Big Bertha/Ranger fin pattern...
 

Hi all,

Are the fins the same size? Old catalog shows 3/32" for the Ranger. Plans show 1/8" for the 'Bertha. Have a fin pattern taken from a Big Bertha ~ 20 years ago - does not match the PDF files on screen. I don't have a printer... when held up to the screen, the pattern is quite a bit longer.

The reason I ask, parts are on the way from Semroc for both, have the pattern, just don't want to bolloks it up :-) Built a 3 cluster BB ~ 20 years ago, that was fun!

Bob

p.s. I'm a rebar, thanks to all!

As I understand it, Vern Estes created the Big Bertha by adapting the existing Astron Ranger design and changing the motor mount to use a single engine. He has said that he did this to create a model that had a slower liftoff, one that was easier to follow and that was more dramatic. So the Big Bertha is basically a single-engine version of the Ranger. Yes, the fin pattern is identical for both models.

You built a 3 cluster Big Bertha back in the day? Talk about bringing the design back around full circle! :D

Mark

Almost nothing is the correct size strait off the Internet. Just about everything has to be resized.

Bertha's progeny
 

By the way, the Astron Ranger/Big Bertha pair has produced at least three generations of descendents. There was the downscaled TK-3/#803 Mini-Bertha (1971), the upscaled #2018/#2165 Super Big Bertha (1989, and reintroduced in 2000) and the #2093 Broadsword (1994) (two models that were essentially twins underneath the paint), the #1261 Baby Bertha (designed by our friend the Rocket Doctor, introduced in 2002, and a current model) and the Baby's cousin once removed, the #2021 Rascal (1990). It could also be argued that the Goonybird line (1973) also represented another branch of the family. There might be other relatives, too. The Ranger/Big Bertha has been quite a protean design that has resulted in an extensive legacy.

The Big Bertha, originally introduced in 1965 (43 years ago!), is not only Estes' oldest design still in production, but is model rocketry's oldest kit design that is still being produced by its original manufacturer.

Mark

P.S. The Big Bertha also inspired other companies to produce similar models. These include Quest's Big Betty and Semroc's Vega (and ?Centuri's Centurion, possibly?)

How are you going to paint your Astron Ranger? Mine is in '71 colors

The Damon Ranger!

Mark

I plan to do the BB in the '69 colors; the red & white looks great! The Ranger?, dunno yet.

Bob

I agree. Estes should be ashamed for moving away from such a great paint scheme. :D

After all the masking and painting that it took me to do that roll pattern on two different rockets, I can't say that I blame them. :eek:

Oh yeah, but the way Estes does rockets now, it would come pre-colored :eek:

In the process of building a Ranger myself and decided to verify fin sizes. The patterns printed directly from JimZ's site, with no scaling (as is) DO NOT match the current Bertha fins nor the Ranger fin pattern given in the plan set distributed thru the NARTREK packages. For reference, the NARTREK pattern matches the Bertha fins and the NARTREK pattern does appear to have been re-printed from the original plans.

I agree that internet info should not be blindly trusted, but it seems that if a scaling process is used, it should be noted, otherwise the plans are pretty much useless at that point.

As a professional involved day to day with construction plans, I would never think of releasing a plan sheet without a precise scale shown OR actual dimensions listed. Any other opinions?

And that's why you'll see an attempt to add a scale to fin/decal scans on this web site.

When you are getting fin patterns scans or decal scans from YORP or JimZ, you need to be sure that you print the scans at the same dpi (image resolution) that they were scanned at. The plans at JimZ's site are scanned at 300dpi, and I believe that the plans at YORP are also at 300dpi, except where noted (e.g., Estes World Federation Star Probe at 150dpi). You can use a graphics program like the free, open source program The GIMP (Windows, Mac, Unix/Linux versions) to adjust an image's resolution (i.e., rescan the image) to the correct resolution.

If you need help in making this correction using The GIMP, let me know and I will outline the steps to take (the process is actually quite simple).

Mark \\.

Sorry for being late to this party...

The original EIRP design, #13, for the Big Bertha, does show BFS-30 sheet stock for the fins, which is 3/32" thick. The oldest kit plan scan that I have shows this was changed to BFS-40, or 1/8" thick. This plan has the line drawing of the Big Bertha in RED ink at the top of the page, so whenever this printing of the plan was released, that's an indicator of the change date.

Comparing the K-6 Ranger fin outline to the K-23 Big Bertha outline, there is a slight difference. The Ranger fin is 1/4" shorter. The outlines are the same in all respects, until you get to the trailing edge. It looks like Estes added 1/4" to the bottom when the Big Bertha was created. This may have carried over to later production of the Ranger, however the sheet that I'm looking at shows BFS-30 as the fin stock.

The EIRP #13 sheet shows the longer fin, BTW.

I just printed out three sets of fin patterns, using Photoshop Elements 5 - one of the EIRP #13 sheet, one from JimZ K-23 Big Bertha file set, and one from the K-6 Ranger set. All three patterns match each other on outline and overall size, with the exception of the Ranger which is 1/4" shorter than the Big Bertha.

I also have a 25-plus-year-old Big Bertha kit, and I compared my printouts with those fins. The root edge length is 3 3/4" on the kit. The three scans, respectively, show 3 13/16" for the EIRP #13 Big Bertha, 3 5/8" for the K-6 Ranger, and 3 13/16" for the K-23 Big Bertha.

Some of these differences can be attributed to the scanners used to digitize them, and to any "cleaning up" that might have been done to the image. Even the original line art might not be exactly the same as what the plan shows - slight image stretching or shrinkage may have occurred when those images were printed. Paper shrinkage or swelling could account for the 1/16" discrepancy, as could the sanding of the fins when the kit was built.

My Ranger's paint job is based on the one in an early-60s catalog:





The catalog photo was B&W, so I just guessed that it was red. I've since added a black stripe amidships.

Wow :eek:

That ranger is as big as a tree :eek: :eek: :eek:

Yes, basically it all falls into the "acceptable range of variation".

I've had many folks tell me I have a great looking (insert rocket name here). No one has ever said that "the root edge looks to be 1/16 of an inch short." :D

Frankly, about the only time really tight tolerances are needed with fins is when pieces need to fit together. The caps on the Sprite fins come to mind. The conformal fins on the Beta are another good example. Even then, FNF is really good for correcting "dimensional inexactness" :D

Doug


.

Well, you're lucky then. :cool:

I first had my Nike Hercules on display as Peter Alway walked by he says, "Fins are too small." and just keeps walking.

Of course you have to know Peter Alway. :D

I've made a lot of clones and nobody has ever taken a ruler to my fins.

The term I've used is "commercially acceptable".

"dimensional inexactness" ??
Is that a precision value ? :D
How far off does a dimension have to be before it is "inexact" ?
I like that sort of terminology....it fits into my hobby philosophy of "good enuff/that'll doo"

I know Peter :)

I should have stipulated that for scale models, the tolerances are obviously a little tighter, but even then, I agree, less than perfect is indeed commercially acceptable.

I had a similar experience with my Sprint clone. I showed it to Buzz McD who promptly informed me the fins wouldn't do. Seems the aggressive leading edge sanding I did altered the profile enough to take off points in "classic" competitions ;)



Doug

.

Boy, you did go heavy on the sandpaper! :p

I don't know if you got a good enough angle cut on the front and back end of your launch lug, either. :rolleyes: :D

Well I am with him there. And those Cherokee-D fins! Way too large! ;)

And the top stripe is too low. :D

Honestly there is a lot of leeway on a clone.

Where have you seen a "clone" competition? :confused:

Buzz McDermott, now of MASA, used to have a presentation called "Cloning the Classics". I saw it when DARS hosted NARCON back in 2000, IIRC. A year or so later, at a DARS launch, he conducted a contest for classics. I had a couple of new Midgets and showed up that Sunday, chomping at the bit to show off my craftsmanship, only to learn the contest was Saturday-only :o

Anyway, a few years later, we had another one, and have been doing them every year since. We even included it at NSL a couple years ago. Gary Briggs runs them, and I help out. We have several categories allowing for originals and clones (& repro kits, too) as well as upscales and downscales.

It's becoming a tradition, and we're starting to morph the rules a little to keep it interesting. The events get a good turnout, and are slowly growing in popularity.

Not sure what other clubs around the country do, but surely we're not the only one doing this kind of event. I figure, with all the middle aged old far....er....BARs out there, there's gotta be lots of fliers wanting to bench race their clones.

Doug

.

Very interesting...I never heard of that.

I like it! :D

I want to say it was around 1991~92 that HUVARS held an upscale contest. There were a lot of really good entries. Roger Wilfong had a BT-60 Gyroc and BT-101 Ramjet. Both flew really well. I had a BT-60 Screamer and StingRay. Al De La Iglesia flew a really nice BT-101 cluster Cherokee DDD. I believe there were a lot of Mosquitoes as well. *LOL*

SoAR has started doing a "Legacy" competition, bringing back "interesting" rockets from yesteryear and attaching some sort of competition to it. Our first was the Mach 10 from Centuri. I personally had never seen one work well, but we had five entrants and all five flew great. The winner, from John Lawrence, flew spectacularly (and repeated its performance this weekend at NSL).

The second is supposed to be the Gyroc. So far the only one that's been tested is one built from the BMS kit. It went unstable immediately after clearing the rod, throwing its motor out once the delay started burning. I'm assuming there should be some nose weight applied.

I've flown a ton of Gyrocs. They've all been stable. I've never added nose weight. Everyone's MMV though.

The best Mach 10 flight I've seen was Shaun Switenky's. He made his with a movable elevator that popped into glide position at ejection. It boosted straight up, transition into a flat non-turning glide with the wind and he lost it. :p

I've had that happen with my Geminee and CiCi2. I've learned to trim then with a little turn :o

Doug


.

It was the first flight (and last). I believe Shawn 'thought' there was a slight turn in the trim. It was a breezy day and my guess is the wind won over the slight trim turn.

OK, I'll stop hijacking the thread. :D

Hi all,

Well, after several months of volunteer work, etc., it's back to the rockets. I have a Semroc Goliath under construction as practice for the Ranger 3 motor cluster build.

I have a question though... After assembling the motor tubes, installing the blocks, and installing the group into the rear of the model, the lower body appears somewhat oval shaped. I can't tell if it's an optical illusion due to the 3 closely spaced tubes that are glued inside or ?

Plenty of time was allowed between steps, and all was as straight as a non-jigged assembly can be (built over a plate glass sheet and Tamiya cutting mat & used a flat wooden block to seat the assy.) Now, after the glue has dried, I've noticed that while handling said unit one can hear the motor tubes "click" when the tube is slightly tweaked from handling. Glue was applied ~1 3/4" of the way from the rear and ~ 1/4 of an inch from the rear. When the 3 motor cluster BB was built years ago, none of this cropped up. Any ideas?

Bob

p.s. Who has fin marking wraps for Centuri tubes? I really like Semroc kits but HATE the marking "guides" Finally used 3M blue tape to hold the tube to the printed guide in order to hold it in to place for marking. I'd hazard a guess that the printing process doesn't allow matching to the body tubes.

Payload Bay has a fin marking guide and other great rocketry tools.

http://www.payloadbay.com/page-Tools.html