Build advice...please...

I'm about to build an Estes SR-71 Blackbird. Does anyone have any advice on building this beauty?

I will probably build this one and hang it in my office...it's just too awesome looking to have it lost in the trees...

A couple of build threads to start with - this one has a couple of gotchas and hints:

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

Here's another with some pics:

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

There are lots of other threads - do a search for SR71

Greg

It's not a high flier on a C6 if you build it with the stock 18mm motor mount, so you really won't have to worry about losing it in the trees. It stays well in sight the whole flight, and comes down safely on a 12" chute with minimal drift... the blackbird is my favorite model; I have on modded out for 24mm, 2 in the bag, and a spare main nose cone... hmmm, I better get a few more, running low..

I need to rebuild mine (actually I need to build a new one) because it lawndarted and the top 1/3 was damaged beyond repair. The problem is that I don't remember what caused the lawndart. I think it was a bad ejection charge, or maybe the motor was ejected due to a stuck chute.

My advice is to use CA to join the fin sections. It is very difficult to keep the fins straight long enough for wood glue to dry. The fins on my first one were badly warped because the joints were not flat/straight.

Modding for 24mm is definitely recommended. I've had one built with 18mm and it was underpowered. Just leave out the motor mount, and use one of the centering rings from it as a thrust ring and load it with 24mm D's. I saw the one Don Magness (SecretSquirrel, Squirrel Works) owns fly in this configuration and was thoroughly impressed, based on my previous experience with the 18mm flights.

Build it as a 3 18mm motor cluster, or a single 24mm the fly like a bat outa..... great flyers!

Originally posted by Fore Check
Modding for 24mm is definitely recommended. I've had one built with 18mm and it was underpowered. Just leave out the motor mount, and use one of the centering rings from it as a thrust ring and load it with 24mm D's. I saw the one Don Magness (SecretSquirrel, Squirrel Works) owns fly in this configuration and was thoroughly impressed, based on my previous experience with the 18mm flights.

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I'll probably do that ... then make an adapter to accommodate the C motors. I have done this before with other rockets.

Hmmm...what about 1 - 24mm and 2 - 18mm I could use the side tubes for a couple B motors. I am not sure if the wings could handle C's or not.

Originally posted by bigone5500
I'll probably do that ... then make an adapter to accommodate the C motors. I have done this before with other rockets.

Hmmm...what about 1 - 24mm and 2 - 18mm I could use the side tubes for a couple B motors. I am not sure if the wings could handle C's or not.

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Good Lord! Can't take the C's LOL
I've been flying the SR-71 on 3 - C6 motors for a very long time. I'm on the 4th model...Crashed one (center motor didn't ignite see pic below) and have warn out two others. Now I duct the outboard C6-7's into the Core usually flown with a C6-7 or 5 as well ducts are 3/16" x 1/8" rectungular brass tubing 4 pieces soldered side by side cut into each wing tube standoff section starting 3" from the nozzle end. I'm Planning building the next version with 24mm mount with 18mm adapter as you just mentioned. but I'll be using C6's in the outboards

Originally posted by bigone5500
I'll probably do that ... then make an adapter to accommodate the C motors. I have done this before with other rockets.

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Don't try and make tje core interchangeable with a C! If you mod for 24mm (which truly is a must and turns out great performance) you will have to add additional nose weight (no big deal with a D and up). With this additional weight , it will be too heavy for a C to lift.

How much nose weight to add has been discussed on here many times; do a quick search and you'll find the info (around 24 grams I *believe*)

If you want to fly it on a single D or AT reload, great. If you want to fly it on a cluster of a core D and outboard C's... good, just be ready to add even more noseweight and grind down the end of the engine nacelles a little to make room for the 18mm C's in the "engine tubes" just don't try to mod if for 24mm and expect to fly it on a single C... it won't work.

If you do try and cluster it, be aware of how far the outboard thrust will be outside of the center line... If you're not good/experienced at clustering, I would probably not advise you to do said cluster. If one engine lights late, or one lights early, the asymetrical thrust created will make the rocket power itself in an arc and end up thrashing on the ground... If you do this, make sure you have a good 12V power source and some good igniters, and a clip whip to eliminate as many variables for failure as possible.

Originally posted by Micromeister
Good Lord! Can't take the C's LOL
I've been flying the SR-71 on 3 - C6 motors for a very long time. I'm on the 4th model...Crashed one (center motor didn't ignite see pic below) and have warn out two others. Now I duct the outboard C6-7's into the Core usually flown with a C6-7 or 5 as well ducts are 3/16" x 1/8" rectungular brass tubing 4 pieces soldered side by side cut into each wing tube standoff section starting 3" from the nozzle end. I'm Planning building the next version with 24mm mount with 18mm adapter as you just mentioned. but I'll be using C6's in the outboards

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OMG Micro!!!

That is just tooooo awesome!!!

Originally posted by TeenRocketNerd
Don't try and make tje core interchangeable with a C! If you mod for 24mm (which truly is a must and turns out great performance) you will have to add additional nose weight (no big deal with a D and up). With this additional weight , it will be too heavy for a C to lift.

How much nose weight to add has been discussed on here many times; do a quick search and you'll find the info (around 24 grams I *believe*)

If you want to fly it on a single D or AT reload, great. If you want to fly it on a cluster of a core D and outboard C's... good, just be ready to add even more noseweight and grind down the end of the engine nacelles a little to make room for the 18mm C's in the "engine tubes" just don't try to mod if for 24mm and expect to fly it on a single C... it won't work.

If you do try and cluster it, be aware of how far the outboard thrust will be outside of the center line... If you're not good/experienced at clustering, I would probably not advise you to do said cluster. If one engine lights late, or one lights early, the asymetrical thrust created will make the rocket power itself in an arc and end up thrashing on the ground... If you do this, make sure you have a good 12V power source and some good igniters, and a clip whip to eliminate as many variables for failure as possible.

Click to expand...

I have done 3 cluster rockets so far. The clip whip I use is a 4 motor clip that can be used on 2 or 3 clusters too. I used high temp silicone wire and soldered all joints. I have used this whip once and it worked like a charm. See my NoName X4 rocket launch video here: NoName X4 Video I also have plans and a rocksim file here on TRF if anyone is interested... https://www.rocketryforum.com/showthread.php?s=&threadid=27835&highlight=noname+x4 I think I need a larger dia. chute because it looks like it is descending too fast.

I also use a 12v launch controller with most of my rockets unless I'm just going to launch a few small ones, I just use the Estes controller then.

Just to reinforce what TRN posted:
Most important Please test your igniters, before and AFTER they are installed in the motors. Can't tell you how many igniters i've found recently that are BAD right out of the pack! Below is a little 1.5v continuity tester i've been using on all my cluster models to ensure everything is good after they have been installed in the motors.

Also be away the size of the battery (cold Crank amps) , size of the controller wire and distance from the cluster pay a very large part in weather your clustering will be successful or not. a clip whip is only an extension of the controller wire so if your wire can't carry enough amps quickly enough you well likely have one or more motors fail to ignite.

If you have a few minutes I'd offer a Tech-Tip on clustering BP motors in the library section of narhams.org #006 may be of interest if your planning on doing a lot of mod-roc cluster birds
Hope this helps.

Speaking of the Blackbird, John, have you tried downscaling it yet? Given your myriad projects, I'd be surprised if you haven't (besides, gotta replace that plastic brick that Quest sold! )

Greg

Originally posted by gpoehlein
Speaking of the Blackbird, John, have you tried downscaling it yet? Given your myriad projects, I'd be surprised if you haven't (besides, gotta replace that plastic brick that Quest sold! )

Greg

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Greg:
I tried a T4 but it was just toOOOO heavy for 3 micros. I'm hoping to get around to trying a T3 downscale and still be able to get T2+ for the outboards Haven't done the drawing yet so i'm not sure if it's gotta fit, along with the turned nozzles
With all the other junk I've been doing of late I haven't had a chance to build anything really Hopefully by next week things will be back to where I can get back into the rocket dungon and get some of the projects moving again

Originally posted by Micromeister
Greg:
I tried a T4 but it was just toOOOO heavy for 3 micros. I'm hoping to get around to trying a T3 downscale and still be able to get T2+ for the outboards Haven't done the drawing yet so i'm not sure if it's gotta fit, along with the turned nozzles
With all the other junk I've been doing of late I haven't had a chance to build anything really Hopefully by next week things will be back to where I can get back into the rocket dungon and get some of the projects moving again

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What about using cardstock for the engine nacelles, intakes and afterburners? They might not be perfect (I don't remember if they are conical or curved) but 24# paper would likely be strong enough (if not, 67# would definitely be) and would be a lot lighter than turned nose and tail cones and standard tubes.

Greg

Originally posted by gpoehlein
What about using cardstock for the engine nacelles, intakes and afterburners? They might not be perfect (I don't remember if they are conical or curved) but 24# paper would likely be strong enough (if not, 67# would definitely be) and would be a lot lighter than turned nose and tail cones and standard tubes.

Greg

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Can't really tell at this point Greg, as mentioned haven't really seriously looked at the sizes of the components yet.
Ever rolled a .281" to .255" dia cone? Not much to work with Since the tail cones are conical, and I may be dealing with a minimum diameter tube to start with the cone length and taper "may loose it's appeal? at this point I'm just looking to get the slight taper that I can emboss lines in. Balsa will be too soft so basswood, Poplar, Styrene or a built up epoxy may be the trick
Already using 40lb presentation board for the bodywrap, which may have to be reduced to 24lb on the T3 model Ya know I'm sort of a Scale Purist...If I'm gonna do this, it's gotta be PDC to some kind of scale.
Adding the necessary dorsal fins is being considered in .010 clear matte polycarbonate to improve the scale look of the model
Intake cones that's another sticky point.... Pun intended, they are needed IF i intend to make the model a cluster, not as important if just nacelles (like the Quest LPB). I'm REALLY leaning toward clustering....1st Love ya know, so turing either a cone/cowling or recessable cones are both still being looked at.
A further consideration is making the model Nose section large enough to hold the necessary #9 lead shot for get a clustered micro to be stable as well as looking good
Remember MY rocketry Motto... "If it doesn't fly is just another dust collector"
It's looking pretty good for this satruday! I may actually be able to clear my building tables by friday, and get the home computer station back up and running satruday.. So some of the drafting for the MMWW Micro SR-71 may get ON the board then

Actually, John, I HAVE rolled a .255" nose cone. And you are right - rolling that little cone was a royal pain in the donkey!!!

I did a minimum diameter downscale of Der Red Max for mmxII motors, and the nose cone was made from two transitions, a cone and a cylinder. That's why I suggested 24"paper - I was able to roll them from that. The little beast actually flew, too - it was nose blow recovery with just a piece of string for the shock cord.

I'm at work right now, but I'll try to post a pic in the next day or so (don't think I've ever photographed that one).

Greg

Now that I look at it - I think this little bird was made from 67# stock. I think it turned out pretty well, but as I said, those nose cone parts were a royal pain to make!

Full scale mosquito for reference.

Greg

Crud - hit the submit button before adding photo!

Greg

Bigone:
Though you might be interested in seeing the parts used to duct the SR. First is an old poloriod of the rectangular tube ducts in place in the outboard wing spacers with the exhaust nozzle motor mounts and intake heat sheilds. I'll follow with a full size scan of the duct tubes. Turely the precess is a bit of a job but I was exceedingly happy with the outcome This set of parts has at least 30 flights on it. litterally wore out the main body tube

Left is a single section of the 3/32" x 3/16" Brass rectangular tubing used in the sing ducts. I beileve is has about an .030" wall thickness tho I can't remember for sure. Solders up very easily with plain old 50/50 solder.
Hope this helps.