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| R&D B Division Prizes
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B Rocket Glide |
For NARAM-46, the Rocket Glide event is for B engine class.
Rocket Glide
combines the challenge of building and flying a glider which remains in one
piece for the whole flight, which can boost relatively well (and hold together)
on rocket power, and transition to a long gliding flight.
In Rocket Glide, the glider must remain in one piece
for the whole flight. Nothing can come off - no pop-pods, no parasites, no
ejected engine. It cannot be staged. The glider must be returned for one
of the two flights allowed.
Flex-wing (Rogallo/hang glider) type gliders are not
allowed.
For the full rules for this event, please see
the Rocket Glide Rules
on the NAR web page.
Scoring -
For Rocket Glide, the scoring is the total of two flights allowed, but at least
one of those flights must have the glider returned.
Design considerations - Difficulty of making and flying a glider that does
not have any parts come off in flight (Often with a design that uses some sort
of moving parts like a sliding wing or sliding pod). Trade-offs of high glider
performance and visibility with surviving rocket boost, and trying to get at
least a reasonable boost altitude.
Rocket Glider designs are more specialized than Boost
Gliders, so it is not recommended for newer fliers to try to design their own.
Best to go with a kit such as those below, or a plan. With experience, you
might later develop a knack for designing your own gliders, but it's best to
learn from something proven first.
A list of plans and kits is
included further down on this page.
Designs - Many basic design approaches have been used for
Rocket Glide. Here are a few:
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Slide-Wing -
The wing is mounted in a manner that allows it to slide along the fuselage, so
the wing is towards the back for launch (moving the CP rearward), then at
ejection moves forward for glide. They tend to boost very straight. The wing
slide mechanics are somewhat more difficult to build than others, but it is
usually worth it.
Slide-pod -
A long engine pod about the length of a normal pop-pop is used. The pod is
forward on boost (making the CG forward like a normal pop-pod B/G) then at
ejection slides back so that the CG is where it needs to be for glide. It is a
reasonable approach which usually boosts OK, and is easier to build than a
slide-wing. Well-made slide wings tend to perform better than well-made
slide-pods. Slide-pod models use a telescoping external tube glued to the
pylon, such as 20mm telescoping tubing, for a BT-20 sliding pod tube to freely
slide inside of.
Auto-Elevator
- A design which does not move the wing, or move the CG, but changes the angle
of the elevator (or canard). The elevator has to be flat (straight) for boost
so there is no incidence between the wing and tail, so the model will boost
straight. For glide, the elevator moves up (or canard trailing edge moves
down). This is often one of the simplest and easiest rocket glider designs to
use. Although depending on the particular model design, the performance
potential might be compromised.
The Xebec-B is an auto-elevator design, which is easy
to build as R/G's go. But it is somewhat finicky as to how straight it boosts,
varying from model to model (and sometimes modeler to modeler). Usually it if
does not boost straight, it pitches up a bit onto its back, due to unintended
slight positive incidence.
Swing-Wing -
Originally a definitive early design for Rocket Gliders, the wings pivot from
rearward for boost to forward for glide. They are neat to see fly and deploy,
but tend to be too heavy and complex to be competitive other than in the higher
engine classes. For B engine class, it's not very competitive.
No Moving Parts
- A special design that, as it's name says, has no moving parts. So, it is
about the simplest Rocket Glider to build (That has wings, anyway). This
approach was tried when the event was first created, but only experts had any
decent success trimming their models to boost straight and transition to a glide.
More recently, Kevin Wickart has come up with a design called the "Mediocre
Fred", which is not as finicky as the early designs, but must
be built exactly as described. It was a plan in Sport Rocketry magazine, and
also is available online on the WOOSH website. It is designed for D power, but
can be flown on a B6-2. Ideally, for B class it should be scaled down.
"Backslider" Superroc Rocket Glider - Bob and Peter Alway wrote a winning R&D report
resulting in the "Backslider" plan. It is a type of super roc rocket
glider, which is basically a long skinny "normal" rocket going up,
that glides down backwards using lift from the long body tube and fins (read
the report to understand how). It does not glide very well compared to normal
R/G's, but has been used by some for qualified flights and "return"
flights, and in some smaller contests has taken places when used as the primary
(or only) model a competitor used. Depending on the resulting CG due to the
parts used and assembly, a given Backslider model might require a little bit of
clay (not too much) to be added to the root of one fin to make sure it glides
rearwards, rather than falling horizontally (which is not a glide).
Deployment magic
- All of the above R/G designs (excluding the Backslider) use the ejection
charge only as a starting point to cause the design to go from rocket boost
mode to glide mode. Usually rubber bands are used to make the wings slide, pods
slide, wings swing, or elevator to move. What keeps them from moving until
ejection? Usually a burn-thread which is rigged to hold the model in boost
mode. At ejection, the thread burns, allowing the rubber bands to do their
thing.
The burn thread needs to be thin so it will burn
easily. The button and carpet type of thread that Estes uses for shroud lines
is too thick for anything short of a D12 ejection charge to burn. So use a
finer thread. I prefer to use white elastic thread, which will snap free when
it burns.
The rubber bands need to be selected carefully. Do not
grab just any rubber band and try to force it to stretch really far, as it
might cause the model to actually break itself when the band force causes the
model's parts to slam into each other too hard at ejection. Look for rubber
bands with 1/16" cross sections, in various lengths, at Office Supply type
stores. Look for the classic pale brown latex bands, colored bands tend to not
stretch as much. While the band should not be stretched so much that it causes
excessive force, it should not be relaxed at the end of travel so that there is
slack, as it might not deploy the wings, pod, etc, 100% as it needs to. This is
not hard to get right, just it can cause trouble if it's overlooked.
Building Gliders
- Jeff Vincent's Nocturne Slide-Wing Rocket Glider plan includes a lot of
useful instructions on how to build, trim, and fly a Rocket Glider. It also
includes some information on how to rig up the thread and rubber band system,
useful to know for any slide-wing. The written
article is here, and the 11 x 17" plans are here.
Ed LaCroix created some fantastic instructions
for the Maxima A Boost Glider kit, from the time when Ed owned and
ran Apogee. The instructions are so in-depth that they are a must-read
for anyone wanting to learn more on how to build, trim, and fly rocket boosted
gliders of any kind. Please note that the Maxima is a BOOST Glider, not a
Rocket Glider, so that design is not legal for this event. But the general
"how to build and fly glider" information in those instructions is
very useful.
Kevin Wickart wrote a nice short article on how to do
quick and easy airfoils, on the WOOSH section's website. Click
here to read it.
A VERY nice sanding block, useful for gliders,
helicopter, and any rocket really, is an all-metal 2-piece clamp-type sanding
block made by Red Devil, carried by most Ace Hardware stores (look near where
they stock sandpaper). It has a 1/8" foam rubber backing sheet, which
ought to be removed since it allows rounding things too easily in 3-D when you
usually want to shape in 2-D at a given time (as with a wing). So, remove the
rubberized portion. That sanding block holds a 4.5 x 5.5" sheet of
sandpaper (quarter of a 9 x 11" sheet), with a 3.5 x 4.5" sanding
surface area on the block. This works far better in most cases than a narrow
sanding block. Of course, the wings (or fins) should be shaped and finished before
they are glued to the fuselage or model.
When doing very rough shaping for wings, 80 to 120
grit sandpaper is good to grind off a lot of wood in a short time. Don't
over-do it though by sanding off too much. Then go to finer grit like 180 to
220 for finer shaping. Beyond that, 280/320 paper, is sort of a cross between
final shaping and setting up for a final finish. A final finish for bare balsa
is to use 400 grit paper. Get the "black" type wet or dry sandpaper,
it sands better and lasts longer than the reddish types. If you use any clear
dope, use 320 to 400 grit paper before and after.
Glider Finish
- Never use paint on a contest type glider. For newer fliers, no finish is
usually fine. You don 't want to weigh the model down too much and maybe having
warpage problems. If you want to improve the finish, use some thinned clear
dope in one or two light coats, sanding before and after with 240 and 400 grit
sandpaper. The idea it not to add weight or cause the wood parts to warp. Some
fliers like to use a Japanese tissue finish, but that is more for experts and
to an extent is overkill for A B/G's.
Coloring -
OK, so bare balsa (even with clear dope) is not easy to see in the air or on
the ground. Use a large black magic marker to color the bottom of the wing and
tail surfaces black, as that shows up against the sky pretty well. Use a large
red or orange magic marker to color the top surfaces. If you can find true
fluorescent markers (not to be confused with wimpy fluorescent highlighters),
an orange or red/magenta fluorescent color is highly recommended.
Glide trimming
- It is an understatement to say that it is very important to trim the glider
to glide properly. It's not easy to describe just how to do so.
One mostly universal tip is to have the tail of the
glider and the wing to not be parallel to each other (zero incidence). There
ought to be a little bit of "up elevator" angle in the tail, relative
to the wing, to make the nose pull up a bit. Some plans/kits may be quite
specific, and in those cases go with what they say (for example the Xebec-B
auto-elevator design requires absolute zero incidence for a straight boost,
then up elevator for glide). Note that free flight model airplane experts
sometimes prefer zero incidence, but they are deeply experienced (usually) to
have just the right touch and experience to get away with it.
The above being said, one of the simple ways to
achieve slight positive incidence (without adding too much) is to build the
model zero-zero, then warp the trailing edge of the stabilizer up. Make sure
that the fuselage itself is not warped "down" - if it is warped at
all, better to be warped "up" relative to the wing and stabilizer.
Special trimming notes for Rocket Gliders –
- Always
trim with a burned-out engine casing in the model, using the same
engine type you will fly it with. If you trim with no engine, or an
unfired engine, the CG you try to trim for will not be where the real
flight's glide CG will be.
- For
Slide-Wing models, do not glue the forward wing stops on before going out
to do some basic trimming. Use tape to hold the wing from sliding along
the fuselage, and do a few trim throws to see if you have the wing in the
right ballpark location. If the model seems tail heavy, move the wing back
a bit, and re-tape. If it seems nose heavy, move the wing forward a bit,
and re-tape. When it seems to be in the right spot, use a pencil or pen to
mark on the fuselage exactly where the wing should stop, then later glue
the stops on at that location.
- For
Slide-Pod models, do not glue on the glide position stop ring (near the
front) to the slide pod until doing a similar series of rough glide trim
tosses as described above for slide-wings, in order to determine where the
slide pod should stop for glide.
- For
Auto-Elevator models, the trimming is unique. The elevator needs to be
absolutely flat on boost, so the model will boost straight. Auto-elevator
models tend to be designed a bit nose-heavy, so there should be no need to
add any noseweight. So the way to trim an auto-elevator model (at least as
far as pitch trim), is to adjust the elevator angle until it glides
properly. If it stalls, adjust for less elevator. If it goes into a
shallow dive or just feels like it is gliding too fast, adjust for more up
elevator.
General trimming tips from a number of different
sources:
Estes Boost Glider Technical Report, written
by Tom Beach (pdf file from Estes Educator website). An excellent
article with many illustrations, that cover
a wide range of areas involving Boost Gliders and Rocket Gliders, including
trimming. HIGHLY RECOMMENDED.
Kevin McKiou's Basics of Design and
Trimming of B/G's and R/G's. Items 1 thru 5 are useful only if you
are designing your own, or modifying an existing plan/kit. Items 6 thru 9 are
useful for trimming gliders for optimum glide performance.
Again, Ed LaCroix's instructions
for the Maxima A Boost Glider has trimming tips.
Hand
Launch Glider trimming tips for beginners, from a British Free
Flight model airplane site. The latter portions about hard throws (necessary
for contest HL gliders) is not too relevant for rocket boosted gliders (since
the F/F HL glider fliers's hard upward throws are their equivalents to our
rocket "boosts"). Note the basic glide trim info and illustrations at
the top of the page.
Launching -
Set up the glider on the pad so that it faces into the wind. This means the
wing bottom faces upwind, and the wing top faces downwind. Actually the
dihedral effect will usually try to make the glider face that way.
Apply a flag of masking tape to the launch rod, so the
flag holds the model high enough for the glider tail to not be touching the
bottom of the launcher. Some people prefer to make their own glider launcher
that has the launch rod mounted onto a 3/8" or 1/2" dowel, so that
the whole rod can be used for guidance.
A classic launch problem is for the micro-clips to
fall at ignition to grab onto the glider wing or tail, causing damage or even
disaster. Some prefer to tape the clips to the rod so they can't fall, which is
effective but a bit messy. Others like to use an umbilical approach. They
arrange for a separate launch rod, dowel, or other structure to hold the micro
clip wires away from the glider, so when the clips fall they will not fall straight
down, but swing away in an arc from the glider. A simple umbilical is to use a
piece of 1/4 x 1/4 spruce 18" long or so, and cut the bottom at a very
sharp angle that is about 30 degrees from vertical. Then glue a launch lug to
the angled part. That way, the spruce umbilical can be slipped over the launch
rod, umbilical angled at 30 degrees from the rod, ready for the micro-clips to
be attached to it. Put your name on it, since the next person to use that pad
will probably want to remove your umbilical.
More Information:
- See
the RMR
Rocket Boosted Glider FAQ (Frequently Asked Questions). Scroll
down section 9.2 for free-flight RBG info.
- See
the "RocketBoostGliders"
Yahoogroup, which discusses Boost Gliders and Rocket Gliders.
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Engine recommendation
for B Rocket Glide: |
B4-2 (Most winged R/G designs needs low thrust and a
short delay) |
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B6-4
(Backslider Superroc type R/G's
only) |
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Model Plans & Kits |
Designer |
Notes |
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Nocturne
Slide-Wing R/G article (NAR website) |
Plan by Jeff Vincent, of ASTRE |
Competitive slide-wing plan. Article has a lot of
generally useful information beyond the plan itself. |
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Stiletto-B
Slide wing plan (pdf file) |
Plan by George Gassaway |
Competitive slide-wing plan |
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QCR - "Easy
Slide" slide wing and slide pod kit series by Ken Brown |
Kits by Ken Brown - QCR - Qualified
Competition Rockets |
Competitive kits. See QCR's website for the various
slide wing and slide pod designs they offer. |
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Future B R/G kit by Edmonds Aerospace |
Kit by Rob Edmonds - See notes at right |
Rob Edmonds is working up a B R/G kit for NARAM-46.
When it comes out, this page will be updated. |
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Xebec-B
auto-elevator plan (pdf file) |
Plan by George Gassaway |
Easy to build plan that can be a bit touchy on
boost. |
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XP-2
Swing Wing R/G plan (pdf file) NAR site |
Plan by Chris King, based on Al Nienast's design |
Swing wings are not as competitive as some other
designs. But if swing wings interest you more than the others, this is a good
one to build. |
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Plan by Bob & Peter Alway |
From their winning R&D report. Not a competitive
model, but the simplest to build R/G that there is. |
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Maxima
A B/G INSTRUCTIONS |
Great glider instructions by Ed LaCroix. |
The Maxima is not legal for R/G. But the
instructions are a must-read for how to build, fly, and trim any rocket
boosted glider |
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Last
Updated 7/8/04