The Microship Substrate
© 2004 by Steven K. Roberts
Nomadic Research Labs
This document is a moderately detailed description of the
Microship substrate—the micro-trimaran itself, including the hulls,
deck fabrication, crossbeams, hatches, and other basic boat
details. We stop short of discussing the sail rig, auxiliary
propulsion systems, landing gear, hydraulically controlled rudder,
cockpit features, or electronics; these will be covered in other
articles as well as the book about the project. The intent here
is to provide enough information to help fellow boatbuilders overcome
the initial hurdles in small multihull fabrication by revealing the
fundamental structural and nautical design features of the basic
One of the driving requirements of any project is the need to minimize
the nightmare of fabrication (unless that process is amusing for its
own sake, which is certainly a valid approach). But basically, I
believe that life is too short to re-invent the hull, and frankly, if I
could have found an off-the-shelf boat that met my needs I would have
engaged in epic schmoozing or similar aberrant behavior to acquire a
pair of ‘em. We actually tried this twice (with the Fulmar and Hogfish), but the lack of clear
project specifications doomed both to failure. There’s a lesson
in there somewhere.
OK, if we can’t just go get a Microship, how do we get close?
Real™Designers think nothing of conjuring lines, scantlings,
and fiberglass layup schedules as needed, although
these tend to be people who make a career of marine architecture and
are not intimidated by the process. But building molds for hulls
and designing internal rib structures just to get something that
floats, before even starting on the “interesting” parts?
Naaah. Not at Nomadic Research Labs—that sounds too much like
work. As such, the first few weeks of this project (once we
arrived at a clear design goal, which took five years) involved the
quest for existing hulls and anything else that would let us avoid Big
Nasty Goo Jobs.
Fortunately, people have been making highly efficient, slender boats of
suitable scale for a long time… they’re called canoes.
The Center Hull
The objective here was easily stated. I wanted maximum volume in
a smooth, hackable hull, tough enough to withstand occasional abrasion
and long enough to provide a center cockpit area with room to lay my
lanky 6’4” body down to sleep.
The hackability requirement called for a hull material that would
accept epoxy and thus allow added fiberglass structures, ruling out
canoes made of plastic, aluminum, or any of a variety of
vinyl/ABS/foam-sandwich materials designed to take river-running abuse
and provide absolute flotation in case of flooding. A search of
available products in the 18-20-foot range turned up a number of
vendors large and small, and for reasons of specifications and
aesthetics I found myself gravitating to Wenonah.
Before long, two of their excellent “Odyssey” expedition canoes were
enroute to the West Coast from the company’s plant in Wisconsin (Figure
1: A pair of Wenonah “Odyssey” canoes atop Biggus Truckus,
destined to become Microship hulls.
The boats were slightly customized by the manufacturer to accommodate
our unusual needs: we had no use for the usual canoe seats,
thwarts, or gunwales, but Wenonah bonded in a pair of 1/2”
marine-plywood bulkheads eight feet apart—coinciding with the distance
between the crossbeams of a stock Fulmar 19-foot trimaran. Why
was this dimension relevant? In parallel with the canoe quest, we
had discovered to our delight that we would be able to purchase outer
hulls and crossbeams from Fulmar Canada, shortly before their
discontinuation of the product. Not only did this save another huge
load of work, but it freed us from having to come up with this
dimension ourselves through some arcane combination of marine
architecture and rectumology. There would be quite enough
inspired guesswork over the next few months anyway, and it’s nice to
reduce the number of variables up front.
The Odyssey canoe hulls gave us an ideal starting point for the
project: a lot of interior space in a smooth, lightweight
package. In principle, all we had to do to turn them into
trimarans was attach the Fulmar parts, a task that for a few
exhilarating days was little more than a single line-item on the To-Do
The obvious problem is the physical interface with the crossbeams and
outer hulls, but we also had to make some early decisions about the design waterline (the line that
designers optimistically draw on a boat to demarcate topsides paint
from bottom paint), freeboard
(how far above said waterline the gunwales are, affecting everything
from windage to the dryness of the ride), centers of gravity and buoyancy
(ensuring that the boat tends to float in such a way that the waterline
turns out to be correct), dihedral
(how high the outer hulls should be relative to the center hull to
strike a balance between dragging heavily in the water and tipping
annoyingly from side to side when at rest), and balance
(the overall relationship between stuff that gets blown around by the
wind and stuff that hangs under the boat, ultimately manifesting itself
in the feel of the helm and general sailing performance). In
words, having a pair of canoes in the lab, perched inscrutably on
workstands, failed to reveal an immediate and obvious next step.
at least we had a lot to think about.
||42 pounds, with Kevlar
||0” (bottom flat from
bow to stern)
Wenonah Odyssey Canoe Specifications
Inevitably, much of the noodling that goes on in the early stages of a
design is a bit painful to relate. Basically, it takes the form
of tossing all the variables into the air, juggling them frantically
while studying their interactions and bothering experts with dumb
questions, then confidently congealing all the data into a clear mental
model that just has to be correct—or appears so until the one expert
you were unable to reach finally returns your call and says,
“What? No, no, you can’t do it that way; jeez, who on earth told
you that?” OK, maybe
I’m exaggerating a little,
but I bet if you drag a system architect out to a pub and start the
beer flowing, you will eventually extract the admission that any new
design involves a healthy measure of unquantifiable art and wishful
thinking, stitched together by formal tools and guided by the intuition
gained through a lifetime of design work (all adding up to unshakable
opinions about what’s right). That’s pretty much what happened
here, and in the early phases I depended heavily on others for many of
the marine architecture essentials while my job became one of research,
synthesis, and conflict resolution; essential wizardry at this stage
came from the formidable talent pool of Bob Stuart, John Marples, David
Berkstresser, Gino Morrelli, Greg Jacobs, Mark Reynolds, Jim Antrim,
Andrew Letton, and a few others.
With such cognoscenti contributing ideas, how could we possibly go
Gunwales and Bellies
It was obvious from the beginning that the center hull would need more
freeboard than was provided by the stock canoe, so we decided to make
the boat 2” taller all the way around. This adds internal volume
and makes for a drier ride; it has nothing to do with the waterline or
You can see the details of this and some of the other “first steps” in
Figure 2. Up near the bow in the photo, Bob Stuart is trying to
establish a vertical line for the placement of the mast step (getting a
level reference plane is a real pain in a boat, because everything is
curved). In the foreground there is a molded aka nest resting atop the aft
bulkhead, with one of the crossbeams nestled inside. We’ll
discuss this in the next section.
2: The first steps in canoe-hacking—bulkheads, molded aka nests,
and gunwale extensions.
Along the top edge of the boat there is evidence of a bit of
surgery in progress, detailed in the drawing of Figure 3. When
the canoe arrived in the lab, the rim of the hull ended with the little
square cross-section labeled “original wood gunwale”—less finished than
would normally be the case, as we knew we were going to hack it
anyway. The single-layer wall below that is a thin layup of
Kevlar plus an external gelcoat layer (a tough pigment). Every
two feet there is a stiffening rib of foam-core material that curves
from the gunwale down to join the canoe floor, which similarly consists
of two skins separated by a thin layer of foam. The net effect is
a nice balance of lightness and rigidity, and we tied into it with all
of our subsequent construction.
In Figure 3, we are looking edge-on at our new additions to the
gunwales. Below the original wood, we glued in a tapered piece of
foam (ripped on a table saw) to allow our added fiberglass cloth to lay
smoothly along the hull, as it refuses to bend around sharp
corners. Above the wood, there is a 2-inch wide strip of foam,
and directly to this is glued the deck, made of identical stuff.
Where these two pieces meet (at slightly less than a 90° angle,
given the slight crown of the deck for drainage, stiffness, and
aesthetics), we sanded the outer corner to a gentle radius and, inside,
added a fillet of thickened epoxy with the consistency of peanut
butter. At this point, all we had to do to make it strong was cut some
pieces of fiberglass cloth, lay them on all the surfaces, and squeegee
on the epoxy. (A more detailed discussion of working with these
materials, as well as some commentary about the facilities required,
may be found elsewhere in this article collection: "Basic Composite Fabrication")
3: Detail of hull-deck structure and “gunwale extensions” that make the
whole boat two inches taller. 1/2” foam is shaped and glued to
form the desired shape, then covered with fiberglass and epoxy.
4: View inside the bow compartment, showing hull-deck
The internal view of the resulting structure is shown in Figure 4,
looking forward from inside the front hatch. There are actually a
number of details revealed here. Beginning up at the deck
(ignoring the hardware and black hydraulic line—that’s part of the
landing-gear steering assembly), you can see distinct levels as you
move down along the sides of the hull. Starting at the horizontal
underside of the deck, there is that 2” tall strip of foam, then the
original wood rim, then a different color of foam used for the tapered
part. Why different foam? As with most materials in this
business, there are lots of options; here, we had less need for
compressive strength so we used a lighter material to save a few
ounces. The final stratum visible is the overlap of fiberglass
cloth onto the original hull material.
Incidentally, those two wooden strips on the sides of the hull are for
added stiffness—we were concerned that sailing would subject the boat
to much heavier cyclic abuse than originally intended, and these reduce
any tendency that the large flat surfaces might have to flex (or
“oilcan”) in response to waves. Also, in the foreground of the
photo, you can see one of the foam-core stiffening ribs I mentioned
At this point, we have a canoe that’s 2” taller than before, and have
also established how the deck is integrated with the hull. If we
were simply closing an open boat and adding a few compartments for gear
storage, we’d be nearly there... but this is a Microship, which
obviates simplicity. A simple decked-over hull with access
hatches is fine for the bow and stern segments, but the region between the bulkheads is a
Here, we have to accommodate a gadget-happy human with as much space as
possible, provide horizontal surfaces in the cockpit for armrests and
controls, support the equipment console, install the retractable seat
and other essential fixtures, allow room to sleep, and somehow segue
into vertical walls that provide inboard support for solar
panels. All these needs are addressed by the structure shown
schematically in Figure 5, which became known as the gunwale belly.
5: Cross-sectional view of gunwale belly structure.
Starting from the bottom, we see the same structure that appeared in
the basic bow and stern sections—the pair of foam strips that add 2” of
height and let fiberglass cloth lay nicely against the hull. But
instead of merging into a simple deck, these now tee into long curved
foam sections, running the full eight feet between bulkheads.
After considerable experimentation, we discovered that the Divinycell
core material will easily take simple curves through a carefully
calibrated thermal process involving industrial electric strip heaters
and a bending jig of 4” PVC tubing to provide a consistent
radius. In retrospect, it would probably have been better to bend
longer sections at once than we did, as the minor variations in the
process translated into a lot of sanding and filling later, but such is
the nature of prototypes.
You can see the results in Figure 6. In the foreground is the
opening for the aft gear hatch, and the gunwale bellies adjacent to
that are thicker than the rest—2 inches, to be exact. These are
the “roots” of the arch structure to be added later, providing support
for a fabric enclosure reminiscent of an automotive convertible top, as
well as mounting space for all sorts of essential equipment. The
foam triangles between the arch roots and the hatch opening will
provide surfaces for the electric thruster (port) and the anchor
(starboard); the different foam color, as before, is because we didn’t
need much compressive strength.
Just forward of all that is the aft aka nest, and as that’s the subject
of the next section I won’t say anything about it here.
Continuing in the same direction, we come to the cockpit area itself—a
huge opening flanked by those segmented gunwale bellies (still raw
Divinycell foam, not yet fiberglassed. Now you can start to see
what they’re good for: once the seat is installed, these
horizontal surfaces, or decklets,
end up becoming a significant part of my immediate environment, much
easier on the arms than the original thin canoe gunwales. The big
rectangular hole on the starboard side will become part of the trunk
that houses the pedal drive unit.
6: The gunwale bellies and other deck parts freshly attached to the
boat, before fiberglassing. In the foreground is the aft hatch
Note the horizontal flat section just forward of the open cockpit
space. This is the floor of the equipment console area, which
will be packed with computers and communications gear. Just below
it, you can see the forward bulkhead (where the battery box will go),
and the last visible feature before we reach the limits of the cheesy
flash on that clunky first-generation 640x480 digital camera is the
forward aka nest. If you squint at the picture just right, you
can also see a black object that appears to be atop that—that’s the
mast step, which we’ll get to shortly.
It’s funny… it all seems to go so quickly when I write about it like
this. One might be tempted to conclude that construction
proceeded just as smoothly. But in these early stages, we were
faced with the problem of accommodating all future needs, some of which
had barely been articulated. While certain features were defined
by the chosen hulls and crossbeams, we were still vague on a few
details; all I can say is that it’s a good thing fiberglass and foam
are so editable!
OK, let’s look at those critical hull-crossbeam interface widgets.
The Aka Nests
You’ve seen them already, in Figures 2 and 6. The task here was
to take a pair of curvy crossbeams designed for a small commercial
trimaran, and somehow graft them onto a canoe. There are no
off-the-shelf brackets that do this, and crudely bolting them on
without thinking about stress distribution would be asking for
premature failure. The solution was to mold custom nests.
The crossbeams from the Fulmar are U-sections,
meaning that they are open at the bottom (you can see one if you
peek ahead at Figure 8). To mold a perfectly mating shape, we had
to box them in with something flexible, yet stiff and smooth—scrounged
Formica countertop laminate from the dumpster of a nearby cabinet shop
turned out to be perfect. We simply cut strips on the table saw
and hot-glued them to the crossbeams, as shown in the cross-sectional
drawing of Figure 7.
7: The mold used to fabricate the aka nests is made with waxed
Formica countertop material hot-glued around the original crossbeams.
For this to work as a fiberglass mold, there are a few
requirements. First, since the fabric will absolutely refuse to
wrap around square corners, it is necessary to radius the outside
corners and fillet the inside ones. We carved the radius with a
laminate trimmer (basically an agile little router), and immediately
ran into the problem of removing so much of the thin Formica material
that our glue joints started to fail. We changed to a tighter
radius and got it to work with more aggressive gluing, realized that at
least the first few fiberglass layers would have to be on the bias
(with the weave at a 45-degree angle to the edge, allowing it to make a
sharper bend). The fillets were easy—filled epoxy applied with a
tongue depressor and sanded smooth. Finally, the whole
contraption was given a few coats of mold-release wax, ensuring that
the new layup would not become a permanent part of the crossbeam… we do need these to be removable!
Adding cloth is time-consuming but straightforward. Each nest was
given 6 layers of 10-ounce cloth, yielding a final thickness of about
.060”. (Additional strength would be added where needed later,
during integration with the boat.) We kept the process flowing,
allowing each layer to gel a bit before adding the next, thus ensuring
a good chemical bond.
After final cure, we popped the parts off the molds, a process that is
always, for some reason, incredibly satisfying. The waxed Formica
surface left a very smooth interior finish, and all that remained was
cleanup of the ragged edges prior to bonding them to the hull.
Somewhere in here, a rather large question arose: where, exactly,
do these things go? Their distance apart was defined by the
existing Fulmar aka/ama assembly, of course, but the variables included
fore-aft placement of the whole affair, height above waterline, and
amount of pitch-axis tilt relative to the center hull. This
called for many hours of staring, sketching, and calling experts; we
finally concluded that it should go, yes, right about here. As
with many such decisions, what looked and felt like a SWAG (scientific
wild-ass guess) was actually built upon a lot of research, but this was
one of those areas where verbal explanations from marine architects
carried more weight than objective measurement of waterplane areas and
angles of attack.
The nests were glued in place using the whole aka/ama assembly as a
fixturing aid, then gradually accumulated layers of fiberglass that
rendered them permanent parts of the boat. The only remaining issue was
the attachment method that would allow easy removal of the crossbeams.
8: The akas are held in their nests by two bolts on each side.
This view is the underside of the aft crossbeam, starboard side.
If you think about the “load case analysis,” it’s clear that across
most of the nest there is actually very little stress. The real
action happens where the crossbeams meet the hull, and almost all of
that stress occurs when the boat is fighting heeling forces from the
wind in the sail (the wind is often doing its best to push sailboats
over, and a trimaran fights this influence through the buoyancy of its
outer hulls instead of the mass of a keel). While this is
happening on one side, the other is just supporting the weight of the
outer hull, insignificant by comparison. In other words, we
really need to be able to deal with high intermittent tension
loads. This all translates into 3/8” stainless bolts bonded into
a relatively incompressible wood-core substrate well-glassed to the
surrounding structures, poking through the top of the crossbeam, and
captured with acorn nuts along with something to distribute the load
and avoid crushing glass fibers. You can see the seamy underside
of all this in Figure 8, and a much sexier top view in Figure 9.
There comes a point in boatbuilding whereon the vessel starts to appear
as one lovely thing instead of thousands of bits of foam and glass all
glued together in a patchwork of multicolored fillers and
epoxies. We’re not there yet in this discussion, of course, but
this photograph should give us hope.
9: Fast-forward to a much later stage of completion. Note
the aka bolts behind the pondering author, with the load distributed
across black-anodized aluminum plates. The finished gunwale
bellies are also visible, supporting extensive hardware fixturing.
Since we have the luxury of Figure 9 to look at, let’s talk for a
moment about that distinctive square structure behind the seat. As
Microship design progressed, it became ever more apparent that there
would have to be a way to define an enclosed cockpit space more
substantially than with a rickety folding frame of metal tubing, as is
often used to support the fabric dodger
or bimini on small cruising
vessels. A decent integrated structure would offer a lot of
advantages: mounting space for cockpit fixtures (you can just
barely see the face of the Marine VHF radio in the photo), support for
an antenna and radar reflector as well as the sternlight, and—perhaps
most significantly—a substrate for the traveler that allows the point at
which the boom is sheeted to the boat to be moved from side to side,
giving more control over sail shape and angle to the wind. The
traveler is the horizontal rail-like object atop the arch, and that
wonderfully arcane vertical thing in the foreground is a dual-band
J-pole antenna for amateur radio.
From a fiberglass perspective, the arch is a direct outgrowth of the
deck, though we used a very lightweight blue insulation foam, sculpted
it into a pretty shape, and laid on the glass. In retrospect, we
probably should have chosen a proper structural foam like lower density
Divinycell, for the cheap home-improvement stuff crumbles and cracks at
the slightest provocation, making subsequent thread-casting and other
retrofit jobs a pain.
Near the bottom of the arch, you can see a little horizontal step with
a pin sticking up; that’s part of the solar array mounting system.
Decks and Hatches
During our discussion of gunwales and bellies, we saw how the half-inch
foam core was glued at an almost-right angle, then rounded, filleted,
and glassed over to make a smooth hull-deck seam. It’s only
simple at the forward and aft ends of the boat (about five feet each),
but these are very critical areas for mounting surfaces, aesthetics,
and the gear hatches. Where else, on this tiny vessel, would I
put all my junk?
10: The center hull on its rolling workstand (outdoor dust-generation
is always preferable to the alternative). Foredeck and hatch
opening are clearly visible, as are aka nests, bellies, and main
To achieve a nicely crowned deck, a big flat piece of stock Divinycell
foam was constrained in a fixture to induce a simple curve, then
glassed on both sides. The tensile strength of the fiberglass is
more than enough to retain the shape with just a wee bit of
spring-back, so no thermal bending was necessary (unlike the extreme
curves of the bellies). Segments of this were then cut out to
create the foredeck and afterdeck surfaces, and the hatch covers were
made of the pieces left over from carefully cutting the openings that
they would cover. There’s a good view of this in Figure 10, which
documents one of those long days of sanding, sanding, endlessly sanding.
We spent a long time pondering the hatches, addressing both the basic
practicality of providing useful stowage space and the rather daunting
problem of keeping the contents dry even when green water aggressively
hammers the foredeck while I’m out there flirting with death instead of
spending a storm day safely in camp. I confess that I was tempted
by off-the-shelf “opening ports” from the marine supply world, but they
are heavy, expensive, and the wrong shape. Most are also designed
to be opened from the inside, as apparently, on some boats, there is
actually enough room to move around below. Fortunately, I was
talked out of this by Bob Stuart, who is less intimated by tricky
fiberglass projects than am I.
11: Detail of hatch cover interface. Dark rectangle is
On Wordplay, the hatch covers
are deceptively simple. The opening in the deck has a flange that
projects upward all the way around the cutout, forming a coaming. To create this, a
strip of newspaper was soaked with epoxy, allowed to stiffen but not
fully cure, then wrapped around the raw edge of the hole. Once
this solidified, it formed a tidy little core for the continuation of
both top and bottom layers of fiberglass covering the deck. You
can see a cross-sectional sketch of this in Figure 11, and Figure 12 is
a shot of the result—showing both the coaming and the flanged hatch
cover, tethered to the boat. These index nicely together, of
course, leaving only the problem of waterproofing. The geometry itself
sheds falling water just fine, but breaking waves are another
matter. The black ring around the hatch cover is a simple
glued-on gasket of neoprene, which makes a surprisingly good seal when
mated with the sharp edge of the deck flange.
Unfortunately, this still doesn’t finish the job. Something has
to hold the hatch cover down tightly enough to achieve gasket
compression, and this this is accomplished
with the dangling black webbing straps on either side of the hatch opening in Figure
12, or in use in Figure 13.
12: Hatch cover and opening, with mating flanges and neoprene
compression gasket. Note bonded-in tether of Kevlar cord to
prevent loss of the cover at sea.
tubular nylon webbing is sewn to stainless-steel D-rings retained in
deck fixtures, which were fabricated through a rather tricky process of
laying fiberglass “bow ties” over a mold of thin vinyl tubing (later
extracted without difficulty, as epoxy doesn’t stick to such
13: Forward hatch closed, retained by straps and buckles.
This design is not as convenient to use as I would like; still on the projects list is an
internal hidden hinge along with a remote-release spring latch that maintains
good gasket compression.
In many of the photos seen so far, there has been a visible feature
that I have hardly mentioned: a black tube poking through the
deck just in front of the forward bulkhead. Affectionately known
as the mast urbator, this
accepts the 21-foot freestanding WindRider 16 sail rig, which is then free
to rotate on its Delrin bearings to allow furling.
The primary requirement in this area is brute strength. If you
think about what’s happening in a high wind where all the transient and
static loads are concentrated, it’s clear that this has to be one of
the strongest places on the whole boat—and it’s no coincidence that
this, the forward bulkhead, the aka nest, and the landing gear are all
bonded securely into a single structure. The mast step is shown
in Figure 15, viewed from inside the forward hatch.
The unit itself began life as a chunk of aluminum tubing with 3” inside
diameter and 1/8” wall thickness. Since this was to be in a nasty
environment and a partner in
a bearing relationship, we wanted it corrosion-proof and
slippery. This called for a special form of anodizing that goes
beyond the normal conversion coating used to increase corrosion
resistance—this process embeds Teflon in the surface, yielding an
incredibly low coefficient of friction, the hardness of steel, and
excellent abrasion resistance. Typified by the Tufram process from General
Magnaplate, this is used in industry where lightweight parts are
to replace those of case-hardened steel, but without giving up the
desirable surface characteristics.
15: The mast step is a Teflon-anodized aluminum tube bonded
securely into the hull just in front of the forward bulkhead.
Once we had the part on hand, the task was to fixture it into the boat
in such a way that the mast would stand perfectly vertical. In an
environment of curves and and imperfections, this involves standing
back with a funny squinting expression, mumbling over bubble levels and
tape measures, and wondering how something that looks so right can
measure so wrong (and vice versa).
In the photo, you can see the massive layup that integrates this unit
into the hull. We ground the fancy anodizing off the tubing where
it would have to take epoxy, then subjected it to an aluminum-etch
process to allow a proper chemical bond to the surface. The
fiberglass is in layers, each slightly larger than the last to provide
graduated load distribution without any stress-risers. (If there is a sharp
boundary between two objects that are enjoying cyclic stress relative
to each other, fracture will occur at that spot. This can be
generalized to the advice that one should avoid square corners in just
about any system subject to flexion, because that is where failure will
eventually take place.) Here, we cut out a dozen or so circles of
fiberglass cloth, stepped in increments of about half an inch.
The result is a smooth transition between the rigid mast step and the
tough but flexible hull.
A few details are worth noting here. A vertical tube stuck in a
boat is going to fill up with water, so a drainhole was molded into
place through the bulkhead into the main compartment. The
rationale is that the cockpit is generally wet and has a bilge pump,
while the forward gear hatch should stay as dry as possible.
Second, since the mast is going to rotate in this thing, there had to
be something approximating a thrust bearing, however crude. This
took the form of an epoxy-sealed chunk of wood with a hard plastic
surface screwed (with recessed flat-heads) on top. This just
rests in the bottom of the urbator, and it has a couple of protruding
screws to allow easy removal with a loop of string.
In the photo, there are a couple of other features that might arouse
curiosity. The white flexible tube emerging from the plywood
bulkhead carries a bundle of hydraulic lines as well as a coaxial cable
to the VHF antenna on the bow. The cable on the other side is for
the navlights and serial data stream from the ultrasonic wind
sensor. And the little disc in the upper right corner is a
talisman that has accompanied me 17,000 miles around the US via
bicycle—a St. Christopher medal given to me by a lady in Key Largo,
Florida after some rednecks just about killed me. (I’m not
Catholic, but you know... it’s not really about that, is it?)
For this part to make sense, I should say something else about how
sailboats work. To do anything other than coast downwind with the
wind astern, a boat needs a way to provide lateral resistance to moving
sideways through the water. Given this, the aerodynamic lift
provided by a well-designed suit of sails can propel the boat through a
very wide range of angles—not directly into the wind, of course, but
surprisingly close. 45 degrees is not uncommon.
A monohull takes advantage of its keel to accomplish this; that hunk of
lead is more than just a big counterweight to keep the boat from
blowing over. But if we have a multihull (or a beachable dinghy,
or even a sailboard), we have to provide lateral resistance some other
way. This typically involves a retractable board, foil-shaped to
minimize turbulence, mounted at an appropriate spot in the hull.
Some boats use leeboards that pivot down outside the hull, accepting
the noise and drag of a “surface-piercing foil” in exchange for
simplicity and minimal impact on usable space aboard. Others go
for greater efficiency with a centerboard that deploys from an internal
trunk, but these eat up precious internal space and can fail
catastrophically in a grounding.
In the Microships, we elected to try a quirky compromise in the form of
a retractable daggerboard that slides through a trunk at the turn of
the bilge—leaving the center of the tiny hull free for sleeping and
pedaling while avoiding the splashes and general clunkiness of a
leeboard. Take a look at Figure 16.
16: Microship daggerboard is forward-angled to increase the
probability of harmlessly kicking up in a grounding. The bow is
to the left, and that little fin in the lower right is part of the
pedal-drive unit over on the starboard side.
The weirdest thing about this, at first glance, is the fact that it is
angled forward. This was not some dumb mistake from pulling a
bleary all-nighter; it was calculated to avoid damage when I plow into
something. Assuming the boat is moving mostly forward (not always
the case, but one can hope), then the board will just pop up instead of
attempting to pivot aft, knifing through the hull and turning an oops moment into a potential
To facilitiate this, we did a little trick to minimize friction.
One of the more wondrous materials available from the McMaster-Carr
catalog is bondable Teflon,
chemically treated on one side in a way that makes the ultra-slick PTFE
plastic accept epoxy. As far as I know, the only explanation for
this is “magic,” but then, I’m not a chemist. In any case, it
works beautifully, and whenever we needed tough slippery spots on the
boat we just lopped off a suitable chunk of this stuff and glued it
on. The trunk, which was molded of fiberglass around the recycled
(and heavy) daggerboard from an old Nacra beach catamaran, now has
little Teflon inserts in all four corners, and the sliding action is
Normally, of course, I try not to depend on hitting bottom as a way of
raising the appendages. Another nice feature of the
forward-angled trunk is enhanced usability: I can raise the board
with one hand and park it in a little notch on the cowling. The
cockpit perspective on all this is in Figure 17, which shows the dagger
retracted, hoisted by a handle made of 1/4” braided line and a scrap of
tubular nylon webbing.
17: View of daggerboard and its trunk from inside the cockpit
(circa late 2001; no console electronics yet).
The trunk itself is simply glassed into the hull and deck, providing a
very stable structure that, like everything on the boat, ends up
becoming a mounting surface for something else. That complicated
hydraulic assembly is the rudder deployment system, and the gap between
trunk and hull provides a nice place to tuck the spare paddle.
So much for the basic trunk fabrication... but there’s one critical
issue we haven’t mentioned. How did we know where to put this
thing? Does it really matter?
As it turns out, placement is absolutely critical. One of the
many delicate balancing acts involved in sailboat design is the
relationship between the center of
effort (CE) and the center of
lateral resistance (CLR). Screw this up, and the boat will
become hard to handle, inefficient, and possibly even dangerous.
CE can be viewed as the resultant center of all the wind’s effects on
anything above waterline. Obviously, this is mostly about the
sail and is thus a function of conditions, but it is also significantly
affected by the topsides, the arch, whether or not the dodger is
deployed, laundry flapping from the antennas, courtesy flags and
burgees ... whatever. Somewhere up in the air over the console is
a magic point that represents a big celestial finger pushing on the
Similarly, CLR is the resultant of all the stuff below waterline and
the drag it presents to sideways motion. Some things, like the
daggerboard, are specifically designed to do this effectively, but the
tendency to slip to leeward is also affected by hull shapes and the
presence or absence of the pedal drive and electric thruster. The
rudder is also a huge factor, but we don’t have much choice about where
to put it. Daggerboard placement is essentially the only variable
that doesn’t involve a lot of extra work.
Why does it matter? Picture this: if the CE is way forward
of the CLR, then the boat will always try to “fall off” the wind, or
turn away from the applied force and run downwind. Such lee helm can be pathological,
because if you are trying to head as close to the wind as possible and
for some reason (including inattention) lose rudder control, the boat
will turn in such a way that the heeling forces get abruptly
higher—stressing the rig and crossbeams, and, in extreme conditions,
increasing the possibility of capsize. You don’t want a sneeze or
a broken rudder fitting to dump you into a dangerous situation.
Conversely, if the CE is aft of the CLR, letting go of the steering
will cause the boat to turn into the wind as the stern is pushed around
that virtual pivot point... whereupon the sail will start flogging and
you end up dead in the water, in
irons. That may be embarrassing, but it beats
hypothermia. It might seem that one would want the CE directly
above the CLR, but it turns out that a little bit of this weather helm is a good feature—you
can de-power without any difficulty, and turning through the wind
(tacking) is easier. Of course, you don’t want the CE to be too
far aft of the CLR, or you’ll burn out your arm muscles trying to fight
the rudder to maintain a heading.
Some hard-core race boats actually allow the centerboard to be tuned,
tilting fore and aft and in some cases even angled relative to
centerline, trying to extract that extra 1/10 knot of boat speed.
I’m not that devoted to performance; I just want it to work reasonably
well in a variety of conditions (and not break). This was another
area where we ended up integrating the advice of a lot of marine
architects, taking measurements, doing calculations, and constructing
an intuition that eventually allowed us to switch from pencils to
Sharpies—then fire up the jigsaw to rip a long ugly hole in the
beautiful Kevlar hull. The scary thing about all this is that
there was essentially no way to test it until a huge amount of
additional work was done and the stakes had become significant.
Fortunately, it came out just about right, although in a heavy wind
there’s a bit more weather helm (tendency to head up) than I would
like—and I finally figured out why. It is conventional wisdom
among yacht designers to place the CE slightly forward of the CLR in
steady state conditions… knowing that the effective CE will move aft
when the boat heels. I figured that since “multihulls sail flat,”
I didn’t need to take this compensatory step, and being wary of the
dangers of lee helm I established the static CE/CLR relationship the
way I wanted it to be under dynamic conditions. But in practice,
it turns out that the phenomenon of the CE moving aft is due to mast
turbulence and sail inefficiencies, and those affect a multihull just
as they do a monohull. The net effect is more arm strain holding the
boat off the wind when conditions are intense.
That does beat the alternative, however, and it is somewhat tweakable
by adjusting a few variables (deploying a thruster, dropping the
dodger, furling the sail slightly, or partially retracting the board).
OK, I think we’ve pretty well completed our brief tour of the center
hull. Let’s take a quick look at the crossbeams and outer
hulls... after a few quick book recommendations. These have all
been very useful in the
design of this craft:
Aka and Amas
As I mentioned, we managed to save a huge amount of work by starting
with an existing assembly of crossbeams and outer hulls made for the
Fulmar-19 trimaran. This was familiar territory, as I had owned
one in the early years of the project—all we had to do was make the
Microship hull design backward-compatible with legacy components.
A good overall view of the boat, uncomplicated by landing gear and
other added complexity, may be seen in Figure 18. This was the
first test sail, taking place before a friendly crowd at the 1998 Sea
Kayak Symposium in Port Townsend, Washington. I remember
thinking, “Alright! She sails; we’re almost done. The
expedition will launch next Spring!” <sigh>
18: First Microship test sail, showing aka/ama assembly as well as
other basic hull features.
Notice in this photo that the outer hulls kiss the water rather
lightly—this was intended, and it was a great relief to see that we got
the dihedral about right. Actually, she sits quite a bit lower in
the water once stuffed full of heavy touring gear and geek necessities,
so the self-congratulation was premature. The goal is to achieve
a balance: the less ama immersion, the less hydrodynamic drag
from wetted surface, but if one hull is always “flying” to maximize
speed, then at rest the boat will rock back and forth in a most
annoying fashion. Racers err on the side of speed and fly a hull
every chance they get, but my objectives are more sedate.
Another thing to notice is the curve of the akas (the crossbeams),
keeping them as high above the water as possible to minimize
interaction with waves. These pretty shapes don’t lend themselves
to solar panel mounting very well, but it turns out that it’s a moot
point anyway—there is so much flexion in the system (a good thing) that
the solar array has to move independently of the outer hulls.
One of the essential features of this assembly, given the plan to add
landing gear and become amphibian for unassisted haulouts and portages,
is the ability to fold. In the original Fulmar, this was strictly
for trailering; nobody in their right mind adds retractable,
hydraulically steered full-suspension landing gear to a canoe!
But as we intended to do exactly that, the folding feature was doubly
interesting, reducing the boat to 6-foot overall width (from the
original 11) when on the road.
19: Aka hinge assembly (without locking pin). Round blob is a red
Figure 19 shows how it works. The aka is split in the middle (in
the photo, the segment on the right is attached to the boat). A
robust pair of anodized aluminum bars forms a simple hinge, pivoting
around the bolt on the far right. When in use on the water, a
stainless steel locking pin is inserted into the empty hole, passing
through both of the bars and a couple of nylon bushings set into the
flanges of the aka U-section. The system is a little fiddly but effective; here you can see the payoff,
with the boat folded for road mode and emerging from Tim Nolan’s garage
in Madison, Wisconsin—bound for a test sail a couple of miles away on Lake Monona.
20: Microship folded and ready to join the commuting throng.
The outer hulls (amas) are simple affairs, with a single screw-on
access hatch for inspection and sponging out any leaks (there have not
been any). I am often asked if I stow gear out there, but no—I
want all the buoyancy I can get and they’d be a pain to reach on the
water anyway. As the loads are smoothly distributed, the
fiberglass layup is light and simple, interfaced to the akas by simple
retaining bolts and molded nests (Figure 21). Under normal
sailing conditions, there is no focused bending moment here as there is
at the junction between the akas and the center hulls—though I do worry
somewhat about careening sideways in a storm into something
unyielding. I guess there are no guarantees in this business.
There are a couple of other things to note in Figure 21. We
originally added that odd flat platform to the stock hulls to provide a
mounting surface for a rather goofy solar array mounting scheme, which
was abandoned during the depressingly familiar window between
fabrication of components and thinking the problem through more
completely. Far from being wasted effort, however, those surfaces
turned out to be a lifesaver when making the journey between cockpit
and dock, over and over, loaded with packs. The stock hull was
useless for this, and as my landing gear prevent use of a normal fabric
trampoline between the hulls, this is actually a difficult problem.
In a somewhat related vein, being tied alongside a dock (as in a marina
slip) subjects the system to additional abuse. People normally
use inflatable cushions to reduce noise and abrasion, but the shape of
these tiny hulls makes such fenders ineffective—they float up, move
around, and otherwise do all they can to avoid being useful.
If you look closely at the photo, you can see part of the
solution: a black rubber extrusion made to cushion
tractor-trailer rigs backing up to loading docks.
21: Simple connection between crossbeams and outer hulls.
On Songline, we used a much
softer marine product called Gunnel-Guard, which was clearly superior
in performance. But in this application, the aesthetics tipped the scales: concerned about white
Dacron picking up dock creosote (which indeed it does), I opted for
this solution… and then paid for it on the first mini-expedition by
having to endure a continuous thunk… thunk… in windy marina conditions. I finally discovered that a flat
chunk of foam, like a child’s life jacket, can be lashed in place to
solve the problem. But this violates the fundamental rule
concerning random loose objects that have to be stowed and deployed,
so a more integrated solution is needed, right up there on the to-do
list with emergency deployable wheel chocks and the ability to sprout a
service stand to allow landing gear maintenance.
22: The view inside an ama.
A few glitches notwithstanding, we’re finally on our way—the basic
Microship substrate exists. In our next article of
this series, we'll explore the surprisingly robust sail rig and a few
other essential features that turn this into a proper micro-yacht.
23: LAD (Lego-Aided Design) model by Pender, age 7, who visited
the lab with his dad one afternoon, quietly contemplated multihull
marine architecture while the adults nattered on endlessly about boring
geek stuff, then went home and built this.
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Some of the essential magazines that feed the imagination during a
marathon boatbuilding project: