Madcow Rocketry PAC-3 User manual

Specications:
Length: 50”
Diameter 2.6”
Weight: 21oz
Recovery: 24” Nylon Chute
Motor Mount: 29mm
Fins: 8 - 1/8” Plywood
CG: 31” from nose tip
Recommended Motors:
Single Use RMS
F20W-4 780’ F40W-7 1100’
F50T-6 975’ G64W-7 1620’
G40W-7 1440’
G80T-7 1700’
Parts List
1. (1) Molded nose cone
2. (1) Pre-slotted body tube (10.5”)
3. (1) Mid section body tube (20.5”)
4. (1) Forward section body tube (10.5”)
5. (2) Centering rings
6. (1) Bulkhead
7. (1) Eyebolt, nut & washer
8. (1) 29mm motor tube
 9. (8)laser-cutns
10. (1) Kevlar® shock cord section
11. (1) Nylon shock cord section
 12. (1)9”x9”ameproofchuteprotector
13. (1) 24” Nylon chute
14. (2) ¼” launch lugs
15. (2) Couplers
16. (1) Cut Vinyl Decal
Required to complete: 5 minute epoxy,
120/220sandpaper,maskingtape, nishing
ller/paint.
K-146
PAC-3
898666 00146 8
®

2 ©2009 MadCow Rocketry™ PAC-3 Assembly
Please make sure you read all directions and understand how to assemble your model
beforeyoustartconstruction.Itisalsoagoodideatotestteachpartbeforeassembly
–somemanufacturingtolerancesmayrequirelightsandingbeforenalassembly.
Laser cut parts will exhibit varying amounts of charring on the edges depending on the
density of the plywood. The charred edges do not interfere with bonding and do not
need to be cleaned before assembly. In most cases the charring will be cleaned up
duringsandingfornishingandpainting.
Step 1 – Motor Mount Assembly
Testtthecenteringringsoverthemotormounttubeandsandifnecessary.Therings
shouldhaveasnugtbutlooseenoughtomovetheringoverthemotortubewithout
deformingit.Alsotesttthecenteringringsinthebodytubeandsandifnecessary.
One of the rings will have a notch for the shock cord - this will be the forward ring.
Spread some epoxy on the outside of one end of the motor tube and slide the
ring (without the notch) until there is approximately 1/8” of motor tube exposed.
IMPORTANT:Make sure you clean the
motor tube of any epoxy so as not to
interferewiththentangslater.
After the aft ring is dry, make a mark
2 1/2” from the other end of the
motor tube. Spread some epoxy on
the motor tube and slide the forward
ring (with the notch) until it aligns
with the mark.
Step 2 – Shock Cord Attachment
The shock cord in this kit consists of a shorter section of Kevlar and a longer section of
nylon cording. The two sections should be tied together using a single overhand, ring
bendordoublesherman’sknot.TheKevlarsectionwillbeattachedtothemotormount
and the nylon section will be attached to the nose cone.
Wrap the end of the Kevlar shock
cord around the forward end of the
motor tube and tie a square knot or
bowline knot near the notch in the
forward centering ring. Apply some
epoxy to the knot to make sure it
doesn’t come loose later. Make
sure the Kevlar loop is seated against the
forward centering ring so that it will not
interferewiththentangslater.YoucantackwithepoxyorCAtoholdinplace.
1/8” Exposed 2 1/2” Exposed
Forward Ring Notch
Fin Fin Tang
Apply CA or
Epoxy to knot
Push cord in corner and
tack with epoxy
Step 3 – Insert Motor Tube Assembly into Body Tube
Wrap the shock chord into a small bundle and stuff it inside the motor tube for this next
step.Makesurethecordpassesoverthenotchintheforwardcenteringring.Testtthe
motortubeassemblyintothebodytubetoensureasnugt.Sandthecenteringringsif
necessary.
Whenyouaresatisedwiththet,spreadsomeepoxyontheinsideofthebodytube
and slide the forward centering ring of the motor assembly into the body tube. Make
sure you have the motor assembly facing the right way! (The shock cord goes

PAC-3 Assembly ©2009 MadCow Rocketry™ 3
Ensureringsareclearofthenslots
Step 4 – Fin Assembly
Testteachofthensintotheprecutnslots.Thenshouldseatrmlyagainstthe
motortube-sandeachnifnecessary.ThePAC-3nsconsistoftheaftns,whichare
Tshaped,andtheforwardnswhicharewedgeshaped.BeginwiththeaftTshaped
nsandapplysomeepoxytotheendofthentangthatwillcontactthemotortube(the
topoftheT).Also,spreadathinlayerofepoxyoneachsideofthentang.Slidethe
nintoplaceandcheckthealignment.Continuerecheckingthenalignmentuntilyou
aresuretheepoxyhasset.Cleananyexcessepoxyfromaroundthenjoint.Repeat
fortheremainingaftns.Next,attachtheremaining4forwardnsensuringtheyare
alignedwiththe4aftnsandtheyareseatedagainsttheaftendoftheslot(slidall
thewaybackasfarastheycango).Last,applyepoxylletstobothsidesofeachn.
Carefullysmooththeepoxylletswithyourngerbeforetheepoxysets.Alloweachllet
tosetbeforerotatingtheairframeforthenextllet.
Step 6 – Launch Lug Attachment
Mark the CG point along the launch lug line you made in a previous step. Make sure you
measure the CG point from the tip of the nose cone and NOT the end of the body tube.
Apply a small amount of epoxy on the launch lug line about ¾” long on the CG mark.
Press one of the launch lugs into the epoxy and ensure that it is aligned with the launch
lugline.Youcansitedownthetubeandlookthroughthelaunchlugtomakesureitis
straight. Similarly epoxy the second launch lug about 1/2” from the aft end of the body
tube. Site down both launch lugs and make sure they are both aligned. If you have a ¼”
launch rod, you can use this to ensure that both lugs are aligned properly.
Step 5 – Forward Section Assembly
Insert the eyebolt through the hole in the center of the bulkhead and secure using the
washer and nut. IMPORTANT: Apply some epoxy to the nut and eyebolt threads
to ensure the nut doesn’t come loose later. Apply some epoxy to the inside of the
coupler and push the bulkhead in so there is about a 1/8” to ¼” of coupler exposed. After
theepoxyhasset,applyalletofepoxyaroundtheinsideedgeofthecouplerbulkhead
joint.Nextmarkthecoupler2”fromtheforwardedge.Applysomeepoxytotheinside
of the forward body tube section and slide the coupler up to the mark. There should
be 3” of coupler exposed.
Make sure the coupler is
straight and the body tubes
are aligned properly when
they are assembled later.
over the forward centering ring) Spread some more epoxy on the inside edge of the
body tube before sliding the rear centering ring into the body tube. Continue sliding the
assembly inside the body tube until the aft end of the motor tube is even with the aft
endofthebodytube.It’sagoodideatotesttanineachslotherebeforetheepoxy
sets. Hold the body tube with the motor
tube assembly down until the epoxy sets.
Make sure the weight of the motor assembly
doesn’t cause it to slide out of alignment.
Next, epoxy one of the couplers into the
forward end of the aft body tube leaving 2 5/8” of the coupler exposed. The coupler will
coverpartoftheforwardnslots-makesuretheuncoveredsectionofthenslotislong
enoughfortheforwardntangs.Itisagoodideatotestttheforwardnsintoeach
slot before the coupler glue dries. When the coupler epoxy dries, attach the long middle
sectionofthebodytubetotheaftbodytube.Last,usingadoorjamorsmallsectionof
anglestock,pencilalinehalfwaybetweentwoofthensthatextendsfromthefrontto
the back of the body tube. This line will be used later to align the launch lugs.

Step 6 – Final Assembly
Insertthelargestmotoryouintendtoy(orsimulatetheweightwithansubstitute).
Ensure the CG is forward of the recommended CG. The CG is measured from the tip
ofthenosecone.IftheCGisbehindthespeciedpoint,addweightinsidethenose
cone by pouring lead shot into the nose cone tip and adding some epoxy. IMPORTANT:
Screw in a screw through the plastic nose cone into the lead to hold it in place.
Grind or cut off the screw head before lling and applying the nose cone nish.
The epoxy will not stick to the inside of the nose cone and if you do not anchor
with a screw, the liftoff force will cause the weight to become dislodged causing
an unstable model.Youcanalsoplacetheleadinthebaseofthenoseconesothatit
cannot become dislodged during liftoff, but you will have to use more weight.
Yourmodelisnowreadytopaintandapplythedecal.Toapplythecutletteringdecal,
carefully remove the backing from the decal - the individual letters will remain stuck
to the top carrier. Next, position the decal were you would like it and carefully smooth
out the top carrier to ensure the letters are securely attached to the rocket body. Last,
carefully remove the top carrier making sure the letters stay attached to the rocket body
and are not lifted with the carrier.
Step7–FlyingYourModel
Attachtheendoftheshockcordandtheparachutetothepayloadsectioneyebolt.Youcanalso
attachthechuteprotectortotheshockcordjustbelowthat.Whenpackingyourchute,wrapthe
chute protector around the chute with the opening in the chute protector facing forward. Always make
sureyourchuteiswellprotectedasthehotejectionmotorgasseswillmeltthenylonchute.
IMPORTANT: always use positive motor retention to secure the motor. Failure to use motor
retention will cause the motor to be ejected instead of the parachute making for a dangerous
ballistic reentry.
IMPORTANT: some motors do not have a thrust ring that rides against the back of the motor
tube. You can construct a thrust ring by wrapping a ¼” wide strip of masking tape around the
aft end of the motor until you have a layer of masking tape approximately the same thickness
of the motor tube. Do not y without a thrust ring as the motor will y through the rocket
causing a dangerously unstable free ying rocket motor.
IMPORTANT: always remember to check your balance point and ensure your CG is ahead of
the specied CG point.
IMPORTANT: Always follow the NAR safety code and remember that rockets are not toys
and can be dangerous if not prepared and used properly. If you are a beginner, it is a good
idea to y with a club or other group of experienced rocketeers until you have gained some
experience.
IMPORTANT: In no event shall Madcow Rocketry be liable for any direct, indirect, punitive,
incidental, special consequential damages whatsoever arising out of or connected with the
use or misuse of it’s products. The buyer assumes all risk and liability resulting from ANY
use of any and all products sold by Madcow Rocketry. Your purchase and use of any Madcow
Rocketry product constitutes your agreement to and acceptance of these terms. If you do
not agree to these terms and conditions, you must return the unused product in resalable
condition for a refund or credit.
IMPORTANT: Please contact us via phone or email if you have any questions about
constructing or ying your model.
24338 El Toro Rd #E-134
Laguna Woods, CA 92637
949.547.8847
www.madcowrocketry.com
©2006 MadCow Rocketry™
®