Weighing down performance cats

[Fishpants]

Hello all,
I’ve read a lot about performance-oriented catamarans like Outremer, Catana etc, and how you are negating the performance characteristics by overloading the boat, in which case you may be better off with a production boat like Lagoon, FP, etc.

My question is, at what point, weight-wise, does this become an issue? (I realize this can’t be answered too specifically)

I hope to one day do some long-range cruising, and while I don’t need all the creature comforts like washer/dryer, generator, A/C, one thing I’d like is a small compressor for scuba tank fills. Would this sort of thinking preclude me from a performance cat? How would I determine how much extra weight is too much?

Thanks!

[billknny]

If you don't have a generator, how do you think you powering your scuba compressor? Certainly gasoline is not an impossible choice. Doing so safely is possible, but not easy, and adds its own weight.

Before you say "solar" have you actually looked at the amount of energy it takes to fill a scuba tank?

[Dave_S]

In my opinion no, my boat is around 7.2t empty with all the hardware, rigging sails, tender, electronics anchors etc.. if I load it up with fuel, water, watermaker, food, people, booze, toys, tools, spares etc.. it may be over a ton heavier (I'm guessing, another 1.2t). It will sail easily at the heavy load in all directions. Significantly better at all times than the big heavier cats. I am considering dive tanks and compressor over a Hookah. I do consider everything that goes on based on weight because it does affect its sailing but I think you would need to go to extremes to slow it to the level of the luxury cats.

[Fishpants]

Billknny, I don’t think I mentioned anything about solar...

Yes, was thinking gas powered compressor, but truth be told, haven’t yet put a god deal of thought into the details yet. (Recall my post says “may one day consider...)

Dave_S, thanks for the input. I was hoping that this would be the case- that you wouldn’t necessarily have to always be stripped down to enjoy the benefits of a faster cat!

[Simi 60]

Originally Posted by Dave_S

In my opinion no, my boat is around 7.2t empty with all the hardware, rigging sails, tender, electronics anchors etc.. if I load it up with fuel, water, watermaker, food, people, booze, toys, tools, spares etc.. it may be over a ton heavier (I'm guessing, another 1.2t). .

Dave, according to specs you are borderline before you put anything on.
Disp of 7060kg
Payload of 2000kg
Wouldn't that mean you should be at around 5060kg before you load her up?

Waterline 1480

[css145hs]

The Schionning models don't list actual design waterline displacement for most of them, as they cater to home builders primarily and Jeff has stated it's to keep the builders honest and on track with their weights during build. While we won't really know, the DWL displacement is likely closer to 7060+2000 than it is 7060-2000. Loading it up a bit may reduce light wind performance, but its still a fast boat. The Schionning WL1480 is a bit on the high end with a nearly 15:1 beam-length ratio, you can still do very well at around 13:1, especially if you consider that many of the production cats are at like 8:1. It will be less weight sensitive at those ratios and still sail well.

[BigBeakie]

Following on from css post above, we found a sweet spot on a 15m 50ft cat to be a LWL to Bh ratio of 12:1 to 12.5:1

I would have thought hitting 15:1 on a shorter boat was getting quite "racey" for a cruising boat, at the expense of cruising load capacity.

At that hull length and proportion the sailing numbers for light airs and the load carrying capacity were optimised. It assumes the boat is balanced so there is enough room under the transoms to avoid parasitic drag, and of course that you have efficient hulls shapes in the first place.

A suggestion is to look at the DWL line on the drawings and get the immersion number from the designer, then see where the line is for your estimated loadings. If the line climbs up and turns the corners so its on the stern transoms just below the first step, expect fairly average light air performance. Of course, compared to hulls with 8:1 ratios, it will still be moving nicely, just not optimised.


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[44'cruisingcat]

Some would have you believe if you go one gramme over design displacement, the boat won't sail at all.

These people have no clue.

Yes, there's a gradual tapering of performance. But you're starting from a place so far ahead of most production boats.

[44'cruisingcat]

Some would have you believe if you go one gramme over design displacement, the boat won't sail at all.

These people have no clue.

Yes, there's a gradual tapering of performance. But you're starting from a place so far ahead of most production boats.

[Sand crab]

I think the Catanas will handle a load better than the Outies.

[HBrew]

It’s true that if you overload them then you gradually diminish the point of having a performance cat. If you want more stuff then you need more waterline which means more $$$$’s. The real challenge is finding the true payload of these boats because the lightship displacement numbers they publish are often meaningless. In the end, I suggest speaking to owners and/or chartering to understand the true performance characteristics of various cats

[tomfl]

When he was still alive I had an interesting exchange on the internet with Ian Farrier about this topic. I get the gradual decrease stuff but there is also another issue.

Look at the stern of performance boats and often there is space to put a closed fist between the stern and water level; of course this changes when the boat heels and one side is depressed. So not only is the weight important but where the weight is located as well. Often times there is a quarter berth aft in each hull; and often times these areas are the default accumulated junk storage area. The result is the boat drags it's ass as it moves through the water. Simply moving the weight forward would often result in a performance improvement.

[yeloya]

Originally Posted by Sand crab

I think the Catanas will handle a load better than the Outies.

I don't know exactly why but this seems to be true , comparing O51 vs Catana 47, having sailed both extensively..
If the question was" how much extra weight have to be loaded to reduce the performance of a fast cat to parity with FP/Lagoon?", the answer is "almost never".. Because the fast cats are not fast only because they are lighter but because their hulls are slimmer and they carry more sail.

Cheers

Yeloya

[Fishpants]

I’m always amazed at the detail of so many responses- often greater than I had needed! Thanks to all for the replies.

As to “performance cats”, where do you think new Seawinds sit on the scale? I’ve read that they do sail well, better than many others, but is that just marketing hype? I’ve only seen the 1160 up close, but didn’t have a chance to go out on her. But owners were 2 years into a global trip and had nothing but good things to say about the boat. I’m intrigued by the new 1260...

[Dolphin460]

I agree with YELOYA. Having said that, and in reference to my Dolphin 460, which has thin asymmetrical hulls, lighter will always be faster and one should not overload a cat beyond the designers recommendation. IMO.