General Concept
Molly is so far a prototype design. I have been asked if will be
possible to scale down Moxie to 36 feet, and still be able to use steel or
aluminum for the hull structure. The result of that design study is shown
above.
Molly's displacement is planned to be approximately 13,750 at the design waterline.
Loaded
displacement is planned to be around 19,000. Other particulars are:
- Draft 3 ft
- LWL 32.2
ft
- Beam WL 10.1 ft
- Beam Overall 11.8 ft
- CP 0.59.
As with the 43' Moxie, the 36' Molly is intended to be an ideal family cruiser for
coastal and inland waters. For a place like the US Pacific Northwest, the
San Francisco Bay estuaries, the Columbia River, the entire US East Coast
Inland waterway, for the coast of Chile, the canals of Europe, the Aegean
Sea... a more
perfect small power boat would be hard to imagine, unless perhaps it would
be the somewhat larger vessels in this series (see below).
Molly is planned for a couple with occasional guests, plus a spacious
pilot house. The aft deck, screened in or enclosed with canvas, would make a
great place from which to watch the waterfront. Molly, as with Moxie, is
intended to be extremely economical to build for the amount of living space provided.
Construction
Though it may be possible to construct the hull in steel, weights
must be watched very carefully. For example, if built with a steel
hull 10 gauge plate would be a requirement for the hull, or perhaps 4 mm for
the bottom and 3.5 mm for the topsides. If built in steel, the fore deck and
the pilot house structure would necessarily be cold moulded wood.
Molly would benefit most from the use of aluminum as a hull material. In
that case, the hull, decks, and pilot house could all be built with one
material, with only the pilot house roof being cold moulded wood, a choice
based upon maximizing headroom and simplifying construction.
Molly would be an excellent candidate for building in plywood with
epoxy/fabric sheathing. This would give the boat a structure that is both
strong and light in weight. With attention to detail, much of the internal
structure such as stringers could be left visible, saving weight and
providing a very handsome interior. As with metal, all parts can be
pre-cut using a computer driven router. Very simple stuff.
My own preference would favor aluminum
construction. With metal, one can arrange for the parts to be pre-cut
by computer driven plasma arc or water jet cutter. Via the computer model
shown above, the plating, frames, tank faces, and other internal structure
can be quickly detailed for NC cutting. The resulting "boat kit" would
make for very fast assembly.
Since all surfaces are developable, Molly could also be easily built in
GRP using pre-made flat panels. If composite construction were
preferred, and it were instead desired to do a single lay-up for the hull, a
female mould would be made using flat sheet material such as particle board.
For this purpose, it can be quite expedient to create mold frames and cut
the sheathing for the mold via NC router. As with metal, the mould
parts are easily developed directly from the computer model of the hull.
Power And Range
Approximately 150 gallons of diesel fuel have been planned.
According to the Beebe algorithm for range, with a 15% reserve and a
specific fuel consumption of 18 hp/gal/hr, Molly's range would be around
1,300 miles at S/L 1.15, or 6.6 knots, for which the engine power
requirement would be around 12 to 14 hp. Variations would be noted
between the various choices of hull materials, with steel being the heaviest
and plywood the lightest, and range would vary accordingly.
Maximum speed depends on engine power. An engine of 40 hp would push
Molly at "normal" hull speed of around 7.7 knots. Due to being a relatively
light displacement boat though, the hull has a speed potential of around 8.8
knots. The engine would therefore ideally be around 50 hp to take best
advantage of the hull shape.
For this, possibly the best combination would be to make use of the
excellent Sabb controllable pitch gear, mounted onto a Lister Alpha 4
cylinder diesel. In fact, this combination is available directly from
Sabb of Norway. For more information on this arrangement, please see
our Controllable Pitch web article.
Interior
Headroom inside is intended to be approximately 6' 0" throughout,
assuming a cold molded deck and PH
top structure. If building in aluminum, the deck would be 4" thick, so
headroom would be reduced by around 2" and freeboard raised by around 2"
therefore interior headroom would be 5' - 10" throughout. If building
in aluminum, the pilot house top would ideally be cold moulded, and this
would preserve the originally intended 6' headroom there.
Accommodation layout is as follows: Right forward is a fo'c's'l.
Aft of the WT bulkhead is a double berth, then aft of that a head to port
and bureau / dresser / hanging locker to starb'd, then aft of that a
generous galley is on both port and starb'd sides. That takes you to
the end of the lower accommodations.
The pilot house is intended to have a dinette / settee right aft port and starb'd,
with a table on center. A companionway to below is to be on center
forward with pilot seat & wheel to port. Exit door to side deck
would then be to starb'd only.
The aft deck is intended to have an aft facing seat with a fixed
table and folding chairs.
In Summary
This is a preliminary design for which the general hull form is
shown above and below. Molly is at present a concept design. The hull form has
been modeled, preliminary calcs have been done, and an interior has been
sketched primarily as a "feasibility study."
I have developed various prototypes of this vessel type in sizes ranging
from 32 feet to 68 feet. Of course, those sizes are not the limits of
what could be done; they are
simply the range that we have so-far investigated in terms of achieving a
viable layout and general form factor.
Two designs in the Moxie family have been fully detailed in order to expand
on the Moxie concept: the 49' Quinn for construction
in aluminum, and the 50' Renegade for steel.
Even in the larger sizes, the layout is optimized for two people, with
guests accommodated on the saloon or pilot house settees. Of course as the vessel becomes larger the layout possibilities become
more numerous. For example, expanding the design to 55 feet or sot would provide the possibility of a second stateroom or office.
A 32' version called "Mandy" is intended to have the same accommodation
plan below forward as the Greatheart 36,
except that Mandy would have a large aft deck instead of the Greatheart 36 aft cabin. The Mandy 32 prototype has a preliminary displacement of
10,600 lb, a beam of 10.5 ft, and a DWL of 28.5 ft.
For more information on these vessels, please feel free to contact us...
Also, you may want to check out the article written about the 43' Moxie
design by Steve Knauth in Soundings Magazine here.
Copyright 2003 - 2008 Michael Kasten
