Multiplex Gemini Build

I collected my Gemini from Galaxy Models on the way home on a Monday afternoon.   It had it's maiden flight the following Saturday.  Here are a few pictures that I took during the build.  It's not a full "build log" because there wasn't really a lot to do.

Still in the boxEven the packaging is quite impressive.  I took the time to unpack everything and check it off against the parts list.  Nothing was missing and it helps to know what every thing is so that you don't start putting the wrong bits together !

Servo in fuzelarge
I had purchased four Hitec HS-55s to use in this model.  They are slightly larger than the MPX parts,  so the mounting holes in the fuzelarge needed to me extended backwards by a small amount.  The picture shows where I cut away the foam.

Glued in placeOnce the control rods and snakes were installed the servos were secured in place using hot glue.  Using the  outermost hole on the servo arms  means the rod lines up correctly and the throws are about right.

Here's a tip:   Don't glue the snakes in too near the ends of the slot in the fuzelarge as the need to move a little as the servo arm turns.  This is more important at the tail end of the snakes.  Also it reduces the risk of gluing the inner and outer tubes together, or worse still gluing the rod into the snakes.

Tailwheel in viceThe manual was not very helpful when it came to putting the tail wheel assembly together.  The  part of the  wire  sticking  up  has to be bent into shape such that it lies  in the  position of its  shadow in the picture.   The manual  says to use "a pair of combination pliers" but I couldn't see how to do this without putting stress on the plastic parts in the process.
Bending the rodIn the end I realised I could put it in the vice the other way up, and use the 5-7mm of wire that is needed below the bracket to cover the depth of the vice jaw while bending the wire to shape.

Slot in the rudderWith the hinge and bracket glued in place I cut a slot for the wire as described in the manual.

CLose up of rudder slotIn the manual it says "glue the wire into the rudder using plenty of cyano.  Well I tried this, but since cyano isn't a "space filling" glue it didn't seem very secure to me.

Extra fillerSo I cut out a small piece from some spare foam and glued it in place to fill the rest of the slot.  I've outlined the extra piece in the picture.  The excess was trimmed off after the glue had set.

The upper wing spportThe cabane parts after gluing.  With any of the parts where there is a slot into which another part fits,  don't put glue on the sides as it will "grip" before you get the parts fully together.  Put plenty of glue in the bottom of the slot so that as the parts come right together it will be forced up the sides of the joint.

When installing the tail section it is also important to consider which parts come into contact first and which parts need to slide over each other before the final position is reached.  If you put glue on these parts it will grip before you get the parts fully together (I know because this happened to me when putting the elevators into my Twinstar II.  I didn't make the same mistake this time). 

Assembled wings
The wings, cabane and wing struts all  glued together.
Bottom of the wings
The aileron linkages are quite fiddly to get together.  Unlike the servo mounts in the fuzelarge sides, the aileron mounts did not require any adjustments.
FIrst test assembly
Here it is all put together for the first time.
Balsa mount for the ESCThe manual says to install the ESC behind the  motor "suspended on its cables", but I decided to provide a firm mount to stop it moving about in flight.  I cut a small strip of balsa to size and glued it to the motor mounts in the sides of the fuzelarge.  The ESC is held in place on the mount with velcro.

Bottom view
The final thing to do was to add the transfers.  The manual says this should be done before the major parts are glued together, but I was impatient to get it built.  The only parts that would be difficult to do are the inner surfaces of the wings, so mine have remained undecorated.
Side view

Head on view

Ready to take off
So, by the following Saturday it was all ready to go.  The last thing to do was to set up the servo throws and exponentials on my transmitter.  I set these all to the values in the manual.

With a Thunder Power Prolite TP-2100 pack fitted, and a ferrite ring on the ESC lead, and the Futaba receiver fitted  on the top of the lower wing, the CofG came out 20mm behind the spar in the top wing.  The manual suggests 75mm back from the  "nose" of the top wing which would be on the spar, so mine is a little bit to the rear of that point. 

Post maiden flight adjustments

The maiden flight was a little bit stressful because I seemed to have set the elevator linkage with the servo  NOT in it's neutral position.  As a result it need all the nose down trim my transmitter had and a bit more besides.  But I got it round a couple of circuits and managed a reasonable landing.

So post flight I reset the linkage and reset the transmitter trim.  On the second flight it became obvious that some down thrust was needed on the motor mount.  The design of the mount makes this adjustment very easy.  1) Remove spinner and prop. 2) loosen of the middle bolts on each side.  3) Turn top bolts on each side in one turn and the bottom bolts out half a turn.  4) Tighten the middle bolts and refit the prop and spinner.

The third flight was much better but it was still climbing when the throttle was opened, so a further half turn in was added to the top motor mount bolts.

By now I was confident enough to ask  someone to use my camera to get some video of the Gemini in action