Go Back  RCU Forums > RC Airplanes > Beginners
Reload this Page >

My trainer seems to dive a lot whn I try to roll it

Notices
Beginners Beginners in RC start here for help.

My trainer seems to dive a lot whn I try to roll it

Old 10-25-2013, 01:00 PM
  #1  
carl24bpool
Senior Member
Thread Starter
 
Join Date: Nov 2004
Location: Blackpool, UNITED KINGDOM
Posts: 287
Likes: 0
Received 1 Like on 1 Post
Default My trainer seems to dive a lot whn I try to roll it

I'm sure my first Ripmax trainer didnt do this. My current plane is identical to the one I had the inverted flight boo boo with.

When I give it some hard aileron to roll the plane has a strong tendency to dive before I can even get inverted. Even a couple of mistakes high it still gets quite low as I'm recovering. If I add in hard forward on teh elevator it keeps the plane level but it just doesn;t seem to roll on a nice axis like my other one did.

Is this likely to be a nose biased C of G, or could my ailerons need a little more movement (extending the throw). ?
Old 10-25-2013, 02:00 PM
  #2  
RCKen
RCU Forum Manager/Admin
My Feedback: (9)
 
RCKen's Avatar
 
Join Date: Jul 2002
Location: Lawton, OK
Posts: 27,581
Likes: 0
Received 25 Likes on 22 Posts
Default

This is normal for most planes. The proper procedure when you roll a plane is to feed in elevator when the plane comes over inverted to keep it level. then as the plane rolls upright you take the elevator back out. Some planes will also require you to feed in rudder as it rolls to keep it straight, but not every plane will need this.

Ken
Old 10-25-2013, 02:31 PM
  #3  
jetmech05
 
Join Date: Jul 2005
Location: Jacksonville, FL
Posts: 4,865
Likes: 0
Received 0 Likes on 0 Posts
Default

As usual Ken has it right.
Old 10-25-2013, 07:00 PM
  #4  
Ed_Moorman
My Feedback: (1)
 
Ed_Moorman's Avatar
 
Join Date: Jan 2002
Location: Shalimar, FL
Posts: 4,059
Likes: 0
Received 1 Like on 1 Post
Default

You are probably holding some up elevator during the roll. In addition, a traIner with a flat bottom airfoil will naturally drop its nose when inverted.

When I wrote the Fun Aerobatics column for R/C Report magazine, I taught a trainer roll. You raise the nose about 20 degrees, release the up elevator, use full aileron to roll, release the aileron stick, use up elevator to level out. The key to the trainer roll is to do the maneuver "by the numbers," 1-2-3. Up release, roll release, up release.
Old 10-25-2013, 08:27 PM
  #5  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,056
Likes: 0
Received 0 Likes on 0 Posts
Cool

Originally Posted by carl24bpool View Post
............Is this likely to be a nose biased C of G, or could my ailerons need a little more movement (extending the throw). ?
Both things may help.
Check how your elevator is trimmed for normal level flight; if noticeably up, you may have the CG too forward or the wing incidence too small and that trim will induce an undesired loop (down) when inverted.

More throw in the ailerons will help adopting the inverted position sooner, allowing the lift generated by the inverted wing in combination with the down elevator input mentioned above.
More throw in the rudder and rudder input while sideways will help less nose down attitude while the wing is vertical respect to the ground (zero lift).

These articles will help you coordinating the proper control inputs of any decent roll:

http://www.rcflightschool.com/Sport_Lessons/E30-31.asp

http://www.rcflightschool.com/Adv_Le...Adv_C10-13.pdf

http://www.modelairplanenews.com/blo...recision-roll/

Last edited by Lnewqban; 10-25-2013 at 08:30 PM.
Old 10-26-2013, 08:11 PM
  #6  
malthepal
Member
My Feedback: (1)
 
Join Date: Nov 2003
Location: North Salt Lake, UT
Posts: 60
Likes: 0
Received 0 Likes on 0 Posts
Default

The man who trained me taught me to "push away from the ground when inverted". In other words, down elevator. It comes pretty easy after a few tries.
Old 10-27-2013, 05:58 AM
  #7  
jester_s1
Moderator
 
Join Date: Dec 2006
Location: Fort Worth, TX
Posts: 7,266
Received 35 Likes on 30 Posts
Default

It sounds like you are losing altitude during the knife edge portions of the roll? That's normal for a trainer. Because of the dihedral, you can't coordinate rudder to hold altitude in knife edge on a trainer, so you have to learn that "trainer roll" mentioned above. When I fly with a trainer and want to see how good I can make it, I actually give it enough of a down elevator bump while inverted to get through the second knife edge portion too. You wind up with an "m" shaped flight path going up before starting, descending until inverted, then bumping up again and descending until upright again. It's a neat challenge to keep that "m" as flat as possible and find the minimum corrections needed to keep from losing any altitude. But like I've told you before, it sounds like your flying skills are good enough to leave trainers behind. If you will get yourself one of the classic sport planes you'll find this aerobatics stuff to be so much easier. An Ugly Stick, 4 Star, Pulse, Easy Sport and a number of others will take away the trainer quirks but will keep the nice low speed handling and landing that you probably still need.
Old 10-27-2013, 06:10 PM
  #8  
Hossfly
 
Hossfly's Avatar
 
Join Date: Dec 2001
Location: New Caney, TX
Posts: 6,130
Likes: 0
Received 2 Likes on 2 Posts
Default

Originally Posted by carl24bpool View Post
I'm sure my first Ripmax trainer didnt do this. My current plane is identical to the one I had the inverted flight boo boo with.

When I give it some hard aileron to roll the plane has a strong tendency to dive before I can even get inverted. Even a couple of mistakes high it still gets quite low as I'm recovering. If I add in hard forward on teh elevator it keeps the plane level but it just doesn;t seem to roll on a nice axis like my other one did.

Is this likely to be a nose biased C of G, or could my ailerons need a little more movement (extending the throw). ?
Your model is an airplane. An airplane reacts to the aerodynamic laws. Grab a piece of paper and start to draw some basics. Draw the end of the airplane going away from you, just a stick drawing to indicate wing, stab, and vertical stabilizer in their proper place. This plane is in trim, so draw an arrow showing each force. There are two forces in this drawing. Given level trim, the up arrow ( lift ) will be equal to the down-arrow (gravity). Now in your mind roll the airplane. Gravity will stay the same force. OTOH, Lift is now slanted because lift is always perpendicular to the lateral axis (wing tip to tip). Therefore the lift axis has two parts in the triangle that results. Since the lift factor has one leg -- the up vector which is now less than the vertical gravity vector. Gravity now is stronger than the lift vector so your airplane is descending which will be the nose starting down and that is the way it is. One of the reasons that pilotsare in damand!
You can add aditional up elevator which will add to the lift vector, however it will increase drag requiring additional power. This is where Prior Planning Prevents PiXs Poor Performance. The 6 Ps for pilots.
30* bank angle requires additional up-force from st. and level. 45* bank angle requires, iirc, 1.5 G. 60* bank requires 2G to sustain level flight. Therefore it is NOT your airplane being bad. It is strictly the pilot that can make things right or cuss the airplane and watch it crash.
Start with a small amount of up-elevator as you start the roll. Using the ailerons to roll and maybe a touch of rudder keep feeding in back pressure until the airplane is going over and then feed in down elevator until the airplane is coming into the right-side-up. As the roll is completeing feed in up elevator to maintain altitude until the model wishes to rise, then reduce aileron while using elevator as needed to keep the altitude. At first your rolls will be somewhat large and kind of like a barrel-roll, Soon you will get ahead of th airplane and your rolls will be so easy, you will wonder what the fuss is about.
When you get this down, and that will be almost right-on, I have another item that can provide a lot of fun. The Barrel Roll. A roll around a point. Much Fun. OTOH it sometimes provides some interesting pilotage, which is much more demanding than the quick aileron roll.

Don't forget: http://www.allstar.fiu.edu/aero/airflylvl3.htm

Last edited by Hossfly; 10-27-2013 at 07:13 PM.
Old 10-28-2013, 01:46 AM
  #9  
carl24bpool
Senior Member
Thread Starter
 
Join Date: Nov 2004
Location: Blackpool, UNITED KINGDOM
Posts: 287
Likes: 0
Received 1 Like on 1 Post
Default

Thank for all the tips guys.

I only raised the issue as my previous Rimpa Trainer (identical to this one) would roll very easily with only aileron.

I think the only real difference can be the rates and the first plane had higher rates and therefore had less chance to lose height during the roll. I'll try upping the rates too as they are a little tame for what I do these days. Perhaps add a little epo to help keep landings smooth.
Old 10-28-2013, 05:12 AM
  #10  
jester_s1
Moderator
 
Join Date: Dec 2006
Location: Fort Worth, TX
Posts: 7,266
Received 35 Likes on 30 Posts
Default

Don't discount the value of tame rates. It doesn't take much skill to whip though a roll in 1 second without bumping into the Earth. The truly good pilots can do a 5+ second roll with no deviation in altitude or heading or pull a 300 foot loop that's perfectly straight and round. More skill does not equal more control throw.
Old 10-28-2013, 06:22 AM
  #11  
Lnewqban
 
Lnewqban's Avatar
 
Join Date: Apr 2007
Location: South Florida
Posts: 4,056
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by carl24bpool View Post
Thank for all the tips guys.

I only raised the issue as my previous Rimpa Trainer (identical to this one) would roll very easily with only aileron.

I think the only real difference can be the rates and the first plane had higher rates and therefore had less chance to lose height during the roll. I'll try upping the rates too as they are a little tame for what I do these days. Perhaps add a little epo to help keep landings smooth.
As Jester has explained, quick rolls only mask lack of skills.
Although your plane will not do pretty axial rolls, you can always practice and learn the fundamental skill of rudder control.

I would increase the throw of the ruder instead and would practice using it as the plane adopts a knife edge attitude during the roll.
My previously posted links explain how-to.

I summary, the inconvenience that you see now could become a reason to practice and master slow rolls, left and right.
Staying within your comfort zone may be safer for your plane, but rarely makes you a better pilot.

Please read these:
http://www.geistware.com/rcmodeling/...some_pilot.htm

http://www.rchawk.com/rudder.htm

http://www.neprcc.org/documents/UsingTheRudder.pdf







Old 10-29-2013, 02:34 AM
  #12  
carl24bpool
Senior Member
Thread Starter
 
Join Date: Nov 2004
Location: Blackpool, UNITED KINGDOM
Posts: 287
Likes: 0
Received 1 Like on 1 Post
Default

Thanks guys.

I think my rudder is at full throws already which is around 25mm each way. It wont really go much more without binding on the tail plane.

I'm going to sick with teh plane for a few more weeks but over winter I'm going to look for a new kit to build. Some sort of low wing trainer. I really liked the Space walker II from seagull models and kinda regret selling it to a friend. My PC-9 is a little fast and more demanding to fly than the Spacewalker was.

I'll have to see what I fancy.

I'll try and master these rolls though. It is definitely much more difficult to be using three inputs at the same time than just using the right stick that's for sure. Especially the right amount of each input!!
Old 10-29-2013, 04:15 AM
  #13  
jester_s1
Moderator
 
Join Date: Dec 2006
Location: Fort Worth, TX
Posts: 7,266
Received 35 Likes on 30 Posts
Default

And you'll find that with a trainer, you have so much roll coupling with the rudder that you'll have to give it more aileron in the first half and almost none in the second half.
Old 10-29-2013, 10:52 AM
  #14  
carl24bpool
Senior Member
Thread Starter
 
Join Date: Nov 2004
Location: Blackpool, UNITED KINGDOM
Posts: 287
Likes: 0
Received 1 Like on 1 Post
Default

Originally Posted by jester_s1 View Post
And you'll find that with a trainer, you have so much roll coupling with the rudder that you'll have to give it more aileron in the first half and almost none in the second half.

lol, just to make things even easier

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.