The Stated Requirements
The client stated the following:
"I seek a marine
mobile home primarily for long-term island/harbor hopping in the Western
Pacific and the rivers of China, but capable of occasional long ocean
passages.
My wife has three requirements:
A lounge / house with a view
Galley with a view
Emergency sailing capability
The galley should be large enough for everyday living, the head (one
is enough) should have a separate shower, not a grate below the toilet.
My list includes lots of storage, a well equipped shop, and an
office/computer/study area. It would be good if settees were long
enough to serve as guest berths in port.
There is no need to think too hard about an emergency sail.
Indonesian trimarans routinely use rectangular sails on near-vertical
yards hung from short masts. They could be awnings with the
necessary fittings added. I prefer simple mechanical systems that
I can fix myself, except for communications and navigation gear.
I have few preconceived notions about layout. I have done a lot
of sketching, and the trimaran configuration is so narrow that there are
really not all that many options for layout unless it has a wide topside
blister or the length exceeds 60 feet, and 60 feet is already a hard
boat to manage in port. Too much beam hanging out above the
waterline looks funny, and may preclude trucking. I am open to all
suggestions including a catamaran that does not break the budget.
Materials. I like unpainted aluminum a la Northwest
fishing boats, but given that construction will be in the Philippines, I
think materials are confined by cost to sheathed strip planking and/or
ply.
Appearance. I actually like 'spaceships' that look like the
ILAN Voyager and Cable & Wireless, but for this vessel I prefer a more
traditional looking boat in order to find better acceptance in
third world ports. At a minimum, the boat should be
designed to accept routine bashing about in rough ports.
Except for the local fishing boats however, it is not clear what
"traditional looking" will actually be for such a craft as this, given
that the concept is most certainly not traditional...!"
The Resulting Design Sketch
On the face of it, a somewhat bizarre request; a tough
assignment, at best: Come up with a "traditional looking"
trimaran...? Well, the result is certainly that. It
would fit in well in any Asian port, and also would not be out of place among trawler
yachts in a
Western port. It is perhaps somewhat in the Wharram "tradition"
though the hull form is quite different from those craft, and is combined with a pilot house that any trawler would be proud of.
Is the result strange? I think not -- it is instead quite a
neat little ship!
To fit a sail rig would be quite easy, and if primarily used as an
"emergency" get-home affair, it could easily be a
Chinese Junk type of schooner to
keep the rig low.
For get-home sailing, one would presume dagger-boards or centerboards
arranged to not interfere with the accommodations. Mast placement
is always problematic to the interior of a vessel, so in this case, they
would probably be deck stepped, and in that way could be made to easily
be lowered.
The "Sitting room with a view" is accomplished in the Pilot House, with
a wide settee facing forward. A table forward of the settee allows meals to be taken there for a good view of the harbor.
Another larger settee and table arrangement below provides privacy for evening
dining as well.
The requirement for "a galley with a view" is well
met in my view, since the galley is located centrally below the fore deck,
and is of a generous size. As for the view, it would be quite
good. The galley is forward of the amas, so they would not be an
interference. The fore-deck spans the full width of the ship,
extending from bulwark to bulwark athwartships, and from the pilot
house, all the way forward until the anchor well is reached at the bow.
With generous ports within the bulwark outboard of the galley, plus
several good sky lights, all requirements are met.
An alternate location for the galley would of course be to lengthen
the pilot house, and place the galley within it. In spite of the
excellent view from there, this arrangement has multiple disadvantages.
It would raise the center of gravity of the main hull due to the longer
pilot house; it would locate more weight aft (already pushing the
limits); it would place a lot of activity in the piloting area, always a
disadvantage; and it would make food preparation underway during the
night watch somewhat of a risk to the helmsman's night vision. For
a true voyaging vessel, the piloting area is best reserved for just
that, and for comfortable lounging while at sea or in harbor.
Below, forward of the settee are a pair of office-like desks with swivel chairs.
Below aft, there is a generous shower to starb'd, and a large head to port.
Right forward is a very spacious double berth with a big
shelf / locker forward of that. Farther forward yet is the fo'c's'l locker
to house the anchor rode.
In order to achieve any sort of meaningful 'shop-space' the vessel would
either have to become longer, or one of the interior spaces would have
to serve multiple purposes. For example, if it could be tolerated
to locate the shower within the head compartment to port,
one could then dedicate the starb'd compartment to being a shop-space,
or possibly an office, or even an extra guest cabin...
Naturally, in such a long and narrow living space, the width of sole
is very restricted. One can raise up the sole in the outboard
areas if it is needed, and then arrange for comfortable seating for
whatever task is contemplated, whether this be a shop area, shower,
office, or what have you.
On the Exterior, one could arrange a nice wrap around seat at the
stern and maybe a BBQ / bar on the aft face of the pilot house on either
side of the 'stack.' There is plenty of foredeck area for sun bathing,
and with a mast and boom there, one can easily arrange an awning for a bit of shade...
Though not illustrated in the above-linked drawings, there could be a
'trampoline' net arranged between the main hull and the amas, extending
from the forward beam to the aft beam... a great place to hang out under
way...
The amas themselves are quite small, and should be kept water tight
with a secure hatch. Each could become a small 'kid's cabin' and
they would have their own 'private vessel' to command...
Alternately, though it is best to keep them as light as possible, they
could be used for light weight storage, say for fenders, lines, sails,
etc.
Materials of Construction
The 'design-study' budget for this vessel was limited in the
extreme, therefore the vessel's name (and its implied meaning).
Therefore 'Pennywise' remains a prototype design awaiting a more
qualified owner to pursue the remaining drawings, design calcs, propulsion
and resistance calcs, etc.
Even so, given the type of vessel in question we can say a few
things definitively:
Building a vessel of this type in steel would be
completely out of the question.
Aluminum alloy would be an excellent choice for the
hulls, the decks, the pilot house structures, and for the
cross beams. If built in aluminum and NC cut, the building
of the hulls would be very quickly achieved.
Plywood is certainly a quick method of construction, and
if covered using a composite resin / laminate, there would
be very good strength, lightness of structure, and
ease of general maintenance.
Cored FRP construction does offer several advantages,
among them strength, longevity and freedom from general
maintenance. Naturally, FRP construction of any type will be
much more costly in terms of materials than any other type,
particularly if construction were to be in a remote part of
the world.
In order to achieve the best laminate quality, we prefer vinyl ester resin or epoxy resin. With these, the logical
fabric would be Kevlar or another high strength fiber such
as E-glass or S-glass. There is little point with a
cruising vessel to use high-cost exotic fibers however such as carbon
fiber. While light and stiff, carbon fiber is quite
expensive, thus it is ordinarily ruled out for this kind
of boat.
A very light weight interior would be quite important as well. For
this, we specify the use of honeycomb panels for the joinery flats
wherever it is practical and easy to do so. One such material
brand is Nida-Core, possibly the most cost effective among the HC
panels. Nida Core panels have thin plywood skins bonded to a
phenolic resin honeycomb core. This produces very stiff and light weight interior joinery
with more or less the same labor cost as with standard plywood
construction.
Ideally the struts / cross-beams would be laminated wood, and would be
tapered. If the hulls were all plywood, construction would be very
fast. In that case we could detail all the sheets for NC Cutting by a 2-axis router. For maximum
construction speed and the least number of man-hours we could make use of the "stitch and glue" method of
hull construction. This would allow eliminating many of the heavy
carlins and chine logs common to traditional plywood construction. Each hull could be
quickly built upside down until the deck is reached, then turned over.
If built in cored glass, the mould would be simple to build using
flat pressed board panels, and would of course be built upright.
To detail the mould for NC cutting would be quite easy... we would
simply put the 'structure' of the mould on the outside of the hull
surfaces rather than on the inside...! The result would be a
'mould kit' which would quickly snap together.
Hull Form
The hull is a simple single chine type in order to provide the
ultimate flexibility in choice of construction materials. The
general shape is a V-bottom on all hulls, using a shape somewhat
reminiscent of the US east coast sharpies. The transoms are all arranged
to be similar to the sharpie's fantail stern, and with a brief little
"kick" upward at the stern. The prominent bow is a tribute
to the possibility that this may be an Asian built vessel. With a
junk rig, all the more fitting.
Of course the amas (the outer hulls) would not be deep in the water.
Opinion varies quite widely on this, with some even advocating that amas
be completely clear of the water with the vessel upright. In my
view, the amas' hulls should just "kiss" the water when at rest with the
vessel in an average load condition. This would immerse the keels
on each ama, so they would never be entirely free of the water unless a
sail rig were provided and the vessel were under a press of sail.
A monohull or a power catamaran can be designed to carry enormous
cargo, however a trimaran cannot tolerate being overly burdened with the
accretion of extra weight (most cruising vessels seem to suffer from
this...!).
Vigilance will therefore be required in order to preserve the inherently
excellent performance that such a vessel has to offer.
Opinion is also divided on the best fore and aft location for the
amas. In this case, the amas have been located quite far aft so
that they can provide added buoyancy where it is needed most, due to the
weight of engines and PH, etc. The aft location will help minimize
any tendency to trip, and will provide the maximum in terms of tracking
ability. In the aft location, the amas will also help the stern of
the vessel resist squatting at speed.
Naturally, if sailing ability were to receive greater emphasis the
amas would be located farther forward. The amas would not be moved
beyond amidships however, as that would introduce the potential for
tripping as well as possible steering anomalies.
The amas need to be as light as possible, so fuel and water can not
be located there. Still, the amas need not be empty... The amas
are 26' long by 3' 9" wide, so a perfectly comfortable berth could be
placed into each ama with room to spare, making each one a little
microcosm for young sailors... A little water tight combo
house-companionway for observing the ocean... very nice indeed!
I have modeled the hull and house as drawn, and I've also modeled the
house with considerably less "saddle" shape. Please see the links
above for images of the hull model.
Power
The trimaran allows the use of an efficient single engine
and there is no need for roll attenuation devices. A long
slender hull is the very ultimate in terms of efficiency.
Power would be via a diesel engine located below the Pilot House in
the main hull. Overall, all systems must be kept as light as
possible. Therefore, one can presume there would be a single engine of
modest size to adequately drive the boat; that there
would be no generator per se, and instead a very adequate 12v DC system
would serve electrical needs;
that tankage would be kept to the minimum; and that construction
materials would be as light as possible.
If very long range were a requirement, then emphasis could be placed
on the vessel's sailing ability, for which purpose as mentioned the
Chinese Junk rig would be an ideal choice. If that were chosen, the
rig would likely be similar to that shown on our
50' Renegade. A sail rig would offer the ultimate in terms of
range, get-home power, and the fun of sailing...
For the Penny Wise, if built very lightly as intended (around 26k to
28k lb. total in the light load condition), power could be in the range
of around 65 - 70 hp, and that would attain a speed of around 10 knots
depending on the load condition.
However due to being very light, narrow and long the hull is capable of exceeding that speed by
quite a lot. In optimum conditions 15 knots would be possible,
but... that would require 165 hp...! On a more rational note, we'd prefer
a maximum of around 95 - 100 hp total,
sufficient for 12 knots depending on load condition.
With 400 USG and a 15% reserve, range would be around 3,000 NM at 8
knots. That's enough to reach Hawaii from any West Coast port -
and then some.
Now that's what I call economy and good speed...!
Summary
So far, this design is a prototype, i.e. it is a sketch of an idea
accompanied by a 3-D
model created within Maxsurf. It is a concept that I believe has
considerable merit for long range cruising. Monohull power passagemakers expend terrific expense on roll damping, which in this
case would just not be an issue. Relative to active stabies, the
amas would be silent and efficient. Relative to paravanes, the
amas would be very simple, would require no tending, would provide extra
space and extra buoyancy, and would not present nearly the amount of
drag induced by paravanes.
There have been some very impressive voyages in power trimarans of
late. The whole concept has engendered a completely new vessel
type: the ILAN (Incredibly Long And Narrow). An internet search
for ILAN will turn up quite a few interesting precedents for such a
vessel, and should illustrate the practicality of the concept.
With an ILAN type however, the hull materials must be light weight in
the extreme, thus they require quite an extreme budget to build...!
The adventure with this particular assignment has been:
- To create the best combination of economy and efficiency
- To somehow
nail down a style that gives the vessel a "traditional" aspect
- To create a type
that lends itself to alternate building methods
- To provide an aesthetic that will have the best chance to "fit-in" regardless of
where the vessel may be found, whether that may be in the South China Sea, or
the South of France...!
Similar Designs...?
We have developed various prototype designs for multi-hull craft,
including catamarans and proas. We have also developed a series of mono-hull vessels which are quite
similar to the Penny Wise. They are the various vessels in the
Moxie family. One of them is the 60'
Peregrine, my own ideal as a personal yacht for coastal
cruising, as well as for long range passages - and which shares quite a
lot of design traits with the Penny Wise...
