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Old 13-06-2018, 16:45   #31
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Re: Motion In The Ocean...

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Originally Posted by scarlet View Post
Those videos were more of what I had suspected! And several people have mentioned our "slow speed"... Our skipper seemed to think we were going fast, but I know cats usually do better than that. I'm still thinking that our sail trim was way off.
To avoid setting any false expectations, those videos were from a Catana 48, a Lock Crowther/Christophe Barreau designed boat with dagger boards that probably has less interior space than the 38 ft charter catamaran you were on, but does sail very well. What I particularly liked about her was our ability to sail well in lighter winds when others were motoring. The speed overall was great, but being able to keep sailing even in lighter winds was a big plus for us. But that is not important for everyone, we had friends with a similar sized Lagoon with big fuel tanks who were just as happy to motor while we sailed, and we got there about the same time in light winds.

And I may have been over-estimating the capabilities of the boat you were on in saying it was slow - however from your description it sounded like you might have been trying to point high, rather than footing off a little to make the ride more comfortable and usually faster. Impossible to tell without being there, but I certainly made that mistake frequently when I first moved from a mono-hull to a catamaran.
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Old 13-06-2018, 17:19   #32
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Re: Motion In The Ocean...

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Photo here
Aww Phil, that's a bit rude to post boat porn so early in the morning:smile

I had not realised your Chamberlain had a wishbone rig. I'd like to catch up some time and talk about your experience with it. Was your rig done by AYS? Looks like we'll have similar sailplan as well, aft mast cutter rig with prodder.

Here's a rendering of our new FreeFlow 50 with wishbone rig:
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Old 13-06-2018, 19:44   #33
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Re: Motion In The Ocean...

As belizesailor is right, cat hulls, in most conditions, oscillate out of phase from each other. Running DDW, dead up wind (under power, of course) or off the wind on very long period swells in moderate winds tends to minimize or eliminate the oscillations.

I've owned a 47' sailing cat and experienced the yawing and jerking in 15-25 knot winds in 6' to 8' seas. I own a 41' mono which is very sea-kindly up 35 knots in the channels between the Hawaiian Islands. And have crossed the Gulf of Mexico in a 45' mono hitting fast-moving cold fronts of short duration with momentary gusts up to 70 knots, not fun but not too scary. I also own a 47' power cat but haven't had the opportunity to take her out in serious sea or winds and I don't know it I want to.

The out-of-phase hull oscillations of any catamaran makes me question their real seaworthiness. If I were going way off shore in one I would check and double check my weather window and have plans B,C & D to seek shelter.
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Old 13-06-2018, 20:12   #34
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Re: Motion In The Ocean...

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As belizesailor is right, cat hulls, in most conditions, oscillate out of phase from each other. Running DDW, dead up wind (under power, of course) or off the wind on very long period swells in moderate winds tends to minimize or eliminate the oscillations.



I've owned a 47' sailing cat and experienced the yawing and jerking in 15-25 knot winds in 6' to 8' seas. I own a 41' mono which is very sea-kindly up 35 knots in the channels between the Hawaiian Islands. And have crossed the Gulf of Mexico in a 45' mono hitting fast-moving cold fronts of short duration with momentary gusts up to 70 knots, not fun but not too scary. I also own a 47' power cat but haven't had the opportunity to take her out in serious sea or winds and I don't know it I want to.



The out-of-phase hull oscillations of any catamaran makes me question their real seaworthiness. If I were going way off shore in one I would check and double check my weather window and have plans B,C & D to seek shelter.

You were good until your last paragraph, then you lost the plot. Seriously, Ďquestion their real seaworthinessĎ?????

The hulls of a cruising cat are 4-8m apart and ocean swells have periods from 50m up. One hull rising a split second before the other hull to a swell is nothing sketchy at all.

In wind chop/waves where the period is much shorter the out of phase wave impacts may be uncomfortable, but it is in no way unsafe.

BTW, in most cats the hulls do not move much, if at all, relative to each other - thatís what the main beams are for. The oscillations I assume you are referring to are simply the jerky movement of the boat caused by the different wave impacts. If your hulls are moving relative to each other and youíre not on a Wharram or other design made for soft beam lashings then something is structurally wrong.

None of us can generalise from personal experience in a particular catamaran to sweeping statements about all catamarans -canít sink, easily flipped, faster than monohulls, canít go upwind, canít sail in light winds, etc. The OP asked a reasonable question regarding the behaviour of a specific catamaran and techniques to make it more comfortable. Suggestions have ranged from particular techniques generally applicable to any catamaran to those requiring a different boat.

And just like with monohulls, modern cruising catamaran designs are on a continuum from sailing well in all directions in most conditions to not sailing very well in any direction other than a broad reach. Each person picks where on that continuum they want their boat to be.

I saw a Delos presentation where they said theyíve spent one year sailing over the last 10 years of cruising since leaving Seattle.
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Old 14-06-2018, 11:31   #35
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Re: Motion In The Ocean...

fxykty may be right from a practical point of view. Over its typical life span, given the amount of use and degree of exposure that the average cruising catamaran gets, the out-of-phase oscillations of the hulls will not generally become problematic. But in even moderately rough water these forces will put continuing stress on the bridge deck structure that, given sufficient time and intensity of exposure, the hulls will eventually tear themselves apart. Itís true however, that long before they would be expected to self-destruct they will typically flip if conditions are really that threatening.
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Old 14-06-2018, 11:38   #36
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Re: Motion In The Ocean...

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Originally Posted by jmschmidt View Post
fxykty may be right from a practical point of view. Over its typical life span, given the amount of use and degree of exposure that the average cruising catamaran gets, the out-of-phase oscillations of the hulls will not generally become problematic. But in even moderately rough water these forces will put continuing stress on the bridge deck structure that, given sufficient time and intensity of exposure, the hulls will eventually tear themselves apart. Itís true however, that long before they would be expected to self-destruct they will typically flip if conditions are really that threatening.

I'm sure you are incorrect. Very incorrect. Posts like this just gotta make you smile 😝. Or laugh 😂


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Old 14-06-2018, 12:19   #37
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Re: Motion In The Ocean...

Underdeck is a critical thing with cats. It makes all the difference in the world.

I also agree completely that a multihulls are not designed to be sailed like a monohull. You can not press their nose to hard to the wind and not suffer loss of velocity and comfort. I am not a cat sailor. But I am a trimaran sailor. You foot off and you get more comfort and better velocity.

When buying a cat I think it is imperative too be very careful with weight and bridge-deck clearance. Unless you just want to cruise with all the home comforts. I do not say that as a mean statement. In fact, many husbands do it for their wive’s comfort or because that is okay for them.

I remember going to the Miami boat show back in the early 90’s....got a ride on a beautiful Privelege Cat.. I stepped aboard...wow...my hair was on fire. The wind was about 10 knots. We had about 8 spectators on board. Sails went up and we were doing 2 knots....if that... Next ride was on a Corsair 27 trimaran. I believe the owner was a Paul Aguilar....maybe??? Still 10 knots of breeze with us doing 7 upwind...and 12 knots on a reach.....I was hooked!

I will take performance with basic amenities every time. Obviously not all want the pleasure of real sailing and prefer a compromise
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Old 14-06-2018, 14:37   #38
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Re: Motion In The Ocean...

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Originally Posted by alansmith View Post
Underdeck is a critical thing with cats. It makes all the difference in the world.

I also agree completely that a multihulls are not designed to be sailed like a monohull. You can not press their nose to hard to the wind and not suffer loss of velocity and comfort. I am not a cat sailor. But I am a trimaran sailor. You foot off and you get more comfort and better velocity.

When buying a cat I think it is imperative too be very careful with weight and bridge-deck clearance. Unless you just want to cruise with all the home comforts. I do not say that as a mean statement. In fact, many husbands do it for their wiveís comfort or because that is okay for them.

I remember going to the Miami boat show back in the early 90ís....got a ride on a beautiful Privelege Cat.. I stepped aboard...wow...my hair was on fire. The wind was about 10 knots. We had about 8 spectators on board. Sails went up and we were doing 2 knots....if that... Next ride was on a Corsair 27 trimaran. I believe the owner was a Paul Aguilar....maybe??? Still 10 knots of breeze with us doing 7 upwind...and 12 knots on a reach.....I was hooked!

I will take performance with basic amenities every time. Obviously not all want the pleasure of real sailing and prefer a compromise
Only 7 knots upwind!? Must have been trimmed wrong! 🤣

I remember the first time I sailed a Corsair. Winds were no more than 5 kts and we were doing at least the same on most points of sail...amazing light air boats. The first time we tacked with me at the helm, I did a full 360 chasing the apparent wind...very different than sailing a cruising cat.

High performance boats are great, and I do own one, but if I were to take it cruising, I would be solo...same for a Corsair...great boats to race, but to cruise...not so much.
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Old 14-06-2018, 14:47   #39
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Re: Motion In The Ocean...

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Originally Posted by jmschmidt View Post
fxykty may be right from a practical point of view. Over its typical life span, given the amount of use and degree of exposure that the average cruising catamaran gets, the out-of-phase oscillations of the hulls will not generally become problematic. But in even moderately rough water these forces will put continuing stress on the bridge deck structure that, given sufficient time and intensity of exposure, the hulls will eventually tear themselves apart. It’s true however, that long before they would be expected to self-destruct they will typically flip if conditions are really that threatening.
This may have sometimes been the case years ago in very few cruising cats but not today. There used to be monohull based writers who would draw pictures of trimarans with beams breaking and cats folding in the middle. Certainly this did occur, but apart from a racing multi, it almost never happens now.

There are a couple of reasons for this but one basic one is fatigue resistance, The above comment infers that real world repeated flexing of a structure will cause it to break. This is fatigue failure. Fatigue failure can be designed for and eliminated. Most fatigue failure is roughly logarithmic, meaning that lowering the stress to half gives you 10 times more fatigue cycles. So eventually builders learnt that adding strength in certain areas so that they were way overbuilt for ordinary stress protects from fatigue failure. The DC 3 airplane is fatigue proof. Whereas other planes have built in fatigue life spans, the DC3 can keep flying for decades after the other planes are scrapped because the loads are low enough to get the alloy parts well up into the billions or trillions of cycles. Long enough for our life times.

Chamfer panels, deep bridgedecks, unidirectional reinforcement, resin infusion, epoxy, better laminating, reduction in mechanical fastenings and better engineering modelling all make the modern multi vastly better engineered than their predecessors.

Then there is the comment about them flipping when conditions become threatening. There have been many instances of cats being abandoned in terrible weather - Ramtha in the Queens Birthday Storm and Eclipse (Richard Woods 34 footer) and left in atrocious weather. These two boats were found afterwards floating fine. Cats have capsized sure, but the idea that they either flip or break up is 1960s prejudice and without any foundation.

Did someone just troll me and I bit hard?

Cheers

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Old 14-06-2018, 14:53   #40
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Re: Motion In The Ocean...

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Originally Posted by jmschmidt View Post

I've owned a 47' sailing cat and experienced the yawing and jerking in 15-25 knot winds in 6' to 8' seas.
The rest of your posts cause me to seriously doubt this.

What design was it?
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Old 14-06-2018, 20:57   #41
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Re: Motion In The Ocean...

Robertson & Caine Leopard 47 in the channel between Bora Bora and Huahina and in any similar sea-state and wind in Hawaiian waters. It was not excessive but was detectable.
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Old 14-06-2018, 21:40   #42
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Re: Motion In The Ocean...

Detectable. Right. LOL.
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Old 14-06-2018, 21:42   #43
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Re: Motion In The Ocean...

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Robertson & Caine Leopard 47 in the channel between Bora Bora and Huahina and in any similar sea-state and wind in Hawaiian waters. It was not excessive but was detectable.

Umm, there are channels (kind of, but too far apart and the islands too low to have much interaction effect) between Bora Bora and Tahaa and Raiatea/Tahaa and Huahine. Bora Bora and Huahine are separated by a couple of islands and 45 miles, no channel.

I expect the Hawaiian channels are vastly different due to their acceleration zones.

In any case, bummer that you didnít enjoy the sailing characteristics of the R&C 47 - those are of a design generation that still looked to maintaining reasonable sailing performance. Still a bit of underpowered for its weight though, as it was designed for charter.
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Old 15-06-2018, 01:49   #44
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Re: Motion In The Ocean...

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fxykty may be right from a practical point of view. Over its typical life span, given the amount of use and degree of exposure that the average cruising monohull gets, the out-of-phase oscillations of the keel will not generally become problematic. But in even moderately rough water these forces will put continuing stress on the hull keel structure that, given sufficient time and intensity of exposure, the keel will eventually tear itself off. Itís true however, that long before they would be expected to self-destruct they will typically sink if conditions are really that threatening.

Iíve edited it to make more sense.
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Old 15-06-2018, 02:22   #45
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Re: Motion In The Ocean...

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Iíve edited it to make more sense.
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