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        Discussion EDF 40 jet

#1 davezoom Apr 22, 2010 06:34 PM

EDF 40 jet
 
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Hi....Just building a very simple jet around a 40mm Fan unit.Couple of pics of the build so far. Just making it up as I go along , any comments would be greatly appreciated , Id love this to be able to fly.

#2 Esprit440 Apr 22, 2010 08:03 PM

Very interesting, I like the plastic bubble fuselage - is that made from a bottle? First time I can recall seeing anything like that. That would look very cool painted with a canopy area masked off!

I have a feeling that it will end up nose heavy since the fan is mid mounted and all the gear would appear to go in the forward fuselage. CG is probably close to where the front lip of the fan is now. Mounting the fan farther back and shortening the exhaust duct would help and give more options for locating everything else.

Vertical tails would look a little better canted outwards I think, but that is subjective. :)

I'll be interested to see this one progress.

-Matt

#3 Rusty-Gunn Apr 22, 2010 09:31 PM

I'd agree as to the CG area. Perhaps on MKII you can move the EDF rearward, and angle the twin tails, too. Otherwise, its a nice EDF. I'd like to see this one fly.

#4 davezoom Apr 23, 2010 01:24 AM

Thanks for those comments.It is only pinned together at the moment so I can make any adjustments suggested...:)

#5 davezoom Apr 25, 2010 06:04 PM

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ok...made a few adjustments as reccomended, As she stands now with no equipment installed she glides like a dream. I will mount the motor further back but will install tube and motor probably last so I can adjust c of g to suit.
As she is gliding almost perfectly I should be able to pin point the balance point at this stage correct?

#6 Esprit440 Apr 25, 2010 07:25 PM

You should be able to get very close to the "correct" CG with a gliding airframe at this stage.

Try to get it flying in a very slight continuous dive rather than a slower, floating flight.

Small light models like this can fly nicely with CG positions that are unusably tail-heavy when the weight of gear is added later and wing loading goes way up.

-Matt

#7 davezoom Apr 28, 2010 06:42 PM

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Servos now attached and elevator/ailerons installed.
All up weight should be around 150g .
Im using a 7.2V 500mah battery which with the motor should give 114g thrust according to some data I have for the motor and fan.
Ive no idea on thrust to weight ratios so does anyone have any input on this....Thanks

#8 davezoom May 01, 2010 05:15 PM

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Finished except I want to find a better way to do the canopy. Fired her up in the lounge and she flew across the room on a partly charged battery. Hope to maiden her sometime this week if the weather improves.....:)

#9 Esprit440 May 01, 2010 09:13 PM

I actually like the canopy. :)

What's the green stuff in the exhaust duct, tape? You'll want to make sure it's nice and smooth there.

-Matt

#10 davezoom May 02, 2010 02:54 AM

Matt.... its the rim from a milk bottle top ive inserted to keep the foam duct open , it fits reasonably flush but could be better.
Total flying weight with battery is 143g .

#11 davezoom May 03, 2010 06:54 AM

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Decided to enlarge the wing area ......Im hoping it will need less power then to keep it in the air ?

#12 davezoom May 03, 2010 12:29 PM

Di a trial flight...she did fly but tail heavy ,even flew into the wind reasonably well, will need to do some adjustments. any advice with setting up a delta wing with elevon control would be much appreciated.

#13 Sabrejock May 03, 2010 03:51 PM

The center of yaw stability [v/fins] seems very close to the center of balance. And with that amount of nose ahead of the center of balance, beware of a tendency to flat spin if turbulence or handling put too much yaw in for the fins to handle. If it is a problem, you can angle the fins backward out even beyond the trailing edge.

Been there, done that, and got the T-shirt:eek: Tex.

#14 TANGOSIERRAROM May 04, 2010 08:20 AM

You should be on the money at 114g thrust to 150g auw anything around 60% and up should fly pretty well. You will need to make sure the ducting is good ideally the the exit wants to be about 90%FSA to get the most out of the fan at flying speed.

#15 rudes May 05, 2010 05:14 AM

davezoom can you tell me the c rating of your battery and the kv of the motor please. And whats your thoughts on this http://www.lowpricerc.com/product_in...products_id=65 I don't have any edf units and was wondering if I should try these.

The canopy looks great, paint it black on the inside and a white rubberband around it about a third of the way back should look ok :)

Thanks
Rudolf


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