F-22 Raptor This Time (twin tube design)

[hermanjc]

Aside from the dinosaur raptor rocket for my son, I've had another raptor idea in my head ever since I made my upscale Estes SR-71. The F-22 design I came up with is for a twin BT55 body tube for a two motor cluster. Aside from a 3D printed nose cone, the rocket/plane will be made from balsa and paper to shape the fuselage to the wings. I do have a Rocksim model to help figure out CP. I'm thinking of using 24mm motor mounts, but with the maiden on C6-3s in adapters.

 

[Bill S]

Cool idea, I'll be following this one.

 

[KenECoyote]

Wow, nice! I actually dug up this kit last night and thought you were referring to this one.

 

[hermanjc]

Wow, nice! I actually dug up this kit last night and thought you were referring to this one.
View attachment 456065

That's an awesome kit! I found it as I was researching options, but wanted a free flyer like my SR-71. Gonna require a heck of a lot of nose weight I think, but the ability to fly one 2 super C's or 2 Ds should take care of that .

 

[hermanjc]

Wing sections cut and glued and currently under a nice heavy book to hopefully dry flat. Tomorrow I'll paper them, too. I have a set of BT55 tubes on order (didn't have long enough ones in my parts bin).

 

[hermanjc]

Papered wings are done. Designed and printed #8-32 nut holders to join the two body tubes and serve as rail button mounts. Printed and glued on ribs to support the wings against the body tubes and shape the fuselage paper wrap.

 

[hermanjc]

Made fin alignment jigs. Will use them to bond the top scale fins as well as some small belly fins. Rocksim model is nearly finished so I can dial in CG. Measured a total length of 22 inches.

 

[mo2872]

Very cool

 

[hermanjc]

Back to work on the F22 after a vacation. Finished up with some additional paper forming ribs/tube joiners. Also 3D printed some centering rings to make the motor mounts. Top fins have been glued on. Still need to make a tansition for the back of the cockpit the fuselage. I am thinking I'll just shape a chunk of balsa for that. Getting close to paint. I'm loving how it looks.

 

[John_lennon]

The F-22 is really coming along nicely I always liked the SR-71 Blackbirds profile. It's a very cool designed plane.

 

[Huxter]

Yes, it's lookin better and better! That's a damn sexy rear!

 

[hermanjc]

The F-22 is really coming along nicely I always liked the SR-71 Blackbirds profile. It's a very cool designed plane.

A little bit of progress, with the motor mounts now installed and nose weight added. Took out the SR71 for some comparison.

 

[nosecone]

Lookin good !

 

[John_lennon]

A little bit of progress, with the motor mounts now installed and nose weight added. Took out the SR71 for some comparison.

View attachment 464274
View attachment 464275

Yes they're both really cool. Nice work.

 

[hermanjc]

Looking good with some paint. A few decals will be put on tonight.

 

[neil_w]

Your twin-tube fuselage really came out fantastic.

 

[hermanjc]

Your twin-tube fuselage really came out fantastic.

Thank you @neil_w.

Last couple of shots until this bird takes the to the air. Just added some simple decals. I thought about adding thin black lines to detail panels/elevons/etc., but I don't trust my hand to get it looking right.

 

[hermanjc]

Had a successful maiden flight with 2xSuper C5-3s. Trying to determine if the "sweet" arc and roll maneuver into what looked like a pretty steady glide before ejection was due to lift forces from the wings or being a little underpowered. In any case, good flight and safe recovery after dodging power lines and the road. Next flight might be with 2xD12s.



*Apologies for shaky cam and rocket going out of frame, I was much more concerned with watching the maiden from my own two eyes
View attachment F22_maiden.mp4

 

[mo2872]

Very cool!

 

[BABAR]

Nice accomplishment!

good thing both lit, or Goose would have been a goner! (Oops, wrong service)

 

[BABAR]

Had a successful maiden flight with 2xSuper C5-3s. Trying to determine if the "sweet" arc and roll maneuver into what looked like a pretty steady glide before ejection was due to lift forces from the wings or being a little underpowered. In any case, good flight and safe recovery after dodging power lines and the road.

any time anything cool happens and the flight is successful and the model is recovered undamaged and nobody and nothing are hurt, the answer is ALWAYS, “Oh yeah, I meant to do that.”

 

[Nytrunner]

Great build!

It looked like it pitched up (from a pilot's perspective). I'd conjecture that was because of the asymmetrical drag of the fins on the top side

 

[hermanjc]

Great build!

It looked like it pitched up (from a pilot's perspective). I'd conjecture that was because of the asymmetrical drag of the fins on the top side

Thank you, @Nytrunner.
I think I will try adding belly fin's (similar to the Estes SR-71 construction) and try a second flight with C5-3's before I move on to D12's.

 

[BABAR]

Great build!

It looked like it pitched up (from a pilot's perspective). I'd conjecture that was because of the asymmetrical drag of the fins on the top side

Probably right. Your alignment was probably TOO good. My asymmetric fins usually result in a corkscrew, so in a way it is self correcting so the net trajectory is straight. Your perfect alignment and those big wing fins probably prevented rotation/corkscrewing. Some ventral plumage should to the trick.

 

[hermanjc]

I have attempted 2 more flights since the maiden, each with the same pitch over result. First I tried adding belly fins with the hope the added drag would fix the problem. No such luck, but the Raptor almost landed in the bed of my truck (instead it found itself parked between my truck and my brothers car).



View attachment F22_20210620_red.mp4

Next I added some deflected flaps to the belly fins, but there was no noticable improvement on the pitch over, and if anything they reduced the jet's want to roll into a stable flight prior to ejection.

Note: this picture was taken post flight, and one of the flaps had mostly broken off on landing.


View attachment F22_20210724_red.mp4

Next I will remove the flaps, and instead try adding ailerons to the trailing edge of the main wings. I might 3D print a few at different angles that attach with small screws vs glued on balsa so that if I get some success on a first try I can attempt to tune it in.

 

[Nytrunner]

Worth considering, your intake ramps are also solid plane surfaces angled so that airflow will add to the pitching moment.

I would have predicted that the fins you added would have some corrective effect on the flight at least, but there doesn't seem to be a noticeable difference in either the videos, or your own firsthand account.

Bummer

 

[mo2872]

Looks like some down elevator(via tabs) would keep it going vertical.

 

[hermanjc]

Looks like some down elevator(via tabs) would keep it going vertical.

Some down elevator it is.

 

[OverTheTop]

Adding wedges on the top rear of the wings could help also, and not be prone to breaking off. Adding wedges is a method used frequently to make sounding rockets spin, by adding them to the aft end of the fins.

 

[BABAR]

Downward elevator certainly may help, but if you pick different motors, you may end up literally chasing your tail.

the amount of elevator deflection at one airspeed (C5-3 motor) may not be the same for another airspeed (D12-3). Plus you may have account for change in CG, certainly not negligible in a two tail motor bird.

you miiiiiiight consider a little asymmetry on you elevators to cause a mild intentional roll, this is sometimes used (I think in boost gliders) to correct an arced flight by continuously redirecting and hopefully neutralizing the arc.

I am thinking that the bird may be a bit sensitive to the asymmetric dorsal fins, especially as the extended forward wing surfaces (kinda like the “chines” on the SR-71) may start acting like forward canards when the rocket starts to tip.

great looking rocket!