Semroc Hydra 7 Review

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Pyro Pro

Well-Known Member
Jul 24, 2003
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The Hydra 7 is a currently the "newest" kit by Semroc Astronautics (original release in 1969, new release on January 1st, 2004). The rocket is based around 6, 18mm motor tubes, and is a great clustered, high altitude payloader, and retails for $23. The rocket can fly on anything from 1 C6-3 to 3 C6-5's to 7 C6-7's. With its largest motor loadout (7 C6's) it is supposed to reach 1700'

I bought this kit last Saturday at the Whitakers launch, and have been working on it nonstop ever since. I finished it today around 1:00.
All parts came packaged in a large plastic bag, with the smaller ones being inside their own small bag. All parts were in exellent condition, and all there.
Parts List
2-Body Tubes 1.69"
7-Body Tubes 0.79"
1-Body Tube 3.63"
1-Nose Cone 1.631"
3-Nose Cones 0.714"
4-Laser Cut fin sheets
1-Balsa Tube Coupler for 1.69" Tube
1-Launch Lug 1/8"
1-Screw eye
2-Elastic Shock cords
1-Kevlar Shock cord
3-Parachutes 12"
3-Sets of shroud lines
1-Wooden dowel 3/16"
7-Thrust rings
6-Plugs for thrust rings
1-Decal Sheet
1-Engine spacing tube
1-Q-Tip for glue application

Construction starts with sealing the fins, because there are so many it would be hard to reach them after the rocket is finished. I used about 3 coats (on each side) of some type of spray on sealer, although I'm not sure what brand it is. Next, you glue together the 7 motor tubes in a six-point star pattern. From here, you attach the 6 shroud support fins in between the joints of the motor tubes (LOC Viper style). Then you glue on the shroud, and put in the motor blocks. The six outside blocks are plugged with cardboard disks, and the central one is left open for the ejection charge to go through. The next step is where the rocket begins to get its unique appearance. From the outside, the nosecones in the kit appear to go halfway through the body tube. However, instead of cutting the body tube, you are supplyed with 3 nose cones. You have to cut each one in half, and then sand the curvature of the 1.6" tube into the side of them so they conform to the body tube. I thought this step would be the trickiest of them all, however it was quite easy. First I cut the Nosecones in half with a microsaw, then I used a drum out of a drum sander to sand down the curve on the nosecones. Once you get that done, you test fit them into the booster tubes and slide the Main body tube down onto them. You are supposed to re-sand if nesecsary, however I didn't have to. The next few steps involve gluing on the fins, which I'm sure everyone here knows how to do just fine. The only little catch with the fins is that...there are 21!!!(thank you laser-cutting:rolleyes: ). After that is done, you assemble the payload section (glue in coupler, glue in screw eye), and the other little things you do at the end like filits, launch lug, etc.
Contruction Rating 5/5

Finishing: I still havent't painted it, givin that there are about 4" of snow on the ground outside and the temperature is about 20degrees Farenheight. However, I don't have school tomorrow, so I may paint it then. I'm thinking blue payload and nosecone, blue cluster tube nosecones, and white everything else.

Flight: I plan to fly it at the Febuary 2004 Whitakers launch, with paint of course.

Overall, a very nice kit. Everything fit well, which definatly made constuction simpler, and the laser cut fins are a nice touch, especially with the number on this rocket. I can't wait to fly it, so I may take it to the field by our house and fly it on a single C6-3 (250'), but I'd hate to crash it before I can fly it full-up on all 7 motors. So, if you don't already have one, I'd buy one, because, even on display, it is a spectacular kit.

Overall rating: a well deserved 5/5

Mini Review: Rocket Stand

I got this along with the kit, and it is designed to hold the small specification card that comes with Semroc kits, as well as the rocket. All parts are laser cut thin cardboard, and it goes together nicely with laser-cut precision. You can see it holding the rocket in the picture below.

Sweet looking design there, and I like the display stand. I forgot that Semroc has the stands available for purchase.

Did you have to apply any weight to the front end on this kit ?..I ask only because thats a lot of weight, fins and boosters on the business end. 8) many great rockets coming out from company's like Semroc, Roachwerks and Fliskits - along with Thrustline Aero, its hard to choose. lol

Thanks for the review,
No, I didn't put any weight into the nose, because the instuctions don't call for it. I guess it has enough fin area to keep the CP back in a resonable position. the RocSim file showed that it was fairly stable with 7 C motors loaded. If anything should arise, there's still plenty of room in the payload.
I think that in the slang dictionary, under 'Kicks Butt' there is a pic of the Hydra! :D

I cannot wait until I build mine. It is in the queue right now, and the weather is just not lettin' me finish the projects I have already started.:mad:
At long last, I finally got to fly it! Last month's launch was cancelled due to snow, so I had been waiting anxiously for this month.

Whitakers, NC
First Flight: Motor(s): (1x) C6-3

First flight just to test things out. Worked nicely, with a slow, majestic ascent. Loosened 1 fin on recovery, but nothing a little CA couldn't handle.
First Flight Rating: 4/5
Second Flight: Motor(s): (7x) C6-7

First Attempt- Wired up 7 high current igniters to the motor and twisted the wires together. 5-4-3-2-1-Lauch.......nothing. To little current coming from the launch controller.

Second Attempt- Same igniters and setup, but used leads from the high-powered pads. Still no go.

Third Attempt- Took out 3 motors to have a 4 motor cluster. Used leads from high-powered pads. 5-4-3-2-1-Launch......Smoke......nothing. Igniters in all 4 motors burned, but not the motors. The igniter plugs seemed to have insulated to heat because only the lower-most part of the igniter had burned, and the pyrogen was still intact on the upper portion, the motor touching portion.

Fourth Attempt- Used a clip whip (Thanks to Dave Morey for supplying it) to wire up 7 Estes igniters. 5-4-3-2-1-Launch....Smoke....FIRE!!!
The rocket roared up into the sky, with the full fury of 7 C6 motors burning in the rear. After about 3 seconds, with the rocket barely in sight, POP! POP! POP! POP! POP! POP! As the 6 outboard motors were ejected. The central motor ejected the parachutes and it drifted about 1/2 mile downwind. Post-Flight inspection showed that all motors had apparanty burned, because all of the motors ejected. The fin that had broken on the first flight had come loose again, but other than that, no damage on the booster section. The payload section was recoverd another 1/2 mile or so farther in another field.
Second Flight Rating 5/5, but it actually deserves more (like a 7/5).

Still haven't got round to painting my Hydra VII yet. :rolleyes:

Thanks for the flight report, Pyro. Glad to hear that a 7-motor ignition is possible.

Weathers getting better over here, so I'm going to have to get mine painted 'cos the launching season is almost apon us.

Any pics?
Originally posted by cydermaster

Thanks for the flight report, Pyro. Glad to hear that a 7-motor ignition is possible.

It's a doddle if you use quickmatch.
I think I know someone who got a picture, so I'll see if I can get that one.