Small trailerable cruising cats... biggest flaw?

[Steve W]

Ray,you are right about the Macgregor 36,mine was a 1979 with one board and it was not great at tacking but it had less rocker than most cats. I once talked to a guy who used to be a dealer back in the day and he was running a 1979 single board boat and a 1982 boat with two boards as cattlemarans on Galverston bay and licensed for 16 passengers,he swore that the single board boat tacked more reliably than the other. I only brought up putting a board in the hull because it may be difficult to adequate latteral support to a board in the center, i wouldnt worry about the lessened efficency of the board in the center,its just one of the many tradeoffs.
Steve.

[rayaldridge]

Steve, I plan to stabilize the central spine with water stays. This will be important for a couple of reasons. One big one is that the Nacra 5.2 rig I bought for this boat has the tack quite low on the mast. In order to clear the cabins and give the crew good visibility under the sails-- one of the nice things about Slider's setup-- I have to raise the step well above the center deck. The center spine is an I-beam with a ply web and timber caps. By stabilizing the bottom of the beam with water stays beneath the deck, I hope to stabilize the step, which will involve boxing the beam in way of the step. Because the Nacra rig has a rotating mast, that stability is really important.

Re single daggerboards-- I decided that the single board was the best solution partly as a result of the John Shuttleworth article that dealt with this issue.

http://www.john-shuttleworth.com/designs/S70design.html

I steal from the best!

[CT 249]

Originally Posted by rayaldridge

I realized that had there been cats in the Fastnet race, it was much less likely that they'd have been capsized in the first place. I think you can look at other bad weather races with mixed entries-- the 1998 Sydney-to-Hobart Race is an example-- and see that the cats fared better, in terms of capsize, than the monohulls.

Ray, the reason that no cats capsized in the 1998 Hobart is that there were no cats in the race! It's a rather extraordinary piece of evidence to use to show the supposed superiority of cats.

There were no cats in the Fastnet race but there was one tri in a parallel multihull race that was cancelled due to lack of entries. The tri capsized with the loss of four lives (i.e. a 100% death/competitors ratio, compared to the loss of 15 of the 2000+ monohull sailors and four of the small number of cruising yachties in the area).

While cats are, of course, different to tris it's hard to see the Fastnet experience as indicating that it was much less likely that a cat would have capsized.

The "mixed entry" or parallel races here have seen far more cat capsizes than mono capsizes. Here's one example -

http://forums.sailinganarchy.com/ind...pic=24488&st=0

but the Brisbane-Gladstone has plenty of others.

I'm NOT saying that monos are better or safer than multis - I've encouraged most of the people closest to me to go sailing multis offshore - but it's hard to let a claim as false as one that there were cats in the 1998 Hobart go past without pointing out the truth.

There have been many false claims made about mono safety, such as the person here who claimed that lives had been lost on monos in the B-G (not true, but several lives were lost in the tri Australian Maid in 1972). Imagine how you'd feel if there were false claims being made about multi safety - There's no reason to make false claims about mono safety either. This sort of stuff just widens the mono/multi divide, like the repetitions of the (false) claim that the NYYC banned cats back in Herreshoff's day.

[rayaldridge]

I'm sorry-- I got it wrong, it wasn't even a race. It was the Queen's Birthday storm in 1994. That's a pretty big mistake-- my brains must be running out of my ears. At least I was in the right hemisphere and the right decade!

Interesting pictures here.

I think maybe I didn't make my point very well, which is that a cat has vastly more roll moment of inertia than a monohull or a tri. This makes them less vulnerable to wave-induced capsize. I don't know if anyone disputes this, but physics is on the side of the cats.

[cavalier mk2]

The Newick tri Buck's Fizz that capsized during the Fastnet storm was found upside down with the daggerboard extended. It appeared they had been laying ahull but didn't raise the board for the necessary side slip. Some tri designers such as Bernard Rhodes and Ed Horstman advocated carrying weight in the amas to increase the roll moment of inertia while others suggest the buoyancy in the leeward ama will counteract the roll moment. Amas that are a bit immersed at rest would work more like a cat and less like a catapult than high dihedral versions. The old mono trick from the days of working sail of hauling a weight into the rigging to increase the roll moment is something to be considered for tender boats. With the variance in individual designs it is hard to generalize but monos that lose their masts would appear to be in worse shape than multihulls. It does seem that most of the recent cruising multihull capsizes of both trimarans and catamarans have been do to wind force.

[ThomD]

Did you find that Slider at 8.5 feet was uncomfortable? Why would slider at 21 feet and 8.5 feet be uncomfortable? Assuming she was upright? Monohull beam is a totally different thing, because the boats depend so highly on the external ballast with little immersion happening with roll. So they can get a nice pendulum underway.

Anyway, I don't mind what kind of cat you built. I will be excited to see anything you come up with. The Seaclipper folding design shows that not all the practical, cheap, effective, ideas have been tried.

I think there is a muscle car vs. GT kind of deal here. You already have a rig, and an OAL in mind, so you have to go with the beam that requires. My 24' x 18.5' trimaran moves along nicely under Hobie 18 and baggy sails, and sometimes gets pretty animated. So maybe you will need more beam. Whether one could configure a 21 foot boat with 8 foot beam that would have a lot of efficiencies is another mater.

[rayaldridge]

Just a slight update. I'm actually building the boat I was talking about now.



Of course, it's gone through dozens of changes. As I may have mentioned, my motto is to never make up my mind until I have no other choice.

I had something happen to me that in retrospect is pretty funny. I had the first hull wired up, and as is my habit, I tabbed between the wires with little epoxy fillets. I removed the wires, and was starting to fillet and tape the hull at the bow, when I noticed I'd missed a couple of wires. As I started back toward the open transom to pull them, I heard a terrible ripping sound and I dropped about a foot. The only way out was the transom, so as I galloped aft, the hull opened up most of the way.

More here:

http://slidercat.com/blog/wordpress/?p=559