(by Matt Taylor)
Picture courtesy of Orbital
This is a 18mm boosted glider constructed almost entirely of high grade balsa
for strength and reduced weight.
- (1) 18mm Estes type tube with plastic ogive nose cone
- (3) sheets of pre-cut balsa for wings and elevons
- (1) blast deflector/air-brake (optional)
- (1) small lead BB for nose weight
Construction is not too hard. The only glue you need is some medium CA. The
pre-cut balsa made things easier. One thing that you have to watch is when
gluing the two wing half's together to make sure that both leading edges are
the right way. You have to cut slots for 8 mylar hinges that connect the
elevons to the rear of the wing which is the only real hard part of
building it. Cutting the slots in 2mm balsa, 10mm deep and trying not to break
the surface is hard. Seven (7) pages of instructions made sure that there were
no other gotcha's or unknowns.
Painting is not recommended as it will add weight and reduce glide times. One
light coat of sanding sealer is all that is needed. Any way the balsa looks
good on its own. A light coat of CA on the leading edges with help stop dents
out of 5
A B6-P is recommended for first flight or a C6-P if you like long walks.
It was very easy to prep. Just load the motor check the fins, etc. There is
no wadding required and tape is used for retention. Due to a very busy day
flying other rockets I could only fly it once. When it was loaded on the pad it
was not angled correctly so it was very fast and did two loops then glided back
Before you fly it you need to do gliding test to make sure it glides right, the
kit has included some Plasticine to balance out the wings if needed. A whole
page of the instructions is dedicated to testing so you can't go wrong.
The actual flight didn't glide too far but that could be because of it
losing the nose cone (didn't tape it on) but they are easily replaceable.
out of 5
I think that this is a great product and I will be looking a the bigger
versions of this "space plane". Highly recommended for anyone wanting
a change from standard rockets. TRUE quality!
out of 5
(Contributed - by Darren J Longhorn - 04/01/04)
The VMX-2 Spaceplane is a new rocket glider kit by the equally new UK rocketry
company, Orbital Engineering. You may have seen the pre-production prototype of
this kit flying at various rocketry events in 2002, including the IRW and
On opening the sturdy corrugated cardboard box, first impressions are very
good. Three sheets and four strips of balsa wrapped in bubble wrap, a nice
piece of BT-20, all the small parts in a resealable bag, and a very
comprehensive looking set of instructions. I should point out at this stage
that the kit supplied was a production prototype, and the final production kits
may differ slightly.
The Kit includes:-
- 3 sheets of balsa containing pre cut wings etc
- 2 triangular section leading edges
- 2 triangular section body fillets
- Plastic nose cone
- Coupler tube
- Launch lug
- Balsa blast deflector
- 2 lengths of elastic
- Lead weight
- Trimming putty
- Self adhesive aluminium foil
- Thrust ring
- 3 motor plugs
- Mylar strip
- 2 pins
- Comprehensive 9-page instructions
The first step is to free the wing parts from the balsa sheets and assemble
them. The wing parts appear to have been partially pre cut by some sort of
router. There are just a few tabs on each component which require cutting to
free the part. I found it best to do a "rough cut" first, some way up
the tab, to free the part. Then, once free of the sheet I did a "close
cut" to remove the remains of the tab. It’s best to do this final
cut from both sides of the part. The instructions indicate that either medium
CA or light wood glue may be used for construction. I wasn’t in any rush
(waiting for the glue to dry gave me the opportunity to write this review) so
used EVO-STIK wood adhesive and "double glue joints".
I found the wing assembly straight
forward with the exception of adding the leading edges. Although the
positioning of these is quite clear in the wing plan diagram, there’s
another diagram that I just found confusing. I couldn’t figure out what
it was trying to show me, or even be sure what view it represented. Suffice to
say that if you assemble the wings bottom side down, the leading edges go flat
side down too! The wings must be assembled with a dihedral. I found this quite
tricky and, once dry, had to fill a small gap at the aft end.
The next step is to add the elevons. These are attached to the aft end of
the wings using mylar hinges. You have to make slots in the aft edge of the
main wing and the forward edge of the elevon. I thought this was going to be a
bit tricky, but as long as you keep the knife horizontal with respect to the
wing/elevon, it’s not too bad. The positioning of the hinges seemed a bit
odd, so I made mine equidistant along the elevon (which was a mistake, the
manufacturer informs me that the unequal spacing is intentional). The hinges
are attached by pushing a pin through the fins with the mylar tabs in position.
Then CA is wicked into the resulting hole. This hinge design is very clean and
I like it a lot.
Fins & Strakes
The fins are added to the elevons next, and this was where I had my first
real trouble. Either the slots are too narrow, or the balsa the fins are cut
from is too thick. I fixed this by scoring across the fin at the top of the
tab, and then carefully paring away part of the tab thickness. The under wing
strakes had to be modified in the same way. Once the fins and strakes are in
place, the elevons are attached to the wing with the hinges, in the same way as
the hinges were attached to the elevons.
The kit can be made into two
slightly different versions, one for sport, the other for competition. The
difference is in the arrangements made for the venting of unwanted ejection
gases. In the sport model the gases are vented through a in the top of
the body tube. There are also parts to deflect the gases and strengthen the
body tube interior. For the , these parts are omitted and
instead the motor most be plugged forcing the ejection gases out of the motor
nozzle. I decided to build the sport model.
For the sport model the next stage is to cut out the vent hatch. This is
best done with a sharp knife. A section must be left uncut to provide a hinge.
This hinge is reinforced by the addition of a self adhesive foil strip. Enough
of this foil is supplied to add protection to the body tube just aft of the
vent. A cylindrical section of balsa is glued into place inside of the body
tube just forward of the vent to deflect the ejection gases through the vent.
Finally, a length of thick cardboard tube is fitted inside the body tube to
strengthen it. This buts up to the balsa deflector. The aft end of this
strengthener acts as the motor thrust ring. (For the competition model, an
ordinary thrust ring is provided.)
Next the body is attached to the
wings. You need to take care here as it’s all to easy to not get the tube
properly aligned. The triangular body fillets complete the main assembly. These
must be trimmed square at the aft end and glued into position. Once dry the
front end must be trimmed to match the leading edge wing extensions. The nose
weight is added to the nose cone, which is secured only with tape to facilitate
the addition of more weight during trimming.
The mechanism to move the elevons is installed next. This comprises a pin
pushed through the part of the fins mounted on each elevon, and two length of
elastic attached to the part of the fins mounted on the wing. The pins pushed
through the fins at 45° and secured using CA. Once dry the head of the pins
is clipped off. The elastic is attached to the fins in the pre-made
indentations (you did assemble them on the correct side, right?) and hooked
onto the points of the pins. The tension can be adjusted by stretching the
elastic more or less before hooking onto the pin points. You don’t need
much tension. The instructions specify that the weight of a spent C6 motor
should be just capable of lowering the elevon on to the strake.
The way the mechanism works is that, at lift off, the forces the
elevons into the flat position. Once in normal flight however, the tension in
the elastic is enough to overcome the airflow and raise the elevons for gliding
It this point, the instructions suggest that you might like to radius the
edges, but I think it's probably easier to do this as you go along, and that's
what I did. Next, I gave all of the balsa areas a coat of sanding sealer, and
then sanded smooth using progressively finer paper, until almost all of the
sealer was removed. This may sound strange, but the idea is to fill the grain
in the balsa, rather than add a nice shiny coating.
The instructions regarding trimming are quite clear. There are two main
parts to it, the elevon tensioning covered previously, and sorting out the
balance for gliding. This is done by test throwing the glider and adding small
amounts of clay weight to the wings to correct for any roll or pitch. My first
attempt at trimming, at 2003, led to the nosecone being pushed into the
body tube. In retrospect, there was too much breeze. The small amount of damage
was easily repaired.
Location: Baildon Moor
A perfect boost and translation to horizontal flight. Once flying horizontally,
the glider made a 180° turn, then appeared to roll over, and slide sideways
into what became a dive to the ground. The front body tube was crimped but
easily repaired. The crimped sction of tube was excised and replaced with a new
section, attached by means of a short coupler.
Before the next flight, I spent a lot more time at IRW 2003 trimming. There
was a gentle breeze and I got it so it would glide really well either with, or
against the breeze.
Location: IRW 2003
Once again, a great boost and translation. Again it made a turn, but this time
much wider. There was no roll, but the glider slowly pitched down and picked up
speed. This was never corrected and it dived into the ground. Amazingly, there
was no damage at all.
Location: IRW 2003
Another great boost, but the flight was just a higher version of flight #2.
What did I expect? This time there was a lot of damage. The body tube is folded
up and the wings are broken across the span. It will be a big rebuild, which I
haven't yet attempted.
I think the problem with the first flight was lack of trimming, that led to
it rolling over and diving. For the second and third flights, I wonder if I had
the elevons tensioned correctly? The tensioning is meant to be set such that
the elevons are flat for the boost, and pop up for gliding flight. It might be
that I didn't have quite enough tension. Therefore, as the glider pitched
forwards, it picked up speed, and the increased wind speed forced the elevons
into the horizontal position. Once that happened it would never be able to
correct its . I did follow the directions for tensioning, using the
spent motor on the elevon, but maybe the exact position is critical? I passed
on my thoughts to Orbital, but disappointingly, I never got a response.
This is an excellent kit. It's not exactly cheap, but the quality of the
parts is second to none, the instructions are detailed and comprehensive, and
even the packaging is first-rate. I really enjoyed building it. I must point
out however that I can't recommend this kit for a beginner to rocket gliders.
Despite the detailed direction, I never really had a successful flight. Since
I've seen and read about many other successful flights of VMX-2s, I have to put
that down to my own inexperience with rocket gliders which is limited to a
couple of flights of an Estes Tomcat, and a few flights of an
"AstronMike" style saucer glider. I reckon that either the trimming
wasn't up to snuff, or that I didn't get the elevon tension correct. So in
conclusion, this is a great kit, but if you're a beginner, practice your
trimming on something cheaper first.
This article was first published, in two parts, in 10...9...8... the
newsletter of the United Kingdom Rocketry Association.
Between publication of the first part of this article and the second, I was
informed by Verney Montague that have put up a handsome Gold Medal to be
awarded to the first person to break the two minute barrier with a rocket
powered Spaceplane. The medal has actually been around for 2-3 years. Anyone
know if it's been won yet?