Hello, I have a Catalina 38, which I plan to cruise in the next few years to Mexico. I am thinking about a larger mainsail, something along the lines that the Dashew's use on the Deerfoots. By that I mean a large roach main that can be dropped in a small reef to clear the backstay when going to weather. I would apprecaite your input on this idea, in addition what sail cloth to use, weight, etc. I have spoken to Cat38 owners who have installed longer booms to obtain more drive out of their mains, and have not experienced any adverse changes in helm. I'm wondering if the added footage aloft will impact the existing rig and induce weather helm. Thank you, Keith
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Did similar
Keith, I have a Valiant 32 with a very short boom and a tendency to have bad weather helm. We just had a new mainsail built that added 18" to the leach at max point and overlaps the backstay by 3". We just did a 1000 mile trip from La Paz to San Diego with it and it is perfect. At 3" it doesn't hang up on the backstay at all, but we've added 20% more mainsail area. The helm still balances fine primarily I think because the new sail is flatter than the stretched out 23 year old sail. I considered really maxing out the roach, but realized first of all a 20% increase was probably enough and second having to drop the main would be a pain. I'm not sure how much overlap you can get without it self tacking, but I suspect it is 12" or less. I know of a Creekmore 45 with 12" of overlap and he is able to tack fine, but that is a bigger boat with a bigger sail and more force to blow it through.
Keith, I have a Valiant 32 with a very short boom and a tendency to have bad weather helm. We just had a new mainsail built that added 18" to the leach at max point and overlaps the backstay by 3". We just did a 1000 mile trip from La Paz to San Diego with it and it is perfect. At 3" it doesn't hang up on the backstay at all, but we've added 20% more mainsail area. The helm still balances fine primarily I think because the new sail is flatter than the stretched out 23 year old sail. I considered really maxing out the roach, but realized first of all a 20% increase was probably enough and second having to drop the main would be a pain. I'm not sure how much overlap you can get without it self tacking, but I suspect it is 12" or less. I know of a Creekmore 45 with 12" of overlap and he is able to tack fine, but that is a bigger boat with a bigger sail and more force to blow it through.
Me Too....
..as Justin, I had an O'Day 27 that was a bit under canvassed and we did a larger main about a foot longer on the boom (which was already extra long because of aft sheeting). The roach was carried out and it had a full upper batten. It overlapped a few inches, but the only time it was a problem was when dead into the wind to drop it, and then rarely. BIG difference in performance, tho as Justin notes, the old sail wasn't producing good shape. RD
..as Justin, I had an O'Day 27 that was a bit under canvassed and we did a larger main about a foot longer on the boom (which was already extra long because of aft sheeting). The roach was carried out and it had a full upper batten. It overlapped a few inches, but the only time it was a problem was when dead into the wind to drop it, and then rarely. BIG difference in performance, tho as Justin notes, the old sail wasn't producing good shape. RD
Backstay Idea
On our 35 the backstay is a single line down to within say 10 or 15 feet of the stern where it splits. Now here's an idea. If your Catalina was similar, what one could do is install two backstays lines, one each from the masthead to each side of the stern, so the roach would be between them, then for close hauled work where the top is not twisted off, would one still have to drop the main to tack? If the stay is too close to the sail then there would be more chafe unless chafe protection was added. We got a new main a couple years ago and it has max roach for the rig, and in fact, a bit too much for light air tacking. Even though the backstay is loose I sometimes have to push up on it for the sail to clear across - a bit of a pain - but otherwise it sails really good! A cruiser would do this once and as the wind shifts one could just change course; however, in racing this would not be a good tactic. One thing for shure, just a small amount of roach increase makes a noticible difference.
On our 35 the backstay is a single line down to within say 10 or 15 feet of the stern where it splits. Now here's an idea. If your Catalina was similar, what one could do is install two backstays lines, one each from the masthead to each side of the stern, so the roach would be between them, then for close hauled work where the top is not twisted off, would one still have to drop the main to tack? If the stay is too close to the sail then there would be more chafe unless chafe protection was added. We got a new main a couple years ago and it has max roach for the rig, and in fact, a bit too much for light air tacking. Even though the backstay is loose I sometimes have to push up on it for the sail to clear across - a bit of a pain - but otherwise it sails really good! A cruiser would do this once and as the wind shifts one could just change course; however, in racing this would not be a good tactic. One thing for shure, just a small amount of roach increase makes a noticible difference.
Weather helm
Weather helm is a function of where the center of effort of the sail is on a given point of sail and sail trim relative to the boat. This is a balancing act. You have a headsail with a center of effort forward of the mast and a mainsail with a center of effort aft of the mast. These forces create a moment trying to turn the boat in opposite directions. Both also create a force trying to push the boat sidewise that is resisted by the keels center of lateral resistance and the hull itself. For a very slight weather helm (required for safety) all these forces causing rotational moments must balance close to equilibrium (sum of the moments equal to zero). Area alone will not necessarily cause more weather helm. The shape of the sail and position of the center of effort coupled with the headsail being used must all be considered for a good answer to your question.
Weather helm is a function of where the center of effort of the sail is on a given point of sail and sail trim relative to the boat. This is a balancing act. You have a headsail with a center of effort forward of the mast and a mainsail with a center of effort aft of the mast. These forces create a moment trying to turn the boat in opposite directions. Both also create a force trying to push the boat sidewise that is resisted by the keels center of lateral resistance and the hull itself. For a very slight weather helm (required for safety) all these forces causing rotational moments must balance close to equilibrium (sum of the moments equal to zero). Area alone will not necessarily cause more weather helm. The shape of the sail and position of the center of effort coupled with the headsail being used must all be considered for a good answer to your question.
More on weather helm
Of course I forgot to mention heel angle of the boat. For a given wind condition and sail combination and trim you end up with a heel angle caused by the vector component of the forces on the center of effort of the head and mainsail (assuming no spinnaker) normal to the boat centerline. As the boat heels the heeling moment is resisted by the mass of the keel creating an opposing moment about the center of bouyancy of the hull (the position of which changes as the boat heels due to the shape of the hull). But as the boat heels and the keel is no longer verticle it's effectivity at resisting lateral motion is reduced so basically the more you heel the less resistance against rotational moments is provided by the keel and more weather helm results. Weather helm prediction must be accompanied by a set of assumptions for sails, boat design, wind conditions, and sail trim, as well as point of sail. A very difficult problem requiring an emperical solution. I see boats all the time operating with excessive heel angles with skippers fighting the helm and getting no more speed. A good sailor should understand these forces at work and know when to reduce sail, both reefing the main and going to a smaller headsail. The boat with the rail buried in the water makes a nice picture for a magazine but to me is a sign of poor ship handling. Applying more force to a boat to get the same speed makes no sense, it just causes more wear and tear on equipment than required.
Of course I forgot to mention heel angle of the boat. For a given wind condition and sail combination and trim you end up with a heel angle caused by the vector component of the forces on the center of effort of the head and mainsail (assuming no spinnaker) normal to the boat centerline. As the boat heels the heeling moment is resisted by the mass of the keel creating an opposing moment about the center of bouyancy of the hull (the position of which changes as the boat heels due to the shape of the hull). But as the boat heels and the keel is no longer verticle it's effectivity at resisting lateral motion is reduced so basically the more you heel the less resistance against rotational moments is provided by the keel and more weather helm results. Weather helm prediction must be accompanied by a set of assumptions for sails, boat design, wind conditions, and sail trim, as well as point of sail. A very difficult problem requiring an emperical solution. I see boats all the time operating with excessive heel angles with skippers fighting the helm and getting no more speed. A good sailor should understand these forces at work and know when to reduce sail, both reefing the main and going to a smaller headsail. The boat with the rail buried in the water makes a nice picture for a magazine but to me is a sign of poor ship handling. Applying more force to a boat to get the same speed makes no sense, it just causes more wear and tear on equipment than required.
Sail cloth
Jan.6, 2000 Dear Keith Justin and Rick have the real world answer you want on what the big roach main will do to performance. I see Dave has been reading Skene's Elements of Yacht Design again
)) Mind you, he might just be prepared to build that sail for you if you ask him. To answer one part of your question a 10.3 ounce dacron should be about the right weight sail cloth for your boat and where your going, but check with your sail maker to be sure on that, as well as how much larger you might reasonably expect to go. Fair Winds, Brian Pickton of BeneteauOwners.net Aboard the Legend, Rodney Bay, St. Lucia
Jan.6, 2000 Dear Keith Justin and Rick have the real world answer you want on what the big roach main will do to performance. I see Dave has been reading Skene's Elements of Yacht Design again
)) Mind you, he might just be prepared to build that sail for you if you ask him. To answer one part of your question a 10.3 ounce dacron should be about the right weight sail cloth for your boat and where your going, but check with your sail maker to be sure on that, as well as how much larger you might reasonably expect to go. Fair Winds, Brian Pickton of BeneteauOwners.net Aboard the Legend, Rodney Bay, St. LuciaSkene's
Rod, I never heard of skene's much less read it. Thanks for the heads up on what sounds like a good book. Everything I discussed is based on my own mechanical engineering background which trained me to analyze forces on mechanical systems. A boat can be analyzed by a free body diagram with applied force vectors through the various "centers". These are the resultants that are equivalent to the sums of the forces acting all over the boat. Once these are known an analysis can be conducted to see if the boat is at equilibrium (sum of forces equal to zero, basic statics) or in motion (sum of forces not equal to zero, basic dynamics). I've been interested in taking the Westlawn School of Yacht design home study course but have a lot on my plate already. Other than work I'm taking the Masters Course for a Coast Guard captains license, finishing my dinghy. Repairing sails and dodger for my O'Day, and generally stewing over this stinking cold weather in new england. Worst winter in years so far, what happened to global warming???
Rod, I never heard of skene's much less read it. Thanks for the heads up on what sounds like a good book. Everything I discussed is based on my own mechanical engineering background which trained me to analyze forces on mechanical systems. A boat can be analyzed by a free body diagram with applied force vectors through the various "centers". These are the resultants that are equivalent to the sums of the forces acting all over the boat. Once these are known an analysis can be conducted to see if the boat is at equilibrium (sum of forces equal to zero, basic statics) or in motion (sum of forces not equal to zero, basic dynamics). I've been interested in taking the Westlawn School of Yacht design home study course but have a lot on my plate already. Other than work I'm taking the Masters Course for a Coast Guard captains license, finishing my dinghy. Repairing sails and dodger for my O'Day, and generally stewing over this stinking cold weather in new england. Worst winter in years so far, what happened to global warming???
The engineer discovers Skene's!!!
Lawd, a little knowledge is a dangerous thing! LOL Forgive me but it's amazing to hear of Skene's mentioned nowadays. Since mathematicians like Britton Chance and Jerry Milgram made overt strides into the once mystical 'black art' of yacht design in the early '70s, there are not many people left who are well-read in the classics. This ignorance on the part of so-called modern 'designers' leads to those frustratingly frequent misinterpretations of my dad's work (one idiot claimed in print the Cherubini 44 was a direct offshoot of Herreshoff's 45-ft Mobjack– if he'd known anything of the design theory of both boats he'd've known it was like comparing Kathy Ireland to Rosie O'Donnell). I am sure that a 'mechie' like David will enjoy Skene's (a 1937-ish book if I recall). There's plenty of both static and kinetic physics in there to keep most of us tech-heads happy. My dad, who studied in the Westlawn course when he was about 17, sort of forced Skene's upon me when I was a teenager. There are other books of his that I inherited that I would wholeheartedly endorse– my favourite being Illingworth's 1955 book 'Offshore', a sort of Bible for the traditional CCA racing boats which influenced the reactionary IOR of the late '60s and thus the centrist Hunter line that came after it. In these books you get very dry but invaluably objective, factual information about the theory and effects of factors like underbody shapes, mast rake, sail design, rig tuning, and sail trim, as well as plenty of handling, navigation, and competition advice that will never go out of style. This is the kind of stuff that, properly read and comprehended, and coupled with sober, reflective experience, can totally blow out of the water some of the more inane comments of unenlightened 'perception' and 'observation' by less knowledgable people that are the bane of marinas and bulletin boards everywhere. I would sincerely encourage any sailor with half a brain to delve into some of the better (especially the slightly older) books on yacht design and building and handling (and not to be afraid of the racing books either). It's winter now and most of us will be waxing bottoms and tuning rigs before we know it. But there's still time to get in a good book. The Mystic Seaport bookshop has a good collection of previously-owned books on these subjects up stairs (I bought Illingworth's second book there last April). So put down Chapman's and get going, Dave!! JC
Lawd, a little knowledge is a dangerous thing! LOL Forgive me but it's amazing to hear of Skene's mentioned nowadays. Since mathematicians like Britton Chance and Jerry Milgram made overt strides into the once mystical 'black art' of yacht design in the early '70s, there are not many people left who are well-read in the classics. This ignorance on the part of so-called modern 'designers' leads to those frustratingly frequent misinterpretations of my dad's work (one idiot claimed in print the Cherubini 44 was a direct offshoot of Herreshoff's 45-ft Mobjack– if he'd known anything of the design theory of both boats he'd've known it was like comparing Kathy Ireland to Rosie O'Donnell). I am sure that a 'mechie' like David will enjoy Skene's (a 1937-ish book if I recall). There's plenty of both static and kinetic physics in there to keep most of us tech-heads happy. My dad, who studied in the Westlawn course when he was about 17, sort of forced Skene's upon me when I was a teenager. There are other books of his that I inherited that I would wholeheartedly endorse– my favourite being Illingworth's 1955 book 'Offshore', a sort of Bible for the traditional CCA racing boats which influenced the reactionary IOR of the late '60s and thus the centrist Hunter line that came after it. In these books you get very dry but invaluably objective, factual information about the theory and effects of factors like underbody shapes, mast rake, sail design, rig tuning, and sail trim, as well as plenty of handling, navigation, and competition advice that will never go out of style. This is the kind of stuff that, properly read and comprehended, and coupled with sober, reflective experience, can totally blow out of the water some of the more inane comments of unenlightened 'perception' and 'observation' by less knowledgable people that are the bane of marinas and bulletin boards everywhere. I would sincerely encourage any sailor with half a brain to delve into some of the better (especially the slightly older) books on yacht design and building and handling (and not to be afraid of the racing books either). It's winter now and most of us will be waxing bottoms and tuning rigs before we know it. But there's still time to get in a good book. The Mystic Seaport bookshop has a good collection of previously-owned books on these subjects up stairs (I bought Illingworth's second book there last April). So put down Chapman's and get going, Dave!! JC
By the way, about heel angle....
When I was about 15 I taught myself the Sunfish. Not long afterwards I read a very good article by the 1973 or '74 Sunfish World Champion in something like Yacht Racing magazine. You know what the hull shape of a Sunfish is, right? Here is what the article was called: 'SAIL HER FLAT!' As I followed his advice I realised what he meant and it still applies to displacement hull forms. A boat is designed at a static, level attitude. Despite everything that goes on it's theoretically intended to be sailed as close to upright as possible. Things like full-battened mains are intended to derive power from upright heel angles, translating that into forward movement instead of the roll vector. Old CCA boats seemed to speed up when they heeled, but speed is a factor of waterline length and those hulls had 6 ft of overhang on each end. This is why my dad's boats tend to heel early, stay put once there, and seemed to accelerate when heeled. They are closely related to the CCA-type theory under which he learned design and tended to be shorter on the waterline than their contemporaries. (The CCA influence of long overhangs also tends to make his boats more classically beautiful, which people notice without knowing precisely why.) David is right that people ploughing along under too much canvas at very improper heel angles are doing something technically wrong. Their sail shape and keel shape are both compromised (airplanes are not efficient at odd angles of attack either, for similar but not identical reasons). I won't argue with the perceptions those people have got from their experiences. I only know that for a variety of reasons one should try to keep the boat as upright as possible under sail. Sail trim and perhaps a better understanding of its effects in both theory and practice will demonstrate this better than any bulletin-board discussion will. JC
When I was about 15 I taught myself the Sunfish. Not long afterwards I read a very good article by the 1973 or '74 Sunfish World Champion in something like Yacht Racing magazine. You know what the hull shape of a Sunfish is, right? Here is what the article was called: 'SAIL HER FLAT!' As I followed his advice I realised what he meant and it still applies to displacement hull forms. A boat is designed at a static, level attitude. Despite everything that goes on it's theoretically intended to be sailed as close to upright as possible. Things like full-battened mains are intended to derive power from upright heel angles, translating that into forward movement instead of the roll vector. Old CCA boats seemed to speed up when they heeled, but speed is a factor of waterline length and those hulls had 6 ft of overhang on each end. This is why my dad's boats tend to heel early, stay put once there, and seemed to accelerate when heeled. They are closely related to the CCA-type theory under which he learned design and tended to be shorter on the waterline than their contemporaries. (The CCA influence of long overhangs also tends to make his boats more classically beautiful, which people notice without knowing precisely why.) David is right that people ploughing along under too much canvas at very improper heel angles are doing something technically wrong. Their sail shape and keel shape are both compromised (airplanes are not efficient at odd angles of attack either, for similar but not identical reasons). I won't argue with the perceptions those people have got from their experiences. I only know that for a variety of reasons one should try to keep the boat as upright as possible under sail. Sail trim and perhaps a better understanding of its effects in both theory and practice will demonstrate this better than any bulletin-board discussion will. JC
Sail her flat revisited
JC just triggered another thought in one of his notes, which are great, thank you. A sailboat with an excessive amount of heel has the sails at a position relative to the wind direction drastically different then they were designed for. A sail is designed assuming the wind is blowing parallel to the water and the sail is perpendicular to the water, the wind blows across the sail (assume upwind sailing to humour me) creating lift by reducing pressure on the leeward side. Enough for the theory, as a simple example hold a piece of 8.5 x 11 paper on one short edge so it is curled like a sail and blow across the top edge, you will see the paper rise upwards as if by magic. But now assume the sail is set at an angle of say 30 degrees off the perpendicular. The wind hasn't changed so now the flow of air across the sail is drastically different than the sail was designed for, the center of effort position changes, and all kinds of very bad things result. My rule of thumb I picked up somewhere is a 20 degree max angle of heel and then reef. Reef more if conditions increase the heel beyond 20 degrees to the point of dousing sails. Of course roller furling stinks reefed so a headsail change is most desirable but requires effort on the part of us lazy skippers, unless we have a crew to bark orders at. Thanks JC d
JC just triggered another thought in one of his notes, which are great, thank you. A sailboat with an excessive amount of heel has the sails at a position relative to the wind direction drastically different then they were designed for. A sail is designed assuming the wind is blowing parallel to the water and the sail is perpendicular to the water, the wind blows across the sail (assume upwind sailing to humour me) creating lift by reducing pressure on the leeward side. Enough for the theory, as a simple example hold a piece of 8.5 x 11 paper on one short edge so it is curled like a sail and blow across the top edge, you will see the paper rise upwards as if by magic. But now assume the sail is set at an angle of say 30 degrees off the perpendicular. The wind hasn't changed so now the flow of air across the sail is drastically different than the sail was designed for, the center of effort position changes, and all kinds of very bad things result. My rule of thumb I picked up somewhere is a 20 degree max angle of heel and then reef. Reef more if conditions increase the heel beyond 20 degrees to the point of dousing sails. Of course roller furling stinks reefed so a headsail change is most desirable but requires effort on the part of us lazy skippers, unless we have a crew to bark orders at. Thanks JC d
Roach
Well we have a lot of good response here. I really like the larger roach Mains!! I have yet to experience any adverse effects for the larger roach. I do NOT agree that dropping your main to tack is a way to sail thru life. There comes a time when added performance and the hassle factor become out of balance. My feeling is the Dashew main does this. The eliptical roach is extremely effective for upwind sailing and more so than adding boom length. BUT adding so much that you have to prepare so far in advance to tack such as taking a tuck goes way over the hassle factor, for benifit added. You will get almost the same performance added with enough roach to pass under the backstay in all but light airs, and not have to reef to tack. Your design has plenty of room for a longer boom and you will add the most area by combining a longer boom with a foot or so of overlap on the backstay. This addition of boom and roach will be great for off wind sailing at any angle and will help on the tighter angles enough. A good high aspect 7 oz will do fine and if you wanted to will it to your grand kids go for 8. I would also use a Tides Marine Track to ease the friction to the luff slides cause by the extra roach. Mark
Well we have a lot of good response here. I really like the larger roach Mains!! I have yet to experience any adverse effects for the larger roach. I do NOT agree that dropping your main to tack is a way to sail thru life. There comes a time when added performance and the hassle factor become out of balance. My feeling is the Dashew main does this. The eliptical roach is extremely effective for upwind sailing and more so than adding boom length. BUT adding so much that you have to prepare so far in advance to tack such as taking a tuck goes way over the hassle factor, for benifit added. You will get almost the same performance added with enough roach to pass under the backstay in all but light airs, and not have to reef to tack. Your design has plenty of room for a longer boom and you will add the most area by combining a longer boom with a foot or so of overlap on the backstay. This addition of boom and roach will be great for off wind sailing at any angle and will help on the tighter angles enough. A good high aspect 7 oz will do fine and if you wanted to will it to your grand kids go for 8. I would also use a Tides Marine Track to ease the friction to the luff slides cause by the extra roach. Mark
Sailboats are not airplanes
It is, however tempting, too awkward to compare too much of a sailboat's sailing rig with aerofoils, etc. The aerofoil on an airplane does one thing: generate lift. The sail on a sailboat does two things: generate lift and provide propulsion. Worse, the aerofoil, being propelled by either a power plant or gravity, generates lift on its convex surface– the sail, in making the boat's only source of headway, sort of does it on both... or at least its aim is to make way towards the concave surface (aweather). So whilst David has the right idea, it is a little risky, for educational purposes, to compare too closely the air's effects on two very different things. (It's even worse when you bring up landsailers, which we sailed often, and iceboats!!!) I'm sorry but I can't pretend to know enough about the physics to explain it coherently. All I can do is assert to you that what I know was taught to me by The Master and that I do know it (perhaps intuitively, as he was often accused of knowing it, but the fact was he was probably an engineering genius). I think we ought to have started a separate article on these abstruse physics issues rather than ignore poor Keith's question! JC
It is, however tempting, too awkward to compare too much of a sailboat's sailing rig with aerofoils, etc. The aerofoil on an airplane does one thing: generate lift. The sail on a sailboat does two things: generate lift and provide propulsion. Worse, the aerofoil, being propelled by either a power plant or gravity, generates lift on its convex surface– the sail, in making the boat's only source of headway, sort of does it on both... or at least its aim is to make way towards the concave surface (aweather). So whilst David has the right idea, it is a little risky, for educational purposes, to compare too closely the air's effects on two very different things. (It's even worse when you bring up landsailers, which we sailed often, and iceboats!!!) I'm sorry but I can't pretend to know enough about the physics to explain it coherently. All I can do is assert to you that what I know was taught to me by The Master and that I do know it (perhaps intuitively, as he was often accused of knowing it, but the fact was he was probably an engineering genius). I think we ought to have started a separate article on these abstruse physics issues rather than ignore poor Keith's question! JC
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