Just Curious--- Anyone do an Estes F15-0 to E (echo) 15-8 two stager?

[BABAR]

Was just messing around looking at propellant weights.

On thrustcurve.org the F to F combo looks a bit heavy to get off the launch rod. Could probably do F to E (found this out after my initial post)

Looks like this could be done without straying into High Power land. https://nar.org/hpcert/NARhprintro.html

This is for F to F, so F to E would be better.
Total impulse at 50 each for total of 100 stays under 160 Ns
Average thrust at 25 is easily under 80
Total propellant weight at 120 is just BARELY under 125
Could easily be built under 1,500 grams with motors (combined weight of just the two motors about 200)

cost for engines at $18 a pair would be about $18 per flight, plus tax and shipping. https://www.hobbylinc.com/f_model_rocket_engines

I'm guessing has already been done.
Would make an interesting minimum diameter rocket.

 

[BEC]

If the conditions allow I will try it this coming weekend - Estes Majestic and the PSII booster. Minimum diameter would need a nice big field......

 

[shreadvector]

Kit built as the isntructions say with the PSII booster used per the instructions works fine with F15-0 to F15-8. I prefer little wind and a six foot long steel launch rod.

You will not be able to use an E15-8 as there is no such motor.

You can indeed use an E16-8 in the upper stage as that motor exists.

 

[Rocketjunkie]

This is a 3 stage rack rocket - F15-0 to F15-0 to F15-8.
[YOUTUBE]c1pqYgG-TOg[/YOUTUBE]

 

[ThirstyBarbarian]

I haven't done much staging, and I have a question about the staging of two different motor classes like being described here. Is there any advantage to the order in which the two classes of motor are staged? Would it make more sense to go F to E, or E to F?

 

[BABAR]

Kit built as the isntructions say with the PSII booster used per the instructions works fine with F15-0 to F15-8. I prefer little wind and a six foot long steel launch rod.

You will not be able to use an E15-8 as there is no such motor.

You can indeed use an E16-8 in the upper stage as that motor exists.

I sit corrected. Thanx! LOL
I was trying to correct my initial post, as thrustcurve.org suggested that my original idea, F15-0 to F15-8 was going to be going a bit slow off a 2m rod.
Although reading the Post 4 by rocket Junkie, apparently thrustcurve.org may be a bit conservative!

 

[BABAR]

This is a 3 stage rack rocket - F15-0 to F15-0 to F15-8.
[YOUTUBE]c1pqYgG-TOg[/YOUTUBE]

How was the recovery? Any estimate on altitude? By propellant mass this would qualify as HPR.

 

[kouroshg]

I haven't done much staging, and I have a question about the staging of two different motor classes like being described here. Is there any advantage to the order in which the two classes of motor are staged? Would it make more sense to go F to E, or E to F?

I would use the bigger/more powerful motor in the booster stage and the smaller/lower power motor in the systainer. The reason being that you want more power to launch the heavier rocket and once it's moving, the sustainer is already going at a pretty good clip.

 

[shreadvector]

Actually, you want to carefully review the rocket at all points in the flight because if it is moving too slow at any point the results can be a weathercocking disaster.

Using an E16-0 booster will give you the exact same intiial thrust spike but you will have less time with the long sustaining and lower thrust before the upper stage ignites (with it's own thrust spike, but it takes some time to reach the peak thrust - look at the curves carefully). Dropping the weight of the booster stage and booster motor casing earlier can be an advantage to the upper stage. The optimum would be a booster motor with higher thrust than the sustainer to get it moving fast, but the motors are pretty much similar except for the F having a longer sustaining burn at the lower thrust level.

Run several simulations to see how it behaves in each combination.

THis is why the new mass marketed two-stagers use a D12-0 booster and an 18mm B6 or C6 sustainer. The D12-0 gets the medium weight combo moving pretty fast.

I would use the bigger/more powerful motor in the booster stage and the smaller/lower power motor in the systainer. The reason being that you want more power to launch the heavier rocket and once it's moving, the sustainer is already going at a pretty good clip.

 

[kelltym88]

Hmmmm, interesting that this subject should come up.......

I recently won an Estes Magnum kit off of ebay and looking at it I thought that it would be interesting to put an "F" booster on it. So I made my own "F" booster and made the upper stage 24mm. My only challenge now is getting the CG to balance after the initial boost. Those "F" booster motors are heavy. I have dry fitted weight in the payload section, which works for the initial boost, but after staging it would surely veer off, so I may have to put it in the nose. Or make it longer, but I want to be able to use at as ""D" to "D" as well.

Slightly off topic, but kind of the same........

 

[Rocketjunkie]

How was the recovery? Any estimate on altitude? By propellant mass this would qualify as HPR.

Recovery on a 3" x 80" gold ribbon streamer was fine. Saw it land but didn't go get it. It only costs about $5 to build and contains $30 of motors. Fire & forget , just build another. Flown at a HPR launch with waiver. The rack gets pretty charred from the upper motors. Might survive a second flight but no more.