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 Slider Cat

design and story by Ray Aldridge

 

Slider is a 16 foot minimalist cruising catamaran with comfortable, adjustable seating inside the hulls.

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Specifications

Length overall - 16 feet
Waterline length - 14 feet, 11 inches
Beam - 8 feet, 6 inches
Sail Area - 140 sf
Draft-board up - 11 inches at max disp.
Draft-board down - 40 inches
Empty Weight - 500 pounds, approx
Payload - 600 lbs.

The Boat

I designed Slider to be the most luxurious 16 foot open boat beach cruiser possible. Much of the luxury derives from the fact that Slider is a catamaran, and consequently has a very stable and level ride. Even more luxurious is the adjustable seating within the hulls, where much of the crews’ bodies are protected from the elements. The helmsman steers facing forward in a comfortable molded seat, using a steering line that runs around the perimeter of the center deck and hulls. Once at anchor, luxury takes the form of a fairly spacious tent, which allows two people to bed down on the center deck, with one cockpit and its seats enclosed by the tent, and the other cockpit open for access to the outside world.

Once at anchor, luxury takes the form of a fairly spacious tent, which allows two people to bed down on the center deck.

Because Slider is a cruising boat, her sail area is a conservative 140 sq. ft. This is undercanvassed, by the standards of beach cats such as the Hobie 16, which carries 218 sq. ft. of sail. Slider has slightly more stability than a typical 16 ft. beach cat, because of her greater weight… but if Slider capsizes, she probably can’t be righted by her crew, due to her very buoyant hulls. Sailing with sheets in hand, on the edge of capsize, is not my idea of relaxing cruising. In addition, Slider is intended to be sailed by two crew, one remaining in each cockpit in most circumstances, and without any necessity for the leeward crew to scramble across to the windward hull on every tack.

Because Slider is a cruising boat, her sail area is a conservative 140 sq. ft. This is undercanvassed, by the standards of beach cats such as the Hobie 16.

Despite her modest sail plan, Slider is not a slow boat, particularly when compared to monohull open cruisers of similar size and power (and substantially less luxury. This is due to her fine, 10 to 1, low-resistance hulls. She has a deep offset daggerboard in the port hull, and moderately high-aspect kickup rudders. She goes quite well to windward, especially considering her sprit-sloop rig, with its home-made mainsail. I chose this ancient configuration out of a personal curiosity about its suitability for a tiny cruising multihull, but I’ve also drawn a conventional Bermudan rig, and such a modern rig would have its mast stepped in exactly the same spot.

Despite her modest sail plan, Slider is not a slow boat, particularly when compared to monohull open cruisers of similar size and power (and substantially less luxury.

Slider’s greatest virtue, in my opinion, is her handiness. She tacks effortlessly, unlike many cats, which as a breed are notorious for being slow in stays. She has a modest amount of weather helm, so that if the steering line is released, she comes up into the wind and waits there, sails luffing, for as long as necessary. While she makes her best speed to windward with the sheets cracked slightly, she has a remarkable ability to pinch up and keep sailing more slowly, when necessary to clear a buoy or other obstruction.

Slider’s greatest virtue, in my opinion, is her handiness. She tacks effortlessly, unlike many cats, which as a breed are notorious for being slow in stays.

Her shallow draft and flat bottoms make her easy to beach and to trail on a simple home-built trailer. Her mast can be raised or lowered in moments, because her forestay is tensioned with a zero-stretch Dyneema lanyard led back to the forebeam.

Slider seems to be a completely new kind of beach cruiser. So far as I know, Slider is one-of-a-kind. There are other 16 ft. cruising cats, but none of them are open boats with in-hull seating.

The Plans

The plans include eight 11" X 17" drawings, and a 12,000 word builder's manual, as well as email support from me. Appended to the manual is a diagram so that builders can build their own polytarp sail, if they wish.

The plans include eight 11" X 17" drawings, and a 12,000 word builder's manual, as well as email support from the designer.

When I first thought about building Slider, the idea of selling plans seemed a little goofy to me. The reactions I’d gotten to my idea, from friends and in the various online boat-design forums were dubious at best, and among those critical reactions was one that struck me as possibly accurate: “Okay, so if, as you claim, a little cat with in-hull seating would be so easy to design, why hasn’t a real designer done it? Maybe it’s harder than it looks.”

Maybe it is, I thought, but fortunately, this sensible view of sailboat design did not deter me from trying. It did, however, keep me from taking a lot of pictures of the many elements that make up a little sailboat, nor did I keep acurate records of everything I did. I guess I was afraid that the little boat, when I completed her, would be one of those eccentric creations, like a pram rigged as a brigantine, that everyone enjoys seeing when one comes sailing by, but only their owner really wants.

Slider seems to be a completely new kind of beach cruiser. So far as I know, Slider is one-of-a-kind. There are other 16 ft. cruising cats, but none of them are open boats with in-hull seating.

Slider’s been sailing now for nine months, and I’m convinced she’s pretty special. Whenever I’ve taken anyone out, the reaction has been uniformly enthusiastic. The boat is handy, goes well to windward, has a lively turn of speed, and above all, is unbelievably comfortable, for a 16 foot boat. She’s remarkably dry in a seaway, the seats are luxurious, visibility is perfect, and steering is easy. She tacks effortlessly, unlike many catamarans. She’s sturdy too; we’ve rammed docks and chipped the paint a little, and once we hit a sandbar with the daggerboard down, doing six knots, and neither case nor board was damaged.

Materials

Because I kept imperfect notes during building, my estimate on materials needed and costs involved may not be accurate. However, here are a few honest guesses:

Plywood: I believe Slider can be built with 14 sheets of 6mm or 1/4″ marine ply, plus one sheet of 3/4″ and a half sheet of 1/2″. 4mm ply would do for planking the topsides, if glassed on both sides, but I’d stick with 6mm for decks and hull bottoms. I used a high-quality birch underlayment called Multiply, because it was available locally, and was a lot cheaper than marine plywood.

In this video, we're sailing to Destin in Slider, the 16 foot beachcamping catamaran I designed and built. Winds are just under 10 knots, and we're moving at 5 to 5.5 knots. Comfy. My wife Nancy is steering.

Solid timber usage is more difficult to estimate, because I was completing a number of home improvement projects during this time. I used construction grade timber for the most part in all projects. For example, my stringers, chine logs and sheer clamps were all ripped from 3/4 inch southern yellow pine, which is strong and rot resistant, but heavy. A prettier, lighter boat could be built using clear Douglas Fir, which is widely available from local lumber yards, but is more expensive.

I used approximately five gallons of Epoxy, but this included glassing the hulls to only two inches above the waterline. Were I doing it again, I would probably glass the outside of the hulls completely.

I believe I used approximately 20 yards of 6 oz fiberglass cloth, 60″ wide. This covered glassing the hulls to just above the waterline, and glassing the decks. I cut my own tapes from this material, because a tape without a selvage makes a smoother joint.

For the center deck and the duckboards in each cockpit, I used unfinished cedar, both for low maintenance and for good footing. I used about 10 pieces of 1X6 cedar, 8 feet long.

My son took this video in very light air, standing waist deep in the water, as Slider sailed past.

For the strongback on which each hull is assembled, I used 2 16 foot long 2X6s. I supported these on short saw horses, so that the hulls were at a good working height. Other large timbers were the beams– 10 foot 2X6, and the mast, which was laminated from 2 16 foot white pine 2X4s, then rounded and tapered. Again, these would be prettier and lighter in Douglas Fir.

No permanent fasteners were used on the hulls, but I went through a couple boxes of drywall screws, which were used to hold the planking to the stringers until the epoxy kicked. The only permanent fasteners were 3/8″ bolts holding beams to the beam webs and rudders to the rudders stocks, U-bolts for the forestay bridle, and various stainless screws used to attach deck and rigging hardware.

Rigging is 3/32″ 1X19 stainless. There are no turnbuckles– shrouds are tensioned via 1/8″ Dyneema lanyards. The forestay is tensioned in a similar manner, but the lanyard is taken aft to the forebeam, so that the mast can be dropped just by casting the lanyard off a cleat.

*****

Plans for Slider are available at Duckworks

Ray Aldridge has been a studio potter for most of his life, a writer for a long time, and a boat designer for a short time.  His novels and short stories have been widely published, and he is the book editor for Living Aboard magazine.

He's been sailing the Gulf of Mexico for over 30 years, in a variety of boats, starting with DoubleDare, a 27 foot catamaran designed by James Wharram. Though he subsequently owned a series of monohulls, Doubledare remained his favorite, until he designed and built his little trailerable cruising catamaran.  Slider has now become his all-time favorite, with her ergonomically correct seating inside the hulls, her stability, and her handiness.  She was built to demonstrate the comfort and safety advantages of small open catamarans; there are no similar designs available.  She was named after the red-eared slider, "a deceptively fast aquatic turtle."

Ray maintains a website (http://slidercat.com/blog/wordpress) which contains a
number of articles about Slider, her photos and videos, her cruises, and a growing collection of base camp descriptions for small boat cruisers.

He's currently building the prototype for a new car-top catamaran.

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