Downscaling The Centuri Hornet to a Card Stock Model Part 6

Here's a finished image of the PDF plan.
Don't print out and try to build from the image to the right!
You'll need the actual full-size PDFs.
Patreon members can email me at: oddlrockets@bellsouth.net
Send me a request for the HORNET PDF.

My cardstock models are a bit different. The 24 lb. paper skin is glued over a BT-20 tube. This makes them much stronger than a regular home rolled cardstock tube.
Notice the fins are a mirrored image, the center fold line will end up being a rounded leading edge. The trailing and outside edges are cut square.

After the fins are scored and sharply folded cut out the fins oversize or outside the border and color areas. The "skin" is glued over some cereal box cardboard. Use a glue stick. (Rough up the printed side of the cereal box piece for a better glue bond.)
The back side of the fins are purposely over sized. This guarantees color coverage when the fins are cut to size.
When cutting out the three ply fins, cut on the very thin line on the side that says "Root Edge".

These are by far the cheapest and easiest models to paint!
No balsa filling or painting is required, except if you use a balsa nose cone.
Keep your hands clean when gluing together a carded model!
You will want a good clear coat on these after the model is glued together. Any water will make the ink run and smear. Don't clear coat before assembly, the clear will seal the carded surfaces and the glue bond won't be as strong.

There are plenty of other card stock models available to Patreon members!
Just click on the Patreon FREE PDFs link above.

Downscaling The Centuri Hornet to a Card Stock Model Part 5

1982 Catalog page

1983 Catalog Page

When you do research in old catalogs you sometimes find inconsistencies.
Right now I'm trying to scale the large decal and find it's correct positioning.

The "Magnum" Hornet was introduced in the 1981 Centuri Catalog. See it HERE
It had a black band stripe around the body tube below the fins, as shown in the right picture.
In the 1982 catalog (shown above left) that black band disappears. See it HERE
In the 1983 (shown above right in the last Centuri catalog) the black band is back! See it HERE

The 1982 catalog page is the easiest picture to work from.

The vertical black stripe from the "H" back to the leading edge of the single black fin is about the length of the fins root edge.
The "stinger" on the forward end of the Hornet is about 1/2 the body tube diameter.
When you don't have the original decals, sometimes it's a guessing game. As mentioned before, it'll be real close.

Downscaling The Centuri Hornet to a Card Stock Model Part 4

The available scanned decals were fuzzy. Not terrible, but the edges weren't sharp.
Enlarge the picture and you can see the top online decal scan.

I usually redraw the decals using Corel Draw. Granted on a BT-20 body these will be reduced and most of those soft edges would disappear. Who would notice, right?
Down the road I may want to build an upscale. These are Vector images and can easily be enlarged with no loss of detail. I have it saved and can print as many as needed.

The top image is the online scan, the lower image is my redraw.
There are some subtle differences but I didn't want to spend hours looking for the perfect font.
In the end it took about two hours to redraw the decal.

Downscaling The Centuri Hornet to a Card Stock Model Part 3

After studying old Centuri instructions and taking measurements from online resources a side view drawing was assembled. The Semroc nose cone profile was traced and added.

My first calculations for the downscale BT-20 model gave me an overall height of 10.72 with the nose cone in place and the rear engine mount extension off.

This finished drawing came out to 10.716" tall.
Close enough for me!
Sure, the body tube could be lengthened by 0.004". 

There's still more work to come!

Downscaling The Centuri Hornet to a Card Stock Model Part 2

Downscale models are sometimes a compromise.
You work with all the information you have available and hope you capture the feel of the original and as close to scale as possible.

The original Centuri kit was 19.8" tall as listed in the catalog.
Current Estes specs say the Hornet re-issue is 19.25" tall.
Is the Estes model shorter overall or are they not including the overhanging engine mount and engine hook? That would add 1/2" to the length and closer to the Centuri height.
Since this is to be a miniature of the Centuri version, I'll go with the 19.8" height and subtract 1/2" for the engine mount overhang.


Here's a screen capture from the Centuri instructions.
I drew in a rectangular box that was .736 high, the outside diameter of the downscale BT-20.
The screen capture from the instructions was set over the box and the body tube in the drawing was enlarged to the size of the BT-20 rectangle.

Sometimes these exploded drawings aren't accurate or to scale of the finished kit. If you don't have the original kit,some guesswork is involved.
With what information I can get from the catalogs and instructions, it'll be real close.

The JimZ fin drawing show the full sized fin root length at 2.25"
Divide that by 1.8 and the downscale fin root length will be 1.25"
The available die-cut fin drawing was sized to the shorter 1.25" root edge.

Downscaling The Centuri Hornet to a Card Stock Model Part 1

Down Scaling a model to a card stock version takes some time.

You pick out a model then do some web searches for the instructions.

This time I went to the JimZ website and loaded the Centuri Instructions #5341 

http://www.spacemodeling.org/JimZ/cen5341.htm

The original Centuri Hornet kit was BT-55 based. It came out at a time when Estes had pretty much absorbed the Centuri line. New Centuri branded kits were using BT tubes instead of the Centuri ST tubing.

The above picture is the Estes reissue. This downscale will display the Centuri logo.
The Estes version has the fins glued flush with the bottom of the tube. Centuri's Hornet had the fins set above the rear.
Semroc also has a Hornet kit but it doesn't have the Hornet (bug) drawing in the decal.
This downscale will be from the original BT-55 to a BT-20 diameter.

To get the Scale Factor, the BT-55 diameter of 1.325" was divided by the BT-20 diameter of .736"
The result was 1.8. Every measurement would be divided by the scale factor of 1.8 to get the smaller downscale sizes.

The online Hornet kit instructions told me the BT-55 tube was #30383. Not much help, I couldn't find the length in any catalog.
The Centuri kit nose cone was #71070 which looked to be a 4 to 1 ogive shape.

Here my preliminary figures:

Centuri HORNET Kit # 5341
Carded Downscale Information

Original Model is BT-55 based at 19.8” tall
Allow ½” off low end for engine mount extension = 19.3” tall with NC

Original Height 19.8” divided / by 1.8 scale factor =
10.72” tall BT-20 based downscale with the nose cone in place.
Semroc Nose Cone BNC-20G4 is closest profile at 3” tall
10.72” overall downscale length - 3.0” tall NC = Downscale BT-20 body tube length of 7.72” long

The other available measurements when divided by 1.8 -
Down Scale Launch Lug is 2.22” from rear of BT-20 tube
Down Scale 1/8” diam. Lug is approx. 1.15” long
Down Scale Trailing edge of fin is .41” from rear of BT-20 tube.
Down Scale Fin Root Edge is 1.25” long.

Apogee Peak Of Flight Article Newsletter #306

My third article for the Apogee Peak Of Flight newsletter was published yesterday. You can see it HERE  Look for Newsletter #306. This article explains how to create that sharp paint line around the perimeter of a nose cone. The cover page features the Odd'l Rockets Corkscrew! The nose cone on the left is the finished nose cone used in the article. On the right is the nose cone from the Mini Honest John rocket currently being built on this blog. The Mini HoJo nose cone is a more complicated mask, there is three colors in the test round paint schemes. (The third color, a grey on the nose cone tip is yet to be masked and sprayed.) The Peak Of Flight article goes into much more detail on how to mask the nose cones than I'll be covering on this blog. So check the Peak Of Flight article for the best tutorial information.

Raisin' Maize Build Part 3 Reaming the Interior

I don't know if this is how First Flight Hobbies accomplished this. Here's the way I cut a hole for the BT-5 tube.

Get a 1/2" diameter brass tube and file the edge sharp.
If the brass tube wasn't sharpened, the cob drilling would be very difficult.


Push and turn the sharpened brass tube from the nose cap end. Center it as best you can and while turning make sure the tube is going in straight.
Drill about halfway down the inside of the cob
Remove the tube and push out the styrofoam from the brass tube by pushing it out with a dowel.



Turn over the cob. Pull out and discard the tuft of "silk" from the bottom.

Continue reaming the cob from the bottom.
Keep the brass tube straight and try to intersect the hole you made earlier from the top.

Corkscrew Build Part 5 Kevlar and Elastic Shock Cord Tying

Tying the elastic end of the shock cord below the top of the tube will prevent zippers.

For any "new-be":

A Zipper is when the Kevlar cuts a jagged line down through the top of the tube. This usually happens when the rocket is traveling too fast at ejection. The Kevlar can snap back cutting a jagged line right through a few inches of the upper tube.

If the Kevlar is beneath the top of the tube you can eliminate any chance of a zipper. The elastic shock cord won't cut through the tube.

Here's how to tie the Kevlar to the elastic BELOW the top:

With the Kevlar fed through the front of the tube, mark it just below the top lip of the tube.

You are going to tie on the elastic below that mark you just made.

Feed the Kevlar back through the back end. Long tweezers or a notched dowel can come in handy here.

Tie the elastic to the Kevlar while it is extended out the back, engine end of the rocket. You won't be able to tie the knot inside the rocket from the top. You'll have to do this from the back end.

You can see the mark I made on the Kevlar on the right side of the picture. The right side of the Kevlar is the loose end side. The rocket body is to the left.

I started the knot away from the mark to insure the knot will be inside the body.

This time a square knot was tied to join the two cords.

Apply a small drop of glue and trim off the excess ends.

Feed the elastic back through to the front end of the tube and you are good to go!

Both the Kevlar and knot are below the top of the tube end.

New Kit Logo Development

I'm currently developing three new kits and one accessory for the Odd'l Rockets product line.

Years back I worked as a graphic artist in a hometown print shop.
I spent too many hours working on a phototypesetting machine.
Needless to say, I'm picky about type fonts and how they are set.

I try to find a font that fits the product.
For example - a short and stubby rocket should have a short and stubby font.
The font and logo design should imply what the model is or does.

In the past, I've seen some decal sheets that didn't reflect the kit design. Some vendors would simply set the model name in a standard, boring Press Roman type style.
Other vendors might name their design something like "The ST-67". That doesn't really tell me anything about the model, it's just a number. I try to go for obvious, hopefully clever, names that say what the rocket is.

Before you send off for some custom cut vinyl, spend some time on a free fonts website like:
http://www.1001freefonts.com/
You'll be amazed at what's out there. Sometimes a font can inspire a whole new design idea.

Here you can see the original font and below it the changes I made to have it fit the new UP! Cup odd-ball kit design.

The original font is named Loveladies.
Quite a few changes were made in Corel Draw.

• The "U's" were changed into a cup profile.
  The exclamation mark was turned into a exclamation up arrow.
• The loser exclamation "dot" is now a cup shape.
• The weight of all the letters were "standardized" to match the visual weight of the new "U's".
• The "C" and "P" in Cup were adjusted to be a closer mirror image of each other.
  

Here's a common mistake made in typesetting -

I've set the name "The Flash" four times.

Check out the first example in the upper left.

TIP: Never set a script or hand written font in all capitals!
Even though I wouldn't pick this type style for a rocket, the second example in the upper right is at least readable! Well, maybe not - the "F" in Flash looks a little like an "S".

TIP: When picking your font, remember that setting words in italic implies movement.
Check out the difference between the two lower type settings. Which one would you choose?

Wolverine Downscale "How To" Part 7 Nose Cone

After trimming the nose cone down to the ram jet profile, I decided to fill the two pieces separately. The flat top of the lower section would be hard to keep square it it were filled and sanded with the tip glued in place.

Before using Carpenter's Wood Filler, a dot of masking tape was taped to the center of the lower nose cone part. You can see it just to the side of the tip. This would give me a better raw wood gluing area.

Here's what the ram jet cone looked like, a dry fit just prior to filling.

Wolverine Downscale "How To" Part 6 Nose Cone

After checking the Semroc website, I found there isn't a BT-5 sized Ram-Jet nose
cone available.
One will be made from an exisiting nose cone.

The downsized nose cone will end up being just under 1 1/2" tall (from the shoulder to the tip) or 1.46" tall.

Measure down 5/16" from the top of the Semroc BNC-522P, Sand to the shape shown at the right, removing the gray shaded area.

Cut off the tip at the 5/16" line. You might cut it a little lowerr than 5/16" to allow for sanding the cut side smooth.

Cut the base at 1 5/32" up from the shoulder. Again, you can cut it a little longer for sanding.

The middle gray section will be thrown away.

The tip is centered and glued to the cut off top.

Try to get close to the 1 1/2" exposed length. Nobody is going to measure it and tell you it's incorrect.
If someone does, you're probably hanging out with the wrong rocketry crowd.

Wolverine Downscale "How To" Part 5 Art Placement

You'll have to enlarge this screen shot to understand what was done:

From previous downscale work I knew the width of the BT-5 body wrap would be 1.77" wide. I drew a box to that width and filled it in with gray.

The original kit's fin alignment guide was used for the fin placment lines. It was copied and dropped next to the gray body wrap box, then reduced to fit the 1.77" width.

On the software screen, individual decals spots were redrawn, picked up and dropped into position over the gray body wrap box.

The fins were drawn so they could have the leading fold over the center layer of cereal box cardboard. This gives a rounded leading edge to the fins.

If you are going to build the model, one side of the fin print is wider than the other. This is done to ensure full color coverage on both sides even if your glued wrap is a little off. When cutting through the sandwiched fin, cut the slightly smaller side on the thin black line border.

Wolverine Downscale Part 4 "How To" "Decals"

This is a cropped screen capture from my Corel Draw software.

I loaded in a copy of the decal scan from the Wolverine instructions on JimZs site. The decal scan wasn't very clean and had yellowed quite a bit. I'll have to re-draw it.

In the center is the canopy decal.

I drew lines around the black canopy shape and filled it in with white for this example. Before using it, it'll get filled with black, but I wanted to show the drawn outline.

The rectangles, circles and bars weren't a problem to trace and fill.

The "45" numbers took some tweaking. I found a font that was close and set it directly over the 45 on the decal scan. I had to "push and pull" some of the corner vectors to get it to match up. In the end, it'll be real close.

After everything was re-drawn, the older yellow decal scan is deleted and the new, crisp art is left.

This re-draw won't be used to make a water-slide decal. On my drawing software, the redrawn elements will be set on top of a gray body wrap to be printed on 100 lb. cardstock.

Wolverine Downscale "How To" Part 3 Fins

A trip over to the Semroc "Classics" page gave me a nearly complete parts listing.
Click HERE to see the original size body parts for dimensions.

For example: A search told me the BT-50H body was 7.75" long.
Multiply 7.75" X .56 (scale factor) and the new BT-5 downsize tube ends up being 4.34" long.

Even though I couldn't get the fin pattern from JimZs (see the templates HERE) to print out correctly, I still used the larger images to re-trace the larger fins then reduce them in Corel Draw.

A copy of the oversize fin pattern was loaded into Corel Draw.

I knew the original root edge of the "wing" fin was 2 25" long. I'll use that length to downsize the copy.
I multiplied 2.25" X .56 (scale factor) and got a downsize root edge length of 1.26"

I drew a line parallel to the root edge and made that line exactly 1.26" long.

Enlarge the screen capture picture to understand what was done.

The entire imported fins drawing was picked and reduced so the root edge of the larger wing fin was the same length as the 1.26" long line. With the entire drawing reduced, I could trace the wing, rudder and forward fins to the correct downsize scale.

After the fins were drawn, the background copy was deleted leaving the new fin tracings.

Wolverine Downscale "How To" Part 2

I realize some of this information is known to experienced modelers.
It's repeated here for the benefit of a younger builder or anyone curious about the process of downscaling.


If you are new to the hobby, you might find yourself spending too much time at JimZ's plan site.
You'll find it HERE

The Wolverine instructions are there - click on the Estes logo and scroll down to the Wolverine, plan #0816.
The fin plans are included, but I couldn't get them to print at the correct size. They were way too large! Some plans have a 1" square for reference, this drawing didn't.
A quick post on TRF got me the fin dimensions for my size reference.
Thanks to John Brohm for measuring the fins right through the kit bag!

I wanted to downscale the model from it's original BT-50 to a BT-5 main frame.
Normally you'd divide .543" (BT-5 downscale diameter) by .976 (BT-50 original diameter) to get a downscale factor of .56.

TIP: Using the Scale Factor Charts found HERE
I reafirmed my factor to be .56.
All the original measurements would be multiplied by .56 to get the smaller model dimensions.
Thanks to Jay Goemmer for putting together these valuable charts!