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Old Apr 26, 2010, 06:13 PM
Wonderfully Wicked
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Willoughby, Ohio
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Quote:
Originally Posted by Lardog View Post
So, is it safe to assume they have the default CoG specified incorrectly? Did you try with the CoG at 95mm before changing the horiz stabs? Also, how much weight, if any, did you end up leaving in the nose?
Thanks Don.
I did CG and incidence change both at the same time. I still have 1.25 oz lead in the nose. I think there is something going on with the way the stock model is setup. The CG should not change unless the aerodynamics change and a slow flying version with the nose up may have quite a difference downwash pattern over the wing hitting the tail and when adding the upgraded power the aerodynamics are changing as well as the model is now more nose down. Just a guess on my part as I have never had a model do this before.
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Old Apr 26, 2010, 07:41 PM
ex-noob
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Sammamish, WA, USA
Joined Jan 2010
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Quote:
Originally Posted by The Don View Post
I did CG and incidence change both at the same time. I still have 1.25 oz lead in the nose. I think there is something going on with the way the stock model is setup. The CG should not change unless the aerodynamics change and a slow flying version with the nose up may have quite a difference downwash pattern over the wing hitting the tail and when adding the upgraded power the aerodynamics are changing as well as the model is now more nose down. Just a guess on my part as I have never had a model do this before.
Good to know. This should help me be able to get mine balanced better. You also have a 4s pack which weighs more than my 3s pack, so I image mine did even more of a tail dance than yours did initially.

Thanks again for sharing your experience. It is invaluable.
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Old Apr 29, 2010, 01:53 PM
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USA, CA, Dublin
Joined Jul 2006
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Quote:
Originally Posted by Lardog View Post
Good to know. This should help me be able to get mine balanced better. You also have a 4s pack which weighs more than my 3s pack, so I image mine did even more of a tail dance than yours did initially.

Thanks again for sharing your experience. It is invaluable.
Please keep me updated on how it flies with CG at 95MM and no incidence change for the stabs.

I'm slowly building mine. Going to be running it with the wemo/don's 5400 kv combo on 1800mah 3S. Also did the mod with the dual aileron servo on top.
Oh and I'm planning on glassing the wing with some .7 oz fiberglass and WBPU and maybe some carbon fiber tow for added stiffness(still debating the carbon fiber)
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Old May 02, 2010, 11:27 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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It dawned on me today that I do not have my tanks installed on my model. Those tanks will have a nose down pitching effect associated with them. I am not using them so do not have this and this may be the root cause of the issue.
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Old May 02, 2010, 11:29 PM
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Sammamish, WA, USA
Joined Jan 2010
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Hmm. I don't have mine on either. I imagine the specified CG was determined with the tanks on. Wouldn't have figured they had that much of an effect though.

I have it re-balanced at ~95mm. I had to add 1.5 oz of lead in the nose to do it. I have not yet had a chance to fly as the weather has been crap.
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Old May 05, 2010, 03:44 AM
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Well, I got her up today. There was a little wind, but I couldn't wait. Had a partner give it a good toss and up she went.

CG seemed pretty good. I had it balanced dead on at 95mm (with a 2200mAh 30C pack crammed in the nose). It did seem like it had just a touch of nose up tendency during flight, but overall, was quite good. This might the the up incidence in the elvator that Don and others have mentioned or, could just be that the correct CG for this model (without the tanks attached) is between 90-95mm.

Anyway, this is my first EDF and my first flight, so I spent most of it just trying to get the feel of it. Performance seemed pretty good with the Wicked 5400 combo. It isn't a speed demon, but it's no slouch either. I'm happy with its speed and spent most of the flight at WOT .

I did notice the ailerons were really touchy, so I will likely dial them down some more. I just eyeballed the throw measurements and set the rate adjust down to 70% on my radio, trying to get them around the recommend 10mm. I think I will try 60% to see if I can get it to be a little less twitchy.

Looking forward to some good flight time on this. It looks great zipping through the air, nice and sleek.

Thanks all for all the advise and info.
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Old May 06, 2010, 03:24 PM
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Sammamish, WA, USA
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Flew it again this morning, all went well. Again, the speed generally seems pretty good, however, there seems to be a fairly substantial lack of thrust. It doesn't climb particularly well and has a difficult time even trying to do a loop. This is my first EDF, so I am not experienced enough to know. Is this typical or normal for an EDF or one with a smallish 50mm fan? Compared to my prop planes, the difference is significant and very noticeable.

I am running 2200mAh packs, both 25 and 30C. I am wondering if going down to an 1800 to save some weight would help. From the specs though, we're looking at under 1 oz difference between the two, so I'm not sure whether this would provide a noticeable improvment or not.

Thoughts?

Thanks,
Larry
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Old May 06, 2010, 04:51 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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Do you have a thrust tube installed?

Don
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Old May 06, 2010, 06:00 PM
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Sammamish, WA, USA
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Yes. I tried to make it as close as I could to your specs. I made it with a 1.8" diam.
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Old May 06, 2010, 09:50 PM
Wonderfully Wicked
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Willoughby, Ohio
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Which fan are you using? 1.8" is for 60mm fans.

Don
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Old May 06, 2010, 11:21 PM
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Sammamish, WA, USA
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Using the Wemo Combo 50mm. What should the diameter be a the end of the tube?
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Old May 06, 2010, 11:25 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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1.48" for 80% FSA
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Old May 06, 2010, 11:27 PM
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OK, that's quite a difference. I'm a bit confused though, as I thought you indicated that bringing down the FSA like that was for more speed, not thrust. Will it provide more of both?
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Old May 07, 2010, 12:25 AM
Wonderfully Wicked
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Willoughby, Ohio
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Yes but 1.8" is 120% FSA which is bad. You can try 1.65" for 100% FSA and 1.57" for 90% FSA.
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Old May 07, 2010, 12:27 AM
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Sammamish, WA, USA
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OK. I'll make the adjustments and give her a go.

Thanks again Don.
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