centers and sails

[Mike C]

apart from the obvious of having less driving power and speed, if you shorten the sail do the centers of effort stay in the same place,

example, in the case of reefing four feet on the main and four feet of the jib.

[Didereaux]

The CE does not remain in its designed location, it shouldn'e move far, but it does move with the reefing.

First point is you would rarely if ever(except prior to leaving the berth) ever reef both sails at the same time. The most common sequence would be: first the main, then shorten the jib, main again, then jib etc.

Your center of effort would by fine tuned by trimming, generally hardening up with sheet, vang, cunningham etc. You shouldn't experience large helm either way, if you do your trim is out of whack.

Just my opinion, of course. heh

g'Luk

[rtbates]

As you reef the CE moves down closer to the CLR. This reduces the rigs leverage and hence helps keep you OFF your ear. As far as slower, not really. The fastest I've ever been in our 25D has always been when heavily reefed. All time record is 7.5 knts with the headsail only reefed to about 90%. Winds around 40. This past weekend we had 6.8-7.2 kts with a 2nd reef in main and the genoa reefed to about 110%. Winds around 30. At these wind speeds move sail just drives the hull over and you end up spilling off more wind than you use for forward drive. Reducing sailarea helps keep you upright where the wind force can be transferred to forward drive

[Didereaux]

achhhh...this is perilously close to gag, yech! racing stuff!

As I said the CE does move, and further it should NOT move much with each reef because if it does you produce too much helm one way or the other. Proper reef points should be just within the range of the amount of trim available.

Only in that way can the boat be managed as the conditions worsen.

As for amount of sail and speed, the sail area can be a stout handkerchief in a storm and reach top speed(whatever that may be).

Another point is that the movement of the CE fore and aft is more critical than the movement up or down, it determines helm.

One last note, it's the apparent wind(the change) in heavy conditions that can do you damage, not the real wind(well excepting hurricanes of course. Slamming into a wave while running causes you to slow, that increases the apparent wind and it's resulting higher force. That little factoid has done in more than one 'speedo' wearing sailor. ;)

..or that's the way I ken the thing anyways.
g'Luk

[John Vigor]

apart from the obvious of having less driving power and speed, if you shorten the sail do the centers of effort stay in the same place, example, in the case of reefing four feet on the main and four feet of the jib.

Mike:

Things are rarely obvious in sailboats. Shortening sail does not necessarily produce less driving power because the increased wind speed on a smaller area of canvas will give you the same power as a slower wind on more canvas. As the wind speed doubles, the power produced on a fixed area of sail goes up four times.

The center of effort (CE) of a sail has three basic components, vertical, horizontal, and sideways. If you can imagine a square rigger with three sails of equal area on one mast, and the same distance apart, you could reef by stowing the top sail and the bottom sail, leaving the center sail alone. In this case, neither the horizontal nor the vertical center of effort of the combined sailplan would be altered.

But if you reef a Bermudan mainsail by lowering it partially and securing the surplus canvas in the foot, you will obviously bring down the center of effort, also. If this results in less heeling, the boat's weather helm will be reduced because the center of effort has moved sideways--inboard--and no longer has the same leverage it had before, working around the hull's center of lateral resistance (CLR), to turn the aft end of the boat away from the wind.

Lowering a Bermuda mainsail will also move the center of effort forward quite substantially. If you're suffering from heavy weather helm in a blow, reefing the mainsail will make the most difference and restore maneuverability. You actually get a double whammy by reefing the main: the center of effort moves forward and also inboard, both of which reduce weather helm.

But you don't always start by reefing the mainsail. For example, an overlapping genoa may have quite a lot of area aft of the center of lateral resistance, and that increases weather helm in exactly the same way as mainsail area does. So when the wind gradually starts increasing it's often a good idea to start rolling up some of the genoa first if you have roller reefing.

When your genoa has been reduced to 100 percent of the fore triangle, you're basically in the situation the naval architect had in mind when he started his calculations for CLR and CE. He's envisaging you in about 10 to 15 knots of wind.

Any more than that, and it's time to reef the main. If you're still dipping the gunwale after that, reef the main some more. After that, it's time to change the 100 percent jib to a storm jib, or roll up the genny to that size.

Now you've got a double-reefed main and a storm jib, and if the wind is still increasing your next move depends on whether safety lies to windward or leeward, what the tide is doing, the state of the sea, and whether your engine will start or not.

You can douse the jib and triple reef the main, if you have a third row of reef points, and make very slow progress to windward in reasonably calm seas, or heave to in large seas. But some boats will do better with a storm jib only in very heavy winds, even to weather.

If your destination lies to leeward, or you must run for safety reasons, get the mainsail down and use the storm jib alone for reaching and running.

The center of effort of a triangular foresail will move down and forward, as it does on the mainsail, if your sail is hanked onto the stay. If it rolls up around the stay, it will not as effective as moving the center of effort down, so it will not reduce heeling as much. But, in either case, after it has reached the size of 100-percent of the fore triangle, the effect in reducing weather helm is not as great as that of reefing the mainsail. Obviously, the more area you can fly from the end of a long bowsprit, the greater the effect of reducing weather helm. But it's not practical to do that in heavy weather of course. Most cutters will reduce foresails from forward aft, and have to rely on heavily reefed mainsails to restore balance.

But if you're sailing a CD25 I don't think you have to worry about that.

John Vigor
CD27 "Sangoma"
Bellingham, WA

[Mike C]

"OK now I can tell you rest of the story"

I have found a CD ketch (my dream to own a 30 CD ketch ) its located in lower islands, that is below Bahamas. Storm damaged, the bottom foot feet of the main mast badly buckled and would have to be cut off, the mizzen is history (only the rigging remains, stolen by another boat looking for a mast). The engine is totalled. So I would have a reefed main and a reefed jib to use on the way home. over a thousand miles. Time is not important , I have more time than money.

My question was relating to bringing the boat back to the big PX for repairs. so it would be a slow trip but an interesting one. I want the boat and have time and money to fix it HERE state side but not down there,




If your destination lies to leeward, or you must run for safety reasons, get the mainsail down and use the storm jib alone for reaching and running.

The center of effort of a triangular foresail will move down and forward, as it does on the mainsail, if your sail is hanked onto the stay. If it rolls up around the stay, it will not as effective as moving the
John Vigor
CD27 "Sangoma"
Bellingham, WA[/quote]

[Didereaux]

John>"Most cutters will reduce foresails from forward aft, and have to rely on heavily reefed mainsails to restore balance.
But if you're sailing a CD25 I don't think you have to worry about that."


You are right., in fact that additional 'load' up front adds to stability of the CD-25 because of it's inherent 'lightness' up there.

...or so it has seemed to me.

[Dick Barthel]

Good job of explaining gents.

Dick

Everything should be made as simple as possible but not simpler. Einstein

[Didereaux]

Let's see first at this season you are running into fairly regular contrary winds, sometimes quite heavy ones as those 'northers' blow by every 4-5 days. Next you add the contrary current in the Straights. And you can bet the farm just ass soon as you get into the Straight the wind will shift and blow bigtime from the east.

All in all a most difficult run short-sailed. I take it you have crew committed to such a undertaking? My uneducated, ill-informed guess is that at best it will take 14-17 days - using your guestimate of a thousand or so miles.


If you do decide to attempt this PM me, okay.

[John Vigor]

Mike: I think your priority should be to keep the mast at full length by supporting it upward from the deck somehow for the four feet you're going to cut off.

It will save you a tremendous amount of time and work if you think about it, and you'll have a full suit of sails to get you back home.

I'm sure there are more practical members of this board who could advise you about how to support the mast with four feet cut off the bottom. I don't know if yours is deck-stepped or keel-stepped, but there must be a way. I'm thinking of a wooden extension, or a simple metal fabrication that you could make here and take with you.

C'mon, guys, bend your minds to this jury-rig problem. An extra-tall tabernacle, perhaps, if it's deck-stepped. A few feet of extra-large aluminum tube that the new mast-end can be slipped into and bolted through, maybe? It only has to get the boat home, it's not intended to be a permanent fixture. There has to be a way to get this CD back where she belongs.

But first, Mike, let us know if she's deck-stepped or keel-stepped, and if four feet is actually the amount you'd cut off the bottom of the mast.

John V.

[Oswego John]

John V, Mike, et al

I don't have all the info, but from what I have read, I wouldn't cut anything at all. I think that I would keep the mast stepped as normal, straighten it as much as possible and heliarc aluminum splints to the damaged mast in order to keep it well stepped and at full height.

Good luck,
O J

[Andy Denmark]

n/m
________
Jaguar Mark Viii History

[mike feeney]

John's explanation is succinct and easily understandable.
The issue of getting this baby home is a bit more difficult. We did something similar and almost as adventurous. We bought our CD30K last Thanksgiving and sailed over the holiday (5 days) from Oyster Bay L.I. to Portland Me.
After the Cape Cod canal we had no motor. Although we had a bit of morning ice, we were blessed with strong following winds for all but parts of the first and last day.

I might spend more time putting a mizzen together. In addition to holding the mainmast up ( look up how the triatic is rigged ) if you have the mizzen you will find that the boat is well balanced when sailing with just jib n' jigger.

As to the mainmast... consider cutting out the offending section and then fitting the remaining mast parts over an under sized mast section long enough to be inserted 18"-24" . Pop rivet them together and head north. This style of repair works best with a tapered mast found on many small racing boats. In their case you merely find another wrecked mast and cut the splice section from a point slightly higher than (narrower ) the wrecked section of the mast to be repaired. The fit is then tight and strong.

Depending on where the problem is, you may also have an issue with sail slides and even the boom fitting.

Now that I've thought about it, I think our sail home was a walk in the park compared with your trip. Sooner or later you need dependable spars and rigging. You can perform the labor by yourself here or there so why not buy the hardware there and do it right and have a safe sail back?

[Didereaux]

Yves Gelinas dismasted at the Chathams. Broke at the spreaders. the way he fixed it was fabricated a collar out of (apparently) an extrusion identical to the mast, can't remember if it was an oversize piece or that he just split the piece, (probably was a split piecce as that would maintain the track)whatever, he slid it over the one end and slid the other section of the mast into that(it was tight as I remember he used his winch to pull the two halves together. He smeared it up with adhesive prior to fitting the pieces. Then riveted or scewed them together and proceeded to finish his circumnavigation.

It's in his video, maybe someone has one they can loan you to look at. He sailed an Alberg 30 almost identical to what you are going after.

g'Luk

[Mitch F]

Mike - Where there is a will there is a way.

I can't believe I'm saying this but you could get her home the ugly way: Bolt a long shaft outboard on the stern, load up 15 or 20 jerry cans of gas and go for it. Use the shortened mast and hope the wind is behind you. Hopefully the standing rigging on the main mast is fitted with staylocks or some shortenable standing rigging, otherwise setting up a seaworthy jury rig could be costly.

Without a mizzen set the 30k will sail downwind very well but going to windward is a chore. With the center of effort so far forward the bow is forever being blown off the wind, requiring a whole lot of steering which is tedious and tiring. Without an engine you won't be able to run an autopilot, even if you have one, because you won't be able to charge your batteries sufficiently. You will need several capable and optimistic crew to hand steer 1000 miles.

Many 30k jibs do not go to the masthead so you may not have a problem there, but I'm worried about the small size of your main. The 30k stands up to quite a breeze and often won't ask to be reefed until 20 knots or so. If the breeze were light you would be wishing for more sail area than a 100% jib, reefed main and no mizzen. However, if the boat has a spinnaker it should roughly fit even if the mast is 4' short.

Though the noise would make you go mad by the end of the trip you might look into the outboard idea. Figure out the gas mileage and how many gallons you would need to go the distance. Bear in mind, however, that this rig would make your life a living hell in heavy weather. It would be an unpardonable sin to leave an ugly outboard bracket on such a beautiful boat so your first priority upon arrival in the states would be to remove the engine.

I couldn't in good conscience recommend such a trip, but if you made it you would have a heck of a story to tell. Good Luck.