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The
New Millennium SLEEK-STREEK |
by
Clint Brooks
April 29, 2007
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Clint's "New Millenium Sleek Streek"
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Editor's comments:
The original Sleek-Streek was introduced
by the North Pacific company
sometime in the early 1970s. It became immensely popular,
and was sold in drugstores and hobby shops all over the
United States. These easy-to-assemble sheet balsa models
were extraordinary flyers - far better than the similar
Guillows brand sheet models
currently available. Walt Mooney was purported to have
seen a Sleek-Streek fly by a full-scale
glider he was piloting, at 7,000 ft! |
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The original "Sleek-Streek" by North Pacific
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This model has been out of production for years, but remains
popular in the memories of many modelers who flew it. Clint
Brooks revives those fond memories with this new design, inspired
by the original Sleek Streek as well as the
Cloud Tramp. The New Millennium
Sleek-Streek preserves the classic lines but offers
several improvements, including a high-performance prop-hanger
and adjustable wing saddle. A plastic commercial prop can be
used, or you may carve your own balsa prop for higher performance.
Clint's instructions use modern building techniques and materials
that enable you to build a great flying model. He also includes
complete instructions for flight-preparations and flight-trimming.
Use your best balsa for this one!
Basic model specs: Wingspan: 22 inches; Length:
Approximately 19" overall; Weight: 35-50 grams without
motor.
Download the free plan here. |
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CONSTRUCTION:
Wood Selection
Choose light weight (4-6 lb.) balsa sheet for the wing and tail
components. Make sure the grain structure in the sheet wood
is as even as possible. 3” wide sheet is all that is required.
Harder wood should be selected for the 3/16 basic motor stick,
medium density wood for the 3/32 keel and 1/32 doublers. The
prop hanger block should be hard 3/16 balsa, or laminated from
1/32 & 3/32 balsa with 90 degree grain orientation. The
nose block is subject to some abuse, mainly from thrust trim
adjustments that will be required when you start flying your
Sleek Streek, and the wood must resist crushing or cracking
as much as possible. The motor stick is designed as a built
up structure to allow you to create a bonded assembly with minimal
warps, as the various elements can be bonded together with the
material clamped against a straightedge and allowed to cure.
It is optional to use a motor stick made from a single piece
of 3/16 X 5/8 balsa, should you have access to a nice straight
piece. Taper the aft end from the rear motor
hook to tail approximately as shown for the built up configuration.
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Motor Stick
The built up stick construction is begins by cutting strips
of 1/32 x 3/8 wide to make the doublers. Trim one end to the
angle shown at station 9" on the drawing. Leave a little
long for cleanup at the forward end after the bond assembly
is complete. Have some extra 1/32 sheet handy to shim the 3/32
keel that extends aft of the doubles, and keep this component
on the centerline of the 3/16 sq. upper stick.
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Cut the 3/32 keel member with the angle shown on one end.
Use the cutoff stock to make the 3/32 filler at the rear
motor hook. This is done to allow the hook to extend lower
than the nominal fuselage will allow, and creates more
clearance for the motor to prevent it from bunching at
the aft hook during flight. This helps for consistent
performance and trim settings.
Cut the 3/16 square main stick to size-leave slightly
long for cleanup at the front end after the bond assembly
is complete. Do not cut in any tapers on the aft end at
this time. Sight carefully down the length of the stick,
and determine warp direction, if any. Warp in the stick
should be placed against the straightedge you will use
to establish straightness (natural bow to be in the vertical
plane of the airplane) and will be reduced or eliminated
in the finished bond assembly.
Clamp a straight edge that’s at least 1/8 thick
to a flat surface, with wax paper under the straightedge
and the surface you will be building against. Prefit the
components together dry, so you understand the basic assembly.
The 3/16 square stick goes against the straightedge, and
the doublers and the keel then go against the 3/16 square.
In addition to the pressure against the straightedge,
pressure against the building surface is required during
the bond. This is fairly easy to do just using your fingers,
and depending on the glue you elect to use for assembly,
this may be enough to insure straightness in the finished
bond assembly. If you are not an experienced builder,
it is suggested to assemble the motor stick with aliphatic
resign glue (yellow carpenters glue-Titebond, etc.) to
allow some opportunity to adjust the pieces and provide
clamping to keep light pressure to the joints for bonding.
If you are competent with CA, this works well too if you
are careful. Use medium or slow cure CA to allow some
part positioning opportunity. |
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Original "Sleek-Streek" packaging |
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During
the dry pre-fit, place 1/32 balsa shims under the 3/32 keel
to support aft of the doublers. Secure the shim in place for
the bonding process, so it is already in position when you begin
assembly. Note-the shim is a temporary building aid and not
to be glued to the basic motor stick.
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Bond
the motor stick components together holding against the straightedge
and building surface. When cured, add the tapers on the aft
end of the 3/16 square. It tapers up from the bottom and in
planform (looking down on the motor stick) equally on both sides,
down to the thickness of the fin. This is a refinement which
is optional. However, performance of this type of model is substantially
improved with refinements such as this, and the instructions
will make mention of those found to enhance the flight performance.
Add the prop hangar block at this time, noting the angle of
the bottom for 2 degrees of built in downthrust. Finish the
front end of the stick bond assembly by trimming and sanding
to the side profile shown. Radius the front of the motor stick
for some additional streamlining. Sand the sides of the stick
lightly to blend the doublers to the 3/16 square and generally
perform some light cleanup sanding through 220 grit sandpaper.
Do not aggressively contour the corners of the motor stick down
it’s length - some blending of the lower edges will help
with motor clearance. It is also advisable to taper the lower
edge of the prop hangar block to the approximate width of the
wire prop hanger to obtain a better bond with the thread wrap
that will follow.
Landing Gear
Next, bend the .032 wire landing gear. Bend to the flat pattern
profile shown on sheet 2 of the drawing (do this before cutting
out the wing, stab and fin patterns!). DO NOT bend the axle
ends at this time-if you do, the alignment will be lost in the
next step! Then approximately 1" back from the closed end,
bend the landing gear legs down to a raked back angle as shown
on side view of the model. Now go back and bend the axle ends
up, and adjust the alignment to be square to the fuselage sides
(as closely as you reasonably can). Now prefit the landing gear
to the front end of the motor stick and adjust until a snug
fit is obtained.
Prop Hanger
Next, make the prop hanger assembly. This design has proven
consistent and easy to adjust with your fingers in the field.
Other prop hanger methods are available using brass strip with
a hole, etc. The prop hanger shown has a bearing length that
maintains the thrust setting to a higher degree than a piece
of brass strip with a hole though it. Whatever method is chosen,
use materials that are strong enough to avoid significant deflection
when the motor is fully wound, as this will cause unending frustration
in keeping the model in a consistent power trim configuration.
The other option is to omit the wire assembly and use a tube
bonded directly to the prop hanger block. Extend the block lower
than shown on the plans to maintain a similar prop shaft center
line, and use cellulose cement (Duco, Testors, Ambroid, etc.)
to allow softening of the bond joint with solvent and reposition
of the tube for left or right hand thrust adjustments. Right
thrust of approximate 2 degrees should be established if you
use the hard bonded thrust bearing method. |
Prop Hanger
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To
make the prop hanger shown, bend .047 dia music wire
into a ‘U’, about 3" long on each leg.
Make the ‘U’ radius slightly larger than
1/8 diameter using round nose pliers (use round nose
pliers for all wire bends). Round nose pliers can be
found in craft stores where they stock beading supplies,
and are very handy for accurate wire bending. Use regular
needle nose pliers to adjust wire bends, etc.
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Once
the ‘U’ is made, measure back ½" from
the edge of the bend, and bend both legs 90 degrees down using
needle nose pliers. Now squeeze just above the radius area to
force the two side together as shown on the drawing. You should
have a yoke shaped wire with two parallel legs that touch each
other. Cut-off the tails to the length shown on the drawing.
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Prop
Bearing
There are two ways to make the bearing. What is shown on the
drawing is a segment of soft brass rod, 1/8" diameter.
This can be smaller diameter if you wish. K&S brass rod
stock was used on prototype models. Cut a piece of rod to length
shown, and deburr one edge with a file. Chuck this end into
a multi speed Dremel or similar hand held tool, leaving about
1/4" exposed. Start the tool at low speed, and using a
small file, deburr the rotating brass segment and dress the
turning end flat. To drill the hole, use a hand held pin vise
(available from FAI model supply, hobby dealers) with a .047
diameter drill bit installed, about 3/4" of the length
exposed. In one hand, hold the Dremel tool at lowest RPM setting,
and with the other, the pin vise. Bring the end of the drill
bit against the turning brass with very light pressure, and
allow the point to wiggle around and find center. When it finds
the center, it will bite in and start a hole (feeling the wiggle
into position takes a very light but firm touch-it takes some
practice). Once the hole is started, apply pressure to the pin
vise to bore into the brass, stopping every few moments to back
out chips. If the hole won’t center, try cleaning up the
end of the rod again to remove any burrs from the earlier attempt,
and start again. Add some 3-in-1 oil to aid cutting, and carefully
peck drill all the way through the brass rod. The drill will
tend to stay on center rather accurately if you don’t
get too forceful with the pressure. Even if it comes out the
other end slightly off-center, it is still quite usable. Use
the file and form the turning end of the brass to a radius as
shown on the drawing. After this, apply a countersink lightly
to the hole to deburr and lightly chamfer. Remove the brass
and reverse in the chuck, and countersink the hole in that end
(flat end) Then, polish the brass with some fine sandpaper to
clean for the soldering step.
If you are unable or unwilling to make the solid brass bearing,
a composite brass tube bearing can be fabricated by using K&S
brass tubes-3/32 OD with 1/16 OD telescoped into this. Start
by soldering the 3/32 OD tube at the bearing length shown into
the yoke, to act as the housing for the bearing. Slip the 1/16
OD tube into the 3/32, and bond into place using thin CA. Then
you can then drill out the 1/16 tubing to .047 dia, using the
tube ID as a pilot hole. File the end of the bearing and housing
flat common to the propellor side, and run the countersink lightly
into the hole to clean up and chamfer both ends of the bearing.
This would be the same bearing construction for a hard bonded
setup, except you can substitute aluminum tube for brass to
save weight. Make the bearing at least one inch long for this
method. Check the running fit with your prop shaftmake sure
the shaft can turn very freely-polish the wire with emery paper
and lightly oil to obtain a smooth running fit in the bearing.
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