Small trailerable cruising cats... biggest flaw?

This is not far from where I live, I thought it may interest you guys.

pacific cat:

http://www.trademe.co.nz/Trade-Me-M...l-boats/Small-sailboats/auction-337773884.htm

 

Hey,thanks for the trade me link Skint, i wonder if they were imported there or if that one was brought in by an individual. Really great set of photos, i see it has all the same old crappy hardware as mine and all the old fastener holes from where stuff has been moved. Im going to remove everything and fill the holes, paint it and layout all the new gear to suit me. You can see those huge 3" cockpit drains through the transoms. That spinnaker is the same color as mine i think, my whole boat is the color of the deck on that one.
Steve.

 

Skint,

Thanks for the photos. Lots of details and the original info on the boat as well! I wish there were some dimensions of the hulls though.

Dan

 

Good plan. The hardwary has improved so much it's hardly comparable. Make sure to keep us updated on your boat.

Any idea why the hulls have such a long slot for a daggerboard? It seems more like a centerboard slot at that length.

Dan

 

Dan, your right about the daggerboard slot,i have no idea why it is so long,the daggerboards are very typical eliptical shaped fiberglass molded ones with a chord of 11 1/2" x 42" overall length, it sure gives a lot of ability to adjust balance, orrrr,i could use a pivoting centerboard like a Hobie 18 or Tornado. Might be better for a cruiser. Oh,my boat came with 2 nice glass boards and 1 black anodised cast aluminum board that weighs a ton and 2 decent but missmatched glass rudder blades and 2 decent wood ones.
Steve.

 

"Well, I did say "usable" deck, and the side decks of tris are not as usable as the center deck of a cat. And after all, we are talking about cats, not tris. Cats, in my opinion, are much better cruising boats than tris. Folding solutions for tris are well-developed-- thus my interest in doing the same for cats."

By all means solve the folding cat problem, I can't wait. My point about tris wasn't their deck space but their righting moment. To the extent that one says on wants to rely on beam not bulk, the tri is your friend, You can go square with a tri's 100% beam. and 75-80% is nothing these days. So to the extent that you are happy with 50% beam in a cat, you are already out on a limb so to speak, as relates to accepting bulk over beam.

"I've owned two cats with hard decks, and they really are a lot more comfortable, and I think safer than net. They are heavier, but the better footing makes for a safer boat to move around on."

Which is why you don't really want a folding one. The Gxx will be very solid.

"Thom, you make a number of interesting points, though I remain unconvinced of the value of ballast for multihulls. Most of what makes a multihull good comes from its lightness. An overloaded multi is a slow multi, and an unsafe multi, or at least that's the gospel according to most multihull designers."

This is the nitty gritty of the problem, and what one has to understand. Two big points (as I am sure you know) are one: No weight, no righting moment, so weight is not your enemy but bad design or overloading are. Two, the way the ballasted multi works is to start out of the box on weight. The G32 has to beat conventional ratios, so that ballast can be added partly within, and partly above conventional weight ranges. It also has to be very easy to push so that it isn't standing up under too much sail, but keeps sliding out from under the gusts.

The problem I see is how to do this on smaller sizes where the boat isn't as slippery, and where the displacement isn't as large. Ultimately you can't do it. But that is because small multis don't work, you do have to give up something to put 5 berths on an 18 foot trimaran, as some have done with highly popular designs.

"In the small sizes we are speaking about, there isn't as much payload available as you'd hope. For example, the Simpson cat with the folding aluminum beams had only three or four hundred kilos of payload., and it was a fair amount larger than what we're talking about."

Same thing with my tri, on paper it is a disaster, there is really about 200 pounds, but it sails nicely, and we have fun. At the end of the day displacement goes up to the cube of length, and small boats are always a compromise.

"But I agree that there is a certain logic in the idea of compensating for narrow beam by using movable ballast, since that's how people sail beach cats without capsizing. But the displacement has to come from somewhere, and the added displacement needed to use water ballast is a design problem without an obvious answer that doesn't adversely affect speed, especially for a cruising boat."

I agree with that. So trick one is you have to build a boat that is 66% the weight you would expect. That isn't as hard as it sounds since the hulls you build are not efficient, and you can save money and time doing it, but you will scare the last possible customer away, because they will not want to do tortured hulls... Which I don't understand, it's as if a boatbuilding saviour sent multihull builder's his best idea to rescue them from the drudgery of building slow to build, expensive, and slow to sail boats, but they just rejected it.


"I'd love to see you (or someone) build a 20 foot cat with trailerable beam and water ballast, and use a good beach cat rig. It would be very interesting to compare the solutions, and see which one had the higher performance potential. My opinion is that the light boat with the greater beam would be faster, but it's only my opinion."

And you would be right. If the idea was to make a boat that sailed off a mooring, the wider boat, at these beams is going to be the one I want. I should point out that in light air the Gxx boat will be the lighter and have lower drag, which is why they beat all those million dollar multis with the 30K production boat. But none of those races started from the driveway. What I am after is a boat that is fun to sail starting from the driveway. Really, it is too much trouble to create a narrow beam, trailerable boat unless it does a lot for you. I already have a demountable tri, that I am stuck to a mooring with. To do another build for a boat that folds (twice the building time generally), it needs to have a boat that launches like a bassboat, If I won't use it I don't need it. I think the Gxx will beat you on the water some days, from the driveway everyday, and from the workshop by a significant factor, or maybe not (depends on your solution).

" It would certainly be more comfortable, simpler to sail, less fussing with pumping ballast, and less anxiety arousing."

- Comfort i don't see...

- Simpler to sail I think depends too much on specifics, unless we are double counting the ballast issue.

- One does have to handle the ballast at some level. I have decided on going no motor for a while, and without a motor, I don't know how one gets the ballast on in heavy weather, but with a motor I don't think the ballast is a problem.

- Anxiety I don't know about. It is rightable, and only slightly less beamy. It also has the capacity to be nailed to the water with a lot of ballast. It is an integrated solid structure, with lower loading, a lot of folding designs are pretty hardware dependent. I think it is the difference between worry and risk. We don't worry about the things we are already accustomed to pushing to the back of our minds. This design comes with new worries, but is the risk lessor or greater?

 

Pacific Cat from Trade Me

Hi There
We looked at the P/Cat from Trade Me add Skint posted.
It has cast Bronze daggerboards, after market the owner thought in an attempt to add ballast. The prior owner had brought it in from The USA with him when he moved to New Zealand.
The Boat in general was in poor condition with the owner doing some home handy man work on relocating loose fittings with no backing blocks so fittings into raw chop strand. He had also tipped it over racing off Oamaru, in the South Island so think open Coastal Ocean, he brought it back to the trailer loaded it with water still in hulls then upon pulling trailer out of the water the hulls crushed damaging them badly. The resultant repairs were home handy man at best, executed by riveting aluminium to the inner hull then bogging over alloy plate with a fairly rough paint job over it. quite fair but marginal as a repair of substance. He also sealed the rear hatch's down and put new drain pipe through the rear of hulls that drain the foot wells as they take water in as she is sailed through the dagger board slots, again the replacement of the drains was home handy man at best.
The mast had two repairs to it one externally sleeved and one welded, the mast also had a slight bend in it. He raced it against Paper Tiger and Hobie 16 and said in light airs Hobie 16 would sail away from him but in a good blow he could sail rings around the Hobie. The chap selling it was a nice genuine guy who disclosed every thing about the boat.
A few photo's attached from when we viewed it and the rest of the promo doc he had for it. The repairs to mast and hulls are visible in photo's when enlarged. Also the Hobie 16 and Paper Tiger are visible in back ground of photo's.

 

Too bad it was in poor condition. Interesting cats though, and thanks for the additional photos.

Dan

 

Thom, it is always a pleasure to read your carefully considered posts. You make me think. I'll just address one element of your post, though there's lots there.

I think that tris are actually very different from cats when it comes to analyzing their response to rough conditions. I would say that despite their wider overall beam, tris are more vulnerable to wave-induced capsize than cats, due to the much higher roll moment of inertia possessed by cats.

I would not be happy with 50% beam, in a cat with a lot of sail area in proportion to its size. Slider, at just under 16 feet, has a BOA of 8.5 feet, and as you know, I put a very conservative rig on Slider. The new boat, at 19 feet 8 inches, will have a beam of at least 12 feet, perhaps more. (I'm currently playing with a model, attempting to work out a beam system that allows the rig to remain more or less taut when folded, Not easy!)

Let me add that I think beam does equal comfort. A narrow beam cat is less comfortable in a seaway than a wide beam cat-- I think this is easy to demonstrate by comparing the motion of a monohull to a cat-- and realizing that the narrower the beam, the more like a mono the cat will behave.

The goal with Slider was a cat as easy to launch as a johnboat. I think that she largely succeeds, though raising the mast may undermine that goal. But the mast on Slider is not tall, and is rigged in such a way that everything can remain attached when lowering it into its transport crotch-- boom, sail, sprit, etc. The forestay is tensioned via a Dyneema purchase, so securing the mast in an upright position is as easy as hauling on a line and cleating it off.

The new boat can't be that easy, since the rig is much larger, and the mast is much taller, and is a rotating mast. But the goal with the folding system is that it take a matter of minutes, rather than hours to expand into sailing beam, and that the rig remain in place when the boat is folded, so it can be dry-sailed with convenience similar to a dry-sailed mono.

Anyway, wonderful discussion!

 

I did a quick look at Wood's offerings in the sub 25' range and his consistently come out at 58%-66% for his racier offerings.

Dan

 

Ray,at 12ft beam on a 20ft cat you are at about 60%,my feeling is that the higher you go the more prone you are to diagonal tripping and also the jerkier the motion in a seaway.My old Macgregor 36 was 36x18 and had a very nice motion with none of that jerky motion ive experienced on bigger bridgedeck cats although it was probably more atributed to flexability. A lot of time can be saved at the ramp by streamlining the small things as much as the folding system itself. One place you may want to look for inspiration for a folding system might be the cross strut geometry on those cheap pressed steel sawhorses you can buy at the bug box lumberyards.
Steve.

 

Beam is a very complicated subject, isn't it? I don't think 12 feet is too much on a 20 foot cat, since a number of designs I admire use a similar beam ratio, as Dan mentioned..

One aspect of it that I've wondered about a lot is the question of handiness. Slider is one of the handiest boats I've ever sailed, monohulls included. She never misses stays, and no particular technique is required to get her to tack. I've wondered how increasing the beam relative to LOA affects handiness. My suspicion is that the wider the beam, the less handy the boat. This issue is further confused by my intention to use a single central rudder on the new boat. I'm told that this does not negatively affect steering, and I hope that's correct. A single rudder (and board) on the centerline spine simplifies folding substantially, because there is no tiller bar to complicate matters. Also means the boat can be steered while folded.

Steve, in a sense I'm using a similar technique to stabilize the beams when unfolded. I like hard decks on cruising cats, even tiny ones. The plan is to hinge the decks along the centerline spine, so they can be folded up and bungied together before folding. When the boat is unfolded to sailing beam, the decks drop down and lock onto the hulls.

 

I agree on the hard decks if you can make it work (which im sure you will) dont be afraid to use a single daggerboard in one hull if it makes more sense structurally,it really makes no difference sailingwise,i think having one in each hull is more about mans insistance on symmetry than anything else. I think on the handiness subject i suspect that the wider one goes the more important ackamman angle becomes which of course requires two rudders, however Kelsal uses a single rudder on some wider boats i think but no idea how it worked out.
Steve.

 

Going wider

As to handiness Ray - if you go wider you increase the roll moment of inertia. That is why cats are better in beam seas than tris. The discussion earlier about tris and their higher beam is fine in a static sense but one very good reason that cats do not have to be as wide as tris is because they have significant masses at their maximum beam. Tris have most of their mass in the middle.

To understand roll moment of inertia think of a pole with two weights on it. If you get the two weights in the middle you can swing the pole easily. Now move the weights to the ends of the pole. The pole is now much harder to swing around.

This is one reason cats don't tack as well. You have to accelerate one (heavy) hull relative to the other and this takes energy and speed. Tris being more like the weight in the middle scenario are much quicker to tack. They also only have one hull in the water during a portion of the tack.

Roll moment is a bugger when tacking but great in dynamic situations like gusts and waves. Cats have more so can be narrower.

Diagonal stability is only a problem if you do the silly thing by saying - My cat/tri is beamier now I can put more sail on it. Well you can if you only go on a reach but a square run will find you with exactly the same fore and aft stability as before and then you are closer to capsize. Although going wider will mean that the boat gets a bit heavier.

cheers

Phil

 

Steve, you're right about the single daggerboard. Slider has only one big daggerboard in the port hull, and it works wonderfully well. If I'm remembering correctly, the MacGregor 36 was originally produced with a single daggerboard, but the outcry for symmetry among potential customers was so loud that the design was altered. Despite the lessened efficiency of a non-end-stopped board on the central spine, I'm thinking of going that way, because the cabins are so small-- and for a couple of other reasons, including curiosity.

Phil, I agree completely. In fact, up in post #69, I said, "I would say that despite their wider overall beam, tris are more vulnerable to wave-induced capsize than cats, due to the much higher roll moment of inertia possessed by cats." This is a point I try to make whenever the safety of cats vs. monohulls comes up, as it still does, despite all. I remember long ago reading the report on the Fastnet disaster. When I got to the part about dismasted vessels being subject to repeated capsize, due to the missing inertia of the masts, 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.

Slider tacks reliably in all conditions, with all sail combinations, although her beam to length ratio is slightly higher than 50%. I've always suspected that was because I gave her more rocker than is thought to be ideal, because it was the only way I could get enough displacement for two people and a camping outfit in 16 feet, and still keep the hull fineness to 10:1. I'm hoping that going to a 60% ratio will not make the boat difficult to tack.