Reading a Doyle Log Scale Ruler

[Lasershark]

So I purchased a log scaling ruler, but it didnt come with instructions and google searches yielded sparse info.


  

 



 
So I understand the formula, but I could have used it with a regular tape measure. How do I correlate the diameter and length of the log to the scale on the ruler?

[stavebuyer]

The bottom scale on the front of the rule is a regular ruler marked in inches. The back side of the ruler has the board footage that corresponds to the diameter measured in inches on the front.. The first line on the back is the footage in a 12 long log and reading down the column you have the board feet in 12, 14, 16(8' you have to divide the 16' number in half. To make it clear as mud the 10' and 18' volumes are printed on the front of rule,

You measure the diameter inside the bark and you will be looking at the footage that corresponds right above for 10' and 18' logs or flip the rule over and get the value for 12,14,16 from the back side.

[Lasershark]

So. if I have a 14" inside diameter and a 16' log, I would choose 32 Bd/ft as the answer as demonstrated in the example below?




 




 

(14-4)^2*16/16
=(10)^2*16/16
=100*16/16
=100 bd. ft.

Seems my math doesn't work out, so I guess I need more explanation. 

[stavebuyer]

The very first column of numbers that you circled in blue on the far left of the rule equates to log length. The top of that left hand column has the number 16 and that is feet. From left to right the rest of the top row of numbers is the board footage of a 16 foot log. In your example the last column of numbers that you circled on the far right equates to the board footage of logs that measure 10 inches in diameter.

So at the 10" diameter the face of the ruler that you are looking at in your photo equates to;

the top number 36bd ft = a 10 diameter log that is 16' long
the 2nd number from the top in the same column is 32 and equates to 32 bd ft in 10" diameter log that is 14 feet in length
the bottom number in the same column is 27 bd ft and equates to a log 12 feet in length and 10 inches in diameter.

The very first section on the folding ruler (reading left to right) is the only place the length is marked.

In your picture that would be the "back" of the ruler. All those numbers are board footage values except for the the very first column which is the log length.

16 
14
12

If you turned the ruler over the "front" the very first segment on the left side would look like this

                            log length
DOYLE LOG SCALE 18            all the rest of the numbers in this row are board footage of 18' long logs
                            10            all the rest of the numbers in this row are board footage of 10' long logs 

All the numbers to the right of the 18 row header equate to the diameter in inches read at the bottom of the ruler, Same applies to the second row to the right of the 10.
 

[stavebuyer]

So. if I have a 14" inside diameter and a 16' log, I would choose 32 Bd/ft as the answer as demonstrated in the example below?




 




 

(14-4)^2*16/16
=(10)^2*16/16
=100*16/16
=100 bd. ft.

Seems my math doesn't work out, so I guess I need more explanation.
 long log would scale 

A 14" diameter log sixteen feet in length would scale 100 bd ft. Measure diameter from left to right.(the folding hook on your extreme left of the ruler.
The very bottom row of numbers is a ruler in inches.
From left to right go to the right until you are at "14"
The very bottom number is 14=14 inches
The number above 14 is "62" which is 62 board feet and equates to log 14" in diameter and 10ft in length
The top number in that column is "112" which is the board ft in 14" diameter log thats 18ft in length
Flip the ruler over to read the board footage values for logs 12ft, 14ft,16ft in length
The back of the ruler opposite of the 14" inch mark will be a column of numbers
100
88
75
The "75" on the bottom row is the footage in 14" diameter log 12ft in length
      "88" in the middle row is the footage in a 14" diameter log 14ft in length
       "100" on the top row equates to the footage in 14" diameter log 16ft in lentgh

[Lasershark]

Alright, that makes sense, excellent explanation, thank you Sir.

[mike_belben]

@Lasershark  

  


Most scalers around here use a "stick" that they flip down the log end for end measuring length with the BF info on it, rather than a folding rule. Hence the expression someone is "tight on the stick." 


Theres a few old family sawmills in doyle tennessee.. I had to look If he was the towns namesake but doesnt appear to be.  


Good link about log scale from purdue, claims there are 95 different scales! 

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[stavebuyer]

Alright, that makes sense, excellent explanation, thank you Sir.

It would only take 30 seconds to show someone standing beside you; the design works well but not very self explanatory.