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Journal

The Hoppus Foot



What even is the Hoppus Foot?


This is an article for anyone who, like us, dabbles in hardwoods. Anyone who wonders why, when they go through life in cubic metres of roundwood they get to the sawmill only to be hit in the face with a hoppus foot. Anyone who wonders why, in a decimal world, the hoppus foot still exists. We’ll look at how arcane yet vital the system is to today’s hardwood industry.


A brief history of measuring timber


Noah’s ark, built in Gopher wood, was measured in cubits. A measure from the elbow to the tip of the middle finger, it served us well for a time. After a few thousand years the world of imperial distance measurement managed to move from the arm to the foot. The foot spread and in time a system of volumes for logs was developed based on cubic feet. This system took account of the fact that a log is a circle in cross section, yet what we want to know is the volume of actually usable timber, which is normally rectangular. There were others who tabulated this conversion but Edward Hoppus’s system from 1736 stuck.


Measuring the total volume we can call the full-volume system, measuring a partial “usable” volume we’ll call the hoppus system for this article.


What makes the hoppus foot so confusing?


After over 20 years in the trade I still find it confusing. I’m numerically pretty illiterate but I can understand a cubic metre, so what’s the problem with the hoppus foot?


Do a search on Google and see. You’ll find as many websites that claim a hoppus foot is the rectangular cubic foot with the sides, the falling boards, still on as there are who claim a hoppus foot is the total volume of the log minus the sides. Both claim to give a much more accurate descriptor of the amount of sawable timber than just using cubic feet. Some sites show that the hoppus system is both of these.


To add to the confusion there are a number of different ways to measure hoppus foot. The Timbeter website has a good description. The standard formula uses “quarter girth”. In my naive mind this was used so that you didn’t have to measure the whole girth of a log lying on the ground. But actually, you still grovel around on the ground poking quarter-girth tapes through holes under the log to try and wrap it around the whole log in order to find its quarter girth.


Hoppus Volume (h ft) = (“Quarter Girth” (in))2 × Length (ft) / 144 = (circumference (ft) / 4)2 × Length (ft)

I started to do a comparison of full volume and hoppus volume. But lost the will having to switch between diameters, circumferences, and quarter girths.


So why bother?


Having a measurement that discounts the parts of the log that are never going to be sawn is useful. It gives a better measurement of a log for the sawmiller to understand how much board will come out. Plus, having a set of hoppus tables makes life very easy.


So why not bother?


For a start, it’s imperial. I’m pretty old and we switched to metric before I was born. We could use metric hoppus metres presumably but no one, as far as I know, either uses them or has produced tables for them.


The softwood industry has embraced both metric and full-volume systems and quite happily manages with both. It shows that though there may be a benefit to a niche system such as hoppus feet, the ability to transfer volumes across the supply-chain in a universally understandable way is much more important.


Using a full-volume system also acknowledges two things:


  • That there is value in the rounded edges the hoppus system sets out to exclude. Whether they are chipped for mulch or for biomass systems or other uses, they are still a part of the log with value.

  • There are other equally important factors in sawn outturn as the volume. Taper, knottiness, grain angle, wood type etc will all play an equally important factor.


Hoppus feet are like forestry yield class tables (we’ll do an article on these soon you lucky people). They work for a perfect log or perfect tree but only give a part of the story. If they only give part of the story why not use a simpler system with more universal understanding?


The romanticism of the hoppus foot


Using hoppus feet isn’t really about the accuracy the unit of measurement gives. It’s about maintaining a craft that is handed down. I don’t know of anyone who has gone out of their way to learn the hoppus system, almost always the knowledge is handed down from forester to forester, miller to miller.


Hoppus feet maintain an arcane language of a craft that ensures its continuation. To lose hoppus feet would likely include the loss of the knowledge of assessing timber quality of high-quality standing oak. The loss of understanding how hardwood species differ under the saw. Or of handshake agreements between forester and miller. And of knowledge handed down from old to new generations.


For all its faults, to lose all of the craft of hardwood processing for the sake of technological advancement would be tragic. But moving to a full volume cubic metre would also open up the sector to a more diverse range of new-entrants, investors and users. It may allow small woodland owners, for instance, the ability to play in the market using simple measurements (or apps) to sell their timber.


A brave new world


How do we navigate this new world of needing to maintain craft but also move forward as the world grows increasingly complex and necessarily inclusive? How do we evolve into a world of hardwood growing and processing that brings with it all that craft knowledge that is important, but for the sake of progress, archives all that isn’t needed anymore? We need to find a balance between craft, tradition, technology and new paradigms. Which side of the balance does the hoppus foot fall?


This isn’t really an article about hoppus feet. It’s about the world of forestry and timber we inhabit and the questions we have to face to stay relevant. It could be about forest inventory, yield-classes, species choices, our obsessive focus on high-forest, or any number of those techniques we cling onto in the belief they are foundations of our profession. Answers on a postcard please.





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