A Reminder On What To Scan, And Why

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.....OpenRocket's ..... "Chuck Norris"
TRF Supporter
Mar 27, 2013
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A Public Service Reminder...

As you may or may not know, I'm always looking for resources on old and new kits so that I can sim them in OpenRocket, or (hopefully) build or clone them someday. I'm sure that a lot of others are too.

When you've got an old kit, please check to see if the instructions, fins, and decals are archived either at plans.rocketshoppe.com, or JimZ's site. If what you're building isn't there, or are somehow different, or the image they have lacks any kind of reference to it dimensions (including thickness), is bad (e.g. diecrushed fins), or they only have is a drawing of the fins, I'd ask you to scan yours with a ruler, and post them either here, at YORF, or at TRC (preferably all 3). Photos are good for documentation. But scans are far easier to gather information from.

Did you know that Estes has changed its tags over the years? Sure! Who doesn't? Those tags can be really helpful for a BAR in IDing the variant they want (either on Ebay, or trying to clone). Including that information will help a lot of people.

Did you know that since the 1970s Estes instructions have part numbers and revisions? This may help you pin down the year that your kit was made. The longer a kit has been in production, the more likely that it has somehow evolved over time... Especially the older kits. Hand cut balsa gave way to diecut (crushed) fins. Balsa nosecones were replaced with plastic, then balsa, then plastic again. Shapes of nosecones evolved over time. Engine mounts have changed locations and sizes (Remember the short-lived short E motor Estes had back in the 90's?). Decals change on occasion (and not always for the better... (Estes Wizard)). Even body tubes have changed lengths (There's the Cherokee D with the 16.35" body tube that was later changed to a 18" body tube). All these changes lead to a plethora of variants (I'm looking at you Big Bertha... Alpha... and especially YOU, Omega!), and there's always a chance that someone that is out there that is looking to create that rocket that they got (or didn't get) for Christmas, or their birthday that year. You'll help them (and me) if you can scan those instructions.

Many times I've found that the drawings of a rocket's fins are off. Tracings outlined from them often causes them to become too large, or the angle or lengths that were given by the person doing it was off. There's nothing quite as frustrating as spending time trying to recreate your old favorite (including wasting valuable decals), only to have your eye constantly drawn to something that just seems... Off. Then to find that your resource didn't proof the drawing or measurements. RocketReviews.com has more than it's fair share of really bad .rkt files and poorly simmed fin templates.

These things are SOLID GOLD... Nothing can bring a rocket to life quite as much as the colorful decals that came with a kit. Sure, there are those who don't want to have a cookie cutter version of their rocket (and more power to them). However, often it's the markings that drew many of us to a specific design. It'll help a whole lot of old BARs recapture that feeling of having an old rocket that they lost to time, or scratch that itch they had when they weren't able to buy/build the kit of their childhood dreams. Again, keep in mind that the longer the kit's been in production, the more chance that there have been changes to the decals.

I've found that .png and .tif files are much more reliable for creating useful tracings of in making my .ork files. However, sometimes my browser doesn't like .tif files, making them a pain sometimes. Pdf files are great (sometimes), but I can't always right click and copy an image, making them a source of frustration as well occasionally. Then there's .jpgs. Jpegs are common, but extremely problematic for me. Unfortunately, my skills with high power (read: expensive, or feature laden) image processing software is very limited (by my knowledge on how to use them, or ability to purchase more intuitive versions). Jpeg files compress images in a manner that frequently makes finding edges a royal PITA. Toss in a curved edge, and the frustration only increases. DPI? Maximize this. 300 is good, 600 is better. Please remember to have a ruler in your scan, as well as something indicating the thickness of the balsa, or other flat parts (oddball centering rings and the like). A Digital Micrometer is a very useful tool to have for gauging thicknesses. They aren't really expensive (mine was less than $20 USD at Harbor Freight (I brought mine with me to China)), and I'm sure you'll find it useful for other things once you've got one.

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Jim, do you have tips for kits with vacuformed or injection molded parts? I have a Mercury Atlas, and a 1284 Shuttle I was going to try to document well enough to use to make STL files (or the equivalent). But I don't have real 3D scanning equipment. I'll try the free and or cheap apps, but I'm not sure that looks promising.

I'm going to try to cast the vacuforming. Probably first into investment, then into aluminum. But that's not exactly scalable.

Regrettably, my experience with that kind of problem is very limited.

I'd say scan 'em if you got 'em. You might try contacting Maker's clubs at your local College or in your community to try to find someone with a 3D scanner. A local community college in Portland Oregon (PCC) had a scanner that I tried to scan the Cineroc camera with. However, the undercuts were too complex for it to cope with.

Good photographs from multiple angles may be another way of achiving parts like you want. I seem to remember that there is software that can take images and generate 3D files from that, but I have no first hand experience with that nor what it is called.

One thing that *MIGHT* work is to make a plaster cast of the female side, and use to that for a one off copy using a vaccuform machine. Again... No first hand experience.
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I can add a few comments about scanning, having done a lot of it, and also having done a fair amount of Photoshop/Gimp cleanup of decal images (I'm pretty religious about scanning kits that I build too).

Doing good scans takes some work, consistency, practice, and checking.

Scan instructions at 300 dpi. 8-bit grayscale is usually fine. Assembling the instructions into a single PDF file is nice for posting them to a website.

Scan fins, cardstock parts, and similar items at 300dpi, 8-bit grayscale and save to TIF.

300 dpi is WAY too low for any color work, especially if you will be processing the resulting scan.

Calibrating your scanner with a color target is a good idea.

Scan decals at 1200 dpi, in 24-32 bit color, and save as TIF. Do your cleanup edits on copies of the TIF files. Only convert to JPG *once* for output. The Jpeg format does not withstand multiple edits very well at all.

Scan kit cards and headers at 600 dpi, also in high color depth. For a lot of kit cards you'll have to stitch two and possibly three images.

With modern equipment, scanner document sizes will be nuts on because the scanner dpi is very precisely known. What you have to watch out for are software operations that may rescale/resize the image without telling you, and without preserving the pixel sizes (or even the aspect ratio). Genuine Adobe packages (Acrobat, Reader, etc.) will always provide correct dimensional handling (hint: never choose "fit to page"!). Various other packages that convert to PDF are suspect; be wary of "print to PDF" menu items. There is a lot of crapware out there with buggy image handling. Test your workflow to make sure that you are preserving dimensions. Having a ruler is a useful sanity check, but it only checks in one dimension (won't catch aspect ratio problems) and having to rescale back to the ruler size will lose accuracy compared to keeping the correct pixel dimensions all the way through.

Also be sure to weigh and measure all the parts. This is vital if you want to build a good simulation file later.

For "special case" 3 dimensional parts (a "cloner's nightmare" part is the 1-into-3 staging adapter from the Estes MIRV), get some basic measurements and photos all around. This will enable creation of a 3D model later, even if not by you. If you are lucky enough to have a 3D printer/scanner combo, use it.

There is a good survey of photo-to-3D model options here: https://www.sculpteo.com/blog/2016/01/20/turning-a-picture-into-a-3d-model/ The most well known package for doing this is Autodesk 123D Catch, which is free and reasonably capable.
Actually the correct resolutions for scanning are:

Grayscale line art (no photographs, just black and white text and drawings like most instruction sheets):

* scan at 1200 dpi grayscale
* convert to 1 bit (sometimes called bitmap) using a threshold or levels function
* save as TIFF using LZW compression

Color line art (decals, drawings) (that will be reproduced at actual size):

* Draw a 1" scale line on unused area of artwork
* scan at 300 dpi
* save as TIFF or 24bit PNG

Ideally the decals would be converted to vector artwork using software like Adobe Illustrator, either by hand or by auto-trace. The JPEG file format should never be used for line art - it will introduce jpg compression artifacts that are very difficult to work with.

I don't understand what Dave means when he says 300 dpi is way too low for color work. There isn't a magazine or book printed in America that requires more than 300 dpi.

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