RE: What do you think about JETLEGEND L39?  
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All Forums >> RC Airplanes >> RC Jets >> RE: What do you think about JETLEGEND L39?
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RE: What do you think about JETLEGEND L39? - 4/29/2008 7:18:23 PM   
jetjohn


 

Posts: 309
Joined: 6/9/2005
From: Cardiff, UNITED KINGDOM
Status: online 		Hi Jeremy,
Attached shot shows tanks,header & air cylinder for mains & doors.
Hope this helps,
Regards,
John C


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(in reply to Jeremy_D)
       Post #: 726

RE: What do you think about JETLEGEND L39? - 4/29/2008 7:50:49 PM   
dbarrym



Posts: 1187
Joined: 10/21/2003
From: Carlsbad, CA, USA
Status: offline
quote:

ORIGINAL: Jeremy_D

Can you guys post some pics of where you have put your header tanks.

Also how many air tanks are you using, I was thinking of using two 350cc air tanks for the mains and doors and a 300cc tank for the brakes. Will this be enough?

THanks guys


No access for pics till later...but visualize this.. for UAT mount, I made a small inverted "V" shaped tray from 1/8" lite ply that is epoxied in the rear half of the fuse, just behind the seam/flange, and ahead of the main tank tray and to the side of the airbrake hinge. The UAT is Velcro-strapped to this tray.

I am using both of the supplied air tanks (look like "medium size" Robarts to me) T-ed together for brakes, mounted below the radio tray in the nose (way overkill, one is fine). I have two XL Robart air tanks, mounted on the fuse sides with Velcro, just behind the engine hatch opening and just above the engine mounting rails. These are T-ed together to provide high pressure air (not volume) for the retracts and doors. From 105psi, I can get 5 full cycles before the pressure drops to 80 psi, at which point the gear gets too s-l-o-w on the up cycle. I am using BVM high flow air valves as the stock valves leaked (and those mains are HEAVY).

Pics later.

Barry


(in reply to Jeremy_D)
       Post #: 727

RE: What do you think about JETLEGEND L39? - 4/29/2008 10:32:58 PM   
Jeremy_D



Posts: 430
Joined: 2/17/2005
From: Central Coast, AUSTRALIA
Status: online 		Thats excellent guys, thanks.

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(in reply to dbarrym)
       Post #: 728

RE: What do you think about JETLEGEND L39? - 5/4/2008 6:35:38 PM   
mustangjb


 

Posts: 44
Joined: 6/8/2006
From: Jongny, SWITZERLAND
Status: offline 		Hi all,

Maiden flight this WE in Italy Eolo Jet meeting.

The plane is prefect with the CG or JL, just a little bit slow with the P-120 but enough to take off.

I have doing more than 10 flights, but the front wheel strut have broken during landing, so check this point with yours.

(in reply to Jeremy_D)
       Post #: 729

RE: What do you think about JETLEGEND L39? - 5/4/2008 8:11:25 PM   
cairoman



Posts: 721
Joined: 12/6/2001
From: Nicosia, CYPRUS
Status: offline 		Gentlemen,

I don't wish to disapoint any of you, but please be warned about the strength of the wing carbon (supposedly) tubes!!! they are a joke, so you really need to strengthen them (carbon rod inserts probably) before you experience what happened to me: The front left carbon tube was cut like a cucumber for no apparent reason, two minutes after take-off and the whole wing parted the airframe in two seconds after that leading to an uncontrolled spin and the inevitable crash and burn thereafter. Total equipment lost worth €6000/U$9000....not to mention workmanship from the Guru himself..Mr. Spiderjets!!!! I only had three flights on it and not a scratch before that...BTW not even a warning!!!! and no flutter!!!

I have emailed Yang at JL informing him about the incident, but as you all already know.....absolute silence from him!!!

Chris

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< Message edited by cairoman -- 5/6/2008 8:56:44 PM >

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IJMC-Cyprus, JET-TRONICS' REP
WREN'S REP in Cyprus

(in reply to mustangjb)
       Post #: 730

RE: What do you think about JETLEGEND L39? - 5/4/2008 11:03:11 PM   
lookilook


 

Posts: 44
Joined: 1/10/2008
From: NICOSIA, CYPRUS
Status: offline 		OH NOOOOOOOOOOOOOOOOOOOOOO! CHRIS.........ITS SO UNFAIR LOOSING A PLANE FROM BAD MANUFACTURING......IT WAS AN AMAZING MODEL WELL BUILT UP AND GREAT COLOURING.....PITY PITY PITY.......DONT THEY REFUND WHEN ITS THEIR FAULT WHEN SOMETHING LIKE THIS HAPPENS??I HOPE THEY DO CAUSE ITS A GREAT MODEL OR AT LEAST OFFER YOU SOMETHING ELSE IN EXCHANGE!!!

_____________________________

my wife wants the world and i give her universe
that's how i keep flying,its tough out there!

(in reply to cairoman)
       Post #: 731

RE: What do you think about JETLEGEND L39? - 5/5/2008 6:33:10 PM   
SpiderJets



Posts: 823
Joined: 12/26/2001
From: .., BELGIUM
Status: offline 		Christos,

I feel very very sorry for your loss of this great L-39. The photo was a big shock to me.
I really tried hard to spot the remnants of Batman and his girlfriend to identify this really used to be "my" plane, but in vain. Godspeed them too.

With all my sympathy for your loss,
Nicolas.

PS. ..."Guru"... ?????

(in reply to lookilook)
       Post #: 732

RE: What do you think about JETLEGEND L39? - 5/5/2008 7:09:20 PM   
cairoman



Posts: 721
Joined: 12/6/2001
From: Nicosia, CYPRUS
Status: offline 		Nico,

Your building skills and workmanship is unsurpassed by anyone's I know!!!

Yeah, the strange thing is that no one has commented yet. This is a very serious flaw in the L39 kit and let me tell you...an accident of this type is bound to take place somewhere in the world on a JL L39 pretty soon!!!!

Chris

< Message edited by cairoman -- 5/5/2008 7:15:56 PM >

_____________________________

IJMC-Cyprus, JET-TRONICS' REP
WREN'S REP in Cyprus

(in reply to SpiderJets)
       Post #: 733

RE: What do you think about JETLEGEND L39? - 5/5/2008 7:15:29 PM   
dbarrym



Posts: 1187
Joined: 10/21/2003
From: Carlsbad, CA, USA
Status: offline 		I am wondering if the aluminum clamps may have cut into the CF wing tubes over time and essentially created a stress riser. I am on business travel now but plan to take a close look at mine on return home.

The L39 can handle a bit of weight, it might make sense to insert an aluminum or steel rod into the tubes with Hysol so that it goes 4" or so into the wing past the root. That at least would provide a more graceful failure than a pure CF rod.

I had wondered about the small diameter of the joiners, there's a LOT of load on them, especially on hard landings.

Barry

(in reply to cairoman)
       Post #: 734

RE: What do you think about JETLEGEND L39? - 5/5/2008 7:40:38 PM   
SpiderJets



Posts: 823
Joined: 12/26/2001
From: .., BELGIUM
Status: offline 		Chris,

I'd like to see that wing tube when I come to meet with you in Cyprus next week. It's hard for me to see on the photos how and where the failure took place exactly.
What Barry writes, makes sense. Having two different materials in composite for the wing tubes is a good cure for the eventual material weakness of the other. CF tubes have a weak point and that is eventual splitting...

Nicolas.

(in reply to dbarrym)
       Post #: 735

RE: What do you think about JETLEGEND L39? - 5/5/2008 8:03:33 PM   
cairoman



Posts: 721
Joined: 12/6/2001
From: Nicosia, CYPRUS
Status: offline 		I have it in my workshop. We'll do a more thorough post mortem when you arrive next week.

Chris

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IJMC-Cyprus, JET-TRONICS' REP
WREN'S REP in Cyprus

(in reply to SpiderJets)
       Post #: 736

RE: What do you think about JETLEGEND L39? - 5/5/2008 8:18:59 PM   
jetjohn


 

Posts: 309
Joined: 6/9/2005
From: Cardiff, UNITED KINGDOM
Status: online 		Christos,
Sorry for your loss.

Thank you for the heads up on this issue.

I have just taken a look at the wing tubes on my L39 & they appear to be constructed from three tubes fitted one inside the other.
There are some slight marks on the tubes were the clamps go but nothing to indicate a fracture.
However scince there is an 8 mm hole in the centre of the tubes I think it will be wise to fit an 8mm alloy bar inside, if not a carbon rod.

Once again sorry for the loss of your plane. Especially scince this was the first aircraft/L39 on this forum that helped so many others with construction hints & tips.

All the best,
John C


(in reply to SpiderJets)
       Post #: 737

RE: What do you think about JETLEGEND L39? - 5/6/2008 9:06:20 AM   
aerialcameraman


 

Posts: 58
Joined: 1/19/2007
From: Limassol, CYPRUS
Status: offline 		IMPORTANT Safety Bulletin JL-L39
I would advise all JL-L39 owners to read this carefully, I was a witness to the total demise of the Christos/Nicholas L39. The model took-off in a normal manor and carried out several high speed level circuits when the right wing came off. I immediately recovered the wing and discovered that the initial component failure was the front carbon rod. This had snapped off next to the alum. clamp. To make a conclusive analysis as to the exact cause one needs to understand certain aircraft design principals. The loads incurred on a wing when subjected to + and - G forces act through the upper and lower surface skin structure and are then focussed into the fus. On full size aircraft the wing is usually attached in three primary positions which are at the main spar - top and bottom close to the wings surface and at the back of the wing to anchor the wing against for and aft movements. The rear carbon spar mount on the JL-L39 is fine for that purpose, but the front one is one of the worst design faults that I have ever seen. 95% of the wing loading is focussed at this point and it is totally unsafe and displays a complete lack of aircraft engineer