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Old 22-01-2020, 21:20   #46
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Re: Headsail vs no headsail, efficiency

These may be of interest to you. They are to me now!






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Old 27-01-2020, 08:12   #47
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Re: Headsail vs no headsail, efficiency

I was reading this past weekend about a couple while cruising had extra reefs put in their main. They felt the boat was better balanced while running both sails. Their conclusion was backed up with the boat sailing a straighter course using wind vane steering They also found the boat had more speed.
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Old 27-01-2020, 08:30   #48
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Re: Headsail vs no headsail, efficiency

Many good answers to the WRONG question.

If the vessel is designed by a reputable designer, it will work best rigged as DESIGNED.

My ketch handles best in a strong but sailable wind with 1/2 the head sail, double reefed main and single reefed aft. We use the cutter sail position when there is too little or too much wind. The mizzen mast is actually so situated that you can not tell if I am really a ketch or a yawl. It might actually depend upon the sail deployment.

Efficiency is a word not well suited to be applied to sailing. Efficiency as a term is best suited to situations where all the elements present can be quiesced to a steady state so as to evaluate two other elements in the steady state.

Like a new, just washed, car being driven in top gear on a level dry well maintained concrete road with no true wind, with new tires properly inflated as specified by the manufacturer, all windows up, going 60 miles per hour for an hour. The temperature to be held at 70 degrees Fahrenheit, no cloud cover. You could then calculate the efficiency of the fuel use as required to defeat the drag.

If you take that example, and convert it to a sailboat under way, how many of the parameters specified for the automobile test could be expected to remain constant for an hour in order to measure something else?

Get a boat well designed, and get sails to handle the conditions that might occur.
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Old 27-01-2020, 09:11   #49
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Re: Headsail vs no headsail, efficiency

Some boats can hardly sail at all under main, alone. Hopefully the designer envisioned the best sail plan to balance the rig. Efficiency rating? Redundancy on a boat is always a good idea.
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Old 27-01-2020, 09:28   #50
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Re: Headsail vs no headsail, efficiency

IMO, the balance of the boat would be at least as important. If you had a lot of rudder deflection it will increase the drag. Of course, if you position your masts for sailing with no headsail, that isn't an issue.
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Old 27-01-2020, 11:42   #51
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Re: Headsail vs no headsail, efficiency

Two simple facts that make it clear that one sail is better than two:

1) Efficiency is the lift (forward force of the rig). For all the same reasons that airplanes used to have two or three wings, but now all have _one_ wing, sailboats have been steadily moving to a single wing or sail. The A-Class Cat is a great example. There are no competitive two sail A-class Cats because they are less efficient and will lose in a race. So, despite various folks' opinions, the efficiency question is obvious: One sail.

2) There is greater wind speed aloft than at the surface. When there are large swells it is dramatically clear as one can feel the wind on deck drop off substantially in the lee of the wave and increase at the crest. Therefore, a tall rig with a single long luff and a short foot will always produce more power for two reasons: First, it reaches up to where there is more wind. Second, because a high aspect ratio sail (long luff short foot) is clearly more efficient. Google the wings on a sailplane/glider and take a look.

So, for efficiency, you want one sail and as tall a rig as is practical.

There are other factors:

1) Humans aren't able to manage sails above a certain size without mechanical help, like roller furling, etc... The maximum sized sail which a human can deal with has increased tremendously as we've added complex devices to sailboats. In 1900 500 sq. feet of sail per person was considered a safe ration. Today one can easily manage 1,500 sq. feet of sail per person with roller furling and powered winches. In extreme cases, people are managing 3,000 sq. feet of sail area per person.

2) The devices which allow people to manage large sails are expensive, heavy, and hard to keep working well compared to the simply rigging of 1900. They work, but numerous cruisers end up stuck in port waiting for parts to repair their powered winches or roller furling system. Many sailors can't afford the most efficient rig.

3) When things go wrong with a large single sail, it's dramatic and can be dangerous. A rig with multiple sails and/or masts divides up the force and creates a vessel with a much lower risk of injury if/when something goes wrong.

Finally, some of us just like the look and feel of a multi-masted vessel. Efficiency isn't why we travel by sailboat. Obviously, fishing boats and cargo vessels would still have sails if sailing was more efficient and reliable than engines - it isn't. So, the simple fact that we're discussing the efficiency of a sailboat rig proves we've already decided to do a painfully inefficient thing - sailing.
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Old 27-01-2020, 11:52   #52
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Re: Headsail vs no headsail, efficiency

Quote:
Originally Posted by catnap892 View Post
Some boats can hardly sail at all under main, alone....
Keep in mind that this type of comment describes how a boat designed to have two or more sails performs with only one of them, a main, often smaller than the headsail and with it's efficiency harmed by the presence of the mast at the leading edge.

That same boat with a larger mainsail, one with area equal to the designed area of the combined sail plan, and a small diameter mast, might sail much better.

My own boat, which sails well with very little sail area, does fine with just a main. Of course it is slow upwind, but it works. On any other point of sail if the area of the main is appropriate for the wind strength, the boat sails very well with just a main. However, I think it sails better with a small jib and a reefed main than it does with only a full main. The two sails working together add to efficiency, I think.
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Old 27-01-2020, 15:04   #53
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Re: Headsail vs no headsail, efficiency

I hope you find the attached article interesting. I also suggest reading the article "The Enigma of Aerodynamice Lift" by Ed Regis in the February 2020 issue of Scientific American.
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File Type: pdf A Review of Modern Sail Theory.pdf (1.91 MB, 25 views)
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Old 27-01-2020, 23:05   #54
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Re: Headsail vs no headsail, efficiency

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Originally Posted by Dr. D View Post
I hope you find the attached article interesting. I also suggest reading the article "The Enigma of Aerodynamice Lift" by Ed Regis in the February 2020 issue of Scientific American.

The attachment was was quite interesting, thank you. Will read the article soon.


What I'm taking away from the attachment is that the jib/main combination allows you to point a little higher into the wind as well as giving you a greater range of angle of attack on the main(or both?), and a bit better overall efficiency.


Thank you also to the others for your input.



These were the kind of responses I was hoping for.
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Old 27-01-2020, 23:08   #55
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Re: Headsail vs no headsail, efficiency

If you were to try and convince me not to go with a ketch with no headsail, what would your argument be?



If you think I'm on the right track for my needs, why do you think so?
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Old 28-01-2020, 10:09   #56
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Re: Headsail vs no headsail, efficiency

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Originally Posted by dustman View Post
How much more efficient is the combination of headsail/mainsail than a mainsail alone of the same overall area? 10%, 20%? What other factors to consider? Complexity/simplicity and overall ease of use in adverse conditions?



This is in reference to ketches/schooners.
It's not that simple. In principle a single sail is more efficient, BUT!
To have the same overall area mainsail must be taller, wider or both. If wider the aspect ratio is less and so is the effiency. If taller the heeling arm is longer and thus you must reef earlier and loose power.
Depends also of the point you are sailing. Hard beating favour single sail as the L/D ratio is better. But anything else changes that script..
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Old 28-01-2020, 18:56   #57
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Re: Headsail vs no headsail, efficiency

Depends on the size of boat but I think a cat ketch rig is probably what you'll settle on, with no headsails, perhaps even with wishbone rigs to gain the self-vanging advantage. You'll have two more efficient foils driving you and they'll keep the CE lower.
This discussion may be of interest.
https://www.boatdesign.net/threads/c...rimaran.60367/
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Old 31-01-2020, 10:19   #58
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Re: Headsail vs no headsail, efficiency

What about Chris White's Atlantic 47 rig and sail plan. Any comments on the efficiency of a sail plan with two headsails instead of a main ?
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Old 31-01-2020, 12:06   #59
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Re: Headsail vs no headsail, efficiency

Quote:
Originally Posted by Don C L View Post
Depends on the size of boat but I think a cat ketch rig is probably what you'll settle on, with no headsails, perhaps even with wishbone rigs to gain the self-vanging advantage. You'll have two more efficient foils driving you and they'll keep the CE lower.
This discussion may be of interest.
https://www.boatdesign.net/threads/c...rimaran.60367/
This choice will boil down to what is in the heart of the OP. He will find weight in the arguments which support his choice. Rational and objectivity have less impact when a sailor sees what makes his heart sing.

I have experience with ketches with free standing masts and wishbone booms. Two of them, one a Freedom 40, the other a beautiful Herreshof ketch (below) were owned by close friends and I have sailed on both And Tom Wylie has produced some excellent and good performing boats with free standing masts and wishbone rigs (see below). I believe that Randy Repass owns one. One look at them though and one can see that the single forward sail is huge. Google "wylie cat".

Ketches of this type of rig have some valid claims to simplicity, and both the ones I've sailed were powerful off the wind, however they both lacked windward performance. This lack was such that I know of a couple of occasions when the passage had to be curtailed when it became apparent that even with a headsail the boat could never make the needed distance to windward.

To enjoy the benefit of the interaction and efficiency of two sails working together the best solution, in my view, is a mast head sloop.
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Name:	Randy and Laura sailing Pollen Path DSCN1214.jpg
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ID:	207927  

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Old 01-02-2020, 12:45   #60
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Re: Headsail vs no headsail, efficiency

It will certainly be a catamaran, approx 30' waterline, 12' beam, either a schooner or ketch, leaning towards a gaff rigged ketch with freestanding masts. Since I am limiting the beam so much I want to split the sail plan up to keep the center of effort low. A ketch, in my limited experience but abundant research, seems like it gives you a lot of options and control. The hulls will have no storage or accommodations, being something like scaled up versions of hobie 16 hulls but not quite as skinny, there will only be a very small, highly aerodynamic cabin on deck, everything mounted on an aluminum frame. The whole idea is simple, cheap, light, minimal windage, minimal draft, and easily handled by myself alone and an eye to reducing/eliminating potential maintenance and failure points. The loaded displacement for myself alone should wind up being about 1200 lbs, with a sail area of 120-150ft2, divided between fore and aft masts, thinking about a 60-40 sail area distribution, with sails of 3 to 1 aspect ratio.
[/QUOTE]

I love your design ideas! I am building a quite similar cat, with somewhat similar goals, and using a rigid wing for power (in addition to some electric motors... solar panels... and a gasoline engine for times when moving very fast or clawing off a lee shore is required. Mine will displace 3000 lb, about half the weight of a Maine Cat 30. Mine shares your narrow beam dimension, and uses a small amount of carbon fiber reinforcement in critical areas, and is certainly of ultralight construction... at least for something that can cross oceans, survive a capsize, groundings, etc. So I think you will find 1200 lb empty, (let alone with a person on board) hard to achieve... unless you make the construction pretty exotic.... or uncomfortable fragile.

However, if you are mainly interested in cruising in protected areas or only in places where the water is warm (so you can survive a calamity), 1200 lb is possible without getting too exotic. And weight begets weight (and cost), so sticking to your goal can be a very good thing.

I am not at all trying to be a naysayer, and as if to counter what I just suggested re your design being too light. I submit this: A previous boat I built was 16 feet long, had three hulls with 20 foot beam, was powered by a composite rigid wing, and weighed just over 200 lbs empty, including the rig. For it, wing efficiency (expressed as L/D) was one key to its going several times wind speed. Working against wing efficiency, is Fh/R, the other ratio that determines sailing speed vs windspeed. Fh is heeling force (meaning the maximum heeling force that can be sustained as the boat sails in is designed attitude) and R is resistance (which, in this case, means resistance of the hull through the water combined with the component of aerodynamic resistance that aligns with the hull's path through the water). The wing from a sailplane is wonderfully efficient, but far too long (for its sail area) to be used on a sailboat. The wing of a c-class cat would look short and fat and complicated and gnarly on a sailplane.

So... for "efficiency" as the term is used in aerodynamics, a long, skinny, clean (i.e. no flaps etc) wing (exactly what you see on a sailplane capable of 60:1 glide ratio ) is just the ticket. But, for a sail boat, all sorts of other issues com into play... and aerodynamic efficiency ends up being traded away for many many other reasons... even in boats designed, like my little tri, to go very very fast without regard for comfort or ease of sailing. The wing on a c-class cat, with its flap, slats, multiple sections, etc. trades away aerodynamic efficiency for aerodynamic power... so the coefficient of lift is very high, but the coefficient of drag is necessarily also very high... albeit not so atrociously high as it is in most soft sail arrangements.

If you can live with having two sails, one per hull, there is a lot to be said for that arrangement -- not the least of which being that you could find two 9 meter windsurfer rigs for next to nothing, if you uncover the right garage somewhere. (Actually the right two garages -- most well equipped windsurfers have several rigs, but not two identical rigs.) A hull makes a relatively efficient location for a cantilevered rig.

Another of "Ken's weird boats" had a canted rig. It was a tiny proa. An imaginary line normal to the sail and projected through the sail's center of effort went through the centerboard's center of effort, so there was no heeling couple. That meant that the boat did not heel at all... stead winds, gusts, etc all resulted in a flat boat. A little odd, and shunting was required instead of tacking and gybing... but all in all a pretty neat little boat. (Not an original idea on my part: there have been many others of the type, some vying for the outright sailing speed record a while back.)

But to reiterate: cool design! I wish you success. Ketch (or yawl) rig is a good idea and I (personally) would not be overly concerned with things like slot effect (which doesn't happen in a meaningfully beneficial sense in sail rigs) or interference effects either... which, if you are just reasonably careful, can be largely avoided. An "Aero Rig" is a possibility too, although the cantilever loads can mean a heavier structure than you might want at the base of the mast. Sailplane aspect ratios are typically 30:1 or higher, so much of the esoterica of aerodynamics is of little concern when considering realistic sailing rigs. The 3:1 ratio you mention is fine, although it wouldn't hurt to try for a little bigger number there (via square top rig, fully battened rigs, etc.)

If you have not already built a boat, you will (I hope) find the process itself (and especially designing your own boat) very gratifying. (It reminds me of learning to fly. I've said many times that the process of learning is justification alone -- that one can then fly places is icing on the cake.)
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