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Old 25-07-2018, 09:17   #16
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Re: Sail manipulation: a concise description please?

Just remember "a flappy sail is not a happy sail" I won't go into what the others have said but just imagine your sails as vertical wings. The aim is to achieve laminar flow around the sail and to keep it in the best shape possible using the afore mentioned bits of string. Use the tell tales where fitted.
Don't retract the centreboard on a beam reach, you are correct, only on a broad reach/ dead run.
Unlike flying the direction of the wind varies independently and according to your course.
Just try things and practice and never stop learning.
Fair winds.
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Old 25-07-2018, 09:33   #17
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Re: Sail manipulation: a concise description please?

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Originally Posted by belizesailor View Post
Youve done enough reading...go sailing and it will start to make sense.
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^^^
This
Yes, a lot of my sailing students went thru the same experiece. A little confusing and abstract until you actually get on boats and do it, then it starts coming together.

This is why we always sent the materials to them well ahead of time. This way they could read about it, hear it in class, and do it on the boat...after all 3 of those learning modes, most anyone can get sailing...it all comes together and the light bulb goes on out on the water.
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Old 25-07-2018, 09:34   #18
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Sail manipulation: a concise description please?

If the racers are retracting centerboards on a beam each that’s the fastest/most efficient. That’s an empirical argument.

The argument from first prinples is:

As the boat bears away from the wind the sail is let out to maintain a constant angle of attack.

By the time you are on a beam reach the net force from the sail is mostly straight ahead with some transverse load from drag on the hull and rigging and the hull and stub keel provide adequate lateral area to counter this remaining transverse force.

The trick is to determine when the increased speed of retracting the centerboard overcomes the increased distance sailed due to increased leeway.
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Old 25-07-2018, 09:34   #19
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Re: Sail manipulation: a concise description please?

The more of these controls you have the better you can adjust your sail shape. And there are some special applications of down haul or Cunningham. On some catamarans and racing dinghies the mast can be bent with a powerful down haul. 8 or even 12 to one ! Bending the mast flattens the sail and with less tension on the hang more twist can be induced. It does get complicated. But it's fun subject to learn. Have fun
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Old 25-07-2018, 09:48   #20
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Re: Sail manipulation: a concise description please?

You asked if a larger boat has more controls. My boat is pretty small @ 25', has every main sail control mentioned here AND some that haven't been. Just depends on how the boat was fitted out and how you want to sail it. I don't consider any of them to be set and forget. Properly tuned with good sails your boat will handle better and heel less while going faster. I'll regularly turn off the auto pilot just to see how the helm is balanced.
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Old 25-07-2018, 09:52   #21
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Re: Sail manipulation: a concise description please?

I don't know if the size of the boat is the key to more features at all... it's purpose is. Smaller boats that are geared toward racing have all the controls, but some bigger boats (like mine) do not, cause it's not made to go fast, it's made to go far. My boom vang is a rope (so technically a kicker) but I do have a beast of a traveler, so go figure....
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Old 25-07-2018, 10:07   #22
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Re: Sail manipulation: a concise description please?

Thirtywest


Since you fly, think of this:
When the wind is forward of the beam, your sail is exactly like a wing, sailing close hauled is like flying Vx, when at Vx you are a few knots below Vs, on a sailboat you have tell tales on the leading edge of the sail which will show you are approaching Vs as they just start to lift. (Vsw).

You use your sail “manipulators” to position and shape the wing (sail) to the optimum shape for Vx.
As you ease off the wind a bit you are sailing like VY, again you shape and position the wing for Vy

Once the wind gets abaft the beam it is like a power off descent and you shape for more chord etc.

At some point as you near DDW your sail becomes more of a bag to catch the wind and you shape it for the most “bag” so to speak.

Think airfoil and you will use your “manipulators” in a natural fashion to shape your wing.

M
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Old 25-07-2018, 10:19   #23
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Re: Sail manipulation: a concise description please?

Your 1 through 5 is only nomenclature. Sailing itself is common sense other than rules of the road.
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Old 25-07-2018, 10:31   #24
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Re: Sail manipulation: a concise description please?

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Originally Posted by captmikem View Post
Thirtywest


Since you fly, think of this:
When the wind is forward of the beam, your sail is exactly like a wing, sailing close hauled is like flying Vx, when at Vx you are a few knots below Vs, on a sailboat you have tell tales on the leading edge of the sail which will show you are approaching Vs as they just start to lift. (Vsw).

You use your sail “manipulators” to position and shape the wing (sail) to the optimum shape for Vx.
As you ease off the wind a bit you are sailing like VY, again you shape and position the wing for Vy

Once the wind gets abaft the beam it is like a power off descent and you shape for more chord etc.

At some point as you near DDW your sail becomes more of a bag to catch the wind and you shape it for the most “bag” so to speak.

Think airfoil and you will use your “manipulators” in a natural fashion to shape your wing.

M
Aye, that makes sense. It really is beyond academics at this point. I love reading though. I found a pdf floating around that breaks down trimming.

Thanks again. Headed down to Clearlake tonight (TX) to watch the races and window shop for as long as my wife will allow.
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Old 25-07-2018, 12:28   #25
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Re: Sail manipulation: a concise description please?

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So, I've read a few books, and listened to some lectures, and at some point in each I find myself looking at words that seem to contradict the other guy.

I don't know if it's me or perhaps they are speaking of differently equipped vessels--something I see many not mention.

Without going into details about 'when' these features are employed, I'm just looking for a good description--a one liner if you will--for the following as they relate to draft size, draft position, twist and so forth.

I've got over 20 years in professional aviation so the ideas of airflow, attack, foils, and centers of pressure are not new to me. That being said, I'm just needing to get over this hump; are their uses so intricate that it's more intuition than scenario based?



Thanks for the patience.

1. outhaul
2. main sheet
3. cunningham
4. boom vang
5. traveller

bonus question: why would a center board be retracted on a beam reach? It would seem the most amount of slip would be had there.

having been a professional aviator for more than four decades and a very active sailor for more than a half century I've found that teaching a sailor to fly is a walk in the park but not so teaching a pilot to sail. we that aviate tend to be too structured oftentimes to get the hang of sailing I've discovered.

that said, yes it's fine to understand the aero dynamic and hydro dynamic principles but try not to overthink it. most of what I've learned about sail trim came from trial and error and I mean a ton of both. for instance mainsail twist. there was a time that I would reef way to early and I was looking for a way to depower the upper portion of the main which caused excess weather helm and heel, slowing the boat, without all the trouble of tucking in a reef. by experimenting I found that I could pull the traveler to weather, center of the boat, and ease the mainsheet. this accomplishes three things. it powers up the lower part of the sail to keep the boat driving, and as important, pointing high, while spilling the air out of the upper part without the leach flogging. it's that upper region that was causing all the problems. when you think of it this accomplishes the same thing as reefing but can be done from the cockpit in seconds.

as to your bonus question, leeward slip is minor sailing off the wind as opposed to close hauled. downwind, even on a beam reach, you can steer any direction you like and boat speed is king and drag under the water sucks.

I've learned many sail trim tricks this way so keep at it without overthinking the physics involved. one thing that does carry over from flying to sailing and visa versa is the acronym THAR. [that looks about right.] can't be taught but can be learned. have fun.
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Old 25-07-2018, 12:46   #26
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Re: Sail manipulation: a concise description please?

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Originally Posted by foufou View Post
The more of these controls you have the better you can adjust your sail shape. And there are some special applications of down haul or Cunningham. On some catamarans and racing dinghies the mast can be bent with a powerful down haul. 8 or even 12 to one ! Bending the mast flattens the sail and with less tension on the hang more twist can be induced. It does get complicated. But it's fun subject to learn. Have fun
...to continue on this theme:

Its not the size of the boat, but the intended use. Example: cruising boats typically have far fewer control lines than racing boats regardless of LOA.
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Old 25-07-2018, 13:34   #27
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Re: Sail manipulation: a concise description please?

Quote:
Originally Posted by thirtywest View Post
Without going into details about 'when' these features are employed, I'm just looking for a good description--a one liner if you will--for the following as they relate to draft size, draft position, twist and so forth.


1. outhaul
2. main sheet
3. cunningham
4. boom vang
5. traveller

bonus question: why would a center board be retracted on a beam reach? It would seem the most amount of slip would be had there.

1 Outhaul, changes the flappy flaggy thing into an airfoil, when not tight enough, draft is forward, great for landings and take-offs, oh and broad angle sailing, when tight, changes flaps to zero.


2 Main sheet, changes angle of attack of airfoil, but also flattens, so if you have standing helm, or your trim wheels are spinning between the seats, then, give a little and play with your aircrafts c of g or, let out the traveller, and try again.


3 Nothing cunning, tightens the leading edge if your halyard is already topped, moves draft fwd too, and a great thing if you break your boom and want to go loose footed.


4 Boom vang, great to flatten sail without sheeting, also good to create twist, or curve the sail more for wider sailing angles. Also good to have a hard one, then no topping lift is needed.


5 Traveller, opens and closes the door, see #2 above, and does so without affecting foil profile.


Retracting CB, well, it depends on too many factors, in a multihull you have two liquid medium foils, in that case retract, if a mono, specifically a shallow draft "side-slippy" hull, leave some down there, and play with the lift-drag ratio. Me, I leave it down on a beam reach, and only withdraw on a downhill...


Hope the above helps.
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Old 25-07-2018, 16:07   #28
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Re: Sail manipulation: a concise description please?

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Originally Posted by Siberianhusky View Post
You asked if a larger boat has more controls. My boat is pretty small @ 25', has every main sail control mentioned here AND some that haven't been. Just depends on how the boat was fitted out and how you want to sail it. I don't consider any of them to be set and forget. Properly tuned with good sails your boat will handle better and heel less while going faster. I'll regularly turn off the auto pilot just to see how the helm is balanced.

The 24ft J/24 and 30ft Farr 1/2 ton I race both have more sail trim controls that my 43ft cat
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Old 25-07-2018, 20:18   #29
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Re: Sail manipulation: a concise description please?

Keeping life simple.

Traveler.....we use the traveler to ease out the main sail boom . Lets say from close hauled to a close reach or even a beam reach.

We have the main sail shaped properly to the conditions. The shape of the main is like an airplane wing and the draft is properly set. . We wish to fall off the wind, but do not wish to change the aerodynamic shape of the main. So, as we fall off the wind from close hauled to a close reach....................

We just slide the traveler down to leeward a bit. No messing around with anything, Simple easy and getting the most power and maintaining the proper shape of that air plane wing. If the main sheet is eased, the shape of the sail changes. Not good.
------------------------------------------------------------------------------------------------

Also, changing from a reach to close hauled, we can bring the traveler up to windward a bit, and can head up closer to the wind with a properly shaped airfoil ( main sail ) . We are now close hauled . pointed up to stay closer to the wind direction and our rhumb line or intended course to gain more distance toward our destination.

Just some very minor basic points and Keeping things simple.

Properly trimmed mainsail. Think airplane wing and draft up forward when on the wind. Ease the draft aft when sailing down wind.
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From close hauled to a beam reach, trim the LUFF of the main parallel to the wind direction. ( tell tails or mast head fly at the top of the mast ). Take in to account the draft of the sail. Think laying the tell tale in the luff of the mainsail or the luff parallel o the tell tale..
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Another tip. When we have a single or double reefed main, to reduce heel, strong winds, we sometimes will ease off the main sail traveler to leeward, still maintain the sail shape, and reduce the weather helm and sail on a close reach, hauling okole.
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Coming about; HELMS PERSON : Keeping it simple. When to stop your turn. Before coming about, we will slide the traveler down a bit so the boom will be proper placed once on our next tack.

Come about, and the helmsman watches the main, Crew takes care of the headsail.

Come about, and when the main fills again, stop your turn. You will be close hauled on the opposite tack, and flat moving. Check the tail tails and make any minor adjustment for your new close hauled point of sail.
-----------------------------------------------------------------------------------------------

Out haul: I like the foot of the main sail tight, and generally to do not mess the with out haul once it is set and secured.
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Other un- related suggestions "

Cruising , not racing:

Reefing down:

1. When to reef. When we first see the whitecaps on the ocean. Actually , I now just double reef since the wind generally tends to increase and I do not have to go thru another reefing procedure . I am done, We are sailing closer to our lines, and no weather helm or rounding up in to the wind.

2. Plan B. We look at the forecast winds, and the currents winds and wind speed indicators. If we are in for a blow, we double reef before leaving the dock. Simple and easy and ready to sail.

3. A shoe box will float down wind. But we will rig a preventer to the main boom to prevent accidental jibes, wind shifts, or not so good a job at the helm. It can be as simple as a long extra sheet line secured at the end of the main sail boom and run up forward to a bow deck cleat. haul in hard on the main sheet.. That boom is staying put. Usually used when sailing down wind.
------------------------------------------------------------------------------------------------

There is a lot more to sail trim, and running rigging than the above, but you asked for simple idea.
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Oh, and don't forget changing of sheet block placement when reducing the roller snarler jib sail from a 150 to 110% jib or vice versa . Regardless, The foot of the sail and the leach of the sail should have equal tension.

To help out, once you know the proper sheet block placement, you can put a small piece of waterproof tape at the desire positions next to the sheet block rail. Done deal,
------------------------------------------------------------------------------------------------

There is one heck of a lot to learn about sailing and seamanship. These are just some of the very first basics . It gets much more involved.

Some of the other posters mentioned that sailing is an art. And that is a fact.

We will never know it all, and some of us old ancient mariners are still learning, every day when we read the posts here on the cruising forum.







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Old 25-07-2018, 20:40   #30
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Re: Sail manipulation: a concise description please?

All good advice. I suggest you spend some time sailing with racers. Also consider having a sailmaker or other experienced source join you on your boat and walk you through the basics.
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