Technical Question

Discussion in 'Sailing Talk' started by c14_Jim, Dec 26, 2014.

  1. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    When racing up wind I find most skippers pull the boom into center or near centerline and sail by the telltails on the jib: just keep them barely streaming. I suppose this gets the boat with about a 45 degree angle to the true wind, and the apparent wind much closer, depending on the wind speed. But I wonder under good conditions (say a 10 knot wind with little wave action) if this is the best angle. If one were to bear off a few degrees the speed would increase. Would that compensate for the fact you are heading further away from the mark? If you increase your velocity by bearing off is you velocity made good toward the mark increased or decreased or equal? I suppose it differs in different boats, but does anyone have an idea of what the ideal angle to the apparent wind is in the C14? Boat speed vs Angle of Incidence.jpg
     
  2. boat

    boat Member

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    WOW! this sort of question is best answered with a book written by a lot of sailing/racing experts. I cannot answer your question directly but I can provide a few thoughts related to how I try to sail... I will assume you are sailing inland on a relatively short course and not in a 500 mile open water race with currents and reefs to contend with. I am not an expert on anything so take my "thoughts" for what they are worth. Hopefully, someone will provide a good answer here later.

    My first rule of the road is stay with the pack even if they are not sailing the best lines. I don't always do this but in general I adhere that line of thought. It is tempting to bare off and pick up speed or perhaps sail over to where there is more wind but this can be devastating. if you are not in the same general wind as the pack you could shoot ahead or you could get left behind I mean way behind with a wind shift. If in the pack you can make the most out of the same general wind that everyone has to work with and see who knows how to trim sails and manage the rudder best. Think of it this way: would you like to work your way toward the mark by taking the shortest rout at perhaps a slower speed or would you prefer to make good time heading away from the mark? Yep, I agree that this is a gross simplification. I have gotten lucky out in the distance from the pack a few times but more often than not it has cost me in the end. Now with that said; if you can predict a sizable wind shift and bare off at just the right time you can jump boat-lengths ahead but you have to have a crystal ball to predict correctly all of the time. It takes a keen sense of the typical conditions which is possible on a home course but unlikely doable on a strange coursed. The wind is a strange spirit and tends to lie most of the time...

    While I often have the main near center line it has little to do with my basic objectives while trimming sails. I like to sail the shortest line to the mark so I am always pointing high. I start by trimming the head sail so it is producing the power I need to point but this has nothing to do with how tightly the sail is sheeted. There are times to adjust for power and times for pure speed. Trimming the foresail for speed when starting from a very slow speed will put you on the last row every time.With the head sail trimmed I turn my attention to the rudder. I like to sail with very little pressure on the helm. If you are struggling to pull the rudder to the windward you have to remember that you are dragging the rudder sideways to some degree which equals putting on the brakes! I trim the main to relieve the pressure on the tiller and to make the tell-tails on the leach fly as they should. Once this balance between main efficiency and tiller pressure is resolved I find the boat travels at maximum speed and points quite high. Flying the foresail is a delicate dance consisting of pinching until the tell-tails start to stall and then bearing off a couple of degrees. This exercise continues during the complete (mostly) upwind leg.

    Here is a question for you to ponder: Sailing up wind close halled with the foresail sheet tuned to an A sharp; you see a header approaching what do you do? Prepare to head up when it hits? adjust the jib sheet to a power setting? hold your course and do nothing but let the boat heal over with the additional wind? :rolleyes:

    Just a word about trimming the main; to do it properly you must master all possible adjustment points; leach, tuft, out-hall, Cunningham, etc. If you for some reason don't have a good understanding of each of these items; now would be a good time to hit the books and become an expert. I believe you will see a big difference in where you place in a race. The main has all of the adjustment necessary to make it productive in any situation. That is good to understand.

    I don't know your skills so forgive me if all of this is offenciv;)e due to its oversimplification... ;)
     
  3. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    I took some notes while reading your response. I do not disagree with any of it. I have sailed all my life (i'm 74) and have had the dubious honer of coming in second to some excellent sailors, even national champions on rare occasions. I have also crewed with a few people who were consistent winners. Most of my racing has been in one design dinghies. A couple of comments to your post: In the Etchel 22's I crewed on a boat that consistently won. We, the crew, trimmed the sails. The skipper kept track of the competition and looked for new, better wind. "Get your head out of the boat" one excellent sailor I know says. When we were the first to the new wind on the weather leg we got way ahead. The other thing the skipper did was to "heat it up" when things were going poorly on a broad reach in very light air with spinnaker. By that I mean we came up to accelerate. I know that seems like robbing Peter to pay Paul, so it has to be done with an eye on where it puts you relative to the fleet, the mark and any new wind that might be coming. Perhaps when the spinnaker isn't "flying" the difference is so dramatic that changing the heading of the boat is a small sacrifice. Here in the Pacific Northwest we sail on "protected "waters so we sometimes don't get the consistent wind directions ocean sailors get (some would say "sometimes" is an understatement). As for the question on a header. In small boats like the El Toro and Optimist that I have raced you must tack quickly on a header. If you hesitate those who take it quickly will jump ahead. On keel boats and larger centerboard boats like the Lightning I wait 5 or 10 seconds to make sure the header is going to hold before tacking. The larger the boat the more loss you suffer doing a bunch of unnecessary tacks. Thanks for your interesting response.
     
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  4. boat

    boat Member

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    GREAT RESPONSE Jim. I have been sailing sense the early 50s until today and I am pushing 79 years and still have learned nothing. The problem with responding on a forum like this is you never know if you are responding to; a master sailor or a person that has just discovered a sail boat for the first time. It would be fun to set down over a cool glass of water (or whatever) and talk about sailing, racing tactics, sail trim and whatever. I can never get enough knowledge and I find that I learn something new every time I talk with an experienced sailor. I also learn from teaching; especially when newbies ask simple questions like "WHY" which always forces you back to the basics and find a way to respond. Now everyone knows why I clearly state that I am not an expert on anything. My only intent in responding on this forum is to present an opinion that may or may not be helpful to someone with lesser experience in this wonderful world of sail competition. While I have built sail boats, made my own sails in the early years and raced with what I consider world class skippers I still feel I have a lot to learn from folks with your background.

    Sorry I couldn't provide a specific answer to your question.
     
  5. c14_Jim

    c14_Jim Sailing on Shelter Bay

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  6. boat

    boat Member

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    Jim, Obviously I do not have a specific answer to your question; sorry if I rubbed you the wrong way with my blurb. I suspect you are familiar with the document below but it may shed some light for the lesser experienced sailor. If you assume the upwind mark is set correctly this will provide some insight as to the VMG on various points of sail at different speeds. If anyone is interested; these charts exist for just about any AWA and boat speed. They are not necessarily 100% a perfect indication of the results that will be obtained but they beat a WAG. They are only usable when the wend is dead on with the first mark. It is possible to use a little math/interpolation and get some insight as to what is happening down wind. I hope this is helpful to newbies.
     

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  7. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    That was great. I was looking for something just like that. I'll have the graph the results when I get time.
    Thanks. Happy new Year.
     
  8. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    Apparent wind Vs true wind.jpg I do not understand the table you sent. I would like to. Where did it come from? The chart above seems right to me. For example the table you sent says with an apparent wind angle of 30 degrees (common) and a boat speed of 4 knots (common) surely the true wind angle is not 68 degrees. In fact most sailors would guess it would be 45 degrees. And at the same angle and the boat speed 9 knots the table you sent shows 142 degrees true wind angle. Surely I am missing something. The title did not come through in my copy and perhaps that would explain more.[​IMG]
     
    Last edited: Jan 4, 2015
  9. boat

    boat Member

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    Sorry for omitting the title on the first chart. It was an example of an “Apparent Wind speed of 6 knots. You can find the charts in a number of books. I first started using these charts in the early 70s so I am not sure which book(s) currently provides this information – perhaps the internet. If you have a Cost Gard captains ticket I am sure a review of your original study material will contain the information. I would have to think a bit before I could provide a short explanation other than to say the chart is a result of simple vector analysis that provides basically the same information as the polar plots for your boat but they do not account for leeway.


    I would highly recommend using Polar plots for “your” boat because they would be more accurate for your unique application (sails, crew weight, fearing, leeway tendencies. etc.) Using a complete set of polar plots for your boat will go a long way in answering your question as it applies to your specific boat.


    When sailing downwind I always bare off a few degreed (see polar plots) unless the wind is up at which time I head for the mark.


    Polar plots are much easier to create today using GPS. A GPS is also handy in determining the VMG/ETA to a mark. If you are purchasing a GPS for racing be sure to consider getting a marine specific unit; even these units have shortcomings so use with caution.
     
  10. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    All good stuff. Thanks for answering my post. It was just the sort of discussion I was hoping for.
    Jim
     
  11. boat

    boat Member

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    I am new to the C1
    FOUND IT!


    Jim, I finally located one of my books that with a chapter titled “Chapter 20 - Racing: Polar Plots, Sail Selection, and VMG” (only 25 pages of the 514!). This is not a book for beginners so I would only recommend this book for seasoned sailors interested is getting very deep into theory related to sail design, handling, when to use different sails, how to repairthem, etc. Other topics include calculating CE and CF, mast positioning and bend, deck layout for larger boats, crew responsibilities (up to 12) etc. This book has a very good and lengthy discussion on sail theory and trim. It should be noted, however, that the book is written toward larger boats (22’ to 60’ +/-) but most of the information can be applied to the C14.


    The part you would be most interested in deals with Polar Plots, how to construct the plots, the effects of current, VMG in general, Windward VMG, VMG to leeward, the Kenyon Plotter, SMG by computer, and finally the Apparent Wind Speed charts I mentioned earlier. The AWS charts cover AWS from 6N to 24N which should be adequate for the C14 :rolleyes:. Once you have studied and mastered chapter 20 you should (or will) be the expert on the course.


    I suspect you will find a lot of information in the remainder of the book quite interesting as a review of what you already know; but as I alluded to earlier – this book is not for the new C14 sailor and could be a total waste of money.


    The book title is SAIL POWER, by Wallace Ross (The complete guide to sails and sail handling). I got my book in the very early 70s and I made a note in it that there was an updated edition that came out around 74 / 75 so make sure you get the newest version.


    Let me know if this does not solve your question; a few more sailing books – oldies but goodies. And always ready to discuss what little I know about sailing…
     
  12. c14_Jim

    c14_Jim Sailing on Shelter Bay

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    polar diagram colorful.jpg I got a chuckle; I had to laugh at my self. I have the book Sail Power but that is the one book I didn't reference in this regard. It has been a long while since I read extensively in that book and had not really studied chapter 20 for some reason. Thanks, lots of stuff on VMG I will be interested in reading. I found this colorful polar diagram on line. Seems typical in monohull sloops . Jim
     
    Last edited: Jan 6, 2015
  13. boat

    boat Member

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    Jim, so isn't getting older great. I don't know about you but I contracted CRS a number of years ago and it gets worse every day!

    I feel confident that chapter 20 will serve as a great review of all points of sale. Let me/us know your evaluation of the chapter as well as the book. I may have been wrong about discouraging new sailors. There are a lot of books out there that provide great information in somewhat more manageable detail - your thoughts???

    I have attached a picture of the on-board charts in my cute little aluminum holder.
    :D I don't use these "on" the C14 but have used this package for the past 40+ years on larger boats. The aluminum holder has served as a great protection approach but not really suitable for wet sailing...
     

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