SR-71

[sj_h1]

Has anyone built the Estes Sr-71? How happy were you with it? I started one and I can't say that I enjoyed the build much. Your thoughts?
:confused2:

 

[Lentamental]

I got about half way through, but then lost interest for some reason. It was a fairly difficult build, and I really wasn't that talented at the time. I never flew it.

 

[cbrarick]

I've built and flew 2. The first one had about 50 flights before it was replaced - basically I burnt out the motor tube. They fly great on c6's - don't go low on the power, it really needs a kick in the pants to get it going. I'm working on a 38 mm upscale now....

 

[sj_h1]

The instructions don't seem to be that great and the part fit seems terrible.

 

[BobH48]

There were a couple of build threads on the old TRF.

https://www.rocketryforumarchive.com/showthread.php?s=&threadid=25754&highlight=sr71

and

https://www.rocketryforumarchive.com/showthread.php?s=&threadid=28665&highlight=sr71

 

[JStarStar]

I built one about 15 years ago, and modified it to fly with motor mounts in the outboard engine nacelles, with a tail cone on the fuselage. Instead of messing around with internal ducting to eject the chute out of the fuselage, I went with small 8" chutes in the two engine nacelles.

It was a fairly tricky build -- not easy to get the large skins which form the body to seal evenly -- but not insurmountable if you took your time. Of course my modifications made it tougher, but I do not recall it was unusually impossible to build.

It came out looking real nice and flew fairly decently, although it rolled slowly after being launched -- never really did figure out whether one of the wing/rudder surfaces was slightly out of whack, or possibly I had slightly misaligned the motor mounts, but in any case, it rotated probably once a second or so under powered flight.

Unfortunately it was lost along with a carton of about a dozen rockets which got waylaid when I moved about a decade ago, so I'll never know, unless I decide to build one again (which I suppose I just might do someday).

 

[thunderdog]

Hi,
Have built and flown 3 over the years all flew fine and have one in my build pile now a hard build but i always found it worth it.:clap:

 

[sj_h1]

The instructions did not say what to line up for the the wings, leading edge or trailing edge. The tube 1/4 inch longer than the wing root. Turns out that it needed to be the leading edge and I guessed right. With the nose cone on, there is about 1/8 inch gap between the shoulder of the nose cone and the top of the wrap, which is all the way to the tips of the wings. Not real happy :y:

 

[Micromeister]

Has anyone built the Estes Sr-71? How happy were you with it? I started one and I can't say that I enjoyed the build much. Your thoughts?
:confused2:

Have to say I Love the SR-71 Estes kit, course, I always 3 C6 cluster my SR-71's which does add a bit to the construction and finishing. but it's always been a favorite of mine, I'm working on a micro downscale that I'm hoping to cluster as well

What exactly didn't you find pleasent about your build? the shrouds perhaps?

it's a pretty decent flying model single motored and outa sight on 3. does required a bunch of added nose weight and over time i've learned that ducting the ejection gases into the main is a great safety should the core motor fail ti ignite. That's only happened once but once is enought to total the model

 

[BsSmith]

I've had one sitting partially built for years, the part fit is awful.

Even if I do finish it, it probably won't fly well, like the one at Midwest power a few years ago. (it was windy though)

 

[sj_h1]

I've had one sitting partially built for years, the part fit is awful.

Even if I do finish it, it probably won't fly well, like the one at Midwest power a few years ago. (it was windy though)

I have to agree with you on that!

 

[cbrarick]

mine just went up again - we fly it everytime we fly anything - high, mid or low power... so it went on a c6-3. It was a great flight, nice recovery... like always.

 

[astropilot]

In TRF's previous incarnation I was known as Starpilot. Since the rebirth, I'm know using the screen name of Astopilot. Hello again!

Now that the introductions are done, on to the question at hand. I have built 2 of the Estes SR-71s. My build thread was one of the one listed above. The build was not all that complicated, but there were a few areas that were a bit 'tricky'. One trick that I used for the skins was to use Aleene's® Tacky Glue® to tack the skins to the top and bottom of the tubes and to the wing leading and trailing edges. This glue 'grabs' quickly but still allows you enough time to get everything positioned correctly before it sets up. After that, ordinary old Elmer's was ran down the joint etween the tube and skins and the wings. This seems to have worked very well, and after a few flights, and one parachute failure, the bird is still in fine shape.

Another trick was to wick some thin CA around the skins where the nose cone fits. This really stiffened up the skin in this "high wear" area of the rocket.

The only thing about the kit that I really disliked was the stickers Estes went to instead of water slide decals.

All in all she is a fine kit and a great flyer.

 

[Verna]

Has anyone built the Estes Sr-71? How happy were you with it? I started one and I can't say that I enjoyed the build much. Your thoughts?
:confused2:

Randy has built two and has flown them dozens of times over the years. He enjoyed the build and had no problems. He said to recommend using Elmer's regular white glue and test fit the paper wraps several times before gluing.

The first one was stock as a black single engine version. It flys well on an A8-3, B6-4 or C6-5. The A8-3 perfectly performs a hammerhead stall. The other one is red and it's a 3 engine cluster. Fairly simple to modify and fly. I'm attaching a photo of it's last flights at the BRB night launch last July. He fly's it on a B6-6 and 2 B6-0's or a C6-5 or 7, and 2 C6-0's. The cluster version will get off the pad very fast. Single 18" chute, could be slightly smaller.

The only drawback on the Estes SR-71 is that if the wraps aren't done correctly they want to tear or fold into the bt where the nc fits after a few flights. We have enjoyed the kits, flying them and have 2 more still in plastic.

Verna
www.vernarockets.com

 

[JStarStar]

Randy has built two and has flown them dozens of times over the years. He enjoyed the build and had no problems. He said to recommend using Elmer's regular white glue and test fit the paper wraps several times before gluing.

The first one was stock as a black single engine version. It flys well on an A8-3, B6-4 or C6-5. The A8-3 perfectly performs a hammerhead stall. The other one is red and it's a 3 engine cluster. Fairly simple to modify and fly. I'm attaching a photo of it's last flights at the BRB night launch last July. He fly's it on a B6-6 and 2 B6-0's or a C6-5 or 7, and 2 C6-0's. The cluster version will get off the pad very fast. Single 18" chute, could be slightly smaller.

The only drawback on the Estes SR-71 is that if the wraps aren't done correctly they want to tear or fold into the bt where the nc fits after a few flights. We have enjoyed the kits, flying them and have 2 more still in plastic.

Verna
www.vernarockets.com

Wow, looks pretty cool.

As I recall, when I did my SR-71 with the modification to install the live motor mounts in the engine nacelles (as opposed to a single motor in the fuselage in the stock build), and then loaded it up for launch, it threw the CG back a couple inches, and I had to squeeze a few spoonfuls of clay into the nose cone to push the CG back forward enough to be stable (this was all by cardboard-cutout and swing-testing, back in the dark days pre-RockSim).

So my first reaction to seeing a 3-engine cluster was, "wow, they must have had to fill the nose cone with lead shot to make it stable," but if you're getting good flights in that configuration, obviously you must be doing things right.

 

[cbrarick]

Here's my next one... M-powered! The big kahuna of SR-71's and it's also correct to scale, unlike the estes one.

rick

View attachment 6 inch SR-71 YF-12 Varient.rkt

 

[Verna]

Wow, looks pretty cool.

So my first reaction to seeing a 3-engine cluster was, "wow, they must have had to fill the nose cone with lead shot to make it stable," but if you're getting good flights in that configuration, obviously you must be doing things right.

Actually, not that much more weight. I weighed the two cones we use and the single engine weighed 0.9 ounces and the 3 engine weighed 2.0 ounces with a lot of room left over. Randy just used modelers clay.

Verna
www.vernarockets.com

 

[Chuck H]

I liked the build. Came out OK but there's some oopses. I thought it should be dual-engine but I'll save that for the next one. I've only flown a few times and it always arcs over backwards and ejects the chute just in time - not sure where the problem is - is there any way to troubleshoot/fix this?

 

[RangerStl]

Make sure there's no set in the wings that would cause it to apply "Up" elevator during flight. Check very carefully to make sure all the aero surfaces are straight.

You can also try to tape some small thin sheet aluminum trim tabs to the wing and bend them until the tendency goes away. Be sure to tape them on the aircraft bottom so when you bend them they give "Down" elevator.

That's what I'd try.

Oh, and SMALL adjustments.

 

[cbrarick]

or try a smaller delay. My current one just loves the c6-3 but is a heart stopper on a c6-5...and the c6-7 would be nosecone to deep deployment

 

[RangerStl]

Oh, yeah... absolutely. I assumed that yours flew an arc under power. If you are coasting up, flipping and coming down before the chute pops, use a shorter delay.

My suggestions apply only if it was arcing over during the powered phase of flight like something was misaligned.

Sorry.

 

[Chuck H]

Arcing under power - definitely "up" elevator somewhere. I thought about adding some kind of trim tab - I'll probably give that a go.