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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?
 

tbzep

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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?
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.
 

tibadoe

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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?
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.
 

AKPilot

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The general rule of thumb is 2-3x the length of the rocket. Again, as a general rule.
 

gpoehlein

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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: http://www.youtube.com/watch?v=raLx8RCCpvs
 

Scode68

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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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qquake2k

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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: http://www.youtube.com/watch?v=raLx8RCCpvs
Was the Astron Ranger an early version of the Big Bertha?

Jim
 

gpoehlein

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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.
 

Gillard

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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.
 

sandman

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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
 

zog139

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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:
 

foose4string

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My Bertha shock cord is about this long:



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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Scode68

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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
 

qquake2k

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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.
Nice looking paint job. Do you have a photo of the whole rocket?
 

qquake2k

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Heres a before and after the stickers.
Very very nice! Big Bertha is such a classic rocket, and yet as you have demonstrated, the looks she can achieve are endless. Great job!
 

Peartree

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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.
 

Steward

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For extra excitement, I built a BB with the 24mm motor mount... it screams off of the pad...!!!


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.
 

sandman

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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.
 

zog139

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BTW, there is no prize for getting this.


You mean............ no Roachwerks Little Joe -2 kit up for grabs ? :y:
 

Neutron95

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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.
 

accooper

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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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