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Breamerly

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Posts posted by Breamerly

  1. On 4/5/2021 at 1:38 PM, SloopJonB said:

    Can't be the companies fault - capitalism means that no company would do anything that might fuck up the public - that would hurt their customers and their business.

    Just ask JerKZ how that works.

    Yes. They always take care. They sure do, and it protects all of us.

  2. 2 hours ago, tizak said:

    My $.02 is to connect the compass to the wind and landmarks. Throw in brief info concerning typical prevailing conditions / compass directions and what usually happens when other than typical weather is afoot.

    just my opinion but this is too much theory.

    You can sail small boats all summer without ever knowing - or needing to know - where 'north' is, or how weather works. With sailing student there is already a glut of theory/abstract stuff they have to absorb at the front end - why glom even more on

  3. 9 minutes ago, stief said:

    Too, newbies find it cool calling gusts on the water, once they can "see" gusts coming by the catspaws (etc) 

    Even sailing with my significant other, who has been sailing with me of and on for 5+ years, I notice she has to 'watch' the wind in a way I just don't. I feel where the wind is coming from, and by looking at the sails I can see where it is in relation to the (and vice-versa). She has that sometimes - but other times I can see she still has to stop, look at where it's coming from, then orient that to the centerline of the boat and the set of the sails.

    Still remember sailing as a teenager with a crusty old wooden boat fella who mocked me for looking at the anemometer when the sails luffed. 

    • Like 1
  4. 7 minutes ago, stief said:

    Quick thought: Biggest barrier for really new newbies is the wind. Most of them don't understand that sailors are constantly and unconsciously aware of direction and variation. 

    +1

     

    Continually amazed at how unconscious this is for folks who sail - and how invisible it is to people who don't.

    • Like 2
  5. 19 hours ago, fastyacht said:

    Do the Delkenbaugh calc befor and after...

    Will give you exactly ehat.  You eant

    That's a very straightforward formula that I hadn't seen before, as is WPC. Thank you.

    If I'm understanding correctly, what's most relevant is the heeling moment formula, which is a component of both - Hm = sail area * Cos^2(heel angle) * Heeling arm * Wind pressure.

    @bgytr is it correct to think I could get a sense of the effect of the changes by comparing the moment generated by the same sail area and windspeed with two different Heeling arm values?

    Or in 20 knots of wind, at 20 degrees of heel, the Heeling moment with my current heeling arm and sail area (20ft, 158ft2) is about 1180 Lbs.

    Shorten the Arm by 1 foot and the same moment is reached at a windspeed of.... Drum-roll please.... 20.6 mph.

    If I'm doing that right, seems like a real wet fart of a modification.

    (I do understand that to truly compare stability, I'd need to compare The induced heel of the two configurations at a given wind speed - but it seems like the way I'm doing it here is okay for a rough, rough comparison?)

     

  6. 8 hours ago, Ease the sheet. said:

    Why would you not lower the boom and just get a bigger mainsail?

    Better in the light and you can always reef when it gets heavy.

    That's a great idea. So great, in fact, that I talked to the sailmaker about it yesterday. I think that will be a next year spend, though. 

  7. Sorry if I sound grumpy. Asking for advice on forums is damned-if-you-do/damned-if-you-don't. If you provide lots of specifics, people start answering questions you didn't ask, but if you ask a bare-bones question, people say, 'can't answer the question without more specifics.' And if you really provide a thorough explanation of the details and your whole thought process, you end up with a novel that no one wants to read!

    Everything I've gathered so far is that lowering the CoE by a foot (about 5%) would mean it would take 3-4% higher windspeed to force the boat into the same degree of heel.

    Or, it might buy me something in the ballpark of a knot or two more of wind I could handle before being overpowered.

    Sounds like it's not really worth it.

  8. 1 hour ago, bgytr said:

    In what type of conditions do you predominantly sail?  If it's mostly lighter winds, I'd leave the up where it is as it will be up where there is more wind.  Especially in lighter going, the wind down lower is usually a lot lighter.  If you are out there powered up and heeling 20 plus degrees every time you go out, then it could be worth lowering.

    Pulled up the data on sailboatdata.com.  The benefit that you would see would likely be only in upwind or close reaching when you are fully powered up. You might get an extra tenth of a knot vmg upwind and a similar boost in straightline speed close reaching in strong stuff.  In lighter stuff and offwind you'd probably be better leaving the main up high.  I've not done any calcs to back it up, but just my gut reaction knowing the physics behind it and experience.

    Right. I get that. As I wrote up above, what I'm interested in is the potential utility of making my boom height adjustable, as a way to make the boat a bit more adaptable to heavy weather by giving myself the ability to lower the CE, along with typical heavy air strategies like reefing, active sheeting, and pinching off. To that end I'm trying to understand how much it would change the heeling force, and by extension the windspeed threshold at which the boat overpowers when going to windward.

    Sorry, I posted a lot more specifics in my original on fix-it anarchy, and left this thread a bit bare-bones.

    I am not contemplating a permanent height change. As I wrote up above, I understand that a higher main is intended to 'reach up to the wind' in lighter air, and that lowering it would be better for heavy air. 

    Again, since no one is interested in hearing my entire use case and decision matrix/criteria list, I'm not asking for an overall recommendation about how to set up my rig. I'm trying to understand specifically how much difference this one change would make, in terms of one specific type of force.

  9. 12 minutes ago, AJ Oliver said:

    J-24's also have a terrifyingly low boom - the bane of Learn to Sail. 

    But what's that got to do with lever arms ? 

    Nothing, in that scenario.

    In my case, however, the boom is set relatively high off the deck, with a main cut to accommodate that. 

    By extending the track downward a bit, I'd have the option to lower the boom a little more than foot (it's on a car), and hoist from that lower position.

    Which would give me the same sail, acting on a shorter lever.

    Thus my question: How much of a difference would that actually make (in terms of heeling force)?

  10. 13 hours ago, weightless said:

    From the disdain for cutting the excess from the mast foot I take it this not a cunning plan to reduce the mass moment of inertia?

    I didn't really take it as a serious idea I guess. I didn't ask originally about center of inertia - I asked about the effect of reducing the boom height.

    I asked that specifically because I was contemplating adding adjustability, not making a permanent change (one that would require redoing all my standing rigging and having the genny recut).

    As always on these posts, there's an element of balancing between enough context and too much. I was trying to keep it simple. Apologies if that added confusion.

  11. 5 hours ago, bgytr said:

    What kind of boat?  I am a naval architect, so might have some input if you are congenial about it.

    Whoa whoa whoa there mister, this is the internet, and I'm a stranger - exactly how else am I supposed to react to even the most miniscule ribbing other than by getting insanely butthurt and starting a flame war? lol.

    It's a 1969 Santana 27. I haven't measured yet, but the boom looks to be about 7.5' off the cockpit sole, and about 2.5' (maybe a touch more) off the deck.

    • Like 1
  12. On 4/20/2021 at 10:07 AM, P_Wop said:

    My late dad, a great surgeon and a good sailor, once said, "By the time a man's 50, he's either his own doctor or a fool."

    What he meant by this, I think, was that you should know what your body likes, and what it doesn't like.  You should know how to avoid injury or infection, and correctly diagnose it when you have one.  You should know how much sleep you need, and what sort.  You should know your alcohol tolerance, and keep below it.  You should know what foods are healthy for you, and what foods might be troublesome.  And so on...

    Goddamn. This is some fine advice, and I'm only 35.

    • Like 1
  13. 11 minutes ago, Amati said:

    Is your downhaul on the deck?  Slide the sail down a foot or so (or more) without the boom and go out for a sail.  If you have enough luff tension, it’ll be a fairly close approximation.  You should saw off the top of the mast if you like it shorter, anyway.  Although if that messes with standing rigging and blocks etc, that will be some work....

    Alas. The sail track stops where it is now. To slide it down further I'd have to extend the track (and I guess add a stoppered car to carry it/rest it on).

    Ultimately what I was wondering was whether it was worth the work to make it adjustable as a heavy weather item - have the ability to lower the CE a bit as another arrow in the quiver along with reefing, active sheeting, pinching off, etc.

    Boom has a kicker, so I'd have to also set a second, lower deal for that, to allow moving it up/down.

    For a couple of knots difference in the overpower-threshold windspeed, it seems like more trouble than it's worth, honestly.

    EDIT: oh I see what you mean. Interesting though. But the difference I think would be in stiff weather. Plus, like, no foot tension?

  14. 2 hours ago, shaggybaxter said:

    Could you test your theory by reefing? This should lower your CE of the sail plan and give you an indication, it will decrease your sail area of course, but might be worth doing as a base reference. 
    I get the thinking though, my gooseneck wouldn’t even be 2’ off the deck and I can feel a difference when hopping on opb with a boom 5’ off the deck.

    I have definitely thought about the similarity of it to reefing. But I'm not sure it's comparable, given how much a reef *reduces* the sail area. I don't know how much to ascribe the heel reduction to the lowered center of effort versus the reduced sail area.

     

    And yeah, my thinking at the beginning was that levers often seem to involve an exponential relationship type deal, so maybe a little change would make a big difference. Sounds like, though, a little change would just make a little difference.

     

  15. 1 hour ago, bgytr said:

    Why yes, yes i do.  I'm trying to grasp the point of this discussion.  What miniscule gain do you hope to get by taking the same sail and dropping it down a foot?

    The point is that I'm curious.

    That and I happen to have the boom and gooseneck fitting off the mast, which occasioned me thinking about how much extra room there is between the boom and the deck - far more than is necessary to accommodate standing headroom in the cockpit - and wondering how much that extra room adds to the heeling force on the rig. (I presume the trade off is achieving just a touch more 'reach' on light-air days.)

    I say all this of, of course, in good faith, on the assumption that you aren't just asking what the point is so that you can heap disdain on it from 10,000 feet (rather than contributing).

  16. 31 minutes ago, Panoramix said:

    So you could measure it with all sails down in a harbour just by pulling the top of the mast and measuring the force (how much the boat is lifting you)

    I think this would just be righting moment, wouldn't it?

  17. 26 minutes ago, weightless said:

    Folks have coded the calcs for guesstimates of sail force and moment. eg.  https://cdn2.hubspot.net/hub/209338/news/SailPowerCalc/SailPowerCalc.htm You could play around with your numbers in one of them.

    Great calculator, but something is weird about it. Its listed value for sail heel (which it defines as heeling force exerted by the sails on the mast) does not change when you modify the boom height, even when you use crazy numbers. I think it might have a bit of wonk.

  18. 14 minutes ago, Panoramix said:

    I am not an naval architect and my native tongue isn't English....

    My understanding of the term is that the stiffness of the boat (at least how we use it in French) is how much a boat wants to self-right once you've inclined it. So you could measure it with all sails down in a harbour just by pulling the top of the mast and measuring the force (how much the boat is lifting you). So a boat with a taller will loose in stifness only because the mast will have a weight that wants to make the boat capsize.

    The stiffer the boat, the most sail it can carry in a set wind.

    Stiffening the rig is something different, in high wind you don't want your mast to move in all directions so you want it well tensioned to stop it "pumping" (that is moving like a bow used to shoot arrows!) and make it stiff. There are many things to know about this and entire books have been written about it so I can't say it all with just a few words!

    interesting/excellent. Thanks.

  19. 6 minutes ago, Panoramix said:

    Yes, remembre force is proportional to square of wind speed, so that's about 4% more wind (reefing in 19 instead of 18 knots of wind for instance).

    Indeed. Got it. Thank you.

    That lines up with my even rougher scratchings - something like ~5% windspeed change, or 10% in the most wildly optimistic reading.

    Not huge.

  20. 22 minutes ago, Panoramix said:

    we say it is at deck level (optimistic, very stiff boat), that your mainsail P is 30ft and boom to mast connection is 3ft above deck, CoE will go from 3 + 30/3 = 13 to 2 + 30/3 = 12 so the gain is 8%

    Would that be able to withstand 8% more force/effort at the same amount of heel? 

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