Written by: Bill
Only change since initial setup presented bellow is 480Ls instead of 6V S400s, same 8x2400 and CAM
This is a very early "mark 1" kit. The current TJ has some
slight airframe differences . ... the wing is thicker (filled in) between
the motor nacelles and the top of the fuselage, and the servo bays are
slightly closer to the hinge line.
The present "standard" and "racer" TJ airframes come out
of the same mould so are identical to each other apart from the color.
I'm using 8x2400s with the
stock 6v S400s. My mods. are:
1. CAM 5.5x4.3 props
2. Tape hinged elevons
3. Air inlet under front edge of canopy (like Twin Star)
4. Hollowed out rear fus. to let air flow straight through and out at the back
5. Elevons bent flat (to remove reflex) - Jurgen's idea
6. Clear tape to protect fus. underside
7. Some USAF decals etc. from scrap box
Initial Review. Extract from Ezone Thread - Click
to read the full thread
All up weight is 42.0 oz, which is 10.5 oz over the quoted weight. my 8x2400s
(instead of 7x1700s) account for 2.9 oz of that, the CAM props and adapters 1.5
oz at most ... your guess is as good as mine where the other 6 oz came from!
The control throws are exactly as stated in the instructions, I needed the
outermost hole on the servo arms and second innermost on the elevon horns to get
this. I'm using exactly the same mixer/throw settings on the TX as for my PJ,
which is handy!
OK, now the good bit. This model is very impressive, I flew it at three IC sites
over the weekend and the immediate reaction from most people was "I gotta
get one of those"!
With the flattened elevons I have moved the CG back slightly so it balances just
behind the bumps under the wing (with fingers just touching them). In flight it
needs a little down trim (the thickness of the TE, maybe 2 or 3 mm) but there is
no trim change between power on and off, so the standard thrust line is fine.
With this setup the model is fast, smooth, and stable. Low fast passes are a
breeze ... no "zooming". This model looks and sounds superb on a fast,
low pass. I use some up trim for solo launching - with this the model just pulls
out of your hand and climbs out. I reset the trim to neutral on climb out.
Inverted is rock steady, needs some 'down' held in (as you would expect) but
flies inverted circuits and low passes with no problem. However, it will not do
an outside loop, I think when pitching to higher angles of attack inverted the
airflow breaks away at the rear of the wing and the elevons lose effectiveness.
Roll rate is excellent - at speed (and the model is fast) I would estimate 2.5
rolls per second on full stick deflection. But it is not too sensitive for
general flying - no exponential or dual rates are required. Pitch response is
fine, but not so sharp as roll. Loops, reversals, immelmans, etc. are no
Slow speed handling is superb, there is no real stall and tight turns are
completely safe. I was flying circles and figure eights at low speed just above
the ground ... the ability to fly well both fast and slow was one of the things
that people were most impressed with. It doesn't drop the nose in slow turns
like my PJ does - feels really well sorted.
I managed to get the model to spin - pull sharply nose up, then just as it runs
out of speed apply full up and left (or right). Because of the mixing one elevon
goes fully up (45 degrees plus) while the other is neutral. If you time it just
right the sudden drag on one side causes enough yaw to pull it into a spin!
Couldn't get a stall turn though.
The glide is steeper than the PJ, and more height is lost in turns. This is a
good thing as you can lose a little height without picking up too much speed.
Landings are not too fast, it slows up well when you flare.
At the IC sites I had the timer set to 8 mins and didn't hit BEC cutoff. The
packs came out only slightly warm - exactly the same setup (motors/cells/props)
in the Twin Star caused them to get pretty hot ... that model wasn't fast enough
to let the props unload in flight (too much pitch).
As you would expect, the TJ handles wind and turbulence well (better than the PJ).
The standard battery retention works well and seems completely secure, though
it's a little fiddly getting the rubber band around the pack (I use a length of
3/16" dowel to pick up the band once the pack is in). You also need to
slide the pack in with the model inverted .. otherwise it sticks on the velcro.
In summary, this is a great model, particularly with the elevons bent flat to
reduce the reflex a little. There are a few QA problems - like the supplied
elevon pushrods being too short - that Multiplex need to sort out (if they
haven't already), and my personal view is that the standard "foam plus
tape" hinges are too stiff.
I just bent the elevons flat
using my fingers & thumbs. I had already cut them off in order to re-hinge
with tape top & bottom, but you could probably do it with them still
attached. Don't just bend the extreme TE down, you need to take the whole upward
curve out of the elevon. That foam is pretty tough, if you've got any offcuts
lying around, try snapping or tearing them!
If you go with tape hinges, make sure you clean the foam up first. Meths is
completely safe for this. I experimented with masking tape first, and couldn't
get it to stick to the foam at all until I'd cleaned the surface! So far the
tape hinges are staying put, I will use cyano if they do start to lift.
The Gunther and CAM props both have the same stated pitch (110 mm) and are
probably similar in performance on this model. However I think the CAMs are
slightly more efficient .. the blades are rigid and don't flex like the Gunther
ones. They are also a little quieter as they are further from the wing and fin
TEs (due to the prop adapters). The Gunthers are very light (and free!) though.
The howl they make sounds great at an IC site, but not so good in a local park.
The CAMs still sound pretty good, a club member came rushing up from the car
park yesterday to see what was being flown!
I think the motor cooling can be improved, to start with I opened up the
intakes a little ... the rim around each is very thick, so I carved the foam
away to streamline the airflow and let more in.
I also intend to try covering the open bottom of each motor cutout with a flat
plate. This would force the cooling air to flow along /through the motor and
exit at the rear. I suspect that a lot just spills out downwards at the moment.
However the heat will dissipate quicker on the ground with the motor bays left
I spent 5 minutes flexing the foam hinges back and forward but the servos still
stalled at full throw ... too stiff for me (just personal preference)!
One small thing I forgot to mention in the original post, on anything other than
smooth grass the elevon horns were picking up a lot of debris .. so were
obviously contacting the ground on landing. To avoid shock-loading the servos
(and hinges) I trimmed the horns back to the pushrods (I wasn't using the
outermost 2 holes). Of course this also reduces weight and drag and so makes the
model fly faster