BBertha thread

The Rocketry Forum

Help Support The Rocketry Forum:

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
current project is a two stage big Bertha. though it would be a fast build...well it isn't. started with some left over bits from a baby b, needed a bt an engine hook and centering rings. ordered those and away I built. then ordered a Big Bertha for the sustainer, that is when the 'fun' began. the included c-rings were under sized (outer diameter), replaced those. check the fit of the nose, surprise it has an oversize dia. shoulder(note my previous bertha nose is also oversize in the shoulder), got that sanded down. replaced the launch lug w/ a 3/16" lug. am now debating color scheme. what do you all think of red & yellow? other idea would be white and red. thanks
Rex

bberthav1.jpg
 

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
well I figured that most everyone has built a bertha...I did however take a few shots. here are a couple of the booster. I did have to make a couple of changes from the stock B Bertha, the aft centering ring got moved forward 1/4"( and the mmt got moved forward 1/8") to allow for the interstage coupler, and the launch lug location got moved (because there was a booster fin in the way).
Rex

bbig2.jpg


bbig1.jpg
 

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
started doing decals, and found that the art department has struck again. if one puts the launch lug as per the instructions...then trying to get the aft ring(decal) to match the face card isn't possible. to the art dept. a hand of applause, (CL-) (CL-)*
*sound of one hand clapping
Rex
 

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
for the most part this build is done. waiting for the glue to dry on the motor mount, shortly after the tape was removed, and decals applied.
Rex

bbertha1.jpg


bbertha2.jpg


bbertha3.jpg
 

Nytrunner

Pop lugs, not drugs
TRF Supporter
Joined
Oct 15, 2016
Messages
7,943
Reaction score
3,625
Location
Huntsville AL
How much would it take to get you to fly it in that first configuration :cool:
 

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
it got its' maiden flight today on a pair of B6 motors, about as close to a textbook flight as one could wish for. by the time we glanced at the booster it had already landed (staging at 30' will do that :)), sustainer reached about 300'. glamor photo of it on the pad.
Rex

preflightbbig.jpg
 

TangoJuliet

Well-Known Member
Joined
Jun 26, 2016
Messages
1,239
Reaction score
9
Awesome! Makes me want to build another Big Bertha and add a booster myself! I already need to build another Baby Bertha after a C6-3 CATO last month.
 

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
I will note that the 'B' isn't flyable w/o the Big so if you want both you will need 2 babies :) also note dry weight came out to 135g...definitely not a blink and you'll miss it type launch :).
Rex
 

PhlAsh

Well-Known Member
Joined
May 9, 2011
Messages
987
Reaction score
68
Berthas.jpg

Little Bertha (BT-20) and Micro Bertha (BT-5). RocketMuse put in an Apogee order into which I added a nosecone - once that arrives, I'll start on a BT-50 based Mini Bertha.
 
Last edited:

Rex R

LV2
Joined
Apr 21, 2010
Messages
6,101
Reaction score
147
looking good. though the Estes mini brute version was bt20 (w/ mini engine power) based. just for giggles I tried doing up a three stage version in OR...it works in theory, methinks that I shall let someone else try building and flying it :).
Rex
note this version uses a D12-0 for the 1st stage.

BBBig.jpg
 

PhlAsh

Well-Known Member
Joined
May 9, 2011
Messages
987
Reaction score
68
I found the Estes Mini Bertha instructions on JimZ's site. The only difference between those and what I did seems to be the engine hook (I omitted) and the fin material (I used leftover cardstock from the UFO Invader scratchbuild). I decided that, in keeping with the Max tradition, I would reserve "Mini" for the BT-50 based version for which I am awaiting the nosecone.

Of course now this means I have to do a BT-20 based 'Little Max'!

A 3-stage Bertha would be a prime candidate for the Jolly Logic Chute release or a cord-cutter. I use double streamers on Double-D Bertha and fly it on a pair of D12s (or C11s if the wind is up)
DoubleD_Bertha.jpg

looking good. though the Estes mini brute version was bt20 (w/ mini engine power) based. just for giggles I tried doing up a three stage version in OR...it works in theory, methinks that I shall let someone else try building and flying it :).
Rex
note this version uses a D12-0 for the 1st stage.
 
Top