Big Bertha Clone

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Scode68

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I just built a Big Bertha using stuff that I had for a while but don't know how long the shock cord should be. Everything say SC-1 and all I can make from this is 1/8" wide. How long should the cord be?
 
I just built a Big Bertha using stuff that I had for a while but don't know how long the shock cord should be. Everything say SC-1 and all I can make from this is 1/8" wide. How long should the cord be?

The longer the better. :)

Are you using elastic or kevlar?

Everybody has their formulas, but I like to use a good 4 feet if the rocket is big enough to fit it all in there.
 
I just built a Big Bertha using stuff that I had for a while but don't know how long the shock cord should be. Everything say SC-1 and all I can make from this is 1/8" wide. How long should the cord be?

Nice build and paint.

Just looked at my kit and its about 2 ft long. When I replace it or build another I will go at least 3 ft.
 
The general rule of thumb is 2-3x the length of the rocket. Again, as a general rule.
 
Nice job - the Bertha is a great flyer - you'll have a lot of fun with it.

Go to your local sewing supply store (or craft center if they sell sewing supplies) and grab a couple of packs of both 1/4 and 1/8 inch flat elastic cord - you'll have enough material for quite a few rockets. As for length, AK is right - 2 to 3 times the length of the rocket should be about right.

One other suggestion - Download the instructions for the Astron Ranger from Jimz - it is a cluster version of the Bertha with a payload section. Really fun - I just flew mine this past weekend on three Quest A6-4 motors - it was a fantastic flight (I even heard the three ejection charges go off "pop-pop-pop" :D It's the second flight on in this video: https://www.youtube.com/watch?v=raLx8RCCpvs
 
Thanks,

I'm a "BAR" and have been out of the hobby for 25 years so I have been trying to catch up on new materials and techniques. The rocket on the right was the last kit I purchased back in 84-85, it's an Estes Hecules.

I have an Estes build kit so there ar a few different lengths in there. Kind of figured to go elastic all the way on this since it is a little late to go Kevlar.

Next time I'm in Wall mart I plan on getting some elastic from their fabric section.
 
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One other suggestion - Download the instructions for the Astron Ranger from Jimz - it is a cluster version of the Bertha with a payload section. Really fun - I just flew mine this past weekend on three Quest A6-4 motors - it was a fantastic flight (I even heard the three ejection charges go off "pop-pop-pop" :D It's the second flight on in this video: https://www.youtube.com/watch?v=raLx8RCCpvs

Was the Astron Ranger an early version of the Big Bertha?

Jim
 
Was the Astron Ranger an early version of the Big Bertha?

Jim

Sort of. The Ranger (released in 1962) was a three motor cluster with a payload section. The total length of the sustainer plus payload tube ended up being 18". In 1965, Estes took the fins and nose cone, along with an 18" tube, put a single 18mm motor mount in it and called it the Big Bertha. I don't know the exact details of the genesis of it.

The Bertha launches nice and slow on a single B or C motor. The Ranger, with no payload holding it back, screams off the pad like a bat outa h***. And the conversion is so simple, everyone oughta give it a try and add one to their fleet. I am really glad I did - it is always a crowd pleaser when it launches.
 
Sort of. The Ranger (released in 1962) was a three motor cluster with a payload section. The total length of the sustainer plus payload tube ended up being 18". In 1965, Estes took the fins and nose cone, along with an 18" tube, put a single 18mm motor mount in it and called it the Big Bertha. I don't know the exact details of the genesis of it.

The Bertha launches nice and slow on a single B or C motor. The Ranger, with no payload holding it back, screams off the pad like a bat outa h***. And the conversion is so simple, everyone oughta give it a try and add one to their fleet. I am really glad I did - it is always a crowd pleaser when it launches.

Just had a look at the ranger instructions on Jimz site, i think i'm going to have to build it. Liked the way back then that motor mounts were called engine holder tubes, couplers were called nose blocks etc.
 
Was the Astron Ranger an early version of the Big Bertha?

Jim

Vern Estes came up with the Big Bertha during a Cub Scout meeting/build session a way long time ago based on the Astron Ranger. Vern told me this.:D

Here's his original at NARAM 51.

Who can identify everyone in the pic?;)

Vern at NARAM 51.JPG
 
Vern Estes came up with the Big Bertha during a Cub Scout meeting/build session a way long time ago based on the Astron Ranger. Vern told me this.:D

Here's his original at NARAM 51.

Who can identify everyone in the pic?;)

I can except the young man doing check-in ?

:confused:
 
My Bertha shock cord is about this long:

Bertha-under-chute.jpg


Mine is a clone too, BTW. I'm in the camp that believes the longer, the better (if space allows). You could use 1/8" wide, but there is plenty of room for 1/4", which is what I have in mine. 1/4 inch will hold up longer.
 
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The Ranger sounds like a winner and I'll have to build one of those also.

My daughter wanted the Bertha I built so I will be working on a Ranger for me. We added some star stickers and 3-4 coats of Future on her.

Rocket 003.jpg
 
The Ranger sounds like a winner and I'll have to build one of those also.

My daughter wanted the Bertha I built so I will be working on a Ranger for me. We added some star stickers and 3-4 coats of Future on her.

Nice looking paint job. Do you have a photo of the whole rocket?
 
Vern Estes came up with the Big Bertha during a Cub Scout meeting/build session a way long time ago based on the Astron Ranger. Vern told me this.:D

Here's his original at NARAM 51.

Who can identify everyone in the pic?;)

And my son is holding the rocket just to the left of Vern. The rocket he's holding is a Semroc IRIS.
 
For extra excitement, I built a BB with the 24mm motor mount... it screams off of the pad...!!!

IMG_8363.jpg

Photo by George Gassaway

As to the shock cord legnth... I don't remember where I read (maybe Gassaway told me,) but I've always used 3 times the length of the body tube.
 
Me too - I get John, Carl, Vern and Gleda. And Peartree's son's nose cone.


BTW, there is no prize for getting this.:D

It just seemed like a cool picture to post in a Big Bertha thread.
 
BTW, there is no prize for getting this.


You mean............ no Roachwerks Little Joe -2 kit up for grabs ? :y:
 
At the DART launch this weekend there was a large upscaled Big Bertha. I think that was about six inch diameter tube and a 54 mm motor mount.
 
I have found that using a combo shock cord with twice the length of the rocket of heavy Kevlar cord and twice the length of the rocket of elastic of 1/8th or 1/4th width will do an excellent job with never a zipper.

Andrew
Dark Lord Of The Scratch Builders
 
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