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Thread: Sail making and the conundrum of the camber

  1. #1
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    Default Sail making and the conundrum of the camber

    I will appreciate if some one can help me in what seams to be the more difficult conundrum of sail making.


    How to calculate the camber ratio (the ratio of chord/chamber express in fraction or percentage) of a giving sail. Also how to translate that into broad seaming.


    I am recently new to sail making. So fare I have done 2 sails for currachs. This sails are pretty basic and they don’t have a draft build inside the sail but is created by adding curve to the foot.
    Today I am trying to make a new sail from an existing sail, so in my case I have the overall dimensions. The sail went flat in the floor doesn’t seam to have much of a camber, it does have a curvature at the foot and leech also.


    I do understand the general concepts of camber ratio, draft position, and fullness/flatness of the curve of camber.
    I had a read in the sailmaker’s apprentice by Emiliano Marino and pag 119/120 he explains this concepts. Now he is talking about aspect ratio as in


    height sail x height sail
    area sail


    Is this aspect ration equivalent to calculating the camber ratio of a giving sail?


    If that is the case is the solution expressed in a 100%? Can I go then at the 4 horizontal divisions from luff of the sail, measure the chord and apply the percentage?


    I understand that broadseaming (along curve at foot and darts…) is the translation of this chamber into a 3D shape. Most importantly dictates the position the draft point. It is not clear to me in Marino’s book pag 259 to 265 how he goes about converting a chamber curve desing into broad seaming in the sail specially went he does give general rules in table 6-12 of broadseaming per different material?)


    I was planing to cut the 4 panels with a straight edge on one side and the curve of the camber on the other side (went I have found the draft position and the curve only from that draft position) Or would I just follow Marino’s general tables 6-11 and 6-12.


    Is this adequate any how or to rough of an approach?


    thanks for the help

    Eli

  2. #2
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    Default Re: Sail making and the conundrum of the camber

    You need a different and more simple approach to learning these things. Marino's book is a fantastic effort and has done much to preserve traditional sailmaking technique, but honestly, he isn't the best sail design instructor on the planet. I would strongly suggest that you purchase a copy of Jim Grant's sailmaking booklet "The Mainsail Manual" for a clearer, more straightforward approach to these things. It's probably worth picking up a copy of his Jibsail Manual as well. They're small books and not fancy, but of all the sailmaking books out there, they have, by far, the best chance of teaching you how to design, cut and panel a sail.

    https://www.sailrite.com/search?keywords=books

    How to calculate the camber ratio (the ratio of chord/chamber express in fraction or percentage) of a giving sail. Also how to translate that into broad seaming.
    A percentage of chord width is added to the chord as luff round to yield draft (for example: 2.7% added will create about 1' of draft for every 10' of chord width). This does not "translate into broadseaming". That is a different subject.

    Is this aspect ration equivalent to calculating the camber ratio of a giving sail?
    No, I has nothing to do with it.

    If that is the case is the solution expressed in a 100%? Can I go then at the 4 horizontal divisions from luff of the sail, measure the chord and apply the percentage?
    I don't understand what you are getting at here, but suggest reading Grant's book and learning how to do this properly.

    I understand that broadseaming (along curve at foot and darts…)
    Real sails don't have darts. Period.

    It is not clear to me in Marino’s book page 259 to 265 how he goes about converting a chamber curve design into broad seaming in the sail specially went he does give general rules in table 6-12 of broadseaming per different material?)
    Stiffer, more stable cloth needs more extensive broadseaming than softer, less dimensionally stable cloth. Again, covered in Grant's book.

    I was planing to cut the 4 panels with a straight edge on one side and the curve of the camber on the other side
    That would be a mistake. Computer programs and plotters can make sails using curve-cut panels because they can keep track of the shapes in their little hard drive brains. People can't do that. We use straight-sided panels and varying the seam overlaps to arrive at the same basic sail shapes.

    Is this adequate any how or to rough of an approach?
    It still has a lot of technical knowledge gaps that need to be filled-in and misconceptions which need to be fixed. Unfortunately, sailmaking really isn't one of those things where you can learn a little bit and still design and build a good product. To do a good job and turn out sails that work well and hold up well, you're going to need more studying and some practice. We all had to start somewhere, so just keep learning.

  3. #3
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    Default Re: Sail making and the conundrum of the camber

    For what it's worth, you can learn a whole lot by searching through Todd's posts regarding sails. Many people (including myself) have asked sail making questions here, and Todd has put out a great amount of valuable material in response. A Google search of forum.woodenboat.com is better than our forum's search engine.

    Good luck!
    Dave

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    Default Re: Sail making and the conundrum of the camber

    I started sailmaking about 25 years ago with the same questions you have. The Sailrite Library helped me start but what really helped was meeting Robert Laine who had written Sailcut 4, google it, a program to design a, or any, 4 cornered sail. I used it the first time to make templates for a lugsail on a family boatbuilding project boat and made a few dozen sails for them. Then it could only do crosscut sails but since then vertical cut can also be done. I haven't used it lately as I work now with a sailmaker who has a plotter/cutter. However he could not cut a square sail and then explained me how to do that, with vertical cut panels, on the floor. It worked. Frank
    Www.oarandsail.nl

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    Default Re: Sail making and the conundrum of the camber

    What kind of sail?
    What usage of the boat?
    What panel orientation?
    What material/s?
    What techniques?

    Personally, I try to calculate everything as precise as possible in the design process, but when actually lofting I go mostly by eye.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    Thank you very much for your concise replay Tood.
    I can see I have get things wrong. I will get the books you have recommended and clarify a bit more. I can see this will be a long road alright. I will check inside this forum as recommended too. Thanks for your time.
    Eli

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    Default Re: Sail making and the conundrum of the camber

    Thanks Dave,
    Will do that.
    Eli

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    Default Re: Sail making and the conundrum of the camber

    Hello Frank,
    The sails for a currach are 4 cornered sails alright. This one I am doing it is not. Unfortunately I do not know the boat it is for. This is a commission (at this point adventure) I toke as a test but I now I can see fare more complicate. Will keep at it.
    Thanks
    Eli

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    Default Re: Sail making and the conundrum of the camber

    Thanks for you reply Mats.
    I have started the other way around. I don't know the boat or type of sail. Luff to leech orientation, dacron 6oz, and techniques well unsure...Thanks for the suggestions will need to get lots of info and practice before I can do anything by eye.
    Eli

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    Default Re: Sail making and the conundrum of the camber

    By boat I mean is it a small dingy used by children, a traditional fishing boat now used for daysailing, or a sailracing boat.
    By type of sail I mean is it a lugsail, a jib, a bermudan main... I guess it's a working sail, but it could be a stormsail...
    Also size of boat/sail is of some importance.
    By techniques (closely related to material) I mean will it be hand roped? Will you do any detail work by hand? and things like that.
    I consider these things to be of much more importance than, say, the width of the broadseams or the camber of the luff.
    Or rather, they affect how to decide about said and other aspects of sail-design.

    I'm guessing a balanced lug? On a fairly small boat, 5 m long perhaps? Since it's a replacement sail I guess it's not a very new boat.

    6 oz seems a bit heavy to me, but probably ok for a lugsail. For an old, perhaps traditional, originally fishing boat, I wouldn't bother TOO much about broadseaming, cambers and such; don't get me wrong, do your best, but it's not a boat that will win any races after all.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    By techniques (closely related to material) I mean will it be hand roped? Will you do any detail work by hand? and things like that.
    I consider these things to be of much more importance than, say, the width of the broadseams or the camber of the luff.
    I certainly don't. The things you are mentioning are trim-out options, and quite frankly, they have much less to do with how well the sail works and sets than issues like the broadseams, luff shape, camber, entry angle and other design features. By the time you even get to steps like roping, the quality and performance of the sail has already been pretty much determined. There are also always a variety of ways to properly address the trim-out features, and seldom is one way the "only" way to do these things. You can be the best hand-sewn, fancy-trim sailmaker on the planet, but if you don't have a seriously good understanding and grasp of the important design issues, your sails are never going to be good ones or work very well. As I have said here on previous occasions, you can't make a good sail if you don't know how, and nobody that I know of was ever born a skilled sailmaker. A good deal of that involves learning what is important and what is not, since every sail is a mixture of compromises.

  12. #12
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    Default Re: Sail making and the conundrum of the camber

    Todd, you are citing just a part of what I said.
    I stand by that if it's a sail for a child in a dingy or a sail for an ocean sail racer is a big factor in determening how to build the sail.
    As I said, you should always do your best, but focus may be a bit different for different boats etc.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    I cited a portion of your statement that is simply not true - whether standing alone or surrounded by other stuff (which in this case is actually pretty meaningless and vague). A sail for a child's dinghy and a sail for an ocean racer both use most of the same design and construction principles and neither one will be a very good sail if they don't. If you ever want to become a good sailmaker you will need to learn this. Build a whole bunch of sails of various types, sizes, materials and designs and you will eventually see what I'm talking about.
    Last edited by Todd Bradshaw; 01-03-2018 at 04:32 AM.

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    Default Re: Sail making and the conundrum of the camber

    I don't mean that design is not important, what I try to say is that design needs to be a bit different depending on loads of stuff.
    Then, for anyones first sails, one will mess up somewhere in the making process. I'm not so sure it's wise to spend too much thought and time designing. Especially if one doesn't know eg how the sail will be used.

    For my second sail-set, I spent days calculating CE and redrawing the sail-plan, but once I lofted, I made a thinking mistake that made the mainsail a bit lower than planned. In retrospect I believe that it had been a better sail if I had spent less time calculating CE and more time on lofting.
    Sure, one may argue that I should have done both, but I don't think that is realistic.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    Eli, could you show us pictures and sailplan? I am getting curieus. I saw several curraghs in Brittany this summer but I don not remember seeing a daggerboard, keel or leeboard. So is this a stict downwind sail? Frank

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    Default Re: Sail making and the conundrum of the camber

    I'm not so sure it's wise to spend too much thought and time designing. Especially if one doesn't know eg how the sail will be used.
    You are making a lot of assumptions which are clearly beyond your experience level, and this beautifully illustrates my point. Designing a sail does not take very long at all - if you know how to do it in the first place! The lofting itself is not a design step, it is the step where you put down what you already know on the floor, full-sized. The reason that amateurs fumble around for so long with aspects of the sail design phase is that they haven't yet learned enough about the subject to feel comfortable with the concepts. Unfortunately, skipping or slighting those steps because you aren't comfortable with them, or getting some free computer program to do them for you so that you don't have to study and learn them is not likely to make you a decent sailmaker, or produce high quality sails.

    Sailmaking is not terribly difficult, but much of it entails being aware of, keeping track of, and accounting for a whole lot of little tedious bits of information. By the time the first piece of string or masking tape touches the floor to start lofting, the design should already be done and those tedious bits should have already been addressed. Beginners often tend to think that if they can buy fabric, or find an old Genoa to cut up, then they have everything they need to make sails. It doesn't quite work that way.

    In retrospect I believe that it had been a better sail if I had spent less time calculating CE and more time on lofting.
    Sure, one may argue that I should have done both, but I don't think that is realistic.
    Why on earth would spending the required time to get both of these right be unrealistic? Especially when getting them right has a huge influence on how well (or not) the sail actually works! That's like saying "Gee, I really wanted to be sure the garboard fit well against the keel and wouldn't leak, but I wanted to get on with the rest of the planking."

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    Default Re: Sail making and the conundrum of the camber

    Todd, I think you misunderstand me.
    If you know how to design a sail, if you know how to loft a sail, if you know how to sew a sail, if you know how to rope a sail, and so on, you may very well produce a very good sail; but most beginners don't have expertice in all those areas.

    I know perfecty well that lofting has nothing to do with design, it is nevertheless an important step of sailmaking.

    Is sailmaking difficult? I once went on a corse on how to program device drivers (the tiny programs in your computer controlling small background things) and the teacher said something like "it's like being killed by a thousand paper cuts".
    I think sailmaking is a bit similar, there are so many mistakes you need to avoid.

    As for the boatbuilding reference, it may be a good idea to take shortcuts with the garboard and get on with the planking, to get the boat finished in a reasonable time. And then build another, better, boat.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    As for the boatbuilding reference, it may be a good idea to take shortcuts with the garboard and get on with the planking, to get the boat finished in a reasonable time. And then build another, better, boat.
    This line of "reasoning" makes absolutely no sense to me at all, and it will certainly never make you a good sailmaker, rigger or boatbuilder. Cut corners in order to finish the job faster? Since when is a "reasonable time" less time than it takes to do the job properly? How many sails have you made and how many do you plan to toss away as rejects before you actually take the time and put in the energy to make a really good one?

    The most important sail is always the one you are working on now - not the one after it. That's how you turn out a good product, and if you ever plan to seriously pursue the very limited traditional boating market you had better add that to the list of things to learn.

  19. #19
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    Default Re: Sail making and the conundrum of the camber

    My boatbuilding teacher told me: Give the first boat away, sell your second boat, and keep your third.
    I cut corners there and sold my first and kept my second.

    I have only made 6 sails, working on two more, so I am certainly not in your league. I made two sails that I sold and the buyer is very happy with how they performed.
    And I did my best in both designing, lofting, sewing, roping, detail work...

    Let me ask you, when you made your first sail, how much time was used for design?
    I spent probably more time designing my first set of sails than making them, and those were hand sewn, hand roped sails.

    As for rigging, I did cut corners to be finished in time during my aprenticeship, all accepted by my master as reasonable choises. Some of them I wouldn't do now that I am employed as a rigger, but some I might. It's a matter of time verses results.

    I sense a kind of rudeness in you that I have seen before against others, and I don't really see that I deserve it.

    /Mats
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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    Default Re: Sail making and the conundrum of the camber

    radial lateen.jpg

    This is the first sail I ever built (1980) and we still use it today. I put a considerable amount of time into the design because I wanted to have a tri-radial lateen for my own use and had never seen anybody build a radial lateen. I was working repairing and inspecting hot air balloons at the time and sailmaking was more fun, along with having less potential liability. Before that, I was a Hobie Cat and AMF Alcort dealer and owned a Hobie 18, so I was familiar with sailboats and the demands put on sails when in use.

    I continued to work on sails, both building new ones and doing repair work. The repairs weren't much fun, but offered a wonderful opportunity to see what holds up over time and what doesn't. I suppose my most notable statement for repairs was "These idiots should have known that this would fall apart!" which was needed to be uttered far more often than it should have been. I went through a stage of building exotic Kevlar and Technora full-battened, fat-headed radials and then eventually went the other direction, toward traditional styles. I don't know how many sails I have built, but I have around 300 building plans on my old Mac computer and even if I had only built five or six sails per year, the total for 37 years would be in the 200 sails range.

    Rude? Maybe, but I freely admit to being a perfectionist about the work I do. I'd rather improve efficiency than cut corners on quality and I have little patience for those who do. There are few excuses that justify it. I think my customers over the years have appreciated that. You are welcome to your opinion on it and to work to your own standards. If correcting bogus statements on an internet forum makes me rude, I can live with that. I think I have the body of work to back up what I'm saying, and I'm not forcing anyone to read it.

  21. #21
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    Default Re: Sail making and the conundrum of the camber

    It's a bit funny, really.
    I realized that "cutting corners" has a bit of a different meaning than what I intended to say. I meant more like "enough is enough".
    I learned English in school as my second language, as most kids in Europe, but when I REALLY learned it (not saying I'm more than decent at it precently) was when I started using it.
    By using my limited ability I learnd that "cutting corners" means more like "taking shortcuts".
    I think this learning process translates to many trades or skills.

    /Mats
    Last edited by mohsart; 01-04-2018 at 12:19 AM.
    My blog about my time as a boat building student, a rigger apprentice and Journeyman http://kaptenmohsart.blogspot.se/

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