Hobby Labs SR-71

So I stumbled across this in my archives. To my amazement it was ok after all these years. Flew it back in 2007 as a electric pusher. It flew pretty well too.

But now I want to do the obvious, rocket the darn thing. Did take long to strip out the landing gear and the old Astroflight early brushless motor and ESC.

It's very light. I covered everything up. I need to add the launch lug back or should I go with raile buttons?

Last question(and Frank I know you are watching) what motor did this take or Frank will one of your Aerotecks work on this?

I'd get rid of the terrible sliding mixer tray and put in small servos in each wing. These used plugged aerotech e15 motors, they redesigned them to be e20 motors at lower overall impulse but still call them e15 they boosted very fast your boost trim needs to be spot on. If you can keep it under 14 oz rtf you could use an e6 and it will be less stressful to boost. The fragile neck is the weak point on these models if you have a bad landing and prang it.

Isn't there some way that the neck could be reinforced with carbon fiber tubes?

I have this mental image of cutting it in two at the point where the body gets wider, then using carbon fiber tubing, to create some pins that would slide inside of larger diameter carbon fiber tubing. Perhaps with a rare earth magnet (or two) to lock the two pieces together. Sure it'd add weight, but at least it'd be less likely to get damaged in a harder landing if it's done right.

if you havent done it, paint the bottom white. hard to tell which way is up in the air.

rail buttons. definately.

burkefj said:

I'd get rid of the terrible sliding mixer tray and put in small servos in each wing. These used plugged aerotech e15 motors, they redesigned them to be e20 motors at lower overall impulse but still call them e15 they boosted very fast your boost trim needs to be spot on. If you can keep it under 14 oz rtf you could use an e6 and it will be less stressful to boost. The fragile neck is the weak point on these models if you have a bad landing and prang it.

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Frank I didn't know it ever had one. Horrible idea really but I do remember them. It has two HS55s on elevons. Done deal. So far it's under the target weight by 2 oz.

K'Tesh I only ever flew this on gear and a pusher prop and so far I haven't snapped the head off.

Tom that's a good idea, or orange.

I still have the HobbyLab SR-71. I have repaired it and it could fly again, but I haven't been anxious to fly it. I think this is the second HobbyLab SR-71 that I have owned. In general I have had trouble getting it to fly correctly. I am not sure that it gets high enough height on an E15. On the first few flights it probably got plenty of altitude, but I think my repaired model maybe got too heavy. The remote controller does not have any kind of flip-switch to give constant up-elevon for the glide mode, so the user needs to work in enough trim control or hold the stick correctly. This is something that I have not been good at.

Dump their radio setup and get a new TX with Elevons in the menu. The new one I got is telemetry and 6 channels all under 300 bucks. It has a 250 model memory and every bell and whistle you could ever want. It's the black radio pictured in the thread. A DX6.

SteveNeill said:

Dump their radio setup and get a new TX with Elevons in the menu. The new one I got is telemetry and 6 channels all under 300 bucks. It has a 250 model memory and every bell and whistle you could ever want. It's the black radio pictured in the thread. A DX6.

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Steve, I'll give it some thought. I think I will weigh it first and see how close the model is to 14 oz. I already have the DX6e. It has been a few years since the last repair. At the time I saw the mechanical mixer tray that Frank has talked about. I think at the time of the last repair the SR-71 had split by it self and it was easy to seal everything up before looking inside. I would need to cut into it now. The mechanical mixing still works. I'll give it some thought. I have four E15's in my inventory.

OK, I just weighed it and found it to be 13 oz without the motor and the four AAA batteries.

Going back 4 or 5 years I see that I had several posts on the SR-71. In this post you can see the mechanical mixer tray behind the receiver.

https://www.rocketryforum.com/threads/r-c-sr-71-hobby-lab.25663/page-2#post-743474

It is an interesting set-up. You can see that one servo is dedicated to moving the tray that the second servo sits on. Conceivably, knowing the rough location of everything, one could go in and do a lobotomy and set things up for the DX6. Interesting.

3 videos the first ones from 1999 and that's the original hobby lab SR-71 flying on an e15 and you can see how fast it boosts and how fast it comes in, the second one is Mike hit that I made flying on e20s which are now what Aeroteh makes in a plugged motor they don't actually make any e15 anymore they're quite a bit faster boost, the last one is Mike it flying on an e6 all weigh about 13 ounces ready to fly. My cat was about 20-30%% larger and you can see it lands quite a bit slower.

Frank I think I'll just get your next month. Bigger. Lighter. Flies like and plane instead of a brick. Nice!

I like that. That's how a glider should fly!. Floating about in mid air is neither gliding nor flying which is why I've never bought a certain manufacturers kits as nicely done as they are.

c17253 said:

I like that. That's how a glider should fly!. Floating about in mid air is neither gliding nor flying which is why I've never bought a certain manufacturers kits as nicely done as they are.

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I appreciate the sentiment on wanting a rocketplane to fly like a rocket, however you do understand that what you call floating in mid air is actually flying, just because there is a headwind and there is little ground speed the airplane doesn't care there is still airflow over the wings generating lift You can balast any model up and get it to penetrate the wind if that's your thing.

Here is some more fast flight for you...

I have one of the free flight Hobby Labs SR71. Have not flown it. Any suggestions on motor choice.

Brent said:

I have one of the free flight Hobby Labs SR71. Have not flown it. Any suggestions on motor choice.

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E-20-4 is the closest thing Aerotech currently makes to an E-15-4 which I think was recommended

burkefj said:

I appreciate the sentiment on wanting a rocketplane to fly like a rocket, however you do understand that what you call floating in mid air is actually flying, just because there is a headwind and there is little ground speed the airplane doesn't care there is still airflow over the wings generating lift You can balast any model up and get it to penetrate the wind if that's your thing.

Here is some more fast flight for you...

Click to expand...

Yes that's true but I still stand by my statement. Floating defeats the purpose of building a glider.