(08/09/08) The Hydra VII is my second Semroc kit. My first one,
Lil' Hercules, never got reviewed by me and
only saw one flight as it vanished from the pad. My second impression of Semroc, which confirms my first, is that they
run a very professional company.
From 1969 to 1971, "Semroc produced a full line of rocket kits and engines.
At its peak, Semroc had twenty-five full time employees working at two facilities." 31 years later, Semroc is
back with updated kits. I say, welcome back... and when will those engines be produced again?
Anyhow, back to the Hydra VII. One has to say "wow" when this small
package is opened up and explored. There are a lot of parts packed in this plastic bag. The rocket that is assembled
from all these parts equally deserves a "wow".
There are simply too many parts to list, however, some key parts includes solid
balsa nose cones and tube coupler. The fins are laser cut 1/8" balsa. The body tubes are standard tubing. For more
details, follow along.
The instructions are printed on the front and back of six pages of
8½ x 11" paper. These are neatly attached and assembled into an instruction booklet with a cardstock cover.
The instructions are full of excellent illustrations. Top quality and possibly even better than color photos. There is
a tube marking (2D) template, finishing, and set/flying instructions included in the booklet. As I stated, very
professional from the front color illustration and product specs to the last page listing the NAR Model Rocket Safety
The build of the Hydra is typical of other rockets, however, there are some
highlights that should be pointed out.
The laser-cut fins are awesome. And, interestingly these are worked on first. They
are sanded and sealed right away. This is an important step, because once this bird is assembled you would not be able
to reach all the fins to give them a nice finish.
Next, all the motor tubes are glued together to form a 7-motor cluster. A central
18mm tube, surrounded by six outer 18mm tubes. These motor tubes make up the the lower 1/3rd of the rocket. They also
form the inner structure of this portion of the rocket.
Next, the six long fins are glued into the joints of the six outer 18mm motor
tubes. These are the inner fins, the ones you will be glad you pre-sealed and sanded!
Next, the outer ring is marked and then attached to the six inner fins. I had to do
just a tad bit of sanding on them to allow the tube to slide over the fins nicely.
The six outer motor tubes are then plugged using a laser-cut fiberboard disc that
is glued to an 18mm thrust ring. These are then glued into the bottom of the six outer tubes by using a provided
"Engine Spacing Tube" to ensure they are all even. There is a note highlighted in the instructions here. It
says, "Some builders prefer to leave more engine mounts open to increase the odds that in case all engines do
not ignite, there is a backup." Did I? Nope, so lets see what happens. Frank Whitby did according to his
The central 18mm thrust ring, gets a Kevlar
shock tether tied to it, prior to being placed in the tube.
For the above two steps Semroc included a glue applicator (Q-Tip) and a
"Engine Spacing Tube" as tools. This again highlights Semroc's thoroughness (professionalism).
What I found to be the most difficult part of the build is next. First, the 3
small balsa nose cones need to be cut in half and then sanded on a piece of sandpaper attached to the large body tube.
This allows for a good formation of the balsa nose cone halves. These are then placed into the six outer motor tubes.
The main body tube should slide down inside the circle formed by the six nose cone halves. I had to make several
attempts, sanding more on the nose cone halves each time. When the fit was good, everything was glued into
Now come the 15 fins! First the three main fins are glued in place. I made a
mistake here and had to cut two of them back off. To avoid the mistake I made, pay close attention to the marking of
the out tube instructions. After the three main fins are in place, then four smaller fins are glued in-between each of
the main fins. Yep, a total of 21 fins are on this rocket when complete with this step.
The rest of construction is quick. An elastic shock cord is attached to the
Two 12" parachutes are attached to this shock cord. An eye-screw is added to the bulkhead (coupler) and then it is
glued in place to the upper body tube. To this another elastic shockcord and another 12" parachute is added. The
nose cone is then added. I glued mine in place, even though it is designed to be a payloader.
I have to admit that I had a lot of trouble finishing this rocket. I used my
typical method with Plasti-Kote Primer and worked it quite a bit. Even after that though, I still had grain showing in
those hard to reach spaces between the fins and the balsa nose cone halves on the top of the motor tubes.
The rocket then sat for a long, long time. I finally got motivated to put some
paint on it for NERRF4 and was determined to fly it. Well, the paint reacted and didn't look so good. Oh, well, I was
still determined to fly it.
Overall, for CONSTRUCTION I would rate this kit
points. The instructions are descriptive and easy to follow. Laser-cut fins and the decals really add to the
quality of the kit. Again, the most difficult part of the rocket is the finishing portion.
Unfortunately, the rocket didn't get put in the air at NERRF4 so I shipped it to
Virginia to be flown at NARAM50.
I decided to fly it for the first time 6x C6-0's and a C6-7 in the central motor.
I used Estes ignitors and wired them all together with some copper wire. I then taped each wire joint.
The cluster launch was exciting and it is always nice to see the extra smoke and
flame. People were saying, "I saw at least 4 light" and "I think they all lite". That is the case,
you know, you never know until your recover the rocket.
Recovery?! Well, the upper section drifted and drifted and while I kept looking
back and forth I was comfortable that I saw where the lower section landed (on the two chutes). The upper section
though went way out of the field. I made one sweeping attempt in the very over grown section of swampy weeds and then
said to myself, "oh, well." As the old saying goes, "If you don't want to lose it, don't fly
With that I doubled back and tried to go where the lower section landed. To my
surprise I did not find it either. Later in the day, someone pointed out where it was. I went in after it and received
two good scraps across the shin from thorny weeds and my Hydra VII lower section.
So, you must be wondering, "how many motor lite?" The answer is six. The
most important one, the central motor and 5 of the C6-0's. Interestingly, all the C6-0's that lite pushed themselves
out of the motor tubes and disappeared. No sure that is a good thing.
For FLIGHT/RECOVERY, I would rate this rocket
points. It is a complex looking rocket, however, if flown with a single motor it is very easy to set up. As a
cluster, I'm concerned about the kicking motors and that should be addressed. I see from other's experiences that most
like the flight of the rocket and I have to admit it brings a level of excitement to the model rocketry flying field. I
decided to give it "average" which is a good rating due to the complexity of the cluster set up and no motor
I give the rocket an OVERALL rating of
points. If you are looking for a nice project and one that you could do a great job finishing, then the Hydra
VII is the rocket for you. It has excellent quality of parts and instructions. Take your time though and think out your
finishing plans. You may choose to finish some fins before gluing them in place. Semroc does put out quality
(by David Hash - 04/16/04)
The Hydra 7 is a currently the "newest" kit by Semroc Astronautics
(originally released in 1969 and re-released on January 1st, 2004). The rocket
is based around six 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
C6-5s to 7 C6-7s. With its largest motor setup (7 C6's) it is supposed to reach
1700'. For recovery it splits into two sections, the payload comes down under
one 12" parachute, and the booster on two 12" parachutes.
All parts came packaged in a large plastic bag, with the smaller ones being
inside their own small bag. All parts were in excellent condition and all
- 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
- 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 supplied 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 necessary but 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 of them! (And
thank goodness they were all laser-cut!) After that is done, you assemble the
payload section (glue in coupler and screw eye), and the other little things
you do at the end like fillets, launch lug, etc. Construction was pretty fun,
and I liked the way that everything fit almost perfectly.
Picture courtesy of
For finishing, I first sprayed the entire rocket with white primer. I then
touched up rough spots with sanding and putty until when I primed it everything
was smooth and filled in (spiral, balsa grain, fillets, etc.). I then sprayed
the entire rocket with white gloss Krylon paint. When that was dry, I sprayed
the payload tube and nose cone Krylon gloss blue. After that was dry, I applied
4 of the many decals the rocket comes with.
out of 5
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.
First flight was with only one C6-3 just to test things out. Worked nicely,
with a slow, majestic ascent.
Second flight was with seven C6-7s.
First attempt: Wired up 7 high current igniters to the motor and twisted
the wires together. 5-4-3-2-1-Lauch...nothing. Too 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 some of
the current 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 apparently burned, because all of the motors
PROs: Full cluster ignition is incredible to watch. Attracts a lot of
attention on the pad.
CONs: Hard to light all motors, especially with high-current igniters. The
only igniters I found that would work are Estes Solars, but for those you need
a clip whip because the wires aren't long enough to twist together.
First Flight (1x C6-3): Loosened one fin on impact, but that was my fault,
because I only attached one of the parachutes to the booster section. Fin was
easily fixed with some CA glue and accelerator.
Second Flight (7x C6-7): If you ever fly this rocket on the full load-out
of motors, you may want to consider tying the two sections together or
installing a micro dual-deployment device because this rocket DRIFTS! I had to
walk about 1/2 mile for the booster and then the payload was another 1/2 mile
past that. Whew! I'm glad I didn't put the two parachutes on the booster for
that flight! Anyway, the same fin loosened again at the fillet, but that can
still be repaired.
PROS: Recovery device is well made and anchored well. Provides an okay
CONS: Drifts very far even without one of the three parachutes.
out of 5
Overall, I really enjoyed this rocket in building and flying. The only thing
that needs a little work is the recovery system. If you buy it you will not
regret it and you will have a lot of fun with it. Currently this is my favorite
rocket out of a fleet of about 20.
out of 5
(Contributed - by Frank G. Whitby - 09/28/04)
Semroc Hydra-VII is a 7 motor cluster rocket with a futuristic design.
The kit included every part that was described in the long list. There is a
very nice exploded view of the rocket in the instruction sheet that helps in
identifying the wide array of parts, along with 3 sheets of very nice laser-cut
balsa fins and a host of tubes and several nosecones. The kit comes with some
plastic parachutes that require assembly. All of the hardware seemed to be
complete and adequate. The step-by-step instructions are clearly illustrated
I built the rocket according to instructions, using all shock cord, screw
eyes, etc. that came with it. The construction process involves assembly of the
big, complicated-looking rear section consisting of a big ring fin (referred to
in the instructions as an augmenter shroud) with a host of small radial fins
both at the interior and exterior of this ring. The fins were very easy to deal
with. The instructions suggested sanding them to size at a couple of
appropriate points. The instructions suggest appropriate fin-alignment markings
and alignment techniques, making the fin assembly straightforward throughout.
The instructions suggested yellow glue for the fins. I used medium CA to
securely tack all fins in place and then added very limited yellow glue fillets
throughout. In many places I had difficulty adding fillets because my fingers
are too big to fit into many of the narrow inner fin spaces.
The instructions begin with an extensive description of the assembly of the
7 parallel motor tubes. The description is I think overly laborious but is
clear and does a good job of insuring that the foundation of the rocket is
secure and correct. The interior fins are slotted between the 6 motor tubes
that surround a central motor tube (all motors are 18mm). The big ring fin fit
over the inner fins like a charm after sanding the edges of the inner fins a
bit. I made this fit too tight at first during a dry fit, resulting in some
obviously bent, overstressed inner fins. I removed the big ring and performed
the aforementioned sanding of the inner fins resulting in a tight but gentle
fit. When gluing the big ring in place, I pressed it aft, onto the table,
making the rear edge of the ring flush with the aft end of the motor tubes. I
then realized that this was not according to the design. I noticed that the
rear edge of the inner fins sweep forward about half and inch. This fine point
was not easily seen in the otherwise very detailed drawings in the instruction
manual but is something that an experienced builder should have picked up on.
The ring was meant to be installed so that its rear edge is flush with the rear
edge of the inner fins, not the rear end of the motor tubes. I could not
reverse this step, so I continued on, reasoning that this flaw would not be
detrimental to flight and that the rocket would look nearly as intended.
Addition of all exterior fins was quickly done with CA and went without a
The 7 motor tubes all butt up forward to a large body tube. The 6 outer
motor tubes each get half of a nose cone, creating the cool nubbly transition
from the rear motor assembly to the single large body tube up front. The balsa
nosecones must be cut in half and sanded to fit. I used my small belt sander to
aid in this process and got a pretty good fit all around with the judicious
addition of some masking tape here and there. I think that assembly of these
nosecones pushes the skill level of this kit beyond the reach of a beginner but
makes it suitable for someone wanting a significant challenge. Assembly of the
long, beefy front tubes and nosecone is straightforward. The instructions
suggest plugging all but the central motor tube. I left 3 additional tubes open
to allow for motor ejection, in case all motors do not light. This needs to be
considered carefully when preparing for flight.
During construction of the rocket, it occurred to me that finishing the
rocket with anything close to the recommended color scheme was going to be
extremely difficult due to the intricate nature of the rear assembly. I decided
early on that I would have to dream up some simpler paint scheme especially
since I don't like to spend much time painting my rockets. Masking off detailed
areas of the rocket would obviously be very difficult. Sanding the details was
going to be a challenge as well.
PROs: The instructions are detailed and well illustrated. The parts are all
good quality, especially the fins.
CONs: I messed up the position of the augmenter shroud and the instructions
might provide slightly more detail emphasizing the intended construction method
here. In the end though, it was I who slipped up. Assembly of the plastic
chutes is probably not worth the effort. I substituted some preassembled chutes
that I had on hand.
By the time I completed construction, it occurred to me that I am not
particularly enamored with futuristic design model rockets. I admitted to
myself that I chose this kit because of the 7 motor cluster flying challenge,
not because of the futuristic design. Thus, I decided that I would not go to
the trouble of carefully sanding details and hand painting all of the fins
according to the manufacturer's recommendations. I wanted to be able to mask
off large areas and spray the rocket, thus I proceeded to mask off things in a
generally fashion and sprayed it red, black, and silver. I decided
not to apply the decals since I did not count this paint job among my best. If
my son decides to repaint it, he can apply the decals at that time. My
enthusiasm for the rocket was flagging considerably as I imagined the effort
that it would take to do justice to the design with a perfect paint job.
PROs: The tubes and fins hold paint just fine and minimal sanding was
required before I gave it a rather poor paint job.
CONs: I am not fond of the detailed painting required. If I were to
redesign the instruction sheet for this rocket, I would suggest that all fins,
tubes, and nosecones be painted before assembly. This would actually be very
straightforward and would not interfere with assembly, providing even the most
unenthusiastic painter the chance to finish the rocket in near-archetypal
½ out of 5
For the first flight, I used 4 C6-5 motors. Rocksim puts this at about 1200
feet. It think that might be a bit higher than it actually flew. All 4 motors
ignited and the boost was straight and nice. The boost was a bit slower than I
expected, which gave it just a little bit of a majestic look to the takeoff.
All motors fired their ejection charges. The upper section recovered fine on a
12-inch ASP mylar chute (a bit too much chute for the upper part), but the
lower part had troubles. The rocket came down like a perfect inbound missile
and lawn darted rather badly. The 18-inch plastic chute that I had intended to
recover the heavy lower section of the rocket was melted into a blob, hence the
poor recovery. Perhaps I forgot to install recovery wadding? I just cannot
remember... I did not notice any wadding fly out at deployment, but I also
might not have been paying that much attention either. The main body tube is a
complete loss, but all of the small nosecones and all parts aft of the
transition appear to be in perfect condition, so I think that I can rebuild it
fairly easily. I suspect that upon rebuilding this rocket will take on a new
character and may get bashed into something unusual--requiring a new paint job,
I installed the recovery system as suggested and I think that it is adequate.
PROs: Nice boost, very stable flight (even when coming down without the
front section). Clusters are cool.
CONs: None, other than the problems I caused myself. Also, I would prefer
to recover the rocket in a single piece rather than according to its current
½ out of 5
The Semroc Hydra-VII has the look of a complex, futuristic design rocket that
flies with a 7-motor cluster (7 x 18mm) and recovers in 2 pieces. I purchased
the rocket in order to experience the cluster flights and only during
construction and finishing did I admit to myself that the futuristic rocket
design does not hold a special place in my heart despite having grown up around
a variety of such groundbreaking designs (like the Mars Snooper). I just do not
recall having ever been drawn to the sci-fi aspect of model building. I am thus
not a good judge of Semroc's entry into the retro design and clone arena. I
think that they have done a very good job assembling a kit from quality parts
and they have simplified the assembly of this complex kit. I have a couple of
other kits from Semroc, but I will skip building their other futuristic design
kit, the Laser-X, since I probably would not do it justice.
out of 5