
(Contributed - by Chan Stevens
- 07/21/06)
Brief:
Slightly misnamed, this is a boost glider, not strictly a rocket glider. It's a
standard boost pod configuration made from laser-cut parts with an easy to
build design.
Construction:
Parts were all good quality and the laser-cut work was very good with clean
cuts and only small areas needed to be finished off to free the parts. In the
surprisingly large bag I found:
- BT-56 (8") body tube
- Plastic nose cone with canopy
- BT-20 motor tube
- 20/56 centering rings
- Metal motor clip
- Balsa wing halves
- Balsa stabilizer halves
- Balsa rudder
- Balsa boom
- Streamer/rubber shock cord
- Peel n stick trim decals
Construction is fairly easy on this although is a bit time consuming. It is
rated a skill level 4 kit, however, I think that could be overstating the
complexity a bit. I wouldn't necessarily recommend this as a first glider, but
if you have any previous boost glider experience under your belt you'll find
this fairly easy.
Sunward's instructions are clearly written and include decent
illustrations, and if you're so inclined are written in both English and
French. Not knowing French, I find the duplication distracting and would rather
see them go the route that most instruction manuals take these days--written
start to finish in one language (English), followed by start to finish in a
second language.
The pod assembly is quick and easy work: slot the BT-20 motor tube, slip on
the motor hook, glue on a couple of centering rings, then glue the assembly
inside the larger pod tube. You'll finish it up by gluing on the launch lug and
a retainer assembly where the glider hook slips in during boost. I can
understand the efficiency of using Sunward's stock BT-56 tubing and nose cone,
but for this glider design, the larger/bulky pod tube is a bit of a weakness.
Most other boost gliders use minimum diameter tube in their pod design.
The glider construction is where the real work takes place. While there are
a few low-effort designs out there (any Edmonds kit, Quest QEZ glider, etc.),
most gliders involve a lot of sanding and hand work to properly airfoil the
flying surfaces. I spent a good hour progressing from 120 grit down to 400
grit, working the airfoil into my wings and stabilizer. For this design, only
the top surfaces are airfoiled.
The wing halves are designed to be mounted at an 18 degree dihedral. This
is a pretty detailed measure, and I think most builders would benefit by having
the math done for them by calling out the target height of the wing tip from a
flat surface instead of a .
After sanding, you can bond the wing halves, stabilizer halves, and rudder
to the boom. The instructions were not that clear, but if you pay careful
attention to the drawings, you'll see that the stabilizer is to be mounted flat
on top of the boom. I deviated a bit from the plan, and in order to build a
slight incidence into this (generating more lift), mounted them to the side of
the boom at a slight cant.
Construction wraps up with attaching the rubber shock cord via paper
tri-fold mount to the BT-56. (I'm not big fan of paper tri-fold, but noticed
this pattern appeared a little too small for the width of the supplied rubber.)
Finishing:
Gliders in general should not be painted. The header card for this one shows an
unfinished bird, trimmed with a couple red checkerboard pattern decals. That's
the scheme I went with, but you could also consider using a light thinned dope
on this or or even colored magic markers. If your glider goes
very high or far, coloring can aid quite a bit in tracking and recovery.
Construction Rating:
4
out of 5
Flight and Recovery:
The recommended motors for this are A2-2 (good luck finding those in the US),
B4-2, and B6-3 (or in the US, probably have to go with a -2).
Prior to flight, I spent an evening hand tossing and trimming the glider
for flight. After following the instructions for glider construction (with
noted slight deviation for stabilizer), I found my CG well aft of the wing aft
edge. As a general rule of thumb, the CG of a glider should be right at the CP,
which tends to be where the wing's airfoil is (roughly a third of the way back
from the front edge). I needed to add 5 BBs for nose weight before I could get
the glider to fly through a stall.
For the first flight, I opted for a B4-2. I got a very good boost, looping
a little during coast phase. At apogee, I got a clean transition and the glider
spun around into a decent glide for around 60-90 seconds although it still
showed a bit of a porpoise stall. I added a little clay and flew it a second
time, after switching to a B6-2. The B6 turned out to be too much thrust and I
lost one wing half during boost. The wings mounted at a dihedral angle are very
precariously bonded to my boom.
Having had to reattach the wing, I'll now be looking at more
trimming/adjusting, although based on the first flight, I would rate this a
pretty good glider.
Flight Rating:
4
out of 5
Summary:
I would rate this a 4 as a good boost glider although it's not exactly high
performance. It's heavy duty enough to handle winds of 6-8mph, so you don't
have to wait for one of those perfect weather days to fly.
Its main PROs are solid/stable design and it is fairly easy to build. It's
main CON would be the short, fat pod. I'd also consider changing to a pair of
tip dihedrals rather than a single wing center dihedral.
Overall Rating:
4
out of 5