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50cc 260 Tipstall Happy? - 8/11/2007 12:43:02 AM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		I have a 260 set up with all throws by the book. The CG is 3.5" back from the leading edge as measured at the wingtips. Seems that the plane will tip stall at speed when about 75% of low rate elevator is applied. This happens at speed. Is this normal?

Also, where do you like the CG at? I'm thinking I could push it back about 1/2".

Input welcome.
       Post #: 1

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:46:35 AM   
reyn3545



Posts: 994
Joined: 7/1/2006
From: Alpharetta, GA, USA
Status: offline 		I can't imagine how you're getting a wing to lose lift if you have any speed at all on the plane. If you're straight and level, elevator should do nothing but climb straight up... maybe slightly to one side if you don't have the engine and control surfaces dialed in exactly.

(in reply to shall36)
       Post #: 2

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:50:32 AM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		you can stall a wing at any speed if the angle of attack changes to quickly relative to airflow (the engineers will all jump in now for sure). Basically, I can be in level flight at speed and if I pull back too much to fast, it will snap out of track.

(in reply to reyn3545)
       Post #: 3

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:50:53 AM   
bubbagates



Posts: 8162
Joined: 5/30/2004
From: Elizabethtown, PA, USA
Status: offline 		Does it do it to the same side everytime? If so then it could be lateral balance or the elevators are not either moving at eaxctly the same time or not equally as much

_____________________________

Bill James
Normal is not something to aspire to, it's something to get away from

(in reply to reyn3545)
       Post #: 4

RE: 50cc 260 Tipstall Happy? - 8/11/2007 2:22:58 AM   
reyn3545



Posts: 994
Joined: 7/1/2006
From: Alpharetta, GA, USA
Status: offline 		But you mentioned that you are using only 75% of low rate elevator. If that's the case, you shouldn't be falling off...

Have you taken time to dial in each elevator half? One may be lifting slightly higher. Also, as posted earlier, lateral balance will become a factor as the wings lose lift.

When you slow the plane to a very slow, but level flight, does it want to fall off to one side? Or, when your plane is sitting on the ground and your hands are off the sticks... do you have any more than just a touch of aileron dialed in? If so, you might consider lateral balance as a culprit.

If you only see a problem when you add elevator, I would look there for a problem. If they aren't lifting equally, you could see the plane snap to one side.

You might also look at the incidence on your rear stabs. You could have adjusted the problem out for straight and level flight, but when you add elevator, you change the rules of the game again. That's a longshot, and if your elevator halves are pretty much lined up with the stabs when the plane is "hands off" on the ground, its probably not an issue.

Another "longshot".. if you have expo dialed into the elevators... make sure the expo is set the same for both elevator servos.

To identify necessary balance or control adjustments, take the plane through very slow climbs to vertical, very slow rolls to an inverted 45 degree climb, slow aileron rolls, and other standard moves, but make them very slow. You'll see pretty quickly the adjustments that need to be made to make your plane respond properly when you want to bend the sticks.

There's a pretty thorough run-down on trimming in a plane at troubuiltmodels.com. I don't know anyone that actually goes through the level of detail that they suggest, but reading it and "picking your 7 favorite commandments to follow" will give you a very good tracking plane.

< Message edited by reyn3545 -- 8/11/2007 2:25:07 AM >

(in reply to bubbagates)
       Post #: 5

RE: 50cc 260 Tipstall Happy? - 8/11/2007 3:49:04 AM   
Grelker



Posts: 200
Joined: 8/28/2004
From: Bellevue, WA, USA
Status: offline 		Mine does the same thing, but only on high rates. It always drops to the right AND it only does it if I pull instantaneously. Rapid pulls it doesn't happen. Reyn maybe on the right track with uneven elevators....

_____________________________

Jon N.

(in reply to reyn3545)
       Post #: 6

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:48:42 PM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		Thanks for all the input guys!

If I had to guess, I'd say it snaps off to the right most of the time.

I spent a lot of time dialing in the elevators at both full and partial throws. That took a LOT of time. I'm using the 8103 and it's not the best radio out there for split elevators, at least that's my opinion. I was able to get them as close as possible using the throw meter that came with the plane. I'll download the setup guide and give things a look over.

I have done big and small inside and outside loops and the plane seems to track pretty well. It doesn't corkscrew out either way. I wouldn't be surprised if the lateral balance is off, but I just don't seem to be sensitive enough to note which way it is off.


I should be out flying again today, so I'll report back on findings.

(in reply to Grelker)
       Post #: 7

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:53:00 PM   
reyn3545



Posts: 994
Joined: 7/1/2006
From: Alpharetta, GA, USA
Status: offline 		How's the weather down there? Its been over 100 for the past couple of days in Atlanta... we're supposed to go out again today, but I don't know how long I'm going to put up with that kind of heat.

Good luck in the air.

(in reply to shall36)
       Post #: 8

RE: 50cc 260 Tipstall Happy? - 8/11/2007 12:57:38 PM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		It's very hot....very. I take a lot of water and wear a towel on my head. I can usually last about 2 hours. It's been a little less humid than normal, so that's a relief, but it's still above 95* in the shade. The Extra doesn't seem to mind the heat (although I haven't flown in it cold weather, yet), but my Raptor 50 Heli can tell!

(in reply to reyn3545)
       Post #: 9

RE: 50cc 260 Tipstall Happy? - 8/11/2007 1:19:39 PM   
reyn3545



Posts: 994
Joined: 7/1/2006
From: Alpharetta, GA, USA
Status: offline 		I never thought about that... I bet the helis do become a handful when the air thins out and thermals pop up everywhere!

< Message edited by reyn3545 -- 8/11/2007 1:20:03 PM >

(in reply to shall36)
       Post #: 10

RE: 50cc 260 Tipstall Happy? - 8/11/2007 1:22:03 PM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		Things get unstable and the engines run hot, so you end up going a bit rich and performance suffers even more.

(in reply to reyn3545)
       Post #: 11

RE: 50cc 260 Tipstall Happy? - 8/11/2007 1:42:52 PM   
Grelker



Posts: 200
Joined: 8/28/2004
From: Bellevue, WA, USA
Status: offline 		When I set my elevator halves, I set one half to the throw I want. I have 2 balsa sticks about 18" long that I tape to each elevator half so that they just about meet behind the rudder, a V shape. Take care to put them in the same place on each elevator half. Then I match the other elevator throw and center by matching the sticks to one another. Works everytime and is quick.

_____________________________

Jon N.

(in reply to shall36)
       Post #: 12

RE: 50cc 260 Tipstall Happy? - 8/11/2007 1:43:42 PM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		I know this is a bit off the topic, but I'd like some input on radio choice. I read through some of the stuff on TBM's website and they talk about different flight modes and stuff like that. The 8103 doesn't really support that very well, at least if you plan to keep the land/elevator switch active for flapperons and spoilerons. Right now, I use the mode switch to boost elevator and aileron throws by 125%. When you couple this with dual-rate switches, you end up with 4 levels of throw. As the TBM site says, using the dual-rate switches is cumbersome. The bummer about the mode switch on the 8103 is that it doesn't impact expo. So, you bump up the rate but not the expo.

As I said earlier, setting up the split elevators on the 8103 was a total pain in the neck! I spent over an hour figuring it all out. As some of you have probably seen, when you start messing with the expo, the elevators can move the same total amount at different rates. Very frustrating.

I also noted that TBM talks about a 3-D machine and a sequence machine and they expect that you have one for each. The computer part is easy...just set up a computer profile for each type of flying, but things like CG and downthrust settings are obviously plane-specific.

Any thoughts on radio setup would be appreciated.

(in reply to shall36)
       Post #: 13

RE: 50cc 260 Tipstall Happy? - 8/11/2007 1:47:46 PM   
shall36


 

Posts: 105
Joined: 6/1/2002
From: Orlando, FL, USA
Status: offline 		Cool! Gonna do that! Thanks!

(in reply to Grelker)
       Post #: 14

RE: 50cc 260 Tipstall Happy? - 8/11/2007 2:45:54 PM   
reyn3545



Posts: 994
Joined: 7/1/2006
From: Alpharetta, GA, USA
Status: offline 		The process described above is a good tool to make sure your throws are even. If you want to set "exact" throws (say, 45 degree deflection on high rates)... then you need either a throw meter or a digital incicence meter.

Throw meters are very simple, mechanical devices. Typically, a wooden radius with degree markings, and in the center of it, a needle with a weight on the bottom. You fix it to the control surface (they usually have a clothespin type of clip) and then check the throws as you move the surface. Sounds simple on the surface, but these devices are usually are very tempremental.... friction where the needle bolts through the radius results in inaccurate readings.

Digital incidence meeters can give very precise readings. They range in price anywhere from $50 (Hangar 9) to over $200. I expect you probably get what you pay for. I got the Hangar 9 a year or so ago when I was having problems with my biplane. Its a so-so product for measuring wing incidence, but a GREAT tool for measuring control surface throws. I won't go into a full description of how to use it, but its very simple.... make sure your plane is sitting level, then set the meter on a control surface and zero it. Now move the control surface and note how many degrees it moves. You can also compare the "centered" location of all control surfaces to see if they are fighting against each other.

(in reply to shall36)
       Post #: 15

RE: 50cc 260 Tipstall Happy? -