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Old 19-03-2023, 20:08   #1
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Catamaran Paradox

I like cats. But I currently have a mono. I learned to sail in 1967 on a Pacific cat 16ft at diamond head in HA. Many years later I had a Woods design open 36ft cat . It could do 15 kn. It had no center cabin. A few years later I bought a Gemini 105. I sold it after a year. Both cats made lotsa water noise from their slab sided hulls. The FG Gemini had many stress cracks showing in the surface gelcoat.Scary. Inside underway boath boats made so much noise I couldnt sleep underway. The gemini even made lotsa noise at the docd from little 4-6 inch waves . Its hull was only 1/4" thick. The Woos 36 made a huge boomig sound at speed in 3-4ft waves on a reach or beat. It could beat as it had daggers. The paradox is that to have a speedy cat you have sloww way down for a peaceful time so why have a speedy cat.??
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Old 19-03-2023, 20:37   #2
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Re: Catamaran Paradox

Yes, generally slow down to only 160-190 nm 24 hrs runs.
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Old 19-03-2023, 23:32   #3
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Re: Catamaran Paradox

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Yes, generally slow down to only 160-190 nm 24 hrs runs.
done any ocean crossings on your Vardo? Crossing times? Best day's run? Average day's run?
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Old 20-03-2023, 00:00   #4
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Re: Catamaran Paradox

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… The paradox is that to have a speedy cat you have sloww way down for a peaceful time so why have a speedy cat.??

Well, the problem is your sample of 2 small slab-sided cats, neither of which I would call speedy (for ocean cruising).

Try a larger cat purpose-built for cruising. Last night in F4 building to F6 broad reaching with jib and double reefed main we averaged 80 miles in 8 hours, with frequent surfs into the mid to high teens. My wife slept through it all during her off watch, including my putting in the two mainsail reefs.

We have solid fibreglass hulls, but they are well stiffened (no oil canning) and lined with adhesive vinyl stuff. You can hear water rushing past, but it’s muted. The odd wave slap is noticeable. One of the joys of a longer boat is that most of the wave-induced noise takes place much further forward than the sleeping cabins.

Yes, we do slow down for comfort: we reef enough so that our top speeds don’t double our average speed. We still plan for and average 200 mile days.
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Old 20-03-2023, 03:07   #5
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Re: Catamaran Paradox

there is another reason for the speedy cat.

when times are peaceful out there, you can still be sailing. That’s one of my primary reasons.

yes you can go at TopSpeed, when the conditions are boisterous, but when the conditions are not windy enough, you can still sail. that’s one of the main reasons for having a performance boat in my opinion. The ability to continue sailing when others are motoring.

I didn’t realize you used to have a woods. Those are awesome. Richard Woods is a great designer. The simplicity of his boats and the performance are pretty cool actually. He seems to strike just the right mix between the two. He answered a lot of my questions building this boat. Very helpful. Very nice guy. Incredible designs. I’m a huge fan actually.

but as to the noise, I definitely understand what you are saying. And I also understand what fxykty is saying.

catamarans just make noise. It’s the noise at anchor to me that it’s a little bit annoying. I guess that’s because I haven’t sailed mine yet! Rrrr. But underway, the larger catamaran definitely interacts less with the surface of the water. As the chop builds, it’s still way down there. It doesn’t touch the bridge deck. It doesn’t make big slapping or banging sounds, it makes some wooshes however.

I have already had a Catalac which is somewhat similar to a Gemini but much less performance. so I can compare that with the current boat I have and it’s a world of difference in how it interacts with the water.

I think potentially also where are you sleep will make a difference. Maybe when you are underway you can sleep up on the bridge deck in the main salon area. Or the cockpit. Or somewhere that’s not up toward the bows and down in the hulls.

don’t forget the majority of time is spent not underway. So you would only have to move sleeping locations infrequently if you were bothered by the sound.

to me, I lose more sleep from the rolling and the motion of the monohulls than I do from the sound of the catamaran.
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Old 20-03-2023, 13:56   #6
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Re: Catamaran Paradox

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done any ocean crossings on your Vardo? Crossing times? Best day's run? Average day's run?
Average is probably about 170, best was 200 and had quite a few close like 198, 196 as I recall. Just crossed to Southport from Opua single-handed and averaged about 150 in pretty light winds initially but did entire crossing with reef in.
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Old 20-03-2023, 15:15   #7
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Re: Catamaran Paradox

So, basically there are 5 types of core materials. There's no core like that O55, and then plywood, balsa, foam and honeycomb cores. Which do you think would be quieter if we were comparing identical boats?
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Old 20-03-2023, 17:18   #8
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Re: Catamaran Paradox

I've sailed a lot of foam race boats that are plenty noisy so I would suggest maybe balsa or possibly honeycomb quieter. But overall if you're tired on passage, you'll sleep.
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Old 21-03-2023, 02:45   #9
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Re: Catamaran Paradox

I am reminded of this thread as I sit here at 5 AM unable to go back to sleep.

it is so unbelievably loud in the boat right now. This sucks. It’s keeping me awake. And I am at anchor.

went to bed at 11:30 PM it’s 5:30 AM. That’s not good enough sleep.

I have a foam core boat with no hard sides. It is all radius chine. Not a hard angle on the hull to be found. But the boat is very, very stiff. I think that contributes to it.

choose your anchorages carefully when you have a stiff catamaran.
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Old 21-03-2023, 03:38   #10
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Re: Catamaran Paradox

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Originally Posted by Chotu View Post
I am reminded of this thread as I sit here at 5 AM unable to go back to sleep.

it is so unbelievably loud in the boat right now. This sucks. It’s keeping me awake. And I am at anchor.

went to bed at 11:30 PM it’s 5:30 AM. That’s not good enough sleep.

I have a foam core boat with no hard sides. It is all radius chine. Not a hard angle on the hull to be found. But the boat is very, very stiff. I think that contributes to it.

choose your anchorages carefully when you have a stiff catamaran.

I don’t think that’s what the problem is (for noise at anchor). AFAIK your boat isn’t finished inside - adding furniture, cabinets, soft furnishings, floors and cushions will do heaps towards reducing noise inside. For now, scatter all the towels you’ve got over the floor and hull sides in your sleeping cabin.

We have a solid glass-hulled cat and don’t have any excess noise. We anchor wherever we please and don’t really care if it’s exposed or rough. Noise is only an issue during high teens low twenties surfs with breaking seas - then the rush of water and congestion under the bridgedeck gets loud. We travelled several days and nights on a cross country train a few years ago and waking up at night with the clatter of the rails and shaking back and forth of the carriage had me thinking “time to put in a reef”.
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Old 21-03-2023, 05:02   #11
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Re: Catamaran Paradox

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Originally Posted by fxykty View Post
I don’t think that’s what the problem is (for noise at anchor). AFAIK your boat isn’t finished inside - adding furniture, cabinets, soft furnishings, floors and cushions will do heaps towards reducing noise inside. For now, scatter all the towels you’ve got over the floor and hull sides in your sleeping cabin.

We have a solid glass-hulled cat and don’t have any excess noise. We anchor wherever we please and don’t really care if it’s exposed or rough. Noise is only an issue during high teens low twenties surfs with breaking seas - then the rush of water and congestion under the bridgedeck gets loud. We travelled several days and nights on a cross country train a few years ago and waking up at night with the clatter of the rails and shaking back and forth of the carriage had me thinking “time to put in a reef”.
That’s so funny that you mention the train!

lying in bed, that’s exactly what this feels like right now and I was thinking about it being like a train a couple hours ago. It feels like when you are on a sleeper car in a train. It’s moving about as much and it’s about as loud. Probably a little more loud.

and you could very well be right. It might have to do with some of the things that are currently not installed.

but the noise seems to come from just about where the waterline is. It’s where the air and the water are interacting outside the boat.

It almost sounds like the sound of water trickling, but at a much higher volume. I can hear every drop of water interact with the hull.

However, a purely fiberglass hull (unless 1 inch or 25mm thick) is definitely not as stiff as a boat that is made with a core. The core provides that stiffness that’s way above and beyond. stiffness of a panel comes from the thickness.

My hull laminate is about 27-28mm thick (like 1.15"). It's stupidly stiff. More than in the plans because they called for .75" foam but I got a great deal on 1" foam. So it's just ridiculous how stiff this thing is. It's like a rock.

Because the panel can’t absorb the noise through moving at all, I think it’s transmitted through a little easier.


but also I am analyzing where the sounds are coming from right now. And to be honest it sounds like they are coming from the ceiling actually. When I am laying in the berth. Because there is nothing on the ceiling. It’s just raw fiberglass. And I also don’t have my cabin soles installed in the sleeping quarters yet. so I can tell the sound that would normally be down by the water line is reverberating around the state room. That’s making it seem louder. Once I have something softer on the ceiling, that should help with the sound I think. And also the cabinetry will help because it will break up the sound waves. They won’t be such a smooth and curved surface to act like a speaker/waveguide.
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Old 21-03-2023, 06:08   #12
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Re: Catamaran Paradox

so after getting up I noticed that today’s waves are a bit of an anomaly.

I attached some pictures of a nearby boat. So you can see what’s going on. I’m sleeping in the starboard hull. you can see the starboard side of this nearby boat.

look at how the waves are breaking on the side of it and going all the way up to the toe rail.

It’s just weird stuff here. Very strong Current but the waves are coming from a different direction and breaking on the starboard hull.

That’s why it was worse than normal today.
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Old 21-03-2023, 06:12   #13
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Re: Catamaran Paradox

There's an established fix for the Gemini wave slap at anchor. It basically puts a fillet where the hull meets bridge deck. Actually the older hull design was less susceptible and we never had an issue (3400 model).

Also, the spider cracks in the gel coat are well known. Looks bad but haven't heard of any that were structural. Thin fiberglass will flex more than an overbuilt old full keel monohull. Gelcoat is brittle, so you get spider cracks even thought he fiberglass is fine.

It's a boat, they move and they make noise. Discretion is the better part of valor and all that... Generally the boat can take the bashing but it grates on your nerves. If you want to bash into short steep waves, modern flat bottom monohulls can be pretty noisy and uncomfortable too. Get yourself and old narrow full keeler if that's your preferred way of sailing. You won't make a lot of miles or have much room when you get there but you can bash thru waves pretty good.

Boats are trade offs.
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Old 21-03-2023, 06:19   #14
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Re: Catamaran Paradox

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Originally Posted by Chotu View Post
That’s so funny that you mention the train!

lying in bed, that’s exactly what this feels like right now and I was thinking about it being like a train a couple hours ago. It feels like when you are on a sleeper car in a train. It’s moving about as much and it’s about as loud. Probably a little more loud.

and you could very well be right. It might have to do with some of the things that are currently not installed.

but the noise seems to come from just about where the waterline is. It’s where the air and the water are interacting outside the boat.

It almost sounds like the sound of water trickling, but at a much higher volume. I can hear every drop of water interact with the hull.

However, a purely fiberglass hull (unless 1 inch or 25mm thick) is definitely not as stiff as a boat that is made with a core. The core provides that stiffness that’s way above and beyond. stiffness of a panel comes from the thickness.

My hull laminate is about 27-28mm thick (like 1.15"). It's stupidly stiff. More than in the plans because they called for .75" foam but I got a great deal on 1" foam. So it's just ridiculous how stiff this thing is. It's like a rock.

Because the panel can’t absorb the noise through moving at all, I think it’s transmitted through a little easier.


but also I am analyzing where the sounds are coming from right now. And to be honest it sounds like they are coming from the ceiling actually. When I am laying in the berth. Because there is nothing on the ceiling. It’s just raw fiberglass. And I also don’t have my cabin soles installed in the sleeping quarters yet. so I can tell the sound that would normally be down by the water line is reverberating around the state room. That’s making it seem louder. Once I have something softer on the ceiling, that should help with the sound I think. And also the cabinetry will help because it will break up the sound waves. They won’t be such a smooth and curved surface to act like a speaker/waveguide.
Great description of water noise in my ex Gemini.
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Old 21-03-2023, 07:55   #15
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Re: Catamaran Paradox

Chotu: 1 oz of earplugs or a thousand lbs of lead lined foam.
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