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Old Dec 06, 2005, 01:10 PM
Pushing the Limits of FFF
wirbech's Avatar
United States, CA, Sierra Madre
Joined Jun 2005
1,167 Posts
Another thing to check is your prop. Make sure that it is on correctly. The writing should face the front of the plane.

John
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Old Dec 06, 2005, 02:24 PM
bigglesjets
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Notts UK
Joined Jul 2005
201 Posts
Hi Submarco

Excellent! I do hope this sorts your problem out, I dont like to see guys disolusioned before they get off the ground,so to speak!

Regards

Alan
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Old Dec 06, 2005, 02:32 PM
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gyronuts's Avatar
York England
Joined Jul 2002
583 Posts
Just a thought but my F15 used to do that. I came to the conclusion that it was the flexing of the depron elevator/elevons at higher speeds which caused the pitch up . At which point the speed reduced and control recovered. The tailplane is very flexible and it does not take much to bend the whole surface and shaft. Bill
PS the nose high pitch up in the picture was not an intentional control input!!!
PPS I had a lot of trouble finding a prop that would give me good vertical performance yet a reasonable turn of speed level.
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Old Dec 07, 2005, 02:17 AM
ViruTs
Denver
Joined Mar 2004
773 Posts
flight report:

yes it was the cg, finally my f-18 flew decently, however, because of the dark I didi crash it. AT this point I think I will make a new one.
I will make sure to balance it on the cg, however, yes Gyronuts reported I think the pitch up is something structurally inherent to those kind of planes, that would make sense when I used to p˛wer system such as the mega 4t, but not so much when it came to the axi 2212/26 or teh bp21. Plus, still thinking on Gyronuts commentaries, yes I think the picking the right prop makes a lot of difference.
I will work on that to.
I plan to work on two projects, a new f-18 and the Cobra's F-20 tigersharck, lets see If I have more luck now.
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Old Dec 07, 2005, 05:36 AM
From Earth to the Moon!
albireo's Avatar
Sacramento, Ca.
Joined Jul 2003
1,518 Posts
This is what I've been looking for Tom. Just to clarify, you mean if the nose lifts when you cut the power you move the battery/weight forward to balance the plane, and if the nose dips down you move the battery/weight back not move the CoG mark on the plane/plans foward or backward, right? That is, you always stick with the CoG measurement mark on the plane/plans and move the CG by shifting weight in the nose...
Joe

Quote:
Originally Posted by RCParkflyer
Sounds like your CG Location is off.

when you fly the plane, cut the power, if the nose lifts your CG is too far back. If the nose dips down, the CG is too far forward, just move it back.

Tom
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Old Dec 07, 2005, 08:15 AM
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RCParkflyer's Avatar
Racine, WI AMA# 809291
Joined Nov 2003
5,856 Posts
Quote:
Originally Posted by albireo
This is what I've been looking for Tom. Just to clarify, you mean if the nose lifts when you cut the power you move the battery/weight forward to balance the plane, and if the nose dips down you move the battery/weight back not move the CoG mark on the plane/plans foward or backward, right? That is, you always stick with the CoG measurement mark on the plane/plans and move the CG by shifting weight in the nose...
Joe
You will end up with a new CG position, but it will be only a slight adjustment, as your pretty close already, your just fine tuning the plane at this point. Once the plane flys level, then you re-balance it, and mark the new CoG spot, then you just balance the plane on that new spot every time you fly.
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Old Dec 07, 2005, 03:28 PM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,133 Posts
Quote:
Originally Posted by submarco
flight report:

yes it was the cg, finally my f-18 flew decently, however, because of the dark I didi crash it. AT this point I think I will make a new one.
I will make sure to balance it on the cg, however, yes Gyronuts reported I think the pitch up is something structurally inherent to those kind of planes, that would make sense when I used to p˛wer system such as the mega 4t, but not so much when it came to the axi 2212/26 or teh bp21. Plus, still thinking on Gyronuts commentaries, yes I think the picking the right prop makes a lot of difference.
I will work on that to.
I plan to work on two projects, a new f-18 and the Cobra's F-20 tigersharck, lets see If I have more luck now.
Sorry to hear about your crash - for the next one try the Axi 2212/26 with a 9*7,5 APC SF prop - Really rocks!!

Ben_E
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Last edited by Ben_E; Dec 07, 2005 at 03:38 PM.
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Old Dec 07, 2005, 09:35 PM
From Earth to the Moon!
albireo's Avatar
Sacramento, Ca.
Joined Jul 2003
1,518 Posts
I'll second that motor reccomendation, I use that exact same setup and my piggie Shumate design F-15 weighs a fat 24 oz and it really hauls - I mean much faster than I can fly it...
Joe
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Old Dec 08, 2005, 04:53 AM
Go FASST or go home...
Ben_E's Avatar
Bergen, Norway
Joined Nov 2002
3,133 Posts
Quote:
Originally Posted by albireo
I'll second that motor reccomendation, I use that exact same setup and my piggie Shumate design F-15 weighs a fat 24 oz and it really hauls - I mean much faster than I can fly it...
Joe
there is nothing like WOT!!

Ben_E
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Old Dec 08, 2005, 09:54 AM
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Wade Joos's Avatar
United States, UT, Salt Lake City
Joined Aug 2002
1,230 Posts
Cg

Guys,
I think either I am reading this wrong or there needs to be some clarification.

"This is what I've been looking for Tom. Just to clarify, you mean if the nose lifts when you cut the power you move the battery/weight forward to balance the plane, and if the nose dips down you move the battery/weight back not move the CoG mark on the plane/plans foward or backward, right? That is, you always stick with the CoG measurement mark on the plane/plans and move the CG by shifting weight in the nose...
Joe"

This would be the test for thrust line.
If the plane changes pitch - either up or down with throttle changes, then it is the thrust line of the motor that is incorrect.

To check for proper CG, set up the plane for level flight, then roll it over on its back. If the plane dives toward the ground it is nose heavy, if it pitches up, then it is tail heavy.
A nose heavy condition can also be detected by looking at where the elevator is trimmed for level flight. If the elevator has a lot of up" or "down", then the CG balance needs to be adjusted.
The maked "CG" spot on the plans is just a suggested starting point. Each plane may be a bit different from that location.
Once you have the plane flying normal and inverted with little input change required from the elevator, then that will be your correct CG location. Once you have found the sweet spot, put a mark on the plane & use that as a balance point from then on.
I hope this makes sense & helps
Later
Wade
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