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 How often do you reach max hull speed?

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T O P I C    R E V I E W
myersge1 Posted - 11/03/2020 : 15:05:53
How often is everyone able to reach max hull speed (6.3 kts) when under sail and in what wind conditions? I've reached max hull speed only once and it was with 12 kt winds on a beam reach. I leave the boat in the lake (Alabama) year-round so it has some slime that I hope is mostly washed away each time I motor out of the marina and channel. With moderate winds (around 8 kts), I can only hit 5.0-5.2 kts on a beam reach. I know there are a lot of variables but is max hull speed pretty normal for most of you?
21   L A T E S T    R E P L I E S    (Newest First)
Lee Panza Posted - 11/09/2020 : 00:30:02
Tim: You had 10 gusting to 16 up there? Down here SFO recorded over 30kn gusting to over 35 around noon. I had a blast out there! And we got a little bit of "white stuff" falling, too: hail! You're right: it's not Summer any more.
keats Posted - 11/08/2020 : 17:35:14
Hit 6.2 kts today with the 110 jib today.

Weather was calling for winds 10 kts with gusts to 16 but it sure looked like it was dancing a bit higher with gentle white caps on the lake at times. It was a pretty cool day for Northern California and I knew that some rain clouds would be brushing by the lake, though I hoped to avoid them. They caught us near the end of the sail and I had to send the first mate below while I single handed in the rain and falling wind. Even got a little snow for a bit. I'd venture to say we're two one of few Californians who sailed in the snow today.

Tacked into a sheltered bay, dropped the sails and started to motor back to the marina. Fired up a radiant heater in the cabin to keep the mate happy.

On the way, the rain quit, the wind died out and the sun peeked through so I raised the sails loosely to dry them out. Motored into the slip and buttoned everything up, warmed up with a little red wine and headed out. It was a good Fall sail.
Steve Milby Posted - 11/08/2020 : 09:54:08
After looking at the sequence I see what you're saying, Lee. When the photo was taken, he had rounded the mark and had the jib trimmed in to closehauled. The mainsail was luffing, either because he didn't have it trimmed in yet for the new closehauled course, or because he intentionally let it luff because he knew it would only make the boat heel even more.

As between the jib and the mainsail, the mainsail is primarily responsible for heeling moment, so, when the boat begins to heel excessively, the first thing we do is to depower the mainsail by easing the traveler to leeward.

With only the jib driving the boat in the photo, it is on the borderline of heeling excessively, so, if he trimmed in the mainsail hard and got a lot of drive out of it, the boat would only have heeled more and perhaps either rounded up to windward or even auto-tacked. His best choice would be to trim in the mainsheet hard while the traveler was eased all the way to leeward, to flatten and depower the mainsail, and then bring the traveler up to windward just enough to stop the sail from flailing, while still allowing it to luff heavily. When you trim the sail in that manner, and you look at it, you'll see that most of the mainsail is being backwinded by the jib, and that only the last 12-18" of the leech are lying down smoothly and providing drive. The importance of those few inches of cloth is that they are pushing the transom to leeward and helping the boat point to windward.

The most common mistake that I see made by sailors, including experienced racing sailors who should know better, is over-trimming the mainsail in strong winds. Your goal is not to generate maximum power out of both sails at all times. The goal, in sail trimming, is to balance the pressure on the jib against the pressure on the mainsail.

A sailboat pivots around it's keel. The jib pushes the bow to leeward and the mainsail pushes the stern to leeward. The keel resists the boat's tendency to drift sideways, and translates those sideways forces into forward motion. The rudder corrects any imbalance in the pressures on the jib and mainsail, to hold the boat's desired course. If the forces on the jib and mainsail are perfectly balanced, then you won't have to use the rudder to hold the boat on course. Any time that you have to turn the rudder, you create drag which slows the boat. Whenever the sails are perfectly trimmed, and the forces on the jib and mainsail are equally balanced, the boat sails it's fastest, points it's highest and needs only the least pressure on the tiller to hold it on course.

Many experienced sailors and racers insist on bringing the boom to the centerline of the boat, even in strong winds. When you do that, you generate too much power in the mainsail. When you do that in moderate winds, you slow the boat because you have to use pressure on the tiller to hold it's course. When you do that in strong winds, you not only slow the boat, but, in an extreme case you cause the boat to round up or to auto-tack. That might be what was happening to Paul Zell in the 3 photos. In the first photo, he was sailing along with a well-trimmed jib and an over-trimmed mainsail. How can I tell that the main is over-trimmed? Because it's smooth from the luff to the leech. In that much wind the traveler should have been eased to leeward until the luff of the mainsail was backwinded by the jib and the sailcloth at the luff was lifting significantly. When the mainsail is backwinded like that, racers call it a "bubble," and that's a good thing.

In the last two photos you can see that the boat has come head-to-wind and the boat is nearly in irons. That suggests that either he was in the process of tacking, or the boat rounded up due to the over-trimmed mainsail. The mainsail was producing so much pressure pushing the stern to leeward that the rudder didn't have enough lateral resistance to keep the boat from rounding up.

How can you tell if the pressures on the mainsail and jib are in balance? You'll feel the tiller pressure lighten.
Lee Panza Posted - 11/07/2020 : 16:34:16


More about how sea state can render theoretical hull speed irrelevant and how the specific position of the jib lead cars is sometimes not terribly precise. This sequence is one of our own, Paul Zell, beating into typical SF Bay summertime conditions in one of our Club's beer can races:







BTW, if it looks like Paul was having a tough time, he corrected out to 4th place. I was hove-to under reefed main & jib to take these and the shots of the rest of our racers.

Lee Panza Posted - 11/07/2020 : 16:05:47
Steve, I had posted that photo to illustrate the sea state on a typical Summer afternoon, when theoretical hull speed is not necessarily a limit. But I found your analysis of the boat's sail trim interesting. Keep in mind that he's in the process of rounding the mark at the bottom of the downwind leg in a beer can race. As you well know, that's a point at which the trimming requirements are changing radically, and when it's this knarly proper trim at any specific moment almost becomes just a fortunate coincidence until you settle into the first upwind tack.

BTW, the rest of the sequence, if you're interested, are at:
https://panza.smugmug.com/MYSAILBOAT/Sierra-Point-Yacht-Club-Beer-Can-Races/SPYC-Beer-Can-Race-8252020

I had to stop shooting before everybody came around, because I was working my outboard so aggressively back and forth, gunning it when the prop wasn't out of the water, and I suddenly noticed that it was beginning to slide around on the bracket. At that point I put my sails back up and headed home.

Steve Milby Posted - 11/07/2020 : 10:06:00
Look at the above photo of the boat passing a mark. The boat is overpowered, but the sails are well-trimmed the way you have to trim them when overpowered. The boat is at least borderline heeling excessively.

The jib is trimmed inside the lifelines and the foot is flat. The genoa car is a few inches too far aft, and that is allowing the jib's leech to be a little too full. He could correct that by moving the genoa car forward 2-4". That would cause the jib sheet to pull a little more downward, which would flatten the leech. If he moved the genoa car too far forward, that would ease the aftward pull on the jibsheet and allow the foot of the sail to be too full. Moving the car forwards and backwards controls the shape of the sail's foot and leech. Moving it aft flattens the foot. Moving it forward flattens the leech. To depower the jib, you want the foot and leech to be equally flat.

The mainsail is luffed to the point of flailing. Thus, he's getting no drive out of the mainsail. He is undoubtedly getting arm weary from a very heavy helm. When he's pulling so hard on the tiller, that means he's dragging the rudder crossways to the water flow, and that is killing his boat speed. The extreme pressure on the sails on the windward side is causing the boat to drift to leeward more than usual. Because of his reduced speed, the keel is losing lift and contributing more to his leeward drift. Combined, this means that he's not sailing very close to the wind and it will take him longer to reach his destination.

If he furled about 12-15" of his jib, that alone would reduce the angle of heel, reduce the heavy helm, reduce the leeward drift, improve boat speed and improve pointing. If he would, in addition, tuck a single reef in the mainsail, it would improve all those conditions even more. In addition, because the mainsail would be flatter and thus depowered, he could trim in the mainsail and even get a little drive out of it.

The fellow in the photo is doing a good job of trimming his sails in the conditions, but the boat would sail better if he reduced sail area, instead of using trimming techniques to extend the useful wind range of his sails.

If you use the genoa car placement that someone else is using, how do you know that his setting is correct? If you look at your sail's foot and leech and adjust the car so that the foot and leech are equally flat, then you'll know it's right.
JanS48 Posted - 11/06/2020 : 22:10:03
According to my Raymarine gps I often get to around 7.2 to as high as 8 kts sustained. My C25 is a STD rig with a 125 jib (pulled tight). This would be in a 15~20 kt wind off-beam reach with the wind to stern but not quite a broad reach. Sea is a moderate chop sailing off of Newport harbor heading into the ocean without big swells. I'm able to do this often with many other boats as company. The ocean off of Newport harbor is a sailors dream. The C25 seems to hold it's own but many of the larger boats can sail right by me. As a point of reference my 15 hp outboard running wide open will push the boat to just 7 kts in a flat calm with a big bump to stern.
Steve Milby Posted - 11/06/2020 : 12:24:58
Think about it this way. In high winds you must depower the jib. You can either depower it by reducing it's size or flattening it's shape. How do you flatten the jib? You move the genoa cars back. How far can you move them? You can only move them back until the foot of the sail is stretched taut, i.e. with no appreciable curve. You can also only move them back and pull the sheet until the leech of the sail touches the spreader.

If the wind is blowing that hard, the far better, more seamanlike choice for a cruising sailor is to reduce sail area. The boat will sail better, and be easier for you to control and to tack.

Racing sailors generally prefer to flatten their genoas instead of reducing their size. Why? Because they seldom use roller furling jibs. Taking their big genoa down and replacing it with a smaller jib takes too much time. You have a furling jib, and in a strong blow, you can roll up a little sail area, keep the boat on it's feet and drive it to windward better than a racer who is struggling with too much sail area.

So, my advice is, when the boat becomes overpowered, roll up a little sail area instead of using sail trimming techniques to extend the useful wind range of the genoa. That's when your furler will give you an advantage over the racers.

Whether you race or not is immaterial. Racers don't always practice the best seamanship, because they can't afford to take the time to change sails. With your furler, you have the luxury of being able to roll some sail in and out as the wind puffs and lulls.
Lee Panza Posted - 11/06/2020 : 12:09:05
When asking about positioning the genoa car, remember that differently-cut sails would need different car placements for the same degree of twist-off. Furler vs. hanks could make a difference. More than that, if a sail was custom-measured on the boat by the sailmaker and cut for the type of sailing the owner said they intend it to be used for (ie. comfortable daysailing vs. racing), it could require a different lead placement than one cut to OEM specs from Catalina.

And, as you bear off you might want a little more camber along the foot, even while you continuously adjust the tension along the leach by easing or hardening the sheet; for this the car could be moved forward.

But the most important variable in genoa car placement would be the degree of heel you're willing to tolerate, at least on a temporary basis during wind surges. I just heard something funny that I'll share here (I'm sure some people will recognize the truth to this). Someone told me that when he's out with his wife they refer to the inclinometer (that little curved bubble-level that quantifies the degree of heel) as the "divorce-o-meter"

The best advice you might get on this is only a starting point, Gerry. You have to learn through experience what works best for you on your boat. An entire dimension to the enjoyment we can get from sailing is the learning experience, and the satisfaction derived from acquiring the knowledge that makes us better sailors can be a very gratifying reward.

Derek Crawford Posted - 11/06/2020 : 09:36:15
"How far back do you have your 155 genoa lead car (for twist) in winds that high?"
The car for the 155 was usually level with the stanchion that is level with the companionway. With high (20+) forecast we would move it back up to 3 holes on the track but it never got back even close to the cockpit winch. In the severe gusts 35-50 mph we would just come head to wind until it went away.
bigelowp Posted - 11/06/2020 : 07:44:12
I have gotten close over the bottom, but with current helping. I do not have a knot meter but am guessing that I have never even been close to "hull Speed" but I am also not a racer so it has not been a concern. Regarding wakes vs waves . . . . Where I sail on western Long Island Sound there is a lot of wake activity. Anyone coming out of Norwalk Ct heading west will cut through the Sheffield Islands, which have earned the nickname by many of the Wake Islands! On weekends and holidays there is always a parade of boats, mostly larger power boats, speeding through the relatively narrow channel creating continual wakes. When winds are blowing from the east or northwest the chop caused by the natural waves crossing with the wakes can be interesting. On a weekday, with little power boat activity sailing is easy, on weekends you must have patience or motor out of the area.
Voyager Posted - 11/06/2020 : 06:51:15
Tim, we have a lake in CT with a “Ski Club”. I used to kayak and fish there. My favorite waves were the ones when the ski boat would encircle me and create coincident waves coming from all directions. I definitely used my paddle brace to get through that!
myersge1 Posted - 11/06/2020 : 05:37:03
How far back do you have your 155 genoa lead car (for twist) in winds that high? I have a 155 genoa on a furler and have the car 8-10" aft of the wench in strong winds. Much further aft than that and it rubs on the railing upright and gunwale/coaming.
Derek Crawford Posted - 11/05/2020 : 08:55:09
I've hit over 10 knots on a couple of occasions. Both times a front came through as we were racing and with a 155% and a full main up it was a little interesting. Lake sailing can get hairy at times - I've had it go from 20 to 35 instantaneously - we were 100 yards from finishing. After crossing the line we dropped the sails and motored - going one whole knot on full throttle.
Lee Panza Posted - 11/05/2020 : 00:49:37
Keep in mind that the calculated figure is THEORETICAL maximum hull speed. If a hull of such-and-such length is pulled through flat water at a particular speed, the bow and stern wave align with the hull ends and the hull drops down into the trough between them. Trying to exceed that speed means constantly climbing up the back of the bow wave, which requires a lot more power.

That figure is only an abstraction, however. Actual conditions are usually more complex. On San Francisco Bay in the middle of Summer we often get afternoon winds in the low-to-mid twenties, and sometimes higher. They kick up a nasty chop that starts to aggregate into coherent rollers of three feet or more (especially a few miles out down by SFO). At times I've seen brief bursts well in excess of 6 and a half (and I've carefully calibrated my knotmeter myself). Sailing a deep reach in mid-twenties sustained (with higher gusts), running at a diagonal on the order of 30 to 40 degrees off DDW so I'm cutting across the faces instead of just surfing them at their own speed, I've seen mid-sevens. Of course, under those conditions I'm not paying much attention to that gauge because just managing the boat takes a lot of focus. Definitely an E-ticket ride!



(this was a friend of mine going the other way)


But the point is, when the surrounding water is in a wave pattern that overrides the effect of the hull through the water, that theoretical hull speed limitation no longer governs.

keats Posted - 11/04/2020 : 21:01:51
Bruce, the waves we do have are generally man-made. Don't know if you're ever been around a wake boat but they are made to put up a wall of water.
Voyager Posted - 11/04/2020 : 18:24:25
Tim, I believe that your experience reflects what Steve Milby said, that if you have relatively flat seas, and persistent strong winds, you can sail to weather very efficiently. You’ll even enjoy stronger apparent winds due to the combination of your forward speed and the wind coming from ahead of your boat.
Lakes generally have a lot less fetch than large bays, sounds or the ocean. I can reliably predict short chop beginning about 2-3 hours after the start of strong winds on Long Island Sound. Under certain conditions however, e.g.: offshore breezes, I can get going pretty fast because of the absence of waves breaking on my bow.
I’d guess lake sailers, in general, would see less chop than me.
myersge1 Posted - 11/04/2020 : 17:21:49
20-25kt winds are a little much for me. My marina is on the lake's edge and doesn't provide a lot of wind break so getting in and out of the slip is challenging in tight quarters with winds that high. However, it sounds like 5.2kts on a beam reach with moderate winds is in the ballpark.
keats Posted - 11/03/2020 : 20:06:00
I think it depends a lot on how much sail you can put up. I've hit 6.3 pretty regularly in 12-15 kts on our mountain lake, beam reach and a bit higher. I've got a tall rig and a 150% hank on genoa that really powers the boat. My sails are not new but I keep the bottom clean.
Steve Milby Posted - 11/03/2020 : 18:51:49
My C25 didn't have a knotmeter, but I always kept the bottom clean, the rig tuned and it had good racing sails, and I'm sure it hit or briefly exceeded hull speed from time-to-time on a beam reach in 20-25 kt. winds. I doubt that it ever reached hull speed when closehauled. A well maintained C25 should be able to reach or exceed hull speed in those conditions.

By comparison, my C&C 35 Landfall has a hull speed of 6.93 kts. On one occasion, it made between 9-10 kts. continuously for three hours (measured by knotmeter). It was on a beam reach in 27-30 kt. winds sailing south along the Chesapeake Bay's western (windward) shore in smooth water. The key to being able to continuously exceed hull speed is to have strong enough winds in smooth water to drive the boat over it's own bow wave. Once there, the strong wind must be consistent enough to keep it ahead of it's own bow wave. If the wind lulls, the boat will lose speed and drop back behind it's bow wave, and it will take a strong puff to drive it over it's bow wave again. On that day, for three hours the wind didn't lull enough to cause the boat to drop behind it's bow wave.

Many people believe it's only possible to exceed hull speed in a conventional monohull for brief periods, while surfing down the face of a wave. That's the more likely way to exceed hull speed, but it can be done for extended periods of time in ideal conditions. Nevertheless, not many C25 sailors would sail their boats in 25-30 kt. winds.
Voyager Posted - 11/03/2020 : 16:25:56
Almost never. Whether it’s due to slime on the hull or my old sails, I never go hull speed through the water on my knot meter. I can easily get to 5.2 kts, however, in lively breezes or using the engine.
Now, I can exceed hull speed because I sail in tidal waters. One day I went about 70 nm in 10 hrs by catching the flood tide at slack in Mystic CT at 0600 and sailing west to Stratford by 1600. I hit 8.0 kts SOG for several hours motorsailing until 1400, then the current reversed, making my last 2 hours a lot slower.

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