The 43' Classic Trawler-Yacht
"Roberta Jean"
Larger Exterior Profile |
Deck Plan |
Interior Profile |
Interior Plan
Perspective Forward |
Perspective Aft
Copyright 2008 - 2012 Michael Kasten
General Concept
The 43' Roberta Jean is a slight modification of my
original 43' Roberta
design. The hull form of the RJ-43 is identical to that of the 43' Roberta
except that the center of buoyancy has been moved aft slightly on the
RJ-43 in order to accommodate the farther aft
pilot house and engine room. In other words, on the original 43' Roberta
the pilot house was longer, and the engine located farther forward.
Both the RJ 43 and the 43' Roberta have a layout that is to a large extent shared across
a family of our motor yacht designs, starting with the
43' Moxie and, extending up to
their bigger sisters, the 49' Quinn, the
50' Renegade, and
the 60' Peregrine. Each of these designs represent examples of my own ideal Motor
Yacht type.
Specifically, they share in common a plumb stem, a long raised fore deck,
an aft-located pilot house, and a fantail stern.
This is a truly classic motor yacht form that I have named after the
Lake Union Dream Boats built during the '20s and '30s in Seattle, thus
the monniker: "Dream Yacht."
In the case of the 43' Roberta,
I was asked to create a design that uses the same excellent
interior layout as that of the 43' Moxie, but with a slightly heavier displacement hull form in order to provide
a little more elbow room throughout. To retain the fantail and
plumb stem, I chose a hull form based on my lineage of Tug-Yachts:
the
Boojum, Buster,
Nidaros, and Boomer
designs. These designs have a relatively much deeper body for the sake of maximum carrying capacity and
sea-going comfort. Still, they share the excellent fantail stern - a natural
and classic end for a metal boat - and a
plumb stem, very much in line with the Moxie to Peregrine "Dream Yacht" series.
Layout
As a variation on the 43' Roberta, the
RJ-43 shown here has a shorter pilot house and engine space in
order to dedicate a bit more room o the layout below. In most
other respects, they are quite similar. To augment the interior
layout drawings linked above, a walk-through of the RJ-43
interior is as follows:
The RJ-43 has a covered aft deck for part-time outdoor
living, which can be screened in
or enclosed by a canvas / vinyl dodger in cooler weather. A large open fore deck allows plenty of space for sun
tanning and for stowing gear. A flat flat "cargo platform"
/ hatch is provided on the fore deck. The shore boat will go on
the house top, nested in between the legs of an "A-Frame" mast.
Inside, the layout is as conservative as possible in order to keep boat size within limits, but still extremely
comfortable for a couple and occasional guests. The saloon settee
on the port side can be made into a double berth, as can the pilot
house dinette. Combined with the aft-facing seat on the aft deck, conceivably there is sleeping space for
seven...! If the aft deck table were able to be lowered to
berth-height to create a double, there would be room for eight...!
The galley is quite large, occupying a generous part of the port side aft. There is a large head / shower
opposite the galley to starb'd complete with - you'd never guess...
its own bath tub!
The essential differences between the Roberta Jean and the Roberta are that the
RJ-43 shown here has a larger forward cabin with an
island berth; a larger galley and head; farther aft pilot house and engine room; shorter aft deck and lazarette
/ store room.
My preference...? While I very much like the larger pilot house and
lazarette storage on the 43' Roberta, I
do rather prefer the RJ-43
shown here for its more private forward owner’s cabin and island berth.
Construction
The choice in favor of aluminum for the structure was to keep structural
weights as low as possible, yet to make the vessel as rugged as possible.
For example, if built to the same strength as a steel vessel, a
bare aluminum hull "as fabricated" will weigh roughly 1/3 less than an
equivalent steel hull. However, if designed to the same weight budget
for structure, the lighter weight of aluminum will permit a given hull form
to be built with immensely greater strength than would be possible if
building the same hull in steel.
In other words, given the same weight budget, and increased scantlings, the
aluminum structure will have a much higher strength than the same design in
steel.
The benefits of more robust scantlings are many. Among them are that the
added plate thickness will preserve hull fairness to a much greater degree;
the internal stringers and frames can be spaced farther apart, also
contributing to fairness; or if the frames and stringers are not spaced
farther, the strength will be increased proportionately.
As an example, it would be typical to build a vessel of this size using
3/16 inch steel plate, or if built in aluminum using 1/4 inch alloy plate –
in other words to use approximately 50%
greater scantling size for aluminum for a similar overall strength.
However, given the same weight budget as the steel vessel, it is possible to
use 3/8 inch aluminum plate without any weight penalty – and that is
precisely the approach taken with the scantlings throughout the
Roberta Jean 43. Rather
than having just 50% greater thickness, the plating thickness is double
that of the steel vessel, achieving a roughly equivalent weight, and a
structure that is approximately twice the strength.
There will be many who may question the above regarding steel vs.
aluminum on the basis of strength vs. weight. I refer them to my web
article on just that subject at
www.kastenmarine.com/alumVSsteel.htm.
For the RJ-43, all parts are intended to be NC cut by plasma arc, water jet, or
router. The NC cutting process leverages the work that has already been done
to create the computerized design model. In other words, structure can be
easily developed directly from the surface model of the hull and
superstructure. The resulting "boat kit" makes for fast and accurate
assembly. Once the parts have been pre-cut and delivered, the frames and
other internal structures are quickly erected, the stringers placed, and the
plating applied.
This not only saves considerable labor on the fabrication floor, it also
vastly improves the accuracy of the fit-up. The result is consistent
plate seams and much less distortion during the weld-up, yielding a much
more fair hull. The reward is that the hull does not need fairing, and
for that matter does not even need paint...!
Stabilization
Although steadying sails could certainly be used, the
RJ 43 is specified to make use of low-drag aluminum paravanes for
stabilization. These low-drag paravanes are a series of proprietary
designs that I developed based on US Navy research as regards geometry,
balance and size matched to various boat sizes.
These low-drag paravanes make use of NACA foil shaped surfaces combined with
a weighted NACA foil shaped bulb. They are designed to be machined out of
marine grade aluminum plate and rod. The paravanes are balanced and are
adjustable for different speeds.
Power And Range
As with all the vessels in my “tug-yacht” and “dream
yacht” series, the
RJ 43 has a rather plumb stem
in order to maximize the WL length within a given boat length. In
addition to providing more accommodation space, this also provides the most
boat speed for a given overall boat length.
For the sake of ocean voyaging, the RJ-43 has been given a
generous fuel capacity. Per the Beebe algorithm for range
calculations, the
RJ 43 should achieve 3,000 NM at 7 knots on a fuel capacity of
770 USG with 12% held in reserve.
A 4 cylinder John Deere engine
has been specified. If one were to prefer a naturally aspirated
engine, the JD 4045 DFM at around 75 to 85 hp should push the vessel along
at S/L 1.2 to 1.32. If using the JD 4045 TFM (turbo version) at
105 to 130 hp there would be plenty left over to punch into the weather.
The propulsion gear shown in the drawings is the JD 4045 TFM mated to a Sabb
controllable pitch gear and Helseth self-contained shaft system having a
three blade controllable pitch propeller – the ideal for fuel efficient
travel at any boat speed and at any loading.
Particulars
Overall height is kept under 3.5 meters in order to also allow cruising the canals of Europe.
Roberta Jean's particulars are:
- 43' - 0" Length on Deck
- 12' - 6" Moulded Beam
- 39' - 7" WL Length - Half Load
- 5' - 1" Draft - Half Load
- 9' - 5" Air Draft - Half Load
- 42,000 Lb Light
- 54,000 Lb Loaded
In Summary
For a couple seeking a comfortable life afloat, the 43' Roberta Jean combines all of the basic
necessities with the luxury of a spacious and un-crowded interior. In terms of the perfect interior for a
personal motor yacht, the Moxie - Roberta - Roberta Jean - Quinn - Renegade - Peregrine
designs are my own first
choice.
To me, the primary appeal of these designs is the excellent accommodations for two, even in the larger sizes.
Guests can be accommodated by various means, none of which require there being a separate dedicated guest cabin.
A covered aft deck offers protection from sun and rain; a gourmet size galley and big saloon allow the luxury of
fine dining afloat... Combine that with simple construction and economical powering... we think it is a winning
combination to say the least.
For more information on these vessels, please
contact us...
Similar Designs and Prototypes in this Tug /
Trawler Yacht Series
Tug Types
Boojum 22 |
Boojum 25 |
Boojum 30
Terrier 32 |
Talisker 32 |
Nidaros 38
Trawler Types
Sweet Okole 30 |
Buster 30 |
Boojum 43
Roberta 43 |
Roberta Jean 43 |
Roberta Jean 47
Far Horizon 40 |
Far Horizon 43 |
Far Horizon 46
Direct Quote from an aluminum boat owner...
As an owner since 5 years of an aluminum boat I could not
agree more with your preference for this material. She is a
great boat and requires very little in the way of
maintenance. I do a lot more reef snorkeling than the paint,
polish, varnish and wax guys!
--Peter Kminek
