Ramos are you talking about the Hamburgh event? if so as far as i know it is still on and scheduled for October 10,11 and 12th.




Alan

3D.
no i was talking about the titusvill... where is hamburg any way??

I have made a change to the way I am shielding the elevator servos from the hot exhaust gas. I originally had one piece of tin over the pipe gap. I feel this may not give me the best cooling and allow the bellmouth to do its job. I now have two seperate shields covering the servos. I will fly the L-39 and let you know how it works.

Maj.wood. I agree 100% for your heat process, thats why I have been waiting 6 mo. for the turbine bypass. My L-39 is ready, less turbine install because I do not like the close quarters with elevator servos. HOPE Wagner will chime in and advise bypasses are ready to ship as I have waited a long time for this important part of the Jet. I talked to Wagner at the MAC an he said shortly?
Wagner please chime in and get us the bypasses. What's the hang-up? The planes are more difficult, time wise to make? A BYPASS? Let get it together. WHMC STL

I agree on the elevator servo location. We will send feedback to the factory and see about relocating those. As far as the bypass, I never use them. All my jets fly with just a bellmouth on the pipe. The L-39 fuse is very wide. Larger than most in the turbine area so I feel with the right setup and correct pipe size and pipe to turbine gap there should be no problems. I think the supplied pipe is a bit small for my P-70 and causing some heat related issues. Wagner has the factory working on a larger pipe. I think that will solve any heat issues.

I was planning to fly the L-39 today but the weather is a washout. Next weekend I have a full scale airshow to attend(Thunderbirds) so I am not sure I will get to do any flying before the Liberty Bell Jet Rally. My line up for that event is my FeiBao Panther and Tamjets A-4 Skyhawk. The L-39 takes a back seat again. I will hopefully get some time on this bird soon. I only have one flight on it!

Just a thought Woody, do you think that your first designed heat sheild have worked better if it had a bell mouth on it?

William

Hi William.
Do you mean the pipe or the original shield having the bellmouth? The pipe did have a bellmouth with the original shield. Having a bellmouth on the shield is an interesting thought. My new setup really opens things up but I fear it is my pipe diameter that is the real culprit.

Yes I was talking about the heat sheild that you made the first time. It should have had a rounded front end on it and bent up a little to help let more air pass through it while protecting servos from the heat.

William

Pretty good considering the thread has 208 posts...you've generated a lt of interest in this bird...

Thanks William.
Wayne just think how much I can say about it when I get some flights on her!!!

...and we are waiting for that!!

Can anyone tell me what are the four little white F/G parts for? . The look like fairings for somewhaer on the model.


Regards

I think you would use them on the hinge line or perhaps servo linkages. I would have to look at the full size bird to locate them and thus determine their use. I did not use them.

I just got back from an airshow and they had two L-39's there. One was Angel 7 painted in the Blue Angels colors. That jet flew and looked great in the air. The other L-39 was in a camo color and on static display. Those fiberglass fairings are for the top of the flaps. There are two on each side of the jet covering the flap linkages. I am all fired up to fly my L-39 but can't till I get back from Liberty Bell. I just can't wait to get this jet back in the air!!!!!!!

Another way of resolving the elevator servo heat shielding. Note I also turned the servo control arms around to outboard position (easy mod) and used aluminium servo control arms. I also made up some small servo heat shields from .005 mm stainless steel sheet and attached to engine bearer next to servos on both sides as you can see in photo.

Cheers-Marty

And a couple of my scratch built cockpit

Wow that cockpit looks great!! Interestingly when I ran the jet up in my driveway with the new heat shields the shields were cool to the touch. Even 5 min after shutdown the bellmouth on the pipe was still too warm to keep your finger on. This tells me that the servos are not that much in danger. When the hatch is on and I am flying may be different but I will let you know. I am not concerned.

....as long as you never, ever have a hot start......

Well that is true. All bets are off during a hot start.

I have some time between jet rallys so I am going to fly my L-39 this week. I will actually meet Wagner in Titusville (home of Octurbofest) and he will join me for a few days of jet flying. I should have some detailed info on flight characteristics by the end of the week. I may be a bit distracted by the arrival of my new FeiBao F-5E however.

i saw the pics of the F-5 that ur getting... B E A U T I F U L!!!!!! i cant wait to see it... hope ur flights are going well.. gotta here the report on the L-39.. ttys dom

jerry

Ok guys, here is the complete chronicle of my experiences with my new L-39:
I test flew the jet back in April and only logged one flight. The plane flew well but I was unable to retract the gear. I had lost air due to some airlines rupturing from heat. During that flight the L-39 felt solid and was very aerobatic. The landing was smooth but I was shocked that when I taxied back to the pit I saw that the wings were completely destroyed. The force of the landing caused the wing skins to delaminate from the ribs and even the trailing edge spars split. I immediately contacted Wagner of Rcjetmodels and he had me cut sections of the wing apart to use as color samples for the new wings that he promised to send. Wagner and I discussed the design and materials used for the construction of the L-39 wings and also what improvements should be made. Wagner took the color samples and my notes to China during his factory visit. In about 45 days the wings had been totally redesigned with new materials and construction techniques. When I received the new wings I was immediately drawn to how solid they felt. They were very strong. Absolutely no flex at all when I tried to twist and tork on them. I also noted the extensive use of Carbon fiber, different higher quality epoxy and a new material Nomex that was used in place of the balsa parts (wing skins / spars). The color match of the new wings was perfect!! After assembling the new wings I was anxious to fly the L-39 again. I made arrangement to meet Wagner in Titusville, PA for test flying.

Well it was a hectic two days of test flying.
On the first flight I did not retract the gear for fear of the heat problem. My new heat shields for the elevator servos worked great and were better than my original setup. Still after landing I found that I had burst my airlines again. We spent all day repairing airlines and flew all but one flight with the gear down. I rerouted the lines in front of the first engine bulkhead but still was getting heat damage. I ultimately enlisted the help of my friend Rich Miller who was kind enough to bring an assortment of heat shielding materials to the field. He first replaced my airlines with HD lines from DreamWorks. next the lines were installed into a woven tube that is used to insulate lines and such. The tubes were than wrapped with aluminum tape. End of failures in that area. We believe that the excess heat is caused by the far too small pipe supplied with the kit. The rear ID is only 2.5". My P-70 posted good numbers as far as max and average temperature were concerned. I verified these numbers with Jetcat. Wagner Is going to contact the factory about building a larger pipe.

Now the flying.
This jet is a dream to fly. It is super smooth and will gracefully perform all aerobatic maneuvers. We did it all. Point rolls, slow rolls, loops, inverted, knife edge and so on. With the gear down the plane cruises at about 130 or so. But hold on cause when the gear is retracted this thing transform into a sport jet!! It is very very fast. You wont believe it. An awesome plane to fly. Takeoff are so pretty to watch. The ground handling is rock solid….tracks like a cat.

There were problems. This is a great airplane to fly as long as you don’t land it!!!!!
We flew the jet a total of 8 flights and the first 5 landings should have completely destroyed this plane. The jet would just fall out of the sky. I mean you are on final, everything looking good, great airspeed and without warning the jet just falls out of the sky. Absolutely punishing the landing gear and wings. I’m talking dropping in from like 3 feet! Every type of approach was tried, fast, slower, steep, flat, full flap, take off flap etc and this thing kept falling out of the sky. The jet also had a tendency to balloon on final as it approached the runway. This too resulted in the jet now sitting 6 feet in the air with no airspeed……..down to the runway she goes.
I can’t tell you what a beating those retracts, struts and wing took. The great news is that new wing design is awesome. There is zero sign of any damage or fractures anywhere(I gutted them after day one of flying and examined the inside with light). The landing gear and struts are perfect as well. Remember the spring setup I choose in my building thread. well it works. There is actually no damage anywhere on this jet despite all this.

So that was the end of day one. After spending all night taking the jet apart and looking for damage I then had to figure out what was wrong and a strategy for the next days flying. The CG was rechecked with empty tanks, full tanks and ½ tanks and was determined to be fine as per my original setup. The next day we logged three more flights with absolutely perfect grease job landings. So what was the problem? Well when I landed with take off flap (15 mm) the jet would balloon on final. With landing flap (40 mm) the jet would fall out of the sky. What I did was reduce the landing flap to 25mm. My thought was that is was a good number between the others and should give the perfect ratio between lift and drag. I also reduced my elevator throw from 20mm to 15mm. As a note, I don’t use expo. These settings along with flying a specific approach resulted in a stable, predictable approach that allowed the jet to softly return to the runway. My approach was a constant descending, slightly nose down approach. You must keep the nose slightly down, pointing at the runway till you are about three feet off the ground. Then gently level the jet to bleed excess speed and finally pull the nose up slightly and hold it. The jet will gently land on the mains followed by the nose. Do not try a high alpha power on approach. this is a conventional wing jet and that technique does not work.

I can’t tell you what a great flying jet this is. And now a great landing one too. Those landings are now so pretty. As I get more time on the jet I will update the thread. I will bring this jet to the D.O.G.S. rally along with my Panther so you will get to see it first hand. It was a long journey but now I have it all sorted out and will no doubt end up having this be one of my favorite jets!!

I want to thank Wagner of Rcjetmodels and FeiBao for the outstanding customer service as we worked out the kinks on this project.

Here is some photos from Titusville yesterday
Sorry I forgot to take photos of the new airline insulation, I was too busy

p.s the last photo was at Capt Crackers house on Lake Erie during a beautiful sunset!

Rich

Hi guys.
I just returned from the D.O.G.S. show where I was able to log 22 flights between the Panther and L-39. The L-39 now has a total of 27 flights on it. I like this jet more and more each time I fly it. It is super smooth in the air, very nimble and a great aerobatic plane. I was running low on fuel on one flight and while waiting for my turn to land I pulled the power to about 1/3 and deployed the take off flaps but keeping the gear up. I was shocked at how slow this jet will fly. And it is ROCK SOLID during slow flight. No wallowing. And I am not just talking a straight flyby but being able to turn and maneuver in this configuration. Who knew!! The landings are now very consistent. I was able to grease most of my landings all weekend. Just fly a good slightly nose down approach to the runway, level off at about ten feet and maybe five or ten degrees nose up and hold it. Just before touchdown add a bit more backpressure for a gentle mains first landing. The jet tracks straight as an arrow on the ground. I was surprised since it has a narrow wheel base. The trailing link gear can handle even the most brutal runway conditions. I am working on getting a larger pipe. The supplied pipe is only 2.5" ID. I'm getting lots of heat in the jet as a result. Wagner is working with the factory to get me a 3 1/4" pipe as recommended by Jetcat. I think the new pipe will really wake this jet up. It is quite fast now but I think there is more performance to be had. That's it for now......I need to go flying

Dom at the DOGS show