Taking a shot at the G record

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techrat said:
I have many questions regarding this build. Why is a high-strength Carbon Fiber tube required when the motor is a G12? I would imagine the low-thrust, long burn motor would allow you to use a cardboard tube. In my mind, you could take a standard Estes "Star Orbiter" BT-60 kit, build it without the second tube so it's only half the length, and still fly pretty damn high on a G -- a low thrust G12 should not cause the tube to fail.

It seems to me that the Carbon Fiber requires heavier adhesives such as epoxy to keep the fins attached, when you could go cardboard and balsa, and keep the whole thing fairly light. Or am I not thinking this through?
Click to expand...

You're mostly right, and I have done several builds that way with a cardboard tube and airfoiled balsa fins for the F10. The carbon tube is 16.5 grams vs. 12 grams for cardboard. The advantages are that I can get a smooth finish without adding paint, I can get a more secure connection for the fins, which will be very thin (0.03-0.04") carbon fiber, and just overall durability.
 
techrat said:
In my mind, you could take a standard Estes "Star Orbiter" BT-60 kit, build it without the second tube so it's only half the length, and still fly pretty damn high on a G -- a low thrust G12 should not cause the tube to fail.
Click to expand...
G12ST-P is a 28.6mm motor. BT-60 is 41.6mm. If we assume Adrian's tube adds 1.5mm to the diameter of the motor (it could be less), the BT-60 will have 91% more frontal area. It would surely have a nice, high flight, but it's not what you'd want when gunning for a record.
Adrian A said:
Below shows everything tucked into the Apogee nosecone. The glued-in bulkhead is right near the front of the coupler.
Click to expand...
I'm very familiar with that nose cone. This is amazing. I could never have imagined you would get all of that to fit.
 
How fast are you expecting to go? If it's significantly subsonic, would an elliptical nosecone be more efficient?
 
NTP2 said:
From my understanding, the G12 is a long burn motor so it can’t push hard enough to go supersonic.
Click to expand...
That's more or less what I expected, though I'm also not sure if there is a 29mm elliptical nose cone on the market.
 
NTP2 said:
Idk if you can get one, but making one should be easy with a 3D printer.
Click to expand...
bad_idea said:
G12ST-P is a 28.6mm motor. BT-60 is 41.6mm. If we assume Adrian's tube adds 1.5mm to the diameter of the motor (it could be less), the BT-60 will have 91% more frontal area. It would surely have a nice, high flight, but it's not what you'd want when gunning for a record.

I'm very familiar with that nose cone. This is amazing. I could never have imagined you would get all of that to fit.
Click to expand...
If I were going with cardboard, I'd use the Apogee 29mm carboard tube. Likewise, the Apogee 29mm cone is the only light commercial 29mm cone I'm aware of.

The sim has the G12 flight going to about Mach 0.95. For the subsonic part, you just need something smooth, rounded, and near minimum surface area. The Apogee cone is fine for that because the size and shape are convenient for the tracker and altimeter I need to fit. But for transonic, it would be better if this were a Von Karman shape, and no commercial VK 29mm cones exist as far as I know. I have a polished aluminum VK plug and a worn out (destroyed) silicone mold from it, but laying up inside a mold like that is more of a headache than I want to take on. I actually bought a 3D printer this year, but I haven't had the chance yet to re-learn CAD and set it up. That's a project for this fall/winter.
 
Adrian A said:
If I were going with cardboard, I'd use the Apogee 29mm carboard tube. Likewise, the Apogee 29mm cone is the only light commercial 29mm cone I'm aware of.

The sim has the G12 flight going to about Mach 0.95. For the subsonic part, you just need something smooth, rounded, and near minimum surface area. The Apogee cone is fine for that because the size and shape are convenient for the tracker and altimeter I need to fit. But for transonic, it would be better if this were a Von Karman shape, and no commercial VK 29mm cones exist as far as I know. I have a polished aluminum VK plug and a worn out (destroyed) silicone mold from it, but laying up inside a mold like that is more of a headache than I want to take on. I actually bought a 3D printer this year, but I haven't had the chance yet to re-learn CAD and set it up. That's a project for this fall/winter.
Click to expand...
It's wild that the rocket is light enough that a G12 takes it so close to supersonic. Did you do any explicit modeling for fin flutter?
 
I haven't seen a weight for the Estes So Long nose, but presumably it would be heavier than the Apogee Aspire nose.
 
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boatgeek said:
It's wild that the rocket is light enough that a G12 takes it so close to supersonic. Did you do any explicit modeling for fin flutter?
Click to expand...
No, I looked into the existing techniques and they don't pass a sanity check for the effect of root chord , so it's trial and error for me.

Also, if I use a tailcone the G12 flights sim just over Mach 1.
 
Adrian A said:
No, I looked into the existing techniques and they don't pass a sanity check for the effect of root chord , so it's trial and error for me.

Also, if I use a tailcone the G12 flights sim just over Mach 1.
Click to expand...
Seems like a good application of giving it a hairy eyeball and saying "probably good enough."

As I tell the students in the high school rocketry club, engineering is the science of good enough. It's a line from my materials professor lo these many years ago.
 
boatgeek said:
Seems like a good application of giving it a hairy eyeball and saying "probably good enough."

As I tell the students in the high school rocketry club, engineering is the science of good enough. It's a line from my materials professor lo these many years ago.
Click to expand...
He sounds like a wise man.
 
Adrian A said:
I took some photos a couple of days ago that I haven't posted yet:

View attachment 608838
This one shows the tracker, tracker battery, and Blue Raven battery installed into the cone on the left, and on the right is the 29mm Blue Raven with the shock cord threaded through the tracker board and the Blue Raven's main deployment terminal. The other 2 terminals with the nuts attach the Blue Raven to the glued-in bulkhead and electrically connect the board to the Arm+ and Apogee channel deployment wires that are soldered onto the brass screws in the next photo, which shows the other side of the glued-in bulkhead:

View attachment 608839

My current plan for sealing this is to put a blob of vacuum sealing putty on the shock cord at a location that will provide enough room to pull the av-bay apart and then I'll tuck the slack in when I stick the coupler back into the nosecone.

Below shows everything tucked into the Apogee nosecone. The glued-in bulkhead is right near the front of the coupler.
View attachment 608840
Click to expand...
I love the LED in the nose.

It looks ready for a night launch :)

-- kjh
 
Adrian A said:
If I were going with cardboard, I'd use the Apogee 29mm carboard tube. Likewise, the Apogee 29mm cone is the only light commercial 29mm cone I'm aware of.
Click to expand...

AFAIK, Quest 30mm tubing is the same stuff as the Apogee 29mm light tubing. So the Quest 30mm NC should work as well.
 
I cut out the fins from some mostly-unidirectional CF fin stock that I made a long time ago. Once I sanded them flat they were 30 mils thick, about 1.1 grams each.

Tacked down onto the tube after a couple of alignment mistakes, the tube is 20.2 grams.

IMG-1916.jpg

With the fillets added and sanded, it's 21.2 grams.

IMG-1917.jpg

The fins feel a little bit floppy, so I'm going to go ahead and do a thin tip-to-tip layup with some thin uni fiber today.
 
kjhambrick said:
Thats a beautie, Adrian !

I believe you mentioned that the AF tube is 1.8 inch longer than the G12 ?

So your AF tube is about 8-inches / 203 mm long ?

Thanks !

-- kjh
Click to expand...
Yes, 8.25”

For the reinforcement layup I did a single layer of thin uni fibers that cover the fillet and go out to the fin tips, parallel to the trailing edge. The pieces are a little narrower than the fin chord so that I can sand it into a tapered cross section. Then peel ply, blue shop towel for a bleeder layer and then into a garbage bag hooked up to a vacuum pump. I have a space heater warming it up inside a cardboard box chimney now.
 
Adrian A said:
The fins feel a little bit floppy
Click to expand...
I’m happy to know I’m not the only one using ‘underly’ technical language to describe rocket parts.

I wondered how at 1.1 grams each they would hold up, so I’m glad to see they are getting some reinforcement. That’s the fine line between just strong enough, but not so much so that they steal altitude. It’s hard to know for sure when it’s the latter, but the former becomes obvious before too long.


Tony
 
After the reinforcement the tube is 22.2 grams, but the fins are significantly stiffer. 1 gram of carbon can go a long way. They’re still not totally rigid but they feel to me like they will be ok for a transonic flight.
IMG_1920.jpeg

IMG_1919.jpeg

Next I'll do just a little bit of sanding and then apply a layer of thickened epoxy over the whole thing for the surface finish.
 
After my thickened coat, oven-cured at 160F, the tube was 24.6 g. Then I sanded almost all of it off to get the final smooth shape with 100 grit sandpaper. The subtle long waves in the tube are finally gone. I did some wet sanding with 320 grit and and it's back down to 22.6. grams.

IMG_1924.jpeg

There are some fine scratches from the 100 grit sandpaper (just a cosmetic issue) and some exposed carbon, so now I have wiped on a very thin coat of epoxy from the last batch (still fluid since it was at low room temperature the whole time) on the tube and the nosecone and the tube is back in the oven.
 

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