Downsize Cherokee D Carded Build Thread

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hcmbanjo

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I’d downloaded the PDF for this rocket a while back. My problem was - where did I originally find it?
After a few searches brought up nothing, I decided to go to the people who take the time to downsize the classics for the rest of us. I fired off a PM to Bill Harrington. He reminded me that Greg Poehlien had done the work on this one. It still resides in the TRF Archives.

Here's the address:
https://www.rocketryforumarchive.co...8&highlight=downscale+of+some+classics&page=2

Scroll down to post #38 for the PDF. This entire thread is a goldmine for carded builders. The Red Max is a build for another day.

Thanks go to Greg Poehlien for all the drawing and downscaling.

This model was a little different in that the wrap was glued around a BT-5 instead of rolling your own tubing. The printout also give you two different lengths for the main body tube. If memory serves, Estes had brought out the Cherokee D in the shorter version first.
 
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I printed mine on 110 lb. Cardstock. Greg Poehlien recommends 35 lb., 96 bright presentation paper. I looking back I should have used a lighter weight paper. I know the seam match would have been perfect with the 35 lb. Paper. Using the thicker 110 lb. Cardstock, my seam match had a very slight separation.

The reason I used 110 lb. Cardstock was more out of habit than anything else. I use it for my other cardstock rockets when rolling tubes, this model uses the printed body skin directly over a BT-5. The 110 stock works better for me when making “plyed” fins.

Here’s the parts laid out:
BT-5 (cut to 6 7/8", just a bit longer than the smaller wrap calls for)

BC-522P - I went with a balsa cone, this way with filler I could make the area right above the shoulder thicker.
The original Cherokee D nose cone was a BNC-55AC a secant ogive. The large end of the nose cone has a slight flare above the shoulder.
Adding the cardstock wrap makes the BT-5 diameter a little bigger. I'll try to build up a flared end to match the original nose cone contour.

Engine Block (cut from a expended engine)

65 lb. Kevlar X 20"

Not shown - Elastic shock cord, screw eye and streamer.

IMG_1858.jpg
 
First up,
I glued ½ of the fins (one side) to some thin cardboard cut from a cereal box. Beforehand, rough up the printed side of the cardboard with some 220 grit sandpaper for a better gluing surface.

That dowel was used to roll the cardstock flat and remove any excess glue. The half fins were sandwiched in waxed paper and set under some heavy books to dry.

I cut out the other side of the fins, but didn’t cut the rounded corners yet. The corners will be cut off after gluing to the other cardstock side.

Pic 2 Half fin glued.jpg

Pic 3 Other half fin cut out.jpg
 
Nice job thus far Chris (as always)! Much better than my
Cherokee downscale. (Post #177, on Page 9 of
that archived thread)

We'll have to drag race at an upcoming ROCK launch!
 
Whoops!
Sorry about that Bill - I mean Bob!

That won't happen again, I owe you a beer.

More build thread tonight.
 
A pencil line was drawn down the entire length of BT-5 for alignment of the wrap.

I cut the wrap a little longer than needed. This way I could trim it down afterwards. When rolling, I could concentrate on the seam alignment, not on the top or bottom of the body tube length.

I pre-rolled the body wrap just slightly with a dowel. This is going to wrap around the BT-5 tube and may be tight. It’ll need a little coaxing to get it around smoothly.

Masking tape was rolled, sticky side out into a small loop. This was stuck to a larger piece of scrap cardboard. This rolled tape holds down the wrap print side down for spraying with adhesive.

I used my trusty old can of Duro All Purpose Spray Adhesive. That can never seems to run out.

The wrap seam was laid down the drawn pencil line and the wrap was rolled around the BT-5. Everything matched up pretty well with both seams matching up with a slight gap. If I had used 35 lb. Paper, it probably would have been a perfect match. I’m not complaining, there is always a seam in carded rockets. It’s close enough for me.

Pic 4 Pencil line down BT5.jpg

Pic 5 Oversize wrap.jpg

Pic 6 Pre-rolling wrap.jpg

Pic 7 Starting WrapIMG_1863.jpg

Pic 8 Wrap gap.jpg
 
After the wrap sat for a few moments, the seam started to lift. Overall the wrap was down and adhered, just the seam edge was up slightly.

I put a small amount of white glue on one side of my knife and pushed it under the seam. By using white glue on only one side of the knife, you eliminate any chance of getting white glue on the outside printed surface of the wrap. I continued all the down the seam with the white glue. I let the light glue coat dry with the seam still open.

I plugged in my iron while the glue dried.
The iron is set on DRY (no steam) and the heat setting is COTTON.

After the glue was dry, I rolled the clean dry iron over the seam. The iron re-melts the glue and closed up the raised seam.
There is no need to press hard with the iron, let the heat do the work.

Because the underlying BT-5 tube was cut longer than the wrap, I can simply cut the tube down to the edge lines (top and bottom) of the wrap.

Pic 9 Raised Seam.jpg

Pic 10 Glue under seam gap.jpg
 
The PDF gives you small MMX size launch lugs to roll. I wanted to fly this model with “T” engines off a 1/8" rod. I cut longer pieces of cardstock and applied a film of glue to ½ of the piece.
I left the glue film to dry. I preformed the lug by pressing the cardstock into the soft, fleshy heel of my hand. It was wrapped around a metal launch rod and rolled over with a hot iron as before.

Pic 11 Lug wraps cut.jpg

Pic 12 Pre roll lugs.jpg

Pic 13 Lugs finished.jpg
 
The dried two ply fins were cut out on their outside lines. As mentioned earlier, I didn’t cut the rounded corner edges. The third printed ply was cut out earlier.
A film of white glue was set on the middle cardboard and the third layer was lined up and pressed in place.
The third picture shows me lining up the third layer using my fingers on all sides. Be sure there is no sliding of the laminate before setting the fin under books to dry.
After drying, picture 4 shows the rounded corners being cut off through all three layers.
The last picture is burnishing and (slightly) rounding the sides with a convenient tool, the back end of a Sharpie pen.

Pic 14 Fins cut.jpg

Pic 15 Gluing third ply.jpg

Pic 16 Lining up third ply.jpg

Pic 17 Trimming corners thru all three plys.jpg

Pic 18 Rounding edges with Sharpie.jpg
 
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I applied a coat of Carpenter’s Wood Filler to the nose cone and sanded it smooth.
I set the nose cone into a scrap piece of BT-5 to build up the shoulder lip like the original BNC-55AC.
To build up the lip, more filler was applied using a rounded dowel tip. While the filler was still wet, I rolled my thumb around the cone circumference removing the excess and smoothing it out a bit.
The second picture shows the nosecone after sanding. Notice it is wider than the scrap BT-5 it is set in. This build-up will help it match the outside diameter of the printed wrap on the finished model.

Pic 19 Building up NC shoulder.jpg

Pic 20 NC shoulder sanded.jpg
 
The “double glue” method was used to apply the fins and launch lugs on the pre-printed lines.

The engine block was notched to allow the Kevlar to be tied on.
It was glued into the main tube with an expended “T” engine casing. With an engine in place, it will extend 1/4" beyond the end of the body.

If you don't already know this technique, here’s one way to tie the shock cord to prevent a zipper:
The Kevlar was fed through the front of the body tube. Mark the Kevlar where it meets the top of the body tube. Thread it back through to the rear of the body and tie a loop knot with that mark at the top of the loop. Some scrap elastic was tied to that loop. Everything was threaded back though to the top of the body tube.
Using this method, the Kevlar doesn't extend past the end of the body tube.

Pic 21 Kevlar on Engine Block.jpg

Pic 22 Shock cord tied to Kevlar out back of rocket.jpg
 
The nose cone was primed and sanded, then shot with Rustoleum Painter's Touch Gloss Apple Red. It was a good match to the printed red in the wrap.

I know, that’s a BIG screw eye for this size of rocket. I used a larger eye for some forward weight. Being I chose the shorter body tube from the PDF and wanted to be sure the CG was far forward.

The 12" crepe paper streamer was taped to the shock cord 1/3 the way back from the nose cone.

Pic 23 Streamer and shock cord.jpg
 
Finished!
A few lessons learned:
I wanted to fly this one using "T" engines. I made some cardstock lugs to fit a 1/8" launch rod. While you can't see them in the photograph, they look too big on this size rocket.

Next time I'd print the body tube wrap on 24 lb or 35 lb. as Greg Poehlein recommends. My body tube wrap was printed on 110 lb. cardstock. It didn't quite meet when wrapped around the BT-5. A lighter weight paper wrap would probably match up perfectly.
The 110 lb. cardstock does work well for the laminate fins, it gives them a good relative "scale" thickness.

I tried to increase the shoulder end of the nose cone to match the contour of the Cherokee's original BNC-55AC. It really didn't "flare" as much as I had hoped. But, it did fit the body tube and wrap better than it would have without the filler.

Pic 24 Full.jpg

Pic 25 Nose.jpg

Pic 26 Tail end.jpg
 
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Pre-flight notes:
I found some 1/4 A3-2T and ½ A3-2T engines in storage. These date back to 1975. They were in the diamond pack packaging and had the old coated nichrome ignitors.
These were stored in an attic in a Monterey Bay ranch home for over thirty years until I brought them home to Florida two years ago. The Monterey Bay has a very even, dry climate rarely going over 75 degrees. They should be fine for launching the Cherokee “T”.

I'll follow up after the launches.

Pic 27 Old T Engines.jpg
 
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I "lone wolf" launched at the local school yard this morning. Sorry no pics, it was just me.
The Cherokee "T" was loaded up with that 35 year old 1/4A3-2T engine and ignitor.

Upon pressing the button, the old ignitor burned but no ignition. There was just a little gray smoke out the back of the engine, different from when a new ignitor fails. Talk about a flashback - it reminded me of ignitor failures I had when I was a teen.

I'd brought a few new Estes ignitors and prepped it again.
This time ignition and vertical flight. No problems, that 35 year old engine did did very well. The streamer blew a little early and it landed close by. Not a big altitude, but this is a small field so I have to pick engines accordingly.

Boy, those older engines sure smell!
Another flashback to my mother sternly telling me: "Get those (burnt) engines outside and in the trash can. They make the whole house smell like sulphur!"
While all my senses are pretty sharp, my sense of smell is weak. (Just ask my daughters.) But I sure picked up on the thick odor of burned black powder and sulphur after the launch!
 
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