SnowRocker88
Amateur pilot and builder
Well, it certainly looked cool! Keep us updated on the new configuration's results. Would it just spin at low speeds or did it seem far from stall?
A 'ducted' ducted fan!
- Thread starter quorneng
- Start date
quorneng
Master member
SnowRocker88
When it was doing it was the problem. It literally just stopped flying normally and spiralled in. As you can imagine after the first couple of crashes I was concentrating on both not letting the speed drop and keeping high to allow recovery but to no avail!
Once spinning the controls had absolutely no effect at all - it just kept rotating.
To make matters worse I already had an EDF with wings and tail of an almost identical 'Hawker' plan form and that flew very well with no tendency to spin at any speed!
This puzzling behaviour was the main reason for rebuilding it without the ducts. I just had to find out what was happening.
When it was doing it was the problem. It literally just stopped flying normally and spiralled in. As you can imagine after the first couple of crashes I was concentrating on both not letting the speed drop and keeping high to allow recovery but to no avail!
Once spinning the controls had absolutely no effect at all - it just kept rotating.
To make matters worse I already had an EDF with wings and tail of an almost identical 'Hawker' plan form and that flew very well with no tendency to spin at any speed!
This puzzling behaviour was the main reason for rebuilding it without the ducts. I just had to find out what was happening.
Last edited:
quorneng
Master member
To clear the EDF exhaust the batteries had to be mounted low down in 'pods' on either side of the fuselage.
The ESC was 'wrapped around the EDF on the LH side.
At least the pods ensured stability when sitting on the ground!
The radio was placed above the wing.
Without the complex ducting it is actually slightly lighter at 11.7oz and the EDF now generates very near its 18oz 'free air' thrust giving a thrust to weight ratio of 1.5:1!
The maiden flight was no problem except when approaching a fast(ish) pass the whole nose broke off just ahead of the fan. The remained of the plane continued to fly well enough to complete a circuit and achieve a safe landing with no further damage.
This gave me a clear pointer to what was actually happening.
I had assumed on all the previous crashes that apart from the obvious nose crushing the bend in the fuselage was the result of the ground impact. Clearly it wasn't. The whole nose was obviously being deformed in flight so acting like a huge forward rudder. No wonder it spun in.
To make matter worse moving the CofG further forward increased the flying speed and probably made matters worse!
Appropriate reinforcing of the fuselage around the fan greatly increased the bending stiffness.
It now flies very well with a blistering performance. Small, white and very fast it is now even harder to see - let alone in a video!
As it is still only a 'test bed' of limited strength full power is only ever used when in a vertical climb and then only for a couple of seconds. Any longer and it is out of sight!
So far it shows no sign of entering a spin so I have started to move the CofG back again!
Testing will continue whilst I build another set of cascade ducts but this time for a bigger 70mm fan.
The ESC was 'wrapped around the EDF on the LH side.
At least the pods ensured stability when sitting on the ground!
The radio was placed above the wing.
Without the complex ducting it is actually slightly lighter at 11.7oz and the EDF now generates very near its 18oz 'free air' thrust giving a thrust to weight ratio of 1.5:1!
The maiden flight was no problem except when approaching a fast(ish) pass the whole nose broke off just ahead of the fan. The remained of the plane continued to fly well enough to complete a circuit and achieve a safe landing with no further damage.
This gave me a clear pointer to what was actually happening.
I had assumed on all the previous crashes that apart from the obvious nose crushing the bend in the fuselage was the result of the ground impact. Clearly it wasn't. The whole nose was obviously being deformed in flight so acting like a huge forward rudder. No wonder it spun in.
To make matter worse moving the CofG further forward increased the flying speed and probably made matters worse!
Appropriate reinforcing of the fuselage around the fan greatly increased the bending stiffness.
It now flies very well with a blistering performance. Small, white and very fast it is now even harder to see - let alone in a video!
So far it shows no sign of entering a spin so I have started to move the CofG back again!
Testing will continue whilst I build another set of cascade ducts but this time for a bigger 70mm fan.
SnowRocker88
Amateur pilot and builder
Very cool. Glad you found the problem. I never would have thought it was the nose curving.
SnowRocker88
Amateur pilot and builder
Are you going to re-make the cascade ducts since you found your problem? Is this still an ongoing project or has it been deemed finished with the unmodified EDF?
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