Category Archives: SAILS

All things to do with sails: Their use, material, quantity of, measuring for manufacturing, setting and related.

Mast rake Versus Mast bend

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Mast RAKE and mast BEND are two aspects of a boat’s sail plan and rigging used in making small adjustments to the mast, thus the performance, on a sailing boat. The two adjustments are quite different. These two words and attendent adjustments are frequently confused among weekend sailors. I will try to separate the two in this post.

Mast RAKE refers to the distance aft of perpendicular (to the waterline-Horizontal) the top of the mast is. It is used to fine-tune the boats balance and is generally not changed very often on cruising boats and perhaps never.

Mast BEND refers to applying tension to the backstay so that the mast bends to some degree. The amount of bend varies with the boat. BEND can be adjusted on the boat while sailing to change the sail shape and is adjusted depending on the wind speed.

I will address mast rake first.

MAST RAKE:

Some background:

Sail boat designers need to make sure the boat will ‘balance’ when sailing. This means in practice that there will be the ‘right’ amount of pressure, or ‘helm’, on the tiller or wheel when sailing up wind in about 10-15 knots of true wind. This balance is created by the relative positions of two features of the boat’s design. The sail plan’s Center of Effort (CE) and the boat’s (the hull, keel and rudder) Center of Lateral Resistance (CLR). The center of effort of the sail plan is quite easy to determine.

In the picture below you will see three short pencil lines at the pointy end of the crayon. This is the position of the sails C of E that I drew for this exercise. If you look carefully you will see the Designers hand written note indicating HIS C of E on the sail plan, (and a note on the sail’s size in square feet) immediately under where I found the C of E.

the intersections of the pencil lines is the Center of Effort of this sail

The intersections of the pencil lines is the Center of Effort of this sail

The designer calculates the C of E by drawing three lines on the sail plan. They are drawn from the center of one edge of the triangle (the sail) to the opposite angle as seen in the image below.

Big picture of the the center of effort

Big picture of the the center of effort

Lines are struck from the mid-point of the boom to the head, from the mid-point of the mast to clew and the mid-point of the leech to the tack. Where the lines intersect is the C of E. This point is an integral part of the sail and ‘moves’ with the sail. So if for instance the fore stay is lengthened, the mast HEAD moves aft (increasing the rake) the C of E moves aft (creating more weather helm). The reverse reduces weather helm and if excessive, creates neutral or sometimes lee helm.

Mid point of boom.

Mid point of boom.

The C of E is found by striking a line from each sides of the triangle to the opposite corner. Above is the mid-point of the boom, to the head of the sail.

A line from the mid point of the mast to the clew

A line from the mid point of the mast to the clew

The picture above shows a line from the mast mid-point to the clew.

This line is from the leech mid point to the tack

And this line is from the leech mid-point to the tack

Sailmakers need to know the mast rake for a few reasons all to do with making sure the sail(s) fit the boat.

RAKE is determined in most boats, not dinghies (they use another way) by measuring the distance the masthead is AFT of vertical, that is perpendicular to the waterline. It is measured at the boom and described as “xx inches of rake”, at least among Sailmakers & Riggers. Generally it looks like this:

Mast rake measurement on a J-105 rig.

Mast rake measurement on a J-105 rig.

The ruler shown above is set perpendicular to the water line, (on the dwg,) and just touching the back of the mast at the masthead (see picture of mast head below). Sailmakers do this, on a sail plan by using the right angle triangle on the right and laying the ruler alongside the triangle so it touches the mast head while perpendicular to the LWL. You can see here the rake on the J-105 on the sail plan is considerable.

Mast rake view at the top of the rig

Mast rake view at the top of the rig

To measure the rake on the boat you basically set up a plum bob, so you will need the following. The main halyard; a weight—a one gallon jug of water, fuel or rum, or the canvas tool bag is fine and a measuring tool: a 6-foot Stanley tape is fine. Ideally this measurement is done on a windless or light air day where the boat is not bouncing around. It should take 5 minutes or less. It is dead easy to do alone but a mate is always good to have.

Attach the weight to the main halyard and hoist the halyard only a couple of feet so the weight is half way between the bottom of the boom and the cabin top. Let the halyard/weight come to rest. Where the halyard crosses the boom, measure forward to the aft face of the mast and note the distance. This is the rake:-“xx inches”. So in the picture below, the amount of rake is that distance between the forward side of the ruler and the  aft side of the mast,

VIew of the plum bob/main halyard across the boom

View of the plum bob/main halyard across the boom

I used a J-105 as an example here because they have a lot of rake so it is clear in these pictures. Most ‘cruising’ boat’s do not have this much rake.

On the other side of the coin, If there is almost no rake, less than say 2 inches on a 35-foot boat, this bears looking into. If there is a lot, more than say 12-15 inches on the same boat, again this bears research. In the former, you may relate this to the light feel in the helm. In the latter, it will be a large factor in the boat’s weather helm.

Sailmakers need to know how much rake is on a boat when designing sails for several reasons. On a practical note, three key ones are: so the boom does not hit the dodger or bimini or on some boats the mast gallows. How much rake a boat has is also an indicator as to how the boat is set up; rigged or tuned up if you like. To use the J-105 example, if I were sent a measurement sheet that showed 3 inches of rake on a J-105 that would set of alarm bells because it is way off base.

Rake information is needed for designing headsails too. The C of E of headsails is determined the same way as for a mainsail. Thus the amount of rake has an impact on where the clew is going to land. If one was to merely duplicate the three edge dimensions for one boat of a particular class onto a sistership, without checking the sistership’s rake, AND the sistership had a lot of rake, then the clew would be a lot lower and perhaps the sail would not be able to be sheeted to the installed genoa track. The reverse is true if there is a lot less rake, the genoa may want to sheet where there is no track–Seen that happen too.

These two scenarios are less of a problem on cruising boats but a detail that consumes a lot of checking-time on race boats where the track locations are very specific and the tracks are usually pretty short, to save weight of course.

Next up Mast Bend

 

Newport to Bermuda Race 2016: Part one

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An inside staysail suitable for setting of small sails is a requirement of the Newport to Bermuda race. Any offshore race actually

An inside staysail suitable for setting of small sails is a requirement of the Newport to Bermuda race. Any offshore race actually

Yeah yeah, I know, some of the boats are not even back home after the 2014 event but, it is never too early to start planning.

And anyway, last week I received an email from a fellow who wanted counsel on putting together a campaign for the 2016 Newport Bermuda race. We met for a burger and beer and had a great time going over the various elements comprising a successful campaign. IT should be noted that at the moment he does not have a boat suitable for this race. After writing the Spindrift post yesterday, I thought it might be interesting to compare my notes from this meeting with what the Spindrift guys might be thinking about.

For this fellow I came up with, in no particular, just as I thought of them:

A boat suitable for the raced AND ones which the Race committee will permit to enter.

While not used in "normal" yacht races, the physical testing of a boats stability is normal in the open classes, as evidenced here by the pull down test for a 6.5 meter Mini-Transat boat. FOr the Newport to Bermuda race, the Organizing Authority refers to a boats rating certificates and imposes regulations on stability from that data.

While not used in “normal” yacht races, the physical testing of a boats stability is normal in the open classes, as evidenced here by the pull down test for a 6.5 meter Mini-Transat boat. For the Newport to Bermuda race, the Organizing Authority refers to a boats rating certificates and imposes regulations on stability from that data.

The Racing rules of Sailing AND the particular rules of the Newport to Bermuda race.

Preparation of the boat, going over all the systems, upgrading or paring them as necessary
Management of the whole project INCLUDING returning from Bermuda…
Delegation of tasks and areas of responsibility—Sailboat racing is a management exercise as much as a sail boat race.
Strategies for developing the boat, the systems and the crew—Proposed crew is light on for offshore experience into an integrated team. Coaching practice theory and other class room work as it were.
Safety at Sea education—both formal, the usual weekend seminars in the Spring and more intuitive, experiential sort
Weather, (including Gulf Stream) learning about and then decision making during the race.

The ability to capture weather information and the skill to interoperate it is a key element in any ocean race these days with the latter being the more difficult.

The ability to capture weather information and the skill to interoperate it is a key element in any ocean race these days with the latter being the more difficult.

Rigging and sails AND related components of crew co-ordination for setting, changing, lowering sails and the techniques, where each person is for what maneuver
Food—What, how prepared, what kind, where stowed, how served and what to eat when the wx. goes to pieces.

Cooking facilities are mandatory

The care and feeding of the boat’s most important resource and asset is essential

Health of the crew. Overall physical ability to cope with 3-6 days at sea. Meds, issues like Diabetes, seasickness for just couple of issues
And related Medical expertise, what to do when something happens to one of the crew
Logistics, paperwork—passports, race entry paperwork etc.: Back office stuff.
Electronics, related to performance and to Navigation.
Navigation and related disciplines of the position of the boat relative to the Gulf Stream, the expected weather and the competition.
The foregoing is a reasonable overview of what needs to be managed for a 40 foot mono-hull, sailed by Corinthian sailors in a 600-mile race 2 years from now.
In the next few posts I will break down these by number and elaborate a little on just what is needed.

 

Code Zero Spinnakers

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Some thoughts on sail design:

With particular attention “pointing” ability

Especially with respect to Code Zero sails

This essay is in direct response to a statement from another sailmaker to a customer that “a laminated material will point higher” compared to the heavy nylon I was proposing.This is an altogether a too broad a statement.

The type of fabric from which a sail is made is not at the top of the list when contemplating sail shape. Certainly building say a heavy jib of too light a material is not going to be effective but bear in mild also shape is only one aspect of a sail. Apart from “the shape” sails need to consider the following criteria, in no particular order.

Cost, durability, ease of handling, response to hard handling (aka tear strength) range of utility, (wind speed and angle), stowage issues are some of theses criteria.

A code zero is a unique sail in that in most cases it needs to rate like a spinnaker but to work like a genoa. That is it is intended to be used in light air when the boat wants to go up wind and for want ever reason, the “normal headsails” on the boat are not as effective as a “code zero” thus the response about pointing. Years ago such sails might have been referred to as cheater sails

The original code zeros were invented over 20 years ago for the Volvo Ocean Race. Due to the sail limitation rules and the lack of a normal overlapping genoas, Paul Cayard’s team fell upon the idea of having a sail that was designated a “spinnaker” but used as a headsail. They beefed up the boat to take the high loads generated by the tight luff that this sail needed. Fast forward to about 10-15 years ago and similar sails started making their appearances on the domestic recreational race course. Since they had to measure as a spinnaker, which is a girth* issue, all the girth was in the leech, rather like the roach on a mainsail. The other issue with such sails on furlers is the tremendous loads required to set up the luff of the sail so the sail would actually roll around the luff. The boats or the masts that Corinthian sailors sail were just not built for such loads.

About 8 years ago, Hood developed a version of this cheater headsail that was able to set and handled like a normal spinnaker, and was measured as one. This sail did not need a furler, tight luff rope and related costs, was made from Nylon yet could sail as close as 40 degrees apparent.

These sails fit the use profile of the non-professional sailor: They were inexpensive-nylon is cheaper than laminated materials, especially the more recent ones designated code zero materials, they were easy to handle-Just like a normal kite, took up a pretty small space, and considering the infrequence with which they are used this is appreciated by weekend racers. And a particularly appreciated aspect of nylon sails is their relative tear resistance compared to the very light film sails from which code zeros are built. Also nylon is much more resistance to damage from flex, read flogging than Mylar film, a detail if you are to be caught out in a squall somewhere.

With respect to the statement above, a review of design issues is in order.

The pointing ability of a sail is a function of at least two details: the draft of the sail and the entry angle. The draft is of course the fullness of the sail, technically the chord depth. And this depth changes vertically up the sail too. Consider for a moment a conventional spinnaker. If it is full, you can only head up so much in any kind of luffing match with it in pole-on-the-head-stay conditions, close reaching. This is why boats have a flatter reaching spinnaker. Same idea applies to the zero it is flatter again than a regular spinnaker, but fuller than a headsail.

The entry angle is a bit less obvious. This is the angle between the chord line and the angle of the very front couple of inches of the luff of the sail. A narrower angle here means the boat can point higher BUT it also requires that the boat be more accurately steered in order to keep in the groove. If the boat falls out of the groove as when a wave passes, the boat will slow down & the trim needs to be adjusted and the boat brought up to speed again. It is not uncommon for one-design boats to have different shaped headsails for use in flat, moderate of choppy waters. The choppier the waters the wider the angle of attack needs to be so the boat can be steered around waves with out stalling. Stalling is the “falling out of the groove” feeling.

With a sail like a code zero, intended to be used by most production cruiser racers generally in under ten knots true, a wider angle of attack is to be preferred. This is to accommodate the wide variety of conditions that such boats generally sail in.

The loads on a sail diminish dramatically as soon as the sheets are started even a small amount. For instance the load between a spinnaker trimmed hard enough to develop a crease between the tack and clew, as when trying to keep it full in really light air, diminishes quickly when the sail is eased to where the crease vanishes. That is why you may need someone to crank the sail to get it to that stage, but ease it a foot or so and the trimmer can trim by hand.

Going back to the sentence above about building a heavy weather jib from light fabrics, one enters the realm of properties of the fabrics in question: Nylon and code zero fabrics. The latter are a sandwich similar to composite boat building in that there are several layers and glue.

By far and away the vast majority by area of a code zero fabric is Mylar film. Bear in mind that the fabric has two sides, so the Mylar film is 50% of the total fabric in area. This film is half a mil thick. For comparison, a normal laminated sail might be .75 of a mil Mylar for a light air headsail for a 35 foot boat up to say 2 mil Mylar in sails on a bigger boat. It is pretty rare to get thicker film than that because such fabric becomes a real bear to handle.

Next in area is the other 50% of the sail fabric which is very thin deniers (small, tiny in fact yarns) woven polyester that is not shrunk. This is glued onto one side of the fabric.

Finally we get to the strong fibers. These fibers, called tows are glued in between the film and the taffeta. They are described by their denier. This is how thick they are, roughly like half inch line is thicker than quarter inch but thinker than five eighth. 50 denier is what light nylon sails are woven from, 1100 is a thick denier. Most fabrics operate in the 300-900 denier, as a broad statement. Reading the data from one of the major cloth suppliers in the US, their second to lightest material is made as follow:

Half a mil of film:

A tow (cloth speak for a “bundle” of fibers-Visually a tow will look like a thick piece of string) of 1140 denier aramid fiber, gold in color, set on half inch centers on the zero axis. The zero axis is parallel with the length of the roll.

There is a flat X shaped 750 denier tow of an aramid called Technora, this is black

There is a taffeta on the other side of the film.

There is a glue line holding the lot together.

To review

This material is 2.1 oz

This code zero fabric is close to two times the cost per yard than 1.5 oz Nylon.

It is about 30% more expensive per yard than grand prix nylon.

It is about half as stretchy on the zero axis as a comparable nylon

The film on this fabric is only half a mil-Not a strength consideration but a handling and durability question:

Durability is a factor in the sense of dragging the sail over life lines, across stuff on the deck, by the rigging turn buckles with cotter pins just starting to poke thru the electric tape, meat hooks on the halyards of the mast, and around down below. And as noted if caught out in building breeze and it spends time flogging, this (flexing) will degrade the film more than any overloading will do. At any rate most sailmakers to day will make the clew so the ring fails before the sails blows up.

This video is of a Hood Code Zero on a J-105. I was sailing this boat from Newport to Fishers Island alone. In this circumstance we are actually beam reaching, not going to go up wind. I have used this same sail in 25-30 knots true sailing at 90 apparent double handed from Block Island to Greenport in a race. We won because we had a sail we co old set that was right for the conditions.

 

 

 

Solent stays and storm jibs

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A Solent stay is an excellent way to get a heavy weather Jib or a Storm Jib rigged on your boat. This post will discuss another layer of rigging issues as posed by a fellow from the LinkedIn group. The personal names refer to the people in the discussion topic on LinkedIn.

A Solent stay is a great way to get a smaller sail set when it is too windy for the Jib on the furler

A Solent stay is a great way to get a smaller sail set when it is too windy for the Jib on the furler.

Several issues will be discussed here:

  1. Spar and deck integrity
  2. Aspect ratio of the headsails
  3. Running backstays

Implicit in this essay and the above issues is the  design of the boat and in particular the size of the fore-triangle, in absolute terms and relative to the overall length of the boat.

I am answering a question from a LinkedIn group discussion here since my response on the group was way to long for the comments section and I cannot post images. So this post will read a bit more like a monologue that the usual Blog Post Essay style.

The answers I wanted to post on LinkedIn begin here:

Gentlemen,

To continue on the subject of how to set what kind of small sails for when it is blowing too hard for the bigger ones.

Some points for discussion:

  • Pad eyes ripping out
  • Inner staysail stay (& Runners?)
  • Aspect ratio, again
  • One alternative

 Pad eyes ripping out

Graham is correct. You must make certain beyond any doubt that the structure at the deck termination of the stay is absolutely capable of taking the load. Not merely the load of the stay tension but the dynamic load of the boat bashing off waves etc.  (Please review the images below taken from a Quest 30 set up for single and double-handed sailing in the ocean) Simply because there is a “bulkhead” there, does not mean for a moment it is a true structural member capable of withstanding the loads imparted when sailing in 30 plus knots. Far more often it is merely masking the forward part of the forward cabin from the anchor rode etc. so merely glued in to make the interior look nice. I had this exact situation on a delivery with a Santa Cruz 52 one time. We pulled the padeye out of the deck along with a bit of deck while sailing with the SSL in only about 30 knots and modest seas. Upon subsequent inspection we discovered that the forward “bulk head” was just what I described above, a way to make the forward cabin look nice. Virtually no structural content, yet someone had landed the staysail fittings there….

This image is inside the anchor well on the boat

This image is inside the anchor well on the Quest 30. As you will see the furler is under the deck in the anchor well.We took the primary pin securing the headstay to the boat and attached the eye that is seen here. The piece of string is part of the method we used to align the hole in the deck so the strop would be as straight and parallel with the stay as we could manage.

This issue of local structural strength is one of the reasons I often advocate for the stay to be at the bow because in variably the forward part of the boat, where the head stay lands is strong both in terms of layers of materials but the angular nature of the bow, provides lots of strength through the structural geometry.

We spent a lot of time measuring angles to get the position of the hole in the deck right.

We spent a lot of time measuring angles to get the position of the hole in the deck right.

The staysail passes thru the deck (and into the anchor well) just aft of the headsail furler

The staysail stay passes through the deck (and into the anchor well) just aft of the headsail furler. You can see we lined the hole we made in the deck with a plastic through hull and used a textile strop connected to the eye seen in the picture above.

 

This  is what the strop looks like attached to the adjustment tackle on deck:

Here you can see the strop passing through the deck to the eye on the primary headstay pin seen in the images above

Here you can see the strop passing through the deck to the eye on the primary headstay pin seen in the images above We got the alignment of the whole arrangement pretty good. The strop is only just bearing on the aft edge of the hole.

 

Inner Stay and Runners:

This image os of the Inside stay arrangement on a 30 footer. It is NOT a Solent as in a sail that is arael to and just aft of the headstay. Rather it is in snside staysail, staysail storm staysail, choose your name.

This image is of the inside stay arrangement on the  Quest 30. It is NOT a Solent as in a sail that is parallel to and just aft of the headstay. Rather it is an inside staysail stay, a staysail stay, a storm staysail stay, choose your name. The idea is that it provides for a smaller sail for use when the one on the furler is too much.

 

In the images above, the salient points are:

  • Smaller sail set on hanks when the furling headsail is too much
  • The hardware for this sail was already on the mast
  • Using the pad eye on the deck, seen above just aft of the stbd. stanchion made the aspect ratio AND the size of the sail too great and small respectively. (Refer to the Power Point link further on in this post)This is relative because you do not want too much of a jump in sail area between sails other wise there is a gap in the “gear box” as I refer to it as.
  • It later transpired that we discovered the pad eye was intended for a spinnaker staysail which of course see a lot less load.

Timo: I do not know so far if: a) your boat already has an inside stay-a stay originating from a point on the spar about the location of the spreaders, and b) if so is it already set up with a stay, a halyard and so on?

If so, then I again advocate for the base of the stay and so the sails tack fitting to be as forward as possible.(as in the image above) For the reasons previously outlined. BUT be very careful with the mast.  If there is for instance a Spinnaker pole topping lift sheave and line at about the right place. Almost for sure the sheave and related structure for a spinnaker pole topping lift is inadequate to carry the loads of a heavy weather stay.

Staysail stay attachment point on the spar and runner take offs.

Staysail stay attachment point on the spar and runner take offs. The necessary components for the staysail to be attached to the spar  are seen here. Stay attachment-Via a T fitting into the spar, the halyard sheave box and halyard, and attachment points for the runners. Note too that the spar has been reinforced in the way of all this

 

If not, then the issues surrounding installing such rigging are roughly the same as for a Solent stay set up except that you will need to add running backstays too. This may be complicated by the location of the spreaders so you may want to move the ideal location for the stay and halyard away from the spreaders area-Too many holes for one thing.

Aspect ratio:

I had previously mentioned that the Aspect Ration of the Avance 36 fore triangle is over 3:1. I have done some rudimentary calculations and your Self Taking jib is even higher. This is because the 3:1 number originated with the boat’s specified “I” and “J” dimensions. The actual sail dimensions are shorter on the luff and much shorter on the foot. The latter because if the sail sheets to a track, self tacking track, then the clew will be further forward than if the sail sheeted to a track on the deck like “ normal”. I have an old essay on this issue I will post as soon as I can find it.

This link, below is to a 4 slide power point presentation on this Aspect Ratio Question in particular as it applied to the Quest 30. It was prepared by Mark Washeim at Doyle Sails Long Is. (New York) who worked with us on this sail/rigging/seaworthiness discussion

millard hvy staysail 042413

One alternative:

Depending on a few variables like: how confident are you, with whom do you sail, where, how athletic are you and a few more, a way to address your original question: “What to do when it blows harder than the roller furling jib is suitable for?”One answer is to convert the boat back to hanks…..What you say? Give up my roller furling?

Well sailing as you know is a trade of. You know what the trade offs are with the furler. Some of the nice aspects of a sail with hanks are:

  • Nicer sail shape, the Jib can have battens and look like a real Jib.
  • When not sailing close hauled but say close reaching-say 40-80 degrees apparent wind angle, it is possible to rig up a rail lead and so help the sails shaping.
  • With a hank on Jib, it can have a reef like a mainsail-the mechanics are the same as for a reef in the mainsail and any sailmaker worthy of the name can do it.
  • The sail can be a bit bigger, because there are not deductions for the furler and the clew can be further aft, depending on the location of the headsail track.
  • When you need/want to sail in harder wind, you can have the sail that is designed for the conditions, small flat strong etc.
  • Less windage if you have to anchor in hard wind.
  • Less or not chance really of the sail coming partially unfurled in string wind while you are at work. (Something I have seen too)
  • Hanks are way more reliable that ANY Furler (or its furling line…)

 Some points AGAINST reverting to a hank on headsail.

  • What do I do in winds under say 10 knots?”
  • I have to go to the bow to change sails in wind and waves
  • Where do I put the sails?
  • I have to put it on and take it off every time I want to go sailing-I cannot just unroll it.

 Some THOUGHTS on the against list:

  • Under to knots you can use a light air headsail made from heavy nylon and with a strong textile rope in the luff and no hanks. This sail is not very common these days but I would use them a couple of times a year for different customers when I was at Hood (15 years) to answer this very question for all the same reasons we are having this discussion.
  • This sail is easy to handle because:
  • Is Nylon so can be “handled” like a spinnaker-Stuffed into a bag, sat on, kids (or adults…)can sleep on it, it can be stuffed into a small space, it need not be treated with the care of a Dacron sail-I.E. always folded up and so on. It is inexpensive both in capital cost AND compared to the VALUE of it. It can be used as a reaching sail in more wind at wider apparent wind angles.
  • It is light,  so fills in very light air.
  • The next sail-the Jib-Can be already hanked on. This Nylon sail, being set free-flying, can readily be dropped and pushed down the fore hatch and the jib hoisted in less than one minute most of the time.
  • You may be able to sell your furler and so recoup some of the costs…

All of this assumes that you have a larger headsail now for very light air. I do not know either way….. If the only sail you have is the sail on the self-tacker then I submit to you that this hank on jib offer a lot of benefits.

Finally while looking on the web for pictures of an Avance 36, I saw a 33 for sale and it is rigged with only a self tacking Jib and hanks….. And the pictures of it on the mooring showed the sail hanked on and stowed in a cover like the mainsail.

 

 

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

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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.