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  #1  
Old 04-30-2013, 01:18 PM
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K'Tesh K'Tesh is offline
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Cool Build Report: Upscaling the Cherokee D to a BT-60 (123%)

My third rocket was the Cherokee D.

And I loved it. From its sleek, sharply pointed, red nose, to the black and red wraps around that long gloss white body tube, and those CG and CP markings. Of course, who can forget those red swoosh marks (with the NASA written in black below) on those rounded trapezoidal fins and the "louvre" decals at the bottom. It was a thing of beauty, an image of FAST even if it wasn't moving at all. All that, and you could still stick a D motor into it and launch the thing!

Of course, being a kid, I totally didn't do very well on my first and second tries at it. I didn't fill the balsa, I painted the rocket flat white (with runs), the lower wrap tore, and the decals eventually started to flake off (the second try is still trying to flake off).

The first rocket was launched three times and lost each time. First try, a winter day in Ashland, Oregon. The sky was overcast with a ceiling of (I thought) 2000 feet, the ground was covered with snow. The rocket flew straight and true, and disappeared into the lower part of the cloud.... OOPS!

I searched and searched around the school field I was launching from, but no luck. I went to all the neighbors and asked if they found a rocket, and after a cursory search, it wasn't found. This was back in the early '80's and cell phones weren't common by any means. I had to give it up for lost.

Months later... I was in the neighborhood again on a weekend. So, I decided to see if my rocket turned up. I went to the first house next to the school, and was pleased when I was told that they had found my rocket (the same day it was lost) and held on to it for me. I had my Cherokee D back.

Later, I launched it at my Grandparent's ranch on the banks of the Rogue River (rogue like ruffian) and of course, the wind blew it into the river on the far bank. Not knowing how deep it was, I stripped down (much to my slightly younger cousin's amusement) and proceeded to walk across the very shallow (about 8" max) rapids (if I had taken off my pants, my ass wouldn't have even gotten wet). I recovered the rocket sitting in the water stuck between rocks near the shore, then made my way back. The rocket was soaked, and the engine absorbed a lot of water, fusing itself into the engine mount.

Months Later... I tried to get the engine to release, and it moved, a very little bit. After much manipulation, and a pair of needle-nosed pliers I was able to extract the engine. I was back in business.

Another trip to Eagle Point, and the ranch, and I decided to try my luck again (if it wasn't for bad luck, I'd have none at all). The rocket soared, and as it was drifting back (this time towards me, and already on my side of the river) it was met by a very concerned osprey defending its nest. The rocket floated down, and of course, it got caught in the same tree as the nest, well above the area I could safely manage to get to with an angry osprey flapping about overhead. It was lost.

Years later... it was still there, until one trip I found that it wasn't up there anymore. I quickly rushed to the base of the tree, but no sign was to be found of it. I asked my Grandfather if he had it... nope. His brother, however when asked told me that he found the remains of the rocket trampled after it had finally fallen and landed right where the cows like to rest, and he tossed the remains in the trash.

My 2nd attempt looked slightly better than the first (no runs in the paint), but a broken fin and flaking decals made me stop using it.

Now, nearly 30 years later, and I want to make it again... Correction, I AM making it again (the 1971-1983 version).

I've got a few BT-60's and BT-55's left that are not slated for any one project. I've already got the BT-55's decals from Sandman, and the BT-60 decals will be ordered soon. I've already started building it.

Last night I sat down and did the math, I found that a BT-55 upscaled to a BT-60 is a 123% increase in size.

Cherokee D (1970)
Overall .............................21.8"*
Nose Cone.......................... 5.4" (BNC-55AC)
Body Tube........................16.4"
Fins (at the root)..............3.75”

1970 Cherokee D Upscale 123%
Total Length......................26.8125” ~26 13/16”
Nose Cone..........................6.642” ~6 5/8” (BNC-60AC is actually 6.7” or ~6 11/16”)
Body Tube(s).....................20.1875” ~20 3/16”
Upper tube.........................
Lower tube.......................
Fins (at the root)................4.6125” ~4 5/8”



Cherokee D (1970-1983)
Overall.............................23.4”
Nose Cone..........................5.4” (PNC-55AC)
Body Tube........................18” (BT-55)
Fins (at the root)................3.75”

Upscaled 123%
Total Length......................28.78” ~28 ¾”
Nose Cone..........................6.642” ~6 5/8” (BNC-60AC is actually 6.7” or ~6 11/16”)
Body Tube(s)....................22.138” ~22 1/8”
Upper tube.........................6.765” ~6 3/4”
Lower tube.......................15.373” ~15 3/8”
Fins (at the root)................4.6125” ~4 5/8”

*The Cherokee D always was listed as 21.6" long in the catalogs.


Since the body tube length is longer than 18", I’ll need to make the rocket in two parts (and I'm going with a zipperless design parting at the coupler). The upper section will contain the parachute, and will consist of the nose cone (a BNC-60AC from Semroc (on order)) , and a short length of body tube 6 ¾” long. I chose this length because on my Cherokee D, I had the bottom edge of the lower wrap at 5 1/2” below the top of the tube. The lower portion will contain the motor mount, fins, both lugs, shock cord (connected to the upper section) and a baffle/coupler.

Last night I cut down the tubes necessary, built up the engine mount, and I slotted the tube for the fins.

I don’t have the nose cone yet, so an old parted out Mean Machine’s nose cone is filling in for the moment. I plan on cutting out the fins tonight, and making one of the 18” parachutes I found in my stockpile.

My plans on marking the rocket is to have both wraps located above the separation line, and I like look of the "louvres", but up (pointed) side down (IMHO it'll look more like the "turkey-feathers" of a jet's afterburner). The CG and CP decals will be placed as on the original, but I am planning on adding some weight the nose to move the CG a little further forward.

Thanks for Looking TBC.
Jim
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.

Last edited by K'Tesh : 06-19-2013 at 02:42 AM.
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  #2  
Old 05-05-2013, 01:28 PM
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K'Tesh K'Tesh is offline
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Cool NOW! With Pictures...

Heres my upscale in progress, and its inspiration...





I based the separation point on the bottom of the lower wrap. It seemed like a reasonable area to hide the joint between the lower and upper sections of the rocket. The nosecone in the photos of the upscaled rocket you can see is a place holder that I had from an unused nosecone from a Mean Machine. I'm ordering a Semroc BNC-60AC to replace it.



The grain lines you can see on the upscale build's fins are from the printed fin patterns I glued onto the balsa... The older one didn't get it's fins filled.



Oh, and I tapered the launch lugs...



Thanks for Looking... TBC
Jim
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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  #3  
Old 05-05-2013, 07:45 PM
PaulK PaulK is offline
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Always love to see a Cherokee-D thread. Are you building it for 24mm? Next thing you know, you'll be building a BT-70 upscale (Semroc has an exact balsa upscale NC), which flies great on 24mm E/F composites. Make sure to get your decals from excelsior / Sandman!
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  #4  
Old 05-05-2013, 11:24 PM
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K'Tesh K'Tesh is offline
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Quote:
Originally Posted by PaulK
Always love to see a Cherokee-D thread. Are you building it for 24mm? Next thing you know, you'll be building a BT-70 upscale (Semroc has an exact balsa upscale NC), which flies great on 24mm E/F composites. Make sure to get your decals from excelsior / Sandman!


I'm building it to take D and E engines, but I don't have plans on going up to a BT-70 any time soon. The decals will be from Gord. I have to finish University, then Lord Willing, I'll be on my way to Asia to teach English.

I'm planning on finishing the rockets I have, then loaning them to local schools to inspire the next generation of kids. When I'm stable, I'll be able to recall some of them for my own classroom.

All The Best!
Jim
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__________________
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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  #5  
Old 05-07-2013, 06:35 AM
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K'Tesh K'Tesh is offline
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Question Uhm... This doesn't jive... 1/8" or 3/32"?

While I'm building my upscale, I'm also looking at the old Cherokee D I still have (which has lost quite a bit of color lately due to those flaking decals and the handling it's been getting). I've looked at JimZ's site, and he's got the original fin thickness at 1/8". My fins are thinner than that I'm sure, more like 3/32". Anybody else got an old rocket laying around to confirm my calibrated eyeballing of the fin thickness? I ask, because I got with my original order from Gord a set of 1/1 scale decals, and yes, I'm building a 1/1 scale one at the same time (turns out my BT-55's are already claimed, so I'm getting another one of those too).

[EDIT] In poking around the 1974 Estes Custom Parts Catalog , I found that the Cherokee D's balsa fins were available for purchase. Dimensions given for BF-47 (PN 32220) were 3/32" x 4" x9". I've updated the graphic.



BTW, the upscale has 1/8" thick fins.

Thanks!
Jim
__________________
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.

Last edited by K'Tesh : 01-10-2017 at 09:11 PM.
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  #6  
Old 05-07-2013, 11:03 AM
Rex R Rex R is offline
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the longer version might have had thinner fins (or someone got carried away with sanding them smooth ). the plans on Jim-z's site are from the 'short' version(as is the semroc reteo version) both call for 1/8" fins, hm shouldn't the upscale fins be 5/32"....
rex
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  #7  
Old 05-12-2013, 08:05 PM
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K'Tesh K'Tesh is offline
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Unhappy Ok, now I'm certain... or is that certifiable...

Quote:
Originally Posted by Rex R
tthe plans on Jim-z's site are from the 'short' version(as is the semroc reteo version) both call for 1/8" fins, hm shouldn't the upscale fins be 5/32"....


I pulled out a bit of 3/32" balsa, and was able to determine that the fins on my original Cherokee D was 3/32" and not 1/8". I papered the fins, and slotted the tube on the 1/1 scale clone (D-E engine capable). The clone is a modified Estes CC Express (which gave me some leftover parts to mod my Estes Venus Probe). Running the numbers, 3/32" upscaled 123% is a lot closer to 1/8" than 5/32" (without going over by much)

3/32"*1.23 = .115"

1/8" = 0.125"
5/32" = .156"


The 1/1 and 123% upscale both got primed yesterday, but I learned two very important lessons:


Three Cherokee D's (before the problem with the 2nd primer coat)


NEVER!!! again will I use white primer (even if it's wet sandable). Imperfections are too hard to see to be fixed with it.

ALWAYS!!!! read the instructions on the paint can before putting on the 2nd coat. I decided to go over the upscale's white so I could see what was going on, but I didn't wait 24 hours. A large portion of the bodytube's paint work bubbled up. The white primer requires paint be reapplied in less than 1 hour, or after 24 hours... I waited 4. I brushed the bubbled portion, and it peeled off like it wasn't even adhearing. I rubbed off as much as I could before it set up, but it's got some really ugly... umm... stuff... going on.

Today I went and bought some filler grey primer, and I'm hoping that when I can paint again, I'll be able to fill the damaged paint areas and get it sanded down and looking sharp again.

The red nosecones turned out well... Sanded the nosecones first with 320 grit, then 400, and finally with 600 wet or dry. I then used a tooth brush, and some Colgate to do the final prep work, and painted the red straight on once it was allowed to dry. I've learned with gloss colors, despite whatever the cans say about "dry to touch" not to handle the part directly for at least four hours, and be gentle with it until the drying process is complete (1-5 days). I'm still waiting to place my order for the upscale's real nosecone and decals from Gord.

Thanks for looking... TBC
Jim
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__________________
.
.

Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.
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  #8  
Old 05-12-2013, 09:44 PM
Rex R Rex R is offline
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Dupli-color has some nice primer, likewise 'Bondo' (usually with the automotive supplies). both are lacquer based and can be sanded after an hour.
my bane is gloss white...you can't tell what you're doing .
Rex
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  #9  
Old 05-20-2013, 12:54 PM
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K'Tesh K'Tesh is offline
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Lightbulb Well, it's primed again...

Yesterday, I primed the rocket using filler primer. It's not done with being primed, but the results so far are encouraging. I was able to sand the intersection of the undamaged and damaged areas down quite nicely before I started to see body tube. Another coat or two of primer, and some more sanding, and it may be ready to top coat.

The fins are looking quite nice, the fillets need some work. Any ideas?

Thanks
Jim
.
__________________
.
.

Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.

Last edited by K'Tesh : 05-20-2013 at 01:34 PM.
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  #10  
Old 05-23-2013, 02:14 AM
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K'Tesh K'Tesh is offline
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Unhappy Photo of the damaged paint job.

Heres a photo of the damaged primer coat...



I'd love to post more, but I can't figure out the changes flickr did to their site, and it's ****ing me off.
__________________
.
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Dreaming of making the rockets I dreamed of as a kid (and then some).

"The Guide says there is an art to flying", said Ford, "or rather a knack."
"The knack lies in learning how to throw yourself at the ground and miss."


Launching is Optional... Landing? That Depends on Trees.

Last edited by K'Tesh : 05-23-2013 at 02:59 PM.
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