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-   -   my first EDF jet (https://www.rcuniverse.com/forum/questions-answers-154/4154764-my-first-edf-jet.html)

matt138 04-11-2006 10:31 PM

my first EDF jet
 
I'm planning on building an EDF F-16 and here are the estimated specifications:

wing area: ~140 sq.in.
motor: speed 400(around 10 oz thrust)
weight: 16-18 oz.

Is there anything wrong with the specs. ? should I go for it, or should I increase the wing area or is it okay? I might prolly change to brushless.

firstplaceaviator 04-12-2006 06:38 AM

RE: my first EDF jet
 
I would increase wing area to at least 180 sq. in.

Use a brushless motor to start with. Brushed mototrs in ducted fans usaually don't last more than a few flights.
I recommend a Model Motors "Mini AC" 1215/12 12 or a MPJet AC 25/25-26 Mk. 2

Don't even consider Ni-cad or Ni-Mh batteries. Use only Li-Po's. a Thunder Power 3 Cell 1320 Mah battery will be perfect.

Keep us posted on your progress!
Doug

matt138 04-12-2006 07:11 AM

RE: my first EDF jet
 
Thanks Doug. I had the same idea, increasing the wing area to 180 sq. in. because I noticed most ARF 400 size EDF Jets have around the same wing area. Anyway, I'm just planning on the materials and power system for the F-16 I'll probably start making it in 3 more weeks. I will post my progress here.
I was wondering how to exactly calculate the wing area. The 140 sq. in. was measured from 2 trapeziums on the sides and one rectangle in the middle, or should I measure it as a triangle at the top and a rectangle at the bottom ?
http://img100.imageshack.us/img100/7...problem0nl.gif
I used the first picture to calculate the wing area, is taht right ?
Thank you.
matt

firstplaceaviator 04-12-2006 09:51 AM

RE: my first EDF jet
 
Matt,
Manufacturers use several methods for calculating wing area.
Some even include the wing center section (through the fuselage) in their calculations!
I ususally subtract the fuselage out. Full scale engineers don't include the fuselage as wing area.

But, becuase the shape of the F-16, the fuselage does provide quite a bit of lift.
So, your 1st diagram and calculations will work just fine.

My Byron F-16 is very difficult to stall becuase of the shape. It just goes into a nose high attitude and starts loosing altitude quickly!
Just add a bit of throttle, and it flies beautifully in high alpha.


For me, it is easiest to calculate a rectangle, then subtract out the triangular portions.

matt138 04-13-2006 11:28 AM

RE: my first EDF jet
 
Thanks again Doug, that really helped. I've already modified my sketch to fit the new wingspan. I'll probably start cutting some white foams soon, screw that 3 weeks :D.


matt138 04-14-2006 10:59 AM

RE: my first EDF jet
 
As promised here are the pictures of 2 days progress:
http://img519.imageshack.us/img519/9739/img00236tv.jpg
http://img514.imageshack.us/img514/9265/img00270ns.jpg
http://img514.imageshack.us/img514/4225/img00292bb.jpg
http://img514.imageshack.us/img514/6035/img00305og.jpg
The white foam with this model really requires ALOT of sand papering. The dimensions aren't as exact as the full scale, the middle platform was taken from here http://www.rcgroups.com/forums/showthread.php?t=337663 . I had to add some wingspan to get the 180sq in wing area. For me as long as it "has" the shape of the real F-16, it should be ok :eek:. Anyway I have to wait for another 2 weeks before I start on the back and the ducting parts because I'll need to get the ducted fan system first.

firstplaceaviator 04-14-2006 12:05 PM

RE: my first EDF jet
 
Lookin Good Matt!
If I didn't already have WAY TOO MANY planes, I'd ask you to build me one too!

matt138 04-14-2006 11:50 PM

RE: my first EDF jet
 
TOO MANY ??? How many is that ? I've never built a plane for anyone before maybe it's because there are not many who likes RC airplanes at my place. I've always thought about selling some too, but I think I'll do that after I get out of college. However, recently a friend of mine just started to be interested in RC modelling after watching me building that F-16. Suprisingly he has already started on his own model, a Euro Fighter EDF.

firstplaceaviator 04-15-2006 07:45 AM

RE: my first EDF jet
 
Well, for me 23 RTF planes, 4 helis and 114 kits is too many. I'm out of room...Time to liquidate again!!!!!!!!

When I was in college, I only had one 42% Scale Extra 300, a Goldberg Extra 300, a Lanier 1/4 scale Laser 200, a Yardstick and about 3 kits!

I've been out of college for 10 years now. Most of the model stuff I have has been purchased since I got married and bought a house in 1999. Oh yeah, did I mention the full scale Cherokee?

Doug


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