After cleaning up the remaining minor details, such as drilling port holes, the rocket was complete as far as I could take it in NYC. I do not paint my rockets until they have been tested, with the intent of saving the bulk of the finishing time on a rocket in the case that it fails it's first time out. Once it survives an actual flight, I take the time to make it pretty. Well... as pretty as my adolescent spray paint skills can make it. :)

The next step of the journey involves getting it to the launch, because as my dad assured me, trying to get a rocket past airport security is lunacy, motors in tow or not. The only other real option is to ship it to where you are going and pick it up once you get there.

As it turned out, there were some more things I was planning on doing at the fields, which I wouldn't have to if I shipped it to Jimmy, who I will be meeting in Atlanta and driving up with he and his father. Since Jimmy already picked up my rocket box from my dad, he would be able to take care the even more last minute things, like drilling holes for shear pins, attaching the rail buttons and ground testing the electronics.

Planned Flights

If you haven't noticed, we have a flight log for every rocket here on rocketclubs.com which you can find by clicking on the name of this rocket in this article's header, and then clicking on the the icon on the right which looks like fire coming out of a rocket. Or you can just click this link. If you log a flight for a future date, the flight will be marked as planned until that date, and then it will automatically switch to the main flight log.

If you click the date of a flight on the flight log page, it will take you to a launch details page. This page has all the details of the launch, including a complete list of the motors used, projected launch date and altitude. We have a number of planned features for this page, which we will announce when they are ready.

In the meantime, please check out my planned flights, and you'll see that I'm going for a lot of firsts at ST2011, first K motor, first mile high flight, first electronic recovery system and first dual deploy. Hope to see you all there!

Now that I have solved the problem where my motor tube was too large, I can now complete the fin can!

Completing the Fin Can

As soon as I finished sanding the crap out the motor tube centering rings so I could put the parts together, I went ahead and finished it up by epoxying it all together.

The next step was to insert the motor tube assembly into the lower air frame. I used the method I learned earlier in this process and put the inner ring of epoxy in first, then slid the motor tube in half way and put a second ring around the base. This worked like a charm. I let this section dry for a few hours, and prepared for the next step in which I would put the third centering ring up near the end that would eventually connect to the rest of the rocket.

The epoxy had fully set before I started this process, and I am very glad I let it because otherwise it would have destroyed the fin can because the extra epoxy on when inserting the last centering ring caused a VERY tight fit that ended up putting a lot of pressure on the motor tube.

I had dry fit this section and planned it out fully before I ever glued the motor tube in place, so I knew better than to try and dry fit the last centering ring after the motor tube was stuck in place. At this point once you put the last centering ring in, taking it out would be almost impossible.

The basic plan goes like this:

1. EYE BALL IT, MAN, DOUBLE CHECK, TRIPLE CHECK!
2. Mark the coupler/bulk plate assembly half way with a pencil
3. Put a bunch of epoxy around the edge of the tube
4. Slide the centering ring in just over a half inch
5. Insert the coupler/bulk plate assembly, spinning it as it goes in until it gets to the pencil mark
6. Turn the entire assembly upside down and hold it in place

Attaching the Fins

Once the motor tube, all centering rings and the bulk plate assembly have dried and are firmly in place, the next step is to attach the fins. I differ from the kit instructions when it comes to fins. The instructions call for you to leave the bottom centering ring off, tack the fins in place and drain epoxy along the fins. I prefer to tack the fins in place, drill a hole next to the fins and use a baby feeding syringe to insert epoxy into a closed cavity.

Either way you have to tack the fins in place. This is easy enough, just put a nice generous amount along the fin slit and a strip along the edge of the fin which will attach to the motor tube. Then insert the fin and use tape to hold it in place. Using this method you can put all the fins on at once and be prepared for the fillets a few hours later.

The only bit of advice I have for the fillets so far is to use tape to mark off where they should end. This makes clean up significantly easier by removing the need to sand off the excess. Just make sure to pull the tape off well before the epoxy starts to harden.

One of the things that has always confused me about Public Missiles kits is that the instructions tell you to attach the nose cone by poking out the thin little circle of plastic on either side of the nose cone and looping the shock cord through it. Seriously, check out step 8 in the instructions for this kit. How I'm supposed to string a 3/4 inch nylon strap through a quarter inch hole without destroying it is beyond me.

Problem - Attaching the Nose Cone

Up to this point, building the rocket has been a pretty smooth process, with nothing more than the usual kinks of trying to fit my forearm down a 3in tube and realizing the instructions are your friend for the most part. In this case however, I think the instructions for step 8 were written for a rocket which comes with a shock cord small enough to do this, and then to avoid rewriting step 8, they just let you figure this one out for yourself. And that's exactly what we are going to do in this article!

Research

I always look first for first hand accounts of someone else doing it before me. If you can find someone else describing problems in their own words of a first hand account, you will likely find yourself in the same situations and more prepared for the problems they were not expecting.

The instructions do suggest using a kwik-link, which is just a small loop with a screw tight hole in it. In this case, I have my own first hand account. My second high power rocket ever was a Public Missiles Quasar and I purchased a kwik-link with it to solve this problem as suggested by the instructions. When trying to poke the thin plastic out with an X-acto knife as shown in the instructions, it took some work to clean it up and even once opened completely and cleaned up, the hole was still too small for the small kwik-link to fit through it! I ended up wiggling it back and forth for a minute or so until I finally forced it through and on the very first launch, the force of the ejection charge blew the nose cone clear off, tearing right through the plastic!

Another solution is to just forego the need to attach a shock cord to the nose cone at all by adding a payload bay as the top section to your rocket. If you plan to go this route, it is advisable to have made the decision before you purchase the rocket to make sure you have the extra airframe and coupler bulkhead. This solution works great for small single stage recovery projects as a place to toss an altimeter or some extra weight depending on the motor you are using.

At the November 2010 monthly club launch for Phoenix Missile Works (NAR682, TRA81) I spoke with Richard who had another idea. He had a similar nose cone and showed me how he had attached an eye bolt to hole in the center of the nose cone which was much stronger than anything I had seen before. It was more work than the other methods, but you could feel the strength of it when tugging on the shock cord.

Solution - Eye Bolt in the Nose Cone

In the story about tearing through the plastic with the kwik-link attach, the problem almost certainly boils down to me using too much black powder or some other cause than the strength of plastic hole, but I like to have as few concerns as possible when launching a rocket, and this experience kept me from wanting to try this method again.

This rocket was also designed to have the electronics in the center section. Adding another payload bay at the top was not in the original plan and the weight was distributed perfectly for larger motors. Cross that option off the list.

Since I saw the eye bolt solution I've wanted to try it out. The instructions Richard gave me involved cutting a hole in the side of the nose cone to pour epoxy into which would then be epoxied over itself and sanded back to match the original wall of the nose cone. This seemed like a lot of extra work, so instead picked up some 5 minute epoxy, mixed it and quickly but carefully crammed as much of it into the hole as possible in 30 seconds. I used enough to be sure that it would fill the small area around the nosecone when turned right side up.

Next I screwed an eye bolt into the tip, I made sure to buy one large enough that it fit tightly inside the hole, turned the whole thing right side up and held it there for 5 or 6 minutes while it all settled and reached a semi set state. Then I flipped it back over and added some more epoxy to the outside to ensure there were a firm grip on the inside and outside of the nose cone. At this point make sure to clean up the excess quickly to avoid sanding later. I let it rest standing upside down and called it finished. About an hour later, it felt almost as strong as the one Richard had shown me!

Construction of the CPR3000 is a long process. In fact, the instruction booklet for it is larger than the entire Spitfire kit instructions! Naturally, the more steps there are, the more planning it takes and the more things need to be checked to ensure it is done correctly.

There are really 2 major parts to building the CPR3000: getting the inside tubes prepped and attaching the inside tubes to the airframe.

Building the Actual Electronics Bay

This part is easy.

1. Epoxy the blue screw parts to the electronics tubes, pay attention to line up the notched section with the groove in the electronics bay tube, clean the excess and wait to dry
2. Attach the centering rings tightly against the blue screw sections, epoxy, clean, wait to dry
3. Put a small strip of epoxy along the length of the tube (not covering the groove on the larger piece), attach a separate piston strap along the length of epoxy, tape sufficiently, wait to dry
4. Slide the grooved centering ring over the ends of the piston straps, and a half inch down the electronics bay tubes. The fit should be pretty tight. Roll up the dangling piston straps and put them inside of the tubes, tape over the end to make sure no epoxy gets inside them! Apply epoxy to the centering rings, wait to dry

Congratulations! You have now built the electronics bay inside portion. The tube on the left in the picture above is on step 3 and the tube on the left is on step 4. Once you reach this point, I highly recommend dry fitting your rocket again to make sure everything still fits.

Attaching the Electronics Bay to the Airframe

This part is hard.

Inserting each side has it's own problems. The first side can be whatever side you want it to be, and I choose the shorter section. When dry fitting, I found it hard to believe that the coupler would fit between the sections if care wasn't taken to use a very minimal amount of glue which is not one of my strengths. I decided to glue the coupler in to one of the tubes first, then I would be able to slide the entire assembly through the rocket, making a perfectly flush connection, resting the inside assembly against the coupler.

This worked as intended, and I have a very nice and flush connection here. This did create a problem on the other end however, where I now had to maneuver glue in the long side of a 3 inch airframe to glue the inside centering ring. This is never a good position to be in, and I could write up the 5 or so ways I have dealt with this situation in the past as it's own post. This time I mixed up some epoxy in a small plastic ramekin and slid the whole thing in there, then flipped it upside down and waited for it all to slowly ooze out.

The trick is that you cannot get any epoxy on the inside of this tube or else you'll have to sand it off after the fact for the piston to function correctly. Also, the seal in this part of the rocket has to be complete or else you create the chance for the expanding gases to affect your electronics.

In hindsight, if I had just followed the instructions here, the coupler would have fit just fine... but might have inadvertently glued the two halves together for good. If I were to do it again today, I would follow the instructions in the kit, but also glue the coupler in at the same time so that I would still get that flush fit.

For the other half, I only glued the centering ring on the piston side first. I was afraid if I tried to do both as the kit suggests, I would have glued the two halves together since I decided to attach the coupler already. If you follow all the instructions in the kit, it tells you not to glue the coupler in until the very end, which would have prevented this situation. But in this case I still got the hard part done first, and this time without having to put my arm down a 3 inch airframe!

In the above image you can see the two sections connected at this point, and they stood here until the epoxy had set. In the picture below, the parts have been separated and the close centering ring was epoxied in.

At this point, the only thing left to do is break the piston strap out of the electronics tube and attach the pre-made piston assembly. Don't forget the D-ring! At this point you can attach the parachutes and nose cone, and your CPR3000 is done!

Today's article was going to be about the completion of the CPR3000, but there are still a couple more steps, so that will have to wait until tomorrow. In the meantime I started working on the fin cans. The 38mm fin can dry fit perfectly and was ready for glue right away, so I put the easy stuff together. The 54mm motor mount did not dry fit so nicely.

Problem - The Motor Tube is Too Big!

The 54mm motor mount was ordered as an addition to the kit so I could launch the newly two stage recovery Spitfire on some larger motors.

This isn't the first time I've gotten a motor tube which came a little to big, my Public Missiles Quasar came that was as well. At that time I broke the fragile 2.1 in to 3 in centering ring while trying to sand the inside of it. This was a major pain and lead to some extra creative gluing which took about 5 times the amount of glue and time as it would have taken had it fit in the first place.

On the current rocket I remembered this experience from the last rocket and decided to be a little more careful and not try to force pieces in place. To let you know how much it was off, I couldn't even fit the HAMR motor retainer on the motor tube, which has never happened before.

Research

There are essentially 2 ways to fix a motor tube that is too big around. You can either sand the outside of the motor tube or sand the inside of the centering rings to fit.

If the motor tube is very large, or is a large way off of the needed diameter, sanding the inside of the centering rings requires less work. If your centering rings are small, typical of many near minimum diameter rockets, they can be fragile and extra care should be taken to prevent breaking them when sanding.

Solution - Sand Inside of Centering Rings, With Care

Last time I ran into this problem, and broke the centering ring, it was because I tried to sand the inside of the centering ring with fine grit sandpaper and it kept ripping. This frustrated me and I tried to sand it harder to make it go faster.

This time I realized that a more coarse grit sand paper would make the sanding go faster and it was going to be glued over anyway so looks were not important. I got a hold of some 60 grit sand paper, but I was still running into the same problem with it tearing often because flat sand paper is hard to mold to the inside of a centering ring. Then I ran to Home Depot to look for a solution and came across the marvel that is sand paper sponges!

The technique here is to hold your fingers out so that you can spin the sponge without running into your fingers constantly. When my hands got tired (there were 3 centering rings to do), I switched it up and spun the centering ring around the sponge. Whichever technique you are using, be sure to switch directions when it gets smooth and it goes much faster. This is a way to be very gentle with the rings while at the same time getting the work done in a timely fashion.

After a few short minutes, the centering ring finally fit on the tube.

Once I had finished the 3 centering rings, I was very happy, but the motor retainer still did not fit smoothly on the tube, so in the end I had to sand the tube as well. That didn't take too long and then I was ready for a good dry fit.

Next time: the CPR3000 build and recap (seriously this time).

The Spitfire comes with a 38mm motor mount, which is great if you are building the kit as it comes. When I added the dual deploy setup however, that added a lot of weight to the design, limiting the number of acceptable motors I could use with this kit. The solution was to write the guys at Public Missiles and ask them to cut a second fin can with a 54mm motor mount!

Dry Fit

Now we are in the construction phase and the first step is to cut the existing 3ft airframe in half, per the retro fit instructions on the CPR3000. Since I moved to NYC, I left most of my rocket building supplies at my dad's house thinking there wouldn't be enough room to store them in my new apartment. I needed a saw for this, so quick trip Home Depot and I was ready to go. It only occurred to me once I was in Home Depot that it might have been a better idea to just bring the airframe to the store and have them cut and sand it with bigger and faster tools.

After sanding the rough edges, I was ready to dry fit the rocket completely. It's important to dry fit for a couple reasons:

• Make sure you have all the pieces
• Make sure all the pieces fit together
• Help you plan out which order build things
• Make any last minute changes before you're committed

Problems

While dry fitting, I realized a couple of things. First, my design uses rail guides, and I completely forgot to order them with the second motor mount. Second, I did not order a bulkhead replacement for the strap and D-ring bulkhead that comes with the CPR for the fin can. This turned out not to be that big of a deal because I also ended up with an extra piston, with it's own strap bulkhead, so I put both of those bulk heads together to create one with a small enough hole to use an eye bolt.

The 54mm motor mount also felt too thick. I had trouble even putting the motor retainer on it, which slides easily on to every other rocket I have ever built. The centering rings would also not go on it. This problem is easy to solve, just sand it, but I put that off for now because I want to take it to Home Depot and use one of their power sanders to fix it up quickly.

Decisions

The CPR instructions call for the coupler to be placed in the airframe after gluing the aft assembly inside the airframe. I chose to glue the coupler in place first, that way I can slide the aft electronics bay assembly in from the other side and get a flush fit against the coupler. On the 54mm fin can, I will do a similar sort of thing to give an extra point of contact for the part of the rocket which takes the brunt of the force while the motor is burning.

Other than that, everything looks pretty standard, so I went ahead and started gluing the easy parts together.

Next time: some modeling info.

Roctober skies 2010 was high on my list of events I was looking forward to after returning home from my honeymoon. I didn't get to launch very often in 2009-2010 because of schedule and saving for my wedding, so this was a huge event for me. Jimmy was also going for his level 1/2 certification flights as well and we even had two close friends and Jimmy's dad come just to watch!

The day was very exciting and a great time was had by all. A few days later I received a phone call from Bob Haas informing me that I had won a Public Missiles Spitfire in the raffle, as well as an assortment of plastic motor protectors! Hooray!

Problem - Make Spitfire Dual Deploy

The Spitfire kit is a very clean and simple kit, perfect for the entry level high power flyer, or someone looking for a rocket they can easily launch 3 or 4 times in a day with decent power. I'm at the point now, however, where I am completely devoted to learning something new from every rocket I build by doing something I haven't done before on each build. For my level 2 certification, I built a big 4 inch rocket, which I named Heritage because it's first flight was on father's day, with the intent of making it dual deploy, but in the end realized I hadn't spent enough time on the design before I bought parts and started epoxying parts together. In the end I scrapped the dual deploy concept and used motor ejection for a successful first attempt level 2 cert.

As soon as I got the Spitfire, I knew I was going to modify it to make my first dual deploy rocket.

Research

The biggest problem with the Heritage rocket was that I was trying to just do it all myself, without looking up how other people had done it to find out what works and more importantly, what doesn't. This time around I spent some time looking at the designs by members of the Phoenix Missile Works family as well some commercially available solutions and I read through Modern High-Power Rocketry 2 for ideas.

The best way to learn something is to spend as much time as possible around people who know it better than you do. When at a launch, walking around, looking at and asking about other people's rockets is the best way to get ideas and solutions to problems you are having with your own rockets. The people at Phoenix Missile Works were most helpful on just about every topic involved with building a rocket. They had a number of designs for electronic and dual deployment setups, most of which were built for custom for each rocket.

Next I read through the Modern High-Power Rocketry books for ideas. Again the ideas were more or less custom per rocket, although I have say this book is great. A few more pictures on each page and they could remove the words all together, that's how detailed the pictures are. This book was also the one of the only sources I checked when designing my first dual deploy rocket, which never came to fruition.

The commerically available solutions are different in that they are already designed for you. This has major benefits for the rocketeer who is just looking to fly and recover their rockets. It takes away some of the "have I done everything I need to, or am I about to lawn dart" thoughts that run through your head on the first launch of any major new project. Aside from that, most manufacturers that make rocketry electronics and some rocket vendors have avionics bay kits available for their products, so finding one that works with your rocket shouldn't be much of a challenge.

Solution - CPR3000

In the end I chose the CPR3000 as the best solution for my rocket. The biggest deciding factor was that I get to skip the design part of it which is not so much my goal right now as gaining experience using dual recovery. Also, the guys at [Public Missiles][1] have always been quick to respond to my questions, respond with insightful answers and the Spitfire is one of their kits. I also liked the simplicity of the CPR3000... I mean it comes with an instruction booklet, and if something does confuse me, I know they will be quick to answer any questions I might have.

Next step: dry fit and one more idea to really give this rocket a workout.