quorneng
Master member
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.
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
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.
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.
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:
To this:
Less than 1mm.
The fin and tailplane were treated in the same way.
The broken fuselage was going to be an even bigger job.
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.
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
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.
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.
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:
To this:
Less than 1mm.
The fin and tailplane were treated in the same way.
The broken fuselage was going to be an even bigger job.
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