My new rocket is here, and it's one I have been drooling about for a while... the Extreme Wildman!  I guess I have a thing for 4 inch rockets.  My level 1 was a 4 inch Arrow launched on a 38MM mount.  My level 2 was a custom designed rocket I call the Heritage, a 4 inch with a 54MM mount.  My level 3 will (hopefully) be the Extreme Wildman, a 4 inch with a 75MM mount. :)

Every part of this rocket has been a blast so far.  The kit comes with a lifetime guarantee as long as you follow the instructions to the letter and Tim at Wildman Rocketry was very happy to fulfill my order with all the construction materials required to get the guarantee.  I am still waiting for the nosecone, but the rest of the rocket is here and I found some time this afternoon to prep most of the rocket for glue.  You know how this part goes; it's all drawing lines and sanding, and sanding and sanding.  And sanding.  Sanding is easily 50% of the time you spend building your rocket if you aren't glassing it yourself.

The interesting part today was drilling the injection holes for the internal fin filets.  If you've never tried to drill through fiberglass before, be warned, it's more difficult than it sounds.  

The first holes I drilled were the vent holes, and it was immediately evident that the drill bit was not going to cut through the fiberglass tube easily.  Naturally I applied a little extra force and it appeared to move faster.  Then all of a sudden, it broke through the tube.  I pulled the bit out and looked down the tube, where instead of drilling through cleanly, it had pushed the fibers in, pulling off an entire ring inside the tube.  I tried to peel it and just made it worse.  I ended up cutting the thread off with scissors and then sanding the inside of the tube.  Unfortunately I did not take a picture of this mess.

For the next hole, I decided to start with the smallest drill bit I had and slowly increase the size of the bits used until the hole was the desired width.  The same thing happened with the small bit, however this time I was prepared to sand the problem immediately and the successive holes drilled cleanly.  This method takes forever.  Instead of drilling one hole slowly, I now had to drill the same hole 3 times slowly to get it to spec.  That's okay though, slow and steady wins the race.  The next 3 pictures are at various stages of the process for the 12 other holes used for the interior filet injection.

To do these 12 holes took about two hours.  Now it's time to move on to actually putting the fin can together.

My level one certification was an awesome experience.  I spent almost a full year building the rocket and talking with people from Birmingham Rocket Boys about how to certify.  My dad and I made a trip out a launch hoping to fly only to find out the rocket still needed a few things...

• Fireproofing for the parachute
• Launch lugs
• A motor casing
• A reload

We must have looked like fools out there, but it was a ton of fun (despite the 7 hours of driving).  As soon as we got home, I had the launch lugs and fireproofing ordered.  The casings were a little more than expected then and I waited for Christmas so I could send a letter to Santa...

The day of the flight I was really nervous, but thankfully everyone at BRB was extremely helpful and guided me every step of the way.  The rocket launched slightly into the wind and went up to about 1200 ft, the motor ejection went off precisely at apogee and the parachute inflated.  The rocket landed on one of the fins, and cracked the filet but I still passed.  Boy was I relieved.

My dad surprised me on that trip having built a rocket of his own to certify with, but he had left the motor adapter at the house, and was unable to match my flight.  We ended up staying all day to watch all the rockets and had a blast.  

As we left, Kim from BRB said:

Congratulations, now you can really start spending money.  

I never gave much thought to it then, but I completely understand him now as I am preparing for my level 3 certification.  Then we hopped in the car for the drive home.  Every one of our trips back is filled with wishes and theories about the next awesome adventure we're going to have in rocketry.

SCRATCH BUILT CENTER RINGS AND BULKPLATES

I realize that center rings and bulk plates are far from being the most expensive or glamorous components of rocket-mongery, but let’s face it you can’t build a high power rocket without them. Even a simple dual-deployment six inch diameter rocket needs at least three center rings for the motor tube and two bulk plates for the electronics payload bay. If the rocket is more complex and of a heavier build you may need two more center rings as seats for the payload bay’s bulk plates, perhaps another bulk plate to compartmentalize the payload bay and a bulk plate for the fiberglass nosecone to protect an antenna, GPS and data transmitter from ejection gasses. At $6-$9 dollars apiece rings could cost $35--$70 for one rocket!

Granted, less than $100 not going to break the bank, but there is a less expensive way to obtain these essential components -- make them yourself. If you own a router, a router table (or in lieu of the table a two foot long by one and a half foot wide piece of rigid board -- plywood, a chipboard shelf or the like, and at least two screws with the proper thread to fit you router to attach it to the board) you could make all the center rings and bulk plates you could ever desire, of any size, for a fifth of the price of buying them pre-made. Not only that, you could also immerse yourself in the immense pride of having made them yourself – satisfaction guaranteed.

I begin making rings and plates by drawing an outline of the outside diameter of the actual tube I’m making the components for on my ring material, in this case 3/8” seven ply plywood. I take a pencil and trace around the circumference of the tube. I can buy a 12” X 24” sheet of seven ply plywood for $12 and make six six inch rings from it – pretty good deal.

Next, find the center of the circle you just drew on the piece of plywood. This is the hardest part of the entire process and it’s quite simple to accomplish. If you remember your high school geometry you will recall that the perpendicular bisector of any chord of a circle will always pass through the center of the circle. So draw two chords inside the circle, mark the center of the chords and then take a right-angle triangle to draw a perpendicular line from the marked centers of the chords – they will cross at the center of the circle.

A couple of fine points –

• Draw chords of an even number of inches to make marking the center of the chord a snap. The center of a four inch long chord is two inches. Make it easy.

• Trace the tube diameter with one point of the circumference of the circle toughing the edge of the ring material (as seen in the above photo). This actually makes starting the routing much easier; set that edge of the ring material right against the router bit to start the routing. My experience is that the routing a ring like this will produce a ring that perfectly fits the inside diameter of the tube.

• I use a six penny finishing nail to spin the ring on as I rout it. I drill a 7/64” hole in the center point of the ring then slide the six penny finishing nail into the center hole. Once I have the plywood set against the router bit (as seen left), I set the six penny nail in the center hole of the drawn ring into board I’m using as a router table.

• If you’re making multiple rings out of one piece of plywood at the same time, leave ½” between each drawn ring to give the ¼” router bit the space it needs to make the cuts.

It’s easier than you think to make perfectly round professionally looking center rings and bulk plates for the rockets you love to build.