Mild to wild... Widest motor class rocket build

[Steve Shannon]

A PML Pterodactyl was capable of being built to fly on all three high power levels (L1, L2, and L3). Granted it would take something with high average thrust in the L1 motors, but it could fly high enough to deploy a chute safely.

No, I didn’t try it, but when I selected the Pterodactyl as my L3 rocket I remember reading a web page that discussed it. I suspect most of the short fat rockets could be flown in the same way when built by someone with some experience.

 

[KenECoyote]

How about a properly sized carbon fiber version of something like a Wizard, Big Daddy or Alpha?

 

[boatgeek]

How about a properly sized carbon fiber version of something like a Wizard, Big Daddy or Alpha?

A Wizard is already nearly gone on a C. I'd hate to see what it did on an F, even upscaled to 24mm body tube!

 

[KenECoyote]

A Wizard is already nearly gone on a C. I'd hate to see what it did on an F, even upscaled to 24mm body tube!

"properly sized"

 

[dhbarr]

I don't think this is going to work. Any rocket LIGHT enough to fly on an BP "A" motor won't be STRONG enough to survive an F motor. My best suggestion would be a rocket with swappable motor mounts that can take an "A" cluster (Let's say at least 3 or 4 A motors), and can also take 29mm F's. That's the only way I see this working. You can make a rocket that'll fly on "A", but would likely be ripped apart by any high impulse composite motor. And any rocket build to survive F's just won't get off the pad under "A" impulse unless it's clustered.

This is simply not true. Minimum diameter, minimum length , minimum mass Apogee Aspire parts can easily take an F, which I have personally flown. I would have been pretty certain on several G's and maybe a few H's

 

[KenECoyote]

Saucer? As you put in a bigger & longer motor, the saucer itself becomes a rear funnel stabilizer.

 

[KenECoyote]

How about a properly sized carbon fiber version of something like a Wizard, Big Daddy or Alpha?

A Wizard is already nearly gone on a C. I'd hate to see what it did on an F, even upscaled to 24mm body tube!

"properly sized"

Actually I see your point...I was more in the vein of "let's see what I have that is cf and may be able to survive A-F" and I had some small cf rockets, but I wasn't paying attention to the point that it'd be going to la-la land (even though for E & F I'd put in a mini Eggfinder).

I may try the challenge given I have some cf supplies and I think something like Big Daddy, saucer or the other designs noted above may work. I can probably test A-D locally and then send to a friend with high skies for further testing if all goes well.

Just add that to my "wish to" build pile lol

 

[DigBaddy]

I've seen Baby Berthas with 29mm mounts....so that kind of crazy is possible Some smart fin reinforcement and adjustable nose weight, and it might be doable to handle a huge range of motors. I've even flown our stock Baby Bertha on a 1/2A (barely). Paper motor adapters may save a few grams over plastic. Baby Berthas can tumble recover just fine - or be ok on just a streamer for harder terrain.

 

[KenECoyote]

(Please forgive me if I've missed something mentioned earlier...jumping on this in-between work hehe )

The biggest challenge I see is that an Estes A8 motor's max liftoff weight is 3oz. and trying to build an under 3oz rocket that can take an F motor is quite a tall ask.

To me, the spirit of the challenge would be to ensure the rocket design and main components (bt, nose cone, fins) themselves don't change and that there is flexibility in recovery and tracking for the sake of safety, recording and recovery (which I believe all of us would agree is important).

So, after the lightweight design is settled on, for the A motor I would do just nose deploy with no recovery other than maybe a kevlar line connection. For the other extreme of an F motor, I'd add nose weight, gps tracking, altimeter and a LOOOONG streamer.

Sounds simple!

 

[jqavins]

Several of the comments above have mentioned changeable nose weight. But...

Also going to to aim for no changes to the rocket between motors; no nose cone weight changes or fin can tweaks.

So that solution is a non-starter in terms of the challenge as stated.

On the other hand, that's why I think it's darn near impossible as stated. If it's got enough nose weight to be stable with the mass of an F in the ass, then on an A it'll be too heavy to come off the rod with safe speed and/or radically overstable. Changeable nose weight just looks like a necessity to me. I know I've stated all that before, and also pointed out that a tall rocket might help, since it reduces the need for nose weight in the E and F engine cases. It also occurs to me now that a long launch rod would be a good idea, to give an A engine a fighting chance. But I still don't see this ending well.

I'll be grinning from ear to ear if I can be proven wrong.

 

[KenECoyote]

Several of the comments above have mentioned changeable nose weight. But...

So that solution is a non-starter in terms of the challenge as stated.

On the other hand, that's why I think it's darn near impossible as stated. If it's got enough nose weight to be stable with the mass of an F in the ass, then on an A it'll be too heavy to come off the rod with safe speed and/or radically overstable. Changeable nose weight just looks like a necessity to me. I know I've stated all that before, and also pointed out that a tall rocket might help, since it reduces the need for nose weight in the E and F engine cases. It also occurs to me now that a long launch rod would be a good idea, to give an A engine a fighting chance. But I still don't see this ending well.

I'll be grinning from ear to ear if I can be proven wrong.

Yeah, sounds like a Capstone project lol

 

[Beanboy]

It looks possible:

• Launch guide length: 48.0000 In.
• Velocity at launch guide departure: 52.0441 ft/s
• The launch guide was cleared at : 0.264 Seconds
• User specified minimum velocity for stable flight: 43.9993 ft/s
• Minimum velocity for stable flight reached at: 33.1070 In.

More worried about the coming back down part:

• Time to burnout: 0.731 Sec.
• Time to apogee: 3.270 Sec.
• Optimal ejection delay: 2.539 Sec.

Yes, overstable in the 7.x range. Also want to see published weight of Q-Jet F41.

 

[Beanboy]

And won't be a saucer; that would be too easy.

 

[rocketace]

My rocket "Zoom" can do a D to a J.
An old AT-D21 was the smallest up to a J825 & J570, Mach 2.2 & 16,000ft respectively. *D&E motors use a different nose cone* But I could see with some crafty work being able to do an E-K on a similar design without any changes.

 

[boatgeek]

Here's roughly what I would propose:
BT-80 tube with one of the rounded nose cones for minimum altitude under F power
Three trapezoidal fins, 1/8" balsa, papered for strength
A pretty small chute
A few more details to be dealt with (cut off the bottom of the nose cone to minimize weight, add in a shock cord weight, add rail buttons)
Launch off a 6' rail for maximum velocity off rail
A8-0 motor for the very low end.

I will grant that the A8 might not inflate the chute before it landed. The F44 shows a little bit of low stability, but this is also less than 10:1 so we could add in the base drag hack. I could see this being flyable. I might also look around for other F motors--the F44 wants a 6 second delay, squarely between the available 4 and 8. On the other hand, it keeps it a little lower too!

 

[lakeroadster]

Here's roughly what I would propose:
BT-80 tube with one of the rounded nose cones for minimum altitude under F power
Three trapezoidal fins, 1/8" balsa, papered for strength
A pretty small chute
A few more details to be dealt with (cut off the bottom of the nose cone to minimize weight, add in a shock cord weight, add rail buttons)
Launch off a 6' rail for maximum velocity off rail
A8-0 motor for the very low end.
View attachment 546270
I will grant that the A8 might not inflate the chute before it landed. The F44 shows a little bit of low stability, but this is also less than 10:1 so we could add in the base drag hack. I could see this being flyable. I might also look around for other F motors--the F44 wants a 6 second delay, squarely between the available 4 and 8. On the other hand, it keeps it a little lower too!

Off the rod speed looks sketchy on the A8... and a 17.7 feet apogee? I guess technically that's a flight.

 

[Flyfalcons]

I don't think this is going to work. Any rocket LIGHT enough to fly on an BP "A" motor won't be STRONG enough to survive an F motor. My best suggestion would be a rocket with swappable motor mounts that can take an "A" cluster (Let's say at least 3 or 4 A motors), and can also take 29mm F's. That's the only way I see this working. You can make a rocket that'll fly on "A", but would likely be ripped apart by any high impulse composite motor. And any rocket build to survive F's just won't get off the pad under "A" impulse unless it's clustered.

It's not that difficult, I built a 24mm minimum diameter cardboard rocket with papered balsa fins. Light enough for an A and had flown a couple times on an E20W. I attempted to launch it with an F44W but the motor blew on the pad. It would have survived no problem.

 

[DigBaddy]

Was looking at my fleet. Figured I'd sim a High Flier XL based on mine. This has a streamer for recovery. I switched the sim back to the unpapered fins. The fins have a lot of attachment length and may survive a F44 flight. No nose weight needed. 8' long rail though....

Could shave a bit of weight by clipping the fins and using a shorter coupler. Shortening the front tube a bit would drop weight and still maintain enough stability.

Looks like A8-3 to F44 may work just fine.

 

[boatgeek]

Off the rod speed looks sketchy on the A8... and a 17.7 feet apogee? I guess technically that's a flight.

Definitely a calm-day operation. I never said it was a LONG flight. It would be a crowd-pleaser though, with burnout at the top of the rail.

 

[Neutronium95]

A cardboard 29mm minimum diameter rocket should be capable of A through H, with carful motor selection. I suspect that with some strategic use of fiberglass, you could get it to survive a 29mm I motor, although it might end up too heavy for an A motor.

The only changes in configuration tht I'd make for different motor sizes would be whether or not a deployment altimeter and tracker are installed.

I believe that the way to maximize the motor range of a rocket is to build a lightweight minimum diameter rocket. You can use low thrust motors for the higher impulse classes in order to minimize aerodynamic forces, and it will still end up light enough to fly on significantly smller motors.

 

[dhbarr]

Several of the comments above have mentioned changeable nose weight. But...

So that solution is a non-starter in terms of the challenge as stated.

On the other hand, that's why I think it's darn near impossible as stated. If it's got enough nose weight to be stable with the mass of an F in the ass, then on an A it'll be too heavy to come off the rod with safe speed and/or radically overstable. Changeable nose weight just looks like a necessity to me. I know I've stated all that before, and also pointed out that a tall rocket might help, since it reduces the need for nose weight in the E and F engine cases. It also occurs to me now that a long launch rod would be a good idea, to give an A engine a fighting chance. But I still don't see this ending well.

I'll be grinning from ear to ear if I can be proven wrong.

Two words: Tube. Fin.

Three words: No. Nose. Weight.

 

[SolarYellow]

Another COTS option may be the Cherokee E with a 29mm MMT (it slips inside a BMS BT-55 coupler to work perfectly as a CR). Leave off the extra six-inch chunk of BT, just build it as 18-in airframe. Paper the fins. You'd have to adapt down to the smaller motors, but it is pretty light and simple. Should be big enough and have robust enough fins to live with the F44. That's not my favorite motor, though, as it wastes a lot of energy on velocity. Other options will get it higher, especially in a 24/40 reloadable case. Don't know about the full gamut of CTI 3-grain options without additional work.

 

[goose_in_co]

Pratt Hobbies used to make a Tomahawk kit that included adaptors for motors from A through G, the list was: 18mm: Estes A8-3, B6-4, C6-7, Aerotech RMS C6-7, D13-7, D24-10T, and E27-4T, 24mm: Estes D12-7, Aerotech E15-7, F24-10, Aerotech RMS D15-7T, E18-7, E28-7 and F12-5J, 29mm: Estes/NCR Dark Star F52-7, Aerotech Econojet G35-7, Aerotech RMS F22-5J, F40-10, F52-11, G33-7J and G64-10. It also had dimensions of the CP, so that if you wanted to use the larger motors, you could add the required nose weight to move the CG forward past the CP.
The rocket had plywood fins, and was solidly built, and could have been easily reinforced for the higher thrust motors. I flew mine on an A8-3, which barely ejected the streamer before it hit the ground, and the C6-5, barely made it to around 300 feet. I never tried a D, which should have been a better match for the kit.


The "Caution streamer" did not work well and it was replaced with either a parachute or nylon streamer that worked much better.

So I am certain with proper planning and interchangeable nose weight, you can make it work

Goose

 

[jqavins]

Yes, overstable in the 7.x range.

Definitely a calm day flyer. The kind of calm day one almost never sees, though not actually never.

Also want to see published weight of Q-Jet F41.

60.7 grams launch mass, 25.87 grams burnout mass, according to the certification document issued by TRA. 30 grams of propellant, so 30.7 grams at burnout, and the rest is probably mostly the delay grain with a little for the ejection charge and cap.

A pretty small chute

Small for sure, but why does it have to be pretty? A six gore chute with pictures of Karen Gillan, Jennifer Morrison, and Mary Tyler Moore across two gores each?

(OK, you wrote it correctly, without a comma, but I couldn't let that stop me.)

 

[lakeroadster]

Here's a BT-52H version with TARC Payloader style Basswood fins. I used my rear eject spool design and made the nose cone ballast adjustable.

Looks like a fun flyer.

​

 

[Beanboy]

Roughly what I have in the basement. Empty weight is ~1.8 ounces, which is accurate.

 

[jqavins]

What are the rod exit speeds? (That simulation results display is configurable to show various parameters, including that one.)

 

[Beanboy]

What are the rod exit speeds? (That simulation results display is configurable to show various parameters, including that one.)

A dozen or so posts up, it does look possible:

• Launch guide length: 48.0000 In.
• Velocity at launch guide departure: 52.0441 ft/s
• The launch guide was cleared at : 0.264 Seconds
• User specified minimum velocity for stable flight: 43.9993 ft/s
• Minimum velocity for stable flight reached at: 33.1070 In.

More worried about the coming back down part:

• Time to burnout: 0.731 Sec.
• Time to apogee: 3.270 Sec.
• Optimal ejection delay: 2.539 Sec.

 

[jqavins]

Sorry, didn't realize the newly posted design was the same as the one with those results.

Also, now that I've correctly connected posts 42 and 56, I see that the static margin with the F21 installed is ample (over three calibers, about 15% of rocket length) so if you've got any nose weight you could reduce it. That would help you with the A engine, both by reducing the overstability and increasing the rod exit speed.