Now that we have your attention, lets get into the build of this beast.

Fins:

It may seem odd to start a build of this magnitude with the fins, but we had doubts about making fins that were both strong enough and light enough to make this project a reality. We discussed a few ideas, all of which involved a large amount of expense and an even larger amount of work. So rather than make our lives harder than they needed to be we decided that the Home Depot method was our best bet for a first shot.

We figured that the fins should have a final thickness of about 1" for structural and aesthetic purposes. This gave us a starting point for our design, so off to the hardware to browse and buy things we didn't even know we needed. After some testing we came up with a design employing plywood, foam, door skins, pocket screws and a lot of wood glue. The central portion of the fin was built with 3/4" AB plywood and pink insulation foam, and the skins were 1/8" door skin. The frame was built using pocket screws, which give and AMAZING amount of strength, giving a lightweight but very rigid structure.

The frame includes the fin tab which was made solid to give the maximum amount of strength since the fins are designed to be removable. From this point pink insulation foam was cut to fit into the two triangular shapes then hot-wire cut down to the thickness of the frame.

The two skins of the fins were cut to rough shape with a jigsaw and slathered with a thin layer of wood glue and placed on either side of the frame. The whole assemble was then placed into what we like to call the "red-neck press" which consisted of two long flat pieces of plywood we had lying around the shop along with everything heavy we could find including 5 buckets of water, a sanding station and a chop saw. It was left in the press for a couple of days to insure that all of the glue was completely cured. We then used a flushcut bit and router to trim the skins down. When all was said and done each fin weighs about 15 lbs.

Motor Mount:

After the shot of confidence from the fins we felt slightly more sane, but then we started working on the motor mount and that feeling went back out the window. The motor mount is extremely important on this project. That can be said about any rocket, but with the Gemini DC everything happens around the motor mount including parachute deployment. We decided to use a superstructure in this rocket, starting at the base and continuing to just short of the nose. In the motor mount this superstructure consists of 4 fin boxes and 4 stringers. In the upper sections it will consist of 8 stringers. The stringers and fin boxes lock into the centering rings and help to distribute all of the forces throughout the rocket, or at least we hope so.

Our first challenge with the motor mount was equally spacing 8 items around a circular shape. In order to do this we decided to make octagons first then cut the octagons down to rings after positioning the slots and fin boxes. We started by making an octagon pattern and cutting out the slots for the fin boxes. Using a the trusty flushcut and router we used this pattern to make the 5 octagons which would become the motor mount. The slots for the stringers were cut on the table saw and the motor mount holes were again cut using a pattern and router. Finally the octagons were rounded using a router table with a circle cutting jig.

With the rings completed we were able to start to assemble the motor mount. The fin boxes were constructed using tongue and groove construction in order to maximize the strength and the stringers were slotted to mate with the slots in each ring. The motor mount was assembled using a section of extruded aluminum rail in order to insure that there was no twist during glue up.

The bottom plate of the motor mount is made of 3/4" 9 ply birch in an attempt to avoid the motors punching through the rocket. Above the motor mount there is another 1.5" of rings which hold the parachute attachment rod. The stack has a solid ring on bottom, and two upper rings which were webbed out to reduce weight. This is a similar design to how we will construct the superstructure in the upper sections.

With the motor mount done we were finally able to do some major mock-up. There is very little about this project that is small so when you put it all together it is truly a sight to see. The 10" tube represents the main nose cone, it is approximately the correct length. You can see the original kit in the foreground of the first picture and inside the motor mount in the second picture. (First picture: Jay on left, Jacob on right) We have Polecat Aerospace to thank for the side tube nosecones, there is no way we could have made them as light as they did.

Support Structure:

We have some major concerns about the14 feet of unsupported tube above the motor mount, but we have come up with a solution which we believe will give the tube enough strength to avoid buckling under thrust. The idea involves what we are calling a super-structure which will transfer the forces from the motor mount up to within 3 feet of the nose cone shoulder. This should result in a very stiff tube which will be unlikely to buckle at liftoff. The super-structure consists of two 6 foot sections of a skeleton structure. They are both made up of 5 3/8" plywood rings and 8 poplar stringers (3/4" x 3/4"). This echoes the design of the motor mount which used 4 fin boxes and 4 stringers to achieve the same goal. The stringers are slotted as well as the rings to give a half lap joint which ensures the superstructure is square when assembled.

The rings were webbed out similar to the top rings of the retention plate above, with a smaller inner web width. This allows the section to be significantly reduced in weight. The section were assembled using wood glue and bungee's, and allowed to dry. Final weight of each section 8.25 lbs, not too shabby when you take into account the strength it will provide. The plan is to bolt the two super-structure sections together in the center, then bolt them to the top of the motor mount, giving a solid structure from base to around 19 feet.

Motor Mount Revisit:

We glued up the motor mount and everything went pretty well. We were only able to attach the rail to 4 of the 5 rings and this turned out to be a little bit of an issue. We ended up with some twist in the final section which causes the fins to bind a small amount. The top section twists by about 1/16" at the top, so it is not much to fix but definitely needs to be fixed. We have a couple methods we are experimenting with to fix the twist, and we will add the solution here when it is resolved.

As usual once we had some major parts put together we couldn't resist setting it up to admire the project. This is going to be, to say the least, a sight to see.

Now for the money shot. I took the liberty of adding a representation of the final size, though keep in mind that this is still not correct size, I couldn't enlarge the kit picture any more and still fit it in the real picture. The final size is still probably a couple feet taller than this would suggest. You can see the motor mount on bottom, and both super-structure sections stack up as they will be in the rocket.

Ejection System:

The biggest issue that we face on this project is without a doubt the rear ejection. As we know from our good friend Newton objects at rest stay at rest, and this has an important consequence when applied to the Gemini DC. The parachutes in the original kit are simply stuffed into the side tubes and friction holds them in place. This is simple and effective, but unfortunately this only works on a small scale. As rockets get bigger parachutes get heavier, and Newton enters the picture in a big way. Without a method of retention for the parachutes we would have a flight trajectory similar to a top fuel dragster with a stuck throttle, as our parachutes would be deployed at liftoff. We had a method of overcoming this issue on our 2x, 3x, 4x, and 8x Gemini DC's (yeah we kind of like the kit) but this method involved ejecting the motor mount at apogee. The 8x was pushing the boundary of safety with this method, so it was not a good method for the 14x. We needed a new method to keep the parachutes with the rocket until apogee, that would also allow us to keep our very large and very expensive motor mount in the rocket. The answer came from, Ken Sparks, one of our team mates from Arizona Rocketry Team. The idea is simple, use side deployment rather than rear deployment, but put it so low on the side tube that in actuality the parachutes do come out the rear. This idea uses a cap which is inserted from the side and retained on the bottom with a plywood half-ring. This gives the cap a surface to push against during boost keeping the parachutes in the side tube. The cap itself is hollow inside and has an internal couple piece which is used as a shear pin attachment point. The cap will be deployed to the side and will have a small drogue parachute inside of it. This drogue will be attached to the main parachutes and is the primary method of deployment. We built a model of the system, which is not exactly the same as the final system, but close enough to get the idea.

We also have some Solidworks models created by Jacob, to show the idea prior to the actual model being built.

Nose Cone:

This was one of the largest parts of this project as well as the part which required the most amount of technique. The nose cone was formed out of a massive block of Expanded Poly-Styrene Foam. A 1 inch wooden closet pole was inserted through the length of the foam block. This pole would act as the pivot in our make-shift lathe. The lathe consisted of two endplates which mated with the closet pole, and two sides which were cut out in the shape of the final nose cone. Once the lathe was built and the guide surfaces were sanded smooth, a hot wire was used to cut the foam block to rough shape. We were lucky enough to get some help from Roy, one of our fellow Arizona Rocketry Team members, with the nose cone. After the foam was hot-wired a router was mounted on a sled which followed the guides to cut the nose cone to final shape. The router was turned on and roy slowly moved it along the length of the nose cone while Jay spun the cone with a drill. The final step was to do some sanding, and we ended up with a very nice foam nose cone.

Now that we had a nicely shaped foam nose cone the next step was to make it strong. We use an 8.9 ounce 8-harness satin weave fiberglass on all of our nose cones. This glass conforms to a compound shape very well and makes it possible to cover a nose cone with 1 wrap most of the time. With the help of Ken Sparks and Guy Smith, other ART members, we were able to get two layers of glass on the nose cone during a morning build session. The end result is a very strong nose cone. The should is being fabricated out of a split piece of concrete form tube mounted directly to the closet pole.

Motor Mount Revisit ... Again:

Well the twist in the motor mount was fixed without much problem. The piece of 15-15 extruded aluminum rail was reattached to the motor mount and two plates of 1/4 inch plywood were placed between the upper centering rings bringing it right back to perfect. Ken was kind enough to bring us his motor cases so we could check for any binds in the motor tubes, everything looked good so we went ahead and epoxied the tubes, followed by expanding foam to solidify the bond. We also had a chance to put the holes in the top and bottom of the fin boxes for the fin retention, more to come on that later. The most exotic piece of this rocket thus far is the Aluminum motor retention plate. Ken helped us get this plate cut out and it looks like it will work perfectly, just allowing the motor nozzles to pass though and retaining the cases.

The 12 holes are match up with T-nuts in the thrust plate for positive retention of the motors. More to come soon, but the project is really starting to come together. We have some sponsors which are coming on board that will help to make this project even better, more to come on them soon as well.

To continue the saga of the motor mount, we have epoxied it into the lower body tube. It was a challenge due to the size of the pieces we were working with but it appears to have worked out well. The motor mount was recessed a half inch to allow the retention plate to be flush with the base of the tube when installed. The retention plate has also had some half inch spacer tubes added to all of the attachment points to keep it even when mounted. After the epoxy dried we used a router and a flush cut bit to slot the tube using the inside of the fin boxes as a guide. After the router had done its job a light sanding, followed by epoxy along the length of the box finished the job.

While we are at it here is a picture of the nose cone attached to the shoulder as well.

Piston Ejection:

As we said before, we try to take things that are challenging on the low power scale and we try to apply them to high power. One of the more irritating methods of parachute deployment is the piston method. So, as any sane rocket person would expect, we decided we needed to use them in this project. Now we do have some good reasons for employing the dreaded piston.

Our first reason is the volume of the bay we would be trying to pressurize if we did not use the piston, 10" tube 6 feet long, it is a lot of empty space. The next reason is that we will have 4 of Susan's beautiful parachutes, which she slaved over for hours upon hours, in the side tubes of this project. The last thing we want to do is put even the smallest black spot on them. We would have to deal with her all the way home from Vegas if we did, and who knows how long after that. Since there are not enough nickel slots in the world to make up for us hurting her parachutes we decided the piston was the way to go.

Now these are certainly not you average size piston. Each one is 36" long and 10" in diameter, with a 3/8" steel rod running down the center. The rod is our attachment point along with a 3/8" eye-nut on either end. The main structure of the piston is made of white insulation foam. This is another idea we have to give Ken Sparks credit for, he has used foam on more rockets than anyone else I know. How many other people do you know of that have made a 14 foot tall foam Estes Fat Boy. The foam was built up in layers on top of and below the 3/8" rod and glued to the two 1/4" plywood endplates. A hot wire cutter was used to trim the foam to match the profile on the endplates. A little sanding later and you have a perfect cylinder. A layer of 6oz fiberglass was then layed up over the foam to keep it from burning as this foam has a tendency to do, Saturn V RIP.

The project is really beginning to come together. We will be looking at paint and decals soon, and are hoping to get our electronics figured out within a week or two. The project is looking to be a definite go for LDRS.

Piston Ejection Revisit:

Well piston ejection was a good idea that ended up being a big bust. We spent about 6 hours one Saturday trying to get one of the pistons to slide in the tube smoothly, and were unsuccessful. Our sanding techniques did get to be very inventive though. We used one of the pistons with sandpaper on it and a rope tied to both ends. We pulled the piston through the tube, turned it and pulled it back the other way. This led to a lot of sore arms, hands and backs and very little progress. Next we used a piece of 8"tube with sandpaper taped to it and lead weights inside. We pushed and pulled the tube and went around the side tube. This made a little more progress, but still was mostly useless. Our last sanding method was a custom 6" drum sander with a 4 foot reach. We put it in the chuck of a drill and went up and down the tube. This worked well, but as we found out it was all in vain, even sanding the piston down. We discovered at the end of the day that the tube was not perfectly round anymore, which accounted for the tight fit, but presented a problem with no clear solution. We could apply a little pressure and the piston would slide perfectly. We decided we could not ensure that the pistons would slide without binding, and if the pistons bound we were in big trouble on flight.

So plan B . . . what was plan B again? This was the first time in the project we didn't think we were going to get this thing done. We had been planning to use a piston for a month at this point and had never even thought about it not working as expected. So we decided we had to go back to our basic proven method of deployment. We take a space just big enough to fit our parachutes, put 4 rather large ejection charges, for redundancy, on the bottom and blow the laundry out. This involved us moving our charges a good distance down the side tubes. We already needed a coupler in the tube to make the side ejection caps work as designed, so we split the coupler at the location the charge plate needed to go and sandwiched it between the two pieces of coupler. We also put a door in the side tube to allow the insertion of the removable charge holders and also to give us a nice place for two of our Guy Smith on-board cameras. Now I know many web sites and build pages have a lot of expressive pictures showing the mood and temperament of the builders, but we being two lonely rocketeers couldn't get the camera out to capture our disappointment. So just imagine both of us looking very dejected and sad once we hit the piston wall. Needless to say we still hate pistons, but we are confident in this new method.

The Pictures above also show the parachute attachment point which connects directly to our original attachment point at the top of the motor mount. The connection point is attached to a 90 degree angle bracket and about 4 feet of 1/2" threaded rod. The PVC parts are the charge holders.

The above picture shows the entire parachute attachment affair. Everything is bolted with lock-washers so we should not have any issue even if we have a glue joint failure at some point.

Side Tube Connection:

Well I think I managed to skip ahead somewhat. If you couldn't tell there are side tubes attached to the main tube in the pictures above. Well just think of this as one of those movies that has flashbacks. So...FLASHBACK. The side tubes were attached to the main body tube with a large cradle. The cradle was made by cutting 3 circles out of a piece of OSB to match the final tube layout of the rocket. The piece was then cut in half and viola we had a cradle. We aligned the tubes, inserted the 1/2" threaded rod, since it would be impossible after gluing on the side tubes, and got ready to glue. We used epoxy and cab-o-sil to make the initial attachment, and then poured in epoxy fillets after it was dry. In order to give us a stronger joint and to give us a nice look we glued a 7 foot long quarter piece of 6" tube. This gave us a secondary glue joint at a good distance from the initial glue joint, resulting in a very strong joint. Alright after the pictures below imagine a bright white flash and come back to the future.

Fins Revisit:

Well we got the other son involved in the project this past weekend. John was standing around looking bored, so we gave him a job none of us were very excited to do. We let him grind the end plates of the fin tabs. These end plates are on an angle which allows a simple bolt from above and bolt from below to lock the fins into the boxes. The plates are 1/8" steel bar stock. They were binding in the fin boxes, so John got to grind the bottom of the plates. He was thrilled...totally.

Ejection System Revisit:

We have started to apply the method we tester previously on the actual rocket and it is looking pretty good. The side tube caps otherwise known as "pizza boxes," what can I say we were hungry, they look somewhat like pizzas, and they are boxes...kinda. So we cut the doors off the body, made the coupler that goes inside the door, and put the whole affair together. We also installed the lip under the pizza box that keeps it from falling away during launch. We have a small issue with the boxes being able to rotate out, but we think we have a way to fix the issue. The caps look just like they do above so here is a picture of the lip.

Mock-Up, This time it's AWESOME:

Well we go the thing together, not vertically, but horizontally. It is huge. I'm not quite sure how on earth we will get this thing in the air, but we will figure that out later. In one picture you can see the original kit sitting on the nose cone.

Great New Sponsors:

We have some great news on the sponsorship front. We already have the amazing support of Polecat Aerospace for the side tube nose cones, and What's Up Hobbies is helping us out with some of the major components that make the flight possible. Both companies have been invaluable to us in this project and many times before this. I am sure we will be talking to them after this project as well. Great people, with amazing products and top notch customer service make us glad to have the support of these two sponsors.

We are pleased to announce the addition of Perfectflite and Missileworks as our two newest sponsors. Both of these companies have always performed to highest standard when it comes to both quality and customer service. We try to stress to anyone new to the hobby that it is cheap insurance to always fly a couple of different manufacturers electronics in your big projects. There is always the possibility that some never before seen anomaly could occur which could cause an altimeter or timer to fail. With 300-350 lbs of rocket in the air we feel it would be irresponsible not to do everything within our power eliminate every possible failure point. We have 100% faith in the products produced by both of these manufacturers and are very happy to be able to welcome them to the project.

Glassing the Fins:

The edges of the fins have been chipping ever since we first made them long long ago. To fix this we rounded them over with a router and glassed them. We used 6" fiberglass tape on both the leading and trailing edge of the fins. This should give them a bit more strength and also makes them a lot more durable.

Superstructure Attachment:

The superstructure is our way to keep the rocket in one piece during flight. All loads are transmitted through the motor mount and into the superstructure. This spreads the load out and keeps one point from being a single point of failure. We had an interesting problem with attaching the superstructure, we needed to bolt something down 2 feet into our main body tube. Our arms would reach that, but it would make our lives harder to have to reach that far. In order to avoid this we put rods through the first two rings. These rods can not come back far enough for the washer to fall off, but also can only go forward enough to engage in the T-Nuts we put in the upper plate of the motor mount. These rods can then be tightened from the top of the rods rather than 2 feet down in the tube.

The upper attachment point is far simpler. Since it is in open air when it is attached we will just use nuts and bolts. On launch day the tubes will be screwed into the stringers on the superstructure and the whole system will be complete.

Retention Plate Complete:

We completed the plate that will serve as motor retention for all 5 motors. The mounting hardware may be a little overkill, but it is just how we do things. If 4 bolts will work, 12 should really work!

Electronics Bay:

With the electronics beginning to come in from our great sponsors Missileworks and Perfectflite we are able to get started on the electronics bay. We will be using a single centralized bay. Since we have our superstructure running the length of the rocket the bay was somewhat predetermined. We decided to build a box between opposing stringers. This box would give us a 17" by 12" sled that we could mount electronics to. The location in the superstructure puts the bay about 12 feet off the ground, which still will be accessible with a ladder. The bay will hold a total of 6 Altimeters, 6 Timers, and 1 WRC from Missileworks. The door will be cut out of the tube once we know the exact location of the bay in the tube.

More to come this weekend, so stay tuned.

Our Little Supercomputer:

Having received all of our electronics from our wonderful sponsors Perfectflite and Missileworks we decided to get started on the electrical system. First a rundown of the offensive line.

As you can see this is going to be a complicated electrical system. For that reason there is a great deal of planning that is going into this system. Every piece of electronics is necessary to make everything work correctly. Every piece of electronics is also run in parallel with a redundant system to ensure safety. We could try to explain the layout of the electronics onto the sled, but it is far easier to simply let the pictures tell the tale.

I know all of our fans have been wondering who Jacob is, well now you know. I am the webmaster and photographer so for that reason I don't make it into pictures very often. Fortunately though I also am most farmiliar with the electronics used in the project, so there I am in all of my glory. Sorry ladies ... I am taken, by the web site editor, Sophie. Any challenges for my hand can be taken up with her ... not all at once though.

The electronics are now fully assembled on the board, but we did not get a fully assembled picture. Jay even got a chance to put his electrical engineering degree to use when he checked over the board. We used what may be a record number of terminal strips on the board. Something on the order of 100 connections had to be made, but it is all done and it should make our lives easier on launch day.

Basic Flight Events:

Ignition: At launch two break wires in parallel will be broken by the rocket beginning to move. The break wires will be put in parallel to add a level of safety. We do not want an accidental activation due to one break wire being broken. By putting the break wires in parallel both must be broken to activate the timers. These break wires activate two of the PerfectFlite MiniTimers. These times will be set to 0.5 seconds after which they will ignite the second set of igniters, lighting the motors if the initial igniter fails.

Apogee: At apogee two PerfectFlite MAWDs and two Missileworks RRC2s eject the pizza boxes off of the side tubes. These are redundant systems to ensure safety. The pizza boxes pull out 10 foot pilot chutes which in turn pull out the two 20 foot parachutes in each side tube. If the pilot chutes do not do their job then we have an ejection charge backup. When the pizza boxes eject they will break a set of break wires wired in series. This allows for either break wire to activate the two PerfectFlite MiniTimers attached to either side tube. These timers will be set to 0.5 seconds and will ignite ejection charges in the side tubes.

1500 Feet: In theory, at 1500 feet the main nose cone will eject bringing out two more 20 foot parachutes as well as a pair of 10 foot parachutes for the nose cone. These will be ejected by one PerfectFlite MAWD and one Missileworks RRC2. We say in theory because we don't know that any amount of tape or any number of shear pins will hold the nose cone on at apogee. In the event the nose comes off at apogee, the rocket simply has a longer ride down. We would rather the parachutes all come out at the wrong time than not come out at all.

At Any Time: If we at any point get scared, or feel that events are happening too late for our liking, we have the option of pressing a button and ejecting all of the parachutes. This is thanks to our MissileWorks WRC system. We will have one channel set up to blow the pizza boxes and the second channel set to blow both the nose and side tube parachute charges. This unit gives us the safest rocket we could possibly have without just leaving it on the pad forever.

Fins, Now With New and Improved Finish:

Jay filled the fins with the magic epoxy and Q-cells mixture. Q-cells are sold by US-Composites, and are a very nice type of micro balloons. The fins were sanded and are now going into paint. Jay and John spent part of the weekend sanding, by the end of the day they were hot, tired, and a little itchy.

We are nearing the end. Jay is painting and getting decals finalized. Jacob is traveling, leaving Jay to do the dirty work. Things are looking good to be done and ready for LDRS.

Flight Report:

The 14x GeminiDC took to the skies above Jean, Nv mid morning on Saturday July 14th. The beast was powered by just under 2000 lbs of thrust off of the pad, and a full O worth of total impulse. Motors were as planned, 1 Aerotech M1939 and 4 Aerotech M1315s, all motors were lit on the ground thanks to some Larry Foster made igniters which we are convinced can light dirt. At half a second into flight two PerfectFlight Minitimers ignited our backup motor igniters though they were not necessary to get the motors lit. Guidance for the 350+ lb rocket was provided by Ken Spark's always perfect launch tower. The flight went perfectly with a slight roll to apogee at a majestic 3000 ft. At Apogee the PerfectFlight and Missileworks altimeters, one of each per side tube, blew the pizza boxes away from the rocket deploying the first two of 11 Susan Dennis parachutes. The ejection of the pizza boxes started the 4 other PerfectFlite Minitimers with delays set to 2 and 4 seconds, one of each time delay in each side tube. These timers initiated ejection charges to help push two 20 foot parachutes out of each side tube. The first parachute to inflate shredded as the rocket had picked up speed since the drogue chute deployment at apogee. The second chute lost one shroud line and therefore did not inflate properly either. The other side tube had perfect inflation of both of it's 20 foot parachutes and the rocket continued under control toward earth. At around 1200 feet the PerfectFlite MAWD and Missileworks RRC2 altimeters deployed the nose cone bringing out two more 20 foot parachutes for the body as well as a 16 foot and two 10 foot parachutes for the nose cone. With all of the laundry safely both channels of the MissileWorks WRC system were fired and worked perfectly. All pieces drifted safely back to earth and landed about 1000 ft from the launch pad.

Flight Video on You Tube

All parachutes were recovered, and the rocket is in relatively good shape. We sustained some fin damage as a result of losing two parachutes, as well as some ejection charge damage with the pizza poxes. All in all the flight was a complete success. We could not have done it without the support of many friends and family. We are still gathering the names of all those that helped us at the pad and during the building stages of this project. We will be updating with a more complete flight report on the LDRS 26 page as soon as we have a chance. The 14x Gemini DC was by far the most ambitious and challenging project we have ever faced, and it certainly begs the question, what's next? We have a few ideas up our sleeves, so don't worry we will be back and you won't want to miss it. Who knows, you may even see the 14x Gemini DC take to the skies again.

Finally I would like to implore anyone reading this to keep Polecat Aerospace, What's Up Hobbies, Perfectflite and Missileworks in mind when searching for rocketry related items of any type. These companies and vendors helped to make this build a reality.

Keep your eyes out for the 28 foot Estes Comanche 3 that we will be helping the Arizona Rocketry Team build for a planned launch at Plaster Blaster 2007.