rocket appropriate for D12-7?

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bjphoenix

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I found 3 D12-7 in my stuff and that means I need a new rocket to use them. My D rockets are more like the Estes Executioner, not appropriate for 7 sec. delay. I scanned some older Estes catalogs to find some that should use the D12-7 and found the Hi Flier XL with BT-60 airframe and 31" length. I'm thinking a BT55 airframe rocket would work also but might get that much more altitude and I don't want to lose it and have to build another. BT-60 airframe seems like the best compromise. The Sprint XL might also be appropriate although it doesn't list the D12-7 as a recommended engine. The Hi Flier XL is cheap enough that I wouldn't be too hurt if it punches through the clouds and doesn't come back.
 
Red Nova?

https://bellevillehobby.com/product/estes-red-nova-model-rocket/

The D12-7 was the recommended motor for the original Goblin. Looks like they recommend the D12-5 for the reissue. Wonder what changed to make the difference?

https://bellevillehobby.com/product/estes-goblin-model-rocket/

https://www.ninfinger.org/rockets/catalogs/estes75/75est18.html

EDIT: Looked at the Estes website -- D12-7 is still recommended for the Goblin

https://www.estesrockets.com/rockets/by-engine/c11-and-d/007236-goblintm
 
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A recommended engine that has a long delay implies greater altitude, that is inevitable. Might be because it's a smaller, lightweight rocket, like the Goblin, or a two stager like the Extreme 12. By the way, if you launch the Goblin on a small field with a D12, it will go outta sight. Lost mine that way. Use a C11 instead.
Does it have to be an Estes? Many other manufacturers out there. Here's a cheap two stager that can use a D12-7 for the upper stage, by Custom Rockets:
https://www.erockets.biz/custom-flying-model-rocket-kit-galaxy-10058/
Good way to learn about multi-staging. And about half the price of the Estes Extreme 12, and about the same price as the Goblin. But oh, so much fun!
 
A recommended engine that has a long delay implies greater altitude, that is inevitable. Might be because it's a smaller, lightweight rocket, like the Goblin, or a two stager like the Extreme 12. By the way, if you launch the Goblin on a small field with a D12, it will go outta sight. Lost mine that way. Use a C11 instead.
Does it have to be an Estes? Many other manufacturers out there. Here's a cheap two stager that can use a D12-7 for the upper stage, by Custom Rockets:
https://www.erockets.biz/custom-flying-model-rocket-kit-galaxy-10058/
Good way to learn about multi-staging. And about half the price of the Estes Extreme 12, and about the same price as the Goblin. But oh, so much fun!
I fly my Goblin with a D12-7, with as little wind as possible and a shiny metallic streamer about 5' long. Impressive flight Md haven't lost it in 3 attempts.
 
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And I would add to the aforementioned Semroc Cherokee D and Magnum Hornet, the Semroc Magnum Sprint, if you can find one. They all top out at around 1300' on a D12.
 
I vote for the scratch build 2 stage - grab some D12-0s and you will get some altitude for sure and need every bit of that 7 seconds :)
 
The local club has a big field but I still prefer to keep them in sight.

The last rocket I launched out of sight was a BT50 rocket on an aerotech SU F72. It was out of sight once the igniter lit. I don't think it launched, I think it teleported into another dimension. So I prefer to keep them in sight, at least just a tiny little bit.

And thanks for the suggestions, I'll check them out.

I have a clone of an Estes Apogee II (without the payload compartment). I haven't had the courage to launch it yet.
 
The local club has a big field but I still prefer to keep them in sight.

That's an interesting problem. I guess you need a longish and relatively light-weight rocket? Something that you will be able to see at the altitude from which it will safely recover on a 7 second delay.

Just because I have an Open Rocket file for the Red Nova

Screen Shot 2018-11-30 at 9.33.41 PM.png

At 230 meters a 55cm long rocket would subtend a visual angle of about 0.13° (about 8 arcminutes). Depending upon the conditions, and the health of your eyes, this should be easy to see as it arcs over at apogee.

I have a clone of an Estes Apogee II (without the payload compartment). I haven't had the courage to launch it yet.

With an A8 in the sustainer and a streamer, the Apogee II is a good small-field flier. From where we set up the pads, at our club LPR field, it is between 250 and 300 feet to the trees in pretty much any direction. The only time my Apogee II has gone out of bounds was when I used a Quest A6 in the sustainer. It was along walk to get most of it back (the ejection charge separated the payload section which ricocheted off a utility pole and disappeared into the understory).
 
Currently contemplating putting out a kit called Katana-D.
Specifically designed and made for the "Mighty D" engines to maximize performance.
Does not use TTW fins, but papered w/mounting tabs.
If you have RocSim (I understand OR can open RS files) I attached the file.
Over 2150' altitude, and still rising upon deployment on a 7 second delay at almost 20' per second.
Very simple and easy design for small rocket performance junkies.
 

Attachments

  • Katana-D II.rkt
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With an A8 in the sustainer and a streamer, the Apogee II is a good small-field flier. From where we set up the pads, at our club LPR field, it is between 250 and 300 feet to the trees in pretty much any direction. The only time my Apogee II has gone out of bounds was when I used a Quest A6 in the sustainer. It was along walk to get most of it back (the ejection charge separated the payload section which ricocheted off a utility pole and disappeared into the understory).

I found my Apogee in the closet recently, I forgot I even had it. It was laying there loaded with B.8 motors.
 
I bought an Estes Hi-Flier XL and built it but haven't gotten a chance to launch it yet, I'm waiting for a calm day.
I noticed that the WRASP rocket database lists recommended motors for different rockets. I found 40+ that work with D12-7!
 
Estes Maxi Streak, and Goblin, Red Nova, Hi-Flier XL, Show Stopper and Black Brant II come to mind if you want stock kits.

If you want to upgrade motor mounts then the Big Bertha, Citation Patriot, M104 Patriot, Der Red Max are a good start. I fly my Big Bertha with the 24mm motor mount on the D12-7 all the time. Perfect rocket for that motor.
 
I fly my Goblin with a D12-7, with as little wind as possible and a shiny metallic streamer about 5' long. Impressive flight Md haven't lost it in 3 attempts.

Ive managed 4 successful flights and recoveries with aerotech f44's in mine, its a hoot!
 
That's an interesting problem. I guess you need a longish and relatively light-weight rocket? Something that you will be able to see at the altitude from which it will safely recover on a 7 second delay.

Just because I have an Open Rocket file for the Red Nova

View attachment 367947

At 230 meters a 55cm long rocket would subtend a visual angle of about 0.13° (about 8 arcminutes). Depending upon the conditions, and the health of your eyes, this should be easy to see as it arcs over at apogee.



With an A8 in the sustainer and a streamer, the Apogee II is a good small-field flier. From where we set up the pads, at our club LPR field, it is between 250 and 300 feet to the trees in pretty much any direction. The only time my Apogee II has gone out of bounds was when I used a Quest A6 in the sustainer. It was along walk to get most of it back (the ejection charge separated the payload section which ricocheted off a utility pole and disappeared into the understory).
It is a challenge. I assume that keeping it in sight means under 500ft and drift no more than 1000ft with a D12-7. Here's my guess: a rocket that weighs about 200g and a 10mph wind with the rod canted slightly into the wind or using a 4' streamer. For the first motor, don't bother painting it until you successfully recover the rocket. Write your phone number on the tube in pencil.
 
Maybe I am missing something here, but the delay time needs to be tied to the "coast" time of the rocket. The chute needs to deploy close to the apogee of the flight. If you pick you delay by hoping it will open close to the ground you are taking a chance on zippering your airframe.

A D12-7 should be used on something that has a lot of "coast" time like an Estes Vapor. It is a sleek rocket that will continue to go up for quite a while after the engine burns out. If you use a shorter delay it'll still be going up when the chute pops and can result in a zipper

A short fat rocket like a Estes Big Daddy needs something like a D12-5 (maybe even a -3) because when that motor burns out it will slow down fairly fast. If you fly that with a -7 it'll be on it's way down and travelling fairly fast. That can cause a zipper

Just my 2 cents,
-Bob
 
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