I am sorry, I see the error of my ways.
I will go order a few hundred blanks and practice until I am a Jedi master with my rail bands.
I like what you are attempting to do. But your band dims/tangent angles are only good for one specific rail profile (curve). Each different rail profile shape/curve will have its own specific and different band tangents/specifications.
The two (2) rail profile curves below would have very different rail band tangents:
This stuff works great in theory or on a computer.
Your making measurements off a surface with a 90° - most blanks already come with a dome on the deck and once you cut an outline, most of the time your still left with a dome.
Just something to think about.
Might be good tool for reference though.
Looks like its pretty complete. Good job.
I shall crawl back under my nerdy stone, and try not to upset folk with unnecessary sums!
I will go find something more interesting to do with my time… whittling, hmmm…
make this work, gadgetuk. interesting.
Gadget,
I have been thinking more along the lines of a set of standard angles for rail band tangents drawn for any rail profile/outline/curve (e.g. 30, 45 and 60 degrees etc.). With a little geometry/trigonometry it should be fairly simple to calculate any rail band width for any given profile/outline.
What shape/tool did you use to re-draw/modify the top curves for my profiles? An elipse perhaps? I used french curves to create curves tangential to the circles.
BTW I must convert from Imperial to metric and metric to Imperial units fairly regularly for the day job. I will assume you are posting in mm.
Been meaning to buy a simple tool something like this to play with rail band tangent angles for templates:
You came up with this twenty years ago?? But---- It’s based on something you got off of Greenlight’s website??? You still have to take these calacaltions and interpret them by hand. Otherwise CNC can already do all of the above. Why don’t you just put in enough time on the planer to get skilled enough to do a nice rail?? I’m sure this thread will run for quite awhile as there was one done a few months back that went on for weeks. It had all the same sorts of Apex drawings and computer angles just like this one.
my life is a sham
In the time it takes to boot up a computer, log-in, open a program, start a new file, select a specific shape, type in desired dimensions, save and print; I can pretty much draw a circle, a rectangle and a curved line and maybe even a few tangents. Pickett, Alvin and Staedtler make dandy circle and other geometric shape templates and/or french curves. When the power goes out, I can still draw and/or replicate precisely any rail profile template – with automatic hard copy output.
Tangents are pretty much quick draw items also.
The only power tools I use are a hand drill, a drill press, an orbital sander, a jigsaw and a circular saw.
However, MS PowerPoint comes in handy from time-to-time, especially for ellipses with precise dimensions. Photoshop is nice for quick proportional re-sizing of an image.
I’m just a little confused. I didn’t say anyone invented it. I was saying that if y over twenty years ago; how could it be based on anything on Greenlight’s website. They haven’t been around but just a few years. Lowel
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Understood. Took me awhile. Tried to edit my last comment , but that is a function that doesn’t function on Sways. My apology.
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When you get a close-tolerance poly blank or molded eps, the deck is already domed. Regardless of how narrow you cut your outline, you’re basically going to blend your deck bands into this dome. How many bands you will need depends on how much of the original dome curvature you’ve maintained during thickness and skinning.
Most pro shapers use 3 dots on the rail at mid-point to define rail shape and the initial bands; ACE made a good presentation of this with photos on another thread, you may want to review it. Those 3 dots are: (1) Middle of the rail, (2) Bottom of 1st band on rail, (3) Top of 1st band on the deck, measured from the edge in. The relevance to your calculator is that points 2 & 3 will vary with how the blank is domed, board thickness, and rail shape. I’ve seen guys use a table based on a particular blank which gives the measurements between these points for varying the board thickness. However, this only works with the same blanks of a given length range and same designs. In cutting the first band starting at the tail, you go from zero depth to max when you reach the dots, then max to zero going to the nose. You are aiming at those dots on the cut trying to get as close as possible between them. The big factors in getting this right are the angle of the planer and coordinating the depth control with the forward movement of the planer. Practice with the planer off a few times up to the dots and check where you’re at on the depth. Many mastershapers judge the ability to cut rail bands based on how close those first bands come to the dots. Once you have the first band done, you just follow it for the next one and so on. You’re done when the planer is flat or almost flat depending on the dome. This method also helps in matching both sides. When you over do it marking and measuring the blank, you’re basically following lines thinking that if you stay within those lines you’re OK. Took me a very long time to understand that shaping is a hand / eye art and not a measuring one. Three dots, that’s all you need and if you can master that you’ll truly understand what this is all about.
holy Cow.
just shaped a rail with a sureform
this morning,never considered
marking it first,making adjustments
on the fly is inherent in my process
coloring inside the lines is real hard.
On college ruled binderpaper
my letters often straddle the lines
to make the letters line up from the middle.
turning the rails with an artu razor plane makes neat
little square bands.
…ambrose…
My rail band calculators are in my head and I call them my eyes.
I hear the engineers at Lockheed-Martin and Boeing just eyeball the shape/profile of the leading edge of commercial jet wings.
Close enough for flight, after all they are pros…
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