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Moving from BP motors to composites. Maybe.

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Dane Ronnow

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Over the last few weeks, I've posted a number of questions concerning a scratch-built 2.6" rocket, designed for a cluster of three E9-8 BP motors. Over the course of discussions rising from those questions, I've learned that E9 engines may be unreliable to a point of destroying the rocket. Researching E9 failures on the MESS web site, I've learned that E12 BP motors—which were a second (albeit undesirable) choice to the E9—have a greater incidence of failures.

[Note: As far as I can tell, MESS statistics don't provide a baseline for failure stats, only the failures. So we can't say, "X percentage of these motors failed." Only "X number of these motors failed." So MESS stats are not meaningful to me.]

Discussions of the clustered E9 motor led to discussions of the (probable) need to modify Estes igniters with some type of pyrogen to improve reliability of clustered-motor ignition.

Then I asked a question concerning ejection pressure from three E motors, and the possibility of blowing out the lower body tube. That brought to light speculation concerning the ejection baffle, and possible use of one or two (of the three) motors having no ejection charge, which exposed the fact that the E9 is not available with a 0 delay, or plugged. E12s do, but I can't use one or two E9s and one or two E12s (obviously).

That brought me back to the idea of using E12s. And that moved me to seriously consider chucking the idea of using a cluster, and, in fact, BP motors altogether.

So now I'm looking at Aerotech single-use motors, and learning all I can about them. And coming to grips with the fact that it's becoming more expensive to fly this rocket once it's built.

Anyway, I look back over the long haul and I have to chuckle. At the rate I'm going, I'll still be working on this rocket when the cows come home. I guess it's some consolation that I can fly it in OR. And hey! So far it hasn't blown up!

I want to thank all of you who contributed ideas and advice. It's been a valuable learning experience for me.
 

aerostadt

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There is a question in my mind about how easy is it to get 3 composite 24 mm motors to fire all at once. I'm currently building a test rocket to ignite a cluster of two 24 mm composite motors. I am encouraged by the recent success of seancarroll, who got a cluster of 3 composite 29 mm motors to ignite all at once.
 

Dane Ronnow

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There is a question in my mind about how easy is it to get 3 composite 24 mm motors to fire all at once.
If you're referring to my 2.6" rocket, what I meant (and probably didn't do a very good job at conveying) was I'm now thinking of abandoning the cluster idea, and switching to a single composite motor, most likely a 29mm. As far as how easy it would be to get three composite motors to ignite simultaneously—or one motor, for that matter—I don't know. When it comes to composites, I'm brand spanking new.
 

neil_w

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As I have said now on a number of threads, flying a single-use composite motor is not significantly different from flying a BP motor. Igniter insertion is a bit different (but not hard), and you need to make sure your launch controller has enough juice but really it's the same experience overall.

Reloadables are a different story of course, but you don't need to jump into them right away. Stick an Economax F67 in there and it'll get that rocket moving, no problem, for about $16 a launch.

In my LPR/small MPR fleet I use a mix of BP and composite motors. It's very nice, when the need arises, to be able to pull out a motor that absolutely has more than enough thrust for a given flight.
 

Mike Haberer

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There is a question in my mind about how easy is it to get 3 composite 24 mm motors to fire all at once. I'm currently building a test rocket to ignite a cluster of two 24 mm composite motors. I am encouraged by the recent success of seancarroll, who got a cluster of 3 composite 29 mm motors to ignite all at once.
The key to composite clusters are choosing the right motors and the right igniters. Blue thunder is the easiest to ignite (a lot of people use slivers of blue thunder on large composite motors along with the igniter to light difficult to light propellants like Redline and Green Mojave). White lightning also ignites easily. Research the best igniters here on TRF. A lot of people like Wildman's.
 

Daddyisabar

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Don't trust your eyes, they can decive you. Only opinions and past advice will you find here. Reach out with your feelings and fulfill your model rocket destiny. Keep your mind on where you are at, what you are doing. Younglings , heed the advice of the masters but you must find your own way in constructing ever more complex rockets. Blasters are so uncivilized and do not underestimate the power of the dark side. Be selfless and pay forward. Practice good science and stay safe. These are the ways of the Jedi. We will be watching your career with much interest.

Yes, you are a rocket scientist!

E9 and E12 CATO fear: Fear is the mind killer.

KISS. Keep it simple stupid, until you are ready to move on.

Trust in thrust. Power and nose weight can solve 90% of your problems and that ain't bad.

Build light, build strong.

May then Force be with you. Have fun.
 

Dane Ronnow

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Stick an Economax F67 in there and it'll get that rocket moving, no problem, for about $16 a launch.
I'd like to sim that motor in OR, but it's not listed in the database. And I can't get thrustcurve to bring it up. You wouldn't happen to know where I can find a motor file for the F67 that I could drop in OR would you?
 

samb

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Don't trust your eyes, they can decive you. Only opinions and past advice will you find here ...
And never ever expect a straight answer from Daddy. 🙃 Always entertaining and frequently accurate (spelling excepted) but never straight. He flies airplanes with rocket motors in the nose for goodness sake ! :)
Have you found any locals to fly with ? I've found it useful sometimes to filter all the answers you get online through some real live crusty old steely-eyed model rocketeers.
 
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Rocketjunkie

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Never had a problem with E9's (163) and E12's (30), all from Hobby Lobby and AC Supply. 3", 24 mm Ultimate on 7 E9-s
4 stage rack rocket on E12's
The Ultimate loves a 24 mm CTI G motor and air starting 6 Estes BP motors (with fuses lit from the central G).
 

Daddyisabar

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And never ever expect a straight answer from Daddy. 🙃 Always entertaining and frequently accurate (spelling excepted) but never straight. He flies airplanes with rocket motors in the nose for goodness sake ! :)
Have you found any locals to fly with ? I've found it useful sometimes to filter all the answers you get online through some real live crusty old steely-eyed model rocketeers.
I always get The Straight Story from the old steely-eyed model rocketeers. So what if they have lost their license and have driven cross country to the launch on their John Deere garden tractor. :)
 

samb

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I always get The Straight Story from the old steely-eyed model rocketeers. So what if they have lost their license and have driven cross country to the launch on their John Deere garden tractor. :)
Yes ! A Richard Farnsworth movie reference. Outstanding as always Daddy. :)
 

Dane Ronnow

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. . . flying a single-use composite motor is not significantly different from flying a BP motor.
It's my understanding that composite motors—at least F and G Aerotechs, which is what I'm looking at now—have a paper or plastic cap that blows off at ejection. If I shorten the motor tube so it's flush with the forward centering ring (making it 4.5" long) so I can shake the ejection caps out the bottom, would there be a problem with longer motors sticking out the front of the motor tube?
 

neil_w

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It's my understanding that composite motors—at least F and G Aerotechs, which is what I'm looking at now—have a paper or plastic cap that blows off at ejection. If I shorten the motor tube so it's flush with the forward centering ring (making it 4.5" long) so I can shake the ejection caps out the bottom, would there be a problem with longer motors sticking out the front of the motor tube?
No problem at all.
 

Dane Ronnow

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Younglings , heed the advice of the masters but you must find your own way in constructing ever more complex rockets.
I'm not young (69), but I am new to the current state of rocketry and scratch-building rockets (I flew kits when I was a kid). So this was on-point for me. In fact, your entire post was some of the best advice I've received since I joined TRF. And, as an old guy, I can comfortably call it sage wisdom. Thank you, sir!
 

Joekeyo

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perhaps with the new Estes Mabel actually designed to create large BP motors, the motors will improve.
Bill Stine talked about improving the E12 this year . The customers complain the manufacture responds. Estes has been in business for over 60 yrs. maybe that's part of the reason. I wouldn't throw the baby out with bath water.
 

Dane Ronnow

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Have you found any locals to fly with ?
Just now getting to know them. I went to the last launch Tripoli Vegas held (they fly every third Saturday on the Jean Dry Lake Bed) and met a few of them. Looking forward to meeting more this coming Saturday.
 
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Dane Ronnow

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make sure your launch controller has enough juice
Sorry to pepper you with questions, but I want to nail this down, and I know very little about volts, current, resistance, etc.

I've got an Estes PSII launch controller that has the six 1.5v C-size batteries internally. When I was working toward a three-engine cluster, I was going to add an external 12v 7.2Ah SLA batt, wired to the PSII through the Deans connector, replacing the C batts. That was based on the need for 2 amps per igniter.

Would the 9 volts internal supply be enough for the FirstFire Mini that comes with the F67? Or should I plan on using the 12 volt external SLA for a more comfortable margin?
 

neil_w

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I believe the PSII controller should be fine; that's what it's designed for.
 

boatgeek

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The PSII will probably be OK, though the C batteries don't put out as much current as the LiPo or other chemistries. If you happen to have another battery around, no reason not to plug it in to the red JST connector. If you have reasonably fresh C cells, they'll work for a while. It's just frustrating on the day that they suddenly decide that they're not going to light your igniters.
 

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I personally feel that the fear of the E9 and E12 are grossly over exaggerated and overblown. Do they CATO? sure they do, that has been proven but so do other motors. My person experience with them has been perfect. Looking at my flight log since returning to rocketry, I have flow 86 of the E9 and 103 of the E12 motors. In 189 flights, I have had 0 failures. Don't fear those motors. If you have them, fly them.

I'm not a fan of clusters. I build a few rockets with them but for the most part I don't care for them. Seems like a waste of money to me. Burn 3 Estes E12 motors or burn one F44 for the same performance. Or in the case of the Semroc Ranger/Bertha twins. Burn 3, C6-7's for 1200ft or burn 1, E12-6 for 1300ft.

As for composites. I popped the composite cherry about 18 months ago with an E20-4 in a LOC Graduator. The launch process for single use Aerotech motors is simple. The igniter gets inserted all the way to the top of the motor as they burn from the top down. The first couple can be tricky as the igniter doesn't always want to go all the way in. Just play around with the motor for a few minutes the day before launch and get a feel for it. Once you launch a composite you will be hooked and suddenly the fear of building a rocket too large or too heavy goes out the window. Flying composites opened me up to manufactures I didn't know existed. The other thing that surprised me was that my regular Estes controller with 4AA batteries launched it just fine. But then again, I've launched 3 motor clusters with it as well which people have said can't be done. Don't get me wrong. The Estes Pro controller is a million miles better but the standard on will work with fresh batteries.

As for cost. Yeah they are a little more expensive depending on where you buy them. I've been lucky and found E20-4 and E30-4 for $18 for a pack of 2 and the F44-8's for $20 for a pack of 2. I feel there additional cost is worth it. Once you see one leave the pad in person you are hooked.
 
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