Crash & Rebuild Post your crash stories, pictures and if you want to document your rebuild you can do that here too!

Piper Cub 1/4 left rolled on take off. PLS HELP

Reply
Old 08-23-2013, 01:23 AM
  #1
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Piper Cub 1/4 left rolled on take off. PLS HELP

[TABLE="class: tborder user-postbit-left-user, width: 100%, align: center"]
[TR]
[/TR]
[TR]
[TD="class: alt2"]Hi Guys,

I have made a Piper Cub J3 1/4 scale with DLE 20 mounted on it. During my maiden flight plane was taxing well, ailerons, elevator and rudder were all levelled.
As soon as plane took off, plane took a hard left turn and rolled left.

Any expert guidance what needs to be checked. I have already balanced the plane with correct cg.

Thanks & Regards,
Anilesh
[/TD]
[/TR]
[TR]
[TD="class: user-postbit-bottom-user, bgcolor: #404040"]



[/TD]
[/TR]
[/TABLE]
anileshrai is offline  
Reply With Quote
Old 08-23-2013, 01:28 AM
  #2
4*60
 
Join Date: Mar 2002
Location: Shuswap, BC,
Posts: 1,738
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Possibly you took off too soon. Common problem. You need to do a takeoff roll and make sure no up elevator. Let it get up to speed brfore lifting off. At low speed the ailerons have no real effect and you cannot stop this if too slow.
4*60 is offline  
Reply With Quote
Old 08-23-2013, 02:55 AM
  #3
sensei
 
sensei's Avatar
 
Join Date: Jul 2002
Location: SAN ANTONIO, TX
Posts: 2,630
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

You did not state that the nose pitched up and then rolled to the left, so check your wing for any twist issues.

Bob
sensei is offline  
Reply With Quote
Old 08-23-2013, 03:21 AM
  #4
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks 4*60 and Bob, yes nose was pitched up and then it performed a cartwheel on the left as soon as it took off the ground. Kindly advise how to check the thrust line or any modifications to be done, is there any possibility that my thrust line is offset, if required i can post pictures of the engine mount.
anileshrai is offline  
Reply With Quote
Old 08-23-2013, 04:36 AM
  #5
flyinwalenda
 
flyinwalenda's Avatar
 
Join Date: Oct 2009
Location: Northeast, PA
Posts: 3,699
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Sounds like a typical Cub lifting a little too early. You always need to be ready on the rudder to keep it straight. Cubs are not trainers like most think !
flyinwalenda is offline  
Reply With Quote
Old 08-23-2013, 06:14 AM
  #6
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks brian, is there any need to give any right thrust or should i again try with longer run at full throttle?
anileshrai is offline  
Reply With Quote
Old 08-23-2013, 10:15 AM
  #7
flyinwalenda
 
flyinwalenda's Avatar
 
Join Date: Oct 2009
Location: Northeast, PA
Posts: 3,699
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I'm no expert but I do know you can't "horse" a Cub into the air and you don't "drag race" it down the runway either. Nice and easy taxi and rollout until the tail wheel lifts then gradually increase power and it should lift off on it's own provided the control surfaces where adjusted neutral . You should be on the rudder to keep it straight while on the ground and as it lifts off be ready to add some right rudder if needed. Then increase power and fly it out. If the plane was built correctly you should go with the stock settings and alignment. Once in the air and trimmed see now it flies and takes-off,
flyinwalenda is offline  
Reply With Quote
Old 08-23-2013, 07:14 PM
  #8
jester_s1
Moderator
 
Join Date: Dec 2006
Location: Fort Worth, TX
Posts: 6,171
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

That sounds like a tip stall. As others are saying, it would be caused by letting the plane get lifted off the ground before raising the tail and gaining enough airspeed to fly. It's easier to make that mistake if your landing gear is too far forward since that makes it harder for the tail to come up.
jester_s1 is offline  
Reply With Quote
Old 08-24-2013, 10:54 AM
  #9
4*60
 
Join Date: Mar 2002
Location: Shuswap, BC,
Posts: 1,738
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I would try again with a longer ground roll and more speed before liftoff.
4*60 is offline  
Reply With Quote
Old 08-31-2013, 03:31 PM
  #10
biam
 
biam's Avatar
 
Join Date: Jun 2004
Location: desloge, MO
Posts: 251
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Quote:
Originally Posted by flyinwalenda View Post
I'm no expert but I do know you can't "horse" a Cub into the air and you don't "drag race" it down the runway either. Nice and easy taxi and rollout until the tail wheel lifts then gradually increase power and it should lift off on it's own provided the control surfaces where adjusted neutral . You should be on the rudder to keep it straight while on the ground and as it lifts off be ready to add some right rudder if needed. Then increase power and fly it out. If the plane was built correctly you should go with the stock settings and alignment. Once in the air and trimmed see now it flies and takes-off,
well said! Cubs need to be handled like fine women, nice and easy. Gently coaxed in to the air, and then thoroughly enjoyed while slowly flying around at a scale speed! Try this approach and have fun!
biam is offline  
Reply With Quote
Old 11-30-2013, 03:52 PM
  #11
airzona
 
Join Date: Oct 2007
Location: riverview, MI
Posts: 59
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

More ground speed, right rudder, add elevator once tail comes up, shallow takeoff climb.
airzona is offline  
Reply With Quote
Old 12-12-2013, 06:30 AM
  #12
bikerbc
 
Join Date: Jan 2011
Location: SorrentoBritish Columbia, CANADA
Posts: 2,018
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

As the other have said this is a problem common to Cubs caused by lifting off too early ..You need to let it build up more speed and let it lift itself off . Its not a bad idea to let somebody who is familiar with Cubs take it up for you the first time and get it trimmed out because they can be a real handful until you get used to them . They Are not a trainer although they will teach you a lot about flying . When taking off remember to use your rudder .
bikerbc is offline  
Reply With Quote
Old 12-15-2013, 10:35 AM
  #13
mazzea117
 
Join Date: Jan 2006
Location: Deer Park, NY
Posts: 1
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I have a 1/4 scale cub, you need to ADD slight down elevator to keep from lifting off ground too soon! This will bring tail wheel off ground sooner and decrease angle of attack, just ease into throttle to full. Just watch plane, keep level, build up AIR SPEED on the ground, then just pull back on elevator, SLIGHTLY, and watch a beautiful scale-like take-off. Just remember, the cub will ALWAYS want to take off too soon, Your the pilot, not the other way around! Good luck, and enjoy
































j
mazzea117 is offline  
Reply With Quote
Old 12-15-2013, 11:05 AM
  #14
JPMacG
 
Join Date: Jan 2002
Location: Ivyland, PA
Posts: 2,260
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Exactly. Down elevator to bring the tail up to a horizontal position and hold it there while you gain speed. Then, slight up elevator to lift it off the ground and be ready to correct with rudder when it breaks ground.

Last edited by JPMacG; 12-15-2013 at 11:08 AM.
JPMacG is offline  
Reply With Quote
Old 01-24-2014, 07:50 PM
  #15
John_M_
 
John_M_'s Avatar
 
Join Date: Jan 2014
Posts: 1,200
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Definitely make sure your tailwheel is set true and straight... so when you push the plane along the ground with the radio on, and NO engine running, it should rolls straight ahead, and doesn't have the tendency to roll to the right or left (not even the slightest amount)... I know it may sound odd, but having the the tailwheel set correctly will allow you to slowly advance the throttle as the plane picks up airspeed... then once the airspeed reaches the point the tail lifts up, there's enough air flow over the vertical fin and rudder to help keep the plane pointing into the wind... then all you'll need to do is make small corrections on the rudder as needed.

The biggest mistake I've seen is to slam the throttle stick to full on takeoff, and then there's sooo much torque roll, the plane dives to the left; then you over control trying to correct with the rudder... you're too busy fighting the rudder, you forget about the elevator, the plane jumps into the air too soon, and you end up with a stall / snap roll into the ground.

Also abort the takeoff if the plane gets squirrel on the ground... once it gets squirrel like that, all you're going to do is make it worse by over correcting... I'd rather abort the takeoff, and run off the side of the runway into the weeds, than to pick up the pieces from a stall / snap roll on take off.

John M,
John_M_ is offline  
Reply With Quote
Old 01-27-2014, 12:54 AM
  #16
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Hi Guys,

Thanks for your help and suggestion.

I need some more help, I have installed DLE 20 gas engine in my 1/4 J3 Cub. I have break in the engine by flying without cowl turning Xoar 16x8 prop at 7600 rpm. Engine is giving great performance.I have now installed the cowl on this plane and have observed engine's rpm is dipping to 6800 RPM as I am new gassers please help me to rectify this problem. Is it due to over heating or may be my cowl is not letting air to pass in.

Expert advices are most welcome.

Anilesh
anileshrai is offline  
Reply With Quote
Old 01-27-2014, 09:24 AM
  #17
PiperDriver
 
Join Date: Nov 2002
Location: Rolling Meadows, IL
Posts: 16
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Done the same thing with my Sig 1/4 clipped wing. Not enough airspeed on takeoff. Jerked it off and rolled into the ground. Airframe weight has more effect on this slower airplane than you might think. In process of rebuilding mine after the last mishap like this.
PiperDriver is offline  
Reply With Quote
Old 01-27-2014, 09:46 AM
  #18
flyinwalenda
 
flyinwalenda's Avatar
 
Join Date: Oct 2009
Location: Northeast, PA
Posts: 3,699
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Quote:
Originally Posted by anileshrai View Post
Hi Guys,

Thanks for your help and suggestion.

I need some more help, I have installed DLE 20 gas engine in my 1/4 J3 Cub. I have break in the engine by flying without cowl turning Xoar 16x8 prop at 7600 rpm. Engine is giving great performance.I have now installed the cowl on this plane and have observed engine's rpm is dipping to 6800 RPM as I am new gassers please help me to rectify this problem. Is it due to over heating or may be my cowl is not letting air to pass in.

Expert advices are most welcome.

Anilesh
Overheating would/could be the cause. A cowl will cause overheating if there is not enough air flowing through and around the head. Remember the exit hole(s) in the rear of the cowl should be around 1.5 times the size of the inlet hole(s). You also may need to install baffles to direct the air over the head. Without seeing the installed cowl it's difficult to determine.

Also if there is a spinner attached it could be blocking a good amount of the inlet air.

Last edited by flyinwalenda; 01-27-2014 at 09:51 AM.
flyinwalenda is offline  
Reply With Quote
Old 01-27-2014, 09:51 AM
  #19
RCPAUL
 
Join Date: Dec 2001
Location: Gahanna, OH
Posts: 1,106
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Laterally balancing any airplane is a good thing to do.
RCPAUL is offline  
Reply With Quote
Old 01-27-2014, 12:16 PM
  #20
John_M_
 
John_M_'s Avatar
 
Join Date: Jan 2014
Posts: 1,200
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Quote:
Originally Posted by anileshrai View Post
Hi Guys,Thanks for your help and suggestion.I need some more help, I have installed DLE 20 gas engine in my 1/4 J3 Cub. I have break in the engine by flying without cowl turning Xoar 16x8 prop at 7600 rpm. Engine is giving great performance.I have now installed the cowl on this plane and have observed engine's rpm is dipping to 6800 RPM as I am new gassers please help me to rectify this problem. Is it due to over heating or may be my cowl is not letting air to pass in. Expert advices are most welcome.Anilesh
If your cowl has the plastic dummy engines and air scoops on the sides, cut large openings where the plastic scoops and dummy engine faces the propeller... then open a large opening at the bottom of the cowl to allow the air to exit... on my 1/4 sig cub, I had the simulated air filter housing cut open as well to allow more airflow into the cowl.

I'm in the process now of adding an os ft-160 twin and will be adding the air scoops over each cylinder (like the real thing) and then cut a fairly large opening at the bottom of the cowl.

With the DLE 20 gas engine, since the majority of the engine is inside the cowl, you'll want to make sure you direct a good flow of air from the openings you cut in the cowl, and direct the airflow over the cooling fins on the DLE 20... you can use some 1/8 ply glued inside the cowl to direct the air flow onto the DLE 20 cylinder head... when the plane is flying in the air; the air will be force inside the cowl, so you don't want the air pressure to build up inside the cowl; you want the air to move as freely as possible through the openings in the front and out the bottom, so just make sure you have a big enough exit hole at the bottom of the cowl to allow the air to exit... do this while keeping the strength and integrate of the cowl intact (re-enforce as needed).

John M,

Last edited by John_M_; 01-27-2014 at 12:19 PM.
John_M_ is offline  
Reply With Quote
Old 01-27-2014, 01:11 PM
  #21
John_M_
 
John_M_'s Avatar
 
Join Date: Jan 2014
Posts: 1,200
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Here's some images of what someone else has done with their DLE-20.... doesn't look too bad at all... doesn't take much to keep things cool

.http://www.rcgroups.com/forums/showp...7&postcount=15



John M,
John_M_ is offline  
Reply With Quote
Old 02-10-2014, 04:42 AM
  #22
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Hi Guys,

Please find the pictures of my cowl and please do suggest what can be done for better cooling as engine rpm is decreasing as soon as i put on the cowl may be its heating up.


I have already cut a big slot in firewall for better opening and have even given spacers in mount.

Should i go for vent hole mod or should i cut more cowl. How can baffle this cowl. Any Idea?

Waiting for your earlier response.

Thanks & Regards,
Anilesh



Attached Thumbnails
Click image for larger version

Name:	IMAG0833.jpg
Views:	88
Size:	63.9 KB
ID:	1967140   Click image for larger version

Name:	IMAG0832.jpg
Views:	58
Size:	55.8 KB
ID:	1967141   Click image for larger version

Name:	IMAG0835.jpg
Views:	76
Size:	98.4 KB
ID:	1967142   Click image for larger version

Name:	IMAG0837.jpg
Views:	68
Size:	69.3 KB
ID:	1967143   Click image for larger version

Name:	IMAG0843 - Copy.jpg
Views:	51
Size:	46.3 KB
ID:	1967144  
anileshrai is offline  
Reply With Quote
Old 02-10-2014, 05:40 AM
  #23
flyinwalenda
 
flyinwalenda's Avatar
 
Join Date: Oct 2009
Location: Northeast, PA
Posts: 3,699
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

In my opinion the opening is not large enough in the front of the cowl. I would make two cuts on each side of the rectangular opening down to the small hole at the bottom making a diamond shape opening. If it still gets hot you could make that opening a bit larger . You can also glue some small flat pieces of plywood or plastic inside to make a baffle to direct the air down toward the cylinder.
flyinwalenda is offline  
Reply With Quote
Old 02-11-2014, 09:49 AM
  #24
FlyerInOKC
 
FlyerInOKC's Avatar
 
Join Date: Nov 2004
Location: Oklahoma City, OK
Posts: 7,907
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

If anything you could have the bottom opening started too far forward allowing the air to exit before going over the engine fins. Air is like water it follows the path of least resistance. If it hits the engine and has a place to go it will exit rather than go around the engine. I would close the front of the opening and add a baffle to force the air to go thru the cooling fins. This is done by adding a piece cut close to the engine leaving a small gap around the cooling fins for the air go thru. You want to force the air to travel over the engine's cooling fins before it can escape carrying the engine heat with it.
FlyerInOKC is offline  
Reply With Quote
Old 02-13-2014, 11:00 AM
  #25
anileshrai
Thread Starter
 
Join Date: Aug 2012
Location: Ludhiana
Posts: 7
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks for your response.

I would really appreciate if you can post some pictures showing your cowl.

Kind Regards,
Anilesh
anileshrai is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

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



All times are GMT -8. The time now is 08:54 PM.