And I'm finally back at it.  I can't believe it's actually been a month since I posted.  My bad.  I epoxied the second forward centering ring in place last night.  Again, I had to use my masking tape shims to center it since it was pretty loose on the motor tube.  This one was a little bit trickier since it will essentially "seal" the fin compartment.  Basically, the second forward ring and rear centering ring hold tight against the front and rear of the fin.  The placement of these is critical to hold the epoxy when I make the internal fillets.  It's not that hard to do, just requires a bit of forthought and care.  Everytime I mix up a new batch of west systems I get a little bit nervous.  I love the epoxy, but I'm always worried about something I might have fortgotten that will be impossible to fix once the epoxy cures.  I forgot to get a picture, but I'll fix that tonight.

On a side note, Northern Colorado Rocketry's Mile High Mayhem starts today.  Absolutely one of my favorite events of the year.  Whitney and I will head up early tomorrow morning for two days of launching.  Hopefully we'll get some good pictures to post here when we're back.  I plan to test some shock cord management methods on my 4" WHAMmer.  I'm hoping it will yeild some good results that can be applied to this rocket.

This is a dry fit of the Intimidator 5.  Again, we have my trusty assistant on the right, now age 10 (gasp!)  Gives you a bit of scale for the current project.  Oh, and yes, that is me on the left...

Next few nights are pretty busy, not sure I'll be able to get my build groove on, so here are some pictures that I kinda like showing the progression from Level 1 to where I am now.

This rocket is a PML Phobos, it was my L1 certification rocket on an H-128.  My trusty sidekick Whitney is seen holding it up.  I think she was about 4 years old in the picture.  Dig the lightning bolts.

The picture below is me prepping my Level 2 rocket, the WHAMmer.  This one was named as an acronym for my family, W (Whitney), H (Hobbes, my labrador), A (Annie, wife), M (Madison, youngest daughter).  It was my own design and built mostly with PML components.  Funny part is, I clearly remember loading that motor, an aerotech J350, and being very intimidated by it's size.  Funny that whole WHAMmer would almost fit inside the booster section on my current project.

Here are a few more pics from my Level 2 flight day.  For the record, if any of my TAPS are reading this, I got 100% on my L2 written test.

This last picture was taken by my Dad.  It was one of those really awesome days you have, but maybe don't realize just quite how awesome until later.  Level 2 certification is a pretty big deal, there is a written test component, then the flight.  By definition, you've never flown anything with as much power as what you are attempting, unless it's not your first attempt.  This was my first, and I was very nervous.  Dad and my brother both came up to help out and provide moral support.  The weather was perfect, the flight went great, and I think they were both a bit shocked at just how powerful the rocket was. 

Dad passed away a few years ago.  He and I did a lot of really cool things together, but that day up at the launch will always be one of my favorites.  We were all excited and having fun.  No work stress, no phones ringing, no yardwork, no real reason for anything other than having a good time.  I think that's probably one of my favorite parts of rocketry.  The beautiful remote locations we fly at and no outside world distractions.  It makes it so easy to just concentrate on nothing but having a good time.

Next step will be to epoxy the rest of the centering rings on.  For this build, since the motor mount tube to airframe wall gap is so narrow, and the fins are so long, it would be very difficult to get a good internal fillet working from the bottom of the airframe as I normally do.  Instead, I will install all 3 centering rings on the motor tube, then epoxy the motor mount in place.  To get proper strength for fin attachment points, I will drill several 1/4" holes along the root edge of the each fin, on both sides, and inject epoxy through the holes.  This will essentially "case" the fin joint both at the motor tube and airframe tube.  This step is probably overkill since I will be laminating 2 layers of carbon cloth tip to tip over the fins, but solid fin joints are never a bad idea.

While fitting the motor tube and getting everything properly aligned, I usually install, remove and reinstall a dozen times.  To make removing the centering ring easier, I decided to mount the Aeropack motor retainer first.  I'll just say this, Aeropacks are awesome.  Lightweight, clean design, nice machining, bombproof and easy to use.  Best motor retainers available if you ask me.  This is my first experince with the flanged version, and I've decided they went with 12 screws just to give me every possible opportunity to screw up the install.  I am sure after cranking down on these screws that 4 would hold it just fine, the other 8 are just to make me suffer. For the record I actually flirted with doing it right...

The first picture shows the "jig" I used to center the retainer over the motor mount tube.  I had to use a piece of PML phenolic coupler since I don't have any 98mm motor casings.  Once I had it perfectly centered and taped tight enough that I was confident it wouldn't move, I took a hammer and awl and punched marks in the center of each of the 12 holes.  I then drilled one hole to be the guide, as shown in the picture.  Each subsequent hole I slid the retainer back over the centering ring, checked to make sure my punch mark was centered, then drilled another.  I swear I must have installed and unistalled the screws 20 times checking to make sure the retainer stayed perfectly centered over the tube and all the holes fit.  Each hole was tapped with an 8-32 tap and the 11 screws went in smooth as butter.  Almost perfect... The last screw somehow I just barely missed.  After enlarging the hole just a bit I managed to get it in, but tonight I will probably fill that hole with epoxy and fiberglass so I can redrill it perfectly.  Even the that hole still held the screw pretty tight, but it bugs me, so a fill and redrill is gonna happen.

It occured to me since deciding to document this build as a blog (still don't know what blog means), there may be people who take a look at this and have no idea what I'm talking about, and really don't know rocketry.  So I've decided to back up a step.


Level 3 Certification is a milestone challenge by just about any measure for a  model rocket enthusiast.  Commercially available hobby rocket motors are regulated, and each certification from 1 through 3 allows you to obtain more powerful motors.  Earning a Level 3 certification allows someone to buy, possess and fly the biggest motors available legally.  The subject rocket for this blog will stand over 10 feet tall and weigh between 25 and 30 lbs.  By most peoples standards, that's a big model rocket.  The motor for this flight will accelerate the rocket from 0 to 932 mph in about 3.5 seconds.  That gives you a rough idea of the power we're talking about. 

This is a picture of the parts I'm starting with.  That's an Alpha 3 standing in front, or for you non-rocket geeks, a bottle of Molson for scale.  Obviously, as the build progresses, you'll see the whole thing in it's 10+ feet of glory.

4/15/2012  Construction Begins

Drilled the upper centering ring and epoxied it to the motor tube last night.  All 3 rings are too big for the motor tube, so I used masking tape to make shims in order to keep it centered.  I’ll pull the tape out after tack gluing and make a full fillet on each side of the ring.  Mask looks dorky but glass dust is worse.

The final plan for recovery harness back up is to attach about a 3 foot section of ¼” Kevlar to the u-blot shown below with a quick link that will attach to the eyebolt in the motor.  The thing I didn’t like about using a small string or something else to keep the eyebolt from unscrewing is that different size motor (ie different case lengths) would require different length material.  It seemed too awkward to be tying off to the motor once loaded into the rocket.  With this method, the tie off kevlar is long enough to drop through the motor tube and attach to the eyebolt before loading the motor.  And with 3’, it’s long enough to accept the biggest motor that the booster will fit.  I know it’s probably overkill, but I’m sure it will be a really nice back-up that will never be needed.

It should be understood that this very simple "back up" plan for recovery harness attachment has been stewing around in my head for literally months.  I just can't seem to get comfortable with a single forged eyebolt in the forward closure.  The thought of it unscrewing on descent was driving me nuts.  While I don't really think that will ever happen, I feel much better about the whole setup now. 

L3 Build Summary

Bret Packard

TRA #11257 L2

NAR #83659 L2

            My goal for this build is to create a very strong, reliable large rocket that minimizes prep time and complexity in order to provide the best chance for a successful flight.  The basic framework I have chosen for this rocket is the Performance Rocketry Intimidator 5. The Intimidator 5 is a 5” diameter, 10 foot tall all G-10 fiberglass rocket.  The rocket will not be optimized for altitude, but rather emphasis will be placed on durability and stability.  The rocket will be constructed using primarily West Systems epoxy with West Systems 205 and 206 hardeners and various fillers as appropriate.

            The booster section is 48” long and has a 24”, 98mm motor mount with fins that will attach directly to the motor tube.  The fins will have joints filleted to both the motor tube and inside airframe using epoxy with chopped carbon fiber.  The fins will also have 2 layers of 5.9 oz. carbon fiber laid tip to tip for additional reinforcement.  A 98mm Aero-Pack motor retainer secured with 14 stainless steel screws will provide positive motor retention.  A 50 foot long ½” tubular Kevlar shock cord will be attached via a stainless steel quick-link and forged eyebolt threaded into the forward closure of the motor hardware.  An anchor point will be installed in the motor mount to attach a Kevlar strap which will also be attached to the forward closure mounted eyebolt as a backup attachment point in case the eyebolt should ever come unscrewed.  A 24” drogue chute will be used to keep things falling in an organized manner.

            The electronics bay will be inside the 12” coupler tube.  It will house a Missileworks RRC2 and a Featherweight Raven.  Each altimeter will be wired completely independently of the other, including separate black powder charges, and separate power supplies.  Black powder charges will be determined by ground testing once the build is complete. 

            The 48”payload tube will house another 50 foot length of ½’ tubular Kevlar and a TAC-1 Cert 3 parachute.  A Garmin DC-20 will be mounted in the nose cone to provide tracking for the flight.

            The motor I have chosen for this flight is the 6 grain 75mm Cesaroni M-1590 Classic.  With the rockets expected pad weight of approximately 25 lbs., the initial thrust of the M-1590 of over 500 lbs. yields a 20:1 thrust ratio at ignition and a sustained thrust ratio of nearly 14:1, which is more than enough to achieve stable flight.  According to the modeling I have completed in Rocksim 9.0, the rocket reaches stable flight at approximately 24” inches up the rail at a speed of 44 feet per second.  The motor will burn for 4.7 seconds propelling the rocket to a maximum speed of 1,365 fps, then coasting for another 21 seconds before the apogee event occurs at an expected altitude of 13,500 ft.  Altimeters will be programmed to stagger ejection charges by approximately 1 second at apogee and main deployment at approximately 1,000 feet AGL.  The rocket should touch down approximately 3 minutes and 10 seconds after liftoff.  Any sooner than that is probably bad ;)