Found Estes Astron Ranger (K-6) Fin info.

My file for the Estes Astron Ranger (K-6) is almost ready to go. However, the pattern I found (on JimZ's site) doesn't have any kind of scale to it. It's one of those "hand-cut-from-a-pattern" kind of fin templates. So, I'm not going to release the .ork file until someone can get me some info on it. I'd prefer a scan of an original template with a ruler for scale

Why won't I release it until then? Well, I'm very uncertain about this... 'cause it's not stable without a payload according to my first look at it. -0.047 calibers? I will update the images I've uploaded when I get that info.

Again, the instructions were found on JimZ's site. Color scheme is based on the 1971 catalog.

Hey Jim,

[Heavy edit during additional research]

The root edge is right at 3.6". How do we know? First, a direct estimate from published dimensions. The stated length of the Ranger is 24" on the card and catalog. Subtracting 3.125" for BNC-60L and 18" of tubes means the fins extend 2.875" behind the rocket. Using that as the pixel scale on the K-6 pattern scan estimates the root edge length as 3.781".

However, we can do better.

A later Big Bertha has fin root of exactly 3.75" (see scan with ruler on https://www.spacemodeling.org/jimz/estes/est1948_bigbertha(beta)/est1948.pdf)

The detailed images and discussion on this YORF thread show that the legacy K-6 Ranger had a root slightly shorter than most Berthas. See https://www.oldrocketforum.com/showthread.php?t=8173, but the absolute image scaling there is all broken. Nonetheless, using the "family portrait" image from post #27, and taking the K-23 Bertha to have 3.75" root, then the Ranger had 3.595" to pretty good accuracy.

This last thread reported that Vern said that the Bertha fins were *intended* to be identical to the Ranger, but obviously there were some drafting differences, and they overstated the length of the Ranger by a bit over 1/4".

One more edit on stability - I have 0.75 cal to the good with 3xB6-4 using my parts database.

Thanks for that Dave!!!

I'm at work right now. So, it'll have to wait a bit, but I'll get it posted soon.

OH! And you may have given me the tools to answer a question I've got on another sim I'm working on. What is it? It's hush hush right now.

J'im,
take this w/ a grain of salt, a while back when I was building my md bertha, I bought a 'bnc-60L' nose from Semroc and noted that it was longer than the current plastic versions(and Carl told me that he measured Vern's bertha nose). I also used a set of Baby Bertha fins...the current version and the md version are the same overall length. which leads me to believe that the baby bertha fins are the same size (and thickness) as the original Ranger/ big bertha fins. so to get a proper (in my belief) clone of the Ranger, get the Bnc-60L nose from erockets and use the baby bertha fins. I cheated when I built my 'wannabe' ranger clone, I gave it a single 24mm mount .
Rex

K'Tesh, I flew my Ranger in about 1971 on 3 x B6-4s. It absolutely was astounding. One of my most memorable flights, using Centuri Sure-Shot lighters (which worked perfectly).

If I can remember, next month I will pull the dimensions of the fins when I have access to my rocket folders. (The manila paper kind. . . ) Yes I am old school.

Here ya go.

Thanks for that... Woody was able to send me some images too of an original with scale. I've been too tied up at the moment to finish it.

K'Tesh said:

Thanks for that... Woody was able to send me some images too of an original with scale. I've been too tied up at the moment to finish it.

Click to expand...

@K'Tesh, Did you ever finish measuring this and lock down Astron Ranger fin dimensions you're confident in? I'm starting a cardstock downscale to BT-5 (will be single motor, as even MMX won't fit) and I can go forward with what I've got if I have to, but it looks like you have better data than I do.