Never thought much about model rocketry before, but this sure piqued my interest!

I play with those things for a few years back in the 80's. A coupl e of simple D size engine mounts in the back end of an F20 is not a difficult thing. Only problem with this is that secondary bast going th opposite way to deply chutes. Any way to deal withthat???

Darn I had the reply all typed out, then I spazzed and hit some wrong key combo and blew it away.. sigh.

Yes, you need to deavticate the ejction charge or not have one to begin with and there are several options; 1. 2. and 3. are dedicated to Estes D11/D12 or E9 motors. The internal construction fo the motors, from the nozzle forward, is: Propellant grain, delay grain, and ejection charge which is granular. The ejection charge is retained by a loosely pressed clay cap.

1. Buy D11-P motors if you can find them. They are intended for RC rocket gliders, and have no delay or ejection charge. The top is is sealed off with a hard clay cap.

2. Buy D12-0 booster motors. Pour a cap of 30 minute epoxy in the top of the motor, directly onto the exposed propellant face (black) and let it cure. 3/16" is plenty. You can pad out the epoxy with some filler or microballoons if you have it. The motor will shut off at propellant burnout and nothing else will happen.

3. With any motor with a delay and ejection charge, i.e. D12-3, D12-5, D12-7, E9-4, E9-6, E9-8.. carefully scrape away the top soft clay cap and the loose black powder (ejection charge) until you get to the hard top surface of the delay grain which is a gray color. Then pour in a thin cap of epoxy. You don't need as much as for option 1., because in option 1 you are containing the motor chamber pressure with the epoxy. Here you are not. BTW you can flush the scraped out debris down the toilet, it won't hurt septic or sewage systems at all.

Option 3 is better in my opinion, especially if you buy the longest delay you can find (D12-7 or E9-8) because the delay will give you a smoke trail for that many (7 or 8 respectively) seconds after motor burnout, which adds to the smoke and fire effect you're looking for.

If you use composite single use motors, for example Aerotech E15's you can do 3. above more easily - simply peel out the paper cap that retains the black powder ejection charge, and tap it all out. Done. Don't worry about the small exposed surface of delay charge you see on these, it will not cause any problem like leaving in the ejection charge on Estes motors will.

If any of this doesn't make sense I can conjure up a graphic of the three options.

MJD

A LOT of model/high power rocketry is simply what we call 3FT flying, which stand for three fins and a tube, and that gets boring really fast. Another common and disparaging phrase is "whoosh - pop" as in the audio effect of repeatedly launching the aforementioned 3FT rockets. But do something interesting or unique and it is a neat hobby. As a big fan of HLG and free fllight in general, I can tell you that boost gliders are a real hoot, whether or not they are RC or free flight. They require the construction and trimming skills of hand launch gliders, the strength to withstand boost velocities, and to fly straight during boost. I really dig building and flying those. Really big, loud and fast motors (like above) are pretty *****in' too. The motor above is loud enough to deafen you up close. The photos above are taken from 1000' away which is much easier on the ears, but still pretty impressive.

MJD

I remember that article for the twin motor delta with independant ignitions. I was suprised to see AMA Model Aviation posting that article but it is ok within their guidelines. Was tempted to build it.

I had built a "D" powered rocket glider many years back that had its debut at the World Famous Rabbit Dry Lake. It was basically a very lightly built glider I later flew on the slope in light lift days, but I found the "D" motor a bit anemic for me. It launched from a ramp and climbed at a 45* angle to a not so high altitude and the motor ejected itself (by design) out the back to loose unwanted ballast. It was a fun challenge but the plane was more fun on the slope. If I did it all over, I'd crank it up to an "E" and build lighter....

FAI competition RC rocket gliders (S8E) are pretty amazing performers. On a long burn composite E motor they can get up to about 1000' altitude. They are pretty much like 2 channel polyhedral 0.8 - 1.0m span RCHLG's in performance, because that's pretty much what they are. With the low cost flight gear available, one can easily build a sport D12 or E9 boosted glider that can get to several hundred feet altitude and soar well. If you're interested in RC rocket gliders, you might want to take a look at the line of reloadable motors Aerotech offers for these types of models - they have 24mm D and E and 32mm F and G reloadable systems specifically designed for RC rocket gliders. These can get you some serious performance.

I am not sure how he light off the Estes rockets, but I did it by using a extra servo and channel. just made a simple on/off switch with the servo arm to make the connection for the battery/fuse circuit. I used the throttle channel and when I wanted to light off the rocket I just moved the throtle to full and when the servo arem moved forward it made contact with the other end of the wire. The battery I used was the 4.8v receiver battery.

I guess you could also use a landing gear channel for the same thing.

Larry

RC ROCKET???????!!!!!!!! Yeah baby, now I am really interested! Oh great, something else I can't afford to do!

Been doing all kinds of boost gliders (mostly small) for a while and MJD is right they are the most fun. Here is a pic of 41.5's rocket car. He was 6 when he designed and built it.
We launched it this past Sunday with two Bs and one C and then two Cs. Too much fun for one neighborhood.[sm=shades_smile.gif]
If I could get past the pain I would post the vids.[&:]

I fully agree that you need to get rid of the delay ejection charge. It was difficult to find the 11 - P engines so I went with the 12 - 0. My first flight with my FIRST ladyhawk was a launch, reach apogee, try to control craft and crash. SInce I thought that the -0 ment NO ejection pulse, Was I wrong. The first motor burned out, then the '0' ejection pulse caused the second motor to ignite from the top down. When I got to the Ladyhawk, it was smoking, and all my radio and servo gear was burnt to a crisp.

I cut off the wings and built a new body for the glider and gave the chared remains to the local hobby store to display what a rocket motor can do the plastic receiver and servo's. Got lot's of looks and gee wizz what happened.

My later flights were with epoxied tops on the motors.

Larry

No, what I'm suggesting is that someone with too much money to spare decides that it might be cool to bolt a 18000Ns "commercial" motor to his Patriot, and then tries to make a low pass to "impress" the other folks...

A sugar engine may be low key to you, but it can be a lot of fun to other people.

If you realize that "your elevator linkage may come loose", you need to pay more attention to what you're flying. Linkages don't just "come loose"... If they do, you're doing something wrong. I've seen a couple of those at the field... whenever they show up, I make a run for the fence...

It's too easyto get the "run of the mill". We go to the field and see our same buddies (which is good) but the same old thing. Helping a guy out with his huge H9 Ultimate is nice but I'm use to it. Then see families come out and see a plane like this is impressive. I would like to see my F-20 coming across the field and then kick in a couple rocket engines blasting out the back.

Then just while your friends are getting used to your rocket assisted model you activate the scramjet.

I think these models probably should not be flown at the normal flying field and would be best taken out into the desert, but with a little imagination we should be able to push the RC horizontal flight record a little higher and take the current record away from the RC gliders who have held it for too long. Do they still hold it ?

I think part of the rules defining a model record is that it has to obey maximum weight limits.

What about r/c rocket cars?----ooohhhh puppy![X(]

I can send a vid of the car to anyone's email