How to work out m3 of a round log.

[openspaceman]

Pi * D * D / 4 is the same as Pi * r * r

 

 

Possible better writ as

 

=Pi()*(d*d)/4 and bunged in a spreadsheet or =Pi()D^2/4

 

Hoppus is an interesting measure. Hoppus was the chap that bought timber for the dockyards and his system was based on the measuring tools readilly available.

 

I imagine the average yard would only have one accurate measure (a steel yard??).

 

Hoppus would have the middle of a log girthed with string, this length was then folded twice to give a quarter girth which was measured off against the steel yard. Similarly a piece of string would measure the log and be held against the steel yard repeatedly to get the length.

 

The calculated volume would then have been read off pre calculated tables.

 

Now whilst you cannot cut a 50ft3 beam from a 50Hft log you will get approximately 50ft3 of pieces in total including bits of scantling cut from the slabwood, so it was an intuitive measure, unlike m3.

 

Another nicety of using the string to girth an oak log was that you could fold the string into 8ths, discard one 8th and then fold the remaining 7/8 into 4 and use this as the qg, the answer then was a good approximation to the underbark volume.

[Celtictimber]

Nice explanation

[Big J]

Using 3 instead of Pi as an allowance for saw keft and waste doesn't work unfortunately.

 

For instance a 3ft diameter 10ft log has an actual volume of 70 cube (rounded), a hoppus volume of 55 cube and a volume using 3 instead of Pi of 67 cube.

[Celtictimber]

Is there any online calculators to work out hopus foot.

[WeeDee]

Using 3 instead of Pi as an allowance for saw keft and waste doesn't work unfortunately.

 

For instance a 3ft diameter 10ft log has an actual volume of 70 cube (rounded), a hoppus volume of 55 cube and a volume using 3 instead of Pi of 67 cube.

 

Alright, so which one is most suitable?

[openspaceman]

Is there any online calculators to work out hopus foot.

 

It's too simple to need one if L is the length and QG is a 1/4 of the mid girth then

 

=L*QG^2/144

 

dropped in a spreasheet gives Hft

 

Who still uses Hoppus feet?

[Big J]

 

Who still uses Hoppus feet?

 

Almost everyone I know.

 

How else do you measure a sawlog? Measuring by tonne is prone to pitfalls if a log has defect that you need to measure out. Additionally, many small sawmills won't always buy in by the wagon load (no weigh grab).

 

Celtictimber - the hoppus measurement is really tremendously simple. Measure you girth (all measurements in inches). Divide that measurement by 4. Multiply it by itself. Multiply that number by the length. Divide by 1728 for the hoppus foot measurment.

 

Jonathan

[difflock]

J.

I was not suggesting the 0.14159 element of PI would compensate for the saw kerf.

Rather that no point in using it if deducting a kerf wastage %age anyway.

To make for simple sums.

ps

(i)Cept ussens went metric in 1972/3.

(ii)So what do the Germans do in respect of Hoppus meters (which would be an unusably large unit)

(iii) Actually with the very rapid progress in laser scanning technology, it should be relatively simple to build a hand held unit to scan the log, thereby measuring it, and calc the usuable timber within.

N.B.

decimal figs for Pi from memory.

well kinda, with the aid of a nemonic.

"Sir, I bear a rhyme excelling, in mystic force and magic spelling"

It has more verses that I did not bother to learn, 11 decimal places generally being sufficient for most calculations.

[Celtictimber]

Is there such a calculation for hoppus cubic meter

[Celtictimber]

Am I right in thinking that if you can multiply the m3 of a round log by 0.7852 and that will give you the hoppus m3