How does a cat become too heavy?

[Cheechako]

Weight is enemy of performance in a cat or mono it seems to me. Yet, I remain unconvinced it's that big a penalty. My 42 cat carried weight better than my 47 mono.

[jdazey]

Originally Posted by Kelkara

Stu ... in those intervening years the world has stopped using pints to measure pure water ... except in the USA, where their pints are smaller ... so the only pints of water left in "the world around" today weigh a pound.

Now a pint of beer is a different beast altogether.

About a year ago while I was hauled out I met a guy with a big Lagoon getting ready to splash and head for the Bahamas. Ampong other things, he had 40 cases of beer on board. He could only go 4 knots, but he wasn't going to run dry

Cheers,

[Seaslug Caravan]

ANSWER: you load too much crap on.

I notice none have mentioned the effects of overloading on the structural integrity of the boat.



OH, thats right we just add transom extensions , raise the waterline, put the rescue services on speed dial, and bury our heads in the sand.

[senormechanico]

Originally Posted by UNCIVILIZED

As an example of an easy way to reduce weight. If you have a watermaker & 200gal tanks. Dump everything but 1gal/person/day for the planned length of the passage, & then make enough to refill your tanks when you get to your next destination, or just prior to this. Which if you're lighter by 150 gal, that's 1,200lbs. Quite a bit of weight in anyone's book.

Our trimaran's factory dry weight is 5200 lbs.
We are obviously over that with all the goodies we've added, but we have always tried to be mindful of the weight vs advantages.

We only hold 26 gallons of water, but follow your post with almost religious fervor as we make water just before arrival.

OTOH, it almost killed me to have to replace our all nylon head (weight 10 lbs) when it died and the company was long gone.
We settled on a Thetford Nano Eco which I like, but it's 38.8 lbs!
Time for wife and I to lose 28.8 lbs between us to make up for that weight gain !

[toddster8]

Too much canned food and not enough chasing mice!

[sailjumanji]

We has a friend that uses to do local bay races with his dinghy hanging in the davits. Someone asked "why does he do that.". Obvious answer was "because he can.". And while we all knew his performance was adversely affected, passing mono slugs of equal and sometime longer length with the dinghy hanging high was priceless.

Otoh, first cruise we did on our seawind, we had water tanks full at 105 gallons. Boat sailed like a pig in light air. Before we headed off cruising, we instAlled a watermaker. Now carry less water.

[Panope]

I don't know anything about cats, but I was appalled by the weight of my mono's (home-built) interior.

I tore half the interior out and it tipped the scales at 1000 pounds! The new interior will weight less than half this.

Steve

[Simi 60]

Originally Posted by Seaslug Caravan

ANSWER: you load too much crap on.

I notice none have mentioned the effects of overloading on the structural integrity of the boat.



OH, thats right we just add transom extensions , raise the waterline, put the rescue services on speed dial, and bury our heads in the sand.

I got out of my cat and got an ex trawler instead as I realised the cat I needed to be a comfortable live aboard would be 20 metres and cost a million +
Weight is meaningless when you weigh 65,000 kg.
I still have the old dead battery bank on board, 75kg x 8 right there, couldn't be bothered shifting them out.

[44'cruisingcat]

Originally Posted by Seaslug Caravan

ANSWER: you load too much crap on.

I notice none have mentioned the effects of overloading on the structural integrity of the boat.



OH, thats right we just add transom extensions , raise the waterline, put the rescue services on speed dial, and bury our heads in the sand.

Did you have to extend your boat? What design is it? (Assuming it exists.)

[downunder]

Originally Posted by 44'cruisingcat

Did you have to extend your boat? What design is it? (Assuming it exists.)

Slug always seems to avoid that question. Why?

Transom extensions are a proven economical way to improve load carrying of some catamaran designs for liveaboad. Seems the manufacturers of Seawind and Lightwave in Aus and Manta in USA also saw it that way. Likely there are others.

Any problems with transom extensions SLUG ?

[Simi 60]

Transom extensions should be done from day 1
That all seem to get them eventually.

[django37]

Originally Posted by tomfl

While I have no doubt performance will take a hit if a boat is overloaded I am even more sure the guy trimming the sails and playing with the wheel/tiller is more important to how fast the boat sails.

Agreed, good skipper and crew can make a cruising cat 20 - 50% faster than the average. After that a clean bottom is the next, and after that good sails. The sails that comes with the cats from the yard are no good. Next is weight concerns ....

[tomfl]

I had an interesting exchange of posts at SA with Ian Farrier about boat speed. As posted earlier a boat like a Seawind 1000 gets a huge boost in performance if it is modified with one meter sugar scoop extensions; so much so that the factory dropped the 1000 line and built the 1000XL which has the extensions from the factory.

These sugar scoops not only extend the length of the boat but at the aft end are a couple of inches above the water line; something that is true for most of Ian's designs. He pointed out that boat speed is quite dependent on where the stern is related to the water level.

Point is on any boat adding weight can not only change the water line of the boat; but also change what I will call the angle of the water line. I have a friend with a Shuttleworth which was so heavy (probably from the original build) that the first step of the sugar scoops were under water when the boat was at anchor. A lot of what I will call non performance cats/tris at anchor look like they are arse heavy; and it only gets worse when they are sailing.

A well designed cruising boat will have what I call an adequate water tank placed where it does not adversely affect the boats water line angle; e.g. it is as low as possible and close to the center of the boat.

The problem with adding weight to a boat is there is only so much real estate at the ideal location to add weight. Many multihullers (and fast monohullers) try and move the anchor locker aft as far as possible to best place the weight from ground tackle. But lots of folks with a condomaran simply put heavy things where it is easiest to plop them down. Too much weight forward and the chance of a pitch pole is increased. Too much weight aft and you are dragging your butt.

Especially for live aboard cruisers we tend to accumulate things that make cruising more enjoyable. Fresh water, fuel, comfortable dinghy, diving gear, and other toys all add weight. More importantly they add fun to cruising; which to me is the whole point of doing it.

Bottom line if you are adding weight carefully placing it can minimize how big a performance hit you take; not to mention choosing a well designed boat will allow you to carry more weight.

[smj]

The problem is adding a little extra weight here, then a little extra weight there, and all of a sudden your way overloaded. I'm pretty sure the Leopard is designed to handle a pretty substantial load, so your over loading won't have as much of a negative performance affect as if you had a more performance oriented cat. It is true though that the overloading will affect both performance, seaworthiness and possibly have an adverse affect on the structure of your boat.

[tuskie]

Originally Posted by smj

The problem is adding a little extra weight here, then a little extra weight there, and all of a sudden your way overloaded. I'm pretty sure the Leopard is designed to handle a pretty substantial load, so your over loading won't have as much of a negative performance affect as if you had a more performance oriented cat. It is true though that the overloading will affect both performance, seaworthiness and possibly have an adverse affect on the structure of your boat.

I agree. Unfortunately, there seems to be an attitude amongst CF regulars that overloading is OK. This has been discussed recently on another thread, in relation to a large Schionning cat that had at most a 2,000 kg payload. Assuming it was built to design specifcations. Even the legal repercussions of overloading were disputed.

If it's not sensible, safe or sane to overload anything from a billy-cart to a Boeing Dreamliner, why should it be OK to overload sailing vessels, especially catamarans? Sure, they won't self destruct with an extra ounce, but I believe designers, competent ones at least calculate maximum displacement for good reason. This topic is not new, it has been around long before the adoption of the Plimsoll Line on ships. The issues and reasons have not changed.

When the maximum displacement is exceeded, ie. the boat overloaded, the safety margin incorporated by the designer is diminished, bit by bit. As you point out, stability, freeboard, structural strength reserve, etc. are diminished. More strain is on the rigging, rudders and just about everything else.

What are the consequences in real life of overloading? It obviously depends on the extent of the overload, as well as many other factors. Probably, not much except a bit of lost speed in most cases. So, it's all good then? Not really.

I have been on a catamaran recently that the owner admits has quite a lot of water sloshing up the rear steps and washing the cockpit. Not usually much problem. The vessel is a Fusion 40, and is overloaded as a result of too much stuff on a boat constructed too heavily, ie. poorly. Similiar Fusion 40 catamarans that are constructed correctly (light and strong) and not overloaded, do not suffer pooping to the same degree, or at all.

So what? In benign conditions the overloaded cat may not encounter any issues. In heavy seas the pooping may disable the vessel or worse. In 2011, a catamaran of similar size and style, the Spirited 380 "Minx" was abandoned in rough weather in the Coral Sea due to engine bays being flooded as a result of pooping and leaking engine bay hatches. It also suffered sail damage. I don't know whether this low payload carrying "performance" cat was overloaded, but the overweight Fusion 40 in my example may well suffer a similar fate in similar conditions.

The payload of a cruising catamaran is a vital specification, along with bridgedeck clearance, sail area and draft. Its amazing how many manufacturers do not supply this figure; certainly not in the sales brochure or website. Perhaps they don't want buyers aware of this limitation?