Website visitor Bob P. wrote from New Zealand to ask that I
scan and post this Wizrod 350 article and plans from the July 1972
edition of American Aircraft Modeler. Wizrod 350 is a ½A
freeflight job designed by Ron St. Jean. Bob has been a fan
of St. Jean's models from the 1950s and 60s, and wants to see
how the designs progressed into the 1970s. Billed by the author
as "an uncomplicated high-performance FF power design," the Wizrod
350 would make a good subject for a vintage craft.
By Ron St. Jean
As its name implies, the Wizrod is a combination of the best
of two other models designed by the author several years ago, the
Wizard and the Ramrod. Of the two models, the Ramrod was the easiest
to trim out and the most forgiving when mistakes were made, although
both were exceptionally easy to fly compared to other designs available.
So in making the combination, we started with the Ramrod configuration
as a basis.
When you combine the best of a wizard and a ramrod,
here's what you get - an uncomplicated high-performance FF power
The Wizard had such a long fuselage that it reminded one of a
gangly teenage boy. Because of this long fuselage, the Wizards tended
to flex when in flight, the tail sometimes appearing to wobble from
side to side as the fuselage twisted. Actually, this characteristic
did not harm the flight pattern, but probably did spook away a few
potential Wizard builders. Another unwanted characteristic of the
Wizard was its occasional tendency to tail slide. If you ever saw
one come half way down from shut-off-tail first - before completing
the stall, you'd remember it. But don't let us sell the Wizard short.
Its great contest potential is perhaps best attested to by Lee Polansky's
phenomenal Class A Open record of 94:19! And this was done with
the 1/2A version with an 051 engine, breaking his own previous Class
A record of some 70 minutes set with the same model.
Despite the innumerable trophies that the Ramrod brought home
for its owners over the years, it was not quite perfect either.
The wing airfoil was not optimal, and every once in a while a Ramrod
would zero out, normally coming straight in under power at a very
high speed. It was finally discovered that this tendency to zero
out was due to the wing's center of pressure being slightly behind
the lateral twisting line of the wing. Thus, under conditions of
high loading, a twist in the wing was introduced which was similar
to adding negative incidence. Needless to say, if any Ramrod, and
especially a hot one, were tail heavy and thus short on incidence
to begin with, it would be dangerous to fly, as just a little negative
wing twisting could spell disaster.
This phenomenon of wing twisting was best demonstrated on a Ramrod
600 several years ago. We had been flying this particular 600, which
was rather heavy, with a 29 engine for some time, with no complaints.
Just for fun one day, we substituted a hopped-up 35 for the so-so
29. The first flight, with the 35 running at a fast four-cycle,
was quite normal with an average nose-up-under-power tendency. But
when this hot 35 was leaned out on the second flight, a most amazing
thing happened: the 600, which had been launched straight up, climbed
to perhaps 150 feet, slowly nosed over into a dive, came straight
down, and pulled out upside down! It had done an outside loop! Continuing
its inverted climb at about a 20-degree angle, the Ramrod started
a slow roll, which was nearly completed when the engine shut off,
the model gliding in normally, just as if nothing had happened!
Shades of Eddie Rickenbacker - we had almost done an inverted Immelmann
with a free-flight gas model! Visibly shaking from what we had just
witnessed, we resolved never to fly that model again, so once we
were home, it went up into the attic.
Another example, this one illustrating a positive use of the
phenomenon described, is Lee Hines' Sweepette hand-launched glider
design. Lee discovered that his gliders performed better with a
highly swept-back wing, probably because they were getting higher
on launch. In effect, he had a variable-incidence glider. That is,
the center of pressure was well behind the lateral bending line
of the wing, the incidence coming out during the launch burst, but
returning for glide stability.
But back to the Wizrod: The first departure from the Ramrod design
was to utilize the Wizard tapered wing-tip configuration to eliminate
the old tendency to zero out. The Wizard wing airfoil was used with
its free undercamber, which had proven superior to the old 10% flat-bottom
of the Ramrod. We use the term "free undercamber" here because the
Wizard and Wizrod wings are built as 8 1/2-9% thick flat-bottom
sections that gain 1-1 1/2% of undercamber during building and doping
due to the rib-over-spar type of construction.
In line with the lessons learned from the extended Ramrods, the
Wizrod wing was also extended to the same degree as the Wizard,
and the fuselage was also lengthened in accordance with the old
formulas. But unlike either the Wizard or extended Ramrods, the
stabilizer was extended, with an increase in aspect ratio, so as
to maintain the 43%-of-wing-area relationship found in the original
High-revving Tee Dee 049 swinging a RevUP 633
prop pulls Wizrod way up. Cox tank mount is used.
With the exception of the new nose, which was designed around
the rectangular Tee Dee 049 tank mount, construction is the same
as in the Wizard, because it proved to have no weak spots and was
generally simpler than the Ramrod.
The Wizrod magazine plans are one-fourth full size, so scale
up accordingly. Better yet, send for the full-size plans (see page
84). Should you prefer to build the model in other than the 1 1/2A
size, consult the accompanying table for areas and corresponding
factors to use in converting the "350" dimensions. If working from
mag plans rather than full-size ones, use the factor in the fourth
column, rather than that in the third, to get your full-size dimensions.
Because the Wizrod fuselage is basically the profile type, it
is simple to construct. Begin by cutting out one fuselage side from
1/16 x 3" medium balsa. Align the balsa behind the plan and mark
the balsa by pushing a pin through the plan and into the 1/16" sheet.
Besides the outline, make marks for the firewall and the longeron
that goes under the pylon. Note that the firewall has a 10-degree
downthrust angle built in. Duplicate the second side by using the
first as a pattern. Pin the first side to your workbench (the plans
are no longer needed) and add the longerons, followed by the diagonal
crosspieces. All are 1/16 x 1/2". Be sure to eliminate the crosspiece
under the front of the stab platform that would otherwise interfere
with proper DT action. When dry, sand lightly to eliminate any unevenness
between the longerons and crosspieces, then add the second side.
When dry, lift the fuselage from your workbench, block-sand the
front to insure there will be no sidethrust and that it is flat,
then cut out and add the firewall. The two-piece gear separator
is then cemented directly to the firewall. Install the tank-mount
on the firewall with 2-56 or 3-48 machine screws, using epoxy cement
to glue the nuts to the rear of the firewall. Use care to insure
that none of the epoxy gets on the screws. The 3/32" side cheeks
are best cut out as were the fuselage sides. Mark one of them for
the Tick-Off timer, using the left or right, depending on your preference.
After the timer hole is cut, glue 1/16 x 3/8" pieces to the inside
of the cheek to make a box for the timer. The 1/16 x 3/8" balsa
needed to separate the cheeks from the fuselage is best cut from
1/16" sheet, the grain of the wood being cross-wise to accommodate
the curves. Cement this material to each cheek only after it has
been carefully cut, assembled, and sanded to proper size. Finally,
the cheek assemblies are cemented to the sides and firewall. (An
alternate procedure here is to glue the cheeks to the firewall and
then add the curved 3/8" wide pieces to fit.) Now add the 1/32"
plywood Tick-Off timer mount. Cement the tail platform and stop
block to the rear of the fuselage, and add the 1/32" U-shaped piano
wire to the bottom for a tail hook.
Cutout and assemble the 3/16" medium sheet balsa pylon, and add
the platform, hooks and gauze. Shape and sand, but do not assemble
the pylon to the fuselage at this point.
The Wizrod wing offers nothing unusual or new - just the typical
rib-over-spar construction. Accordingly, only a few construction
hints will be provided here. The rib-to-spar fit should be snug,
but not forced. Ribs that are too loose may result in a wing with
excessive undercamber, while force-fit ribs might cause a convex
rather than a concave lower surface, which would degrade performance
considerably. The two center ribs, in order to accommodate the 1/16"
planking, need to have their top cambers reduced by 1/16". The 1/16"
square false rib support glued to the bottom rear of the leading
edge should be immediately cleaned of any cement fillet which might
squeeze up, in order that the false ribs added later will fit properly
and not be held up. This is easily accomplished, as each strip is
put in place, with a square-ended piece of scrap balsa.
Author's Wizrod 350 model is bright Jap tissue
covered to help the timers and chase crew keep it in sight. This
plane is for the trophy hound!
Making a main rib template or pattern out of thin aluminum (or
plywood, as a second choice) will be a useful tool in cutting out
both the ribs and false ribs. To make the different-sized wingtip
ribs, first layout the correct length and spar locations for each
rib. Then place the main rib pattern on the balsa, with the leading
edges together, and lower the pattern's trailing edge until an arc
drawn across the top camber will intersect a point 1/8" higher than
the lower camber at the end of the rib. Draw the arc across the
top camber or, if using a metal template, cut the rib directly.
The correct spar depths are most easily figured by marking, on the
already-cut spars, the places where the ribs will intersect, laying
the spar upon the rib in such a way that the point on each where
the eventual joint will be made come together, and making a mark
for the top of the spar. The corresponding rib for the opposite
wing half can then be duplicated from the first one made in this
Begin the stabilizer by pinning down - over a piece of waxed
paper, of course - the leading edge, notched trailing edge, and
bottom cap strips of 1/16 x 1/8". Next add the single large piece
of 1/16" sheet at the center of the leading edge (which extends
into both right and left halves of the stabilizer, with wood grain
spanwise), followed by the two full ribs. Since the fin, dorsal
fin, and plywood rubber band hook are later cemented between these
two ribs, it is a good idea to make sure they are separated from
each other by inserting scrap 1/16" sheet between them while the
glue is drying. Next add the two small pieces of 1/16" sheet at
the center of the leading edge, noting that the grain should run
fore and aft, as opposed to that for the single piece underneath
them. The two gussets of scrap 1/8" sheet are now added, as are
the 1/16" square rib separator at the leading edge (clean off excess
glue, as was done for the wing). and the spars. Scrap 1/16" sheet
is used on the spars at the center to increase strength.
At this point only the top cap strips are lacking; before they
are cut and glued in place, all joints must be permitted to dry,
then the leading edge unpinned and shimmed up 1/32" with scrap balsa,
and then repinned. This will help insure that the stabilizer's bottom
surface is slightly convex - a condition required for good, longitudinal
stability (the ability to recover from a stall quickly). Add the
fin, dorsal fin, and rubber band hooks only after the stab is covered,
but before it is doped.
Once the model is complete except for the pylon being glued to
the fuselage, assemble the ship and locate the CG. The chances are
good that the pylon will have to be further aft than shown on the
plans in order for the CG to be in the proper place. Assuming this
to be the case, slide the pylon back on the fuselage until the CG
does fall in the proper place in relation to the wing and then cement
it to the fuselage at this point.
Next, check for wing and stabilizer warps by sighting along the
bottom of the surfaces. Ideally, the stab should be flat, but a
little twist won't hurt anything. The wing should be warped noticeably
but not excessively for a left turn. It does not matter whether
the left panels are washed out, the right panels washed in, or if
all the twist is in the center section. Just insure that the left-turn
warp is somewhere present in the wing by steaming or holding it
over an electric range at low heat and twisting the surface in the
desired direction. Overwarp by about 100%, as there will be a significant
Visually check the model to make sure there is no engine sidethrust.
Slight rightthrust is tolerable, but any leftthrust should be eliminated
by placing washers behind the left side of the tank mount. When
the back of the tail is keyed to the stab platform with a piece
of 1/8 x 1/4" scrap balsa on each side, there should be a slight
fin offset to the left. The plywood rubber band hook at the front
acts as not only a key, but also as a DT limiter. To achieve the
latter function, cut the slot needed to pass the hook through the
stab platform a little long in the direction of the tail. The longer
this slot, the greater the DT angle, which should be about 45 degrees.
Finally, shim up the left side of the stab platform 1/32" to 1/16"
to induce a left-hand glide circle.
After the surfaces have been allowed to cure out for about one
week after the final bout with the tea kettle or stove, take the
model and some shim balsa to the field and toss your new Wizrod
around a bit. If you have eyeballed the stab tilt well, the only
thing left is to see if an incidence change is needed to achieve
a normal gliding attitude. After you have verified glide circle
and incidence, and have gotten the feel of the model, try a few
test glides with succeedingly more zip, being sure the left wing
is low to avoid a stall. In this way there is little possibility
of having the model act up after fueling off on the first power
flight. Besides, it gives one a little HLG practice.
Make the first test flight with a short engine run, the prop
on backwards, and the engine running rich. There should be a definite
nosing-up tendency and a shallow (15-30 degree) right bank. If not,
make the needed adjustment and try again. In any event, you should
have your new Wizrod full bore and right in the groove by the third
or fourth flight ... we wish you well.
Wizrod 350 Plans
The AMA Plans Service offers a full-size
version of many of the plans show here at a very reasonable cost. They will scale the plans any size for you. It is always
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Posted November 20, 2014