on image shows the ratio of the mast’s fore and aft length to the width (girth) of the sail. This is obviously a conventional mainsail and was built to comply with local racing handicaps. As on almost all conventional yachts, as the sail approaches the mast head the position of the girth on the sail diminishes. On this Sabre’s main the girth equal to 4-5 times the masts span is a little lower than half the distance between the mainsail head and the top batten. Functionally then the (mast) drag starts to increase dramatically somewhere above the top batten is. I enlarged the image and used a metric rule against the screen to determine this.

Enter the Square Head sail. This sail profile minimizes the drag from the spar as well as being much more sail area.

I do not have many images close up of the relationship between the mast width and the sail girth as for the one of the Sabre above, but I think you get the idea.

I do not have many close up images of the relationship between the mast width and the sail girth as for the one of the Sabre above this image, but I think you get the idea. This image courtesy of Don Miller.

BUT

It is functionally impractical for any boat with a backstay. Unless of course you want to lower the mainsail every time you tack which may sound like a pain but again find out what the customer is trying to do with his boat sail goals plans etc. I did do two offshore cruising boat sails that were exactly that big roach that would not clear the standing backstay. In one case, the image below, it was a bit difficult to get through in light air although he reefed in about 14 knots of wind, so the roach was easier to deal with the first reef in. I did another offshore cruising mainsail where the owner specified that he would sail with the first reef in if lots of tacking was going to be involved. The roach in this sail was even more aggressive than the first one.

This is the roach profile of the first boat I mentioned in the paragraph aobove.

This is the roach profile of the first boat I mentioned in the paragraph above. Many thanks to the owner for providing the image. www.mccubbin.ca/boat

 

This particular boat was built with two configurations-One with this large roach and NO backstay at all for coastal cruising in and around New England. The spar was of course so designed. And a smaller main WITH backstay for going in the ocean. This is one way to do it...

This particular boat that I did the working sails for was built with two configurations-One with this large roach and NO backstay at all for coastal cruising in and around New England. The two light lines you see on the sail are more conventional runners for headstay tension, but are not really required to keep the rig in the boat. The spar was of course so designed. And a smaller main WITH backstay for going in the ocean. This is one way to do it. Boat was a custom Bruce King design.

For boats with such sails, very large roach OR square head, enter the twin topmast running backstays, generally referred to as “the runners”.

As the name implies, they are running backstays that attach to the masthead and are adjusted by a two or three part purchase led to a winch.

This image gives a bit of an idea on the twin running backstays idea. Yes, this is a race boat, a single handed forty footer from the 2009 O.S.T.A.R

This image gives a bit of an idea on the twin running backstays idea. Yes, this is a race boat, a single handed forty footer from the 2009 O.S.T.A.R. The two padeyes with blocks on the transom are part of the three part purchase this boat has. The blue cordage crossing forward of the starboard stern rail is the last fall prior going to the winch through a clutch at the very edge of the image. The pair of blocks adjacent to the base of radar plinth are for the mainsheet.

Upon contemplation it will be seen that this is not something to be undertaken lightly. Many things need to be contemplated, not the least of which, in no particular order are:

Boat & Deck hardware lay out

Mast strength

Standing rigging configuration

The degree of sweep of the spreaders

The skill of the operators and

Their willingness to put up with this added task when tacking

All these factors contribute to the reason why most “cruising” boats do not have square head sails.

Next up running backstays, batten compression and hardware for the battens.

Our first sail late in the afternoon. Scott Bradford assisting and checking the spar.

This is my mini-650 on her first sail late in the afternoon in August 1995. Scott Bradford assisting and checking the spar. This was the first 5 minutes of sailing after her launch. At the time this roach profile was considered to be huge. If you look at the luff you will see the luff sliders I used-NOT ball-bearing at all, but the best available option on the day. I was more interested in keeping the sail on the boat during handling.