FTFC19 Lockheed N+2 SST designed by FAI-F1D

[FAI-F1D]

Update: Final plans here: https://drive.google.com/open?id=1izvmGIf3-AqIt3EN-A6fg_WmeySJoYXl

Whelp I'm throwing my hat in the ring with something rather ambitious. I got away with a mixed propulsion balsa model well enough to release a successful kit (see that insanity over here), so I figured it's time to try doing the same thing in foamboard. And thus, I present to you this absolutely beautiful concept:

Plan is to power only one nacelle and leave the other two empty. That may change if resources permit. Main thing is that the center nacelle will have a QD EDF unit able to easily swap out for a 24mm Estes motor mount. Oh yes, that's right rocket powered foamboard!!!

See y'all at the flightline...er...launch pad!

 

[FAI-F1D]

Design Specs

Center of Gravity:
13 inches aft of the wing root leading edge. For rocket power, this is the CG with a fueled motor; the CG will shift somewhat forward of this as fuel is expended and this is important to maintain directional stability in glide without a propeller present.

Materials:
0.031 Piano wire pushrods (2)
2x Apogee T60 heavy body tubes
1x Apogee T60 coupler
1 Estes BT-60 standard body tube
PNC-60 plastic nose cone (design TBD)
1 sheet waterproof DTFB
1 24mm motor mount adapter for BT-60 from eRockets

Control:
4 Channel Frsky receiver (throttle, elevons, landing gear)
2x Blue Arrow 3g servos (Emax 9051 if buying from the FT store)
3x Turnigy 1440A 4.4g servos (these have a loose gear train which is critical for surviving shock loads on a custom retract system--I cannot afford the weight of commercial retracts on this build)

Propulsion:
In EDF mode
No-name 35mm EDF, 7000 kv
20A esc
3s500 Lipo

Prop Jet Mode
Emax 1306-3600
4x4.5 prop
20A Emax esc
3-4s Lipo, 400-600 mah

In rocket mode
24mm Estes black powder motor (D12 or E9 series)
24mm-BT60 adapter mount
2s200 Lipo

Balsa Catapult version (see attached files):
1 sheet 1/8" balsa
1 sheet 3/32" balsa
scrap of 1/64" ply
lead sheet balancing weight

Plans repository: https://drive.google.com/open?id=1izvmGIf3-AqIt3EN-A6fg_WmeySJoYXl
Build video:

Flight demo:

Dimensioned plans:

 

[Namactual]

I have never heard of this before now. That looks sweet.
I can't wait to see this build.

 

[b-29er]

Neat! Also what is the wingspan going to be on this bird?

 

[FAI-F1D]

Unfortunately Lockheed being Lockheed, no 3-views have ever been released for this rascal. As such, I'm having to somewhat eyeball the proportions. What we have here more or less at least looks like the N+2. And yes, this is set up as a balsa catapult glider. I'll use that for testing to verify that there's sufficient yaw stability. 50' up at 150 mph is a bad time to find out that you've got severe Dutch roll.

 

[FAI-F1D]

Neat! Also what is the wingspan going to be on this bird?

Probably in the 20-25" range. I want to keep it fairly small so that it will boost satisfactorily high on D12 motors. Also trying to stay under 200g all up in electric mode to hopefully get sprightly performance.

 

[kilroy07]

Unfortunately Lockheed being Lockheed

I thought I recognized that little rascal on the tail fin!

Very cool design, looking forward to the Rocket maiden!

 

[Lufthouse]

Looks awesome man!

 

[Namactual]

50' up at 150 mph is a bad time to find out that you've got severe Dutch roll.

C'mon, where is your sense of adventure?

Just kidding, that is a sound plan. I have been debating if I want to start with a small scale chuck glider as well. I might just be worth it with these unconventional airframes.

 

[rockyboy]

I'm thinking EDF's on the two outer nacelles and a D12 rocket boost in the center one - to be ignited once up at a safe altitude of course - and I really want to see the video of boost ignition, especially if it rekits the model in midair

 

[FAI-F1D]

I have been debating if I want to start with a small scale chuck glider as well. I might just be worth it with these unconventional airframes.

Highly recommended. Also you've no doubt seen my proposal about that over in the challenge thread. I think it's a great way to get this done and I can do it fairly economically.

I'm thinking EDF's on the two outer nacelles and a D12 rocket boost in the center one - to be ignited once up at a safe altitude of course - and I really want to see the video of boost ignition, especially if it rekits the model in midair

Yeah, I thought about that, but the weight starts piling up fast. There's a lot going on the moment you try to fly a rocket glider with enough electric power on tap to fly it satisfyingly on both systems. Prime example is that Me-163 from Durafly--the rocket is there purely for visual effect and adds almost nothing to the performance of the plane. Or more simply, it's a gimmick.

If someone wanted to do an air drop of this model, I'd be game for doing an air start since those are pretty fun.

Not terribly worried about structural failure...That's happened in the past but hasn't happened lately. Apparently I'm capable of learning!

Were this a purely electric model, 3 EDFs would be the way to go. As it is, I'm seriously considering hiding retracts inside those outboard nacelles. They'll be a homebrew custom rig based on my work with rubber powered models. Those looking to duplicate this model will find most of it easy, but this part, probably not so much. I'll supply the dxfs of the fittings anyway.

 

[FAI-F1D]

Whelp, I'm ready to cut some wood this evening:

 

[Pilot_35]

Looking good! Can't wait to see it fly. If you had 3 EDF on a 20-25inch wingspan you could have a super fast plane. Good Luck with the rest of the plane!

 

[FAI-F1D]

And there are parts!

 

[DamoRC]

Mmmmm - pointy - I like pointy.

DamoRC

 

[FAI-F1D]

I got the profile scale model built and flying. I've attached the instructions below. Full size plans will be forthcoming.

The model flies quite well all things considered. It's definitely not a performance machine, but it's stable enough to get the job done, which was my main concern. I see no tendencies toward Dutch roll or uncontrollable spins. There is some tendency to drift into a deep stall when certain boundary conditions are applied, but moving the CG forward a little eliminates this as an equilibrium state.

Here's a flight video:

 

[FAI-F1D]

Well this has sat idle for too long. I'm on track to be able to laser cut the entire thing in just a few months anyway, so let's get back to designing. Here's my current track on getting this airplane drafted out. Definitely gonna be a fun bird, and small enough to be easy to deal with. It'll definitely do over 100 mph on an Estes D12. Should be just scary enough to get people's attention.

 

[FAI-F1D]

Airframe components are here!

 

[JTarmstr]

Airframe components are here! View attachment 115588

With three D class rockets wouldn't this be considered a E class rocket? Good luck with the build. Also, maybe you could share where you buy your balsa from? The stuff at my local hobby shop isn't that hard compared to the stuff from Estes.

 

[FAI-F1D]

That super hard balsa isn't good for planes. Get the good C-grain from Sig, or better yet, buy contest grade C-grain from specializedbalsa.com (my preferred supplier).

3 D engines would put this into F class, but would also shred it to bits at nearly 300 mph. So instead it's going to launch on a single D, or better yet an Aerotech E6 which will give almost 10 seconds of power at 80-100 mph and put this thing 500-600' up. I reckon some of my cheating ways should be acknowledged: I'm basing this setup off the Dynasoar Rocketry designs.