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EasyFly ST330

#1
some weeks ago I acquired the 'bones' (Broken and no motor, radio or battery!) of an Easyfly ST330.
Why on earth do this?
Well I wanted to see how well (or not!) a foamy 2m job performed when compared to my 2m built up Depron equivalent.
My first reaction was it was incredibly heavy as it had been 'glassed' over all. Fortunately the glass had not stuck particularly well to the EPO foam so it was not to hard to get it all off. The weight came down by 8oz!
Next the control surfaces (even the ailerons) are moved by long snakes coupled to what I can only describe as 'linear actuator horns'. Very clever but mechanically not the most efficient way of doing things.
HingeHorn.jpg
When coupled with a snake and the stiff 'pinched down' EPO foam hinge line the poor 9g servo had to work very hard to simply move the control surface to full deflection.
The aileron linkage components
AileronLink2.JPG
I work on the principle that with a good mechanical linkage and hinge a much smaller servo is perfectly adequate. In fact the 3.7g micro servo I used weighs the same as just the linear horn! The old stiff hinge was cut away and the aileron modified to use a simple top 'tape' hinge.
AileronMicro.JPG
The same treatment was applied to the elevator with the servo mounted in the fuselage under the tailplane.
With strong differential aileron movement I have found that "bank and yank" (no rudder) control is quite adequate so the rudder was fixed directly to the fin.
FixedFin.JPG
The fin and tailplane were glued directly to the fuselage saving the weight of the original nylon mount.
All together these changes saved a further 2oz and probably gave a better control response than the original set up.
The next issue was the 'thick' wing trailing edge. It probably does not effect the lift that much but it does increase the drag, particularly at speed so balsa trailing edge extensions were added taking the edge from this:
LHWingOrig.JPG
To this:
RHWingTE2.JPG
Less than 1mm.
The fin and tailplane were treated in the same way.
The broken fuselage was going to be an even bigger job.
 
Last edited:

colorex

Rotor Riot!
Mentor
#2
Cool - the trailing edge on the Bixler is about 2 mm, doesn't cause that much trouble. If they make the foam thinner it will dent and break more easily.
 
#3
The fuselage nose section was broken in two places.
CpitUnder.JPG
It was also crushed on the left side.
CpitCrush.JPG
By mounting all the servos next to their control surfaces only the battery, ESC and radio would be in the cockpit so all the moulded cut outs could be filled to improve the strength.
CpitInside.JPG
The new cockpit with a flush floor and extra Depron added to the side walls.
CpitNew.JPG
The sides were also built up to a new sill line to give a deeper stronger cockpit.
CpitSill.JPG
The chosen 220W motor was front mounted so the nose was extended with 6mm Depron sheet 'rings' ending in a substantial 6 ply mount.
DownThrust.JPG
Done like this the motor can be inserted (and removed) through the cockpit.
MtrMount2.JPG
The original canopy was missing so a new hollow one was 'built up' using 3 mm Depron planks.
Canopy1.JPG
It was finished in my house colours of white (spray acrylic) with red control surfaces.
Complete1.JPG
With a 12x6 prop it draws 200W static. With its more powerful motor, bigger prop and 3oz lighter than 'stock' it has a near vertical performance at full power.
The low flying in this video was for the benefit of the camera.
[video=vimeo;53591661]https://vimeo.com/53591661[/video]
It is easy to fly and considering it has no rudder remarkably manoeuvrable. It glides pretty well too!
 
Last edited:

colorex

Rotor Riot!
Mentor
#4
You have some amazing skills... You completely rebuilt the whole nose, now it looks like new! You have my respect, Sir!
 
#7
This is what I am comparing the ST330 to.
BigComplt.JPG
The same span (2m), a pusher, built almost entirely of Depron, it weighs just 23oz (The ST330 is 30) and that's with twice the battery capacity (3000mAh instead of 1500)!
An early test flight, ROG with no undercarriage. Notice how the prop wash twists the tail feathers!
[video=vimeo;45850507]https://vimeo.com/45850507[/video]
Not surprisingly it has a quite a performance. Near vertical it could keep up for 6 minutes (just how high would that be?) and a cruising power endurance of over an hour (longest to date 1hr 11minutes).

ST330 will never be in that league but it nevertheless is still quite nice to fly.