An EDF Concorde - in Depron.

With the 10th anniversary of the last flight just gone I felt it was time to build one.
This will be a continuation of the 'scale ducts' theme as I applied to the Fairey Delta 2 so it is going to have to be very very light.
First I modified a 3 view to remove all the surface detail so when printed out big it can act as a plan.

This would follow the same 'EDF right at the back principle' I used of the FD2 to ensure the maximum static thrust. This location also has the advantage that Concorde's engine nacelles were actually circular at this point.
So how big?
Some quick calculations showed that Concorde with anything bigger than a 40mm EDF would be huge and even with 40s the fuselage is going to be 90" long!.
A cheap 40mm is claimed to give 6oz thrust on a 3s so using 2 and keeping to a 0.6:1 thrust to weight ratio the Concorde must weigh no more than 18oz complete.
For transport the nose section (27") and possibly the tail cone (7") will be removable. The rest will be one piece and include all the electrics and battery.
The intention is to build the nose section first to get an idea of weights and stiffness before committing the time and effort to build the rest.

The nose section (and probably the rest of the fuselage) will be built entirely in 2mm Depron as a 'half shell' over the plan with closely spaced formers but no other internal structure.
This is going to take some time!

I had KK print me off a set of plans for a 4ft wingspan version and i was going to built it out of depron as well, just never got round to it.

i will be watching this one progress with great interest.

Brilliant!!!! Can't wait to see this build thread How will you make the nose section and tail cone attach?

Removable fixing?
Haven't decided yet but I favour a small balsa 'tongue' that slides into a Depron box but in a crash designed to snap off before the fuselage is damaged.

A modest start on the nose section inserting the formers.

This is a minimum construction with no keel or internal support just the formers and the skin. To ensure it retains the correct shape it has stay secure over the plan until the skin is complete. Even after the complete half shell is lifted it is still flexible in torsion so care is needed to avoid building in a twist as the other side is added.

A start on the planking.

Each plank is curved to match the profile of the former to avoid the finished cross section being made up of a series of 'flats'. With such a thin skin the smooth surface has to be achieved with the minimum of sanding.

And the nose section only represents 1/3 of the total fuselage!

The half shell complete and the other side formers added.

The other side progresses.

Worked late this evening so it it now very nearly complete.

It weighs 1.4oz yet is amazingly strong and rigid.
I suppose I shall have to start the rest, once I have worked how on earth I am going to make it!

I have noticed you are always useing new pins from the packets or holders, or do you put them all back in the packets after use,

The pins go back in the holder that way I can tell if any are missing!

The wing plan printed out.

It is pretty big but with the nose section removed it will go in my car (famous last words!) but it might be a bit of a problem to get much else in there as well!

As it is so big I thought I had better build a 'test' nacelle to check the thrust before going any further.

It is shaped to follow the wing under surface.

However as it is only a test item it is built as a box. In the model the wing under surface will be the top of the nacelle.

The 40mm EDF fitted with the Depron dummy jet pipe along side.

The nacelle is 17" long, 3.5" wide and 1.6" deep. It weighs 1.2oz with the EDF.
It delivers 4.2oz thrust from 13.75A at 7.35V (109W).
It all seems very little for a 7'6" long plane!

Looking beautiful..... I got my ticket......

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Cpl Jones

Cpl Jones
I have one of those from my visit to G-BOAC at Manchester. I know I kept it but I can't find it at the moment!

Eric
4 fans?
This is really a question of its final weight.
With 2 fans (28A) I will probably use an 1800mAh 2s to minimise the voltage drop. It would be drawing 15C giving 4.5 minutes duration - assuming it flies at all!
With 4 fans (56A) it would need at least a 3000mAh 2s and a good one at that or the voltage drop would seriously eat into the extra thrust required to carry the additional weight of the 2 fans, 2 ESC and bigger battery (about a 20% increase).

I have cut the 4 wing skins.

With these and from what I have built so far I can 'guestimate' the final weight with 2 fans and an 1800Mah 2s at close to 18oz.
I fear a bit marginal with 2 fans and just 8.4oz thrust.
16oz thrust for a 24oz all up sounds a bit better but I don't have to decide just yet.

Not much progress as this morning I had to put the British Gas team out of a job and fix my central heating boiler.
A quick inspection showed the fan was not running. A more detailed look showed the power was getting to the induction motor and it was indeed trying to turn but the bearings were stiff!
Only two self tappers hold the whole fan in but you have to know exactly where to hit it with a hammer to break it loose. The oil in one 'oilite' bearing had congealed. Easy enough to fix with WD40 and then 3in1. A plumber would of course have simply replaced the fan unit at £170 plus labour!

The next Concorde job is to fix both fans to the 'test' nacelle to see what thrust it produces to check if the 4 fan 'Plan B' option is viable.