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Old 29-02-2008, 14:41   #106
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That's a wimpy answer (grin)

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Originally Posted by rickm505 View Post
I think this entire conversation is boat dependent. There is no one answer.
C'mon Rick, that can't be the final word in a thread titled "multihull capsize due to lack of experience".

Specific to multihulls the following list always applies. Yes I'll wimp out too enough to acknowledge/disclaim some factors will vary for each boat... The factors are in play to a generally increasing degree with performance capability of the boat, and will vary proportional to heading relative to wind, waves, weight distribution and hull buoyancy, mast height, sail area and overall length/beam:
  1. Initial stability is far greater than monohulls, in all cases.
  2. They are not self-righting, in all cases.
  3. Weight aloft is a more significant factor in generating centrifugal force in a turn, overall, compared to most monohulls with lead ballast. This can work for or against you depending on boat handling tactics used: It works for you to help force down the windward hull if you quickly turn downwind, and is less effective if you do it slowly/gradually. It works against you by helping raise the windward hull if you quickly turn upwind, less so if you do it slowly/gradually (but you don't have a lot of time if overpowered to the point where capsizes is a risk).
  4. In most cases (due to narrower BWLs and lack of ballast) the multihull is capable of accelerating and sailing faster than a monohull so is more affected by the difference in apparent wind if heading is changed in relation to wind direction. (e.g. 10 knot boatspeed equates to almost 20-knot difference in apparent wind between windward and leeward headings, which is huge).
Sorry to beat a dead horse, but this is important stuff for the newbie multhull sailor to take away from this thread. It's generally no big deal to wipe out a beach cat, but the stakes are much higher for a cruiser encountering a severe squall line or catabolic(sp?) wind.
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Old 29-02-2008, 15:06   #107
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Sheeting out?

If I remember the prior posts correctly, everyone has talked about sheeting out as you turn downwind. The current high performance beach cats are not sheeting out as they turn down to depower. This does two things. One, if the mainsail was correctly trimmed, as you turn down it immediately stalls and produces less force. Two, once you have turned a little further the apparent wind moves aft and the sail is presenting less sail area normal (perpendicular) to the wind, so there is less force generated by the sail than if it were square on to the wind. This also leaves you where one poster said he would finally sheet in the sail to be able to put in the reef while running. I don't know how applicable or scary this sounds to you big multis.

There is yet another reason for some of the guys not sheeting out, and this is due to the mast warranty. They are fractional rigged boats with mast head spinnakers and they are using the leech tension in the main as a running back. At least one manufacturer has said the mast warranty is void if you sheet out the main with the chute up.

John
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Old 29-02-2008, 16:10   #108
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Quote:
Originally Posted by SailFastTri View Post
C'mon Rick, that can't be the final word in a thread titled "multihull capsize due to lack of experience".
I said that because we all have different experiences. Anyone who's been out in the rough stuff knows that when things go wrong, they go wrong instantly.

My experience is with my boat. In 50 knots my diesels can not maintain position let alone make any headway. All it took was one wave and the bow swings over, with no way to get it back into the wind, and yes sails were down. This is the reason I no longer advocate heading up.

It's strictly a boat control issue.
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Old 29-02-2008, 17:46   #109
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Rick, I understand what you are saying. I have two 30 HP yanmars on a 39'6" cat with less freeboard than is currently popular and its performance to windward under power may not mirrored by other boats. Another factor that has struck me since I wrote my last post is that the maneuver may, to some extent, be contingent upon the balance of your particular boat. If your boat has weatherhelm when overpowered, then moving to windward when on a beat is the natural tendancy for the boat - and trying to steer to leeward would be a much more difficult and slow process. If, on the other hand, your boat experiences lee helm, it may be better to head off. Not my experience with my boat, but....

Brad



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Old 01-03-2008, 10:00   #110
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Quote:
Originally Posted by SailFastTri View Post
Brad's post causes some concern to me too. I started to post a few replies -- even deleted one because I don't want to appear too contentious as a newbie on this board. However I've owned trimarans for 9 years and believe rounding up can be hazardous if you are truly at the limits of stability when starting the move.

If already pinched close upwind (very close) maybe (big maybe) that move is viable, but otherwise you'd be better served to depower the main and jib and don't turn upwind until the boat slows. Turning upwind will increase apparent wind and the centrifugal force from the turn (acting on weight aloft) will tend to assist the wind in lifting the windward hull.

Executed with alacrity, a turn downwind will almost never add any concerns about broadside waves.
Been there. I especially agree with the bold type! You're inviting the centrifugal forces on the weight aloft to add to the wind pressure which is already pushing you in that direction, namely toward capsize.

Steve B.
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Old 01-03-2008, 11:32   #111
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It sounds as if whether you fall off or head up depends largely on where your apparent wind is. Ahead of the beam and you head up, aft of the beam and you head down. Ahead of the beam you sheet out, aft of the beam and you do not. If you are forced to do any of this in a panic, then you probably should have reefed some time ago.
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Old 01-03-2008, 12:01   #112
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Quote:
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It sounds as if whether you fall off or head up depends largely on where your apparent wind is. Ahead of the beam and you head up, aft of the beam and you head down. Ahead of the beam you sheet out, aft of the beam and you do not. If you are forced to do any of this in a panic, then you probably should have reefed some time ago.
I would not agree with that synopsis. On any of my Dragonfly trimarans apparent wind is always ahead of the beam while reaching, unless you're already deep reaching in a downwind course. I would never round-up if severely overpowered, until that condition was brought under control by depowering sails and slowing the boat.
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Old 04-03-2008, 12:40   #113
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Steve and Sailfast, I am wondering if the dynamics in your Dragonfly tris are the same as my cat? Firstly, there is no doubt that your boats will accelerate much more rapidly than my rather pedestrian cruising cat, even with the slightest increase in apparent wind. Secondly, when I am already beating/close reaching, it is highly unlikely that heading up to the point of a luff is going to increase the apparent windspeed by such significant amounts (as my boat will not exceed 10 knots unless surfing). Thirdly, I have never flown a hull in my cat (and never expect to), but have certainly seen performance tris with not only the windward ama out of the water, but the leeward ama starting to bury. How to respond in these circumstances on a tri is not something I would pretend to have an answer to.

In my experience on a rather heavy cruising cat, when going to windward/close reaching and suddenly feeling overpowered (albeit not right at or past the boat's ultimate limit of stability), heading up seemed the best course of action for all the reasons already enunciated. Keeping my boat on the same heading likely would also have worked (albeit the weather helm was trying to pull her up into the wind). Nonetheless, I believe that luffing up was a preferable course of action as: it took less time than moving the traveller to windward and letting out the jib sheets; secondly, if I had attempted to retain the same heading, until the sails were thus depowered I would have been forced to keep the helm turned to leeward in order to counteract the weatherhelm - sounds simple, but difficult while moving the traveller and letting out sheets; thirdly, once depowered the bows would have immediately wanted to head off to leeward, potentially exposing even more of the beam to exposure from waves; finally, until properly into the wind, reefing (the ultimate goal)would have been more difficult.

In any case, I don't see the suggestion of Rick that this may be to some degree boat-dependant as a 'wimpy answer'. While I think we can all agree that getting yourself into a situation where you are actually right at or past the limit of your boats stability must entail some earlier bad seamanship, we should still consider our response and experiment with our individual boats in less extreme conditions. I, for one, feel much more confortable knowing how my boat responded in a situation which certainly seemed to be near its ultimate limit of stability. I got there, as indicated, because my reef in both the jib and the main turned out to be inadequate for the squall line that I saw approaching; in future, I would be much more conservative.
But in future should I nevertheless find myself in similar circumstances, I would not hesitate to react in a similar way in my boat. Your admonishment that you would neverround up if severly overpowered is noted, but in my case and for my boat, set aside based upon what I see as a combination of personal experience and logic.

Brad
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Old 04-03-2008, 13:51   #114
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Brad,

Forgive me if I'm missing your point, but I think you're missing the tri sailors' point.

What they're saying, and what I said in a much earlier post, is very simple: if your hull is in the air, and you're about to capsize, turn downwind. If you turn upwind, you will increase the chances of capsize. It doesn't matter how you got to the point of instability. It doesn't matter if you're sailing a cat or a tri. The point being made is directed at what to do if you are at the point of going over.

Maybe you have to have "been there, done that" to understand what we're talking about, because it was counter-intuitive to me until I actually did it sucessfully.
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Old 04-03-2008, 14:09   #115
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Hud, I didn't misunderstand your earlier post (and in fact in an earlier post of my own, agreed that if you are actually flying a hull, it makes sense to turn to leeward as at that point the centrifugal force trumps everything). What I had been talking about (and thought I had made clear), was a situation where you are not flying a hull and are therefore only approaching your vessels maximum inherent stability (maximum righting moment is, in a catamaran, typically with the leeward hull slightly lifted). Insofar as I am concerned, the major issue then is to get the sails depowered quickly, keep the boat in a heading where it will not suffer wave-assisted capsize and then reef. Others may disagree.

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Old 04-03-2008, 14:41   #116
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Apologies Hud, I just re-read my last post and while at the outset I had stated that I was referring to a situation where you are not rightat your boat's ultimate point of stability (and talked of never having, nor wanting to fly a hull in a cruising cat), I then in the last paragraph referred to being at or past a boat's point of ultimate stability as being a state that requires some earlier bad seamanship. So I understand where the confusion was created. When I then went on to say that I was more comfortable knowing how my boat responded when it seemed to be near its ultimate point of stability, I meant and said precisely that: that if I found myself in similar circumstances, I would not hesitate to respond in a similar way. And again, I added the proviso in my boat.

Admittedly I did not repeat my earlier post wherein I agreed with turning to leeward if you are actually flying a hull (due to centrifugal force and likening it to 'sway' in a cornering car) even if you are sailing to windward. But once again, that is a situation that I assume I can avoid by heading up and reefing (if sailing to windward/close reaching), or heading off and reefing (in all other circumstances).

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Old 04-03-2008, 17:58   #117
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I agree it's boat related and in a similar situation the same answer may not be the best for every boat.
My previous boat was a full keel mono bluewater boat which had a displacement of over 25,000 lbs whereas my current boat has a displacement only slightly over 5,200 lbs, but the sail area is only ten percent less in the trimaran. With the relatively lightweight tri, everything happens a lot faster including "things going South".

The first time I got hit by a relatively big unexpected gust, I was on a reach. I started to turn upwind, and immediately the seat of the pants feeling I got told me, "That's NOT what you want to be doing!" I quickly turned down wind to bleed off apparent wind to get under control. The whole thing took less time than it took for you to read this last paragraph.

Once the boat is slowed down, one can (assuming you have sea room) either reef or furl some sail. Under those kinds of conditions, even a sloppy reef is better than none!


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Old 04-03-2008, 19:03   #118
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Quote:
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Brad,

Forgive me if I'm missing your point, but I think you're missing the tri sailors' point.

What they're saying, and what I said in a much earlier post, is very simple: if your hull is in the air, and you're about to capsize, turn downwind. If you turn upwind, you will increase the chances of capsize. It doesn't matter how you got to the point of instability. It doesn't matter if you're sailing a cat or a tri. The point being made is directed at what to do if you are at the point of going over.

Maybe you have to have "been there, done that" to understand what we're talking about, because it was counter-intuitive to me until I actually did it sucessfully.
With all the Hobie racing I have done, I know for a fact that if you fall off while going to weather and you don't sheet out that it is certain that in a big puff that you ARE going to capsize. Normally you feather the boat up a bit in the big puffs to prevent capsize. When the apparent wind is aft of the beam it is okay to bear off. That is the only time I know of where it is better to fall off.

Why are big cruising cats different? The physics are still the same but on a larger scale...right?
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Old 04-03-2008, 21:23   #119
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Downwind or upwind? Still confused.
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Old 04-03-2008, 21:31   #120
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Downwind baby

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Downwind or upwind? Still confused.

That's a really cool image, and it looks like a nice boat. Blue Skye, if that boat in your image got hit with a strong gust (at the point in time that picture was taken) and rounded-up it would not be the best move. Period.
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