Cruising cat - sub 90 degrees tack upwind

[fxykty]

Originally Posted by django37

Waterlinebeam to depth of a semicircular (Ratio 2:1) underwater section has the min. wetted surface at rest, but as speed builds up, a flatter section has less wetted surface. Basicly, the water doesnt care if it has to moove to the sides or down as the boat passes - again length and displacement fixed.

How does it have less wetted surface? Are you expecting lift due to semi-planing?

There is both the cross sectional shape of the underwater hull (semi circular is optimal for wetted surface as pointed out earlier) and the amount of rocker fore and aft.

The amount of rocker (more is like a curved banana) affects wave making resistance - hence why many owners of length constrained cats put extensions on their sterns to reduce the upturn at the sterns. For a given length, flattening the hull, reducing draft and increasing beam effectively reduces the rocker while increasing wetted surface. I’m guessing this is what you mean - give up some wetted surface for less wave making?

[Factor]

I wonder how Grainger, Schionning, Crowther, Brown, White, Outremer, etc could have got it so wrong

[smj]

Originally Posted by Factor

I wonder how Grainger, Schionning, Crowther, Brown, White, Outremer, etc could have got it so wrong

You haven’t noticed? Lagoons appear to be winning all the races.

[fxykty]

Originally Posted by smj

You haven’t noticed? Lagoons appear to be winning all the races.

What races? Aren’t we talking about cruising boats?

If you mean events like ARC, that does not prove anything about any boat’s performance as the rules allow motoring, there are varying numbers of boats from different manufacturers, the configurations of various boats are completely different (e.g. couple or family on their older boat vs a new boat with new sails little loading and a factory crew), and of course the predominately downwind course.

[smj]

Originally Posted by fxykty

What races? Aren’t we talking about cruising boats?

If you mean events like ARC, that does not prove anything about any boat’s performance as the rules allow motoring, there are varying numbers of boats from different manufacturers, the configurations of various boats are completely different (e.g. couple or family on their older boat vs a new boat with new sails little loading and a factory crew), and of course the predominately downwind course.

I’m sorry, that was my attempt at sarcasm.

[Uncle Bob]

Originally Posted by smj

I’m sorry, that was my attempt at sarcasm.

Some of us got that.

[Training Wheels]

Originally Posted by smj

You haven’t noticed? Lagoons appear to be winning all the races.

[emoji23][emoji23][emoji23] Any Lagoons in the Vendee?

[arsenelupiga]

Originally Posted by Factor

I wonder how Grainger, Schionning, Crowther, Brown, White, Outremer, etc could have got it so wrong

because they make small volume hulls you cant load them too much.

as you know your wife will load all she can, and slow the boat, the only way to prohibit this to buy small volume boat and big waterline. And pay fortune for this.

But then she will load anyway, and your worst nightmare is here. One day lagoon with crappy old sails comes along and beat you upwind as your boat struggles with weight


Somebody said wives are really expensive, there must be some truth in it.

[fxykty]

Originally Posted by arsenelupiga

because they make small volume hulls you cant load them too much.



as you know your wife will load all she can, and slow the boat, the only way to prohibit this to buy small volume boat and big waterline. And pay fortune for this.



But then she will load anyway, and your worst nightmare is here. One day lagoon with crappy old sails comes along and beat you upwind as your boat struggles with weight





Somebody said wives are really expensive, there must be some truth in it.

That is such BS - another misanthropic guy blaming the desire for extra things on wives. Sheesh. Sure, some women demand extra stuff like full size fridge or air con on a boat (bummer for you to have such a wife, but that’s your problem). Some men do too. How about all the gender neutral stuff like dive gear, extra scuba tanks and a compressor, centre console dinghy with a 50hp outboard, ice maker, big screen TV, ...

Or, you have a wife like mine who loves sailing and doesn’t mind ‘only’ 3750kg of load capacity. We bought waterline and small volume - works for us. No fortune either.

[arsenelupiga]

Originally Posted by fxykty

That is such BS - another misanthropic guy blaming the desire for extra things on wives. Sheesh. Sure, some women demand extra stuff like full size fridge or air con on a boat (bummer for you to have such a wife, but that’s your problem). Some men do too. How about all the gender neutral stuff like dive gear, extra scuba tanks and a compressor, centre console dinghy with a 50hp outboard, ice maker, big screen TV, ...

Or, you have a wife like mine who loves sailing and doesn’t mind ‘only’ 3750kg of load capacity. We bought waterline and small volume - works for us. No fortune either.

you are absolutely correct. And I am happy you guys are aligned. That is worth a lot. We have seen tension in couples several times because of wrong boat. Something people underestimate importance of. Now if one is single, then this issue is irrelevant.

[Dave_S]

Originally Posted by arsenelupiga

because they make small volume hulls you cant load them too much.

as you know your wife will load all she can, and slow the boat, the only way to prohibit this to buy small volume boat and big waterline. And pay fortune for this.

But then she will load anyway, and your worst nightmare is here. One day lagoon with crappy old sails comes along and beat you upwind as your boat struggles with weight


Somebody said wives are really expensive, there must be some truth in it.

Originally Posted by fxykty

That is such BS - another misanthropic guy blaming the desire for extra things on wives. Sheesh. Sure, some women demand extra stuff like full size fridge or air con on a boat (bummer for you to have such a wife, but that’s your problem). Some men do too. How about all the gender neutral stuff like dive gear, extra scuba tanks and a compressor, centre console dinghy with a 50hp outboard, ice maker, big screen TV, ...

Or, you have a wife like mine who loves sailing and doesn’t mind ‘only’ 3750kg of load capacity. We bought waterline and small volume - works for us. No fortune either.

It's also wrong I believe because I have overloaded my boat and it still sailed quite well, I am sure I could have added a lot more and still sailed Ok. The overloaded performance boat not sailing as well as a heavier boat (such as the lagoon you mentioned) I am sure is just a myth.

[arsenelupiga]

Originally Posted by django37

Have designed many cats having a Master of Science degree in Naval Architure from the Tecnical University of Denmark, designed and built my first cat in 1971, and have sailed round the world in our L380. The accepted norm about of high length to beam being faster comes from high length to beam normally means the boat is lighter. But if we fix length and displacement, many cats would be faster with more beamy hulls at the waterline. Best relation between waterline beam and depth of a hull is around 2.5 to 1. This because it doesnt sink so much between its own waves at speed and get more wetted surface as the narrower hull.

never thought of that - adds new dimension to my thinking. of course if one overpowers boat and sinks hull deeper, it slows down the boat and time to reef.

cats more sensitive than monos as you have 2 bow vawes interfering.

As narrower hulls are lighter weight than wider at fixed length and displacement, using same build method, and payload is expected to be small, that is why racing boats have narrower hulls? They too need 2.5 to 1 ratio, no doubt.

[arsenelupiga]

Originally Posted by Dave_S

It's also wrong I believe because I have overloaded my boat and it still sailed quite well, I am sure I could have added a lot more and still sailed Ok. The overloaded performance boat not sailing as well as a heavier boat (such as the lagoon you mentioned) I am sure is just a myth.

until your hulls maintain 2.5 to 1 ratio you are fine. Once you pass that point, forces on structure increase much more and potential for something wrong increases correspondingly. It is like not reefing and burying bows. Speed increases just a bit, rest of energy goes into punishing your boats structure.

[Dave_S]

Originally Posted by arsenelupiga

until your hulls maintain 2.5 to 1 ratio you are fine. Once you pass that point, forces on structure increase much more and potential for something wrong increases correspondingly. It is like not reefing and burying bows. Speed increases just a bit, rest of energy goes into punishing your boats structure.

A performance boat is a lightweight boat, that doesn't mean weaker, it is made from stronger and lighter materials with more attention to design efficiencies. Not sure about all boats but thinking of my boat it might have to sit another 250mm lower probably more to increase the X section hull ratio that much which equates to roughly a little over 4t on top of the 2.5t already on board. I don't think that sort of weight increase is going to occur.

[44'cruisingcat]

Originally Posted by arsenelupiga

because they make small volume hulls you cant load them too much.

as you know your wife will load all she can, and slow the boat, the only way to prohibit this to buy small volume boat and big waterline. And pay fortune for this.

But then she will load anyway, and your worst nightmare is here. One day lagoon with crappy old sails comes along and beat you upwind as your boat struggles with weight


Somebody said wives are really expensive, there must be some truth in it.

Some time ago I offered to race your fantastically performing Lagoon in my overloaded performance cat.

You went strangely silent for quite a while.

The offer still stands....