Tallulah is a "metric inch" model of the "Weekender" built from the actual full size plans purchased from Stevenson Projects
I decided to make a study model of the Weekender before building the full sized boat.
The study model quickly evolved into a remote control pond yacht, which is what you see here.
Metric Inch Scale
Tallulah was built to a funky "metric-inch" scale using the 50:1 side
of a three-sided metric architectural rule and reading the decimeter markings as
if they were inches. The resulting model is about 1/13th scale, which
works out to be almost 18 inches in length for the 19 ft long
Weekender.
19ft * 12in/ft * 1in/2.54cm * 10/1 (dm as in) * 1/50scale = 17.95in
( 17.95in / 19ft ) / 12in/ft = 1/12.7scale ~ 1/13th
Why the funky scale? The dimensions on the Weekender plans are given in
inches and fractions of inches, not the feet, inches, and fractions usually
marked on an English architectural rule. Using a Metric rule eliminates
converting measurements given in lots-of-inches to feet and inches. For
instance, the 154 & 3/8ths inches of length along the top of the keel reads
directly off the 50:1 metric decimeter scale as 154.375 decimeters. No
mind-bending error-prone mental gymnastics are required to find the correct
mark. By comparison, 154 & 3/8ths inches would be 12 feet, 10 &
3/8ths inches on a 1/12 scale English rule.
Construction
The hull was constructed from 1/16th 3-ply and 5/32nds 5-ply aircraft grade
birch plywood obtained from Al's
Hobbies in Elmhurst, Illinois. The lofting lines were laid out
directly on the plywood exactly as described in the full-sized Weekender plans
with centerlines, perpendicular station lines at scale 12 inch intervals, and
offsets marked out from the center line along each station line. Push pins
substituted for nails at the offset marks, and a 24 inch long 1/16th square
strip of balsa served as a limber batten to fair the lines. Obviously, no
splicing of plywood panels was required on the model as the entire hull was cut
from a single scale 14ft by 20ft sheet of plywood, which can be seen in the
first photo at the top of this page.
Very flexible 1/16th thick birch plywood was used for the hull sides. It
bent around the curve of the hull so easily that the surface tension of the glue
was enough to hold it in place. Unfortunatly, it was a little too thin,
and flexed under light finger pressure while handling the hull. So a
second layer of birch plywood was laminated over the first, and short frames
installed inside the hull to stiffen up the sides.
The cabin roof was constructed as a sandwich, with curved deck beams glued to a flat bottom base. After theses photos were taken, two layers of the 1/16th birch plywood were laminated to the top of the deck beams. The resulting laminated top is lightweight and very stiff, and snaps into place on top of the cabin sides.
The mast, spars, bits, deadeyes, transom, rub rails, hatches, grab rails,
cockpit combings, ship's wheel, rudder, taft rail, boom crutch, and display
stand were all fabricated from mahogany stick and sheet stock manufactured by
Midwest, again purchased from Al's Hobbies. The companionway hatch slides
on waxed rails and locks onto the drop board, and the front hatch snaps
tightly onto its combings to keep the interior dry while on the water.
Eyes were carved into the mahogany trail boards and painted to give the boat
some personality; reminiscent of Jason's Argo.
All of the mohogany bright work was finished with marine spar varnish. No
stains were used on the mohogany so the colors that you see are the natural
colors of the wood. The hull was masked off and spray painted in enamel
(Rustoleum American Accents if my memory is correct.) The colors were
Hunter Green for the bottom and Heirloom White for the between-the-rub-rails
topsides strip, cabin and deck surfaces. No attempt was made to replicate
the non-skid surfaces of the real boat.
Tallulah's mahogany cradle was made to similar proportions as the stand that
comes with the paper model
of the Weekender. The construction method was inspired by a trestle table
with a tenonned main cross beam supporting mortised uprights,
and the whole shebang held together with a pair of wedges through the
tenons. Self stick felt on the upper and lower surfaces of the cradle
preserves the finish on the boat and the coffee table.
The green mat forming the background in most of the photos is one of the wife's
self-healing sewing/cutting mats manufactured by Olfa, which is conveniently
marked in a one inch square grid. This is a great surface to cut small
parts on using a hobby knife as the plastic is just grippy enough to prevent the
parts from moving.
R/C Conversion
About half way through the construction, I decided there was enough room in the
hull for radio control via standard sized servos. So I fitted the hull
with three servos for controlling the rudder, main sheet, and jib sheet.
The sail trim servos were modified with external trim-potentiometers to increase
the control arm travel from 120 degrees to a full 180 degrees of throw.
To produce the greatest mechanical advantage and reduce servo current draw, the
sheets were arranged to lead off the servo arm in-line with the arm axis at the
fully trimmed and fully eased sail positions.
The steering cable was fashioned from fishing line running in a stiff nylon sleeve (from an airplane control rod) to form a cable guide ala bicycle brake cables. Warming the nylon sleeve with a heat gun or boiling the sleeve in water softens the thermoplastic nylon enough to allow permanent reshaping. The pull-pull steering cable leads from the servo arm athwart-ship to the port cable guide where it is turned 90 degrees to run under the port cockpit seats, and into the lazarette, where it is turned another 90 degrees, leaves the guide, and is secured to the end of the tiller. The cable then continues on to the starboard side to complete the circle back to the servo arm through a mirror image cable guide.
The mahogany rudder box turns on gudgeons and pintles made from a nylon aircraft
hinge with a removable hinge pin. The rudder blade pivots just like on the
real Weekender to avoid damage during an accidental grounding.
Sails and Rigging
The sails were sown up from individual panels of nylon cloth with
stiched-together seams. The main sail has a yacht-cut seam pattern with the panel seams
arranged perpendicular to the leach. A miter cut stay sail, with seams
perpendicular to the leach and foot, fills the foretriangle.
The nylon cloth used for the sails came embossed with a fine square grid pattern, which made measuring and cutting the panels a snap, and helped tremendously in tapering the seams to give proper draft to the sails. The seams were assembled as simple S-fold lap joints with the inside of the seam overlap painted with diluted Elmer's white glue. Hitting the seam with a warm iron set the thinned glue, which held the cloth together for sewing. The diluted glue in the seams also performed like starch, giving mild stiffness to the finished sails for when Tallulah sits on display upon the mantle in the family room.
Stays, sheets and halyards are made of a manila colored extra heavy three strand
cotton yarn from the embroidery section of the local fabric store.
The running rigging turns through brass blocks manufactured by Proctor
Enterprises.
Launch day!
Here we find Tallulah sitting in her cradle on the boat ramp of Lake Cosman awaiting her first taste of the big water.
I was a little concerned that due to the placement of the servos, receiver, and
the battery pack in the forward two thirds of the hull, Tallulah would sit in
the water nose-down, and not level. This turned out to be the case.
I hoped that at worse the extra wetted surface under the bow should induce a
little more weather helm.
My original plan was to adjust her trim with some lead ballast on the rear of
the cockpit floor, but she had so little freeboard that I decided to just sail
her as is. At launching time, I guessed that I would eventually have to
cut the four cell battery apart and place two cells under each of the cockpit
seats.
The radio control worked well, and I was able to easily sail Tallulah around in
figures of eights. I arranged the controls
with the rudder on the right stick (left & right) and
the sheets on the left stick (Main sheet left & right, Jib sheet up & down).
The left stick was set up so that both sheets trim in with the stick
in the lower left corner and trim out with the stick in the upper right corner.
Tacking was a breeze, and most likely helped by the extreme weather helm induced
by the nose-down trim, which is clearly visible in these photos. Tacking
was also eased by the ability to ease the Jib sheet independantly from the Main,
which helps the boat weather-vane quickly into the wind. Pushing the left
stick forward to slacken the Jib sheet and right stick over hard to swing the
rudder starts the turn. As the bow swings through the wind, pulling the
left stick back retrims the Jib for the new course.
Shortly after these photos were taken, the wind picked up considerably, and
Tallulah suffered a knockdown from which she did not recover. Apparently,
some things do not scale well. The rig on the model is proportionally
much heavier compared to the weight of the hull than on the full size boat,
which plays havoc with the righting moment of the boat. I suspect her
stability curve looks more like a sine wave with negative stability starting in
shortly after 90 degrees of heel. Also, judging from her load-waterline
displacement, the boat is carrying about 4000 scale pounds of gear in the form
of batteries and servos located very high up in the hull. While she did
not turn turtle, she could not break the suction formed when the water touch
the sail cloth. As a concession to stability, for the next sail, I intend
to remake the battery pack into a long cylinder and mount it externally down low
underneath the keel just in front of the rudder, which should increase the
hull's righting moment and simultaneously help with the nose-down trim.
If anybody else wants to try an RC Weekender, I would suggest doubling the size
of the model and executing the lofting in 1/6th scale, or use the 25:1 side of
the metric rule for 1/6.35th scale. Doubling the length, width, and depth
increases the displacement of the model hull by a factor of eight, so that 4000
scale pounds of radio gear should reduce to about 500 scale pounds, which is a
much more realistic load for a Weekender hull. The resulting larger sized
hull should allow the servos to be mounted on their sides, which will lower
their center of gravity significantly and improve the stability of the
model. The expanded hull would also leave room for installing a small six
volt airplane fuel pump to be controlled with a fourth RC channel via a
proportional electric speed controller. Connecting the input side of the
pump to a tube drilled forward and downward through the center of the keel, and
the output side to a tube drilled downward and backward through the keel to exit
a little in front of the rudder, will result in a mini jet-drive to allow
maneuvering thrust should the wind fail altogether.
Folding Rig
Finally we come to one of the operational features of the full-scale Weekender
that I find very appealing. Setup and tear-down time for the hinged-mast
gaff rig is measured in seconds, not fractions of hours. Loosening the
turnbuckle on the forestay allows the mast to fold down and backwards into a
boom cradle for the ride home. Of course for the full scale Weekender, the
sails have to be lowered until the gaff jaws clear the mast tabernacle before
the forestay can be unhooked and the mast laid back. But on the model, we
only have to loosen the staysail halyard and untwist the forestay turnbuckle to
stow the mast.
Very cool.
This last photo was stolen from the Stevenson Projects web site and shows Mike setting up the mast on the full scale Weekender. Click (here) to go to the Stevenson Projects Pocket Yachts page. I have watched skippers at the local boat ramp waste most of an hour setting up similar sized rigs. With the full sized Weekender, I expect to be in the water and sailing in less than 15 minutes.
My appologies for the execution of the photography, as it is not my best
work. I was shooting the pictures with a Minolta 400si on a mini tripod
located on a sloping concrete boat ramp and did not notice that the horizon is
not always level in the outdoor shots. I guess the excitement of launch
day was not proportional to the scale of the model !!!
