Due to my schedule, and the fact my local rocket club doesn’t fly experimental motors, I only get to launch EX motors once a year, and Midwest Power in Princeton Illinois. EX motors are just that – typically a rocket propellant you whip up yourself in your garage, or basement. The big advantage of manufacturing your own motors is you can control a lot more variables. Want the flames to be red? add Strontium Nitrate. Need to speed up the burn rate of the propellant? Add Iron Oxide. Need an even thrust level through the entire burn? Try a Finocyl core geometry. You get the idea.

For the last few years, I’ve been trying to push the limit on making a slow-burning propellant. This is much more difficult than changing up the chemical composition because the longer the propellant burns, the more exposure the motor hardware, nozzle, and liner will have to the heat and pressure. Worse, the core geometries with the longest burn characteristics (endburner & moonburners) tend to keep the heat and pressure focused on a particular part of the case for an extended period of time. Once a formula is stable enough to flight test, I typically try them first in an oddroc saucer. They are very light – easy to lift of the pad, very stable – no fin alignment issues, and don’t fly very high – easy to recover just in case…..

In 2011, my longburn test ended in disaster. The propellant burn was so low, the rocket never got off the pad and eventually burned through the motor case, destroying the saucer, rocket motor, and the pad it was sitting on. All of this was caught on video at Midwest power 9 for your enjoyment

Needless to say, I spent a year with the nickname “firestarter” by everyone that witnessed this first attempt.

     A year

later,  with dozens of changes and testing of the propellant formula, I returned to Midwest power in the hopes of a successful launch.  The good news is the launch was successful – the saucer zoomed off the pad. The bad news is my nickname may now be permanent… After a successful flight, the rocket caught fire on decent and started a small  field fire. Once again, I was left with a destroyed rocket and motor. Of course, my daughter caught the whole flight on her iphone while I was clicking away on the still camera. At least I have another year for research!

Saucer and 75mm EX motor ready for launch

launch sequence

And the recovery……

This is all I got back, some burnt carbon fiber and a ruined rocket motor

     What a great time. Special thanks to everyone who came out, and Tripoli Wisconsin for letting me ‘cut in line’ at the university launch.

Picked up the rocket from the Ultimate Paint Shop today. All I can say is: WOW!

The good news is they did a FANTASTIC job! Look at the paint on those fillets – all of my other rockets will look horrible in comparison. Oh well

The bad news is I have two days left to finish the rocket.

Things left to do:

a little rewiring on the AV-Bay. I found an intermittent short on one of the ematch wires. Better safe then sorry.

Need to weight all the parts and recompute the CD/CG. Determine if I need nose weight, then epoxy in the allthread into the nosecone. Also need to foam the nosecone, build some electronics compartments and install the forward bulkhead

I re-fit the AV bay into the upper sustainer, and retest the main parachute deployment. now that everything has been painted. I decided on redundant BP blastcaps for both the drogue and main deployment charges. Better safe then sorry, and I can always remove them later.

drill air holes, sheering pin holes, altimeter arming holes,altimeter breathing holes, and 1515 rail button mounting holes.

Sorry for the lack of updates. work and travel have taken over a bit.

T-2 weeks and counting until lift-off!

I’ve added a page for my pre-flight checklist. you can see it here: https://mylevel3.wordpress.com/pre-flight-checklist/ this is a work in progress, so let me know if you think I’m missing anything obvious.

My rocket now has a few sponsors! I took my rocket into a local automotive paint dealer, The Ultimate Paint Shop in Lake Bluff to get an early start on the paint job(weather has been bad in the Chicago area, they have an indoor paint booth). By the time I left their facility, I had two firm sponsors, with the possibility of adding more.

I checked with my TAP sponsors to make sure it would be ok to have ‘professionals’ finish the exterior – they were all for it. Feels a bit strange – I have no idea what the rocket is going to look like when they are done. I picked out the primary colors, but told them they could add their logo’s and names as necessary for the sponsorships. The one thing I can be sure of is the paint job will certainly look a lot better than if I did it.

In the meantime, I’ve been finishing up the programming on the Altimeters and prepping the GPS & trackers. I decided to add a terminal block for my raven to simply the connection process since it has a common ground. I also learned something new about my Marsa4. I’ve been running low on my ematch supply (Wildman ejection charge lighters), so I ordered a few Quest Q2G2 long’s to use as ematches. I use the Q2’s a lot for lpr rockets as they are very easy to set up, and are extremely reliable. The Q2’s require a very small current to go off. Turns out the Marsa4 puts out enough milliamps during it’s continuity check to ignite the Q2’s. Reinforces the “ground test, ground test, ground test” adage. I will use the Wildman ejection lighters for the marsa4, and the Q2G2’s for the raven.

I’ve gone through several more sanding / priming steps. Also managed to fit the custom nosecone to the sustainer. It’s starting to look like a real rocket! Unfortunately, it’s still cold in the Chicago area, so I’ve been forced to prime outside, then quickly bring everything back into the garage. My wife’s been pretty good about the horrible paint smell, but this won’t last long. Hopefully the weather will start to cooperate soon to get some real work done. My giant piece of allthread also showed up from Mcmaster-Carr for the nosecone. I’m going to reweigh everything and recalculate the Cp/Cd to determine how much nosecone weight I should use to work on that over the weekend.

I’ve been slowly getting back to work. This weekend I spent some time to mount the electronics into the tri-AVbay.

As you can see from the progression below, there isn’t too much to mounting the electronics. I positioned the Altimeter (in this case, a Marsa4), put mounting marks through the screw holes, drilled and tapped the mounting holes, then mounted the altimeter using #4 machine screws and plastic spacers. On the opposite side of the bay, I mounted a 9 volt battery holder, and ran the wires through the bolt cut out.

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I then drilled holes through the top and bottom of the AVBay,and ran ignition wires from the altimeter through each hole.

Once I had the ignition wires through the hole, I mounted a 4-way screw terminal through the same hole, and secured the ignition wires into one side of the screw terminal. This will allow me to mount the e-matches to the screw terminal instead of threading them through the av-bay, and having to re-seal the AV-bay after each launch. This is a method I have been successful with in the past, although I am well aware these screw terminals will be subjected to the black powder residue , and will likely have to be replaced over time.

I then went through the same process with the Raven. First, it is striking how small the raven is, when you look at it in this big AV bay. The raven is more complex to install since it uses a common + wiring scheme. While the Marsa4 had discrete connectors for everything (a + and –  for each e-match, the battery, and the power switch), the Raven only has 4 terminals and a battery + for everything. This means the power switch has to be inline, and each e-match has to be connected to the same + battery post. Not a big deal, and great if you are putting this in a minimum diameter rocket. With the amount of space in my AV bays, it’s kind of unnecessary. That said, this is my most

The third AV Bay will house a Communication Specialist tracker, and an Altus-Metrum. I haven’t decided on where to mount the power connectors yet. I will probably wait until the very end to determine their optimum placement.

I brought the booster section and AV-Bay up to bong this weekend to show my latest progress, and one of my TAP sponsors asked to see my pre-data capture form. Of course, I didn’t have it, so I’m posting it here to make it easily accessible the next time he asks

     The good news is the new pads for my sander came in (picture on left). The bad news is that means I have a LOT of sanding to do. I took advantage of the weather last week to start the lengthy process of sanding, filling, priming, and sanding again to get a nice smooth finish on the rocket. The glassing of the wings turned out a bit messy because of the limited space (about 1.5”) between the trailing edge of the wings, and the leading edge of the fins. I couldn’t find a way to properly keep enough weight on the curing fiberglass to provide the same clean surface I ended up with on the wing tops and fin can. Worse, I can’t really fit an electrical sander in that area, so I’ve had to create all sorts of sanding devices to get into that area. You can see what looks like multiple colors on the wings and fins in the picture on the left. This is indicates in some areas I have sanded through the top layer of fiberglass into the Kevlar. That’s not necessarily a good thing,

so I’m now using a different technique to smooth out rough areas, and even out all of the surfaces. I cleaned the surfaces, and sprayed a first coat of primer. The primer will even out many of the smaller pinholes and rough areas, but more importantly, it will allow me to see very quickly when I’ve sanded through into the fiberglass with the big difference in color. My first pass turned out smoother than I had anticipated, but up close, it still looks like Mickey Rourke’s face – that’s not a good thing. I have three major areas left on the rocket:

1) electrical

  I still need to install the switches, terminal blocks altimeters, GPS devices, and RF trackers  into the rocket and AV-BAY.

2) Nosecone

     The Nosecone shoulder still doesn’t fit  into the upper sustainer. That means more sanding, or, worst case, cutting the shoulder, and replacing it with a new home-made shoulder from a coupler. I also may need to add weight to the nosecone, and probably foam it. I’ll also need to make bay’s for tracking equipment, install all-thread, a bulkhead, and weight bearing anchor.

3) Sanding & Painting

     My plan is to put a really nice airbrushed paintjob on the rocket. Black base with winding flames is my current plan.  This will require a very smooth surface, which means lots of priming and sanding. I’m going to wait until the weather turns a little nicer so I can do this outside, and avoid ruining all of the surfaces and cars in nice garage. My wife hasn’t said anything yet about all of the dust, and I don’t want to push my luck.

    II will probably be taking a break for a bit on the construction side. Work travel is picking up a lot, three of my four daughters need pinewood derby cars made by mid march, and I still haven’t finished those crayon rockets I gave my kids for Christmas. With that said, I’ do plan to finish #1, #2 by next month so I can get a ‘practice’ launch in before the big event in April. Hopefully my leg will have recovered enough for some rocket hunting

     The weather was beautiful yesterday in the Chicago area – a Balmy 52 degrees! I moved the rocket to the garage, but couldn’t resist putting it together for the first time. I still have a fit problem between the nosecone and sustainer, but finally looks like a rocket. It’s supposed to be another nice day today, so I may try to get a few coats of primer on the booster section to see how much sanding and filling work I’ll really need to do – the fin and wing glassing came out much smoother than my usual work.

     Unfortunately, I tore my calf muscle about a week & a half ago skiing in Utah, which has really put a damper on rocket building and pretty much everything else. Worse, I have taken a lot of my OLD rockets out of storage  few weeks ago (a Brutus, Maximum Thrust Thunderbird, and a few other 15+ year old HPR rockets) to show my kids, and clean up for flying this weekend at Bong. Given how thick the snow is, I can’t imaging wading through it all in my leg cast trying to recover the rockets . I’ll still go up to see if either of my tap sponsors want to see my progress, but if I fly something, it will be small.

     I was able to get the wings on. First, I had to re-cut the wing slots. The lower portion was glassed over when I made the fin-can, and the whole slot itself wasn’t quite thick enough for the wings to fit through. I repeated the process on the other side, until I could dry fit both wings with a tight fit. One of the issues I will have with the wings is my limited ability to make interior fillets since both sides of the centering rings are already glued in place. First, I filled the interior of the wing’s nomex honeycomb with epoxy and put it into the slot. I let the epoxy ooze out of the honeycomb, then removed the fin. This gave me a line of epoxy on the motor tube where the wing made contact. I repeated that process a few times to build up the epoxy on the motor tube. I then  drilled a few half-holes in the wing-slots which allowed me insert a syringe into the body and add epoxy for a sloppy, but effective internal fillet on each side of the wing. Once it was dry, I was able to look through the upper center ring hole I made to pour foam to ensure a the wing was touching, and had a a fillet, and taped it up to cure. I repeated the same process on the other side until both wings were secure with internal fillets.

I used the same epoxy and process for the wings, that I used on the fins. Measure and mark the fins and sustainer, lay down tape across the markings, and fill in the middle with epoxy. The process was a little more tricky than the fins because the wing is more than twice the length. Worse, there was not enough clearance between the wing and the fin for me to use the same diameter washer I had used on the fins. Eventually, I settled on using my finger to spread, and create the fillet, dipping it in alcohol between pulls, exactly like using the washer. The result was significantly more messy, but just as effective in creating a very smooth fillet, with clean lines. This will reduce the amount of sanding I will have to do before glassing the fins.

      Once everything was dry,  I separated the booster from the upper sustainer which I was using as a lever to keep the lower sustainer in my rocket holder  to mount the sustainer upright. It’s foam time! Once again I calculated the empty volume on each wing side, mixed the proper amount (266 ML, half part A, half part B), made a quick funnel out of paper and poured in the foam. Within about 5 minutes, the foam had expanded, almost perfectly to the bottom of the pour hole. I love it when a plan actually works so well! I repeated the same process on the other side,  mixing exactly the same amount of foam, but when it was done expanding, I could barely see to top through the pour hole. Yikes! Luckily, my kids weren’t around to see the utter failure of math and science’s ability to predict an outcome. II now had no idea how much volume was left in the sustainer, so I had to do the one thing I hate to do…. guess. As you can imagine, I didn’t guess right, and you can see the results on the right – an oozing mess out of the top of the second pour hole. Luckily, this is not as bad as it looks, and I have a fair amount of experience digging foam out of tight spots thanks to a lot of lawn darts during my magnetic ejection trials. five minutes with my trusty foam extractor (a special grapefruit knife), and a little sanding, and it almost looks like I got it right the first time. I’m now going to move everything out of my office and into my garage in preparation for the massive amount of sanding I’m going to need to do. I would like to thank an anonymous reader for the tip on where to find sanding discs for my 3d sander. A kit of 100 can be had at a retailer named  Micro-Mark here. Of course, there are lots of other goodies to be found at Micro-Mark… My package arrived the other day filled with lots of tools I didn’t know I needed until I saw them in the catalog

   Spent much of the day cleaning up from the snowstorm. My four kids were school free yesterday, so I spent the day shoveling, and playing in the snow with them. I did find a little time for the rocket. The picture on the left is the original plastic nosecone. The one on the right is it’s Scotglas fiberglass replacement. Scott Broderick, a WOOSH member happened to have an “extra’ 7.5” nosecone he was willing to sell.  I was in the right place, at the right time, as this is a custom nosecone, and they can take forever if you order them. I was thinking about building my own, but a certification rocket didn’t seem like the right vehicle to be learning something so critical. The bad news is because this is a custom nosecone, it didn’t fit my upper airframe at all – the shoulder’s outer diameter is too large for the magnaframe. I was able to sneak away and do a LOT of sanding. No way I was going to do this in my office. You would be surprised at the amount of fiberglass dust even a small sanding can create. For sanding curved surfaces, I use a Crasftman 3D sander. The sander has three floating heads each with their own circular sanding pad. This lets the sander conform to most curved surfaces, reducing the possibility of creating a slat spot using a traditional sander. Unfortunately, they don’t seem to make these anymore, so the pads are becoming a little hard to find. This is an indispensable tool for me, so if someone knows of a reasonable alternative, let me know!

     This may sound strange, but one of the main reasons I was attracted to this kit was the TRIAD AV-BAY with three separate 2.5” x 8” sealed bays for electronics. Electronics are one of my favorite parts of large rockets, and this will give me the opportunity to cram a whole lot more than normal. Longer term, I plan to use the 2.5” x 8” as a standard av-bay size so that my sled-mounted electronics can be moved from rocket to rocket without requiring any custom work, or disassembly of the electronics. Here’s the parts list for the AV-bay:

• Six ‘O’ rings
• One av-bay mounting ring with three 2.5” bored holes, five 5/16” pre-drilled holes, and six brass threaded inserts (bottom)
• One av-bay mounting ring with three 2.5” bored holes, five 5/16 pre-drilled holes (top)
• Three 2.5” x 8 phenolic tubes
• Three – 1/4’ x 10.5” all-thread
• Two – 1/4” x 20 u-bolts
• Twenty six – 1/4” x 20 hex nuts
• Twenty six – 1/4” washers
• Three 1/4” eyebolts
• Three – birch av-bay pod covers, each with two small drilled holes, one 1/4” drilled hole and three partial-circular cut outs along perimeter
• Three 2.5” x 2.1” centering rings
• six 2.5” x 1/4” bulkheads with dado slots
• Three G10 boards, 2.5” x 7
• three 1/4” x 20 wing nuts
• six 8/32 x 3/4” machine screws
• six 8/32 washers

     As you can see, this was a comprehensive kit, with most of the major work already completed. Combined with the great set of directions Giant Leap provided, I assumed this would be a piece of cake. Nothing is ever as it seems Step one was to install the ubolts on each ring, then  glue in place the three phenolic tubes into the top, or bottom ring. I opted to use the Hysol glue, although I knew it would be overkill for the bay. I just wanted the two hour pot time. Getting all three tubes perfectly parallel turned out to be more difficult than I expected. After a lot of trial and error, I opted to build a small jig that would keep both rings in place, while one ring dried, laying flat on a piece of teflon coated release film which I normally use for fiberglass / carbon fiber lamination. I just inverted the tubes to glue in place the second ring, ensuring the markings on the side of the rings lined up for installation of the hardware later. This could have

gone pretty quickly, but I typically wait the full cure time between steps. In this case, I was putting down the fillets on the rear fins, then would move to do a step on the AV-bay. After both centering rings were on, I made sure they were true, and moved to putting together the top of each pod. Oops! when putting the eyebolt through the cover, and top bulkhead with the dado slot, it became obvious the eyebolts were too small. Before going out and buying new ones, I measured EVERYTHING to ensure the bulkheads or cover’s were not cut wrong. I also email Giant Leap just to be sure. A quick stop at home depot, and I was back in business.  I then threaded the eyebolts, glued the  bulkheads to the cover, and bolted them together. Once cured, I dry-fit the 3 G10 2.5” x 7” sleds into the dado slots of the bulkheads making sure there was no overhang. I then glued everything up, and left it overnight. While the glue was drying, I installed the three all-thread rods through the two centering rings. This was actually a critical component, as the all thread would be secured through the center rings I had previously installed in the upper airframe. The main parachute  kevlar shock cord would be connected to the U-bolt on the top of the av-bay, so the all thread, and center rings would be the only things connecting the main parachute to the rocket. Another great part of this hobby are the ‘cool’ tools you can buy, which could never normally be justified. In this case, my cool tool of choice was a digital toque wrench which enabled me to apply exactly the same amount of force on every bolt secured to the all-thread. In turn, the extreme recovery forces should be evenly distributed through the rods. At least, this is what I told my wife when she saw the bill for the tools….

     Once the epoxy was dried on the sleds, I glued the front facing bulkhead with the dado slot on the opposite end. A few days later, I dried fit everything, and it fit quite well. I had a few areas where epoxy had overrun, or the bulkheads were too tight, but it took less than thirty minutes to get everything fit perfect. I pulled out the sleds, then CA’s the three 2.5” x 2.1” centering rings into the top of each bay. Once complete, I installed the six o rings, inserted the sleds, and locked in the three tops of the pods with two brass screws each. That was it, I now had a finished AV-bay, with the exception of mounting the electronics. Since my electronics decisions are still in flux, that may be one of the last parts of the build.

     Once I had all three fins tacked on, it was time to make the internal, and external fillets. I decided not to use the same adhesive epoxy I had used to tack on the fins, and build the motor tube. While I really like the E-120HP, once cured, it is almost impossible to sand. I’ve used it once before on external fillets, and when I went to sand them down, I wound up taking a lot of the fiberglass around the fillet, but not the fillet itself. Instead, I opted for Pro-Set x173 / 275. Pro-Set is owned by the Vaughn Brothers, the same parent company that West Systems is. West Systems is a very popular adhesive, and laminating resin used by others in hiigh power rocketry. The two main differences between Pro-Set, and West Systems is Pro-Set comes in a cartridge system for use in a big glue gun (and, I like glue guns!), and they offer specialty resins for the aerospace industry. X173 is a black adhesive aerospace resin with some interesting properties. First, it can handle extremely high temperatures – higher than JBWeld. Second, it has an extremely high tensile strength – well over 10,000 psi. It’s hardness (Shore D) is above one hundred when used with a medium or slow hardner, yet it can be wet sanded. I didn’t say it was easy to sand, certainly not like a traditional epoxy or laminating resin, but much better than hysol.

     Since it is still difficult to shape and sand post cure, I spent a lot of time prepping for the fillet, and used a technique that generally creates baby-smooth fillets that don’t need a lot of work. I think I need to give Tim Lehr credit for process, as I think I first saw it from on a mongoose using proline epoxy, which is very similar to the x173 / 275 I am using. First, I take a washer and run it down the length of the aiframe, and fin, creating a very light scrape in the fiberglass where ithe metal’s edge touches the fin and airframe. I then measure the line, with a ruler and put down a few dashes along the line with a marker., ensuring each mark is measured accuratly. Once I have my guide lines down, I take  1/2” airbrush masking tape and lay it down exactly on the marked guidline. The tape is now at the trailing edge of the fillet I am going to make, and willl ensure an even line once the epoxy has set. I should point out I’ve now coupled the upper and lower airframe together, to give me enough weight to secure the lower airframe to a PVC rocket holder. Since this have a very high set time, I need everything to be very secure for at least a day once complete.

     You would think I would just use that awesome mixing wand to put a nice even bead down, and be done. Unfortunately, experiencee has proven I don’t have the skills to make a good fillet with a gun and wand this big. I opt to fire the epoxy into a cup, and hand mix the epoxy the traditional way. Once mixed, I take a spoon, and fill the space between the masking tape. This stuff is really hard to control. It has a very high viscosity which makes it difficult to work with, but, of course, that’s what the tape is for. I then prepare a cup of isopropyl alcohol, lots of paper towels, and a second cup to catch the excess epoxy.

I take the washer, dip it in the alcohol cup, and take small pulls of the washer to even out the epoxy, eventually pulling the excess of the end of the fin into my second cup. Once it’s even, I redip the washer in Alcohol, and take one final pull slowly, and evenly from one end of the fin to the other. The end result should be

an

extremely smooth, almost glass-like fillet. I then take a tongue depressor, and create a taper on the leading and trailing edge of the fillet. On the leading edge, this will make it easier to do tip-to-tip lamination, while in the rear, it will  even the height of the fillet (and lamination) to the boat tail which will be installed later. I repeat the same process on the second fillet. Once the external fillets are finished, I start work on the internal fillets. Frankly, the care and preperation I took on the external fillets all went out the window for the internal fillets. Nobody is going to see these, and they don’t need to be smoothed, as I don’t plan on laminating the inside. In fact, I plan on foaming the inside, so human eyes are never going to see these again. I did take some pictures, but upon review, I’m actually a little embarrassed how messy I was. Looks like my four year old had a field day in there. I wait about 90 minutes – enough time for the external fillets

to start to set, but WAY before they are really cured, to pull the masking tape away, leaving a clean fillet line on each side. The picture to the left is actually 24 hours later, after the epoxy is cured. You can see the fillet still looks wet, it’s so glass-like smooth. Once done, I repeat this process three more times, ensuring both sides of each fin have exactly the same fillets,while the inside looks like a barrel of monkeys had a poo fight. I then wait an extra day for good measure before I start foaming the in tabs.

     Foam  can be both fun, and frightening. Its really cool to watch foam set and expand, yet at the same time, if you miscalculate how much foam you need, you can have a huge mess on your hands. In my case, too little foam in the first pass, and I would find myself having to deal with three independent compartments of foam to ‘get right’ in a second pass. Too much foam, and I would risk it running over the fintabs into the boat tail section creating a big post-foam clean up process.If things really went badit could run into the slimline adapter and messing up the threads. With this in mind, I secured the slimline with masking tape, and ran a test to determine how much the foam would expand using 5ml of a, and 5ml of b. Once dried, I calculated it has expanded about 24 times. I then calculated the volume of the lower airframe section, and subtracted out the area of the motortube. I divided that volume by 24 to come up with the right amount of foam to do it in one pass. I measured part B, then mixed an equal amount of part A  in. Foam starts to expand quickly – within about 45 seconds of mixing at the temperature my office was at, so I didn’t have a lot of time to waste.  I poured the mixed foam into the aft airframe, and just watched and waited.

As you can see, it came out PEFECT. The foam finished expanding exactly where I had calculated, and started to harden at the end of the fintab, where the boat tail would glued later. This was almost too easy – something is going to go wrong down the road.

At this point, I start to pack everything up in my wife’s minivan to bring up to Bong Recreational Area in the morning to show my TAP sponsors my progress so far, and (I hoped) to launch a few rockets.

Oh yeah, since I had a little bit of the foam left on the spoon, I smeared it into a rocket on my bench that needed a pretty serious repair. Once the foam cures, I ‘ll just sand it down, and laminate a small piece of e-glass over the foam. Thiis stuff is great.

Fins… Fins… You’ve got to love fins.

In this case, I am using a material I’ve never used before. Both the fins and wings are made from “fly-lite”. This is a Giant Leap brand aerospace composite material that consists of an inner layer of nomex honycomb, sandwiched between two thin layers of fiberglass. The end result is a very strong wing, that is about half the weight of g10, or wood. With my 3 large fins, and 2 large wings, I estimate I saved about 6 pounds off of the aft end of the rocket. Frankly, weight isn’t my primary concern, but stability is. Since I had already decided to foam the aft airframe, the weight savings here should keep the total weight of the rocket neutral, reducing the amount of nosecone weight I will need for proper CG / CP. One of the issues you can clearly see wit this material is, it’s impossible to make a beveled leading edge with it. In my case I had custom MDF machined & mitered to cover all of the exposed edges. Just needed to bevel the MDF into a ‘tongue’, and use an exacto knife to build a ‘groove’ in the exposed edges. One REALLY nice things about the fly-lite material, is it is really easy to cut. In fact, I just drew around my template with a felt tip pen, and used a pair of shearing scissors to cut the line. You can’treally get any easier than that! Of course, that means the perpendicular shear strength of the material is quite low. How low? well, the formula to compute shear strength is; 

     While I don’t have the equipment to measure principal stress, I did use a piece to determine it’s ‘relative’ strength. With the MDF epoxied in, there was no amount of stress parallel to the fiberglass sheeting I could create (using a complete set of weights) that would cause the material to fail. With perpendicular force however, it failed at about half the force of a duplicate sized piece of G10. My conclusion? Kevlar and fiberglass lamination.

     With the fins cut, and the edging in place, it was now time to start epoxying the fins in place. I had already dry fit the fins and wings twice, so I was comfortable I wouldn’t have any fit issues. The only real complication was the upper fin tab would now be epoxied to the motor tube within an entirely closed portion of the airframe. I had already glued in place both center rings which would make it challenging to create inner fillets on the fin tab. My solution…. epoxy gun! for someone as messy as I, I tend to get epoxy in lot’s of places it should never be. I found glue guns (both large, and small) to be REALLY helpful when you need to get a bead of epoxy in a very specific spot. They also have ‘mixing’ chambers within the tip, which mixes the two parts of epoxy as it exits the gun. This is VERY handy, although I have found it generally doesn’t mix epoxy nearly as well as doing it by hand in a measuring cup. In this case, I put a bead of epoxy on the fin tabs, then fit them into the through-the-wall fin slot. I left the fin on for a minute or so, then pulled it back out. Looking inside the upper fin tab slot, I could clearly see the line of excess epoxy left by the fin tab. I just inserted the epoxy tip through the slot, and put down a really nice bead of the high viscosity 120HP epoxy. I then reapplied another bead of expoy on the tab root, and the exposed lower centering ring, and reinserted the fin into the slot. I then put a little pressure tape across the outside edge of the fin to keep it in place, and clamped the airframe to my desk. peeking through the wing slots, I could cleary see a great motor tube / fin tab fillet had formed. The aft fin tab was open to viewing – it looked exactly like the upper tab without the big fillet, as I planned on making those later in the project, in conjuction with the outer fin fillets. turned out the lights, to let the epoxy cure for the next 24 hours.

     Over the next four days, I repeated this procedure for all three fins. I should mention I spent a fair amount of time ensuring the fins themselves were perfectly parallel  to the airframe. While TTW slots make it much easier to get proper alignment, there is still a lot of ‘play’ through the slot. If they are not perfectly parallel, the rocket will tend to spin in flight. Not a big deal for a spectator, but I planned on adding video equipment in the rocket. There is nothing worse than watching a spinning rocket video – gives me a headache, and you really can’t see anything. Here’s a good example

  I  spent much of the time in between the fin epoxy curing building the AV-bay, which will be the subject of the next post. It’s one cool AV-bay.

I have a few habits when it comes to building kits….

The first habit is I  ALWAYS read through all of the documentation before starting a build. I’ve learned the hard way that not all directions are accurate, and how something looks in one section, may be very different in a follow on section.

For this particular rocket, Giant Leap provided over 50 pages of documentation! On the one hand, that’s a lot of documentation. On the other, the modifications I was planning on making were sufficient that a fair amount of information I would have to disregard, or modify. And, of course, there are certain things I do in a build that will probably be different than the instructions, just because I’ve used certain techniques successfully in previous builds.

Once I read through the documentation, the first order of business was to build the motor mount. Starting off , I thought I would do something SUPER easy –  – JBweld slimline motor retainer to the motor tube. This consists of sanding the outer diameter of the end of the motor tube to create a rough surface, prep the inside of the slimline with some masking tape to ensure the threads don’t get epoxy on them, coat the slimline and end of the tube, and push them together. Cool. First step was simple.

Oops! One of the modifications I was doing to the kit was to streamline the fins. This meant that the aft end of the fin tab would be a few inches shorter than the stock build. Since the fin tab would be farther down the motor tube, another modification I had planned was extending the boattail to ensure it would buttress the end of the fin tabs.  Once I extended the boat tail, I realized the (now glued in place) slimline would not fit through the now elongated boattail! The end of the slimline adapter has a small tab that’s meant to go behind the aft centering ring in a traditional build. So, as you can see on the left, the slimline adapter was now “stuck” about 2 inches shy of the end of the boattail. Obviously, this won’t work (unless I want the boattail to catch on fire….). Luckily, the metal tab was no match for a grinder I sure am glad I caught this – If I had installed the motor tube and center rings into the rocket airframe, grinding down that tab would have been almost impossible.

The next part was fairly easy – install the rear, and forward centering rings. Since the fins are very long, they had to be cut to ensure they would fit around the rear center ring. This meant the rear center ring placement was CRUCIAL to ensure everything fit together. a few minutes of measuring, I had determined the exact position necessary for both center rings. The motor tube is made by Giant Leap, and is a hybrid phenolic tubing called “Magna Frame” The exterior of the tube was extremely slick, which makes for a difficult mechanical bond when epoxying two different types of materials together. I sanded down the tube in  both positions I had determined for the centering rings . Now it was time to make the upper center ring.

The upper center ring will be one of the critical components of the rocket, and will take a lot of the stress associated with both thrust, and  the initial shock of parachute deployment. I opted to double the width of the centering ring, and install not one, but two u-bolts to attach the recovery harness. Once I epoxy the upper centering ring in place, I will never be able to touch the u-bolts again without ruining a big part of the rocket.  I then connected a purpose-built harness to both u-bolts, which should distribute the recovery shock better between each ubolt. I also drilled two large holes in the centering ring, in preparation for adding foam later in the build  process.  Finally, I added some CA on both the upper, and lower nuts on the u-bolts to ensure they would not come loose during the extreme launch this rocket is likely to make.

Yes, I am well aware my office is a MESS. Thank you for noticing, but don’t tell my wife!

Once the epoxy on the center rings had cured (24 hours – I have a lot of computer equipment in my office, so I can easily keep it about 90 degrees). I dry fit it into the airframe to ensure the center rings were in the right positions to allow for installation of the fins. I had dry fit it once already, but that was before I glued the center rings – this was just a final check before I epoxied the motor tube and centering rings into the airframe. For good measure, I also installed the boattail, ensuring  the slimline would go through the length, and the end of the boattail would buttress the fin tabs.

It’s always a little nerve racking when you build the fins MONTHS before commencing the build, wondering if it’s all going to fit together. After a little sanding, everything fit PERFECT.  What’s fun about dry fitting the components  together is it looks like a rocket! This is highly motivating to see what it’s going to look like a few weeks (or months…), and several steps later.  I then dissembled everything, being very carful not to let the motor tube shift in any way. I then drew circles around the outer diameter of the centering rings, and removed the motor tube from the airframe. This allowed me to see exactly where the centering rings were going to go so I could sand internally to create a rough surface, and apply epoxy just to the areas in which the centering rings would be mounted. I reinstalled the motor tube, and set everything to the side to dry (another 24 hours… tick tick tick)

I  have had the rocksimfile for the rocket for quite a while, and made a few modifications

1) a few cosmetic changes to wings and fins to make them look ‘sleaker’
2) remove mid centering ring, drill holes in forward centering ring,
and fill booster section with Mega Foam prior to installing the tube
coupler / baffle plate subassembly.
3) Drill numerous 1/2 inch holes in the foward fin/wing root tabs to
allow foam to flow through
4) fill tail with mega foam to encapsulate rear fin root tabs prior to
installing tailcone
5) Replace included Polystyrene nosecone with a custom fiberglass 5:1
Ogive nosecone. This will increase the overall height by about 12″,
increase the nosecone weight (both reflected in the Rocksim file), and
allow me more flexibility in adding nosecone weight as I get closer to
final build and have actual weights for the booster and sustainer
sections.
6) Tip to tip lamination of both fins and wings using kevlar and
fiberglass. My usual procedure is fiberglass and Carbon Fiber with a
vacuum bag. Thanks to the lower maximum expected speed of this rocket I
don’t need the stiffness of Carbon fiber,which free’s me from using a
vacuum bag process.  I’m very comfortable with the lamination process,
but I have not yet finalized how I am going to accomplish this given
the wing / fin overlap. My initial thought is to mount the fins first,
then laminate the fins. re-cut the airframe wing slots, mount the
wings, then laminate the wings.

Here is a copy of the Rocksim file:

For recovery I will be abandoning my electromagnetic ejection
concepts. I am still working on them, but starting at MWP 8, I’ve had
a series of failures where the force of ejection was significantly
stronger than I had calculated, and ripped the electronics or magnets
out of the rocket. I think the high voltages are effecting the
electronics, but I’m still unsure.
I plan on using my Marsa4 altimeter for primary, and my Raven for
backup. Both altimeters have been flown several times, and have been
flawless in their operation. I received an Altus Metrum for the
Holidays, which I will add in the third AV bay. Since I have no
flights, nor any experience with it,  I don’t plan on utilizing it for
any part of recovery – Just a way to get some telemetry data, and test
out it’s transmitting recording capabilities. I already love this little guy because the hardware is ‘open hardware’, and the operating system, and flight software is open source! available here

My primary building epoxy is be Loctite Hysol E-120HP

. This is an Aerospace grade high viscosity epoxy that is just amazing.
Provides a long  pot life (~2 hours), and creates bonds stronger than the materials it’s connected to. It’s expensive, but worth it. I use JB Weld in areas that will be subjected to high temperatures (connecting the motor retainer), and US Composites for lamination. I *MAY* use Pro-Set for fin and wing fillets. I haven’t decided yet.

     Welcome to my Triipoli Rocket Association Level 3 certification  Rocket blog! I plan to use this as a way to organize the photo’s and interrogatory around the build.

     Obtaining my Level 3 certification will allow me to fly larger projects with larger M and above motors. Level 3 is not to be taken lightly. This is a formal process that must be successfully completed. The entire rocket project must be thoroughly documented. This requires developing schematic documentation for every rocket component that demonstrates construction techniques, adhesives, materials, laminations, electronics, wiring, and detailed checklists. The whole process must then be approved by two members of the Tripoli Technical Advisory Committee (TAP) with at least one TAP member completing a successful final inspection of the entire rocket project. Once all the paper work and approvals are completed, the level 3 rocket can be flown. Only when the rocket is successfully launched, recovered, and all final TAP signatures obtained, is the level 3 process completed.

     Why is this a big deal? The short answer: If not done correctly, it could be very dangerous. A level 3 rocketeer can launch rockets using motors that are over FOUR THOUSAND times more powerful than the typical Este’s motor you can buy in a hobby store.

     Why on earth would I want to do something like this? The short answer – FUN. This particular hobby combines 8  things that really appeal to me:

1) Computer modeling. Except for the small rockets I build with my kids, every rocket I’ve built will start with a computer simulation. My primary application of choice  is called “Rocksim’ which allows me virtually build the rocket with all of the likely materials I’m going to use, and test it’s flight and operational characteristics before ever picking up a hammer.

2) Advanced building techniques. I can run a drill press as well the next guy  but when you combine these skills with things like at-home carbon fiber vacuum lamination processes, precision alignment requirements,  and advanced epoxy techniques, it starts to really get interesting. In

3) Purpose built computers and custom software. You can’t launch a rocket to 20,000 ft and hope everything works out. I rely on advanced avionics, many home built to control the key stages of a flight and recovery. Altimeters, barrometric sensors, accelerometers, GPS units, telemetery transmitters, HAM transmitters  and onboard video systems all add to the ‘fun’ of a successful launch

4) You can be an individual contributor. The sport is small, and still fairly young. This allows one to be a meaningful individual contributor to further the knowledge and capabilities of the hobby. For example, I’ve been working on an electromagnetic ejection system to remove the need to use black powder, and a small explosion within my rocket to release a recovery device.  At least once a month I run across some new novel idea from a fellow rocketeer on a better / different way to accomplish something

5) Allows for a lot of creative expression. I’ve built rockets that look like bats, flying saucers, space planes, I’ve even launched a Christmas tree. I get to decide how the rocket is painted, and name it (My level 3 rocket is named “Questionable Investment”)

6) Fellow rocketeers. I’m a geek. I know I am a geek. This sport tends to attract like minded geeks, and quite a few interesting personalities. I was laughing so hard at Tim’s Lehr’s “commentary” about my rockets at MWP 8 that most of the video I shot is unusable because I’m laughing too hard to keep the camera straight. Better, all four of my daughters LOVE rockets too – it’s something we can all do together that doesn’t require me to dress up, or have tea with dolls.

7) This is the only hobby I know where the failures are as interesting to watch as the successes. In fact, like car racing, some come to watch, hoping for the failures.

8) LDRS – That’s the name of Tripoli’s big annual rocket launch. Stands for “Large Dangerous Rocket Ships”. Need I say more?

On to the first photo’s!

These are the boxes containing the Giant Leap Nuclear Sledgehammer which will be the basis of my level 3 rocket. A couple of interesting things to note. First, my wife has actually let me take over an entire bay of our garage to turn into a mad scientist laboratory – if you knew my wife, you would know that this is really proof of her love.

Here are the parts “unboxed”. First, note how organized Giant Leap ships their components. I’ was really impressed. Each piece had a separate heat-sealed bag.  Just note – this is the LAST time you will see these components this organized