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Old Oct 29, 2013, 08:30 AM
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Fairey Delta 2 - in Depron.

In 1957 the Fairey Delta 2 held the world speed record at 1132mph. Quite a remarkable achievement for a relatively small aircraft company.
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Always a research plane just 3 were built. (2 flew, 1 for structural testing)
A simple true delta with a circular section fuselage wrapped around an early after burning Avon jet.
The question I asked myself was using lightweight construction techniques in Depron could I make an the FD2 as an EDF with scale inlets and exhausts?
A look at a 3 view confirmed that the combined area of the inlets was actually as large as the restricted nozzle for supersonic flight so acceptable for an EDF.
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The problem was of course the area was small so the fan was going to be too. For 32" span a scale jet exhaust would be 55mm diameter.
The EDF itself would be placed right at the back with no exhaust tube at all. This had the advantage that the entire inlet would be nearly 20% larger than the fan swept area with hopefully reduced ducting losses.
This was going to be a true monocoque structure with all the loads carried the Depron skin. This meant the wings would be actually be fixed directly onto the duct so the stresses in the wing skin were carried around the fuselage duct.
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First I 'tidied up' the 3 view.
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And then 'tile' printed each view out to the required size.

The wings are simple indeed. No ribs or spar just accurately sized Depron shear webs.
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The top skin is glued on 'free hand' to draw the two skins into a simple symmetrical (and very thin!) wing section. Good eyeball skills required to make sure it remains true and that both are identical.

The majority of the EDF duct is a simple 2mm Depron tube wrapped around a piece of gutter down pipe.
The wings are glued directly to the duct.
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The two part fuselage formers are added. Each former position corresponding to a wing shear web.
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So far so good but was it really going to be possible to build (and fly!) an EDF made entirely out of 2mm Depron?
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Old Oct 29, 2013, 10:14 AM
killickb
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The Villages. Florida
Joined Jan 2005
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This is exciting ! I built the Veron free flight ducted fan version back in the 60's. Powered by a .15 size diesel engine. It flew very well. It too was monocoque in designSince then I obtained from Phil Smith, the Veron designer, a new set of plans and patterns. He knew of nobody ever having installed an edf but it is a perfect candidate for a 50mm fan.

Hope your build is very successful and maybe it will stimulate me to finish my edf conversion. Keep the details coming.

An interesting fact that this Veron design is not available through one of today's Veron kit producers, as a laser cut short kit, is that the needle nose design of the FD-2 is considered to dangerous to sell as a commercial model kit !!!!
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Old Oct 29, 2013, 10:37 AM
The "pro" in procrastination
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Canada, ON, Kingston
Joined Mar 2004
2,902 Posts
Hey Quorneng,

Fascinating techniques on an interesting subject! I'm just finishing up my own first Depron build, and have been really impressed by the potential of the material. What glue are you using? As far as the Delta goes, I continue to be amazed at the number and variety of aircraft designs that came out of Britain until 30 years ago or so. Don't stop posting.

Steve
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Old Oct 29, 2013, 05:06 PM
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The much harder bit is making the bifurcated inlets.
First the appropriate formers are added.
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With sufficient planking added to stabilise the structure duct is cut away to create the 'holes' for the bifurcated duct.
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To complete the duct the nose section is required. A former and plank structure built vertically.
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Very delicate to start but get stronger as more planking is added. The cockpit is lined internally. It will contain the battery with the ESC. mounted behind.
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At this stage the long pointed nose is left off.
The tail cone is also built vertically.
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But as the internal duct tapers it is of a planked construction.
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The EDF itself is fixed to the end.
With the three sections joined together some of the external planking can be added to improve the overall rigidity.
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The electrics and cabling will have to installed before the external skin can be completed.
Note the huge size of the elevon.
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Old Oct 29, 2013, 08:26 PM
Oh no, not again!
jhspring's Avatar
United States, LA, Carencro
Joined Dec 2005
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Wow, not just a cool subject, but very innovative construction techniques. Watching with interest. Jeff
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Old Oct 30, 2013, 04:16 AM
I don't like your altitude
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Old Oct 30, 2013, 11:33 AM
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The electrics start ot go in.
The ESC is mounted flush with the top of the fuselage and is heavily finned.
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The radio and an elevon mixer unit are mounted between the duct and the skin.
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I could have used the 'elevon' function on the DX6i but I found that it severely limited the elevator travel. The mixer seemed to provide a much better compromise with a degree of over travel being used when the elevator and aileron were used together.
With the EDF right at the back the exhaust is the fan swept area (2242sqmm).
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The inlet duct is considerably larger, averaging at least 4400sqmm. Overall this should mean lower duct losses than if the EDF was placed in the middle of the fuselage.

The wing is so thin that the 3.7g servos have to lie flush with the wing under surface.
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With all the electrics installed and tested the skin can be completed.
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Light enough to be hand launched it just needs the right weather.
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Old Oct 30, 2013, 12:17 PM
upside down and inside out
mrbump's Avatar
Switzerland, ZH, Zurich
Joined May 2012
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Very nice subject. My father in law had some role (not exactly sure what) in the development of this beast. So it's on my long list of planes to build one day.

I'll be watching this with interest.

I have one question though: How strong is your ducting? From looking at the pictures I'm somewhat concerned about the fan digesting everything in front of it - which is the whole plane, given the fan's position.
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Old Oct 30, 2013, 02:29 PM
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mrbump
I can only say that although made of 2mm Depron it is in effect a tubular 'structure' with complete inner and out skins with closely spaced ribs.
Being built from the inside outwards all the glue joints can be made true and secure and as a result it is remarkably rigid.
In addition with its generous inlet duct area I would hope any negative pressures will be modest.
Finally it is only a cheap 55mm fan drawing 300W as a maximum!
With an 1800mAh 3s it weighs 19oz unpainted.
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Old Oct 30, 2013, 05:40 PM
killickb
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The Villages. Florida
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Nice build -- it just looks right, bet it flies very well ! Now what color? Silver or Blue ? I think it was both Blue and Purple when it had the Concorde wing shape -- BAC 221.
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Old Oct 30, 2013, 05:56 PM
killickb
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The Villages. Florida
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Oops, my mistake. You can also paint "Mauve" and white which is the color it had when going for the World Speed Record --- which it did achieve. So you have Natural, Royal Blue or Mauve. BAC 221 was only ever Pale Blue I believe.
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Old Oct 31, 2013, 06:31 AM
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Normally I maiden first and decorate after simply because the maiden can show up changes but in this case I painted first - Royal Blue.

Actually not an ideal colour over white Depron as it needed two coats to get anything like decent coverage although by careful masking the 'go faster' stripe and the border to the roundels could be left natural Depron.
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Completed with some simple vinyl decals.
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It now weighs just a fraction over 20oz with 16oz static thrust with a modest wing loading of 8oz/sqft.

The maiden did not go too well. A short 3 seconds with almost no control that resulted in some damage.
A substantial split almost completely round the fuselage at the inlets.
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And a bend in that long nose!
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I judged there were two issues.
1. The CofG was too far back. Not that surprising with a relatively small delta on such a long fuselage. The battery compartment was however big enough to move the battery to be moved forward by 1".
2. The huge one piece elevons were just too big making it just too sensitive in pitch. The original actually had separate elevator and ailerons so the surface was divided with the original ailerons becoming the elevons with the elevator portion being fixed with some modest reflex.
Fortunately I had accounted for this possibility and the servos in the wing were placed far enough out to allow for this.
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Fully repaired it worked!
Depron Fairey Delta 2 EDF (3 min 19 sec)

Not the easiest thing to fly but it has plenty of power reserve and it glides nicely, however quiet it is not as like all these lightweight Depron builds the structure acts as a wonderful sounding board!
About its weakest point is the aerodynamic balance tips on the elevons get easily broken in the belly landing (the RH one did in the video!) with any degree of 'up' elevator applied.

In hindsight (and maybe a future modification) is to revert to the scale ailerons and elevators. It would have a small weight penalty (two extra servos) but it would also enable up elevator to be safely used on landing without risking the tips of the ailerons.
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Old Oct 31, 2013, 08:14 AM
killickb
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The Villages. Florida
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I would most assuredly call that success, very nice. Remember you designed, built and flew, you didn't shake the box and out came an ARF. Now you have to fine tune it and you have a unique one-off model.

Next step is a 70mm version ! Again, well done sir.
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Old Oct 31, 2013, 10:24 AM
Oh no, not again!
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United States, LA, Carencro
Joined Dec 2005
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Congratulations Quorneng. Great job! You could do separate elevators with only a single extra servo. A U-shaped connector to link them and one servo to drive them. Anyway, nice work. Jeff
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Old Oct 31, 2013, 11:39 AM
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Jeff
One servo?
It would need a substantial U shaped link (the elevators are 5" apart and it would have to pass right through the middle of the EDF duct creating drag.

Overall I suspect that using two (smaller?) servos would result in little extra penalty.
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