Hoppus Calculation

[muttley9050]

After much research im still stuck, so,

1. How do i work out the hoppus of a standing oak tree?

2. Does your hoppus calculation change for different species to take into account larger bands of sapwood, or does sapwood get included in calculation?

 

Thanks

James

[agg221]

OK, the simple bit is how to calculate.

 

Work out the circumference halfway along the sawlog in inches(rounded to the nearest whole number). You will probably have to guess a bit unless you can climb up to it.

Divide this number by four.

Square it.

Divide by 144.

Multiply by the length in feet.

 

The above is the number of Hoppus feet in your log.

 

The measurement is made over the bark. It allows for this in the calculation and is an estimate that lies between measured cubic feet of total volume, and measured cubic feet of heartwood, so is a bit of a guesstimate at useable timber, but is as fair as is practible to both buyer and seller.

 

The other question is, why do you want to know? It's only really useful for buying and selling. For your own use, measuring top diameter of the useful timber, dividing by two to get radius, squaring, multiplying by 3 (approximation to pi) and then length gets you a more useful figure of what you might get out of it.

 

Alec

[G'day Spruce]

Hmmm, from my experience with this lumber measurement, you need a hoppus girth tape and a hoppus conversion book, if my memory serves me right a hoppus foot is 28% more than a cubic foot. The measurement allows for wastage at the mill, if trees were square we wouldn't need the measurement....

[agg221]

Hmmm' date=' from my experience with this lumber measurement, you need a hoppus girth tape and a hoppus conversion book, if my memory serves me right a hoppus foot is 28% more than a cubic foot. The measurement allows for wastage at the mill, if trees were square we wouldn't need the measurement....[/quote']

 

Your memory serves you right on volume, but you no longer need the tape and book if you have a pocket calculator or mobile phone:001_smile:

 

Alec

[muttley9050]

Thanks, I see your point alec. I'm used to dealing with milled timber really, just trying to work out this oak for the floor/sills and see if the one oak will be enough and how to allow for sap wood, metal in tree etc. The first oak is hedgerow but we have another in woodland we also want to mill and wondering if we can mill both in a day with a Lucas. Think I'm gunna send pics to sawyer and see what he thinks, what do you think?

 

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[wisewood]

OK, the simple bit is how to calculate.

 

Work out the circumference halfway along the sawlog in inches(rounded to the nearest whole number). You will probably have to guess a bit unless you can climb up to it.

Divide this number by four.

Square it.

Divide by 144.

Multiply by the length in feet.

 

The above is the number of Hoppus feet in your log.

 

The measurement is made over the bark. It allows for this in the calculation and is an estimate that lies between measured cubic feet of total volume, and measured cubic feet of heartwood, so is a bit of a guesstimate at useable timber, but is as fair as is practible to both buyer and seller.

 

The other question is, why do you want to know? It's only really useful for buying and selling. For your own use, measuring top diameter of the useful timber, dividing by two to get radius, squaring, multiplying by 3 (approximation to pi) and then length gets you a more useful figure of what you might get out of it.

 

Alec

 

Hi Alec,

 

I'm interested in working out the volume of the logs I'm carving. They are bought by weight which is not ideal and I'd like to see how much of a difference there is between weight price and Hoppus price.

In your calculation above you divide by 144 and then x the log length, I was looking online for the calculation and this one hoppus foot you x length first and then divide by 144

 

I'm confused again:lol:

 

Cheers,

 

Si

[Rhob the Log]

I liked Big J's calculation more than Alec's (sorry Alec )

 

1/4 girth squared x length [all in inches]

--------------------------------------

1728

 

Interestingly, when voluming (yes, I know that's not a word...) your sawn boards, take the length x width x depth (again, all in inches) and divide by 1728 and you have your cubic feet... hope that's a help!

[agg221]

Hi Alec,

 

I'm interested in working out the volume of the logs I'm carving. They are bought by weight which is not ideal and I'd like to see how much of a difference there is between weight price and Hoppus price.

In your calculation above you divide by 144 and then x the log length, I was looking online for the calculation and this one hoppus foot you x length first and then divide by 144

 

I'm confused again:lol:

 

Cheers,

 

Si

 

It doesn't matter which order you carry out multiplication or division operations in (this is a general mathematical rule).

 

I prefer to state it as divide by 144 first as I find it a bit more logical. 144 is 12 squared. The quarter-girth measurement is made in inches. Squaring it gives an area in square inches. To convert to square feet divide by 144, so this is basically the 'face area' of the log in square feet.

 

Firstly, I find this more logical and hence easier to remember. Secondly, I find remembering the comparison between several logs easier if I just have to remember a smaller number in square feet, and then multiply by the length in feet to get cubic (Hoppus) feet.

 

Hope the above is clear!

 

An example of why.

 

Say I have a real log, rather than a neat, hypothetical cylindrical forest-grown log. It's 24' long and 2' dia or so for most of its length, with a severe narrowing to 18" about 16' up, due to a previous side branch.

 

If I'm looking at maximum use, I could treat it as two cylinders - first one has a mid quarter girth of 19", so an area of 361 square ins, or 2.5 square ft. Its volume is 2.5x16=40 Hoppus feet. The second one has a mid quarter girth of 14 ins, so an area of 196 square ins, or 1.36 square ft. Its volume is 1.36x8=11 Hoppus feet. This makes a total of 51 Hoppus feet.

 

However, say I want to consider using it as a full length beam. This means I can only use the smaller area, so already know its area (1.36 square ft) and just multiply by the length of 24ft to get 32.6 Hoppus feet. I now know I'm throwing away 18.4 Hoppus feet if I do this (or using them if I can as thinner boards etc).

 

I find this really useful in assessing potential ways of breaking down timber with step changes in diameter, bends and kinks, rot or other damage etc. but I have no idea if it helps you in the slightest!

 

Alec

[wisewood]

Thanks Alec,

Well put and very informative.

[Copford sawmill sussex]

Yeah I use tape and book but my dad uses your method Alec

 

 

http://Www.Copfordsawmill.co.uk

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