Seagull EP Edge 540 - help please!

[Romeo Whisky]

My favourite model for the past two years has been my Seagull EP Extra 300, so I was most upset when I shredded it through a poplar tree earlier in the season.

Knowing that this model was discontinued (why???), I decided immediately to buy its sibling (replacement?) the EP Edge 540, which although it looks very similar externally, is designed very differently in many respects (with not one of the changes being for the better in my view).

Whereas the Extra was a delight to fly, the Edge is a pig.  Although it balances correctly in the workshop at the specified CG point (which is significantly further back compared to the Extra), it flies incredibly nose-heavy and needs loads of up-elevator trim to fly straight and level under power, but dips its nose as soon as power is taken off for landing, and lands heavily.

I am wary of balancing it to a CG even further back is it already seems a long way back compared to the Extra.  There is virtually no downthrust on the motor mount.  The ailerons are both set correctly to neutral and because of the trim setting the elevators are already slightly raised at the stick-neutral position.

 

This photo shows its marked CG (wing-tip) and motor thrust angle very well  ...

 

... so I am baffled and frustrated, and would welcome any input or ideas, and would especially appreciate to hear of the experiences of anyone else who has this particular model.

[Chris Card]

Have you tried flying power off to see if the nose heavy tendancy is still there?  If it isn't, then possibly a thrust line issue pushing the nose down on power?

[Vecchio Austriaco]

I had this model, it was very easy to fly and quite neutral, the CoG given in the instructions was correct, I suffered rather from being tail heavy. But this comes from engine size / battery size / the 3 tail servos used. Even using 3 cells 3300mAh I had to put a good quantity of lead to the front of the plane.

 

The thrust angle was fine, I didnt change anything.

 

brandnew at the field in Camparada, 2008

 

After a major repair, now with painted landing gear and pilot

 

Dezember 2009 - a few weeks before I crashed it at the field of ALA Lecco in Oggiono

The only thing I didnt like was the landing gear - I changed it to a strip dur aluminium version.

 

And as I found the plane 2 weeks ago at the NATs I replaced it - I just have to get the necessary servos, esc and motor from my old house in Italy and I think end of October - if the English weather has mercy with me - it will fly in the sky of the Midlands.

 

VA

[DH 82A]

  It may be the camera angle, but looking closely at the tailplane, it seems to have a slight positive angle to the wing, which would give a nosedown trim, power on or off.

 

  If not this, Iwould try moving the C.G. back in very small steps, flight testing each time.

[Romeo Whisky]

Thanks guys.  Like Vecchio I had had to put a ton of lead in the nose to balance it, even using relatively heavy LiFePO4 packs (205g).  So as Rex suggested I have progressively removed lead from the nose, pushing the CG back in small increments with test flights at each stage.   After removing about 50g of lead from the nose (25g remaining), the CG point is now virtually on the leading edge of the aileron, and I still need several clicks of up-elevator trim.  She also has a steep approach angle for landing as the airspeed reduces, and lands very heavily compared to my much-loved but sadly deceased Extra 300, putting great strain on the u/cart.

 

A friend suggested flying inverted to see if the issue is really nose-heaviness or an incidence issue with wing or tailplane.  Strangely, although inverted flying is not something I have fully mastered, it seemed to fly hands-off better inverted than right-side-up.  But I'm not really sure what this is telling me.

 

It is less of a pig to fly with the CG further back, but I still don't feel it's properly "sorted" yet.

[DH 82A]

 

Flying better inverted certainly seems to indicate a misalignment between wing and tailplane.  When you say the balance point is on the leading edge of the aileron, I take it you mean at the wingtip?    I would not go any further back, at the moment.

 

   Try laying a straight edge on the tailplane,  extending over the wing, then measure the distance from straightedge to the trailing edge of wing, then from straight edge to centre of leading edge of wing.   The distances shoulbe the same, OR  the leading edge distance should be slightly kess.

 

    

[Romeo Whisky]

Thanks Rex.  Yes, the CG for this model is specified in the manual as at the wingtip.

 

Apart from the overall incidence of wing and tailplane it has occurred to me that the neautral point of the ailerons might be an issue.  It is very easy to ensure that the elevator and tailplane are perfectly aligned, but with a symmetrical wing and full length ailerons it is much less easy to know if they are correctly set at neautral since there is no datum point.

I have wondered if both ailerons might be lowered slightly at the neutral point, but  they look right end on.  Would it be worth adjusting them both upwards slightly.

 

On the other hand you would expect incidence issues to get worse as airspeed is increased, and this would not account for the nose-heavy landing approach when the airspeed reduces.

[DH 82A]

   Yes, you could try raising the ailerons slightly, but remember that will reduce the lift of the wing to some extent, so making the nosedown effect worse.

 You say the nosedown gets worse as speed reduces, do you have much up elevator movement ?   If not , that  would stop you getting the tail down for landing. Try increasing the movement a few degrees, again flight testing.  Beware, though, of giving too much up at landing as this type of  aerobat can" bite" at low speed.