Aero L-39 Albatros - 50mm EDF jet

[Grifflyer]

on 64/70mm version its should be to only adjust plansizes accordingly . Do the plane a touch lagrer to get that edf´s to fit.

Yes, the plane needs to be bigger for the 64/70mm EDF to fit.

 

[FoamyDM]

OK, I think this is pushing plane is pushing something out of Build-ruary. I have been eyeballing it up and down.. I have the motor system all up. It's time.

 

[Grifflyer]

OK, I think this is pushing plane is pushing something out of Build-ruary. I have been eyeballing it up and down.. I have the motor system all up. It's time.

Sounds great!!

 

[Timmy]

What battery do you recommend? Is a 2200mah 4s too heavy?

 

[OliverW]

What battery do you recommend? Is a 2200mah 4s too heavy?

A 4s 1300-1800 would be best. I don't think it would get into the air of you used a 4s 2200

 

[CarolineTyler]

What battery do you recommend? Is a 2200mah 4s too heavy?

Mine fly's well on a 1300mAh 4S battery, 3 minutes of flight with around 1 1/2 minutes left before the ESC cuts out so time for a go-around or two.

 

[Grifflyer]

What battery do you recommend? Is a 2200mah 4s too heavy?

That’d be too heavy, an 1800 is probably the heaviest you could go

 

[Lester]

Thanks for the offer but I'll just patiently wait for final plans. I actually plan to scale them up slightly to accommodate a 64mm edf.

How much do u scale the plans up for 64mm edf

 

[DrthVdr]

Thanks For the plane Grifflyer! This was my first scratch build which I enjoyed it immensely.
I've just completed a 125% ver1 L-39 powered by a 70mm Dr Mad Thrust 2600KV; 100A Turnigy ESC sucking on a 6cell FullyMax 2600mAh 40c battery.
Servos - Ailerons 2x 9gr , Elevators 2x 9gr

As soon as this cold front passes I'll maiden it.

 

[DrthVdr]

Question?
Why is there no rudder?

 

[CappyAmeric]

Question?
Why is there no rudder?

Small single motor EDF jets often leave out the rudder. The No P-factor to counteract like on a prop plane.

Making coordinated turns in small R/C is usually just a guess anyway.

 

[Intashu]

Well I got my 64mm L-39 maiden out of the way. And it survived with only minor damage due to pilot error.

Took a moment to get it airborne, I seriously forget you gotta throw this thing like you hate it to get enough airspeed to climb. Once I got that sorted out it flew pretty well. I needed more up elevator trim than I had so I'll have to cut an acess for the servo and adjust the horn position. Otherwise it flew great! Can't wait to fly it FPV.

On landing the low voltage kicked in a little sooner than I thought so I suddenly had little power, when attempting to flare for a landing in the tall grass it instead overshot the grass, tip stalled and nosed into the dirt.

Fortunatly based on lessons learned from my first L39, I reinforced the whole general front of the plane so apart from a bit of crumpled foamboard it's still perfectly capable of flying again!

I uh... Do need to get some higher C rated batteries however. My 4s 50c battery was quite warm and a little swollen after flying. (it shrank back down after it cooled off)

Absolutly think this plane does well scaled up too. The photo kinds warps the perspective a bit, while I made the main wing like 10% wider than stock (I just extended the cantilever area of the wing tips) it looks way longer in the photo. Went with a paint job based off a navy plane I saw while Googling for paint ideas. Simple, and effective. I'll have to get a few more flights in on this bird before I move up to a 70mm F22 I want to build!

 

[DrthVdr]

Im glad you maiden went better than mine...

 

[DrthVdr]

Didn't quite know you have to throw like Thor chucks his hammer. Just couldn't get it in the air.

 

[Intashu]

Im glad you maiden went better than mine...

My first L-39 only flew once, and spent more time in pieces with multiple nose re-builds. This thing needs a LOT of forward throw to get enough airspeed to take off and not just stall crash (and slightly upwards too) and the tip stalls can be dramatic as well. That being said it can spin like a top and is really nimble through the air with plenty of speed to boot.

It really helped that the field I launch at currently has 3-4 ft tall weeds too, so I chucked it over that, and the few bad launches I had just meant I had to walk though the grass for it, but it sustained no damage in the process.

and yea, I basically needed to put all my effort into a very hard hand launch (while still throwing it it upwards slightly) to get it to fly. my other jets I can do a underhanded toss at full throttle and it will get in the air, but not this bird.

Unfortunate you snapped yours in half, but it shouldn't be too hard to repair and send it again! I suggest making sure the wing is fixed really good and solid to the body as well. I also suggest if you haven't already, using a good strip of thin basswood along the bottom of the whole battery area. my first one had constant problems with breaking the nose off or otherwise destroying the front end, and a wood tray along the bottom really reinforced my current L39 substantually from its little dirt cartwheel landing. I got to remember next time to land it FAST, by flying real low to the ground where the grass is cut and trying to get it to properly flare before it can tip stall. I'll be adding wing tip reinforcement to it before I fly it again as well since they got a little beat up.

 

[DrthVdr]

Thanks for the advice, Ill make those changes and try again.
Luckily I took my Dynam Pitts Python 1080mm with to bash around. I love this plane and fly it on 4&6cells with upgraded motor, DualSky 3520 V2 Eco 820kv 15"x7". Its a BEAST!!! More then double the power of the stock setup.. MoPowaBaby!!! Its a hand full on 4s and completely bonkers riot on 6s..
So the day wasn't completely lost...

 

[CappyAmeric]

Maidened. 128% Grifflyer L-39 with 64mm EDF. The EDF is an old one I had lying around - Freewing 3s 4500kv. Pretty anemic. Empty the L-39 was 680 grams. With a 3s 1300 mAh it almost balanced, and ended up very tail heavy. Hand launch was fair, but after getting control of it with aft CG, it crashed with minor damage. Then I tried a 2300 mAh 3s, and it balanced well, but so it flew very well, but only at full throttle.

I like it. I ordered a Xfly 64mm EDF that is 4s, and 50% more advertised thrust. I will likely cut this one open and try the new EDF and bash it around some while I build a new one. Thanks @Grifflyer for a very nice flying jet!

Livery is fictitious Israeli Air Force L-39 trainer. Tip tanks are 3D prints with magnet attachment to avoid the inevitable wing snags landing on grass.

 

[DrthVdr]

I did the Maths again and scaled the plans at 125% for 70mm EDF but should have scaled it to the EDF OD which is bigger @ 133% so enlarged the wing and feathers and touched up the paint. It’s now 1m ws.
The 6s 415gr battery is all the way fwd. All up mass 1.6kg maybe the wing loading will be better..
what does yours weigh?

 

[Rex227c]

The Aero L-39 Albatros is a Czechoslovakian high performance jet trainer developed in the 1960's. The L-39 has served with over 30 air forces around the world, and is the one of the most widely used trainers. Today the L-39 is used in the Reno air races jet class, flown by demonstration teams such as the Breitling Jet Team of France, and are privately owned by jet enthusiasts.

With this in mind I wanted to create a relatively easy to fly jet the was versatile and had a wide flight envelope. So after four months of work I give you the Grifflyer Aero L-39, a sport jet built out of two sheets of foam board that can be built as an electric ducted fan jet or as a pusher prop jet using standard components found in the Flite Test F pack.

Video:

Overview-

Speed-
Top speed is great when built as an EDF and slows down very well for landing, if built as a pusher prop jet the top end speed drops but your static thrust is much higher giving the plane a more "trainer" like feel.

Handling-
When built as an EDF it tracks like an arrow and the controls are very smooth giving you the ability to fly like a pattern ship, but can become "snappy" and abrupt when you really start banging the sticks around. If you chose to build it with a pusher prop you'll find that it handles similar to a park flyer, but faster and less forgiving.

Stalls-
If your plane stalls it will likely drop a wing but it is nowhere near entering a spin, all you have to do is level the wings and then power out. Due to the fact that a prop jet has more static thrust your recovery will eat up less altitude compared to the EDF setup.

Aerobatics-
The aerobatic ability of this plane limited to the basics, Loops, Rolls, Inverted, Split S's etc.

Take offs-
The method of launching the jet differs depending on how you choose to power it. If you built it with a ducted fan I suggest holding it right behind the trailing edge of the wing and tossing it from there. Let me rephrase that, don't give this a light gentle toss you need to get up to flying speed, because the ducted fan doesn't have enough static thrust to get it up to adequate airspeed before it hits the ground (ask me how I know) On the contrary never launch it like this if you built it with a prop setup as you run the risk of the prop striking your hand, what I do is hold it right in front of the intakes and give it a nice underhand toss and let the motor do the rest.

Landing-
Landing this model is quite simple all you need to do is bleed almost all your airspeed and get it close enough to good 'ol terra firma to put ground effect to work, then right before to hid land flare the plane and you'll "ride" a cushion of air to the ground.

Skill level-
This depends on which variant you'll be building if you want to go prop powered then I'd suggest being able to fly all four channels very comfortably, if you want to build it as an EDF then you'll want to learn how to fly faster planes.

Specs:
EDF Version-
Wingspan- 26in. | 660mm.
Length- 27in. | 685mm.
Wing area- 143 sq. in. | 9.2 sq. dm.
Wing loading- 17.4 oz/sq. ft. | 52g/sq. dm.
Dry weight- 12 oz. | 340 grams
All up weight- 17oz. | 482 grams
CoG- 2 in. from leading edge | 51mm. from leading edge

Prop Version-
Wingspan- 26in. | 660mm.
Length- 27in. | 685mm.
Wing area- 143 sq. in. | 9.2 sq. dm.
Wing loading- 15.8 oz/sq. ft. | 48 g/sq. dm.
Dry weight- 10.2 oz. | 289 grams
All up weight- 15.7 oz. | 445 grams
CoG- 1.5 in. from leading edge | 38mm. from leading edge

Plans:
Aero L-39 Albatros Plans

Instructions:
Aero L-39 Build Instructions


Gallery:
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I have a 64 mm edf ,will I be able to use it for this build?

 

[Intashu]

I have a 64 mm edf ,will I be able to use it for this build?

as-is it would be a tight fit, but you can easily scale the plans up to ~128% and it will be correctly scaled to the larger EDF. This is what I did and I felt like it flies much better being a little larger and able to carry slightly bigger batteries.