The L39 is a relaxing plane to fly. I'd also say it does not need stabilization.

Originally Posted by ryan_t888

The L39 is a relaxing plane to fly. I'd also say it does not need stabilization.

For that matter it doesn’t need flaps either, but needs got nothing to do with it. However, if you live in a place like Kansas with weather fronts hitting from all sides then you may benefit from stabilization.

Thanks!

When you look at the L-39 Wing underside you will see the 'spar slots' that many foam aircraft have. If you look down into them with a torch, you will see the L-39 has a fiberglass rectangular spar. About 3mm wide, and unknown height (prob 8mm or so?)
This runs along REARWARDS of the wiring channel.

There is not much room at all to fit an airspeed sensor and the pitot tube rear Y piping.
You would need to go all the way to that spar, and where the wiring run goes. Re-routing the wiring 'around', or whatever, the sensor put in there.
I would say that it can be done, but it will all be a tight squeeze and basically need 'hacking as you go' to make enough room for it all. Then patch it all up back to a good finish after that.
It is also possible it could be covered over with a thin plastic cover plate, so that it is accessible.

For my case, it will only be temporary to test airspeeds, so it will be in the nose (there is just enough room in the nose area to fit it all), or on a temporary side pod that comes out of the canopy/hatch joint. Modding the Wing is too invasive to be worth it for my case.

Originally Posted by PeterVRC

When you look at the L-39 Wing underside you will see the 'spar slots' that many foam aircraft have. If you look down into them with a torch, you will see the L-39 has a fiberglass rectangular spar. About 3mm wide, and unknown height (prob 8mm or so?)
This runs along REARWARDS of the wiring channel.

There is not much room at all to fit an airspeed sensor and the pitot tube rear Y piping.
You would need to go all the way to that spar, and where the wiring run goes. Re-routing the wiring 'around', or whatever, the sensor put in there.
I would say that it can be done, but it will all be a tight squeeze and basically need 'hacking as you go' to make enough room for it all. Then patch it all up back to a good finish after that.
It is also possible it could be covered over with a thin plastic cover plate, so that it is accessible.

For my case, it will only be temporary to test airspeeds, so it will be in the nose (there is just enough room in the nose area to fit it all), or on a temporary side pod that comes out of the canopy/hatch joint. Modding the Wing is too invasive to be worth it for my case.

Thanks - I’ll have a looksee. I was even thinking of mounting the sensor and the circuit in one of the tip tanks

The L-39 is such a great flying jet! But today I finally tried to destroy mine, by mistake of course!
I guess it is good to be wary of using three battery sizes, and having many of each.... 4500,5000,6200.....
And then when the 4500's and 6200's are the same 'yellow' types.....

I put in a 4500mAH but for some reason began believing it was a 6200mAH
I fly with non-stop Telemetry readouts, but I found out today that I 'ignore' things I am not focussed on..... so I fly along until near the level of Capacity (mAH) used, and THEN begin to monitor the Voltage to fine tune using the maximum without over-doing that and running the battery hot ever.
So with 6200mAH I fly to 4000mAh and then change to Voltage monitoring.
This is not good if you really have a 4500mAh battery in there......

The VOLTAGE would have warned me, but it was just being 'ignored' seeing I was only nearing 4000mAH. You would think you might NOTE the Voltage number being amiss/low..... but I didn't at all.

LVC..... just coming off a Split-S, and I pretty well immediately recognised "No Whine" coming from the L-39. "Oh oh, something is wrong, it has no Power". A quick zero throttle to reset LVC, if it was that, but no change.... something else must have gone wrong, but I still have control....
I went into instant Gear Down and Low Level Flaps, but I had just passed myself so Landing was going to need a 180deg turn back - from about 20feet altitude and 'fairly fast'.
Turning from 'midway across the field' means a left or right turn head to treelines, and you don't really want to do a 180deg turn without going to one side first - but I had no spare energy to waste. So I had to turn TIGHT, and be as efficient as possible!

All in all I was very happy with that process as it was done to the best manner possible - very smooth all the way around - but I also could see, extrapolating the path, that it was not going to get around and still be FLYING!
I pressed it as far as I could, but it stalled about 3 feet off the ground and thus came down 'level' but quite hard - onto the Landing Gear.

The Main Gear Fairings were not happy.... they disintegrated!! So did both of the 3D Printed Fuel Tanks.
One Main Gear Retract mount tore out... and the Nose Gear Retract Pin bent about 30deg, plus that Mount also lifted out X amount.
But at least there was no FOAM damage anywhere! The other damages are easy fixes, but a foam/paint finish damage would be a nuisance!

It could have been a BIG disaster, but I guess it was somewhat 'lucky' that I recognised it immediately (thanks to the noisy/whiney outrunner!), and the place it all began versus what I needed to do to get it down alive. Not quite 100% lucky.... maybe 90% good enough luck.

I will make sure I LISTEN to the Voltage telemetry numbers at all times also from now on!!

-------
Main Gear Fairing STL and GCode files attached:
(mirror the STL file to get the Left one)

I altered the Main Gear Fairings a tiny bit, to be more 'perfect' - they are probably better than the stock design really.
V5 has a better 'slope' of the mounting posts - just in their height difference.
V6 has the faces of the mounting posts also sloped - to match/offset the fact that the Fairings are not parallel to the Main Gear legs really anyway.
Both work totally fine anyway really.

I also added STL's, GCode files, and the PruseSlicer Project files. That way all the settings can be seen/used also.
Probably all 3D printing stuff should be given WITH the settings files so other people can print it as well (or alter to be better possibly) than the designer did.
PS: PrusaSlicer is probably the best Slicer to use anyway!!

And luckily, Red PLA Filament is close to a perfect match to the L-39 too! So no painting required....

Originally Posted by PeterVRC

And luckily, Red PLA Filament is close to a perfect match to the L-39 too! So no painting required....

Depends on the brand.

I have some of the crappiest red PLA I have ever seen that I bought of eBay

Freewing L-39 Inverted Loop (3 min 51 sec)

Swapping my L39 bits into a new fuse (don't ask) and noted that there is no fairing on the exit of the fan - the in-runner wires are just out in the airflow.

Is that normal? If so, has anyone printed one?

OMG NO! You have to fix that.

No really, it's normal.

In future I will pay more attention to the Telemetry readouts!

But at least it 'made' me improve the 3D Printed items a bit (design/mod) and the L-39 came out unscathed in its Finish (foam, paint etc) so I got off lightly with the 'incident'.

L-39 Albatros - Freewing 80mm EDF - LVC Crash Landing movie (7 min 31 sec)

LIVE from the St. George Utah 2020 Presidents Day fly in from MotionRC Customer Community on FB.

First tracks and a beautiful pinky sunrise demoing the new 80mm inrunner on the L-39.

L-39 from MotionRC, LIVE demo from St. George, UT (6 min 8 sec)

It is an awesome flyer! I am loving flying FPV with her!

Albatros L-39 Jet - FPV Aerobatics Flight (6 min 32 sec)

Would it be safe to say the L39 has a better, more robust landing gear setup than the A4 for flights off grass or flying fields with a grass runoff area that you may run into after possibly landing a lil hot? I’ve destroyed more landing gears on foamies just by ending up in the runoff area after a nice landing.

I really like the A4 but this L39 might be a better plane for me. Comparing them at all I would imagine is apples to oranges in the way they fly.

If anyone can get back to me regarding the landing gear versus the A4 gear please let me know. I would also like to hear from pilots who have flown both the A4 and the L39.