Mentioned earlier, the engine mount was recessed a bit more than directed in the instructions. This was so the model would rest on the trailing edges of the fins and not wobble on the extended engine hook. The engine hook finger tab was cut off earlier to give it the old school look.
I tend to glue and fillet the launch lug first, then line up the fin marking guide with the launch lug already in place.
After the Titebond M&TG fillet has dried, I run my fingernail down the recessed fillet to see if it is smooth. If I feel any bubbles or if it is uneven, another fillet is applied.
Once again, the provided Estes fin marking guide doesn't meet up!
Even if it were close I wouldn't trust it.
I'll make up a marking guide by wrapping a piece of paper, marking the overlap joint and folding it into quarters.
That's a shame. I know digital has revolutionized printing, but it is a shame how much crucial, real world measurements are off because of the assumption that digital makes things perfect. Another reason for using your own fin tool.
ReplyDeleteHi Lonnie,
DeleteI don't get it either! On my older kits the wrapped fin marking guides fit very well. I've seen this problem on some Estes kits and many Quest kits.
Perhaps wrong option is being selected when printing (e.g. fit to page)? The original document might have the correct dimensions, but when option such as "fit to page" is selected, the page is resized to printable area -- thus reducing making everything undersize. Since every output device tends to have different non-printable margins, your output size and position may differ according to device.
DeleteA similar sort of problem could occur if you author the document with one size paper in mind, then print on a different size. Common example would be A4 vs US letter. In portrait layout, A4 is a bit taller and narrower than US letter. Resizing to fit the page would case difference in output size. If you keep the original aspect ratio you end up with uneven borders, while trying to make the borders the same by selecting separate scaling for horizontal and vertical would likely stretch or squash image (i.e. a square turns into an oblong rectangle).
The other possibility could be variations in duplication device. Many years ago (in the previous century) I'd run into situations where photocopy machine would unevenly size the duplicate -- especially if you selected enlargement or shrink option. From what I've been able to determine, it was probably an artifact of how the scanner worked -- resulting in "scrunching" on one end and "stretching" on the other. I resorted to performing the duplication in multiple passes - alternately flipping the document between passes.
Hi Naoto,
DeleteThanks for taking the time to write and explain final print size problems. I've been home printing for a while and it can get frustrating.
The reason I brought it up on the post -
This was the marking guide right off the Estes instruction sheet.
Thousands of these were printed up and none would fit the supplied BT-50 tube. (I used a BT-50H, I also tried it on a standard BT-50) I have to wonder how other many frustrated builders there are out there.
Those fin marking guides NEVER work for me. I always use a paper wrapped, taped, and folded into quarters to mark them. That's a tip I learned here years ago.
ReplyDeleteHi Joe!
DeleteWhen you use the home made wrap and fold marking guides -
Mark all four fins then rotate the guide 90 degrees around the tube to the next fin line. Double check and make mark adjustments.
Glad to hear you picked up the tip. Now if it were only as easy to make the three fin guides. I know how to do it, I might do a blog post coming up.
Yep, all sorts of neat "retro" techniques could be used. I remember learning a few tricks back in school during the Euclidean geometry course -- in particular the subject of constructions, where you do stuff with only pencil, compass and straightedge but no ruler. When the topic of how one could subdivide a line segment into equal segments with those tools, the "aha!" light went on and I quickly found ways to apply the techniques in my model-building activities. Was re-introduced to same techniques in a drafting course.
DeleteSpeaking of which... Looking over a text on mechanical drawing could yield useful techniques -- in particular the section on "developments" would be of great interest in relation to model rocketry. Ever wondered how you can figure out the shape you'd need for a shroud between a square tube and round one? Or how about a "slanted" cone (e.g. nosecone on some booster rockets)? Or what sort of shape do you need to cut to join two tubes? of different diameter? at angles other than perpendicular?
Wow, Naoto,
DeleteI was lucky to get through Geometry in High School!
My methods are more try and fail, try again and again, and hope to get it close. I do still use some tricks I've picked up here and there.
I did work for years as a graphic artist. All those techniques are still used in my rocketry building and instruction drawing today.
I haven't had to have a shroud fit a square tube yet. I usually go to "Tools" at payloadbay.com and use the shroud generator and simply type in the tube diameters.
Geometry in ninth grade ended up being a breeze for me partly because I'd been introduced to some of the basic workings of it in fifth grade (actually isn't as strange as you might believe -- the teacher kept with mostly visual aspect with drawings and stuff, as well as demonstration with physical models, rather than concentrating on the part with proofs).
DeleteAnyway... if you enter the keywords "mechanical drawing developing shapes" into Google, you'll find a bunch of links with the information that I was mentioning. It does help to have a knack for special thinking. Nice thing is that when you're working with the stuff with pencil and paper, you generally don't even need to pull out a calculator nor do you need to muck with mathematical formulae. It also helps to have a largish sheet of paper while working out stuff, and know how to deal with orthographic views (aka 3-views). The funny thing is that trying to the same on a computer starts getting awkward very quickly without proper CAD software. Yes, you could use a general drawing program such as Corel or Inkscape (a while back I was using an orphanware software that used be known as ArtLine that ran in GEM on the PC) -- but it quickly gets messy and rather awkward.
Of course, as an alternative to working out stuff yourself, there are handy resources available, such as the Designer's Resource Pak from Apogee Components
Deletehttps://www.apogeerockets.com/Rocket_Books_Videos/Pamphlets_Reports/Designers_Resource_Pak
Nifty parts such as oblique cones, angled tube cutting guides, cone fins, etc.
Re-scaling the parts isn't too hard if you've got access to a scaling photocopier. If all else fails there are several different ways you can rescale. You could construct a pantograph to perform the rescaling, or simply draw a grid on the original and use that as reference re-draw the parts in a larger or smaller size.
The Apogee Components newsletter does contain some neat info
Deletehttps://www.apogeerockets.com/Newsletter/newsletter_archive
Issue #121 has a how-to on making gutting guides for tubes cut at an angle.
Issue #127 has a how-to on making oblique cones