Mild to wild... Widest motor class rocket build

[Beanboy]

Thinking a low to mid power build to fly on A to F...

Any examples out their of designs of any size that handle a wide range of motor classes?

 

[mooffle]

Probably not what you are thinking of. Regardless it is an entertaining thread.
I'd find a decent size overstable 18mm rocketand mod it to have the engine mount removable/swappable. Maybe a big bertha or something similar

 

[dhbarr]

Blue Fin Tuba, G-M

Bluefin Tuba 3"

On the heels of original (38mm) BFT (http://www.rocketryforum.com/showthread.php?60951-Bluefin-Tuba), I'm building a larger version. BFT survived everything that could fit in the fuselage. I'm curious how much (and how little) motor I can throw at a larger version without breaking it. This...

www.rocketryforum.com

 

[Beanboy]

Yeah I almost posted about 38mm based rocket maybe being the widest range, 54mm didn't cross my mind. A very cool build, thanks for the link!

 

[boatgeek]

Oddrocs might be your friends here. You can pretty easily design a cluster spool with 7 x 18mm motors. It'll be light enough to fly on a central A but could take 7 x D. With the new D20 White Lightning Q-Jets, that would get you to 96.6 N-s, or 20% G total impulse. Of course, you have to *light* them all...

 

[CoAz2k]

A bit off topic. My 2.6" Madcow DX-3 with 29 mm motor has flown E through H. It could fly on a 29/360 I-200 with added weight up front.

Low power is an interesting idea.

 

[Beanboy]

Low power is an interesting idea.

Yeah something under three ounces with an A8 loaded that goes up on an F44 may be a neat challenge.

 

[jqavins]

I'd try a 29 mm motor mount, adapters for 24 and 18 mm engines, and swapable nose weights.

 

[boatgeek]

I'd try a 29 mm motor mount, adapters for 24 and 18 mm engines, and swapable nose weights.

In a more "normal" rocket [shakes fist at the clouds], you could easily stop at a 24mm motor mount and fly on the F30 and G65 White Longburn motors from CTI to keep from going too fast. If it's light enough to fly on an A8 it might have structural issues with a lot of nose weight. The TARC team I work with found that they tended to crinkle LPR body tubes after repeated flights on F power with just an egg in the front.

 

[mooffle]

Attached is the first rocket I ever built. Generally I fly it on A8-3's because I'm sentimental and can't shelve it or risk losing it.
Construction is a Paper towel tube within a couple mm of a BT-60, 4 Fins of whatever balsa I had lying around (probably 1/16th), and a nose cone turned on a lathe before I even knew how a lathe worked. (Dad helped along but I was 10)

Making no modifications other than the engine mount OR says I'm good to go! Right guys?

 

[boatgeek]

Attached is the first rocket I ever built. Generally I fly it on A8-3's because I'm sentimental and can't shelve it or risk losing it.
Construction is a Paper towel tube within a couple mm of a BT-60, 4 Fins of whatever balsa I had lying around (probably 1/16th), and a nose cone turned on a lathe before I even knew how a lathe worked. (Dad helped along but I was 10)

Making no modifications other than the engine mount OR says I'm good to go! Right guys?

70G off the pad and 0.7 calibers of stability is a bit ... sporty. Mach 0.7 might be OK, but you're definitely going to want to paper the balsa. Maybe the nose weight is a good idea.

 

[mooffle]

70G off the pad and 0.7 calibers of stability is a bit ... sporty. Mach 0.7 might be OK, but you're definitely going to want to paper the balsa. Maybe the nose weight is a good idea.

Does the screw eye count? It's big-ish and not in the sim. Oh and don't forget the parachute is nylon, not thin estes plastic.

 

[jqavins]

Well, I figure it this way. Let's say you start with old reliable Big Bertha, like mooffle said; good choice. It flies fine on an A8. Any F motor is a bunch heavier, so the CG moves aft, so you need to add nose weight.

It's a decently tall rocket, so maybe you don't need much weight. Maybe an A8 can still lift it. But with the CG moved so far up to the front now, and the A8 not lifting it really fast, it'll weathercock in a breeze that barely rustles the leaves.

To me that means exchaneable nose weights are inescapable.

If LP tubes buckling between the F motor and the nose weight is the problem, use the lightest stronger tube you can find. Thick walled paper? Blue Tube? Regular BT-60 with single layer of the lightest FG you can get? Something like that.

And if that's not the only way, it sounds to me like one viable way.

 

[Neutron95]

I'll run some sims when I get home, but something similar to the Apogee Aspire might be able to do A-H with the release of the H13.

 

[Beanboy]

I've got an old Aspire around somewhere, did send it up on a G25 10+ years ago and got it back sans nose cone. That H13... May just be the motor that motivates me to finally get certified, ha.

As far as nose weight goes, is sticking on a 2nd stage and use just one motor that runs through it versus having to adjust nose weight cheating?

 

[jqavins]

This is the first I've heard of the H13. WOW!

So, the original question was about A through F. As awesome as the H13 appears to be, it weighs 203 grams. Continuing with Big Bertha as an example (and yes, I know, it's just one example and not necessarily the best one) the estimated weight for the model is 71 grams, and an Estes C6 weighs 24 grams, so the H13 by itself outweighs the BB/C6 combination by about 2.1:1.

It'd be one thing to put a 29 mm mount into a stronger BT-60 size tube and fly everything from A to F. It'd be another again to shove a 203 gram motor in the back and keep the rocket stable.

Maybe a taller rocket would help. Super rocs have their own problems, of course, but maybe double the length of BB. Then one would need only something in the ballpark of half the nose weight to balance out the motor weight. That doesn't fix the issue of weathercocking on the A engine, but it may make some things easier.

OK, now to get off my nose weight soap box and onto the Aspire band wagon. That one doesn't weigh a whole lot; it's advertised to fly well on the low thrust F10. So how does it do on an A8? If the A8 actually had 8 N average thrust and peak thrust to match then it'd probably do OK (unless it needs too much tail weight to keep from weathercocking) but unfortunately the designation is a lie; the thing only has 4 N average thrust and the peak is less than 10.

The desired target of A through F may be harder than B though H, and is certainly harder than C through H, specifically C5 through H13. But the goal is the goal, and harder is more fun (in this situation).

(The B6 has more average thrust and peak thrust than the A8. And the 13 mm A10 has even lower average thrust yet. These designations have a defined meaning, and I'm sorry but the "A8" is really an A4. The "B6" is really a baby C5, but at least that's close. The "C6" is really a C5, and the "C5" is really a C4. Since the "B6" and "C6" are correctly two different C5s, I guess calling the baby C a B5 isn't such a crime. Really, all of them are somewhat close to correct except the A engines. But I digress. Frequently.)

 

[mooffle]

As far as nose weight goes, is sticking on a 2nd stage and use just one motor that runs through it versus having to adjust nose weight cheating?

I was going to suggest just leaving a nice big payload bay, fly empty on the bottom of the spectrum then add a camera or science experiment toward the top. However, your suggestion sounds more fun to change up the look of the rocket. Not sure about cheating, isn't this what the real space agencies do with payloads and boosters? See Delta and R-7:

 

[Neutron95]

I made some very rough sims for something similar to the Aspire. The A10 is enough motor to fly it safely, and it doesn't go too fast on the H13. I think that's cool enough that I might build one some day.