Centuri Star Trooper fin pattern?

[blackshire]

Hello All,

I just finished ordering two sets of parts for the Centuri Akela-1 from Semroc, and I ordered an Akela-1 decal sheet from Excelsior Rocketry. While I was placing that order I noticed that they also have the decal sheet for another old Centuri favorite of mine, the Star Trooper!

The Star Trooper plans in the Ye Olde Rocket Plans archive don't include a fin pattern as such, but a scan of the actual fins along with a US/metric ruler. Alas, the smallest increments on the inch side of the ruler are 1/8" wide. Since the kit was almost certainly designed to inch-based specifications, using the metric (millimeter increments) side of the ruler would yield only an approximation of the fin dimensions.

Does anyone have the dimensions of the Star Trooper fins? Measuring the fin angles from the scan using a protractor, I could re-construct a fin pattern using just one or two of the dimensions. I would gladly share the pattern with Scott at Ye Olde Rocket Plans so that other model rocketeers could use it to clone the Star Trooper.

Many thanks in advance to anyone who can help.

[Vanel]

Digitizing the fin image at Ye Old Rocket Plans gives the following dimensions:

Root: 0.65"
Leading: 1.37"
Top fin tip: 0.15"
Bottom fin tip: 0.31"
Trailing: 1.27"

Hope this helps :)

[barone]

Sometimes it's best to send a PM to whoever provided the plans. :rolleyes:

Actually, the ruler is more of an aid to printing out the patterns. You can check the dimensions of the printed version to see if you have a scaling error. In other words, just print the page that has the patterns. Use your ruler and measure against the ruler on the printout. If they match, all you have to do is cut out the pattern. If they dont't, you can scale up or down the required amount to get it to match.

[Vanel]

Sometimes it's best to send a PM to whoever provided the plans. :rolleyes:

But... But then I wouldn't get to use my spiffy OS X digitization software thingie! :p

[barone]

But... But then I wouldn't get to use my spiffy OS X digitization software thingie! :p
LOL....I see you use that technical language too...... :chuckle:

[Mark II]

Yes, what Don said. If the plans include a scanned picture of the actual fins, I check the scale to insure that I have them printed at actual size on a sheet of 110 lb. cardstock, and then I just cut out one of the fin pictures and use it as my template. The scans of the actual parts usually print out at the correct size in Adobe Reader when I set the Page Scaling dialogue to None. But once in a great while, they do not. That's why it's always good to check the ruler that is including in such scans against an actual ruler. In one recent build, I had to open the scan in The GIMP and very slightly rescale it (by about 1%, maybe a little less). It didn't amount to much (they were small fins), and it wouldn't have really made any difference if I had just left things as they were, but I'm like that. (It's one of the reasons why it takes me so long to build a rocket. :rolleyes: )

Sometimes the pattern is a trace of a fin that has already been sanded and rounded, and sometimes it is even a trace of one that is on a built rocket. (When they put together those scanned plans, they have to use whatever is available, and an approximation is better than none.) In those cases, I check the dimensions of the image against the published fin span. (I subtract the rocket's diameter from the published span number, then divide the result in half to get the chord width of an individual fin.) I then consult pictures of the fin in catalog pictures of the rocket, and using my best guess, I draw an outline of the fin in GIMP right on top of the image from the plans. I assume that the designer created the fin angles using whole and half numbers (not unusual fractions of degrees), that if the kit was produced in the USA, then the designer used the fractional (English) system of measurement and that the designer didn't use fractions smaller than 1/32 of an inch (1/64 in rare cases). Also I make the assumption that if a fin looks like it should be symmetrical, then I make sure that my redrawn outline is symmetrical as well.

MarkII

[A Fish Named Wallyum]

I was going to work something up so that a completed set of fins popped off the computer screen, but couldn't figure out the logistics of time travel. :rolleyes:

[blackshire]

As usual, the wealth of information and assistance on this board is almost too great to measure! I thank you all very much for your replies, and I will use Vanel's digitally measured dimensions to create a fin pattern, a copy of which I will send to Scott Hansen at "Ye Olde Rocket Plans" so that others can also use it. (I have already e-mailed Vanel's [Bill Cooke's] digitally measured dimensions to Scott, along with acknowledgement of Bill as their source.)

I will also donate my original #5 tubing Star Trooper nose cone (the only part I have left from mine) to Sirius Rocketry so that they can cast polyurethane resin duplicates of it as part of their "Moldin' Oldies" line of "Type C" (they also cast "Type E") reproductions of discontinued plastic nose cones. (I know that the Star Trooper's #5 nose cone is almost identical to the Estes BT-5 Gnome nose cone [the latter has a slightly more rounded tip], but like Mark II, I am also "that way" regarding the fidelity of reproduction, with kit clones as well as with scale models.)

[blackshire]

An update on the Star Trooper fins: I printed the Star Trooper fin sheet scan (on "Ye Olde Rocket Plans") using the "no scaling" option with Adobe Acrobat, and they printed out at 100% scale (1:1). I compared the decal set that was also included in the scanned image with my reproduction Star Trooper decal sheet from Excelsior Rocketry, and the two are exactly the same size.

[mycrofte]

I usually convert my fin scans in Adobe Illustrator. That way I can add dimensions or even draw a ruler to help with scaling later on. And it is convenient to save as PDF.