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Help! 4 TAIL SURFACE/SERVO EDF SR-71 DTFB?

#1
Anyone attempt it? I have a Testors hard plastic model to build for me other half (The Black Bird is her baby!). Suddenly in my mind I saw the long body and integrated wings and tall rudders of this bird in brown foam board. But not two, but two EDF's in each long engine pod.
1. How do you control a plane with 2 rudders and 2 elevators/elevons?
2. I heard someone talk about pairing up EDF's (Kind of) inside the nacelle's of the massive A-10. Can that be done? And How?
3. Anyone ever really try it? Like not just 60 inch length, 100 to 120 inches? 2000px-Lockheed_SR-71A_3view_svg.png
 

Brett_N

Active member
#2
You need a pair of Y cables and 4 servos and setup Elevons.

Radio mix to Elevon, and 1 servo each to the elevator and ailerons. Skip the rudders, you don't need them. If you really want rudder action, just run a single servo in the center and send it out to both rudder assemblies.

AS for Dual in line EDF's - don't bother. You'll end up with way too much compression on the aft EDF which will only cause higher current draw.

The giant A10 uses regular old motors and props, they are just inside a nacelle.
 
#3
You need a pair of Y cables and 4 servos and setup Elevons.

Radio mix to Elevon, and 1 servo each to the elevator and ailerons. Skip the rudders, you don't need them. If you really want rudder action, just run a single servo in the center and send it out to both rudder assemblies.

AS for Dual in line EDF's - don't bother. You'll end up with way too much compression on the aft EDF which will only cause higher current draw.

The giant A10 uses regular old motors and props, they are just inside a nacelle.

And the A10 motors were horrible inefficient. The 2 motors in line still only produced the same amount of thrust that one of those motors typically generate.
 

DamoRC

Well-known member
Mentor
#4
Ten feet long and five wide, she'll be a beast (a big beautiful beast). If you build light (really light) I'd say she might come in 8-10lbs? Twin 90mm EDFs might just about cut it. 4 x 70mm EDFs (two side by side in each nacelle) would probably be okay.

I'm guessing a ducted prop will not be a great option because of the length of the nacelles.

Good luck!

DamoRC
 
#6
PoorManRC, AF Rocks! And I say that as a Army Vet. LOL. I've been meaning to go visit the closest Blackbird we have here at the Evergreen Air and Space Museum. You know, Spruce Goose? On the internet I can say I've know her intimately... twice. In a word, "DANG"!
I have a 1/48 from Testors I have on my indoor bench. I'm going to attempt to simulate the exhaust with LED's inside the nacelles. That and some fine frosted plastic thread.
But to build a granddaddy bird.... ah. Next one step at a time build. Was thinking cross-hatch cut internal central box frame fuselage support, but which direction should the wing spars go. When you run up the external specs for size will it be pretty apparent? I hope so.
 

PoorManRC

Well-known member
#7
That's funny - I'm building the SAME Testors Kit!! It was a gift, and I already have the 1:72 version....
My Dad Flew the superlative SR-71 Blackbird!!!! 1969-74.

The spar would baffles me, in a Foam Core Plane. Possible, but difficult. I suppose you could make a matching pair of Spectacle shaped Spars, to go across the Fuse, Nacelles and Wingtips - mounting them in sort of a "X" shaped pattern.
I WISH that Kelly Johnson was still alive. He was a wealth of knowledge for this 12 year old boy.....

Evergreen.... There's one of the Museum on my list, when we're able to do our driving US tour.
 
#8
McMinnville Oregon (Or Ore-gun!), is the city for EVERGREEN. Take 99W south out of Portland, and take the Ocean Beaches Cutoff before McMinnville. Takes you right in front of the place. If you get a chance ask your dad if he ever heard of scramble flights with an unknown passenger strapped into the Camera Officers Seat. Euro to Continental US, or Asia to US, or back. Would have been logged as a Training flight, or Update/Repair to Cali, Cali to Home Base flight. (With an East Coast quickie stop.)
 
#10
Ah, the HABU. First time I saw one was an emergency landing at Pope AFB. The first (but not the last) time someone told me the classic military line, "What you think you just saw does not exist. Understand?" "Saw what sir?" "That's what I thought. Carry on."
 

PoorManRC

Well-known member
#11
@Scooter The White Rabbit - That's truly funny!! Growing up on SAC Bases was "interesting". Security was the tightest I'll ever see in my life.
Sometimes a little over zealous.... One time, a SP put a M16 in my Mom's Face!! SHE didn't think it was funny. She wanted straight up to the most stars she could find, and had him Court Marshalled!!!

To this day, I still have to ask how much info I'm allowed to share from Beale.... NOT that I have incredible Secrets from when I was 11 years old!!! But some things are STILL Classified to this Day!! :eek:

Something recently declassified, that you might be interested in....
The "new released speed" is now 3.43 Mach. New Official Ceiling is 95,000ft.

IMG_20091214_214425.jpg

Tell me.... Does THIS look like 80,000ft!!?? My Dad took this in 1972, and has been cleared!
 
#12
"Space, the final frontier..." Oops, sorry. I know about the sometimes silly security protocols. I'm told even though I've been out totally since '92 my clearance is still active. I think mainly just so if I accidentally leak something they have a handle on me. "I'm sorry Senator, I have no memory of any action or inaction on my part or any of my fellow soldiers during the time period and locations your speaking of that deal with the subject matter you are talking about."
By the way, LOVE the pic! 3.43 mach and 95 K... wow. Only NASA knows for sure! LOL
 

PoorManRC

Well-known member
#13
I've been out since 95, and NEVER had that much clearance!! :eek: Though as a HABU Brat, my Dad drove a couple of terms into my head..... Most often was "plausible deniability"!!
It was a Cool place to be a Kid. Of course, I had no idea until I was about 38, that He was FIRED AT with SAM Missiles - 478 TIMES!!

Never hit, not even near misses... The protocol was "accelerate and evade"!
 
#14
"Yeah, they've got tone on us." "Okay. Let me juice her a touch in this climb." That's it. That should do it." "Anything coming up?" "A few sticks, but they are about... six miles back." "Sounds good."
 

PoorManRC

Well-known member
#15
That's pretty damn close, my friend!!
They did about 35 Miles per SECOND! Pouring on the Coal, widened an already impossible gap.

Dad said his favorite line after an 'incident' was "Let's do a 360, and get the Hell out of here!!"
.... I sure miss him. Today would have been his 79th Birthday.
 

PoorManRC

Well-known member
#17
"Someone" just "Might" be working on a twin 70mm version.... but that's on a need to know basis...

By far my favorite jet (nuff said.)
Ditto...... But I'm sure I'm partial... :sneaky:;)
Twin 70's huh? Cool!! This might be quite a challenge. Knowing what I know, Rotate was at 170-190 knots.
Landing was at 180-200 knots, but of course easier because she was lighter.

Honestly, I can't fathom doing one in Foam, with basic controls.... I admire anyone who takes on the Challenge! One thing that many people never knew - the Blackbird NEVER had advanced fly-by-wire Avionics.
She was always a Man Handled Bird!!

But, as Dad told me a few times, after he and Lee Ransom had a double Un-Start.....
"She's got the gliding capabilities of a ROCK"

When you do yours, are you doing full flying Tails, or "cheating" with Rudder Tabs? Mechanically, I think it would easier to swing the whole Tails.... At least as far as the mechanism to connect the two of them.
 
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#18
My cheat. My dad was a senior photo interpreter for the U-2 and the Blackbird out of Henderson AFB, NV. That's a where I was hatched ya know! So Carmine, we be 2 of a kind, don'tcha know! Tail rudders that don't pivot in the slot? Never! I've got two old white PLA cutting boards (I think their PLA) that I use for plastic bearings. Works Fabulously! Even tapped a few tubes to mount on the end of a stick that slip into a outer tube as a no lube pivot point. Hmm... "It don't mean a thing if it ain't got that swing! Do-whop do-whop do-whop do-wow!"
 
#19
Now the Black Beastie did have some... assist systems and hydraulics, (mostly useless from what I've heard, one system upgrade even caused a crash), but not much more. She... liked to fly, wanted to fly, but you had to stay on her every second. Even with the Auto-Pilot on. And no one can believe in the roll out shots on the ground, that vapor trail following her everywhere was leaking fuel! Cold on the ground she was a leaking black knife, to heavy to take off with full tanks. "Leak-y Teak-y!"