Douglas X3 Stiletto

Yes but but a forward CofG reduces the tendency to stall.
Hopefully the resulting increase in speed will improve the elevator  effectiveness.
So far at every hand launch it has a tendency to instantly start to climb away without gaining speed resulting in an uncontrolled stall and that is with the elevator inline with the tail plane.
I would be happier if it started to sink after the launch and gain more speed.
Of course I may be wrong.
 

I hear what you say Simon, I'm just putting alternatives out there.

The Stiletto is all back together now with a "heavy" nose cone made of double wall PLA rather than one wall LW-PLA.
 
It even has 5g of lead in side it so 13g instead of the previous 3g.
The CofG is now even further forward.
 
Now worried it is too far forward but then I was worried about the previous change yet that proved inadequate.
I just have to accept that the long and relatively big forward fuselage when compared to the tiny wing will have a significant effect on the position of a workable CofG given a small RC model is expected to fly in regimes that the full size probably never did.    

Calm to day between significant showers so another go with the Stiletto with its forward CofG and reduced span ailerons. U also chickened out and removed the l4g pfead from the nose cone as I felt the forward movement in CofG was a bit too much .. 
Anyway it actually flew for 20 seconds more or less under control but the gyro was still struggling with the roll so I actually terminated the flight. More of an "arrival" than a landing as wing level on landing was a really just a matter of luck. 
I did think of trying again with the gyro off but decided I was unlikely to be able to do any better.
The next remedy is to turn the roll gyro gain down a bit and move the aileron linkage in two holes on the servo arms.
 
At the same time I have turned the elevator gyro gain up a bit.
Weather forecast is for yet more sharp showers as if the field was not still wet and squelchy enough. .
 

At least you seem to be getting somewhere now. I hope.

Still calm this morning so I tried again. It flew for a whole minute and I achieved an almost a proper landing. Still not perfect but better
With the gyro it can fly at an unrealistic high alpha quite slowly but when the nose goes down it goes FAST!
Not happy with the elevator. It needs a bit of TLC to restore it to its proper stiffness and travel..
I will also paint the wing undersides black.
With such small wings and all white it is not easy to detect if it banked towards you or away. With its ridiculous roll rate get it wrong and its inverted. 
I had a similar problem with the winged V2 and that has 50% bigger wings coupled with a more reasonable roll rate.    .  

Still calm this afternoon so I flew the Hawker P1152 (Swept wing Sea Hawk).
 
Still flies very well. Managed 5:20 which is not bad for a EDF and particularly one with only a 1500mAh 3s. It represent an average of 18A over the flight.
It remained calm do I flew the Stiletto again. Managed 1:20 before its rather wayward characteristics got the better of me with an unintended rather hard arrival.
Unfortunately the "heavy"  PLA nose cone proved indestructible which resulted in some rather serious "compression" damage  further down the fuselage.
 
The abrupt stop also caused the battery to move forward through the battery box.
It is all easy enough to fix.
I am sure it still needs a bit more nose weight so I will return to a crushable LW-PLA nose cone but with nose weight added inside its very nose to bring it up to 12g all up...  
 

Repairs underway. First a cut back
 
Then start putting them back.
 
The battery box has been extended and refitted to allow the battery to go about 8mm further forward.
With the underside "stabilised" the top compression damage areas are cut away.
 
Should be complete in a couple of days but no rush as its going to rain quite a bit more over the next 6 days. 

Just to add to the misery I note than my water bill has virtually doubled over the last 5 years! 

 

Now all put back together.
 
The nose cone is LW-PLA and it has a nose compartment that has a 6 grams of lead shot in it. The access hole is just taped over so more can be added. It is now 4g heavier than the previous heavy PLA nose cone. In addition the battery is 8mm further forward. Hopefully this will have moved the CofG forward enough for a "reasonable" flight.
No idea when the next calm(ish) day will arrive!  

Pretty calm this morning so another go!
2:15 this time. I was just about to organise a landing but as I slowed down just a bit control got difficult so the crushable nose cone had to do its job.
 
It went in pretty firmly with no significant ground slide as the grass is far to long for that! Note the completely crumpled LW-PLA nose cone with relatively minor local fuselage damage and more important no compression damage either.
The Stiletto does seem to have an issue. At slow speed it is still flies tail heavy tend it go into a high alpha stall almost beyond the capability of "down" elevator but once the speed builds it goes into a fast dive but the response with up elevator is pretty marginal. All a bit alarming as the ground approaches fast. 
It is this characteristic that caused me to slow down to the intended  landing. Maybe that was a mistake. 
I am beginning to suspect the stiffness of the tail plane and/or the elevator when at higher speeds so I am reluctant to add more nose weight to cure the slow speed pitch up.
The full size I believe had an all moving tail plane but I don't think I want to go that far so next will be a new stiffer tail plane and elevator with carbon reinforcing. Also maybe a slightly bigger servo.
Still calm so I will go and fly something else.          

Despite being all repaired, the tail plane reinforced and its battery fully charged it did not fly today as the home control check revealed that the elevator servo only worked intermittently so it will have to be replaced..
Not pretty but this is the tail plane reinforcement. Thin strips of carbon fibre tow glued to the top and bottom surfaces.
 
It certainly works.  .
The elevator servo replacement is a tedious cut out job with some very tricky soldering of the 32AWG servo leads due to the limited limited access.
The new servo in and tested.
attachment=29034]NewElevServo.JPG[/attachment]
As it has turned out it is not nearly as calm as it was yesterday so the glue will have time to dry however it should improve a bit later in the week when high pressure is due to "centre" over the UK.
We shall see!  

Calm enough this afternoon so three short flights each of 45 seconds with 3 landing and no damage!. I stopped as I was not sure my luck or my heart would hold for any more.
It is still a real handful to fly.
It needs full power to get up to speed from even a firm hand launch but it then gets very sensitive and tends to dive. I am reluctant to add any nose up trim for as soon. as you throttle back even slightly it starts to climb all by itself. It you don't keep the nose down it just climbs more and more until it stops flying. It actually flies quite reasonably at a slightly reduced throttle but so far I am reluctant to trim for this condition as the trim will then be even further out at the full power launch.
If it wasn't so "twitchy" I would consider a throttle/elevator mix but the degree of mix has to set by trial and error one flight at a time. So far I am not confident I could undertake such flights without crashing.
Tomorrow is due to be calm.         

 

Obviously, I've not seen it fly - but from the description, I'd suggest that you are getting a lot of lift off the fuselage, and the centre of lift is moving about a lot with the varied A o A - or all that forward fus could be blanking the tailplane, especially if it is 'fishtailing' a bit.

Eric
 am sure you are right about fuselage lift and variations in the effective centre of pressure depending on the angle of attack.
The CofG is ridiculously far forward as marked by the white spots.
 
I suspect the situation is made worse by the fact the relatively flat underside of the fuselage is truncated at the twin exhausts.
 
The lift created by the fuselage aft of the exhausts is likely to be minimal compared to that forward of them
I am sure it will come down to finding a CofG compromise and possibly decalage angle that allows normal type RC flying which of course the full size was not required to do.  

At 6 pm the gusts died down so yet another try with the Stiletto. Still difficult to control reliably so the second flight resulted in another crushed nose. 
 
It was quite a hard impact so the battery broke free through the front of the battery box.
I extracted the battery, it had already pulled the Deans apart, so I put it down whilst I picked up the few loose pieces of Depron. I then picked up the Stiletto and transmitter and walked back to the car. You guessed it I had left the LiPo in the grass. Doh!
I went back and searched but I simply could not find in the very long grass. It has not been cut at all this year as the ground has been too soft for the council tractor!
Never mind the repairs to the Stiletto the loss of its 1400mAh 4s has made it a seriously expensive trip. Of course the bit that really annoys is it is entirely my own fault.
I may go back and have another look tomorrow but the grass is so long and tufted I am only likely to spot it if I virtually tread on it.