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Best two scores on this computer:

Score Time Name

8.26 77 s JMBjoinery

Cool little excercise!

Overall score: 4.40

Total time: 113.97

Here’s my approach. I am usually simultaneously trying to figure out the spacing as well as how many boards I need.

I prefer to plan ahead to the end result, and make a spacer block that is properly determined, rather than just assume 2” is going to result in a nice width for the final boards. You might start center out and discover that the final boards wind up extremely narrow. That’d look weird!

For below, I assumed your start and stop points will be a fence board (not a gap).

The SS is deducted on the left side of the equation, because the last board doesn’t get a follow-on spacer.

If you want gaps at the start/end, then ADD the SS to the left side, instead of subtracting it.

First, add up the total lineal distance you need to cover.

Your specs: 73", 2nd section 76 1/2", and the third is 82 1/8" = 231.625” lineal distance

Add up the total of your fence boards + spacings and begin to calculate.

Tweak as necessary to arrive at the above figure.

Formula: ((WW + SS) x YY) – SS = LD

WW = width

SS = spacing

YY = number of boards

LD = Lineal Distance

Use the desired approximate gap to solve once for YY, to get an approximate number of boards.

Then substitute YY with the lower integer.

Then re-solve for SS

Example:

Solve for YY:

(5.125” + 2” spacing) x YY number of boards - 2” = 231.625

7.125 x YY = 233.625 YY = 32.79 boards

Round this down to 32 boards if you want the spacing over 2”. (You could also round up if you don’t mind having less than 2”).

Solve again, this time for the spacing SS:

(5.125 + SS) x 32 – SS = 231.625

(5.125 x 32) + SSx32 – SS = 231.625

164 + 32SS – SS = 231.625

Move this parts across the equals sign:

32SS - SS = 231.625 – 164

31SS = 67.625

SS = 2.1814” The value is between 2-1/8” and 2-3/16”

In this case, it is pretty close to your 2” desired gap.

But, say you had gone with exactly 2”, you would be off by a total of 5.625” at the end, and would have a final board that is ½” wide, or you trim the start and end boards by about half their width… Not great results IMO.

So, make some spacers 2-3/16” in width and your last board’s width will be only a very minor adjustment.

FYI, if you want to start and end with spacing gaps: then 2-1/16”