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Old Sep 09, 2009, 06:31 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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Hey Micbu, I read somewhere in one of these threads another guy had his CG farther back than 78mm. Does it increase the sensitivity to roll when you balance back farther?
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Old Sep 09, 2009, 08:32 AM
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I can not compare the sensitivity to a SR-71 with the CG at 78mm because it is
just impossible to fly with that CG.
There is not enough sub-trim to keep the plane leveled. You always have to keep
the stick pulled back for about 50% of its way.
There are several people here who confirmed that. I can absolutely not understand,
that you guys fly with CG at 78mm.

Michael
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Old Sep 09, 2009, 11:33 PM
On the Edge of Space
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Exit 4, South Jersey, USA
Joined Dec 2007
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I just add a good deal of up trim mechanically, the rear tips of the elevons are 5mm above the top surface of the wing when the servos are centered. It's just like having a reflexive trailing edge and is pretty common on deltas.
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Old Sep 10, 2009, 01:42 AM
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Hi,
i did the same. The rear tips of the elevons are about 5mm up.

Michael
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Old Sep 12, 2009, 11:24 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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How much up deflection do you have? On mine, the elevon tip travels up another 22 mm from neutral stick. I have giant gobs of up set up mechanically.

I banged mine up last week. Lost orientation, too close to public areas, nosed it over into the woods.

Submitted for your enjoyment:
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Old Sep 20, 2009, 05:24 PM
Clear Skies & Contrails
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Edwards AFB, CA
Joined May 2009
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Airframe Only on Sale!

Banana Hobby has the "Airframe Only" on Sale for $99.90.

http://www.bananahobby.com/1801.html

Best,
Tony
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Old Sep 21, 2009, 09:58 PM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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Thanks for the link. I got this one back together and its flown pretty well the last two weeks. I lined the inlet side tubes with manila folders and it makes a really cool whooshing noise now. Debating whether to get a new airframe or just keep flyin it ugly.
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Old Oct 04, 2009, 06:35 PM
On the Edge of Space
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Exit 4, South Jersey, USA
Joined Dec 2007
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A few pics. Manila folder thrust tubes. Zip ties hold em on. If it only looked as good as it sounds.
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Old Oct 19, 2009, 03:20 PM
Build'm,Fly'm,Crash'm
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Sacramento CA
Joined Oct 2009
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Man, that is one war-horse! I guess you have a pretty good idea why 1/3 the production run was destroyed in accidents on the original SR. The flat black is more realistic than the factory finish, though. I've been reading this thread with interest as I have an airframe still in the box. I'll be building this winter, so I may have some questions, if you don't mind? BTW, I have a 20 gram vidieo camera that is begging to go 'spying', what better plane than this? After this thread, I'm not so sure.....Thanks for your input, all of you, on this thread....

Regards, Joe..
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Old Oct 20, 2009, 10:18 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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Greetings Joe.
Yeah, it's ugly! Its a wonder its still in one piece considering it was kind of a test-bed for 3 different power setups, gyro experiments, and test mule for my first computer radio. It does share some of the same problems with the full scale, e.g. wing rocking and poor response to nose high stall. It flies really well though once set up acceptably and flown within its intended flight parameters, in fact I judge it easy to fly.

Maybe the appearance will get some attention this winter. I'll keep the flat black, I think a lot of them were flat black with minimal markings.

Good luck with your build and flights, it'd be great to see some surveillance video! I'll be happy to talk about this bird all you want, it's my favorite.

PS - Another good thread: http://www.rcgroups.com/forums/showthread.php?t=958592
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Old Oct 20, 2009, 11:05 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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Quote:
Originally Posted by micbu
I can not compare the sensitivity to a SR-71 with the CG at 78mm because it is
just impossible to fly with that CG.
There is not enough sub-trim to keep the plane leveled. You always have to keep
the stick pulled back for about 50% of its way.
There are several people here who confirmed that. I can absolutely not understand,
that you guys fly with CG at 78mm.

Michael
Michael, I see the root of our differing observations now. As an experiment, I moved the CG back to 85mm from 78mm and found that the model wanted to climb at neutral stick, requiring down trim and less mechanical reflex (reflex = up elevon at neutral stick). The only difference after adjustments was that the turn radius decreased and pitch sensitivity increased. So, the usual rules apply - if the CG is more forward, the craft is less aerobatic and you will need more elevator movement; if the CG is farther back, the craft is more aerobatic and you need less elevator motion. It is noteworthy that this relatively small change in CG required significant pitch control adjustments.
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Old Oct 20, 2009, 04:12 PM
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Well, less mechanical reflex means less resistance to the air.
The nose does not point towards the sky while flying horizontal.
That means more speed and less power consumption.
What would be the better choice?

Michael
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Old Oct 20, 2009, 10:11 PM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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The better choice depends on what you want to do with your aircraft. There are pluses and minuses to compromise; stall characteristics, maneuverability, wind penetration and sink rate come to mind. There is always a trade off involved.

I don't think I agree that a plane with a forward CG flies with a nose high attitude. On a very nose heavy plane (forward CG), the elevator cannot change the sum of vectors enough to lift the nose from the ground. On a very tail heavy plane (aft CG), the elevator cannot change the sum of vectors enough to push the nose down, so the angle of attack of the wing is too great. The wing cannot generate lift.

In any case, I absolutely agree that with the manufacturers spec of 78mm, you will be pulling a LOT of back stick for 50% of the flight unless you have enough reflex and elevator throw.
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Old Oct 24, 2009, 01:02 AM
Chef, Snowboarder, WEEEE!
Latham NY
Joined Apr 2007
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OK, so STOCK flight times with the majority of it WOT would be >?

I still have not seen a stat posted about how long the stock setup runs.
\
Also is it the same from BH as the Easytiger ?

http://easytigermodels.com/index.php...edbd0b43ebf047

I don't see replacement parts available for this jet, si I assume U break, you buy (another).
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Old Oct 24, 2009, 07:30 AM
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United States, FL, Sebring
Joined Feb 2006
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Quote:
Originally Posted by DaveESPI
OK, so STOCK flight times with the majority of it WOT would be >?

I still have not seen a stat posted about how long the stock setup runs.
\
Also is it the same from BH as the Easytiger ?

http://easytigermodels.com/index.php...edbd0b43ebf047

I don't see replacement parts available for this jet, si I assume U break, you buy (another).

It seem like everyone sells this jet. banana Hobby, nitroplanes, eazytiger, etc.
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