Freewing EDF Group

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5 years 6 months ago #19826 by AlanF
Replied by AlanF on topic Freewing EDF Group
The difference in static thrust is evident when doing a ground run canopy on vs canopy off, which would obviously help during launch. However, if there is a trade off with top speed then that's a harder decision.

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5 years 6 months ago #19828 by MikeSeale
Replied by MikeSeale on topic Freewing EDF Group
I've launched Jon's Mig (maiden and second flight). Simon's Sabre using the underarm method and my Thunderchief. I think that the correct c.f. and some up prior to launch makes then all easy. Just make sure you have enough power...I don't get the logic(?) of letting go on part throttle.

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5 years 6 months ago - 5 years 6 months ago #19829 by AlanF
Replied by AlanF on topic Freewing EDF Group
As far as I'm aware (and I'm no expert) the rational of using part throttle is that at full throttle the fan is stalled and produces excessive torque reaction (or is it gyroscopic precession, I'm not sure) for no gain in acceleration at a time when there is insufficient airflow over the wings to counteract it
Last edit: 5 years 6 months ago by AlanF.

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5 years 6 months ago - 5 years 6 months ago #19830 by DaveBright
Replied by DaveBright on topic Freewing EDF Group
It’s a static thrust vs dynamic thrust toss up. There was a book called ‘Ducted Fans’ by David James which stated some maths that helped you work out optimum inlet area vs fan size vs outlet diameter. Sometimes an acetate sheet rolled to give a smaller outlet can help increase the top end speed but it has to be right!
Last edit: 5 years 6 months ago by DaveBright.

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5 years 6 months ago #19831 by JonTappin
Replied by JonTappin on topic Freewing EDF Group
I have cut a cheat hole in the bottom of mine, I definitely noticed an improvement in thrust, but can't say I noticed any reduction in airspeed. I would recommend it

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5 years 6 months ago #19832 by Dave Rogers
Replied by Dave Rogers on topic Freewing EDF Group
Is adding cheat holes as bad as installing a gyro?

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