The Life of Boats

Tracing the Evolution of a Kayak Sailing Rig
By John C. Harris
May 2012 

CLC SailRig Mark II, mounted on a stock Chesapeake 17. Going fast, the kayak rudder is just hanging on...

I'm sure the impulse to rig kayaks for sailing is ancient.  A hull shape easily driven with a paddle is even easier to drive with a sail.  Of course, a proper kayak is very narrow, so any attempt to carry sail upwind results betimes in a capsize.  Outriggers are needed.

The CLC SailRig adds outrigger hulls to convert a kayak (or canoe) into a sailing trimaran.  This outfit makes a delightfully practical sailboat.  Mounted on a single touring kayak, the all-up weight is perhaps 75lbs, and disassembled is compact enough to transport on the roof of a small car.  The extra speed means you can contemplate long camp-cruising passages.  Plenty of spacing between crossbeams and floats ("amas" is the proper term) allow a normal kayak stroke.  The amas sit clear of the water at rest, so they don't slow you down while paddling.

Paddling a CLC SailRig
Paddling is still easy with a single or double-bladed paddle.

Hundreds and hundreds of the CLC SailRigs have been built from kits and plans.  In the 17 years the rig has been around, I've spent hours debating with builders whether the result was a trimaran sailboat, or a converted kayak.  It is the latter.  On a spectrum of speed potential, a CLC SailRig-equipped kayak will be startlingly fast, but it can't compete with newer-generation Hobies and Nacra beach cats.  I get many hopeful emails looking for the elusive $2000 20-knot sailboat.  We should address the speed issue right at the start.  Beach cat speeds are mostly out of reach for kayak conversions, for these reasons:

  1. The typical kayak hull is optimized in various ways for speeds of just 3 to 5 mph.  Add a sail and you can double that, but not quadruple it. Kayaks have low prismatic coefficients, which in laymen's terms means the stern will squat and cause drag as you get going really fast.  Also, the skinny, fine-bowed kayak hull is apt to be a submarine when driven hard, which is fun only briefly, and never very fast.
  2. Again, because they are optimized for paddling, kayaks tend to be structurally slight.  A Hobie 16 has a 26-foot mast and 218 square feet of sail.  Transplanted into a kayak, the compression loads from the heavy mast and the huge thrust would simply break most kayaks in two.  Could the kayak be reinforced sufficiently?  With difficulty, yes, but see (1);  you still have the wrong hull shape to go 20 knots.
  3. The outriggers ("amas") need to be very large to handle racing-cat speeds.  The rule of thumb, if you're designing a sailing trimaran from scratch, is that they need to be 120% to 200% of the displacement of the entire rig.  So basically you'd need three identical kayaks, which is a lot of expensive okoume and epoxy.  The 10-foot hulls in the CLC SailRig, with about 200lbs max displacement, are big enough for fun sailing but small enough to be quick and cheap to build and to carry on the roof racks.

So how fast can a good kayak-conversion go?  I've heard reports north of 10 knots, which is within the structural limitations of the CLC SailRig and, given how close you sit to the water, feels like 25.  And that's fun.  Acres of advertising copy has been dedicated to the various sailing kayaks, but as far as I know, not much design analysis.  Tracing the 17-year evolution of CLC's kayak sailing conversion will illustrate the challenges and compromises involved.

The CLC SailRig Mark I

CLC SailRig Mark I
CLC SailRig Mark I on a CLC Tred Avon Double.

CLC's first kayak sailing rig, from 1995, was an attempt to turn a kayak into a serious sailboat without despoiling the kayak.  The carefully proportioned outrigger scheme, somewhat unimaginatively dubbed the "CLC SailRig," would fit on any narrow, low-sided boat, which is to say all kayaks and smaller canoes.  Untold hundreds of the rigs were built from these plans.  Just this morning, while looking for photos of the old rig, Bill Cotton emailed this shot of a Mark I CLC SailRig, with what appears to be the optional 12-foot hulls and a sail borrowed from one of Hobie's clever designs.  It's mounted on a CLC Tred Avon Double kayak.  He reports that it's very fast.

The Mark I was sleek and attractive.  It was also quite hard to build.  The crossbeams ("akas," in the arcane multihull lingo) socketed into the hulls. Building these sockets so that they were strong enough for the loads but didn't leak was nearly impossible.  Both of the demo model Mark I's that I built leaked through the sockets.  The hulls used the "tortured plywood" process.  Every single hull had a different shape based on the unique humidity and bending characteristics of the plywood.

The scheme to attach the rig to the kayak has to allow for near-infinite variability in kayak deck and hull design.  The Mark I used heavy aluminum brackets through-bolted to the side of the kayak. This left eight big empty bolt holes when the kayak was returned to paddling duty, and I nearly lost fingers machining the brackets for the kits. We never really specified a sailing rig for the Mark I, observing that there were already some good off-the-shelf kayak sails.  Most builders just repurposed a sail from a windsurfer or sailing dinghy.

The CLC SailRig Mark II

The early SailRig got many things right, but it was almost impossibly expensive to manufacture and sell as a kit.  In 2001 I revisited the whole concept.  I eliminated the 8- and 12-foot tortured plywood amas in favor of 10-footers that were much easier to build.  Once in awhile I get something right, and I wouldn't change a thing about the Mark II amas.  Quick and painless to build, they can be driven very hard without bogging down.  The crossbeams simply bolt to bulkheads.  This is not as elegant but it's leak-proof and strong.

Kayak SailRig Lashings
Nylon lashings are good for at least a thousand pounds of shock-load each.

Gone were the aluminum brackets and holes in the kayak's hull.  Simple and immensely strong nylon twine lashings to stainless eyebolts on the deck are cleaner, lighter, don't concentrate stress, and don't leak.

The pivoting leeboard, which allows you to sail upwind, was carried over from the Mark I, though it was made larger.  To most eyes leeboards look makeshift.  This isn't fair to leeboards, but it's true that they aren't quite as efficient as a daggerboard.  A daggerboard trunk would take up most of the kayak's cockpit---and once again the kayak would be ruined for paddling by the weight, drag, and cockpit interference of the trunk.  (Still, I've done it myself, once.)  The leeboard is bolted to the front aka, which may seem too far forward to balance the sailplan.  It's just right, however.  Kayak-trimarans, with their three strongly-tracking hulls, are much less sensitive to the relationship between the CE and the CLR than the usual monohull formula shown in the design texts.  Tried on a variety of boats, the CLC SailRig has no detectable weather- or lee-helm.

CLC SailRig Rudder Epoxy Plywood
A good kayak-sailing rudder, made from epoxy-coated plywood.

Missing from the early versions was a really good rudder.  Most sailing kayaks are stuck with a kayak rudder.  These highly evolved systems offer foot-pedal steering and light weight, perfect for paddling.  They're too small for sailing speeds.  I was always able to control the SailRig Mark II with a kayak rudder, but often I was sailing with the rudder turned almost sideways, spouting a great rooster tail, because the tiny flat blade couldn't cope.  A purpose-built sailing rudder is two or three times larger in area and has a careful foil-shape to prevent stalling.  (The SailRig plans include patterns for such a rudder.)  I preferred to connect this rudder to a long tiller and steer with one hand, as foot pedals suffer from lots of friction and not much leverage.  Rigging the larger rudder for stowing and deployment from the cockpit (as is standard in kayak rudders) is hard with a home-built system and the one on our demo model just has a wing nut on the pivot bolt.  So you have to put the rudder down in shin-deep water before setting off.  The engineer types will devise remote lifting and lowering schemes.

CLC SailRig Sail Comparison
Comparison of Mark II and Mark III sails.

With the Mark II we attempted to solve the problem of a stock mast and sail.  If you've never bought a sail before, you're going to be shocked by the price. Sails aren't flat sheets of fabric with a bit of hem around the perimeter, as many assume.  They are three-dimensional, hand-sewn fabric wings.  90% of us just don't have the knowledge or equipment to make our own.  Creating an inexpensive stock sail that would really drive the CLC SailRig took about six months of work with the sailmaker, and many prototypes.  At length we settled on two sails (40 square feet and 55 square feet) with a single batten and an optional boom.  The sail had a sleeve that slipped over the bendy aluminum tube mast. This was affordable and it worked pretty well.

The CLC SailRig Mark III

"Pretty well" is something less than we aspire to, however.  The basic architecture of the CLC SailRig could stand more horsepower.  It was just a matter of designing a stock engine that was a good fit for the chassis.  First, we had to attend to the mast.  From the start we'd chosen a thin-walled 1-1/2-inch tube.  This was cheap, but there was a lot more to it than that.  The CLC SailRig is more than ten feet wide, which translates into a lot of sail-carrying power.  Instead of releasing excess energy by heeling or capsizing, the kayak will just go faster and faster until the rig is overloaded.  At some point, the over-pressed CLC SailRig will explode in a cloud of wet splinters.  The cold and wet sailor would send us a very cross email once rescued.  Thus, the mast was designed as a sort of fuse, to shear off at the deck before the relatively fragile kayak broke up under strain.

CLC SailRig Mark III
The CLC SailRig Mark III rig. Sometimes bigger is better. Don't forget to reef or you'll end up in the water.

So this was the speed limitation.  To go faster, we'd need a stiffer mast.  We stuck with the 1-1/2" diameter tube, but doubled the wall thickness to 1/8".  Thus starts a "design spiral" that must be monitored carefully.  The stiffer mast imposes much higher loads on its step, on the floor of the kayak's cockpit.  The Mark III rig needs a bunch of heavy fiberglass around the step, and a few layers on the underside of the deck for good measure.

"What about adding a jib?" I hear you ask.  A jib requires that the mast be stayed with wire shrouds led out to the hulls or it will be too baggy to sail upwind.  The shrouds shift the loads on the mast from mostly axial to mostly compressive.  The stock mast, intended to bend gently and deliberately under sail, isn't stiff enough to handle the compression, so a heavier mast is needed.  Meanwhile, the mast is pushing down on the mast step, requiring further reinforcement there.  The shrouds are pulling up on the crossbeams, and they'll need additional stiffness to handle it.  The kayak itself is being bent like a bow between the upward pull of the jib and shrouds and downward thrust of the mast, so the whole hull could use more fiberglass.  All of this takes a lot more money and especially time, for a modest increase in speed.  Meanwhile, the kayak is now too heavy and cluttered with extra structure to be any fun on its own, and sailing requires more setup time before you get under way.  Let's stick with a single sail and avoid the escalation.

For the sail design, it's logical to try to cram in a lot of area without the mast being too tall.  This suggests full-length battens supporting a deep "roach" in the sail.  Full-battened sails of this pattern can be traced back to the 19th century.  The battens both support the roach and help the sail hold its shape when going fast on windy days.  Because the sail is so big, adding one or two reef points allows you to lift up on the throttle on rough days.  One last escalation is the addition of sail track, pop-riveted to the aluminum tube, for easy hoisting and to give something for the battens to push against.  Our sailmaker Douglas Fowler did a champion job matching the Mark III sail to the bendy mast, and it pulls like a horse.  The kayak goes like lightning.  It costs more.  While the 55 square foot Mark II sail and mast cost $639 ready-to-go (and remain available), the Mark III sail, mast, track, and hardware cost $1278.30.  Welcome to yachting! 

Which Kayak is Best?

We've gone to a great deal of trouble to make sure the CLC SailRig can be fitted to any wood, fiberglass, composite, or plastic kayak.  If you had a choice, which kayak would you pick for sailing?  Surprisingly, relatively short and fat kayaks make the best subjects for a trimaran conversion.  A narrow racing kayak like the Pax 20 is the most easily-driven, so for drag-racing in smooth water you might get the highest speeds that way.  However, you'll soon be disappointed by the handling.  The long waterline, fine bow, and lack of rocker make the racing kayak hard to turn and it submarines in every wave.  Kayak-trimarans are so light that they have no momentum, and have difficulty tacking as they get "hung up in irons."  So a kayak with lots of rocker and plenty of volume in the bow is more fun to sail.  I always keep a paddle tucked under the deck bungies in case a stroke or two is needed to get the bow through the eye of the wind.

CLC SailRig on Sport Tandem
Chesapeake Sport Tandem

Larger tandem or triple kayaks are ideal subjects for conversion because they make such good platforms for expedition work.  Our Sport Tandem racing kayak, an animal of a boat that can and does demolish any paddling competition, has the deep rocker and high-volume bow you need to push hard in waves. That would be my first choice for duration trips.  The akas are centered around the front cockpit, giving the distant rudder lots of leverage to turn the 22-foot kayak.

The Chesapeake Triple is a popular choice for family sailing, and our own showroom model has a lot of miles with the Mark II rig.  It's fun to be able to stand up and walk around in that boat under sail!  It isn't slow, either.  With a 700-pound payload, you could cover a lot of ground or just take the family out on the lake.

Chesapeake Triple, Shearwater 17, Mill Creek 16.5
From top, Chesapeake Triple, Shearwater 17, and Mill Creek 16.5.

For single paddlers wanting to cover the most ground, I would pick the Chesapeake 16, Chesapeake 17, or Shearwater Sport.  They have tall bows for getting over waves, comfortable cockpits, and they're short enough to be maneuverable without giving up much speed.

I've seen a dozen Mill Creek 16.5's outfitted with the CLC SailRig, and it illustrates how open-cockpit types work just as well with the conversion.  In this case, the rear aka crosses neatly between the front and rear seats. 

Wood Duck 12 with CLC SailRig
Wood Duck 12. Spunky and it'll sail a lot faster than you can paddle.

Shorter recreational kayaks won't match the top speeds of traditional sea kayaks, but they will be easier to handle.  Given my choice of CLC's 70+ kayak models, I'd mount my CLC SailRig on the Wood Duck 12.  It would squirt along joyfully, fast and nimble in close-handling, the cockpit dry and voluminous.  The stowed package fits on the roof racks of my Mini Cooper.  Altogether, just ridiculous good fun.

If you've read this far and wondered what it would take to compete with the fast cats in a stitch-and-glue design that you could still cartop, here it is.  This soon-to-be-prototyped CLC kit is 15 feet long and will manage 15 knots.  Alas, we don't have a release date.  We may need to break a few of them before letting this little racer go free in the wild! 

Stitch and Glue Trimaran
An ultralight stitch-and-glue trimaran by John Harris. We're still fiddling with the engineering. Once we get it right, it ought to be terrifically fast and fun.