Catamarans Portfolio

Manu Kai : Hawaiian Sailing Canoe

Posted by on 03/08 at 01:18 PM

LOA: 23'
Beam (sailing): 12'-0"
Beam (trailer): 8'-6"
Weight (approx): 750 lbs.
Draft: 1'-11"
SA: 205 sq. ft.

Manu Kai [Bird of the Sea] is a voyaging double canoe: a sailing catamaran for raids, beach cruising, and coastal sailing. It's designed to be simple, tough, swift, safe, environmentally friendly, and economical to own and to manufacture. It is the sort of small cruiser that I wish were on the market -- that Hobie Cat® would make.

Inspired by the ocean voyaging canoes of ancient Hawaii, the identical hulls feature tall "wavecutter" bows and traditional canoe sterns for surfing large ocean swells. The boardless hulls take the stress out of beaching or accidental groundings, and the protected spade rudders will provide reliable steering control, smooth action and sensitive feel. The sharp keels provide a smooth and easy ride and good tracking, while the cutaway aft still permits tacking with a degree of alacrity.

The hulls have a slender waterline beam of 20" for low wave-making resistance, yet flare above the waterline to 32" for a bit more elbow room inside.

The simple yet efficient sliding gunter rig of 205 sq. ft. combined with the overall sailing beam of 12' will provide plenty of power, and its low center of effort will be appreciated in a sudden squall. The short 18' mast length greatly reduces the sweat required to step it, as well as suffering less windage and overturning moment of the more standard marconi rig when reefed.

Accommodations are spartan below, but the large deck area permits the pitching of a deck tent to convert the canoe from a fast sailboat to a stable camping dock. Cooking, eating, and lounging are done on deck, and a large double berth also fits under the tent. The hulls feature two single berths, plenty of stowage space (could we fit a bicycle?), and a private marine head.

Designed for simplicity in sailing, trailering, as well as manufacturing, the canoe employs sliding aluminum tube cross-beams to compact its sailing beam of 12' to a trailer capable beam of 8'-6". Hull and deck are identical for both hulls, the central auxiliary engine pod give a total of 6 major molded parts from 4 molds for composite (wood core/cloth/epoxy) manufacturing. Though originally conceived for open-mold fiberglass production, this boat would make a very cool cedar stripper. The light weight of approx. 750 lbs. will allow the double canoe to be easily trailed behind even small cars, and encourages the boat to be dry moored, and stored at home during the off season.

Manu Kai is named in honor of the first modern Hawaiian beach sailing catamaran, the original 38' Manu Kai designed and built by Woody Brown and Alfred Kumalae in 1947.

Please Note: The drawing above is a cartoon, a sketch, a doodle. No plans exist.

Comments

• Lovely work, Michael.

  Eliminating daggerboards, kick up rudders and all that other stuff is a brilliant stroke for the no hassle/low cost cruiser.  J.S. Taylor would surely approve of her good looks.  I do too.

  Have you run any numbers for load carrying capacity with a 20” bwl?  I assume you have done a quick calculation for her surface area since you are guessing her displacement.

  I love the sliding gunter rig.  Perhaps with the cost savings of the simple tapered aluminum mast, you could spring for a carbon sprit (what do you call a gunter spar?).  It wouldn’t cost much to make the curved, tapered mandrill.

  I imagine her molded from glass and vinylester resin in female molds, with a couple of chunky balsa stringers neart he waterline and two more at her sheer.

  Maybe her tacking and light air performance would be improved by a little cut away at the fore foot.

  Speaking of beautiful, modern cats with traditional roots, have you seen the Nigel Irens designed Rustic Schooner just launched in Florida?

  Check it out:

  I http://www.constellationyachts.com/rustic-3/index.html

  Posted by  on  03/13  at  10:04 AM

• Hi Chris, thanks for the comments. I’m basing weight off of a Wharram Tiki 21, which I hope I can equal or better. Its payload is 1000 lb. which I think would be adequate. Good thought on the gunter yard (that’s what I’d call it).

  Thanks for the link to the Rustic Schooner. I’ve been following this project for years, glad it finally launched! As you might guess, I’m very a much a fan of “modern cats with traditional roots” and this one is very nice. Too bad about the all white paint job - I know its Florida, but it would have looked really nice with a bit more color and brightwork.

  Posted by Editor  on  03/14  at  09:33 AM

• Hi,

  Very sharp looking boat. What about a plywood build with a hull shape similar to Mbuli? Is that a flare shadow in the topsides? Any drawing of similar yet larger boats?

  RonB. 

  Posted by  on  03/16  at  10:14 AM

• Plywood version would be very different hull shape - as you say, maybe like Mbuli. Yes, that is a flare just below the hull/deck joint. And yes, sketches of bigger boats lying around, just waiting for scanning.

  Posted by Editor  on  03/18  at  10:19 AM

• Michael,

  I love this concept.  I’ve been working on a similar design in cylinder molded plywood but a bit larger at 26 feet.  I always wondered why a small simple inexpensive beach cruiser like this has not hit the market.  Perhaps the profit margin isn’t there to support a commercial venture.  Anyway, this vessel is a great idea.  You should develop and market plans for it.

  Tom

  Posted by  on  05/22  at  09:39 PM

• Tom, I’m glad you like the idea. If you have some drawings of your boat, I’m happy to post them here.

  Posted by Editor  on  05/25  at  03:44 AM

• Michael,
  Very attractive! I have been sketching ideas for my next project and have decided on using the “molded skeg”. I first saw the idea on the Nacra cats and recently found your ‘Manu Kai’ and the Rush Catamarans ( http://www.rushcatamarans.com/ ). I have been curious as to why this hull shape has not been used more often. It seems to be a very good solution for maintaining shallow draft while providing lateral resistance. Any thoughts on this?
  Here is a link to a couple of my sketches. ( http://www.geocities.com/fhrussell/Designs.html ) The second sketch is the 32’ design I have in mind to build next.
  Thanks,
  Frank

  Posted by  on  08/08  at  12:34 PM

• Frank,
  I think the Dart catamaran was the first boat to sport this hull shape. It is indeed a very good hull - the design was a big success, and roundly imitated. The Rush was obviously inspired by the Dart.

  

  Reasons not to use it:
  1. The hull shape is a bit complex, impossible to build in plywood, and certainly more difficult that a basic round bilge hull.
  2. No boardless boat is as good to windward as one with deep foils - so racing evolution tends to select for daggerboards.

  Since Manu Kai is intended to be a rough and ready performance cruiser, I wanted a design that was tough, foolproof, low maintenance, and forgiving of accidents, yet still go very well to windward, and I think this hull shape achieves that goal.

  I like your sketch. The boat looks bigger than 32’. Personally, the rig (wing mast and all) looks intimidating and expensive to me, but it will certainly be fast!

  Posted by  on  08/10  at  09:25 AM

• My dream..... use the same concepts used by the open source community to design an “open source” catamaran.

  If everybody contributes to the design with ideas, drawings, calculations, etc. we should get a pretty nice boat.

  Would be nice to start with Manu Kai and develop the plans, construction details, sail plan, etc.

  I don’t know anything about boat design, but I can contribute with a web site and the tools needed to monitor and publish the progress of the design.

  Just a dream, but many dreamers can make the difference.

  What do you think ?

  Luis

  Posted by Luis Machado  on  09/18  at  08:02 PM

• Nice design.  I came to this page via a search on the proa Mbuli.  I’ve been wondering about a catamaran version.

  I’m told the gunter spar is strictly a yard, but I don’t know why.

  Posted by  on  10/20  at  05:16 AM

• Michael,

  Are you going to develop plans for this cat?  It is almost exactly what I have been looking for.  The other boat that remotely resembles it is the Kontiki 23.  I still think that there might be a market at least for plans for such a versatile little cruiser.  What do you think it would draw?  Would you be able to go more Dart/Wave/etc where there isn’t so much depth to the hull and go with kick up rudders instead?  It’s got to be trailered anyhow… If you do develop plans, I’ll be in line to buy them and build it.

  Dan

  Posted by  on  01/20  at  01:10 PM

• Hi Michael,
  I tried your contact link but get a “syntax error” message back. Is it fixable or could you contact me re Manu Kai
  Thanks,
  Jim

  Posted by  on  09/18  at  11:03 PM

• I really love this design.  It looks fun and friendly....nothing like a floating hotel.  I am interested in the hull shape.  Is this a semi-planing hull or does it perform more like a displacement hull?  What is the expected speed in say 15 knot winds and a bit of chop.

  Posted by  on  09/12  at  04:07 AM

• Commercialising suggestion:

  I like the idea of building the hulls and components in China, and then shipping the compacted kit-set to overseas markets.  This would help hugely to make the construction cost based mainly on materials, and not tricky manufacture.

  You can include a DVD video tutorial that shows people exactly how to build it from a kit-set, just like a TV cooking show.  This should be very popular, because it takes away the headache of having to decode text-image style instructions.

  Note:  Making the video.  Just record, on a digital camera, someone constructing the boat from the kit-set from beginning to end.  Use one or two spotlights to ensure a clear picture.  From here, edit out all the non-informative video material, and do voice-overs to explain what’s going on (don’t actually talk while it’s being built - unclear to hear, difficult and time consuming to make the video).

  Posted by  on  09/12  at  12:23 PM

• Hi Richard, thanks for the comment. The hull is deep and narrow - definitely displacement. I’d want 11-12 knots in a 15 knot breeze, (am I dreaming?) maybe more in stronger wind. I think basically it is a cross between a Prindle or Dart beach cat, and a Wharram.

  Posted by Editor  on  09/12  at  08:16 PM

• Hi Andrew, thanks for the tips. Though China is the obvious choice for modern manufacturing, off-shoring labor to the lowest global bidder isn’t exactly my sustainable dream - I’d much rather the product be built inside its major market (which may indeed be China in the near future), using locally sourced materials and labor, as much as possible.

  Agreed about the video. I also think that much could be done online with video, PDF’s, etc. (available to a subscriber) that could remove much of the mysterious for the first time boatbuilder.

  Posted by Editor  on  09/12  at  08:37 PM