Cruising cat - sub 90 degrees tack upwind

[smj]

Originally Posted by arsenelupiga

thinking again, your cat has daggers, hence you lose another 600 kg of carrying capacity, so instead of 1.5T you probably have 900 kg assuming yours is same performance level as Umadum Looping 45.



that is very thin in my books.



our boats are very different and my claims that we can tack below 90 deg are substantiated by tracks.



It is true that I am improving our boat performance but not because i want to race anyone, but because we preparing for multiple ocean crossings where speed is really important.



Boat is built well, we had no failures in 30 k nm and close to 9 years. Do not use internet as source of truth else you get mislead Comparing to other boats we sailed to NC, many had failures, breakages so others are probably hiding the failures.

God has blessed you with the perfect catamaran......no let’s change that to the perfect boat!

[sailjumanji]

Originally Posted by jmh2002

I suspect the answer to this is much the same as it is across many different types of boats, including monos too.



A fast boat remains a fast boat. An easily driven hull remains an easily driven hull.



Are they affected by adding weight? Yes of course. But I think in most cases it doesn't drag these boats down to 'slower boat' level.



Let's use the example of Umadum, a Looping 45, that you mentioned.



Nobody is talking about a ridiculous example of taking a 6T empty boat and adding 12t to it.



So even if they have a 1.5T load capacity, but add 3 tons to it instead, it still remains a light boat with a high sail area to displacement ratio and slim easily driven hulls (even if they are slightly less slim now with the extra weight).



Certainly I agree that it's possible to improve the performance of slower boats, by keeping them light, adding more sail area, and optimising everything possible. That's just good sense.



But it's a big jump up to that 'next level' performance.



So in summary yes of course there is a 'percentage loss' to the fast boat with added weight.



But I don't think the 'percentage gain' on the optimised slower boat will be enough to make up for the overall difference.



Here's a real world example even though it's from monhulls. Back in the day many of us will have done deliveries on light fast race boats. But on delivery the boat is loaded up with ALL the races sails, spares, tools, etc, etc, and is also normally sailed with old and/or smaller delivery sails too.



Is all of this noticeable? Of course. But even in this heavy 'delivery trim' these boats still remain much faster than the equivalent cruiser or cruiser/racer.



Yes multis are more weight sensitive. But the same principle applies.

Excellent post. I've worked on PHRF Committees for offshore sailing cats for almost 25 years. My experience is identical to yours. There is never an inversion whereby an overloaded performance cat is slower than a condo cat.

[tamicatana]

Originally Posted by smj

God has blessed you with the perfect troll…

Fixed it for you

[jmh2002]

Originally Posted by arsenelupiga

you are forgetting about bridgedeck clearance loss. If as you say loads 3 T then we see 30-40 cm drop in clearance. That is outright dangerous. I had opportunity seeing lighter cats loaded in these 3-4 m beam seas and i can assure you it iwas not pretty. Confirmed by crews. As i am polite will not repeat their werds.

I don't think either 44'cruisingcat 's boat or a Looping 45 or similar types of performance cruising boats will lose 30-40cm in bridgedeck clearance in that situation.

Instead I think we are talking about changes in centimeters, not changes in portions of metres.

Additionally, those types of boats normally have good bridgedeck clearance in the first place, so just like performance they are less affected if they lose a small percentage of it.

[jmh2002]

Originally Posted by sailjumanji

Excellent post. I've worked on PHRF Committees for offshore sailing cats for almost 25 years. My experience is identical to yours. There is never an inversion whereby an overloaded performance cat is slower than a condo cat.

Thanks

In my experience, people with a lot of actual real world sailing experience and knowledge, have... well... actual real world experience and knowledge about these things...

[smj]

Originally Posted by arsenelupiga

you are forgetting about bridgedeck clearance loss. If as you say loads 3 T then we see 30-40 cm drop in clearance. That is outright dangerous. I had opportunity seeing lighter cats loaded in these 3-4 m beam seas and i can assure you it iwas not pretty. Confirmed by crews. As i am polite will not repeat their werds.

That’s a 12”-16” drop in clearance for an extra 6,000lb load? That gives an immersion rate of 1” per 375-500 lbs of weight. Are you talking about a beach cat?

[44'cruisingcat]

Originally Posted by arsenelupiga

you are forgetting about bridgedeck clearance loss. If as you say loads 3 T then we see 30-40 cm drop in clearance. That is outright dangerous. I had opportunity seeing lighter cats loaded in these 3-4 m beam seas and i can assure you it iwas not pretty. Confirmed by crews. As i am polite will not repeat their werds.

Does your uninformed, invented garbage have no end?

Most 40 footish lightweight performance cruising cats have immersion rates around 350 - 400 kg/cm. So your 3000 kg will reduce bridgedeck clearance by 75mm or less.

Given that they probably had significantly greater clearance than most built for charter boats in the first place, it's unlikely to be a problem.

[44'cruisingcat]

Originally Posted by smj

That’s a 12”-16” drop in clearance for an extra 6,000lb load? That gives an immersion rate of 1” per 375-500 lbs of weight. Are you talking about a beach cat?

He has no idea what he's talking about.

[44'cruisingcat]

Originally Posted by arsenelupiga

your boat is optimised for costal cruising, mine for long ocean crossing.

No, your boat is optimized for credit card captains to motor around (possibly with sails hoisted for decorative purposes) safe locations like the Whitsundays, parts of the Caribbean and the Mediterranean.

It has as many beds and heads as possible crammed into it's length so as to share the costs of charter over as many people as possible. It's built to accomplish this as cheaply as possible.

Sorry for the reality check.

[arsenelupiga]

Originally Posted by 44'cruisingcat

Does your uninformed, invented garbage have no end?

Most 40 footish lightweight performance cats have immersion rates around 350 - 400 kg/cm. So your 3000 kg will reduce bridgedeck clearance by 75mm or less.

Given that they probably had significantly greater clearance than most built for charter boats in the first place, it's unlikely to be a problem.

you build your own boat and do not know about archimede law ?

Our waterline is 11.45.

Our widest point is 1.84

Hull takes up 0.59 of the rectangle formed by above 2

Hence 11.45 *1.84 * 0.59 = 12.4m2

We have 2 hulls hence area is 24.8m2

Our boat to sink 1 cm takes 248 kilos.

[arsenelupiga]

wow guys you should relax. Enjoy your boats but really no need to get aggressive. I am enjoying mine.

So is all good.

There is always internet that produces 'truth' that you like.

Objectivity, who cares.

[44'cruisingcat]

Originally Posted by arsenelupiga

you build your own boat and do not know about archimede law ?

Our waterline is 11.45.

Our widest point is 1.84

Hull takes up 0.59 of the rectangle formed by above 2

Hence 11.45 *1.84 * 0.59 = 12.4m2

We have 2 hulls hence area is 24.8m2

Our boat to sink 1 cm takes 248 kilos.

You better avoid carrying too much then. You've got precious little bridgedeck clearance to start with...

A Schionning Cosmos 1160 has an immersion rate of 216kg/cm, not so much different from yours.

[arsenelupiga]

Originally Posted by 44'cruisingcat

You better avoid carrying too much then. You've got precious little bridgedeck clearance to start with...

A Schionning Cosmos 1160 has an immersion rate of 216kg/cm, not so much different from yours.

impossible. His hull would have to be 1.6m wide at waterline. Looks to me less than 1m. You probably mixed imperial with metrical.

You better do your math for yours. What you need to do is take pic of your boat from distance ideally using telescope. Then put on PAINT app and you can measure hull width at waterline vs some known distance on your boat, say boat width.

[arsenelupiga]

Attachment 239200here is how i have done after discussing hull width properties with you. Anyone should do it.

We are 6.22:1 which is distance from 8:1.

[arsenelupiga]

This is approximate calc for Oram 44 from data i guessed.

Hull length to width = 15:1
Hull length = 44 ft = 13.41m
Assume same 0.59 factor for hull shape - this does not change much.

calc

Hull width at waterline = 13.41/15 =0.895 m

Immersion = 0.895*13.41*0.59 = 70kg /cm

3 tons will sink your clearance for 43 cm

1.5T will sink for 21.5 cm

This may be acceptable in coastal sailing but nono for ocean sailing as boat and crew will suffer.


I am sure you are careful with weight.