Vac-U-Boat Vac-U-Cracker User manual

Vac-U-Cracker™
1/10 Scale Crackerbox
Model Kit
For Radio Control
Manufactured by Vac-U-Boat™
1259 Humphries Rd.
Conyers, GA 30012
[e-mail]
Length: 19-7/8 in. Beam: 7-3/8 in.
Thank you for purchasing this Vac-U-Cracker 1/10 Scale Crackerbox kit. You will find the
quality, fit, and finish of this High Impact Polystyrene model to be superior to other kits.
The Vac-U-Cracker™ features exterior details true to the actual Crackerbox racers found
along the West Coast of the United States. These include a scale Chevy V-8 properly oriented
in the engine compartment and realistic drivers with scale helmets. The exterior hardware is
constructed of stainless steel including the “double shark-fin” turn fin, rudder blade, and trim
tabs. Inside you will find a strong aluminum motor mount that will not flex under load, an
mahogany transom reinforcement, ribbed hull & deck reinforcing liners that resists flexing and
twisting giving the hull the rigidity of a fiberglass model. The hull reinforcement has formed
“beds” for the motor mount base, turn fin, and the pass-through for the stern tube. The design
minimizes hull impact flexing and motor torque-induced roll to the hull floor. The drive train is
complete including a stainless steel shaft supported by Oilite® sleeve bearings in a self-
supporting thick-walled brass stern tube. An Octura® X-431 racing prop is included. The
injection-molded rudder assembly includes a stainless steel rudder blade that swings up on
impact reducing the risk of damage to the rudder components. A stainless steel pushrod and
DuBro® EZ-Connector are included. The rudder base is designed to fit next to the included Bru
-Line® Pushrod Seal. The open interior hull floor layout allows you to place your hardware
where you wish in order to adjust the center of gravity according to racing conditions. You
also get a 60-yard roll of Hatch Tape and building supplies including paper clips, ratchet
clamps, epoxy brush, & a transom clamping board.
Buy as much of the kit as you wish. The “Plastic-Only Kit” includes only the vacuum-
formed plastic, transom reinforcement, and the building supplies. Four hardware packages are
available separately. The “Complete Kit” includes all hardware packages. You supply your
choice of R.O.A.R. motor, radio gear, battery, and speed control.
Regulated by the IMPBA, International Model Power Boat Association, the Crackerbox is a
Specialized N-1 MONO class as a scale model of the full-sized APBA, American Power Boat
Association, one design runabout.
The Crackerbox is not an easy ride. Even with the power limitations of a R.O.A.R. motor,
the hull is almost over-powered. You cannot just give it the gas and expect to cross the finish
line. It takes a good eye, easy touch, and careful use of the throttle just to remain upright
through a complete race! A recovery system for overturned boats is required. This boat is easy
on the budget as well. You won’t need exotic electronics to run this boat. The skill of the
driver determines who crosses the finish line first.
© 2005-2011 Philip Pace dba Vac-U-Boat™

Now, for the Warnings!
Read all of the instructions! Review and understand each step, and the one after, as you build
your boat. Don’t rush. Good work takes time.
This is not a toy! I know. It LOOKS like a toy, but it isn’t. Toys are generally safe for small
children. This boat is not safe for small children. Assembling it requires the use of sharp tools
that can cut skin, strong adhesives than can bond flesh and injure eyes, spray paints that can be
flammable and toxic, as well as batteries that can short causing severe burns or fires. Read all
of the instructions and warnings on all of the tools and chemicals you plan to use. Use
protective eyewear when recommended. USE SAFETY GLASSES! If you think you don’t
have the skills, or are uncomfortable with tools and chemicals, or just changed your
mind, then pack up this kit and return it immediately for a full refund. If you bought this
direct from Vac-U-Boat, I’ll reimburse you for standard return shipping. If you need some
help, find a local boat club to join, check with the hobby shop where you purchased your
motor and radio gear, or contact internet clubs and organizations for assistance. Keep
your work area away from children. Even if you have no children, when not working on the
kit, keep all sharp objects and all chemicals locked away in a safe area. You never know who
will come to visit and how well they will supervise the young ones with them.
This is STILL not a toy! Once you complete the boat and are running it in a lake, know that
the boat can injure life, limb, and property. Never touch the propeller, spinning or not, while
there is a battery inside or connected to the boat. Even if it is turned OFF, assume it can glitch
and run on its own. Never run the boat if swimmers are in the water. Don’t chase wildlife. Be
careful with rechargeable batteries. They have the ability to dump large amounts of current in a
very brief period of time if shorted, causing burns or fires. Never store the boat with the battery
inside it, connected or not. Keep your batteries in a safe place, out of the reach of children.
Read the warnings on the other parts you purchase, the motor, battery, electronic speed control,
radio transmitter and receiver, and the battery charger. Use “frequency boards” at your lake to
control radio channel usage. If you don’t control channels, then you increase the risk of loosing
control of the boat. An out of control boat can harm someone. You are responsible for the safe
use of this product. You are responsible for choosing wisely, those who you entrust the use of
the boat and radio, even for a few minutes at a lake. Never swim after a disabled model boat!
This is an adult toy! That is what you say to those nice stranger-type kids that come up to you at the
lake. It isn’t easy, but it is the responsible thing to do. Clubs should keep slower scale boats for
visitors to run. I happen to know a guy who makes a nice easy-to-build plastic tugboat kit that is just
fine for such an occasion. Lets see, what was the name of that boat?....
CHOKING HAZARD - Small parts. Not for children under 3 years.
WARNING - To avoid danger of suffocation, keep plastic bags away from babies and children. Do not use
in cribs, beds, carriages or play pens. THESE PLASTIC BAGS ARE NOT TOYS.
WARNING: Brass parts in this kit contain lead, a chemical known to the State of California to cause
cancer and birth defects and other reproductive harm. Bronze and brass alloys can contain lead.
WARNING:

INSTRUCTIONS
Finally, we are ready to get started building this Vac-U-Cracker. Follow the numbered photos and captions to
assemble your boat. Read through the instructions before building. Assemble the necessary tools and adhesives
on a clean workbench or table. Keep paper towels handy to catch spills. Don’t forget the safety glasses!
You will need 30 minute epoxy, filler for
epoxy (talc, Q-Cells, or your favorite)
Medium CA (or regular model cement),
2 wood scraps or hardcover books, bags
of sand or a 6” x 9” scrap of flat wood, as
well as sharp scissors and a hobby knife.
Consider a sealant or RTV gasket
material for attaching the deck.
Check that all of these parts are in
your kit: Hull, Hull Liner, Deck,
Hatch Cover, 7 Air Cleaners, 3
Helmets, and 3 Helmet Mounts. You
will also find a paint stirring stick &
clamps that will help to clamp the
transom together.
Begin by trimming the Hull along the
marked line as shown. If you are right
-handed, cutting with the boat hull on
your right and the waste on your left
should be easier. Cut carefully.
Afterwards, use sandpaper to level
any uneven spots.
Drill 1/4 inch holes in these locations.
They will provide ventilation under
the hull liner so any moisture trapped
there can dry. Properly placed, larger
holes can save weight without
affecting strength of the floor.
You may find it easier to drill from
the underside of the Liner with a scrap
of wood behind the plastic. This will
support the plastic during drilling and
help avoid tears and splitting. Test
drill on a scrap for practice.
Sand the inside of the Hull on all
surfaces that will contact the Hull
Liner. Always sand the plastic
surfaces where epoxy is used.
Sand the raised areas on the underside
of the Hull Liner. Using the supplied
100 grit sandpaper with light pressure
will roughen the surface of the plastic.
Underside View
123
456
Sand the inside of the Hull Liner
where the mahogany transom
reinforcement will be installed.
789
3
Trim the Hull Liner the same way.
Opinions differ as to how much of the
liner is really necessary. Its size can be
reduced to save weight. I recommend
you leave the sides as-marked for the
best impact protection for the hull.

4
Cut a piece of the paint-stirring stick
smaller than the mahogany transom.
These two pieces will be used on
either side of the transom for
clamping it together.
Pour two 1-3/4 inch circles of parts A
& B of the epoxy. (One looks larger but
is thinner and spread out before the
photo was taken. Mix together well.
Fold in some filler. About 1/2 the
volume of the epoxy is the right
amount of filler to use. (1/4 for Q-
Cells) Mix until smooth and even.
Brush the filled epoxy on the back of
the Transom Reinforcement and place
the reinforcement inside the hull
against the Transom.
Fully cover the Skeg and Stern Tube
recesses. Where you will be cutting
through the hull to install the turn fin
and stern tube. Set the Hull Liner into
the Hull.
Brush the filled epoxy on the underside
of the Hull Liner on each “rib” and all
of the parts of the bottom that contact
the hull. Do not epoxy the drain
channels along the center of the liner.
Take the two pieces of wood, or
hardback books, and wedge them to an
angle to match the bottom of the
transom. This forms a flat hull bottom.
Drain Channels
While pressing down the Hull Liner,
clamp the Transom together using the
two pieces of the paint stick to evenly
spread the pressure of the clamps.
Or, use a flat wood block about 6
inches by 9 inches, tapered to fit only
on the flat area of the hull liner. Set a
weight on top to apply pressure.
Set the sand bags into the Hull floor to
clamp the Hull Liner against the Hull.
Install the 20 paper clips on the sides only
far enough to hold the liner to the hull.
Assembly note: Set the Hull Liner
into the hull, then set the transom
reinforcement in place.
10 11 12
13 14 15
16
Quickly brush the filled epoxy inside the
Hull only on the sides and on the
Transom. Glue for the bottom of the Hull
is applied to the bottom of the Hull Liner.
17 18
19 20 21

Make a final alignment check of the
hull to be sure it is centered to the
angle of the blocks on both ends.
When you get to a corner, break away
the scrap, then continue cutting. Sand
the cut edge smooth.
Use a Hobby Knife to score around the
bottom of the hatch opening. Repeat this
2-3 times until you cut through. Scored
styrene will snap apart when flexed.
Trim the Boat Stand. After trimming,
you can use sandpaper to smooth the
edges or to remove any high spots
along the cut.
Set the stern of the boat at the end that
is taller where the arrow is pointing.
This end is higher and allows
clearance for the rudder blade.
Rough-trim the Hatch to about 1/4
inch outside of the marked line. Test fit the Hatch to the Deck. Sand the hatch edges as needed to fit.
Then, carefully trim along the marked
line. Sand the round corners smooth.
Clean your epoxy brush with alcohol. Cut
out the Deck. Cut carefully as this cut
edge will be visible on the finished boat.
You have 3 Helmets and Helmet
Mounts. One is a spare for “boating
accidents” or can come in handy if
you miss-cut one.
Then, trim away the bell leaving a
strait slope to the side of the Mount.
Rough-cut the Helmet Mount as
shown. Cut close to the curve of the
plastic.
5
22 23 24
25 26 27
28 29 30
31 32 33

The cup-shaped Helmet Mount will be
about 1/4 inch high. Then trim around the bottom at the
point where the plastic flares out.
Sand the cut line as necessary for a
smooth bottom edge. This forms a
realistic Helmet as shown.
Note the shallower 45º slope of the
Helmet Mount (arrow). This
corresponds to the back of the helmet.
Without glue, test fit the Helmet by
engaging the rear of the mount first
as shown above. You may want to
paint before gluing on the Helmet.
Glue a tiny piece of foam inside the
Helmet for flotation if lost. Apply CA
around the inside along the bottom
one-quarter inch of the Helmet.
Tilt the Helmet forward while lifting
gently at the rear. Note the mount is
slightly forward compared to the driver’s
neck.
Rough-trim the helmet close to the
base as shown.
Install the helmets as you did for the
test fit. If you want to be creative, you
could rig the drivers heads to rotate
with the rudder!
After rough-trimming, you can use
sandpaper to smooth the edges of the
air cleaner.
You have 7 Air Cleaners to choose
from, or you can fashion one of your
own.
CA the Helmet Mount to the driver’s
neck about 1/8 inch forward of center.
Medium CA allows repositioning for
a few seconds.
6
34 35 36
37 38 39
40 41 42
43 44 45

Without adhesive, test-fit the Hull to
the Deck. Check the finished edge of
the deck for any uneven areas and
sand them mooth.
Apply a bead of sealant filling the
underside of the Deck Flange. The
sealant will have a triangular cross-
section. Fill the bow groove.
Only gentle pressure is needed to hold
the Hull to the Deck. Have a small folded
towel to use later when gluing the two
together as shown below.
Make sure there is no high spot in the
towel or pillow at the Hatch opening.
You can instead use Masking Tape to
hold the deck to the hull while the
sealant cures.
The “Plastic Only” kit is completed
and ready for hardware installation.
Additional instructions include
standard Vac-U-Cracker hardware
you can use as a guide for your own.
Set the Hull onto the Deck at the Stern
first, then rotate the Deck down at the
bow, as you help the Hull sides slip
into the Deck flange where the sealant
is applied. Let this fully cure.
Support the deck, upside-down, on a
pillow or stack of towels to support it
evenly along its perimeter.
7
46 47 48
Test fit the Hull to the Deck. Check the
finished edge of the deck for any uneven
areas and sand them mooth.
49
A sealant or RTV gasket maker will
give a flexible joint. “Pinch-sand” the
top edge of the Hull to roughen it.
50 51
Sand the underside of the deck and the top of
its reinforcement. Apply filled epoxy. Clamp in
place with six clothes pins as shown. Check the
groove to make sure it is even left and right.
52
Sand the inside corner of the underside
of the Deck. Roughening the surfaces
will help bond the sealant to them.
53 54
55 56 57
CA the Air Cleaner in place. In the next
step #47, the precut bow reinforcement is
touching the deck opening.
Align the clothes pins like this. This
will result in an even groove around
the bow for the hull.

The Turn Fin must fit without
binding. Use the strip of emery cloth
to widen the slot as needed. Sand
slowly and frequently check the fit.
Don’t forget to sand the walls of the
recess as well. Same with the walls
and ribs of the Motor recess and the
pass-through for the Stern Tube.
Sand the inside of the Turn Fin recess so
the filled epoxy will bind it to the hull.
You will use the Boat Stand to
support the Hull while the Turn Fin
epoxy is curing. Put a paper towel
into the stand to catch any drips.
Scuff the flange of the Turn Fin on
both sides with the emery cloth. Don’t
sand the blades of the Turn Fin.
Looking from the stern, use the
reflection of the Turn Fin to confirm
that it is perpendicular to the hull.
Test-fit the Turn Fin into the slot you
just made.
8
58 59 60
Repeat scoring both sides of the raised
line until you are through the hull.
Remove the strip of plastic at the center.
62 63
64 65 66
HARDWARE INSTALLATION
Use these instructions to install the hardware components of the Vac-U-Cracker, or as a
guide for the basic setup of your own hardware. Alignment of the drive components is critical
to a high-performance boat. Installing the hardware in the order shown will allow you to
visually check the alignment and to make adjustments before applying adhesives.
There are numerous ways to modify this kit for maximum performance as a stock 1:10 scale
Crackerbox. Or, you can attach a surface drive and create an “Unlimited Class Crackerbox”.
Check with the Vac-U-Cracker web page for the latest recommendations and suggestions.
Check with your club members for their opinions on configuration & balance of the model.
Cut the slot for the Turn Fin.
Carefully score the liner on each side
of the raised Turn Fin line.
61

Score along the edge of the raised
area with a hobby knife. Continue
scoring strait down until you have
connected the two holes.
On the underside of the slot, bevel
the rear end (stern end). These bevels
allow the Stern Tube to lay in the slot
without binding.
Use the hobby knife to bevel the front
end (bow end) of the top of the stern tube
pass-through slot.
Fill the Stern Tube with your favorite
lubricant. Greases seal well but can
cause a lot of drag on the motor.
Thinner lubricants cause less drag but
may need refilling more often.
Lay out the drive line. For
competition, Crackerboxes require a
“R.O.A.R. Legal” motor. Brushless
R.O.A.R. setups are available.
White lithium grease, or a synthetic
grease works well. They can be thinned.
Push out the excess grease by inserting
the Drive Shaft. Clean any excess grease
from the Stern Tube with solvent.
The holes should line up with the
round ends of the raised area. View
is from the tray underside.
9
67 68 69
Straighten the Turn Fin. Fill the recess
with filled-epoxy.
70
Press the fiberglass cloth into the epoxy
until it is saturated. Check the alignment
of the Turn Fin frequently until it cures.
71 72
Reinforce the Turn Fin installation by
laying a scrap of fiberglass cloth, or
other material, into the epoxy.
73
After the Turn Fin epoxy cures, install
the drive train. Drill two 7/32 inch
holes on either end of the raised area.
74 75
76 77 78
Hold the Turn Fin at an angle and
push filled-epoxy under its flange
until it appears behind the holes.

The prop should be spaced
approximately 1/8 of an inch from the
underside of the hull with a 1/8 inch gap
between the drive dog and stern tube.
Mark the Stern Tube where it
passes through the hull. This marks
the area you will sand. From the
Bow, check the alignment of the
Prop Shaft to the Turn Fin. Slide the
Motor Base left or right to center the
Propeller.
The motor base or prop shaft assembly
should not bind to the hull. Adjust the
motor mount screws or the length of the
slot in the hull to align the prop location.
Clean off any grease residue and then
scuff the Stern Tube so it will bond
with the filled epoxy when installed.
Sand the recesses for the Motor Base
and the Stern Tube slot.
You can glue the Motor Base and
Stern Tube at the same time, or
separately. “Same time” follows:
Put more of the filled epoxy into the
motor base recess of the hull liner. Be
generous.
Mix two 1-1/2 inch puddles of parts A
and B epoxy together. Add filler.
Brush on the underside of the Motor
Mount Base. 10
79 80 81
Install the Motor Mount as shown with the
6-32 x 1/4 inch screws centered in the base
slots of the mount. Tighten the screws.
82
Install the 3-piece Thrust Bearing and the
Coupling, adjusting so the coupling pushes
against the bearing without binding.
83 84
Install the motor with the M3 screws
in the lowest position on the Mount.
Lightly grease the Thrust Bearing.
85
Put a tiny piece of electrical tape over
the center of the T-Nuts to prevent
epoxy from filling the threads.
86 87
88 89 90
Grease Bearing
Assemble the Prop Shaft Assy. Put the
Shaft into the Coupling with the flat of
the shaft under the set screw & tighten.
Scuff the underside of the wood base
so the epoxy will bind to the wood.

Take any extra filled epoxy and
place it around the Motor Base to
better bond it to the walls of the Hull
Liner recess. Let the epoxy fully cure.
Use a push-pin to press marks
through the template onto the
transom. Drill four 1/16th inch holes
at the pin marks on the transom.
Carefully trim the Rudder Template.
Align and tape the template to the
Transom. Set the Rudder on the Template
to check Prop-Rudder alignment.
Use one of the rudder mounting
screws to thread the holes for the
rudder. Use some pressure to help the
screw bite into the PVC reinforcement
without causing the Hull to pull away.
Drill the mounting holes with a
1/16th inch bit, and the center hole
1/4 to 3/8ths inch diameter. Remove
the rudder from the transom.
Temporarily install the rudder with 2
screws. Use the Bru-Line™ Pushrod
Boot Bracket as a template to mark the
centers for three holes needed. 11
91 92 93
Connect the Prop Shaft Assembly to the
Motor. Your goal is to have epoxy around
the stern tube before the motor sets.
94
Put masking tape around the Stern
Tube to catch any epoxy that may drip
around the Stern Tube slot.
95 96
Check the Prop to Hull distance one last
time. Slide the Motor Base left or right to
center the Prop.
97
Add some of the filled epoxy to the
recess around the stern tube.
98
100 101 102
Fill the recess. Push epoxy under and
on top of the stern tube. Before the
epoxy cures, check the alignment.
99
1/8”
1/8”
Set the Motor Assembly into the
Hull Liner. Work quick. Even 30-
minute epoxy will cure too fast!

Trim Tabs are installed level with the
bottom of the hull at the outer edges.
Drill 1/16th inch holes to mount them.
The oval holes in the Tabs will allow
some adjustment after installing.
If your receiver is an AM or FM
model with an antenna wire, at the
edge of the deck, locate a position
near the receiver. Drill a 1/8th inch
hole through the deck.
Insert the mast through the deck and
secure to the inside of the hull with
tape. This installation will be relatively
water-proof and will allow you to
easily remove and replace the antenna.
This completes the construction of
the Vac-U-Cracker. Some tips are
attached. Go to www.vac-u-boat.com
for additional construction or
painting tips.
You will have to remove 3 of the 4 arms
on the servo. The Pushrod should be
centered in the hole in the transom. Mark
the servo for mounting to the floor.
Mount with Epoxy or Servo Tape.
12
103 104 105
Insert the Pushrod Boot into its mount as
shown.
106
Put a little grease on the pushrod to
help it slide into the boot, and install
the rudder with 4 screws.
107 108
Install the pushrod boot to the transom.
Make sure the boot is centered in the
aluminum bracket.
109
Connect the radio to “Center” the
servo. Locate the Steering Servo so the
Pushrod will be strait. The Servo Arm
vertical and the Rudder Arm square.
110 111
112 113 114
Install the Z-Bend end of the
Pushrod into the Rudder Arm exactly
as shown.
Run the rudder left and right to make sure
the pushrod is not binding in the transom.
An external antenna is recommended for
the best reception for the model.
For epoxy, sand the Hull Liner where
marked. Use a hobby knife to score
the servo as shown. Use Velcro to
attach the ESC, Receiver, & Battery.
Glue scrap wood blocks at each end of
the servo to reinforce it to the floor.

PAINTING TIPS: It will take 2 to 3 coats of most hobby paints to give a good even color. Never try to get full
coverage with the first coat. It will run every time! You should be able to see through the first coat. The best tip about
any kind of spray paint is to let the paint “flash” between coats. A coat of paint has “flashed” when it is dry to the
touch. Don’t touch the boat. Touch the masking paper or somewhere where a fingerprint won’t show in case you touched
it too soon. Hobby enamel or Krylon Fusion paint will take 5 to 15 minutes to flash depending on the temperature.
Different colors can take different times to flash. A coat that has flashed properly will support the next coat and prevent
it from dripping. The second coat will take longer to flash than the first. Be patient! Practice on a scrap stood on it’s end.
Your goal is to get coverage without runs. Avoid spraying enamel on very humid days. Humidity can cause the paint to
“blush” leaving a cloudy appearance to dark colors. “Non-toxic” model paints are safest to brush on, for the painter and
the boat.
PAINTING THE HULL: Styrene is best painted with Hobby Enamels, Krylon “Short Cuts”, or Krylon “Fusion”
paint designed for plastic. Sanding is not necessary as these paints chemically bond with the hull plastic. They will not
peel from the surface, even when scraped by rocks or other sharp objects. Lacquers and regular enamels, like regular
“Krylon” paints will melt or weaken the styrene in thin areas or when applied wet-on-wet. Use them at your own risk!
FRONT RIGHT REAR
LEFT TOP 3-COATS BLUE + 3 COATS FUSION
CLEAR COAT
OPTIONAL CUSTOM DECALS: Apply only after the paint has fully cured. Cut out the desired decal from the set.
Separate the paper backing from the front tissue. The decal will adhere to the front tissue. Place the decal on the hull and
smooth it with your fingernail. Peel off the front tissue paper. The decal set includes two side name-number sets and one
top set along with a small “boat” emblem to put on the boat stand to remind you which direction to set the boat on the
stand.
WATERPROOFING - FLOTATION: Clear or colored electrical tape makes great hatch tape. Use new tape for each
run. Seal the tape to the hatch by lightly drawing your fingernail along the hatch seam. Reused tape will leak. If your boat
flips over, it may be several minutes before it can be safely retrieved. Don’t risk your electronics on a few cents worth of
tape! There is plenty of room in the Bow for flotation. An inflated Ziplock® bag with the opening pressed and taped
closed, makes a nice form-fitting float. If you have a mysterious leak, seal the hatch, hold the hull under water and gently
squeeze the deck. The light pressure you put on the sealed hull should release bubbles at the leak. A dab of grease on the
tip of the pushrod boot, and on the tip of the antenna tube will seal those areas well enough.
MAINTENANCE: After running, tilt the boat toward the Bow and blot out any water that was hiding under the
floor. Leave the Hatch off for a couple of days to allow any moisture to dry. Remove the battery from the boat and store it
properly. Check the Stern Tube lubricant regularly. The Stern Tube can be modified with a filler tube or easier, just drill a
tiny hole large enough for your lube syringe and slip a section of silicone rubber hose over the tube to close the opening
while running.
Now go find some water and have fun! Copyright © 2005 - 2011 Philip Pace, d.b.a. Vac-U-Boat