Estes - Big Bertha {Kit} (1948, 23, 7007)

Contributed by Bill Eichelberger

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Diameter: 1.64 inches
Length: 24.00 inches
Manufacturer: Estes
Skill Level: 1
Style: Sport
Rocket Pic

Brief:
Everybody's favorite prom date, the Estes Big Bertha, is a rocket that seems to wind up in every fleet at one time or another. While there are a lot of other rockets in her size range that equal her low, slow, and always stable flights, there's something to be said for building and flying the original. Bertha's getting a little long in the tooth these days and in need of an update, but it's nothing that a quick shot of Kevlar couldn't fix.

Construction:
The kit contains:

  • BT-60 main body tube
  • BT-20B engine tube
  • PNC-60L nose cone
  • 2 RA-2060 centering rings
  • engine hook
  • elastic shock cord
  • balsa fin stock
  • 18" parachute

The Bertha instructions remain the standard by which other skill level one kits are written. (I'd prefer that the part numbers were still included as a part of the exploded view, but that's a personal nit that I felt the need to pick.) The Bertha has no "gotchas" and is the perfect starter rocket for those with a taste for small field flying. I attached the engine mount with Elmer's Wood Glue and for the first time in a long time, glued in a stock Estes shock cord with a tri-fold paper mount. Normally I would use about six feet of combined Kevlar® and sewing elastic, but I wanted this comparison to be about stock models built the way the instructions said. So for the sake of the comparison, I went retro.

My fin attachment method did have a nod to the new millennium. I tacked the fins in place using LocTite Gel CA, then filleted them in place with two heavy lines of wood glue per joint.

Finishing:
Although the Big Bertha paint scheme I modeled was the 1969 catalog version, the finishing remained the same. Before anything was done I coated the spirals with thinned Elmer's Fill 'n' Finish, then sanded the whole thing smooth. The fins, which were shaped as was directed in the instructions, were then given two coats of the same Fill 'n' Finish with sanding between each coat. The rocket was given a base coat of white, then masked to allow the 1969 catalog scheme to come to life in black and red paint. I used Valspar paints throughout the project with the final touch being an Estes logo decal that JimZ sent me with an order back in 2001. Why go to this much trouble? Because the current Bertha paint and decal scheme is DULL! If ever there was a rocket ripe for updating, the Big Bertha is it.

Construction Rating: 4 out of 5

Flight:
While this wasn't my first Big Bertha, I wanted to fly the same progression of motors that I flew in the other three rockets in this comparison: a B4-2, B6-4, and C6-5. All three flights were made on a windy day which I knew from experience would make for some long recovery walks, so I started with the C6-5 flights while my legs were fresh. The Bertha on the C6-5 climbed to a pretty respectable height, then drifted downrange 1/4 of a mile or so. The stretch of field we flew on that day has exactly one rocket eating tree on it, and for a moment it looked as if the Bertha might land in it, but a fortuitous gust carried it past the tree and to the left. I was able to cheat a little and do most of my walking on the access road, which cut down my time between flights and made my legs feel less like lead from stomping through the weeds.

The B6-4, while noticeably lower than the C6-5 flight, would still allow you decent small field flights with very little fear of losing the rocket to a tree. The Bertha recovered about 100 yards from the pad and I was back prepping for the third flight very quickly. Flight #3 was on a B4-2, which was suggested to me as a way to get a good liftoff picture. I still managed to get the rocket smoking on the rod, but the flight was interesting in that it took a moment for the rocket to find it's way after clearing the rod. It looked as if it stopped for a moment before kinking noticeably to the right as the wind caught the big fins. Recovery on the B4-2 flight was just past the pad, but windcocking was pretty severe. (Not always a bad thing.)

Recovery:
Recovery was handled by the stock 18" Estes chute, heavily reefed to cut down on the aforementioned recovery walk. That didn't matter though. I walked myself to death anyway. This hobby needs caddies.

Flight Rating: 4 out of 5

Summary:
PROs: Classic styling, variety of catalog paint schemes to choose from, and foolproof design and instructions.

CONs: Not enough shock cord! And would it kill Estes to come into the 21st century and start including Kevlar® as part of the recovery system?

Overall Rating: 4 out of 5

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    (by Paul Gray)  Background The Big Bertha is a classic rocket built and flown by thousands of people around the world since 1965. Its was designed to have a rather impressive size and to develop the skills of people who are advancing themselves further in the hobby of model rocketry. Because of its size and performance, it is a great rocket to fly on a football field on C motors, ...

Flights

Comments:

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K.R.J. (November 1, 2000)
The Big Bertha was the first "big" rocket I ever built. I got one when I was 12 and in the hospital. The nurses all thought I was crazy for building a model rocket in a hospital bed, but it went together well. ( I didn't paint it there, though!) Years later, after moving to Europe, my friend Ernst bought me one for Christmas. He couldn't believe that I had one as a kid! This is absolutely the best kit Estes (or Robbe GmbH) ever put out. Period. [As far as the review] Exactly the same experiences. Had to chase mine a half mile once because of the large parachute.
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J.W.P. (January 1, 2001)
Big Bertha is the favorite in our fleet. We have never had a bad launch. Specifically, the large tube size let the chute pack loosely and it opens well. Also, this model tends to weathercock. This means it tends to angle into the wind on its own. The harder it blows the more it flies into the wind and is more likely to land back in the launch field.
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D.T.H. (January 1, 2001)
This kit is quick and easy to assemble. I have been flying my kit for about 6 years. It takes a lot of abuse and keeps on flying. A great first kit for kids. I always take it with me to fly.
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P.D.M. (May 1, 2001)
This is a great, classic rocket with good size (for an Estes kit). I built it with a 24mm (D&E-size)engine mount and I added epoxied BBs in the nose to offset the additional weight. I also replaced the cheap Estes chute with a Rogue 18" nylon chute with a spill hole cut out. I then painted mine a combination of black and turquoise to set it apart from the rest of my rockets. I first launched it with a D12 and it flew great! Straight and high. Then I tried an Aerotech E15 and it was spectacular! My last flight of the day was with another E15 and another great flight, but the winds took it almost out of sight and an hours search was fruitless... it was gone. A great kit and I highly recommend the 24mm engine mount, but get ready to get on your horse for recovery.
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D.P. (July 1, 2001)
My Big Bertha has flown 32 times on everything from an A8-3(low flight)to a D21-4T(great flight) as of 6/27. It now has very thick epoxy fillets on the fins because of them coming off and gluing them back on. I switched out the 18" chute after 28 flights because of excessive drift for a 14" one. The review was right on. The reviewer did not think the drift was bad, but it became a problem for me. Otherwise, I would rate the Big Bertha at a 4.5 out of 5.
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D.H. (October 2, 2001)
I've had my Big Bertha for just under a year now and have launched it probably twenty times. Visually, I don't find it all that impressive, but it sure is reliable. In fact, just the other day, I had to launch it with no recovery system at all. I had forgotten that I removed the parachute, but it flew great. Four great flights and only one tiny tear in the body tube.(fixed on site of course!). I always launch the Bertha first on launch day, to test the winds, because I know I will get it back. Long Live Bertha!
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M.B.H (October 11, 2001)
The Big Bertha is probably my favorite rocket. It's robust, reliable, and has great flights. I launched it one day four times, compared to one or two for my Rattle-7. I flew it on an A8-3, for a low, short flight, B4, B6, and a C6 drag race with another Bertha on an Aerotech RMS D. A sweet rocket that I personally do not think I could ever do without again, now to get a couple more to add to my inventory...
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M.C.L (December 26, 2001)
I flew a 1969 model that was the original and had been stored in a box in a garage for 30 years. It has the balsa nose cone and fins. The things to look out for when building this model are the fins. If you use balsa (I recommend retrofitting the newer Estes model with balsa fins), glue them on with Epoxy. I also used epoxy on the motor mount and the shock cord mount. It ended up as an all-epoxy model. The added weight did not affect the C.G appreciably. I added a heavy duty snap swivel and 1/4" elastic shock cord from a fabric store. I sealed the nose cone and fins with Elmers fill-n-finish and sanded each with 400-grit for a perfect finish. I finished mine with OSH spray paint in purple, red and yellow. I made a custom decal (since the original model had no decals, unlike today) for mine. I did the design in color using Adobe Photoshop. I then printed that at Kinko's on their color laser printer but I had them print it on what they called "sticky back" which is a clear, adhesive-backed film. I cut out the design (leaving a 1/8" margin) and stuck that to my model. Final cost? About 2 bucks. Looks awesome. The model is then clear-coated for a mirror finish. I modified this big Bertha with a homemade 24" ripstop nylon X-form parachute. It is heavier than the Estes plastic one that comes with the model but it is built like a tank (to match the rocket). Estes hit a home run with this model. It has flown countless times and has never given a bad performance. It flies straight and true and recovers perfectly each time. I fly it on C6-5's due to the extra weight and it performs flawlessly. This is a great model for an intermediate beginner and will never cease to impress your friends. I recommend not using the black paint job and, instead, coming up with your own design for this odd-looking bird. The crowds love it and it will fly and fly again.
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B.A. (March 24, 2002)
I luv my Big Bertha. The only troubles I've had is that after about 10 flights the engine mount began to come loose. I think I'll use it as an experiment platform. I love how it goes up nice and straight and has a graceful landing.
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J.R. (July 30, 2002)
My only quam with building this rocket came from the motor mounts and the shock cord system. For the motor mount before it's installed make eight small balsa triangles (gussets) with the scrap balsa that is leftover from the fins. Make them small enough so you can glue them every 90 degrees around the forward mount (these would be in the aft position) and the rear motor mount (these would be placed forward of the aft rings). Also replace the shock cord with a Kevlar® cord that could wrap around engine and threaded through the forward ring then attach sewing elastic (found in fabric stores) just after the Kevlar® cord exits the body tube. I used Fill n Sand for sealing the fins and used a wet finger to make real smooth fillets which I then sanded with 220 then 400 grit for a nice finish. Primer, sand ,primer, sand (600grit) tack cloth then paint two coats of color followed by three coats of clear...AWESOME!
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D.W. (April 5, 2003)
You just need to look at the amount of entries in the flight logs for this rocket, and count the number of times words like 'perfect' and 'great' are used to show what a class rocket the Big Bertha is. Its not the highest flyer; but the slow, realistic take off, and the lovely slow arcs to apogee makes up for that!

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