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

What do you think about JETLEGEND L39?

RC Jets Discuss RC jets in this forum plus rc turbines and ducted fan power systems

What do you think about JETLEGEND L39?

Reply

Old 08-19-2019, 05:17 AM
  #1926  
joeflyer
My Feedback: (47)
 
Join Date: Dec 2001
Location: Plymouth, MI
Posts: 2,812
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Brian,

What is your take off flap setting now?
joeflyer is online now  
Reply With Quote
Old 08-19-2019, 06:53 AM
  #1927  
belb99
 
Join Date: Feb 2017
Location: Grimsby UK
Posts: 18
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I will measure up this weekend and post, but it's around 50mm down flap but will confirm.

my mate has the mark 1 version and it was interesting to note that the mark 1 has its nose leg mounted lower in the fuze so nose is higher up on his than mine.

belb99 is offline  
Reply With Quote
Old 08-19-2019, 06:59 AM
  #1928  
joeflyer
My Feedback: (47)
 
Join Date: Dec 2001
Location: Plymouth, MI
Posts: 2,812
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Yes, I think Jet Legend screwed up. The nose strut needs to be at least 1/2 inch longer.
joeflyer is online now  
Reply With Quote
Old 10-19-2019, 03:34 PM
  #1929  
rcflier53
My Feedback: (7)
 
Join Date: Feb 2004
Location: Ft Mill SC
Posts: 46
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Maidened my BVM/JL L-39 this week, and my gosh it was a handful. First of all, the nose down is really tough to overcome on a grass strip with this particular nose gear. After a long takeoff roll, it jumped off the ground and almost stalled and snapped when it did finally get airborne. Secondly, it flew heavy and almost uncontrollable at times, like a high wing load warbird. I flew BVMís demo L-39 plane and it was beautiful to fly! Not sure whatís going on with this particular airframe as it was set up exactly like theirs. After the flights, I made some changes to throws and expo, along with adding a spacer in the strut to stiffen the spring. Flew it again and it still canít get off the grass very well. Did the jump into the air again, but luckily I was ready. 3rd flight, I made the mistake of adding smoke fluid and that increased the takeoff roll quite a bit and it flew even worse. Seems like the smoke tank is about 96oz or something. Itís huge and I only filled it 1/3-1/2 way. I am running a JC Cheetah, with an AS3000 gyro and the recommenced throws and expo. CG is almost exactly at the factory placement. I have purchased a CortexPro to replace that AS3000 as Iím not keen on itís functionality in a Jet. Some people like it and others have felt itís not really locked in as well a CortexPro. So, Iím willing to do whatever to get this model to fly well. Any tips or suggestions are welcomed. Itís a pretty airframe and the build quality is nice. Just not a great flier yet. Thanks in advance!
rcflier53 is offline  
Reply With Quote
Old 10-20-2019, 12:08 AM
  #1930  
belb99
 
Join Date: Feb 2017
Location: Grimsby UK
Posts: 18
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Had the same issues on grass as you, would not rotate and lift off smooth , I added spacer in the nose leg to stiffen it up, eventually kept putting more take off flap in and this helped it lift off better, I was going to try to fit weaker springs in the main legs to it sits down at the back more I'm sure this would help it no end.

unfortunately after 5 flights I add a high speed stall it recovered but clipped a tree and is totalled. I've ordered a replacement and intend to lengthen the nose leg this time and cut the fuze to allow wheel to retract.
hope you get the better of it as they are such a nice plane to fly, other than the high speed stall mine flew fine it was just the take off I think JL should have designed the angle of the plane to sit flat.

Brian
belb99 is offline  
Reply With Quote
Old 10-20-2019, 03:02 AM
  #1931  
madmodelman
 
madmodelman's Avatar
 
Join Date: Oct 2006
Location: Corby, Northants, UNITED KINGDOM
Posts: 2,205
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

The rear springs are already soft, on tarmac there is no problem, on grass the nose leg is pulled back creating a negative incidence on the wing.

Cure is to use stiffer nose leg spring.
madmodelman is offline  
Reply With Quote
Old 10-20-2019, 03:27 AM
  #1932  
belb99
 
Join Date: Feb 2017
Location: Grimsby UK
Posts: 18
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

My friend has the early version and the main springs are a lot softer than my latest version was, even with a stiffer spring in the nose leg the plane still sits nose down and compresses the front leg on take off on grass and Tarmac , there is about 20mm difference in the height on the nose between the two models, his takes off smooth and just rotates easy were mine did not but as I said before more take off flap did help.
belb99 is offline  
Reply With Quote
Old 10-20-2019, 04:14 AM
  #1933  
Bob_B
My Feedback: (11)
 
Bob_B's Avatar
 
Join Date: Nov 2003
Location: Bluegrass State of Mind
Posts: 4,020
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default


I have a slightly smaller L39, i find holding about half UP elevator makes the model track and rotate beautifully at about 3/4 power.

Last edited by Bob_B; 10-20-2019 at 04:17 AM.
Bob_B is offline  
Reply With Quote
Old 10-20-2019, 06:21 AM
  #1934  
madmodelman
 
madmodelman's Avatar
 
Join Date: Oct 2006
Location: Corby, Northants, UNITED KINGDOM
Posts: 2,205
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

We're talking about the 1/5 JL one.
Brian, mine is the earlier version, isn't it possible to pack the nose leg to lower it?
I'm flying the larger FB one nowadays.
madmodelman is offline  
Reply With Quote
Old 10-20-2019, 06:38 AM
  #1935  
rcflier53
My Feedback: (7)
 
Join Date: Feb 2004
Location: Ft Mill SC
Posts: 46
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Iíll look into possibly installing softer main gear springs and adding an even stiffer nose gear spring. That with the increased takeoff flaps will hopefully make the T/O less eventful. Looking at the BVM video on the L-39, that plane looks to be almost perfectly level on the takeoff roll and eases into the sky. Granted thatís on a paved surface too. Thanks for some ideas guys!
rcflier53 is offline  
Reply With Quote
Old 10-20-2019, 06:54 AM
  #1936  
madmodelman
 
madmodelman's Avatar
 
Join Date: Oct 2006
Location: Corby, Northants, UNITED KINGDOM
Posts: 2,205
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Yes, good luck, I haven't got mine now, I would have liked to advise you on my cg.
Mine did fly very nicely.
madmodelman is offline  
Reply With Quote
Old 10-27-2019, 04:42 PM
  #1937  
rcflier53
My Feedback: (7)
 
Join Date: Feb 2004
Location: Ft Mill SC
Posts: 46
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Spent the whole afternoon working in the shop with my Xicoy CG calculator. I started over with all the CG setup and distance calculations. I double checked the factory marks and they match the manual spot on. I used those marks and the balance came out perfectly matched to those using the manualís criteria. These are the weights I logged for different phases of flight based on fuel loads:

CG weight w/UAT full & 1/2 full header tank = 38.3 lbs
Takeoff full fuel (w/o smoke fluid) = 44.1 lbs
Takeoff full fuel with only 50oz smoke fluid = 46.4 lbs
Landing with 1/4 fuel load & no smoke fluid = 40.5 lbs

No wonder this thing dogs so bad on grass. 46+ lbs takeoff with 50oz of smoke fluid.

I also logged the CG change with adding fuel and smoke fluid. My location I chose for weight placement is the nose cone. Full fuel load and no smoke oil, causes the CG to shift forward enough, that the calculator says to remove 0.5 lbs from the nose cone. Add in the smoke fluid and it says to remove 0.6 lbs from the nose cone. At landing fuel load and no smoke fluid it was showing to remove 0.2 lbs from the nose. Not terrible by any means for all those scenarios.

I think Iím just shocked at the weights and trying to figure out how much overweight my bird is than everyone else. Or if Iím worried about it for no reason, and to just adjust takeoff flaps, and flying technique for the first few minutes of a flight.
rcflier53 is offline  
Reply With Quote

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