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Old Jul 13, 2012, 07:18 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Thanks vespa, good things to know.
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Old Jul 13, 2012, 08:58 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
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I may be wrong but it seems like the model is climbing quicker and has a higher level flight speed now with the new inlet configuration. Can you comment on that?

I'd also suggest that you may have pinched down on the inlet size a little too much. As I recall reading in the distant past a good rule of thumb for the ducted fan inlet to outlet ratio is about 1.5:1 in terms of area. If you do such a calculation you will need to not include the area blocked off by the tail end of the fuselage.
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Old Jul 13, 2012, 09:47 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Bruce, yes, I might have reduced the intakes a bit too much. I might rebuild the model from scratch after learning a lot from the savvy folks on this forum. Thanks for the 1.5:1 tip.
The plane does climb quite fast, but I thinlk that it has less than a 1:1 thrust-to-weight ratio. Is that common to other EDF's? I'm not inclined to try any loops with it yet. Maybe later with a 4S battery and stiffened wings.
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Old Jul 14, 2012, 12:53 AM
12th Pursuit Squadron
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Garland, Tx.
Joined Mar 2002
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I thought that the inlet for a ducted fan should be about 120% of FSA. I guess the faster the plane the lower the ratio. I would say that the inlet should not be any larger than the fan duct assembly. Of course, careful design with a specific purpose in mind can push both ends of these suggested numbers. Further research may be worth it, as I am not a DF expert just an avid modeler and gener aviation enthusiast who reads a lot.

J.P.
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Old Jul 14, 2012, 01:14 AM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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I did some area measurements: Duct intake area=5 sqin and FSA =4 sqin. That's 125% of FSA.
Also stiffened the wing with newspaper and white glue. Getting ready to try it with 4S.
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Old Jul 14, 2012, 01:57 AM
12th Pursuit Squadron
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Garland, Tx.
Joined Mar 2002
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Sounds good. First prototypes often up looking a bit like Frankenstein's Monster once all kinds of large and small changes have been made. With a bit of luck, the second will be pretty close to what you want and look good doing it.

J.P.
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Old Jul 14, 2012, 04:50 PM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
1,735 Posts
Jetiger flying with stiffened wing on 3S and 4S.
Lesson learned: Stiffness matters!

Jetiger Newspaper Stiffened on 3S (1 min 19 sec)

Jetiger With Newspaper (0 min 11 sec)

Jetiger on 4S (0 min 51 sec)
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Old Jul 14, 2012, 11:49 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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Quote:
Originally Posted by djacob7 View Post
Jetiger flying with stiffened wing.....

Lesson learned: Stiffness matters.
Love the new reports you can read while waiting for the packs to charge....

So on "stiffness matters", did you find that the model grooved better or was in some way more predictable in flight with the addition of the newspaper?

On the 4S pack the model sure does come alive. It covers a lot of ground in a hurry.
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Old Jul 15, 2012, 12:07 AM
Fremont, CA
United States, CA, Fremont
Joined Jan 2009
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Oh yes, Bruce, stiffening definitely made the plane more predictable and resulted in better authority; I wouldn't even dare to fly on 4S without it. I'm begining to love that plane haha! And my wife volunteered to paint it, so how can you lose!
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Old Jul 16, 2012, 01:28 AM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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Ah, nice to know that the wing skinning suggestion helped out for your needs even it turned out to not be the reason why the model was tripping over its own feet in flight.
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Old Sep 23, 2012, 07:13 AM
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United States, UT, Salt Lake City
Joined Oct 2007
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relative lateral area forward the CG- if no one has mentioned it -apper to be a real issue here
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Old Sep 23, 2012, 07:26 AM
Needs brain lubrication
biber's Avatar
Aachen, very western Germany
Joined Dec 2004
1,391 Posts
It's been mentioned.
The problem has been solved ten weeks ago, see post #36.

biber
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Old Sep 23, 2012, 08:31 AM
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United States, UT, Salt Lake City
Joined Oct 2007
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Good-
I scanned the thread -but early video caught my eye
Years back -there were a number of pusher glo engine canards - horrible designs for the most part -which had very long fuselages - forward the cg
once these yawed - it was easy for the model to enter fatal flat spins .
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