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Rich Holmes
09-14-2014, 08:13 AM
I'm probably going to clone an Estes K-6 Ranger sometime over winter for NARTREK Silver.

Looking at the Ranger instructions (as posted on the JimZ site; also a copy is included in the Silver packet) I'm surprised to see the fins are cut from BFS-30 balsa sheet. BFS-30 indicates the thickness is 3/32".

Surprised because in the first version of TR-6: Cluster Techniques, which was issued the same year as the Ranger (1963), it says 1/8" is the best thickness for cluster rocket fins; and in the 1967 revision it says less than 1/8" thickness can be used but should be reinforced with paper lamination or with balsa ribs parallel to the root edge.

Yet from the same time and same company here's this cluster rocket with long, swept back fins hitting the ground first, and they're 3/32"!

Even more peculiar, in 1965 the Big Bertha comes out, essentially a single motor Ranger, and uses BFS-40 (1/8") for its fins! (Although the Big Bertha plans published in 1963 in Model Rocket News called for BFS-30.)

So what's the story? I presume it really is true the Ranger had 3/32" fins originally. Were they ever thickened to 1/8" before the kit's discontinuation in 1971? Or strengthened? Or was Estes really continuing to sell a design that their own TR advised against?

(Me, I'm considering 1/8" basswood. Maybe papered.)

Earl
09-14-2014, 09:12 AM
I have only seen one Ranger kit before; one I picked up about a year ago. It is probably from the end of the kit run in the very early 70s (early Damon era). It has 3/32 fin stock. I recall being a 'bit' surprised at that choice, but probably is fine for most cluster flights with A and B engines. A cluster of C6s might seem to be pushing things.

Seems like I recall my vintage Scrambler kit has 1/8 fin stock. If the Big Bertha also had 1/8th fin stock, one would think the logical choice for the Ranger would have been the same.

Earl

ghrocketman
09-14-2014, 09:30 AM
My original that I built a LONG time ago has 3/32 fins, as do my Astron Cobra and Astron Scrambler.
The Scrambler lists the B14-5 in a cluster with 3/32 fins as an acceptable motor, which has almost 3 times the kick of a C6 cluster.
I have NEVER had a problem with 3 C6-5's clustered with 3/32" fins.
Glue them on correctly with good fillets and you will have no problems.

1/8" fins on a BT-60 look too 'thick' anyway.

Shamous
09-14-2014, 09:52 AM
It probably also depends on if it Is C grain balsa.

Rich Holmes
09-14-2014, 09:57 AM
Seems like I recall my vintage Scrambler kit has 1/8 fin stock.
Yes, the Scrambler (and Cobra) instructions specify BFS-40, or 1/8".

stefanj
09-14-2014, 11:25 AM
My Ranger clone has 1/8" thick fins. I don't recall which version of the plans I used, but I think it was one of the older ones.

It would be tricky to mount the Ranger's fins TTY, because of the irregular depth available. If it weren't for that, TTW would be an ideal way of stiffening the fins and keeping them on under high-thrust boost.

CPMcGraw
09-15-2014, 09:39 AM
Rich,

The differences in thickness were likely trade-offs in both refinement of the design over time, and in the set-up of kit making. Here's something else to look for: The shape of the Ranger fin is slightly different from the Bertha. Not eye-popping different, but not quite the same either. You might also notice that the BB fin shape from the original MRN plan to the kit version changed over time.

The best way to think about the Ranger and the BB is as a family of designs, which includes the Apogee and Apogee II, the Mini Bertha, and even the modern Baby Bertha. Since the BB was a derivative of the Ranger, you might use the early MRN fin pattern as the starting point.

It's been a while since I looked at those fins, but I know there were differences between all of them.

Rich Holmes
09-15-2014, 10:08 AM
Yeah, I've looked at comparisons of the size and shape of the Ranger, Big Bertha, and Baby Bertha... all similar but all different.*

That doesn't surprise me, but the 3/32" thickness for the Ranger at a time when (and up to 8 years after) the Estes Technical Reports were recommending 1/8" does. Unless there was a change to a thicker fin early on, but I'm not aware there was.

* The MRN (EIRP) and kit BB fins actually were just about the same, according to the information I've found, except for the thickness. Though I think the kit BB fin has changed some over the years, so it would depend on which kit you're comparing.

tbzep
09-15-2014, 10:59 AM
Let's not forget that the nose cone has changed shape over the years also. If you just want a sport Ranger, use a Big Bertha kit with its 1/8" fins and plastic cone and just swap the mount. If you want it to be retro with the 3/32" fins, you also need to locate or turn the proper shape nose cone for that period.

Rich Holmes
09-15-2014, 11:25 AM
I'm actually thinking BNC-60L nose (got one already from BMS) but probably 1/8" basswood fins. If that's inconsistent, well, I'm inconsistent. But to me the look of the nose cone matters, whereas the look of the fins is subordinate to wanting them stronger.

tbzep
09-15-2014, 04:47 PM
I'm actually thinking BNC-60L nose (got one already from BMS) but probably 1/8" basswood fins. If that's inconsistent, well, I'm inconsistent. But to me the look of the nose cone matters, whereas the look of the fins is subordinate to wanting them stronger.
I'd most likely just use a BB kit and swap noses, so we are thinking along the same lines. In fact, that's what my son did with his clone. However, we know that a few folks would dwell on fin thickness accuracy and never realize the nose cone looks completely different from a BB. :p

bernomatic
11-09-2014, 06:34 PM
Two quick questions. Regarding the Ranger model photo on Jim Z's site:

#1 Who determined the color scheme of the early ranger? before it had that roll stripe. All the catalogs I've seen are in B & W.

#2 Is it me, or do the engines in the photo appear to stick out of the rear of the body more than the 1/4" of an EB-20A?

bernomatic
11-09-2014, 06:54 PM
And another question...

The fin pattern I found on Jim Z's site doesn't have a ruler in it to confirm the correct size in printing out. Does anyone know the length of the root edge of the Ranger from an actual kit fin to confirm the size?

tbzep
11-09-2014, 08:18 PM
Two quick questions. Regarding the Ranger model photo on Jim Z's site:

#1 Who determined the color scheme of the early ranger? before it had that roll stripe. All the catalogs I've seen are in B & W.

#2 Is it me, or do the engines in the photo appear to stick out of the rear of the body more than the 1/4" of an EB-20A?
I'm assuming you mean the 1963 Ranger which shows a plain two tone paint scheme. The 1964 catalog had an image with the roll pattern stripe and a drawing with no stripes of any kind. The K-6 plans say to finish the rocket in white, then use red, fluorescent orange, or cerise to make it more visible. I imagine most people who wanted their Ranger to look like the original catalog used the recommendation in the plans to paint their rocket white and instead of painting over the entire rocket with the bright color, only painted the payload section.

Chas Russell
11-09-2014, 08:41 PM
I have two sets of the SEMROC Ranger fins. The root length is 3 and 9/16 inches. I would trust the late Carl McLawhorn's accuracy. He was a bit of a stickler for that sort of thing.

Chas

dvmanning
11-09-2014, 08:42 PM
And another question...

The fin pattern I found on Jim Z's site doesn't have a ruler in it to confirm the correct size in printing out. Does anyone know the length of the root edge of the Ranger from an actual kit fin to confirm the size?

Attached is a full size fin pattern for the Ranger K-6 when printed on Ink jet printer. When I printed the pattern below, it printed in the portrait position from top to bottom giving the root edge 6 1.8". The Ranger is 24 inches tall with a designed fin span from leading edge to leading edge of 5.7 inches (14,5 cm) .
In scaling the image below, I determined that if the attached image is reduced to 58 % of the attached printed scale that the 58% should put the fins close to the correct size within the stated fin span of 5.7 inches.
The second is the reduced scale of 58%. Hopefully this will help, if someone doesn't have the actual dimensions.

mojo1986
11-10-2014, 06:03 AM
I have an original and very vintage Ranger in my built display..............root edge of the fins is 3 5/8 inches.

Joe

astronwolf
11-10-2014, 08:33 AM
Chas: 3-9/16" fin root edge (from Semroc clone)

Mojo: 3-10/16" fin root edge (from a very old original)

close enough for me....but if I ever clone one, I'll probably go all out and add the extra 1/16". :rolleyes: