Easy Fly ST330 RTF

I have acquired a second hand rather battered, incomplete (no motor, ESC, radio) 2m span Easy Fly ST330.

Why?
I wanted to compare the performance of a reasonable foam RTF against one of my own Depron designs, but oh dear!

The whole plane had been glassed and it certainly felt like it so I decided the first thing to do was to strip it off.

The glassed wing half weighs 8.5oz.
As originally intended 5.5oz.

A 'stock' ST330 with an 1800mAh 3s weighs 33oz. Mine is incomplete but I would guess it was well over 40.

Then we come onto the hinges. A test showed the rudder needed over 300gcm to achieve full deflection, the elevator was even worse and both used long snakes that required a further 100g force to actually move! :woohoo:

I hope I can do better than that!

I suppose this should really be on the "Crash (although I did not do it) and Rebuild thread.
It gets a bit worse. The wing joiner.

The bend is not dihedral it actually 'sweep forward' :woohoo: presumably resulting from a hard impact (the nose is badly crushed) from those grossly over weight glassed wings!
One of the carbon wing tubes is split as well.
This could take some time. :whistle:

As if the stiff hinges and snakes are not enough the ST330 uses 'linear' control surface horns.

Neat and stream lined but the movement is translated through 90 degrees by a sliding action of a pin on a 45 degree spiral.
All very clever but it is hard to imagine this action does not 'loose' say 10% of the applied force.

So in total:
The moulded hinge requires 300g from the 1cm servo horn for full deflection.
The snake another 100 to over come its friction
The linear action horn wastes 10%, another 40g.

The servo thus has generate 440g at the servo arm simply to move the surface to full deflection and any actual aerodynamic load has to added on top.

From my research of other forums the ST330 was judged to to be difficult to set up to fly properly and the control surfaces were noted for not centring properly.

I am not at all surprised! :huh:

The saga continues.
The aileron linkage.

I do not see the logic for using an inboard servo, a long snake and the 'linear' aileron horn unit with all the associated inefficiency when it can be replaced by a micro outboard servo with a conventional servo horn and a direct link that is capable of delivering just as much force at the aileron, for a lot less current and with better centring.
In addition the direct micro servo solution is much lighter.
The existing components weigh 21g.

The replacement even including the longer servo lead will weigh just 7!
A saving of 14g (per side) may not sound much but if the same principles can be applied through out the rebuild it should mount up.

But perhaps I'm just picky!

I have a ST Model Fox that has a similar setup on the wings. It does terrible rolls and the rudder is next to useless. I've been told that the poor roll rate isn't down to this setup, and the Fox isn't meant to be aerobatic :huh: what rubbish. I have some Corona slim servos I might add to the very slim wings, connected directly to the ailerons, just to prove him wrong. I bet you get yours sorted first Simon :blush:

Quorneng wrote: But perhaps I'm just picky!

No point in being in RC if you're not!

Talking about being picky, at the Ashbourne scale fly in yesterday there was a wonderful scale Tiger-moth.
The aluminium engine cowlings opened correctly and even had scale props to hold them open. The battery and ignition switches were of course in the cockpit. There is a picture of in the SmartMarty collection

Nice scale prop driven by a petrol motor that sounded quite realistic and it was flown with some verve BUT the Gipsy Major was unusual in that rotated clockwise.
I had to bite my lip not go over and say "nice plane - pity about the prop!" :whistle:

I knew Smarty liked it, there were lots of photos of it!

Now slowly progressing forward.
The LH wing with the its top hinged aileron.

Note the aileron droops under its own weight.
The trailing edges have small balsa extensions to reduce them from this:

4mm thick (pound coin) to this:

Just 1mm (5p coin)
The next big job is to rebuild the internal structure of each wing root to properly match the now straight wing joiner.

I just can't understand why they've done the linkages the way you've described... were they insane? .... Every linkage is supposed to present no load (Or very little) ... WTF Were they thinking of? :S

Remember Phil, this was before very thin wing servos were available, just another way of using engineering to get around a problem (and creating a few more in the process!)

Klipkopwildlife wrote: Remember Phil, this was before very thin wing servos were available, just another way of using engineering to get around a problem (and creating a few more in the process!)

I've never seen those linear horns before ... & I'm old enough to remember linear outputs on servo's. :silly:

To answer you question Pol I think the designer of the Easy Fly powered gliders was very proud of his linear horn and was determined to use them.

This is the rudder.

To simply reach the linear horn buried in the rudder the snake has to go round quite a sharp 90 degree bend. As a result the friction goes through the roof. :woohoo:
What is even more bizarre is the elevator uses a conventional horn with a straight snake run! :ohmy:

It is not as if the ST330 is that old. I think it was released in 2006/7.
The final insult to engineering logic is the original 9g aileron servo would easily fit inside the wing. :S

they are used a lot in scale models as you can hide everything under the skin.

As expected it is rather slow going.
This is the nylon mount for the fin and tailplane.

It alone weighs 7.2g more than the elevator servo I am going to use!
Of course in the original both the fin and tailplane had to be removable to go in its box but I will do without the mount altogether and simply glue the tail feathers on.

The first trial of the micro aileron servo fitted into the space occupied by the linear horn assembly.


The modified fin/rudder assembly.

It has the same balsa trailing edge extension as the wing but now the rudder is fixed. I have found differential ailerons adequate to counter adverse yaw and it saves the weight of a rudder servo. After all this plane is not exactly intended for knife edges!