Following Seas and Cockpit Height

[tp12]

Originally Posted by morven55

Cat People seem to be easily irritated...not to mention defensive.

Cat people on this forum have been subjected to a lot of trolling and are, understandably, biting back. Root cause analysis would suggest where the problem lies but people always tend to notice the reaction, not the original action ...

[ozskipper]

Transom height has less to do with the problem than how the stern handles following seas. If the stern is lightweight and lifts up, any boarding wave will be less damaging than a transom that doesnt lift.

Imagine two identical boats, Boat one has a few hundred kilos of Fuel/water, (whatever) on the stern. The other, boat 2, has weights stored mid ships.
The stern on boat 2 will go up and down with the waves, where as the stern on boat one is more likely to bury itself a little. Thats an over simplified answer as there are plenty of other variables too.

[Sailing55]

Originally Posted by tp12

Cat people on this forum have been subjected to a lot of trolling and are, understandably, biting back. Root cause analysis would suggest where the problem lies but people always tend to notice the reaction, not the original action ...

Root cause analysis might also suggest that some folks are taking things a little too seriously...

Overly sensitive people can be targets for trolling...especially if they react.

Cats, Monos...who cares if you are comfortable with your choice?

[Udacha]

Originally Posted by morven55

Irritating? Many things are irritating, including snarky comments...but why take the bait?

I was, actually, trying to lighten things up a bit. But you gotta admit, some Cat People are quite defensive, and easily baited.

Disclaimer: I have no negative opinions regarding cats or large sliding doors on oceangoing vessels.

"But you gotta admit, some Cat People are quite defensive, and easily baited."

My observation is.... But you gotta admit, some Boat People are quite defensive, and easily baited.

I'm on the fence on whether to get a mono or cat, it will probably depend what my bank account looks like after I sell my home, but I can see good things about both designs.

Also, there are a lot, maybe millions of Sport Fishers built since the 1960s that have huge rear facing sliding doors

[Sailing55]

Originally Posted by Udacha

"But you gotta admit, some Cat People are quite defensive, and easily baited."

My observation is.... But you gotta admit, some Boat People are quite defensive, and easily baited.

I'm on the fence on whether to get a mono or cat, it will probably depend what my bank account looks like after I sell my home, but I can see good things about both designs.

Also, there are a lot, maybe millions of Sport Fishers built since the 1960s that have huge rear facing sliding doors

I'm with you 100%...people should pick the design that suits their purpose and requirements. If we all had the same opinions it would be a dull world. I mean no offense to anyone, and hope that people make good decisions based on solid science and healthy boat design.

But bear in mind that not all designs are suited for all conditions of wind and wave. Hopefully you will do your homework and choose a design with a proven record and plenty of good reviews from experienced non-biased folks.

[Sailing55]

Originally Posted by ozskipper

Transom height has less to do with the problem than how the stern handles following seas. If the stern is lightweight and lifts up, any boarding wave will be less damaging than a transom that doesnt lift.

Imagine two identical boats, Boat one has a few hundred kilos of Fuel/water, (whatever) on the stern. The other, boat 2, has weights stored mid ships.
The stern on boat 2 will go up and down with the waves, where as the stern on boat one is more likely to bury itself a little. Thats an over simplified answer as there are plenty of other variables too.

Quite true Oz...I was on a little 32' Gran Tumlaren [canoe stern] once and having low freeboard I was absolutely amazed at how that wonderful little boat was handling 15' short, steep seas going into Newport Oregon in 25 or so knot winds. Those big waves would roll up astern and she would just lift like a duck as they rolled under the boat. I had absolute faith in that old girl...
Hull shape, fullness of after sections, overhangs, weight distribution, many things affect how a boat handles the seas.

[Southern Star]

The monohullers have it - we multihullers are just too damn sensitive to uneducated, unsubstantiated attacks on our boats. If we don't participate in the same way on the monohull threads, that's our fault - we take our boats and the truth too seriously!

When I get the chance, I am going to start some new threads and contribute to others on the monohull thread. Not espousing demonstrably untrue and negative assertions about monohulls as fact - we multihullers are too serious for that! No, asking some serious questions that I and most current owners of multihulls must have about those who still buy monohulls.

Cheers amigos!

brad

[OceanSeaSpray]

Originally Posted by Southern Star

Oceanseaspray you are correct - as I pointed in post#7, there are monohulls such as Open 60's whcih can perform as well (and as safely) as most catamarans because they mimic catamaran design: extreme beam with relatively flat underbodires and twin canting rudders create more bouyancy and form stability aft.

You are incorrect, however, in concluding that the typical cat and mono have the same dynamics:

They don't mimic anything (noticed the deep keel?) and rudders have nothing to do with buoyancy and stability. The only volume that is of interest is the one that gets submerged when a wave approaches and, in this regard, a relatively wide-sterned monohull in fact tends to have more to offer, this is why I said "waterplane area aft": slice the boat at the waterline and look at the shape of the cut and do the same again with a slightly higher waterline and look at the rate of increase aft. While you are at it, do the same to a Wharram.
However, some of today's cruising multis have such fat and flattish hulls that they certainly approach monohulls. They need it to carry the weight, but also to counteract tendencies to dig in, hobby-horse etc.

They do share the same dynamics because the principles they have to obey to are the same. They react the same to approaching waves and essentially behave the same provided the boat, regardless of configuration, can accelerate, track and stay in front of the wave.

Originally Posted by Southern Star

1. Cats typically have hulls extending aft well behind the bridgdeck/cockpit which increases the leverage of that bouyancy. How many monos with wide after bodies have their transoms well aft of the cockpit?

There isn't that much effective volume in those hull stubs extending aft, even less so when they have been cut away to create boarding platforms, steps and the like.
If the steep part of a wave managed to reach them, they would clearly sink into it much more than a single broad hull.

Originally Posted by Southern Star

2. It is not just bouyancy in the hulls of a cat that creates lift in a following sea - the aft end of the bridgedeck can also create lift when approached by large following seas. Look at the picture of the Lagoon 380 and you should be able to envision what I am talking about.

If you start getting buoyancy from the bridge deck, well... you have lost the plot already because your stern is dug into the wave, not riding in front of it (where it should be) any more and your stub hulls extending aft have failed to lift the boat.
The scenario you really want to avoid is getting the stern into the breaking crest because there is way too much energy being expended there.
That (and engaging the bows) is the main concern monohull people have always had when they think of a multi running in a steep following sea. There isn't always much boat to pop the stern up and the weight of the engines (usually very far aft) increases inertia and makes the stern slower to lift.

Originally Posted by Southern Star

3. Apart from Open 60's and the like (which can and do surf), most cats are able to surf in large following seas with minimal risk of broaching. Check out youtube videos of even small 'condomarans' like the Lagoon 380 safely hitting 16 knots plus downwind in the Southern Ocean to see what I am talking about.

This is very true. Most boats will surf in front of a fast wave however, even a bloody double-ender if the bilges are not too slack... think about Vito Dumas and his little 30' in the 1940s and Moitessier in his steel box.
Course stability doesn't have much to do with being a multi or not, but the reason why multis don't broach is the same as why most won't really point. You can get a boat that will both point very high and run on rails - I own one.
Trouble doesn't develop so much on the run with regular long fast waves, but rather when they get steep and the additional worry is engaging the bow(s).

A fast wave in the southern ocean will do something like 30-40 knots, so the boats you see sailing at 16 knots aren't in any impressive sea or being challenged. Imagine even just an 8' vertical wall of water catching up with you at 30 knots: you have got two options, do 30 knots now until it has flattened out or get hammered.
If the top breaks and plunges forward (as it does), water can hit you even faster than that.
If you are going to engage in no-limits sailing, it is just that there might be better design options than a full height cabin rear and sliding door facing the stern with limited volume in the stern. Make a sensible use of the boat and it might well prove very acceptable; get caught into something outside the envelope and you might regret it.

For the rest, I am not interested in polemics, people attacking people and angry arguments. Today's cruising multis are amazing boats if you use them for what they are intended for, and they can become next to useless if you stray away from that.

This being said, the gap has closed significantly in recent years. Multis carry weight much better, they are much more buoyant now and they have become slower in average. On the other hand, recent monohulls are more stable, heel a lot less in average, track much better and have become faster.
They also used to have deep cockpits and you were sitting in them where motion was reduced. Now they just have huge aft cabins and you are left virtually sitting on deck. But that's ok, because you just have to surround it with a dodger, close the sides, add arches and decorate the stern with half a tonne of gadgets. At this point, they suddenly have less to envy to the sliding door and the crappy upwind angle...

The problem today is that people buy boats from the inside out. They pick what looks the closest to their bloody house and the "quite secondary" sailing bit... well, it just has to do hopefully. Next come the lame excuses: oh, we can motor; we won't go there; it won't happen to us, and the list continues.
Then we stop and wonder about the crap design options main selling points, haha.

[tp12]

Originally Posted by morven55

Root cause analysis might also suggest that some folks are taking things a little too seriously...

Overly sensitive people can be targets for trolling...especially if they react.

Cats, Monos...who cares if you are comfortable with your choice?

That's true, to an extent. However, when it's repeated often and is, quite clearly, against the forum rules regarding trolling, that we've all signed up to, it begins to chafe. Some responses to trolling have been moderated, yet the trolling continues, further adding to the feelings of discontent.

[Southern Star]

Wow, twin (especially twin canted ) rudders have nothing to do with stability? They don't help to avoid broaching? Gee, the naval architects desiging modern performance monohulls (especially those designed for trade-wind routes) need your imput desperately! Same with increased beam and flat sections aft - there is no such thing as form stability!

You are right. The naval architects are wrong. And the sliding doors on catamarns implode all the time - its just a conspiracy to keep it quiet! I'm out of here until you and some of the other catamaran bashers put up numerous examples of what seldom, if ever, happens to support your ridiculous theories.

Brad

[Oliver L.]

Red Herring,

if you are still interested...

We are cruising in our Lagoon 470, so far a bit more than 20,000 sm, and we have had a lot of situations where following waves got a bit high for our comfort level. My observations are:

The length of the sugar scoop seems to be critical. As soon as the wave reaches the first hull (because you never go dead downwind), the boat will start to tilt slightly and to lift the stern. Once the second hull assists, even 4 m waves shrink rather quickly. We have never had a wave enter the cockpit or swamp the dinghy (which is another big real life concern), but I admit that we have to climb over our cockpit enclosure upon boarding - something you don't need to do on some other cats...And no, we have never broached or gotten seriously off course, but we have surfed - at times frighteningly fast. The next reef was overdue...

I don't like the current trend of shortening the sugar scoops to squeeze more "livable space" into the same length, and the concept of "open space" should in my opinion stay in the Caribbean. But likes and dislikes are opinions, I have seen a lot of boats in Tahiti and Hawaii that I would never have crossed the ocean with. Kudos to the people who do...whether they are mono sailors or multihullers.

Oliver

[Liam Wald]

Originally Posted by Southern Star

When I get the chance, I am going to start some new threads and contribute to others on the monohull thread. Not espousing demonstrably untrue and negative assertions about monohulls as fact - we multihullers are too serious for that! No, asking some serious questions that I and most current owners of multihulls must have about those who still buy monohulls.

Cheers amigos!

brad

This sort of thing coming from the official multi-hull spokesperson should be absolutely amusing not to mention informative.
Can't wait!

[smj]

Originally Posted by Southern Star

The monohullers have it - we multihullers are just too damn sensitive to uneducated, unsubstantiated attacks on our boats. If we don't participate in the same way on the monohull threads, that's our fault - we take our boats and the truth too seriously!

When I get the chance, I am going to start some new threads and contribute to others on the monohull thread. Not espousing demonstrably untrue and negative assertions about monohulls as fact - we multihullers are too serious for that! No, asking some serious questions that I and most current owners of multihulls must have about those who still buy monohulls.

Cheers amigos!

brad

Don't let them get under your skin Brad. You and I, as well as probably 90+% of the multihullers on this forum started out with monohulls. My guess is the majority of the monohullers who insist on denigrating multihulls on the multihull thread have little if any experience on multihulls, and honestly probably have little experience sailing altogether. Every year it seems there are more people making the move to multis not vice Versa.


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[MYTraveler]

In heavy, following seas, you must expect the cockpit to be flooded. The real question is how quickly will it evacuate? My last boat (a battlewagon sportfisher) has had about 2' of water in the cockpit. None (other than, maybe, a couple gallons) leaked past the engine room door into the engine room, but hatches floated and the lazarette hatches floated allowing water into the aft bilges. In spec'ing my current boat, I had twin transom doors put in, so if it ever gets flooded, it will drain quickly (at least if I remember to lock them open). And the hatches all have latches, and gutters, so no water will get into any bilge. I have not yet taken huge seas over the transom, but have managed to get enough water in to be confident that even filling it would not be a problem.

[Red Herring]

Well, seems like this thread got a little bent along the way. None the less, to those who actually addressed my question, thank you. I think you have confirmed what I was thinking. Height and buoyancy are nothing but good, as is scoop length. I don't mind climbing up and in, I think I would prefer that to an open stern with walk through. All the boats I am drawn to seem designed in such a manner. The Catana 471/2 and Lagoon 470 being my current favorites.

It's great to have this site as a resource. Thanks for sharing!