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Super Big Bertha----What a Pain To Build!!!

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Flyfalcons

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This thread makes me want to do a SBB build video. I'm not even a fan of the standard Bertha, but the Super seems to drive the point of being big and slow home just a bit better.
 

DeepOvertone

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This thread makes me want to do a SBB build video. I'm not even a fan of the standard Bertha, but the Super seems to drive the point of being big and slow home just a bit better.
I loved the build and I love flying my SBB. After building mine, I went and bought a second kit to store away just in case I lost mine.. I love it that much.
 

PhlAsh

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I don't know why everyone gets so ate up about "flimsy cardboard centering rings". All they do is keep your internal fillets from running amok. Good filleting, internal and external, and it won't matter if the CRs are made out of wax, the fins transfer the load from the MMT to the sustainer. Now, if you were putting a J motor in it....
 

Sluggo

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I don't know why everyone gets so ate up about "flimsy cardboard centering rings". All they do is keep your internal fillets from running amok. Good filleting, internal and external, and it won't matter if the CRs are made out of wax, the fins transfer the load from the MMT to the sustainer. Now, if you were putting a J motor in it....
With all due respect why in many MPR are the centering rings 1/4" and the fins are 1/8th".??
 

Ron Humphrey

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I'm a beginner and SBB is my first "completed" rocket so I can only compare it to a Madcow Mozzie that I never finished. I did warp one of the fins when laminating them (had to make a 5th) and as others have mentioned, the walls of the body tube are thin, so slide a smaller tube inside when cutting the slots for the fins. As a beginner, I made my share of mistakes but had fun figuring things out. As I was waiting for glue/paint to dry I checked out "Rock Sim" and websites with thrust curves. I added an ejection baffle, rail buttons, and a nylon parachute.

This 36.8-inch rocket is designed to be big and light. I fly on cheap "D" motors from Hobby Lobby with a 24mm adapter. The 2.6" diameter SBB goes up nice and slow puts on a real show. Hard to find anything like this for a "D" motor. I think you will be happy with this rocket when you start flying.
(I'm eager to try the newly retooled and inexpensive black powder "E" motors that supposedly don't explode and then on to Der Red Big Max)
View attachment 451835
I used my dremmel to cut out the slots in the body tube. Went smooth.
 

DeepOvertone

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With all due respect why in many MPR are the centering rings 1/4" and the fins are 1/8th".??
Because of the orientation that the stress is applied to the pieces. Its like if you took a 2x4 and laid it out flat across two saw horses and pushed down in the middle, you'd be able to flex it quite a bit. But if you turned it on its side so the thickness is doubled, its much harder to get it to flex in the same way.
Yes, the fins may only be 1/8" thick but the stresses aren't pushing through the 1/8" direction, they are pushing through the 2 inches of fin tang direction.
 

Sluggo

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DigBaddy

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If anyone gets a SBB and decides they don't want to build it, I'll provide my address for uh, disposal...yeah, that's it.
 

dr wogz

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Many.?? I bet I could find 5 or more. The 3" LOC IRIS for starters. Let's focus on that 1 for now. Why is it designed that way. Or how about a Public Missiles rocket with G10 fins.??

Or go to this thread and check out post #119. Fins are gone but the motor tube and rings are still together.
Maybe the manuf. is willing to trade off the slight increase in cost & weight of the part, than the need to stock a separate / different part that is only slightly different (in thickness)..
  • The more of a particular part, the less it costs in teh long run
  • Easier to stock one part, than stock many similar parts (mistakes can be made when kitting) easier to manage inventory, less shelf space needed..
  • The thicker part assembles easier. A thin CR is more likely to be slanted on the MMT tube that a thicker one.

And, what thread are you referring to?
 

UhClem

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The Super Big Bertha seems to have changed. Mine has simple balsa fins (one broken already), no slots, and a 24mm motor mount.
 

Scott_650

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The Super Big Bertha seems to have changed. Mine has simple balsa fins (one broken already), no slots, and a 24mm motor mount.
The current #9719 SBB is part of the PSII line - 29mm mount, TTW built up fins, threaded engine retainer - so yes, a different version of the SBB than #2165 SBB.
 

kuririn

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I made a clone of the original SBB (the one with the fin gussets). Flew it on its' maiden with a 24 mm AT RMS motor. It CATOed and blew a hole in the airframe where the motor mount was. Salvaged the parts and built an upgraded SBB: Thick wall tube, plywood centering rings, TTW ply fins (kept the gussets), and 29mm motor mount.
Vinyl from Stickershock. Flew beautifully on its' maiden.
I guess I'll call it the Super Big Bertha HD. :D
0223211057[1].jpg
0223211058[1].jpg
 

Mike Haberer

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I'm no scientist so bare with me. Wouldn't adding length or adding the coupler towards the nose cause the rocket to weathercock more.??
The added length would, but the added weight forward provides some counter to the added length. The basic sims all ran fine.

I'm learning that over-stable designs are very sensitive to the angle of attack vs. the wind speed. It is very easy to overcompensate rod angle for perceived wind speed. Over stable designs really need real-time ground-level wind speed measurement combined with running a sim to find a safe angle of attack. Rocksim's wind speed ranges are fairly wide and don't account well for wind gusts. One degree of change in rod angle can make the difference between a stable flight and an unstable one. Rocksim Pro, whenever it comes out, promises improved wind adjustments in the simulation runs.

I'm designing a rocket specifically for the new AT G12ST (long burn) motor. Once you get to 3-7mph winds, a stable flight is VERY sensitive to minor design changes coupled with rod angle. Of course, you could wait for a day when there is no wind, but I've only experienced one of them in 55 years of flying....
 

tfrielin

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Thanks to everyone for this wide-ranging and interesting discussion.

To clarify my original position and point:

Compared to other Series II Estes kits, the Super Big Bertha compares unfarorably to other current Series II kits of which I've had recent experience and for two main reasons:

1) The fin build-up which I still maintain is not completely necessary, even though I comprehend the reasons given here for the 20 piece parts fin count. A pain. A needless pain, really.

2) The lack of a pre-slotted body tube.

Both these features---drawbacks---do not afflict the Doorknob, one of which I just built. Nor do either obtain with the Series II Nike Smoke--my next build (and my third NS). The former has solid balsa fins, the latter. nice plastic fins. And both have pre-slotted body tubes. I don't think pre-slotted tubes is too much to ask when you're paying over $30 for a kit.

Same for the Executioner--balsa fins and pre-slotted. of which I've build half a dozen. Even the smaller class 36 3D cluster (or whatever the correct name is) that isn't a fin-through-the-wall construction, but, nevertheless, has "extra" parts for integrity (like those plastic sleeves) is an easier build compared to Super Big Bertha. And results in a nice cluster rocket (too bad it's out of production.).

My overall disappintment with Bertha is its poor construction design, apparently due to cost control and import problems, as I understand from the comments here.

So, bottom line here is: If I splash either the Doorknob, the Nike Smoke, or the Super Big Bertha next time I fly, I would replace the first two. But not Bertha. It's just not a satisfying build for the extra steps.
 
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Mike Haberer

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I'm no scientist so bare with me. Wouldn't adding length or adding the coupler towards the nose cause the rocket to weathercock more.??
The added length would, but the added weight forward provides some counter to the added length. The basic sims all ran fine.

I'm learning that over-stable designs are very sensitive to the angle of attack vs. the wind speed. It is very easy to overcompensate rod angle for perceived wind speed. Over stable designs really need real-time ground-level wind speed measurement combined with running a sim to find a safe angle of attack. Rocksim's wind speed ranges are fairly wide and don't account well for wind gusts. One degree of change in rod angle can make the difference between a stable flight and an unstable one. Rocksim Pro, whenever it comes out, promises improved wind adjustments in the simulation runs.

I'm designing a rocket specifically for the new AT G12ST (long burn) motor. Once you get to 3-7mph winds, a stable flight is VERY sensitive to minor design changes coupled with rod angle. Of course, you could wait for a day when there is no wind, but I've only experienced one of them in 55 years of flying....
 

Sluggo

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The added length would, but the added weight forward provides some counter to the added length. The basic sims all ran fine.

I'm learning that over-stable designs are very sensitive to the angle of attack vs. the wind speed. It is very easy to overcompensate rod angle for perceived wind speed. Over stable designs really need real-time ground-level wind speed measurement combined with running a sim to find a safe angle of attack. Rocksim's wind speed ranges are fairly wide and don't account well for wind gusts. One degree of change in rod angle can make the difference between a stable flight and an unstable one. Rocksim Pro, whenever it comes out, promises improved wind adjustments in the simulation runs.

I'm designing a rocket specifically for the new AT G12ST (long burn) motor. Once you get to 3-7mph winds, a stable flight is VERY sensitive to minor design changes coupled with rod angle. Of course, you could wait for a day when there is no wind, but I've only experienced one of them in 55 years of flying....
Thanks for explaining that. I've got a lot to learn and this makes sense to me. The point of length and weight. Excellent. I hope your design works out for you. Question I've been thinking about lately and its on topic so......

Wind direction and rod angle...... Do you point the angle away from the wind direction knowing that the rocket will cock into the wind.?? Or do you point the rocket into the wind for a better angle of attack.?? Thanks.
 

neil_w

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Wind direction and rod angle...... Do you point the angle away from wind direction knowing that the rocket will cock into the wind.?? Or do you point the rocket into the wind for a better angle of attack.?? Thanks.
If you point it into the wind, it will weathercock more, *but* it will tend to land closer, since the flight will take it into the wind, and then recovery will come back in the other direction.

If you angle it with the wind a bit, then weathercocking will tend to straighten out the flight, and you can get a more perfectly vertical ascent. But then be prepared for a hike to recover.
 

Sluggo

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If you point it into the wind, it will weathercock more, *but* it will tend to land closer, since the flight will take it into the wind, and then recovery will come back in the other direction.

If you angle it with the wind a bit, then weathercocking will tend to straighten out the flight, and you can get a more perfectly vertical ascent. But then be prepared for a hike to recover.
Wow. Just a super reply Neil. Thanks a lot.!! I was just going to post a thread but I'll cheat and post it here......

I've flown my Estes Ventris twice. The first flight was on an F32-4 and was a super straight flight with decent altitude. The rocket came down close to the pad about 100 feet away. Stuck the landing on the 4 fins. I loved that flight.!! The 2nd flight with this rocket was on a G80-7. Winds were similar. I was expecting another straight as an arrow flight, and it was straight for like 1300ft. The rocket ended up going on a looong trajectory for like, ever. Nice smoke trail tracking the rocket. But I'm stuck trying to figure out why it went on that trajectory. It was the most impressive flight I've ever put up but I was somewhat disappointed in the trajectory. The rocket landed 1300 ft. from the pad. Should I have expected that.?? As opposed to a straight up flight and recovery.??
 

neil_w

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Could have been stronger winds higher up, other than that hard to say without having seen it.
 

PhlAsh

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With all due respect why in many MPR are the centering rings 1/4" and the fins are 1/8th".??
That's going the other route and using the CRs to transfer the load.
One or the other - or a balance of both
 

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