HPR Nuke Pro Maxx

[MasonH]

Ok, so my friend and I have ordered a Nuke Pro Maxx, a stiffy tube coupler, an Aeropac Retainer, and a 2.14 bulkhead. Our goal is to make a DD capable NMP rocket that can reach supersonic speeds and over a mile high on nothing larger than an I motor. The parts were ordered from apogee today and should be here Saturday or Monday, so all I have left to buy are rail buttons, nomex, and a shock cord. The first two I can get locally, but the chord I will order from Top Flite. Chances are that if this build goes well, I will buy the same kit and do the same project for myself instead of with a group, just because I love the kit so much.

[EeebeeE]

Follow my threads on the same rocket. According to Open Rocket, my DD Nuke Pro Maxx will achieve Mach 1.2 with a CTI I470. I offset my body tube segment on my Av Bay by a half inch, then extended the motor tube 5/8" from the end of the rocket, and the result is that I can fly this thing on a CTI 6XL case. A J530 will put this thing up to 10,000 feet at a peak of Mach 1.7.

Providing of course that I do not shred. Attached is my Open Rocket design.

[MasonH]

Rocksim says close to 10200' on the same motor, and Mach 1.92 on a J825(?). Either way, I will not be pounding this with a J for years since I am only 15, almost 16. I hope to get this thing to fly by the end of summer. Do you have a link to the build thread?

[grouch]

Mine had a set back yesterday. I wasn't in the right state of mind when I tried to make a sled for my altimeter. It didn't come out as good as I wanted so it is back to the drawing board. I still think I am only a couple of weeks until it will be done though. As long as mine in done before the next CATO for a rundown flight I should be ready to spank it at NERRF. The rocket is seriously cool for sure.

[CarVac]

@MasonH: Rocksim is fairly useless for supersonic predictions. OR and RASAero are better for that.

[MasonH]

I have two main concerns with this build. The first is how to give the fins enough structure to prevent themfrom snapping off. They will be mounted with JB weld and use thickened external fillets, but how do I get internal fillets? I have heard of using expanding foam with a high density, and have used the injection technique that Wildman uses. What are other ways to get structure in the small gap between the motor mount and the airframe?

Secondly, how do I get the motor mount installed the best? My guess was to thicken some epoxy and spread it around the inside of the tube, then slide the motor mount in. Will this work, or will i need to do something different? Again, expanding foam was something I was suggested to use, but I have never used it and it just seems like a hastle.

[grouch]

My fins were glued on with epoxy and chopped carbon fiber. The mixture makes a slug like slurry that I poked into the fin slot with a bamboo skewer. Then when I pushed the fins into the glob, it made filets on each side of the fin. Another thing you could do is not glue the rear centering ring in while you glue in the fins. This will allow you to filet the crap out of the fins at the motor tube. Once all set, glue the aft ring in. I considered that route but I wanted to be sure I had my spacing right for the Slim Line. The fins have a short span and are very stiff, if they are glued on well they won't go anywhere. I bet I could have glued it up with wood glue and been more than fine.

[Wayco]

I have built two of these, one from scratch and the other was my first HPR kit. Both of them I left the rear centering ring off and added epoxy to the TTW tab where it butts up to the MMT by injecting it and letting it flow up to the middle centering ring. I made an extra CR so there are three on the MMT. If you add anything to the epoxy, don't use so much that it won't flow, and you should be golden. Since the root edge is quite long, it really doesn't need a lot of reinforcing, and the space between the MMT and the BT is pretty small. Never foamed a fin can yet, but if I were going to fly this rocket on a J, I might consider that.....

[MasonH]

One of the thing I had not considered when I made my purchase was to buy an extra ring or two. If I had, I could pool the epoxy around the fin tabs. I think what I will do is make a tape ring like CJ does on the DD kits he sells, and make a fillet on one side of the ring with epoxy or JB weld. This ring will butt up against the fin tabs and allow me to inject fillets and let them flow along the tab without making a mess of the entire inside of the fin can

[grouch]

Just remember to keep weight in the back of your mind. That area is the last place you want to start stacking ounces and JB Weld isn't exactly light. The motor tube isn't really long enough to worry about another centering ring, you wouldn't gain anything. Even if you did fill the area with epoxy or something else, you still could break the fins outside the filets. If I were to do it again, I would still just glue it although I might do a tip to tip glass job. I may still wind up doing that but I don't think it is necessary. After all, I think Rick said he stuck a K (I know he put a J in it) in Thai Food and it was build with wood glue if I remember correctly.

BTW, when are you going to fill the spirals in your Phantom and paint that naked beast? You know legally you have to have it painted before the third flight. You knew that right???

[MasonH]

If I can get some time and some paint, that thing will kick some a** out on the field it looks so good. To hell with the spirals. Thats what primer and sand paper are for!

[MasonH]

So...I got a box today. It contained everything I need to actually BUILD the rocket except for the shock chord and nomex, which will be coming soon. I have all of the measurements made, the coupler and payload bay tube marked for drilling, the stiffy glued in, a tape ring made, the tubes sealed, the fins sanded baby butt smooth, and everything has been test fitted. Next I will Sand down the nose cone and drill the holes to feed the shock chord through, since I do not trust that little plastic piece that is already molded, and file a notch into the front ring. My buddy will come over sometime to get everything epoxied in place and drilled. He will then take it to his shop and make it look pretty.

[grouch]

Sounds good. At the rate you are going, you guys will get yours in the air before me!

[MasonH]

Ok, so I went ahead and drilled some holes for the E-bay. I inserted a few small machine screws and nuts, tightened them, and glued the nuts into place. I sanded the nose cone to make it smooth, put, JB Weld on the tape ring, and started fitting the parts together for a proper fit.

[MasonH]

I got some minor work done today in the 10 minutes I could. I got 10 yards of Kevlar shock chord from Top Flight Recovery, and split it in half. One half went into the ring on the motor mount that had a notch in it. It was encapsulated with JB Weld. Tomorrow, the ring will be glued in place with the same stuff, or so I hope. The motor mount was heavily sanded before gluing, removing most of the glassine wrap where the epoxy was placed.

[EeebeeE]

Expanding foam in the fincan does not add that much weight and it both secures the fins and supports the motor tube. The rocket can handle the stress save your weight so you can add a transmitter. This will fly out of sight and you will only see the apogee event if the sky is feel blue. Mine was dd and it still landed a mile away.
As far as sims are concerned, OR said my altitude on a J270 would be 7,000'. It ended up flying almost 8,500'. Nearly punched through our waiver.

[MasonH]

I already have the tape ring for pouring the epoxy fillets, but I did consider that. I will also be trying to get some random parts for the AV bay today while Im out tonight.

[MasonH]

Updates! I have the DD bay complete. I have small metal screws holding it in with nuts glued inside the stiffy tube, the stock eye screws are screwed into each bulkhead and epoxied down, there is a #8 piece of all thread running through the middle of the bay, which holds the sled into place. In addition, I have two small strips of 3/16" basswood to act as guides to help hold the sled in place. I will try to get some pictures later, but I am quite happy with myself. The sled can only go in one way, so I do not have to worry about lining up holes for switches.

[MasonH]

Here are some quick pictures I snapped of the rocket, or what will be a rocket.

[EeebeeE]

you connected your shock cord the way I did with one exception. I also tied a knot on the fincan side of the centering ring. You should be OK, though. It only takes about 1/2 gram of BP to separate the tubes.

Did you shape your fins. Amazing how much faster it will go if you sand them into an airfoil shape. I flipped my vibrating sander upside down, clamped it in a vise, then held the fins at an angle to it to shape them.

[MasonH]

Yup. I used a sanding block and did it by hand at first with rough paper then went to a finer grit and smoothed it all down. As for the shock chord, I don't think that it will be going anywhere soon without ripping apart the whole motor mount.

[MasonH]

I finished filleting the front centering ring yesterday. Now all that remains is to insert the motor mount into the body tube and attach the fins, rear ring, and retainer. Add fillets and buttons, and it is done! Granted that list is long, but it can all be done fairly fast with the right stuff.

My next question is this: how do i insert the motor mount for maximum strength? Do I spread some epoxy inside the airframe in front of the fillets and then insert the motor mount like the Estes kits do? What is the best way to do this?

[Wayco]

I injected epoxy onto the top of my upper CR with a syringe and a length of aquarium tubing. Found the syringe at a feed store, they use all different sizes for veterinary purposes. The aquarium tubing is a snug fit on the nozzle. Just drop it in and squirt some epoxy, roll the tube around and it forms it's own fillet. If you're quick, 5 minute works fine.

[MasonH]

I just spread around some thick epoxy with a dowel. The motor mount is in, the fins are in, the retainer is on, and the holes are drilled. All I need now are buttons and some thickener to make fillets. I have nomex and the parachute ready, so this thing is almost capable of flying in single deploy mode. Not going for DD anytime soon...

[MasonH]

TADA!!!