An RC Depron Douglas X3 Stiletto

[J D 8 - Moderator]

    Coming on to Bills post above I to have had an interest in early experimental jet era.

     Although the X3 did not achieve its aim of mach 2 flight it did revile other issues with high speed flight, a problem that was affecting early versions of the F84 and F86 with in flight break up.

  We have all heard of the yaw roll effect but what was found with the X3 was roll inertial yaw effect.

   A fast roll at high speed would result in a sudden yaw due to the mass of the aircraft body being rotated quickly.  It was only because the X3 had been built with titanium in high stress areas [ the first aircraft use] the problem was found. Fix for F84, F86 was increase wingspan and or increase tail area.

 

[Simon Chaddock]

Yes indeed

If the X-3 was a delta I would have less concern about the ability to keep the nose high during the flare, deltas do it it easily in combination with the ground effect, but the X-3 is very different. I would expect it will not have the elevator authority or the thrust to weight to be able to hold an exaggerated AoA. With a full length nose I suspect the actual landing will have to be a compromise between the speed needed to keep the nose even slightly above horizontal and the risk of damage to nose from the resulting long(ish) grass ground run.

[Richard Harris]

Simon,

 

Brave project.

 

Could you not increase the wing size, get it flying then slowly reduce the area down to its true scale?

[Bill Southwell]

     Hi Simon,

 

    The long nose does put the most fragile part of the plane in the worst spot. What If you make the nose able to break away via small magnets?  That may help mitigate some mutilation from it being a belly slider. That and the fabled field of soft, long, tall grass.

 

   The CG will be critical in helping with the pitch authority. A nose heavy condition would not be helpful and would be the thing to reduce or eliminate the elevator authority.  If you can balance it closer to the tail heavy ,but not beyond, limit you will gain more authority. I have had airframes that were horrible, hard to land, snap happy beasts until I tried an aft limit CG. The lack of slow speed control and snappish elevator response was gone and the former terror of an airplane became a hanger favorite. The small tail surfaces will need as much help as possible. The trick is to get close but not beyond the point of no return. Preaching to the choir I am sure.

 

My hat is off to you. You definitely know how to pick a real challenge. 

 

Best Regards

Bill,

Iuka, MS

[Bill Southwell]

      I have not researched as to what type of horizontal stabilizer the X3 has but the tiny trim tabs at the stabs trailing edge in the 3-views and looking at the photos it looks like it may have had a stabilator and not a stab/elevator set up. If it is a flying stab you would have a lot more pitch power without having to worry about the two part stabilizer stalling due to larger elevator travel causing air flow separation and loss of pitch control. I apologize for my ignorance on the stab type but I did not remember it being talked about and is a forgone issue already. 

 

Best Regards,

Bill

[Futura57]

I just came across this 

and thought it was vaguely comparable. Probably double your wing area though 🤔

[Simon Chaddock]

I had seen it but very impressive.

I wonder if it survived that "very long grass" landing completely undamaged. 

[Simon Chaddock]

With the wing and nose in place the rear end now looks quite Stiletto(ish).

  

But include the nose and it doesn't!

The wing still has the flaps and ailerons to be added before they show their full? area.

Given how low set the wing is the ailerons will have to have top side horns.

Still thinking about how best to hand launch it as the fuselage is too wide to hold directly.

[GrumpyGnome]

Dual purpose cheater/finger holes in underside 🙂

[Futura57]

For launching I think it needs to hitch a ride on a model 747 like the space shuttle 😆

[Simon Chaddock]

Finger holes are my favoured option.

Probably 3 in a small triangle. Thumb and second finger just ahead of the CofG for support and a single index hole just behind the CofG to provide the final 'flick' for speed.

There is space under the duct to allow sufficiently deep blind finger holes.   

[Erfolg]

The Starfighter was a beneficiary from the X3 project. I have read that input from the project influenced the out line design in addition to more technical aspects (below skin deep).

 

I still have hope with respect to my own X3, in respect to the Starfighter, info on methods of construction and propulsion would be very, very interesting.

[Simon Chaddock]

Slowly moving forward. The full span aileron are installed and are also set to act as flaperons.

https://www.youtube.com/watch?v=d_4GFRgegXg

Two positions on a 3 position switch.

The object is to improve lift for launching rather than to slow sown for landing.

At the moment it looks like the X-3 will weigh about 16 oz. it has a wing area of 1.5 sqft giving a wing loading of 11oz/sqft. My heaviest EDF, a Hunter F6, which uses exactly the same fan has a wing loading of 8.24 oz/sqft. It hand launches fairly easily.

My biggest concern is the loss of thrust from the bifurcated exhaust. it raising the question as to whether it will be able to accelerate to a flying speed before it reaches the ground.

It will be interesting to find out!

      

 

[Simon Chaddock]

An underside view of what is virtually the complete airframe showing the exhaust fairing and the substantial battery hatch.

 

All the leads run into the battery hatch.

The 1300mAh 4s will be paced right up against the front bulkhead for CofG reasons.

There will also be a Lemon 'gyro' Rx to go in so a suitable platform will have to be built for it.

And all out of Depron of course! 

[Bill Southwell]

    I have had some good luck with researching the X-3. I have confirmed the horizontal tail used a stabilator for pitch control. And I found something that may help in gaining a little more lift for your hand launch...the X-3 required the use of it's full span wing leading edge droop plus takeoff flaps to take off. Oh and 260 knots or 300mph of ground speed as well. 

 

  I have a few close up pictures of the stabilator, wing L.E. drooped, and the flaps deployed. If you want me to post them just say the word. 

 

Best Regards

Bill

[Simon Chaddock]

Bill

I could not find any details of the tail plane although I guessed it was an all moving type so any info would be useful.

If, and its a big if, the Stiletto proves to fly well I will then set about giving it a scale tail plane layout. It should be possible to so with a minimum weight penalty.

 

It is the possible weight penalty of two extra servos that will likely deter me using separate flaps. My current layout with a single piece combined aileron and flap coupled with the ability to use them as shallow angle flaperons gives me potentially the best extra lift for launch without increasing the drag significantly.

 

In my perverse way the object of this build is to prove it is possible to hand launch a scale Stiletto rather than show detail scale features.

 

I do have an EDF that uses a scale all moving tail plane and jolly sensitive it is. The big issue is being low set the leading edges drop below the bottom of the fuselage so get damaged in a nose high belly landing with full "up" applied. This should not be a problem with the Stiletto as the tail plane is set well above the line of the tail pipes. 

[Bill Southwell]

 

 

I am with you on every gram left out is lift in the bank. I mentioned the leading edge droop as a possible fixed feature. It's helpful in improving slow flight and I have used leading edge droop on several delta designs and the drooped leading edge helped flight manners all around and especially slow flight and landing. I also found a pilot's manual and found it pretty interesting. Not sure if I can upload it here or not. I'll give it a try. I'll add more pics below.

 

Best Regards

Bill

 

 

 

 

[Bill Southwell]

[Bill Southwell]

 

Edited March 4, 2024 by Bill Southwell
Double picture removed

[Bill Southwell]

[Shaun Walsh]

8 minutes ago, Bill Southwell said:

Don't forget to fit the table lamp into the port engine exhaust, probably won't fly without it.

[Bill Southwell]

[Bill Southwell]

[Bill Southwell]

[Bill Southwell]