@DaveR
Also, as for rotating the geometry, I personally prefer, to make it a group as is wouldn’t stick to each other, and I can manipulate the placing of the second arc and then explode it once I am happy with the result. you can certainly rotate the raw geometry and move, and then not worry about the grouping / exploding, just not my preference, in fact with my method there is the down size that the arc is now individual line segments instead of a continuous arc. Different strokes for different folks.
Here is template for cutting the desired curve. Since you do not have a large format printer you will get two pages each having two sections you can split and create portion of the curves. You can the either print additional pages to make the total 96 length or make one section for each and use each as portion of scallop B Template.skp (22.3 KB)
templatescallop B.skp (42.9 KB)
As for using ARC to approximate, it is not possible to calculate the length of a sine curve; arcs lengths can be calculated so the sine and ARC is not the same. You need to decide which you want!
Hi folks.
Click in sequence on the scenes tabs of this SU file for ideas.
Notice that the original question asked for a sine wave which is not the same as alternating circular arcs.
Use Push/Pull to widen the board to required width (i.e. 11 in.).
Regards.
Jean
Board with sine wave edge.skp (543.7 KB)
I did go through the different suggested ideas but settled on the the method suggested by DaveR. One of his suggestions that really helped make simple was to create the sine wave by “laying out the scallops on the component but outside of its container”. This gave me the option to easily modify the pattern and get the start/end points exactly where I needed them. In that I was working with a 96" long board it would be easy to just divide it into the number of required sections and then replicate one sine wave along the board. However if you are working with some weird length, example 73 7/16 it gets a bit messy. Using DaveR idea of placing the the layout outside the container, this allow me to cut the ends of the pattern (which was now longer than the length of the board) so they would properly align on the ends of the board (note, at this time the end point did not align with the end of the board correctly). I cut the pattern so it was short of the board length, I then placed the start point on the guide (this guide is outside the board component, I also placed a guide outside the component for the end) that aligned with and then stretch the entire pattern to the guide that was the end point.
Hopefully the above is not too confusing, I know what I want to say but keep getting tripped up with the flow of the description. IMHO DaveR’s method provides the flexibility to easily create a scalloped edge for any board length. Also it allows you to easily smooth out the scallop edge if desired.
That being said… I just installed the Engineering ToolBox suggested by jean_lemire_1.For me it was a bit of hell learning how to create the sine curve, the YouTube are the pits (IMHO). I finally determined how to create the sine wave a bit longer than the board and trim off the section not needed. I’ve created the sine curve outside the board component. I’m able to cut the sine curve to the clipboard but when I attempt to edit the board and edit > paste in place, it does not seem to end up on the board surface and I’m not able to delete the sections of the sine wave I need to remove. I did test and used the erase tool to erase the sine wave and everything is deleted thus it appears that the sine wave is now part of of the board.
In another test after pasting in place I selected the board surface and used the pull tool to pull the board up and the sine wave disappears into the board. in the following image you can see when I try to select just the section of the board I want to remove the surface of the board is selected. I’ll chalk this up to dumb user error but I cannot get past it.
The main advantage of using the Engineering ToolBox is that it quickly creates the sine wave however I cannot get past my inability to get things working correctly.
When I created the sine wave using the Engineering ToolBox it was on a seperate layer and at a 90 degree angle to the board. In my attempt I started with a new SketchUp model and created everything in the model.
Much thanks to all for the suggestions.
Hi folks.
The Engineering Tool box creates the sine wave on the horizontal plane (red-green axes) and in a group.
The group can be exploded and the curve can be rotated to suit any orientation.
To use the Trigonometric Curves feature you need to enter 6 parameters:
1 - The curve type (sine or cosine)
2 - The curve amplitude (how much the curves goes from maximum to axis). For example, a 1 inch amplitude creates a curve that goes from -1 to +1 for a total of 2 inches in variation from min. to max.
3 - The period length. For example 12 if you want one complete cycle to be 12 inches.
4 - The x length (how long will be the curve). Use a multiple of the period if you want an integer number of periods to fit in the curve length. A 96 inches (8 feet) long board will allow 8 periods of 12 inches (1 feet). Or make sure that the period length divides exactly the curve length. A 96 board can accommodate 10 periods of 9.6 inches, etc.
5 - The x difference or delta x. Don’t specify to small to avoid waiting a while for the curve to draw but use a significant number to get a nice result. Using 0.5 inch gives very good result with a length of 96 inches.
6 - The required unit. I used inch in my example but all SU units are available.
My philosophy with SketchUp is to draw the complex part first and then add the easy part after that.
Jean
If you can create one cosine wave, you should be able to piece together what you need rather easily. I used U-V Polygen to create one cosine wave as a start (the actual size doesn’t matter). Dividing 96" by 12" I get 8 cycles, so I duplicated it seven times and stretched the result to 96". Then I stretched the cosine amplitude to 2" and added the 11" board to it.
Jean, I’m trying to follow your instructions but dummy me is confused.
I’ve installed the Engineering ToolBox Extension, went to the Trig Functions, entered what I think are the correct values, see the following.
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“The curve type (sine or cosine)”, I selected sin
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“The curve amplitude (how much the curves goes from maximum to axis). For example, a 1 inch amplitude creates a curve that goes from -1 to +1 for a total of 2 inches in variation from min. to max.” for this curve I wanted an amplitude of 3/4" thus I entered .75
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“The period length. For example 12 if you want one complete cycle to be 12 inches.” I wanted the length for this curve to be 8" thus for the “length of wave (x-value)” I entered 8.
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'The x length (how long will be the curve). Use a multiple of the period if you want an integer number of periods to fit in the curve length. A 96 inches (8 feet) long board will allow 8 periods of 12 inches (1 feet). Or make sure that the period length divides exactly the curve length. A 96 board can accommodate 10 periods of 9.6 inches, etc." I know what you are saying but I don’t see the “x length” but I do see “x end” I assumed this to be the number of times I want the wave to repeat. Is your “x length” the “x end” that I see?
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“The x difference or delta x. Don’t specify to small to avoid waiting a while for the curve to draw but use a significant number to get a nice result. Using 0.5 inch gives very good result with a length of 96 inches.” I have no idea what the heck this is but based on your suggestion I entered .5.
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“The required unit. I used inch in my example but all SU units are available.” I also selected inch.
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In the toolbox function I used there is also an offset, I just left this at 0, 0, 0
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I then click on “Insert!” and nothing seems to happen, e.g. I do not see a sine wave in my model.
We seem to keep beat this issue. I guess this means “we” are not doing a very good of explaining:
- Sine and cosine curves the only difference is cosine pahse is iff set by 90 deg with respect to the sine wave;
- A sine / cosine wave amplitude is specified ref to zero base line so for your case A = .75 is correct which gives you a 1.5 peak to peak amplitude ;
- Correct sort of since you can use multiple periods over the 12", or even like 8.125? In this post Orginal Poster used more than 1.
- The length of a sine or cosine( distance a point as it travels moving along the curve) cannot calculated so either look up tables or program is used. The box should ask for period => your input is correct.
There is no technical reason the length and period have to divide as integer unless the program requires that or you are considering how SU models by segments.
As an aside you do not have to use plugins to create sine curve in SU. If I put chalk mark on a wheel , spin it and look at from side, plot amp vs anglular position you will get a sine curve. That can be done with native tools.
The plugin curve maker can also be used which I used in some of previous post. - In Op post you will notice the plot started at the negative amplitude peak . That is just a phase shift of the curve.
One could just darw crve with more periods adn start at any ref you want including flipping amplitude - No comment
7)No comment have not used tool box - Did you " zoom" extents"
Hi John hi folks.
I tried with your numbers and got a nice curve.
Since you ask for a period of 8 and a length of 12, you get one and a half period.
The dx is the delta X or the interval between two points on the X axis. since you choose 0.5 inch, it means that there will be calculations made at every 0.5 inch from 0 to 12 inches or 25 calculations in total.
Make sure that you enter 0.75 instead of .75. The plugin don’t understand numbers that start with a dot.
Regards.
Jean
Jean, much thanks. Now when I enter 0.75 it works. Too bad the documentation is so poor. I also discovered that “x end” is the total length of the repeating sine wave. Following is a recap of what I did to get what I needed.
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Used the Engineering ToolBox Extension, used the following values for the Sine Wave
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Positioned the left curve so the apex of the neg side of the curve was at the starting point and trimmed off the portion not needed.
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Created a guide at 46.75" for the right edge of the board. (actually I created several guides at 8" intervals but the one I needed for my board was at 46.75")
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Added a vertical line at the 48" guide to give me a reference as to where I needed to trim off the sine wave.
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At the 48" guide I trimmed off the sine wave to the right of the guide and removed the vertical line. .
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Used the FredoScale tool to position the end of the sine wave on the 46.75" guide (before and after images below).
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I now have a sine wave that has an amplitude of +/- 3/4", wave length about 8" but customized to fit my board length of 46 3/4"
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I then zoomed in to show the first 16". Using SnagIt I performed two captures where I captured just a bit more than the first 8" and the same for the 2nd 8".
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I printed both images to my virtual printer (priPrinter) where I could scale the 8" sections to exactly 8", printed 3 copies of each, cut out the sine wave sections, taped them together (I now have a ribbon just over 46 3/4" long), pasted the taped sine wave on my board, cut and sanded the board.
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Assembled the structure. The following image is the completed 8’ section, Currently I don’t have a picture of the smaller section.
This may not be the best procedure but for me it worked and gave me exactly what I needed.
Much thanks to all for the help and education.
This is pretty close to what I’m trying to do myself - is there any way to do this around the side of a cylinder?
If you’re not afraid of parametric equations, you might try this plugin:
https://sites.google.com/site/spirixcode/code/uv_polygen.rbz
Using the following parameters on a 10" radius cylinder gives this:
Not bad - only what I was going for is like a 50mm circle under a 40mm circle that isn’t so much a cylindrical trapezoid with a straight edge as a cylindrical trapezoid with a nice beveled edge. The crown looking piece above is neat though 
Ah, there we go - I figured it out. The trick was to put in a flat plane, set it up along the Z axis then use ‘follow me’ to coax it all the way around the guideline circle. It looks really nice - thanks for the assistance