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» 2019 Llanfair TH Village Fete
wing with edf ducted fan unit Empty2019-07-12, 18:53 by Rich

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wing with edf ducted fan unit Empty2019-05-08, 17:49 by Gary M Jones

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wing with edf ducted fan unit Empty2019-03-03, 23:44 by Charles E Cornes

Saturday 7/7/18

2018-07-07, 21:07 by Gary M Jones

I was at the field today between 14:00 & 15:00 all on my own , good flying too. There is a dead sheep along the fence line towards the gate from the pits, I saw the farmer so reported this to her. I hope no one had plans for a BBQ Smile .

Farmer …

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Post by Guest on 2011-08-07, 20:06

fitted a 68mm unit to a Wing,Zagi style.First attempt ,no thrust angle and forward of c of g power on Nose went down when power applied.Next up thrust, power applied same result.Any ideas please.

Anybody got a Jet Fuz only suitable for a 68 mm edf fan unit ?

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Post by Guest on 2011-08-07, 20:45

how much reflex do you have ?

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Post by Guest on 2011-08-07, 21:28

Gary thanks for reply.I understand Reflex as a time concept but not sure what you mean by Reflex

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Post by Guest on 2011-08-08, 08:39

Zagi's should have around an 8th of an inch up aileron both sides (might be a little bit more ) for them to fly sunny ive had a few Zagi's slope and electric and thay all needed Reflexed / up ailerons Very Happy

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Post by Guest on 2011-08-08, 08:52

If the fan is mounted on top of the wing near the centre of the wing you will have a considerable nose down couple generated when the power is applied. The fan should be mounted as far towards the rear of the wing as is practicle. The thrust angle of the fan should be such that the rear of the fan points slightly up and the front points down at a shalow angle to be finalised after testing. The angle is very dependant on the fan position.
For the reflex - place a straight edge on the bottom of the wing aerofoil where the ailervons are attached and set them in line with this straight edge datum. This will provide a starting point.
HTH

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Post by Andy Sayle on 2011-08-08, 09:19

The other thing to bear in mind John, is that flying wings can only ever be trimmed to fly straight and level (effectively hands off) for one airspeed. If the airspeed is above that trimmed airspeed, the model will want to climb, and if it is below that trimmed airspeed, the model will want to dive.

The amount this affects a particular model, depends on the pitching moment of the aerofoil section(s) used, the centre of gravity position (in relation to the centre of pressure for the wing) and also the flexibility of the control surfaces/linkages.

As you are seeing the opposite of this, what Allan says is correct, the nose down pitching is down to the thrustline being well above the centre of gravity. lowreing the fan as much as posible, and pointing its axis towards the centre of gravity will help. What I did on a little delta EDF a couple of years ago, was bury the fan as much as possible, and carve out a smooth intake and exhaust in the foam. This still had a big pitch change with throttle, but you soon get used to it when flying Smile

Andy

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Post by Guest on 2011-08-08, 13:10

thanks Guys I appreciate your help.So I had it front end pointing up should be back end position with front pointing down.
Quite proud of myself I seem to understand what you said Twisted Evil

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Post by Rich on 2011-08-08, 13:20

Thats it John opposite to a front mounted prop

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Post by Guest on 2011-08-08, 16:51

Rich wrote:Thats it John opposite to a front mounted prop

thanks Sir

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