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Old 25-07-2012, 06:53   #46
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Re: Slamming main in calms

Now that I've digested this a bit.......thanks, I'll give it a go next time. It certainly can't make it any worse!!
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Old 25-07-2012, 06:53   #47
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Re: Slamming main in calms

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Originally Posted by Sulaire View Post
Hi, thanks

The boom is wound in to midships and does not move in the swell, but the sail is fully battened and even though i tighten everything up ( outhall etc), the main still has a belly that flicks from side to side causing this slamming. Tried a preventer with the boom out to one side slightly, but same result, tried taking in a feef or two, same result.

Tried most things and put it down as just one of tose things...., but on a long passage the other day I sat looking at the rig trying to figure out a cure with no luck and wondered if anyone had a solution. I have a feeling it is just all part of the enjoyment of sailing!!! In which case i will survive ( not sure about the rig though! ).

C.

Do you have a Cunningham? You should be able to take the belly out of your sail. Is it stretched out, or is maybe the leech too long? Maybe it needs to be recut.
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Old 25-07-2012, 06:54   #48
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Re: Slamming main in calms

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Originally Posted by Rakuflames View Post
Do you have a Cunningham? You should be able to take the belly out of your sail. Is it stretched out, or is maybe the leech too long? Maybe it needs to be recut.

Oh yeah -- you didn't mention -- did you tighten up the boom vang?
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Old 25-07-2012, 06:55   #49
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Re: Slamming main in calms

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Originally Posted by TOM View Post
What i would be very interested in knowing is how this effects CATAMARANS do they have the same problem or not.
Oh man, I was so holding my tongue on this thread - but since you asked...

This is not much of a problem on catamarans. First, we don't roll much so the sail doesn't slat and bang often. Usually, just pulling it in tight stops all the slatting in all but large beam seas. Second, the sail isn't needed to provide roll stability like on a mono (we use our auxiliary hull for that), so dropping the sail completely is a viable option if the beam seas are so large as to cause slatting.

Any seas not directly on the beam are hardly noticeable on a catamaran.

Mark
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Old 25-07-2012, 12:02   #50
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Re: Slamming main in calms

Colemj,
Thanks for the clarification. I can understand that a cat wouldn't have the same problems with roll and the main could come down.
kind regards,
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Old 25-07-2012, 12:35   #51
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Re: Slamming main in calms

Just drop the main and leave the gennie and/or staysail(s) up with a bungee tied up on the sheet..
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Old 25-07-2012, 12:52   #52
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You mentioned that you have a fully battened main...

Every time it slats you must visualize little dollar signs flapping off into the horizon. There is no sail adjustment you can make to minimize the damage to the batten pockets and sail when a sail of this type slats. I have one as well.

The only option, if you dont choose to buy sails very often is to douse the main. Reefing will help but the sail still exposed will still slat and wear and the reefing cringles will wear as well.

Once the main is down you can use your headsail to minimize the swinging heel.

If you have a furler then furl your headsail till the clew is just fore of the mast and use both sheets to hold the sail in the centerline of the hull. If you dont have a furler then choose the largest headsail that you have that has a clew forward of theast ie: leas than 100%.

Thats all you can do other than do as others have said and sail with amd outrigger of some sort to dampen you swing, which i have never seen on a cruising sailboat by the way...
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Old 25-07-2012, 13:38   #53
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Re: Slamming main in calms

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Originally Posted by foolishsailor View Post
You mentioned that you have a fully battened main...

Every time it slats you must visualize little dollar signs flapping off into the horizon. There is no sail adjustment you can make to minimize the damage to the batten pockets and sail when a sail of this type slats. I have one as well.
100%. I don't have any empirical data to back this up but I think slamming the main around in a calm generates more wear and damage than sailing in high winds.

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Once the main is down you can use your headsail to minimize the swinging heel.

If you have a furler then furl your headsail till the clew is just fore of the mast and use both sheets to hold the sail in the centerline of the hull. If you dont have a furler then choose the largest headsail that you have that has a clew forward of theast ie: leas than 100%.
Way better that using the main, even reefed but I am very intrigued by the suggestion from gjordan for hoisting a storm main high up the mast and sheeting it flat. The longer lever arm of the sail high up the mast might be very effective.

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Thats all you can do other than do as others have said and sail with amd outrigger of some sort to dampen you swing, which i have never seen on a cruising sailboat by the way...
Ditto. Used them on a shrimp boat and they were extremely effective but only practical (in my opinion) because the boat already had all the rigging in place for dragging nets. Just seems like to much additional crap to hang off a sailboat for one application.
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Old 29-07-2012, 17:11   #54
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Re: Slamming main in calms

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deep frz--in the ocean one doesnt wait for wind. one is not sitting without movement,especially if one has an engine. when forward progress becomes too low, then the mechanicle genny is s tarted and forward progress is maintained..........
hmmm.... in some situations, a lot of diesel needs to be on hand for this to be an option.

Kicki and Thies (who just won - with characteristic lack of fanfare - the same CCA award as Chichester, Tabarly, Knox-Johnston, the Roths et al) waited for wind in mid-ocean IIRC about ten days, on a trip across from Panama toward French Polynesia. They have a 16hp engine in Wanderer III, but as I understand they use it to bridge the inevitable quandary: windlessness, desirable in places you want to anchor, is not conducive to getting in and out under sail.

There is nothing which compares with the thrill of the first inklings of a building, solid breeze after a long calm in mid ocean. People who resort to mechanical gennies are depriving themselves of (to my way of thinking) a transcendent experience, for the sake of schedule, convenience, or habit.
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Old 29-07-2012, 19:25   #55
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Re: Slamming Main in Calms

Most of the ideas I’m aware of have already been laid out in this excellent thread: I’ve taken the liberty of summarising in one list those which may not be widely known.
I’ve added, and capitalised, any ideas I’m aware of which I didn’t come across further up the thread. At least one of "my" (capitalised) ideas was inspired by raw materials provided in this here thread. Apologies if I missed any posts and am claiming spurious originality. NONE of my ideas will be truly original; I’m pretty sure everything will have been tried sometime, somewhere. Thanks to all!


Ideas for sail roll damping: (particularly if you’re going to sit it out, and there’s a long swell from far away which looks like persisting):
  1. Storm trysail per gjordan’s excellent suggestion, hoisted as high as possible
    If the trysail is short footed relative to the mainsail, rather than using free-flying sheets, you might consider FASTENING THE CLEW TO THE VERY END OF THE (main) BOOM and topping up the boom to a rakish angle as a strut. This may enable hoisting the sail a lot higher, with a pair of nylon preventers leading slightly forrard, eg down to either genoa sheet lead, in lieu of a sheet led aft). The idea is to stabilise the clew laterally, and if you get the angles right it should be possible to achieve an ‘overcentre toggle’ action, providing considerable flattening without too much line tension.
    This MIGHT be worth considering even with a deeply SLAB REEFED main: tie the reef points in above the boom (which is as it should be in any case) tilt the boom up, and send the sail further up the rig!
    (Could also substitute a storm jib, if it can be hanked to some spare slugs?)
  2. Storm or working jib (hanked to and) hoisted high up the backstay, sheeted to a slug sent up the mainsail track (or even to the bow) – might be best to use a nylon sheet?
  3. Nylon light air main (Adelie mentioned Mainster sail – new to me but sounds like a great idea) -with no battens and hollow leech (as already suggested)
    The absolute gold standard here, it occurs to me, for a ketch or sketch or schooner, would be a QUADRILATERAL nylon sail, like a ‘fisherman’, only flat cut with hollow tablings, with the second clew sheeted to a halyard from the mizzen.
  4. I haven’t seen this mentioned: HEEL THE BOAT: (stops things rolling around in cupboards, and helps the sails to keep their bellies generally to one side (considerably, if you can get a decent angle). Once you get used to living on an angle, it’s not bad, and certainly beats slatting and/or rolling. Rearrange heavy supplies and fluids to achieve this if feasible (obviously I’m thinking here of an absence of wind, and presence of ground swell, which you expect to last for days).
  5. This next idea will be controversial, and would work best if you can arrange a significant heel first: HOIST A HEAVY OBJECT HIGH UP THE RIG (especially, but not exclusively, when at anchor). This is an old idea: gaff rigged schooners or gaff/wishbone ketches would send a storm anchor up under the gaff to provide relief from rolling. This, I hasten to add, in cases where there was a strong sheeting from the end of the gaff to the main or mizzen masthead. Even cutters, however, would sometimes send a bucket of chain or similar up the mast, with a strong downhaul to stabilise it. In modern rigs, you could send a ring up the backstay with a steadying line, and have a couple of direct lines, one to each stern quarter. Obviously you’d want to wrap whatever you were sending in something tough and resilient. If you’re in a rhythmical rolling situation, a significant change to the rotational moment of inertia can completely kill the rhythm. If you’re a sailing couple, sick to death of each other in a prolonged, fraught calm: draw straws and send the loser up the mast! Killing two birds with just one stone …. (whistling….)

    Reverting to a more serious tone: I mainly add this suggestion in the hope that thoughtful sailors won’t rule out something more moderate and feasible, say, using the reefed main up high as suggested earlier: the extra weight of the bundle of unused sail will not be a disadvantage, but might be quite beneficial.
    It will be obvious that this idea and the previous one will each help the other be more effective.
 
Ideally (if symptoms persist!), combine these measures with Anchorage type flopper stopper if stationary, or Fish type towable stabiliser if ghosting.
 


Ideas for flopper stopping/ stabilising:
  1. Snow Petrel suggested a rigid strut down to the flopper stopper, so it works on both down and upstroke. This is novel and interesting, and certainly made me sit up and think, but I’m not actually sure that this is a great idea: it seems to me it would be really hard to stop it "buckling" when it was in compression (I don’t mean failing as in the strut crumpling, but going out of line with the force, resulting in the strut‘going round the outside’. I can’t see a way to brace it in the third direction.

    I’m theorising here, so I would welcome empirical contradiction: It’s NOT generally essential, when trying to prevent a rhythmical, resonant response to an "excitation" (technical term for the force causing the response) arriving from one direction, to damp in both directions.
    In fact, often it’s best to concentrate on one direction; the other direction is only a ‘reset to neutral’.
    I think there’s a hazy analogy with helming downwind in a breeze with: it’s the ‘first lurch’ of each pair which you have to proactively preempt.
    Motor yachts use a paravane on each side, because they’re essentially a symmetrical system, but it seems to me a sailboat might get away with one only to leeward, particularly if you can provide a significant heel to leeward as mentioned above.
  2. For this purpose, a weight helps keep the flopper stopper down, but is not sufficient to this purpose. To keep the rope tight, you need to arrange some way that the flopper stopper can allow free movement of the water in the reverse direction, like a check valve. For a ‘fish’ or paravane, (google "paravane stabilizers" (US, or stabilisers= GB) this is AFAIK generally done by designing it so the suspension bridle is symmetrical about the centre of effort (when trying to lift the fish) but it’s biased to be nose heavy so that when the boat rolls towards the fish, the fish dives, so the suspension line doesn’t slacken. A fish will introduce some drag, but when you’re ghosting, it will be minimal due to the low horizontal speed, and maintaining uninterrupted flow across the sails is so beneficial that this small penalty might even be worth considering in a race situation.
  3. Stationary flopper stoppers designed for use at anchor (but also feasible offshore when there’s been no wind locally for some time) sometimes use something very like an old fashioned foot valve: a large, strongly built sieve, suspended from a three or four part bridle, with a rubber mat on top of the mesh. The rubber has a pair of slashes running North/South and East/West, running most of the way to the edge. The resultant ‘petals’ allow free flow one way but impede it the other.
    It probably goes without saying that if you’re dealing with a stationary situation, you could put some considerable weight under the flopper stopper, like a spare anchor chain chain (assuming a "long duration" is expected). The distance to leeward would also help with heeling moment, and the buoyancy penalty (as opposed to keeping it up out of the water) for something with a relative density of nearly 8 is probably negligible. And of course if you’re stationary you may be able to use the main boom as the outrigger (depending which ideas you use for a roll-damping sail)
 
I realise there are many to whom all this will be is old news, but some of this practice gets lost over the decades unless it’s continually handed on.



FOR THOSE WITH BIG TANKS (and pockets)

If you’re using the main as a roll stabiliser while relying on the motor for drive: comfort can sometimes be improved by hauling the boom to windward of the centreline with the traveller, or even a second preventer (less strain) in addition to transferring weight to leeward. Obviously you do it to the minimum required to prevent flogging. This keeps the main full (for roll damping) at the expense of some extra drag. I sometimes do a similar thing with a non-overlapping headsail (sheet it gently aback, as an admitted ‘brake’ but in order to stop flogging) if I have to take a short leg to windward under power, say in a winding channel, but will need the sail again shortly: especially if it’s a hanker rather than a roller.
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Old 29-07-2012, 21:02   #56
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Re: Slamming Main in Calms

Let me clear up a little about what I said about using a trysail as a roll stopper. I sheeted the trysail to a cleat on the stern of the boat. It requires no extra rigging or preventors or anything else that you would not have with a normal trysail. That sheeting was far enough aft to flatten the trysail when it was set about 2/3 up the mast. It did not take all of the roll out of the boat(it did take most) but it took all of the violent snap roll out. Slowing and reducing the amount of roll makes a huge differance in comfort at sea or at anchor. This is not a new idea by me. I had read about it in some old sailing book, and I recently ran across this method in an Eric Hiscock book. It was used to stop the excesive rolling when running down wind with twin genoas poled out. Keep it simple and dont beat up your main in the process.____2 cents worth.____Grant.
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Old 29-07-2012, 22:16   #57
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Re: Slamming Main in Calms

Mostly my own boats have been ketchs, when this happend to me I dropped the main and and jib left the staysail up locked im the middle. and raised a fisherman or a Yankee, as high and tight as I can, cures the rockin and the rollin and still lets ya move with even a puff of wind !! just an old way but a good one for ketch sailors
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Old 02-08-2012, 06:45   #58
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Hi

After many chances to test all your great ideas out, I confirm that for our boat ( hans christian 41 , ie heavy!!!), the third reef and staysail combo work well.

Thanks or all the advice, it has become more relaxing now during the inevitable calms in this part of the world!

I might give the trisail idea a go someday, but for now we are anchored on the algarve and taking in the scenery , wine ,and sun!!

Charlie.
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Old 08-08-2012, 04:56   #59
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Re: Slamming Main in Calms

The trysail is the best option. If you can get it set high enough it will take almost all the roll out. A genua, half rolled and then tied tight on the center line is the next best option. If you have to use both.

I tried both these options in heavy sells and they work
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