Saturday, October 5, 2013

Making a Surfboard Template from a Photo or Image

Making a template from an image or photo is very similar to a method for re-sizing a full-size surfboard template.

The following can be done with math solely (see last 7 paragraphs).  Basically you are proportionally re-sizing the image to the length and width you would like for your template.

I will assume you have the picture saved on your computer.  The higher the image resolution is, the better the end result will be.

If you have Adobe Photoshop (or you can insert the image into a MS Powerpoint slide), crop the picture so that the surfboard shape just touches the sides of the cropped rectangle (the widest points, and the tail tip and the nose tip).  The image cropping box method is the quick approach but is less precise.

First re-size the cropped image's dimensions, with "proportions constrained" feature on ("aspect ratio locked"),  to be proportional to the desired "length" (e.g. 7" for 7 feet or 14" for 7' or 21" for 7' etc.)

Next, decide what width you want the board to be.  Turn off constrained proportions (unlock aspect ratio) and type in the width dimension you want using the same scaling used for the length (2" = 1', etc.).

Save and you have a shape that matches your desired dimensions.  (The larger you make the image the more pixelated the outline will become).

You can now transfer the image to graph paper or to template material by plotting measurements onto template material with a grid marked on it (e.g. 1-inch or 2-inch squares).  The template shape will have the exact dimensions you want, based on the dimensions of the re-sized picture.

Use a good top or bottom view photo, and decide the desired length and width dimensions.  BTW the surfboard in the photo/image you will use must aligned in the vertical dimension like atomized's picture (below) for an easy computer crop.  Otherwise, you need to print, crop by hand, then scan and re-size.

I have used a photo posted by atomized at for a quick demonstration (cropping not perfect).  Hand cropping and re-scanning is needed for photos not aligned with vertical or horizontal axes.  Again, all of this can be done mathematically using the original image dimensions multiplied by the proportional change in the desired dimension.

1.  First picture, cropped "quickly" and image length re-sized to 9" = 9'..

Then proportionally re-sized to 7" for a 7' board with dimensions proportional to the original 9' shape, 7" = 7' (width narrows, Aspect Ratio Locked).

Length re-sized to 7" (7') but width remains the same as the original 9' board. (Aspect Ratio Unlocked).

2.  Another example using a Donald Takayama Scorpion photo:

Below, the original image was "quickly" cropped, re-sized proportionally and scaled so length would be 5'10" (Proportions Constrained, Aspect Ratio Locked) width would be less than 21.25", scale 2" = 1'.

After the Image above was re-sized and scaled to a length of 5'10", width was then changed to 21.25" with "proportions not constrained" (Aspect Ratio Unlocked), scale 2" = 1'

Blowing up a photo to full size is not the way to go.  Enlarging the photo to scale -- 1 to 3 inches = 1 foot -- keeping the outline reasonably well defined and then re-plotting to template material, with or without a graph paper intermediate, is the way to use photos or images without using CAD driven design software.

In the Scorpion example, I would not draw a center line/stringer line.  I would measure image width at regular intervals and then divide by 2 for re-plotting as a template.  I like to true up the shape with french curves or ships curves on graph paper before re-plotting to template material.  Even though the photo images are re-sized in inches, I measure the image dimensions in millimeters for re-plotting to graph paper.  The flexible rod/wood-strip method could be used to connect outline points plotted directly onto the actual template material also.

I decided I needed to brush up on my basic Photoshop skills.  So I created several different versions of a much cleaner re-sized Scorpion image, in PNG format (images at bottom of page).  For a surfboard 21.25" wide and 5'10" long, the actual surfboard "image dimensions" should be 3.54 inches wide by 11.666 inches long, where 2 inches = 1 foot.

BTW I did not actually use the cropping method mentioned above.  It is quick and easy but less accurate.  It is easier to explain and demonstrate the re-sizing technique that way also.

Basically, I re-sized the entire original photo of the image.  That re-sized scale image is at the bottom of this page.

1. Print original image.
2. Measure printed surfboard image length and width.
3. Re-size original photo proportionally to get the correct length to for the desired scale.
4. Using the scale for the new length, calculate the desired width in inches and the proportional change.  For example, let us say the new scaled length should be 10 inches.  Original image length is 7 inches.  Proportional change is 10 divided by 7 = 1.43.
5. Unlock constrained proportions (aspect ratio), then proportionally re-size "photo width" accordingly.
6.  Save.
7.  If necessary. I crop the re-sized photo to fit my desired paper size.

Then measure and plot on graph paper or convert re-sized photo dimensions to full-size units and transfer to the grid on the template material.

This can be done using JPEG or PDF template images too to get any combination of length and width.

Re-sizing an Image/Photo with Math

Re-sizing can be done using math solely, re-plotting adjusted dimensions on graph paper or a template grid -- without computer programs.  Let's say the original image is 7.5 inches long and 2.06 inches wide.  You decide you want a scale of 2 inches = 1 foot.  The desired scaled size of the new image is 3.54 inches wide and 11.666 inches long -- for a board that will be 21.25 inches wide and 5 feet 10 inches long.  First, measure image widths at regular intervals along the length of the original image.  For example, you could measure image widths every 0.5 inch along the length.

Now, divide the desired scaled image length of 11.666 inches by the original image length (7.5 inches).  That gives you 1.555.  This is the proportional increase of original image length needed.  So multiply the 0.5-inch length intervals by 1.555 where you measured widths.  Your scaled width measurements will now be every 0.778 inch along the new length of 11.666 inches, rather than every 0.5 inch along the original image length of 7.5 inches.

Widths must now be proportionally re-sized.  Divide desired scaled image max width (3.54 inches) by original image max width (2.06 inches).  Divide 3.54 by 2.06 and you get the proportional increase needed (1.72) for the original image widths measured.  That is, multiply each of the original image widths you measured by 1.72.  You will plot these new widths every 0.778 inches along the new scaled length of 11.666 inches.  Now plot these points on graph paper or template material.  Connect these plotted points with a smooth curve and you are ready to make your template.
Measuring the images in millimeters is more precise, 1.0 inch = 25.4 millimeters.

December 23, 2015

Re-sizing a Full-Size Surfboard Template with Math

It is easy to proportionally re-size a full-size surfboard template and maintain clean curves that are derived from the original template shape.  For re-sizing, you will divide desired length or width by original template length or width, respectively.  
[For an expanded discussion using Lis Fish figures, click this link: ]

For this simple example, the objective is to increase template/surfboard width from 19.75" to 21".  Divide 21" by 19.75".   This gives you 1.063.  Measure widths of the full-size template at 12" intervals.  Now multiply each of the these widths by 1.063 and you have the new widths for the same 12" intervals.  Plot and connect these new width points with a smooth, continuous curve.  You could use the old template or a flexible strip/batten to draw the curved outline.

To make a template shorter, divide the new length (74”) by the old template length (80").  Divide 74” by 80” (= 0.925).  Now place the previous template widths at 11.1" intervals (0.925 x 12") instead of 12" intervals.  Plot the points and connect them with a smooth, continuous curve.

To improve nose and tail shape resolution, you can measure template widths at 1-inch intervals for the first several inches, starting at the template tips/ends.  Similarly, rather than using 12-inch intervals to measure the original template widths, you could use 2- to 3-inch intervals.  Whatever length interval suits you.  The closer together the width measurements are, the better the shape resolution will be overall.

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