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Old Mar 28, 2012, 10:26 PM
Capt. Z
falcon5's Avatar
United States, NV, Las Vegas
Joined Dec 2004
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Quote:
Originally Posted by flyingfitz737 View Post
I would consider bearing at around 25% MAC. Then balance. This is closer to the subsonic aerodynamic center. But if it worked for Fiorenzi then what the hell!

Edit: The leading edge has a pretty good sweep angle. Have you located the MAC? 25% MAC might be pretty close to halfway back at the root. Post your root chord, tip chord, tail 1/2 span and the pivot point location back from the leading edge and I'll draw a picture if you want. Or, just balance it like Fiorenzi and it should work!
Hi Fitz, soryy for the late reply: Cool about Story's pics and book!!!

root chord=16 3/8"
tip chord= 5.5"
sweep = 9.25"
span 15 3/8"
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Old Mar 28, 2012, 10:36 PM
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Colorado Springs, Co
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Andy, I may be a little late to the dance, but ... several years ago on the "other site" there was a very long discussion about placement of the pivot, and balancing. Might be worth a look.
Secondly ... or firstly ... why not drop an e-mail to Phil Avonds? If ANYONE would know about designing a non-fluttering flying stab it would be him!
FWIW, my 14 year old Avonds F-15 has the pivot point at ~50% , as does my Tam's F-16.
36 pounds of thrust doesn't seem to bother it......

Greg
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Old Mar 28, 2012, 10:41 PM
Faith in Lift.
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Joined Oct 2006
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And the beat goes on!
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Old Mar 28, 2012, 11:13 PM
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Steens, MS
Joined Oct 2009
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I just found this thread!!! Oh the memories!!! I live 12 miles from Columbus Air Force Base where Air Force pilots are trained and the T-38 is their advanced trainer. I'm retired now but here are some pics of my "VIP" flight . I too will build a T-38 one day. Here's my documentation too!. Keep up the outstanding work!!!
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Old Mar 28, 2012, 11:16 PM
Capt. Z
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United States, NV, Las Vegas
Joined Dec 2004
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Quote:
Originally Posted by gbmoore View Post
Andy, I may be a little late to the dance, but ... several years ago on the "other site" there was a very long discussion about placement of the pivot, and balancing. Might be worth a look.
Secondly ... or firstly ... why not drop an e-mail to Phil Avonds? If ANYONE would know about designing a non-fluttering flying stab it would be him!
FWIW, my 14 year old Avonds F-15 has the pivot point at ~50% , as does my Tam's F-16.
36 pounds of thrust doesn't seem to bother it......

Greg
36 pound thrust Avonds F-15 wow..now thats a jet !!!

Thanks for the info gbmoore good stuff.
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Old Mar 28, 2012, 11:18 PM
Capt. Z
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Welcome aboard rcnats great to have ya!!!
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Old Mar 28, 2012, 11:48 PM
A Texan abroad
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Joined Oct 2011
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Quote:
Originally Posted by rcnats View Post
I just found this thread!!! Oh the memories!!! I live 12 miles from Columbus Air Force Base where Air Force pilots are trained and the T-38 is their advanced trainer. I'm retired now but here are some pics of my "VIP" flight . I too will build a T-38 one day. Here's my documentation too!. Keep up the outstanding work!!!
Awesome dude! RC planes are great, but when you get guys who flew the real deal, it gets that much sweeter!
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Old Mar 29, 2012, 12:11 AM
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Colorado Springs, Co
Joined May 2002
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Quote:
Originally Posted by falcon5 View Post
36 pound thrust Avonds F-15 wow..now thats a jet !!!
.
Yeh ... it's fun
just finished an evening with the neighbor-kid (now 1st year masters in Aero at Univ. of Colorado) talking about pivot points.....
When CU did the DreamChaser for NASA, the pivot point was placed about 5% in front of MAC (which rang a bell from the thread I mentioned earlier).
When we took the stab from my (lamented) Tam's F-16, the pivot point was about 48% of the root, which calculated to about 20-21% of MAC.
He (of course) was talking about the Beta movements and the ??? factors, of which I only understood the Greek word "Beta"......
Soooo........looks like both of your stabs are in the ball park.
Keep up the PHENOMENAL work!
Greg
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Old Mar 29, 2012, 07:52 AM
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Geelong, Victoria, Australia
Joined Mar 2004
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Quote:
Originally Posted by falcon5 View Post
Here ya go kripto, took it outside for the first time. Not quite sooo masive as it looks in the house.
What can be said that hasn't already been said??? It looks completely massive outside!! Thankyou for the pictures. I have been planning on building a twin 64mm F5 to similar specs as Brent's original 62" version, but now, I dunno, the 38 is one sweet bird too

Cheers
Steve
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Old Mar 29, 2012, 08:13 AM
Now in TN!
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Chapel Hill, TN USA
Joined Apr 2001
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Wow, looking super Andy! Sure looks like that forward pivot point is going to take a ton of weight to balance, isn't it?

J
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Old Mar 29, 2012, 09:09 AM
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United States, TX, Grand Prairie
Joined Nov 2005
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Quote:
Originally Posted by gbmoore View Post
... 36 pounds of thrust doesn't seem to bother it......

Greg
Got any vids of this flying?!
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Old Mar 29, 2012, 10:36 AM
michigan jet guy
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USA, MI, Caledonia
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been quietly lurking in the background. One of the best builds i've seen yet. Right up there with some others i've seen. Outstanding. Phil
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Old Mar 29, 2012, 11:19 AM
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United States, IL, Edwardsville
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I get 42% back from the leading edge at the root for 25% MAC and 38% back from leading edge at the root for 20% MAC.
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Old Mar 29, 2012, 11:44 AM
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Oshkosh, WI
Joined Nov 2002
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I'm sure most of you folks know how to do this. But my curiousity got me to lay down some lines. Looks like 25%MAC is about 45% from L/E of root chord. The Panel plan view CG is just shy of 2" behind the 25%MAC point, so a bit of wt may be needed to balance the panel; not as much as the panel wt*1.973/x, since the panel has more thickness around the 25% pt than toward the T/E.

Hope this saves some time

Phil
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Old Mar 29, 2012, 12:27 PM
Capt. Z
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United States, NV, Las Vegas
Joined Dec 2004
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All great info, thanks guys. Well I may just fly it with the current stabs and use caution for the first dozen or so high speed runs to check things out.
I will add some weight in the ones I have and give it a go

Thanks Nut for the good catch on this issue and all the great input from the crew.
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