Douglas X3 Stiletto

I am sure almost any club would raise more than an eyebrow at such a fine point nose no matter how delicate it was. No problem for me though as I fly and crash alone. To "club" fly I suspect the spike would have to inter changeable with a blunt nose,

Holding it by the finger holes it doesn't "feel" like it would be too hard to give it 'flick' shove so it may be ok but the CoG will have to pretty nearly exactly right to give it much chance of just accelerating away flying flat with little or no control input. On this maiden the gyro will earn its keep!   

Just in case it does fly I have decided to actually build interchangeable noses.
 
They will be held in place with short pegs and magnets.
It will required the X-3 nose section to be slightly "reprofiled" to match the scale cross section of the two noses.
My intention is the long nose will be for "show" only. I doubt the magnets will be strong enough to withstand the aerodynamic forces from any yaw asymmetry on such a long nose. 

After raining on & off most of the morning at 3 pm the sun came out and more to the point there was virtually no wind so the Stiletto had its maiden actually two of them!
Total time 21 seconds. Minor damage on the first rather more on the second.
 
As you can tell from the damage the flight ended "taking out" the right hand side.
However the flight were long enough to confirm what was wrong. It is tail heavy and the elevator is pretty ineffective except at speed.
As I feared the CoG has to be pretty well spot on. Even a touch tail heavy and it simply tries to climb and with limited thrust it cannot accelerate so the pitch up just gets worse. With no airflow over the tail plane the elevator has no effect.
On the second flight some down elevator on launch delayed the rate of pitch up so it got higher before it stalled from near vertical. In the resulting dive the elevator only had any effect rather too late.
So a lack of thrust was not the problem, both hand launches went well, but simply being a bit tail heavy. From my experience with the Bachem Natter that "fuselage lift" can require a rather extreme forward CofG for stable flight.
Still so far so good. It could have been a lot worse.

  

Interesting variable dihedral on the tailplane! It looks a bit like my thumb felt, the other day! 

Made a start repairing the RH inlet and glued the RH wing back on.
 
but in the coarse of testing it appears than when the RH wing was ripped off the aileron link striped a tooth on the servo.
It will not be a simple job to extract it.
I do have a spare electrically dead servo with a good gear train but changing the gear wheels on a 3.7 g servo is a very questionable process.
Its all good fun!

  

Now all fixed and ready to go.
 
The battery has been repositioned a bit further forward and to the left to counter the weight of the ESC on the right.
 
The previous and revised CofG positions are shown.
By my "trapezoidal" calculations this represent a CofG at 23%​​ effective chord. I have also removed the aileron droop which should reduce the nose up pitch,
I half expect the CofG will need to go a bit further forward however it is relatively easy to adjust things to allow the battery slide further forward.
We shall see once the wind dies down but that is not likely until after Easter according to the forecast!  ​​​​

The two noses are now held on with small magnets.
The long nose. It is an all printed structure.
 
The long nose is not flight worthy as the magnets are not strong enough to withstand the likely aerodynamic loads. It is only for show. 
If the X-3 proves to fly reliably then in the privacy of my field I could tape it on securely just to prove it can fly (and land!) with it on.

To recap the result of yesterdays flight attempt.
 
First operation as always is to cut back to an undamaged area.
 
It is always a bit alarming as you seem to throw away what may have been damaged but was still a pristine bit of a plane.
The hole in the former was added simply to get out some loose bit that were trapped in the fuselage.
A start of the new nose.
 
Although tedious it is one advantage of this type of construction. Although originally the nose was built as part of the rest of the fuselage the new nose will be made in exactly the same way as the original thus will be the same weight and strength. It just takes time!
 

The first half planking is now complete so on with the other side. Once the RH side of the formers are added the planking can start again.
 
It is rather slow going as to avoid any distortion it is important to let the glue dry after a few planks are pinned in place.
Once the nose is complete things should move a bit faster as it is really only a "fairing" and plays no part in the structural integrity of the airframe.
It does however have to fit the existing fuselage neatly!   

New nose completed and glued on with the replacement printed short nose.
 
The battery box has been extended by nearly 2 inches/
 
This should place the CofG to give manageable flight characteristics, 
 

I discovered that the existing full nose did not properly fit the rebuilt fuselage nose and it was overall 75 mm too short!
So it needs a new one to be printed.
Last time each section joint had 3mm Depron former made to fit. This time I wanted to print the joining formers as well.
However first a video of the "silly" tall print of the first 140mm of the nose.  The new nose so far printed and positioned correctly against the old nose to show the extra length.
 
The really tricky bit is the existing nose of the fuselage will require to be "adjustment" to get a smooth transition to the long nose but that will have to wait until either the X3 has made an successful & undamaged maiden or the nose has to be rebuilt anyway! 

Pretty calm this morning so out came the Stiletto for another try.
It does actually fly a bit better but the roll is much too sensitive. Even the gyro was struggling rocking from side to side.
The net result was it climbed high enough to get to tree height but the lack of effective control prevented me from flying into it. 
Just managed to get it down with my 7m roach pole but it was still quite a drop through bare branches. 
 
Big hole in the side, the tail plane will likely have to be replaced along with a new nose cone but none of the EDF duct is damaged. All easy enough to repair.
It will have to consider the best way to reduce the aileron sensitivity.
The CG needs to go a bit further forward as well. To avoid further fuselage remodelling to move the battery any further forward it will be a simple nose weight ..
I actually consider today's flight to be a modest success as it didn't damage itself by flying into the ground.

Sounds like my old Concorde model - almost no pitch control, but rolled like a drill-bit! 

First job on the repair is to square off the big hole to the appropriate plank.
 
Big but it just did not go deep enough to damage the inlet duct.
The tail plane has be glued back together.
 
Not quite square to the wing  but as the wing was structurally undamaged as was the inner part of the RH tail plane I fear it never was!
Now just the holes to fill!

Surely moving the CoG further forward will have the effect of reducing the elevator effectiveness?