Lippisch P13a

Decoration largely complete.
all white except for black control surfaces and of of course the exhaust nozzle.
 
To make the underside look different the big nose skid is black.
 
If you can't see the nose skid then it must be inverted!
It weighs 374g ready to go. A bit more than the sub 350g I was hoping for but should still be ok.

Passably calm this morning so the Lippish had is maiden, well sort of.
It does fly but the gyro on the ailerons was much to sensitive so it oscillated in roll very rapidly. Otherwise it was flying more or less straight and level and fairly fast..
I decided to land ASAP to turn down the aileron gyro pot but with the violent roll oscillations it was not easy to control exactly its direction.
There is a rugby goal post on the field and, sods law, it clouted it rather hard.
 
The lightweight structure did not fare too well although the gyro did a good job of keeping it flying level despite the damage to do a soft 'pancake' landing with no further damage.
Fairly major disruption to the structure but should be quite repairable.
While I am at it I will give the elevons proper 'pin' hinges as I suspect some of the gyro wobble was made worse by some flexibility in the simple tape hinges.
An 8 second maiden and significant crash might be considered a failure but it was certainly not in the way I had expected.
Onward and upward!
  
 

I note high pressure is hovering close to the UK and it might actually end up right over the NW which equals no wind.
So I have pressed on with the repairs.
 
No new Depron added just all carefully straightened and glued back in place. It needed lots of masking tape to hold it in position until the glue dried.
I cannot guarantee the root wing section is now exactly the same but then with the bizarre Lippisch aerodynamics I doubt it will make any difference anyway.   
The elevons now have acetate pin hinges.
 
Much better!

Calm this morning, if a bit chilly, so I tried again
It actually flew for a full close by circuit, although perhaps "staggered round" would be a better description..
The Lippisch has rather unusual slow speed characteristics. Get near to the stall it roll wobbles but this is normal for a highly swept delta, but the nose does not drop automatically, it needs down elevator and more than the gyro gives to recover. Once speed is recovered its ok except it is very sensitive in pitch.
Not wishing to go through a stall cycles again I open the throttle to near full, all the flight so far was at about 75%, but the pitch sensitivity got worse and I was certainly not 3 mistakes high!

That nose intake makes a good plough! 
The sudden stop caused the battery to break free and crush the duct.
A view up the exhaust.
 
The ESC and the Rx were dislodged but as is usual everything still worked!
Given that the entire airframe was built up around the full 'one piece' EDF and duct I fear any repair is going to require some serious surgery.

But it did fly a bit more this time!

  
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I did think it was going to require major surgery!
 
About the only way I could envisage removing the EDF and replacing the damage duct was to simply cut off the top off the forward fuselage.
Getting the damged bit out no problem but getting the new bits back in not so much, let alone putting the fuselage back together!

After several hours of LW-PLA printing the new parts of the duct are fitted.
 
Not easy to glue it in through the formers.
Then the much reinforced battery box.
Finally glue back the cut off portions of the fuselage. It required much masking tape to hold it in position whilst the glue dries.
Complete - again!
 
Still high pressure so maybe the next calm morning.

Almost dead calm this morning at 9:30 so I made four short flight attempts. The really important bit is it came back undamaged. 
Even with a bit of lead taped onto the nose inlet it displayed considerable tail heaviness which even the gyro could not limit but each landing was a 'pancake' hence no damage.
After the fourth attempt I discovered the very act of hand launching it caused the battery to move backward!    Doh!
As the battery is counterbalancing the weight of the EDF right up front it does not take much movement to seriously upset a sensitive CoG.in a light weight delta. 
Positive battery restraint next.
 

It looked reasonable this morning, cold with only a mild breeze so I tried the Lippisch again with the battery in its new forward position.
Things did not go well. 
3 very short flights each ending in a distinct roll to the left. Once the wing touched the ground it 'planted' the nose into the grass. By the end the hose inlet was completely destroyed.
No problem a replacement is being printed as I type.
The final impact forced the left aileron up which appears to have stripped the servo gears. Quite some surgery required to replace it.

Of more concern is that the relatively small forward movement of the CofG (about 4 mm) seems to have completely changed its flight characteristics from staggering around at or near the stall to what looks like needing some serious speed to achieve reasonable control. In the short time before 'contact with the ground' it did not seem to respond much to any input I made and the gyro did not seem to be having much effect either although it was definitely on and working.
With a bit of foam I can always move the battery back to its original position.  
      

The aileron servo gears were indeed stripped so it was cut out and replaced.
Al tested and working. You can hardly see the repair.
 
No chance of suitable weather for quite a bit! Gales, snow then rain. 
 

Klippy
Certainly a possibility but with three impacts and the aileron sticks out beyond the wing tip, made me think it was that.
After the first impact I added a bit of right trim but despite my instinctive adding right aileron as it vered to the left it made no difference.
Did my moving the CofG forward require a flying speed  I never achieved?
I will set the battery back a bit for the next attempt.