Following Seas and Cockpit Height

[arsenelupiga]

Originally Posted by 44'cruisingcat

I don't think it's safe to assume most cat's are light displacement these days. Some are remarkably, almost incredibly, heavy.

true. lagoon is 1 of these. Boat can be pushed to 10 kn , any more you need to surf.

However, my wife does not like speeds above 8 kn for any length of time as it is too noisy and annoying for her.

[Sailing55]

Originally Posted by arsenelupiga

true. lagoon is 1 of these. Boat can be pushed to 10 kn , any more you need to surf.

However, my wife does not like speeds above 8 kn for any length of time as it is too noisy and annoying for her.

Lagoon 400 is not a heavy boat, it has a D/L Ratio of 169 which is considered light displacement.

[smj]

Originally Posted by morven55

Lagoon 400 is not a heavy boat, it has a D/L Ratio of 169 which is considered light displacement.

It displaces over 13t, way heavy. It also has a LWL/BH of less than 7, that's how it handles the weight at a cost to performance.


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[Sailing55]

Originally Posted by smj

It displaces over 13t, way heavy. It also has a LWL/BH of less than 7, that's how it handles the weight at a cost to performance.


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Oh, I looked it up and was listed at only 10 tons...boat designers use long tons of 2240...and a DL of 170 or so is actually light displacement. Weight vs waterline length...

[smj]

Originally Posted by morven55

Oh, I looked it up and was listed at only 10 tons...boat designers use long tons of 2240...and a DL of 170 or so is actually light displacement. Weight vs waterline length...

Maybe lightweight for a monohull, but for a catamaran?


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[Sailing55]

Originally Posted by smj

Maybe lightweight for a monohull, but for a catamaran?


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They are just numbers and formulas used in comparing different boats. Displacement tells one how much salt water a given weight "displaces" and is useful in determining how a given weight is distributed along a given waterline.
Multihulls simply have more hulls and different way of distributing the weight, but the numbers for heavy vs light displacement remain the same. Your cat will just not have the weight carrying capacity that a like boat of higher D/L ratio would have. !0 tons may seem like a heavy boat, but distributed along a 39' waterline, it is actually a light boat.

edit: on the other hand it will likely have better performance...

[smj]

Originally Posted by morven55

They are just numbers and formulas used in comparing different boats. Displacement tells one how much salt water a given weight "displaces" and is useful in determining how a given weight is distributed along a given waterline.
Multihulls simply have more hulls and different way of distributing the weight, but the numbers for heavy vs light displacement remain the same. Your cat will just not have the weight carrying capacity that a like boat of higher D/L ratio would have. !0 tons may seem like a heavy boat, but distributed along a 39' waterline, it is actually a light boat.

edit: on the other hand it will likely have better performance...

Lagoon 400 displaces over 13 tons, the Fusion 40 less than 6 tons. I would say for a multihull the Lagoon is heavy, but makes for a decent cruising boat.


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[tp12]

In the multi world, these boats are very sensitive to weight. For a cat at 11t to be light it would have to be over 60' IMO.


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[44'cruisingcat]

Originally Posted by smj

Lagoon 400 displaces over 13 tons, the Fusion 40 less than 6 tons. I would say for a multihull the Lagoon is heavy, but makes for a decent cruising boat.


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In reality you won't find any 6 tonne Fusion 40's. (Or 13 tonne L400's either I expect.)

[44'cruisingcat]

Originally Posted by morven55

They are just numbers and formulas used in comparing different boats. Displacement tells one how much salt water a given weight "displaces" and is useful in determining how a given weight is distributed along a given waterline.
Multihulls simply have more hulls and different way of distributing the weight, but the numbers for heavy vs light displacement remain the same. Your cat will just not have the weight carrying capacity that a like boat of higher D/L ratio would have. !0 tons may seem like a heavy boat, but distributed along a 39' waterline, it is actually a light boat.

You don't seem to understand the major difference between multihulls and mono's. Ballast.

A 10 tonne 40 foot mono may be a lightish boat, but that's because about 4 tonnes of the 10 is lead. A 10 tonne 40 foot cat is NOT a light boat.

[StuM]

Originally Posted by 44'cruisingcat

You don't seem to understand the major difference between multihulls and mono's. Ballast.

A 10 tonne 40 foot mono may be a lightish boat, but that's because about 4 tonnes of the 10 is lead. A 10 tonne 40 foot cat is NOT a light boat.

Yep,light and heavy are not absolute terms, they are comparatives.

And using a D/L formula to determine the "heaviness" of a multihull and compare it to the generally accepted D?L ratios for light/heavy monohulls is totally inappropriate.

Clearly yet another person who has felt the need to comment in this multihull design thread with no knowledge in the area.

[smj]

Originally Posted by 44'cruisingcat

In reality you won't find any 6 tonne Fusion 40's. (Or 13 tonne L400's either I expect.)

Your probably right, just numbers I pulled of Multihull Dynamics to make a point.


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[44'cruisingcat]

Originally Posted by StuM

Yep,light and heavy are not absolute terms, they are comparatives.

And using a D/L formula to determine the "heaviness" of a multihull and compare it to the generally accepted D?L ratios for light/heavy monohulls is totally inappropriate.

Clearly yet another person who has felt the need to comment in this multihull design thread with no knowledge in the area.

Our D/L ratio puts our full-time liveaboard cruising boat in the "extreme racer" category....

[Sailing55]

Originally Posted by StuM

Yep,light and heavy are not absolute terms, they are comparatives.

And using a D/L formula to determine the "heaviness" of a multihull and compare it to the generally accepted D?L ratios for light/heavy monohulls is totally inappropriate.

Clearly yet another person who has felt the need to comment in this multihull design thread with no knowledge in the area.

According to the designers of Lagoon 400:

Light displacement of 22,500lbs for a D/L ratio of 189 is considered to be a light displacement boat

Max. loaded cruising displacement of 30,000lbs for a D/L of 248 [heavy displacement boat]

And using the D/L ratio to determine whether a boat is in the Light Displacement category or not is EXACTLY what I was pointing out.

A cat with a D/L of 189 compared to a cat with a D/L of 248 IS a light displacement boat.

Do you really feel the need to be so rude if you don't agree with someone? If I am wrong I would like to understand where my logic is flawed. But is it really necessary to be so nasty?

[Sailing55]

Originally Posted by 44'cruisingcat

You don't seem to understand the major difference between multihulls and mono's. Ballast.

A 10 tonne 40 foot mono may be a lightish boat, but that's because about 4 tonnes of the 10 is lead. A 10 tonne 40 foot cat is NOT a light boat.

Ballast is irrelevant. If a cat or a mono hull has a D/L in the 150 to 200 range it is a LIGHT DISPLACEMENT boat.