Slider is a very conventional catamaran, except for her size, her sprit-sloop rig, and the seating arrangement in the hulls. The hulls are modified dory hulls, with a single rounded chine where the topsides join the flat bottoms. The transoms are cut off square, and tucked up well above the design waterline, so as to avoid the excessive drag associated with submerged transoms. At the bows, the forefeet are submerged when the boat is sailing on her lines. The bows have substantial flare, but are very fine at the waterline, so that the boat rarely slaps, even in big chop.
The hulls overall are quite fine at the waterline; the individual waterline beam to length ratio is better than 10 to 1. Hulls this fine readily exceed hull speed, and our best speed to date has been 8.4 knots– three knots over theoretical hull speed. Her hull flare, rubrails, side decks, and low cockpit coamings knock down a lot of water, making her a remarkably dry boat. We’ve been out in fairly fearsome chop and taken only an occasional drop of spray aboard– not enough to seriously dampen the decks.
* Slider’s length overall is 15 feet 10 inches.
* Her overall beam is 8 feet 6 inches, to allow her to be trailed without special permits.
* Her empty weight is approximately 500 pounds.
* Her maximum displacement is 1100 pounds, giving her a payload of 600 pounds.
* At maximum displacement, with rudders and daggerboards up, her draft is 11 inches.
* Her waterline length is 14 feet 11 inches.
* Individual hull waterline beam is 16.6 inches at max displacement.
* Her wetted surface, not counting board or rudders, is 60 sq. ft at max displacement.
* With daggerboard fully down, her draft is approximately 40 inches.
* Her freeboard– the distance from waterline to gunwale– is 18 inches midship.
* Individual hull beam at the gunwales is 32 inches.
* Her daggerboard is rectangular in planform and is based on a NACA 0009 section.
* When her rudders are down and board up, her draft is 20 inches.
* Her steering is set up with Ackerman linkage.
* Her rudders are rectangular in planform and based on NACA 0012 sections.
* Her sail area is 140 sq. ft., divided into a small jib and larger sprit mainsail.
* Her masthead is approximately 18 feet above the waterline.
* She is equipped with large flotation chambers fore and aft in each hull, accessible via 6 inch deck plates.
* At maximum displacement, her Sail Area/Displacement ratio is 21.
* In daysailing trim (two crew and a cooler) her SA/D ratio is 24.
* Displacement/length ratio is 75.
* Prismatic coefficient is .60
Slider’s performance has been a completely pleasant surprise. As would anyone who invests the better part of three years in a boatbuilding project, I had many hopes for my little cat, but no certainties. Slider was the first boat I’d designed, though not the first boat I’d built. I was pretty sure she wouldn’t sink, but beyond that, I didn’t know what to expect.
One of my largest worries was her tacking ability– catamarans are notorious for being slow in stays. But as it turned out, Slider is a surprisingly snappy tacker. I just put the helm down and around she goes.
I didn’t expect Slider to be very fast, but she’s an overachiever. She’s not fast compared to a beach cat, but she’s fast enough to keep up with cruising monohulls almost twice her length. She goes remarkably well to windward, for an under-canvassed 16 foot open boat. With her daggerboard down, she makes little leeway. She makes the most ground to windward sailed a little free, but she is surprisingly good at pinching up to creep around things like buoys and the tips of sandbars.
I was most surprised at her ability to get to windward in heavy air and rough chop. On a recent trip back from Navarre, we had to beat to windward in 15 to 20 knot winds, against a chop rolling down the 20 mile fetch of Santa Rosa Sound. It took us 5 hours to make that 20 miles, but Slider tacked up the Sound in large chunks. The chop was big, square, and chaotic, because of the way it was refracting off the many sandbars and points that line the Sound. Slider was barely jostled. My daughter made herself a little nest of sleeping bags in the starboard hull, and slept most of the way home. Not a drop of water landed on her during that whole 5 hours.
One of Slider’s greatest virtues, it turns out, is that she’s a very dry boat.
I’ve sailed aboard much larger boats with much more freeboard that were a lot wetter. The best illustration of Slider’s ability to keep out the wet stuff came one day when we were crossing the channel just east of the bridge. A huge express cruiser came idling out from under the bridge. Instead of waiting 15 seconds for us to clear the channel, the woman driving the monster hit the throttles about 50 feet from us, and roared past no more than 20 feet dead ahead. I’d guess the wake she left was 5 feet deep when it got to us. Slider dropped into that hole in the ocean and crashed into the middle of the following wave. She stuck her nose in deep enough that there was green water over the foredecks. But Slider rose out of the hole, the water poured aft and hit the forward crossbeam, which acted as a breakwater. Not a drop of water made it into the cockpits. I think most 16 foot open boats would have been swamped.
Finally, I’ve been very pleased with how well-mannered Slider has proven to be.
When you release the steering line, she rounds up and sits like a duck, both sails luffing. This has been a useful attribute when out fishing with a friend or family member; a strike on one of our trolled lures means we usually both abandon steering to try to land the fish.
Slider’s a very handy boat, very maneuverable, but at the same time she has a sort of stable, smooth, purposeful quality. She sometimes feels like a much bigger boat. However, in calm water two people can paddle her at 3 knots without a great deal of effort.
All in all, I’m more than happy with my little beachcruising catamaran. I’m continually making small changes in her, little improvements here and there, but her virtues have been more delightful and her vices far fewer than I could have imagined. I feel very lucky.
Copyright 2008 Ray Aldridge