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Sailing on Genoa

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Initially Posted - 02/07/2009 : 18:28:35

It was 70º with wind around 10 kts. and the bay was smooth. Out of pure laziness (just day sailing with no destination), we sailed with just he 150 up. I had never checked, but in 7 - 10 kts. we easily tacked through 90º (probably more like 88º). That was on my compass and maintaining good speed and no struggling to maintain the edge without pinching. Hopefully this will help answer the the newer folks questions about genoa vs main with one sail up.

Dave B. aboard Pearl
1982 TR/SK/Trad. #3399
Lake Erie/Florida Panhandle

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Dave5041
Former Mainsheet Editor

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Response Posted - 02/07/2009 : 18:34:45

P.S. By good speed, I mean the cable was humming, sometimes very loudly, and that means 4 - 5 kts. My knotmeter was fouled, and I didn't have a gps with me for precise numbers

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bigelowp
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Response Posted - 02/07/2009 : 19:47:36

On western Long Island Sound I have often sailed with just the 135 genny up with great success. It all depends on your location, wind speed and mind set -- but one sail sailing can be very relaxing . . .

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Dave Bristle
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Djibouti
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Response Posted - 02/07/2009 : 22:43:35

I've preached this sermon many times before, but besides performing surprisingly well, if you're out on a gusty, blustery day, the genoa has so much more of its area so much lower that the heeling forces of a gust are almost trivial. With our 130 alone in 15 knots with gusts to 25, we comfortably cruised around, with gusts maybe pushing us to 15 degrees (if that)--staying close enough to hull speed to feel very satisfied. My late Admiral liked to have the boat moving--not lazing along--and she was happy. I liked that I could pull one string and be sailing, and then pull another and be done!

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Walt Oler
1st Mate

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USA
44 Posts

Response Posted - 02/08/2009 : 06:52:02

We have a full batten main and 110 jib for our 82 C25 TR/FK. Recently, we were forced to tack into the Corpus Christi municipal marina in 16-18 kt winds because of motor problems. Initially, we tried to sail on the jib alone because it was roller furled and easiest to get back up quickly. The lee helm was so severe, we found it impossible to hold the course. We gave it up and went downwind back out into Corpus Christi Bay to raise and reef the main(2nd reef point) and furl the jib. Things worked out after that.

I guess the difference for us was that the 110 jib has a center of pressure farther forward than a 150 genoa which caused the boat to be badly out of balance.

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OLarryR
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USA
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Response Posted - 02/08/2009 : 07:33:48

I have sailed occasionally with just the Genoa. I have to agree with Peter that sailing with the Genoa alone and enjoying it has to do with a number of factors. For many, if you sail in open waters, there is probably little thought as to what would make it unsatisfactory sailing with just the Genoa. But river sailing is one of those places where the factors sometimes add up to sailing with both sails. Depending on the combination of wind, direction, current, tide and most important, the degree that tacking is necessary, just going alone with the Genoa is sometimes a chore. This is because when changing tacks, I have experienced where the Genoa momentarily pulls the boat falling off the tack and then takes a few seconds or more to recover back to my desired tack. By that time and especially in a somewhat narrow channel, the falling off the tack and subsequent recovery is one of losing efficiency trying to head upwind and in many cases, against tide.

However, when in wider areas of the river, going downwind or on a broad reach, I will sometimes just go with the Genoa. It's easy ! No reason to even take the main sail cover off or have to put it back on. The furling rig Genoa can be furled/unfurled from the cockpit. I also have just sailed with the Main sail and that has it's benefits as well. That's sometimes for those days when I just feel like relaxing and not messing with pulling the Genoa sheets from side to side. Just go out with the main and coast along with little attention given to anything.....just have to watch out I do not doze off while coasting along !

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Dave5041
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3758 Posts

Response Posted - 02/08/2009 : 08:23:36

Subjectively it has always felt like Pearl points higher with both sails and theoretically it should be true, but I had never actually measured my tacking angles. I consider tacking through 90º to be acceptable performance for my relaxed form of sailing, except when rarely trying desperately to reach a windward destination on a longer cruise. Today's weather will be similar to yesterday's (I love being able to head south for the winter), so I may try it again today with the main and with full canvas. I know she's a pig on main only in light to medium air, but newbies frequently ask this question and I thought I would back up my subjective notion with data from one fairly standardized set of conditions. I'm sure that you racers know your angles for most conditions, but the more casual of us don't usually investigate this kind of thing with precision.

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Steve Milby
Past Commodore

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Response Posted - 02/08/2009 : 08:51:15

A sailboat must have some sail area aft of its center of lateral resistance in order to sail to windward. In other words, there should be some sail area forward of the boat's center of lateral resistance, but there must be some sail area aft of it. If all the sail area is forward of the center of lateral resistance, it becomes difficult or impossible to tack the boat and get it to sail to windward on the other tack. When all the sail area is forward of the center of lateral resistance, it tends strongly to pull the bow of the boat downwind.

But, that having been said, a 155% genoa is an overlapping sail. Part of the sail reaches aft of the boat's center of lateral resistance, and that part of the sail will help drive the boat to windward, just as a mainsail will do.

If, however, your big headsail is a 130, or if you roll up some of your 155, it will not have as much sail area aft of the center of lateral resistance, and it will generally be more difficult to sail to windward. If your headsail is a 110% or smaller, it will become increasingly difficult, or impossible, to tack the boat to windward.

In short, sailing to windward on headsail alone works reasonably well with a big overlapping genoa, but not so well as the size of the jib diminishes.

Edited by - Steve Milby on 02/08/2009 12:34:31

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 02/08/2009 : 09:37:57

Sometime ago, I wrote down a few pages of notes while experimenting one day with sailing under headsail and main, main only, and genoa only. I noted such things as pointing ability, speed, tacking ease, downwind performance,...etc, but alas, those notes are nowhere to be found. I can say that sailing performance under a 135 genoa alone is remarkably good on all points of sail and is without question, many times better than under main alone.

When conditions are iffy, I'll just motor out to open water sans sails to see what the wind/sea conditions are like. If it looks like I'll just be battling the conditions, I'll simply turn around and head back to port. If it looks somewhat do-able, I'll just pop the furled genoa. If conditions worsen, I'll simply reel in the genoa and head back to port. If conditions improve, I'll raise the main.

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sanibelle
Deckhand

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USA
22 Posts

Response Posted - 02/08/2009 : 11:36:31

Dave, Steve,

Where is the center of effort (lateral resistance) on my 1980 FK tall rig?

Joe Russo

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 02/08/2009 : 12:05:49

The "center of effort" (CE) is determined by the combination of sails you have up. It is also affected slightly by the hull--it is the geometric center of the forces on the entire rig created by the wind. With two sails, if you estimate where the CE is for each sail, the total CE is on a line between the two individual CEs, slightly toward that of the larger or more powerful sail (which is generally the foresail on a C-25).

The "center of lateral resistance" is based on the underwater characteristics of the boat--especially the keel. It is the center of all forces that resist the boat being pushed sideways by the wind, and translate those forces to forward motion. If you look at a profile drawing of the C-25 fin keel boat (below), you can guess about where that would be. (The bow tends to provide more lateral resistance than the stern, so the CLR is probably somewhat forward of the geometric center of the keel).

In simple terms, if the CE is forward of the CLR, you will get lee helm--the boat will try to turn away from the wind. If the CE is aft of the CLR, you get weather helm--what you want to a small degree. The sails are the big variable. Walt is probably right that his 110 had a CE too far forward. A 135 would be better (from my experience), but also the trim of the 110 could be a factor--he might have had it too flat for the wind he was in. My experience on genny alone is that keeping it a little on the full side with the cars forward a little ("powered up") gives better drive, and better drive gives better helm control and better acceleration out of a tack.

Edited by - Dave Bristle on 02/08/2009 12:21:27

Dave Bristle
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Djibouti
10005 Posts

Response Posted - 02/08/2009 : 12:31:15

PS: Looking at the drawing (which appears to show a 155), it seems the CE is forward of the CLR--just an eyeball estimate. So you would expect noticeable lee helm on a genny alone, especially a smaller one. I experienced virtually neutral helm on my 130 alone. So what's going on??

Arlyn Stewart and I have discussed (and debated) the physics of the hull form, rudder, and keel when moving through the water... I suspect that these things interact to generate some weather-helm forces that counteract the static CLR (as if the boat were standing still) to neutralize my helm. All I know is the result.

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Steve Milby
Past Commodore

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Response Posted - 02/08/2009 : 12:36:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave BristleSteve: I assume you meant "center of lateral resistance" (CLR).

<hr height="1" noshade id="quote"></blockquote id="quote">

Ooops! Right Dave. I corrected my post accordingly. Thanks!

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Steve Milby
Past Commodore

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Response Posted - 02/08/2009 : 12:55:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by sanibelle
 Dave, Steve,

Where is the center of effort (lateral resistance) on my 1980 FK tall rig?

Joe Russo
<hr height="1" noshade id="quote"></blockquote id="quote"> Dave explained it very well. I hope I didn't confuse you, Joe.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 02/08/2009 : 15:23:19

I just thought of another factor that probably places the effective CE further aft on a headsail than the geometric center of that sail--the sail's shape under way. The forward section of the sail, along the luff, will be angled more parallel to the wind, while the aft section, along the leach, will feel more pressure. So the true CE of that 155 (alone) under way might actually be slightly aft of the mast, although the geometric area doesn't suggest that.

Now, if we hypothesize that the underwater part of the bow has more lateral resistance than the stern, we can imagine that the CLR is somewhat forward of the center of the keel, putting the CLR and CE very close on the horizontal scale (which is what matters). Where are these two "points" really? That's a hard question... You could determine a CLR by finding the location on the hull where pushing the boat sideways does not cause it to swing, bow out or stern out. But under way, the dynamics under water are much more complicated. My observations from actual sailing tells me the answers are not determined by simple geometry, nor are they "intuitively obvious to the casual observer" (as math professors have said many times).

Sorry for dragging this out--I find it to be interesting, especially when I (and many of us) can't actually go out and do this stuff!

Edited by - Dave Bristle on 02/08/2009 15:36:03

Steve Milby
Past Commodore

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Response Posted - 02/08/2009 : 15:57:20

I'm not sure that it's necessary for the CE of an overlapping headsail to be aft of the CLR in order for that headsail to provide some assistance to the boat in sailing to windward. The purpose of the mainsail is to kick the stern of the boat to leeward, and to partially counteract the force of the wind on the jib, which is trying to push the bow to leeward. All that is needed is for a little sail area, aft of the CLR, to counteract the force exerted forward of the CLR, and to lever the stern to leeward. I think the aft-most part of the jib's leech is all that's necessary to serve that purpose. The more balanced the relationship is between the forces ahead of and aft of the CLR, the better the boat will sail to windward, but even if the relationship is somewhat out of balance, the boat can still sail reasonably well.

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Merrick
Navigator

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USA
192 Posts

Response Posted - 02/08/2009 : 17:39:42

After reading all this I'm anxious to get out and try the genoa alone. If we can get reasonable speed and less heel the admiral (and thus I) will be happy.
Looking at the underwater configurations, it's also interesting how a deep keel will effect the forces differently from a longer shoal draft or wing keel. THe C25 keel widths arent' that different, except the swing which is deeper and narrower. So which should point better, irregardless of turning capablilty, a deep narrow keel or a shallow wider shoal type keel. Is it simply the most lateral resistance points better?

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/08/2009 : 21:59:48

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Merrick
 So which should point better, irregardless of turning capablilty, a deep narrow keel or a shallow wider shoal type keel. Is it simply the most lateral resistance points better?<hr height="1" noshade id="quote"></blockquote id="quote">Steve... There's been plenty of debate on this (you can "Search" for threads"), but I'll summarize my conclusions:

The wing keel is a compromise in windward performance for trailerability, replacing the swing keel which turned out to be problematic for people in salt water or who didn't maintain its lifting system religiously.

The fin keel was the original "leave-it-in-the-water" configuration, and is considered by many (including me) to be the best for non-trailer-sailors who also aren't worried about a 4' draft (which is pretty shallow for a cruising keelboat).

The swing keel, with its greater depth (although slightly less weight), might be the best performer to windward. But that comes at a cost of maintenance and the risk of hull damage and even sinking if the keel is raised and the cable or its fittings let go. Those risks appear to be why Catalina replaced the swinger with the wing toward the end of the production run.

A deeper keel has the advantage of having surface further below the turbulence created by the hull. It also creates a longer lever-arm for whatever ballast it contains. The C-25's fin has 1900 lbs. of ballast, while the swing has 1500 with a 1' longer lever-arm. The wing, with 1750#, has more of that weight concentrated at the bottom of the keel (the wings), so it's lever arm is probably comparable, but its lateral resistance and therefore windward pointing ability is probably a little less than the other two (but not much). Jim Baumgart's experience (SR/FK) sailing with Gary Norgan (TR/WK) seems to support that. Gary has an advantage in light air, with his taller rig, and Jim can point higher in heavier air with his deeper keel.

The bottom line is they all sail great--as well or better than any cruiser in their size range. In a "one-design" competition, the swing might have a slight slight advantage, but I personally was very happy with my fin for my purposes.

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Steve Milby
Past Commodore

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USA
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Response Posted - 02/09/2009 : 07:05:40

There's a very good article on keel design at the following web address:

http://www.vacantisw.com/keel%20design.htm

In the first paragraph, the author says:

"In the design of a sailboat keel, it is not possible simply to write down all the optimum proportions and draw the keel accordingly. A designer must cope with several limitations, and he or she is not always free to use those optimum values. The greatest concerns, in addition to generating side force, are (1) to provide sufficient volume for ballast, (2) to locate properly the center of lateral resistance to balance the helm, and (3) to position the ballast in the keel to achieve level trim fore and aft. Also, the area of the keel must be just large enough to balance sail forces and must provide low ballast placement for good stability. Often, rating rules, cruising requirements, or moorage depth limitations limit maximum draft of the keel."

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millermg
Navigator

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Response Posted - 02/09/2009 : 09:44:26

I sail w/ 155 genoa alone once and a while- and my experience has been that you can point much better in heavy air than light. We've all experienced the increase in weather helm that occurs as wind speed and power increase. If I get out in 10 knots or more I seem to have enough weather helm and the flow on the foils is adequate under genoa alone to point somewhat decently. Pointing is best checked with the gps- with lee helm, the compass may read a good angle, but the bearing may not be near as good with the boat slipping sideways.

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Dave5041
Former Mainsheet Editor

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Response Posted - 02/09/2009 : 19:16:09

As in heading and CMG. Having both is helpful in determining how to point for optimum windward DMG

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sanibelle
Deckhand

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USA
22 Posts

Response Posted - 02/18/2009 : 16:16:44

Thanks everyone for your expertise. I'm vacationing on Sanibel Island and haven't had much chance to check in for a while. I'm anxious to try some experiments with the sails when we're back in the water, come May.

Joe Russo

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Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
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