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Stalling in a tack

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C25BC
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Canada
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Initially Posted - 06/24/2019 : 08:46:22

We had couple hours to sail the other day so we went out planning to use just the furled headsail , not something I usually do. It was blowing around 15 knots and soon went to 24 with some healthy gusts . I was furled to about 110% on my 135 genoa and kept stalling when trying to tack and had to gybe out of it a couple times, also when heading in I had the rudder hard to port on a beam reach just to maintain the heading.
Needed to keep speed over 4.5 kts to tack. Any feedback on my obvious errors ?

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

islander
Master Marine Consultant

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Response Posted - 06/24/2019 : 09:10:11

I headsail only often and don't have any of those problems. If anything my boat is slightly more in balance from what my tiller tells me. Maybe a tuning issue? Is your keel fully down?

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 06/24/2019 09:14:47

Steve Milby
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Response Posted - 06/24/2019 : 10:19:44

quote:
Originally posted by C25BC

We had couple hours to sail the other day so we went out planning to use just the furled headsail , not something I usually do. It was blowing around 15 knots and soon went to 24 with some healthy gusts . I was furled to about 110% on my 135 genoa and kept stalling when trying to tack and had to gybe out of it a couple times, also when heading in I had the rudder hard to port on a beam reach just to maintain the heading.
Needed to keep speed over 4.5 kts to tack. Any feedback on my obvious errors ?

This is an excellent question, and essential to really understanding how a sailboat works.

Each sail on a sloop has a center of effort (CE). That's the center of all the pressures on the sail when the wind moves across it's surface. Those pressures are what drive the boat through the water.

If a sailboat had no keel, it could only drift downwind, like a leaf floating on a pond. The keel of a sailboat provides a large, flat surface below the water which resists the boat drifting sideways, but allows it to move forward easily. The keel translates the sideways pressure on the sails into forward motion. The center of the resistance that is created by the keel is called the center of lateral resistance (CLR). When a sailboat turns, it rotates around that CLR. When the bow turns to windward, the stern turns to leeward. The CLR is the sailboat's pivot point, like the center hole of a record on a turntable.

In the image below, the smaller CEs represent the CE for each individual sail, i.e. the mainsail and jib. The larger CE represents the CE for both the mainsail and jib combined.

If you only raise a 100% jib with no mainsail, all the pressure on the sail is forward of the CLR, and it pulls the bow to leeward. That's what caused your problem. You needed some pressure aft of the CLR to push the stern to leeward, while the jib pushed the bow to leeward. That would have provided a balanced sailplan that would have enabled the boat to sail to windward.

There are two ways to create that balance. The obvious way is to raise some mainsail. That would provide some pressure aft of the CLR to counterbalance the pressure on the jib, forward of the CLR.

The other way is less obvious. With an overlapping jib, most of the sail area is forward of the CLR, but part of the leech is aft of it. The part that is aft of the CLR provides enough pressure to push the stern to leeward to counterbalance the pressure caused by the other part of the jib. Thus, you can improve the balance of the sailplan by unfurling more of the jib.

As you found out, when the pressures on the jib are too great, the rudder isn't able to overcome them enough to force the bow up to windward.

The sailor's goal is to trim the sails so perfectly that the boat will sail to windward in either strong or light winds with a perfectly balanced helm. It's a pleasure to sail a boat that doesn't make you arm-weary from having excessive tiller pressure.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 06/24/2019 10:23:42

islander
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Response Posted - 06/24/2019 : 11:54:24

Steve, Technically that is all true but it doesn't answer the question as to why he is having these problems and I and others don't. This is my U-Tube video of me sailing in strong winds with my 135 rolled up to about 100. Similar to what he had. Technically going by what you said the nose of my boat should be pushed to port with me fighting the tiller trying to hold her on coarse. In reality my hand wasn't even on the tiller, It was holding the camera. On that day and many more just like it if I had any part of the main up (reefed) I would have been overpowered.https://www.youtube.com/watch?v=Mh9SmFxOXPo

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Steve Milby
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Response Posted - 06/24/2019 : 13:00:18

Scott, sails aren't the only things that can create pressure either forward or aft of the CLR. Anything that creates windage can create pressure. In your video, your bimini is creating considerable pressure aft of the CLR, pushing the stern to leeward and driving the bow to windward.

When you have that much wind, the pressure caused by the bimini is considerable. You also have a very nice looking mainsail cover with a generous cut that is creating windage aft.

You're also sailing in the lee of a shoreline, which is providing flat water. If the waves were coming over a longer fetch, they would be bashing against your bow, one after another, knocking the bow to leeward, and it would require more power from a mainsail to drive the stern to leeward and hold her bow into the wind. If you hadn't been sailing in smooth waters, your bimini wouldn't have provided enough power aft of the CLR to hold your bow to windward. In ideal sailing conditions, it was enough.

In ideal conditions, I have actually sailed my C25 to windward with no sails up, using only the force of the wind blowing against the hull and rigging, and was even able to tack back and forth. You don't get much power from the bare hull, but in very smooth waters, with a fairly strong wind, it's enough to drive the boat.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

islander
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Response Posted - 06/24/2019 : 13:14:39

True, As many including myself found out the C25 sails very well at anchor with no sails up.

Is it possible that the CLR is different on a swing keel vs a wing or fin. I know Dave often sailed on the headsail also and Passage is a fin. Mine's a wing.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 06/24/2019 13:20:38

Steve Milby
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Response Posted - 06/24/2019 : 14:24:59

I'm sure yacht designers have complicated formulas for deciding how to situate a keel in any given hull, and how to situate the rig and sailplan so that the rig can be properly tuned in relation to the keel, but those formulas are way beyond me, but it certainly wouldn't surprise me if there aren't some minor variances between the different keels. It would surprise me, however, if there were any really significant variances.

Whether you have a fin or wing or swing keel, the purpose of rig tuning is to bring the pressures ahead and behind the CLR into proper balance. If a wing keel boat isn't capable of pointing quite as high as a fin or swinger, I don't think it's because of differences in the rig or an imbalance between the sailplan and the CLR. It's because the wing is a slightly less efficient foil than a fin or swinger.

People who choose to buy a fin or swinger do so for different reasons than people who choose to buy a wing. For each, their reasons are valid. A wing keel is robustly constructed, has a shoal draft, is more easily trailerable and still provides very good sailing performance, but it compromises very slightly on pointing ability. If you're not a racer, a degree or two of pointing just isn't a big deal.

I have never said you can't sail on jib alone, but I know you can't do it in violation of the laws of physics. No matter how you achieve it, there has to be at least a nominal balance (not necessarily a perfect balance) between the pressures ahead of and aft of the CLR, and the combined pressures have to be sufficient to power the boat through the chop.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Peregrine
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Response Posted - 06/24/2019 : 15:55:07

quote:
Originally posted by C25BC

We had couple hours to sail the other day so we went out planning to use just the furled headsail , not something I usually do. It was blowing around 15 knots and soon went to 24 with some healthy gusts . I was furled to about 110% on my 135 genoa and kept stalling when trying to tack and had to gybe out of it a couple times, also when heading in I had the rudder hard to port on a beam reach just to maintain the heading.
Needed to keep speed over 4.5 kts to tack. Any feedback on my obvious errors ?

Somebody note the date and time! I am about to agree with Steve Milby.

First let me say I don't "jib only" but that's just me I like the routine of getting the headsail and main to work together.
And getting the two sails to work together even minimally will make it easier to come up and across, i.e. tack, the wind.
However if you just reach or go down wind and jibe while "jib only" it will work better, not best, but better.
Think of it like being under a spinnaker or a drifter in lighter winds, and dicey as the wind picks up.
IMO Best to raise the main even if reefed so that it not so much to handle.

John Gisondi
Peregrine #4762

*

Steve Milby
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Response Posted - 06/24/2019 : 16:26:12

quote:
Originally posted by Peregrine

Somebody note the date and time! I am about to agree with Steve Milby.

The date and time have been duly logged in my diary.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

C25BC
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Response Posted - 06/24/2019 : 17:00:32

Just got home and reading the day's input. Thanks to all . I prefer to use my Mainsail and jib usually, we have gone out a couple times with less wind and just the jib and haven't had any issues except it seems to follow thru more on tacks. The last time was the first time with this boat I didn't have control and couldn't figure out why. I definitely would have done better with a reefed main and jib. I have by no means have mastered the art of sailing but I'm always working on it.
Our lake is notorious for hard blowing gusty afternoon winds in the summer so it does make it interesting.

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

dasreboot
Admiral

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Response Posted - 06/25/2019 : 09:11:13

quote:
Originally posted by islander

Steve, Technically that is all true but it doesn't answer the question as to why he is having these problems and I and others don't.

fouled bottom? maybe swing keel was not all the way down moving the CLR further aft? definitely the bimini has an effect as previously mentioned.

Todd Lewis
Eowyn 87 TR/WK C25 #5656
ARWEN 84 TR/SK C25 #4031
www.mainsailsailingschool.com

Stinkpotter
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Djibouti
9076 Posts

Response Posted - 06/25/2019 : 10:11:15

We did a lot of 130-only sailing--it can be a very relaxing way to "sail to nowhere" or deal with a blustery, gusty afternoon. We rarely had difficulty tacking, and generally our helm went from weather (both sails up) to neutral (genny only). Neutral helm feels strange to me, but it was understandable...

Keep in mind that the genoa has a much lower CE than the main, so the need to reef (partially furl) it is considerably less, especially with no main up. The primary drive from the genny comes from down low, leading to this...

I'm going to speculate that if you move the sheet cars aft and unfurl the whole sail, or most of it, things will improve dramatically. As Steve points out, the CE will be further aft, creating better helm balance. Also, the top of the sail will twist off more, reducing heel so you don't feel as if you need to reef the sail. Additionally, the larger lower part of the sail will be flatter to create more drive, helping you through the tacks. And don't slam the tiller hard over to tack--move it steadily over, not past about 45 degrees, to minimize drag that slows you, and maximizes its lift that turns you. In lighter air, you can also try releasing the genoa a little later than usual to allow it to backwind for a moment, pushing the bow over--then pulling it across and sheeting just after the wind has crossed the bow. You might come almost to a stop, but you'll be stopped at the angle for the new tack, in which case sheet in just enough to fill the sail and you'll get going on a lower course--you can steer up and trim in after you get some speed back up.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 06/25/2019 10:42:23

Stinkpotter
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Djibouti
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Response Posted - 06/25/2019 : 10:28:47

One more thing: Don't keep the genny sheeted board-tight or try to sail as high as you do with both sails. Ease the sheet a little, and sail just a little lower to keep your speed up--that speed will help you though the tack. It's a beneficial compromise for doing without the mainsail.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 06/25/2019 10:30:01

Voyager
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Response Posted - 06/25/2019 : 13:32:55

I�ll have to second Dave Stinkpotter on that. This weekend we had strong NWs that were steady at 15 and gusting to 25 and the genoa was halfway furled with the tiller around 10� off center and I was at 60� to 90� to the wind (close and beam reach).
Passage only got up to 3.5kts but I was happy to be in control in that wind. I did 5.5kts on a broad reach and run down wind. Nice work if you can get it.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Allmanjoy
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Response Posted - 04/25/2020 : 18:30:33

Is there ever a time you�d want to sail with the swing keel retracted so as to move the LCR more aft? If for example you sail with just the Main sail and wanted the keel LCR more aligned with the LE?

Jay C 1985 C25 SR/SK

Steve Milby
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Response Posted - 04/25/2020 : 19:03:32

quote:
Originally posted by Allmanjoy

Is there ever a time you�d want to sail with the swing keel retracted so as to move the LCR more aft? If for example you sail with just the Main sail and wanted the keel LCR more aligned with the LE?

I think you mean the CLR (Center of Lateral Resistance of the keel). I'm not sure what you mean by the LE, perhaps the CE (Center of Effort of the sailplan).

I don't think raising the swing keel moves the CLR aft significantly, because the keel, when down, is swept back at about a 40-45 deg angle. When the keel is retracted, none of the surface of the keel moves aft. It just moves up. It does move some weight aft however. So, I don't think retracting the keel significantly changes the relationship between the CE of the sailplan and the CLR of the keel. Raising the keel also doesn't reduce the keel's lateral resistance. The keel doesn't retract into a keel trunk. It does, however, shorten the keel's lever arm, making the boat more tender.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Stinkpotter
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Djibouti
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Response Posted - 04/26/2020 : 08:45:02

quote:
Originally posted by Steve Milby

[quote]Originally posted by Allmanjoy

I don't think raising the swing keel moves the CLR aft significantly, because the keel, when down, is swept back at about a 40-45 deg angle. When the keel is retracted, none of the surface of the keel moves aft. It just moves up.

I'm not so sure about that--it's "swinging" up... The weight and lever arm parts are true, but couldn't be if the CLR wasn't also moving back. I'll mention that on the C-250 Water Ballast model, several people have reported that partially raising (swinging back) the centerboard has significantly reduced weather helm--that's all about moving the CLR aft. Fully lowered, the C-250 centerboard is practically vertical, unlike the swing keel on the C-25, and virtually all of the ballast is inside the hull, so the overall dynamics are a little different. (When the C-250 was first introduced, I suspected the centerboard was too far forward when fully lowered.) But there's an easy way to answer the question... I would try just partially retracting--maybe lifting it about 1/4 to 1/3 so you keep most of the righting force. In many ways on a sailboat, a little can do a lot.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Steve Milby
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Response Posted - 04/26/2020 : 10:28:27

Dave, don't overlook the word "significantly." IMO, unlike the C250, any effect on the CLR is nominal, especially when measured against the risk of a sudden drop of the keel if the cable snaps. Catalina has always recommended that the keel be kept down all the time.

I've never seen a racer gain anything significant by raising the keel of a C25 swinger, either to windward or downwind, although a few have tried it. In fact, I experimented with it many years ago while crewing on a friend's swinger, and up or down didn't beneficially affect our boat speed or pointing.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Allmanjoy
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Response Posted - 04/26/2020 : 12:08:51

Yes, sorry for the lack of proof reading. I didn�t know Catalina recommended the keel should always be extended. Good to know. Will it sail safely with it up? If for example you were moving through a shallow area?

Jay C 1985 C25 SR/SK

Derek Crawford
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Response Posted - 04/26/2020 : 12:17:53

That's an interesting comment Steve about any speed difference by lifting the keel a little. When we had our original C22 we found that putting 8 turns on the winch (22 turns raised it fully) increased our downwind speed by 1/2 to 2/3 of a knot. (Then the local PHRF Committee banned the raising of keels or centerboards while racing.)

Derek Crawford
Chief Measurer C25-250 2008
Previous owner of "This Side UP"
1981 C-25 TR/FK #2262 Used to have an '89 C22 #9483, "Downsized"
San Antonio, Texas

Steve Milby
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Response Posted - 04/26/2020 : 13:59:09

quote:
Originally posted by Derek Crawford

That's an interesting comment Steve about any speed difference by lifting the keel a little. When we had our original C22 we found that putting 8 turns on the winch (22 turns raised it fully) increased our downwind speed by 1/2 to 2/3 of a knot. (Then the local PHRF Committee banned the raising of keels or centerboards while racing.)

The Catalina 22 swing keel, unlike the C25's, partially retracts into the hull. When the keel is retracted, the boat's wetted surface is reduced. Wetted surface equals drag. When you reduce drag, the boat goes faster.

The S2 7.9, for example, has a lifting keel. The daggerboard lifts straight up into the cabin. That reduces wetted surface and increases boatspeed downwind.

What works for the C22 and S2 7.9 doesn't work for the C25.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Steve Milby
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Response Posted - 04/26/2020 : 16:00:06

quote:
Originally posted by Allmanjoy

I didn�t know Catalina recommended the keel should always be extended. Good to know. Will it sail safely with it up? If for example you were moving through a shallow area?

The keel should be down in high winds and heavy chop, to give the boat maximum stability. In more moderate conditions, the boat is safe with the keel up or down - with one exception. New owners often don't realize how important it is to properly maintain the keel cable and mechanism. If the keel is raised and the cable breaks, the force of the 1500 lb keel dropping can tear apart the fiberglass. If the cable breaks while the keel is down, there's no harm. Hence, the recommendation that it normally be kept down. Some people keep theirs raised in their slip, because of the shallowness of their slip, and that's ok as long as they keep the lifting mechanism in good condition.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Allmanjoy
1st Mate

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Response Posted - 04/26/2020 : 17:53:18

Ok, just replaced the entire lifting system and the 4 keel pivot bolts. Torque them to 20lbs/ft. The new hose came right up to the winch. Normally I�d be concerned with that, but the boat will be in a deep water slip and I plan to keep the he keel lowered. So There won�t be a lot of hoisting the keel.

Jay C 1985 C25 SR/SK

dmpilc
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Response Posted - 04/27/2020 : 08:08:25

The swing keel shape on the C-25 is different than the C-22. The C-25 swing keel flares out slightly toward the bottom, probably adding more weight deeper down. That could create additional turbulence if it is raised up any. I suspect, too, that raising the keel on either boat could increase keel wobble, which you do not want. I found that you do want to keep a little tension on the keel cable for 2 reasons. You get the audible speed indicator (higher pitch hum in the cable as your speed increases), and more importantly in the C-25, if your keel does hit something lifting up the keel even a little it won't hit the fiberglass keel trunk as hard dropping back down cracking the keel trunk (don't ask how I know that!).

Also, by the way, the C-22 class rules prohibit raising the keel while racing, except for after running aground! So, even if you are just club racing, if the NOR includes class rules, you must keep the keel down.

DavidP
1975 C-22 SK #5459 "Shadowfax" Fleet 52
PO of 1984 C-25 SK/TR #4142 "Recess"
Percy Priest Yacht Club, Hamilton Creek Marina, Nashville, TN

Stinkpotter
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Djibouti
9076 Posts

Response Posted - 04/27/2020 : 08:17:46

quote:
Originally posted by Allmanjoy

Will it sail safely with it up? If for example you were moving through a shallow area?

In water shallow enough for the keel to hit bottom, it might not impact the hull if the cable lets go. But as another example of what can happen, there have been reports here of lowered swing keels being pushed up by submerged objects (rock, stump, barn foundation,...?) and then dropping after the boat has passed over the object, cracking the keel trunk.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 04/27/2020 08:32:21

Allmanjoy
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Response Posted - 04/27/2020 : 09:05:04

That�s all good information.

Jay C 1985 C25 SR/SK

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