hoppus foot

In Great Britain, Australia, New Zealand, Burma and some Caribbean colonies, 18th – 20th centuries, with more restricted use in the 21st century, a unit used to evaluate a log in terms of an estimate of the volume of rectangular sawn wood that could be cut from it. It is rarely, and improperly, applied to sawn wood. Symbol, “hft”, sometimes “h cu ft”. Evaluations of standing timber in a forest were also often expressed in hoppus feet per acre. One hoppus foot per acre is equivalent to 0.089 cubic meters per hectare. One hoppus foot is 1.273 cubic feet; the 0.273 excess represents the loss in sawing the log.

One hoppus ton = 50 hoppus feet.

With metrification, in Great Britain use of the hoppus foot has been restricted mostly to hardwood logs. In the 21st century, it is used in Myanmar for teak veneer logs, and in Trinidad and Tobago it is the unit used in issuing licenses for felling trees on state forests.

To calculate the number of hoppus feet in a log, measure a quarter of the girth of the log midway between the ends in inches, square the result, multiply by the length in feet, and divide by 144. Rather than divide the girth by 4, it was often measured with a special tape calibrated in quarter-girth inches (QG inches), i.e., numbered tally marks a quarter of an inch apart. 

The girth of a strongly tapered or irregular log might be measured at several equal intervals, instead of only at the midpoint, and the results averaged.

The hoppus foot is conventionally thought to be equivalent to 10 board feet of sawnwood. Statistics kept in Trinidad and Tobago show that for the years 1995 through 1999, the mean number of board feet obtained per hoppus foot fell in the range 8.8 to 11.2. However, these statistics should be approached cautiously. They also show that in 1997 some sawmill managed to get 215.7 board feet from a hoppus foot, which is mathematically impossible, barring a loaves-and-fishes miracle.

The hoppus foot is named for Edward Hoppus, “surveyor to the corporation of the London Assurance,” who described this method of estimation in a book published in 1736. The author died three years later, but his book was wildly successful, going through numerous editions in the 18th and 19th centuries.

For another log rule, see Scribner-Doyle rule.

Edward Hoppus.
Practical measuring now made easy to the meanest capacity by a new set of tables ready calculated after a plain, easy and correct method which by a bare inspection shew what is the solid or superficial content (and consequently the value) of any piece or quantity of timber, stone, board, glass …
London: Printed and sold by E. Wicksteed, 1736.

Bertram Husch, Thomas W. Beers, and John A. Kershaw, jr.
Forest Mensuration. 4th edition.
John Wiley and Sons, 2002.

sources

 

To measure round Timber that is not tapering.

1. With a rule measure the length of the piece in feet and quarters of a foot, if necessary, and set it down in your memorandum-book; then reduce it to square timber thus :.

2. With a chalk line, or packthread, girt the piece in any place; then double the line twice, and you have one-fourth of the girt, for the side of the square, which you must exactly measure upon your rule, and set down in inches, and quarters of an inch. Having thus reduced the round timber to square timber,

3. Look at the top of the Table of Solid Measure, for the side of the square, equal to ¼ of the girt, and keep your eye down the left hand column, till you find the length of the piece in feet, and over-against it stands the content of the piece sought, in solid feet, inches, and twelfth parts of an inch.

To measure Tapering Timber.

Tapering timber, is timber that is smaller at one end than the other, as Fig. 3., and consequently it will not carry the same square from end to end, throughout the whole piece: when you have found what square the tree will carry throughout, by taking one fourth of the girt (as you were taught on page xxi.), you must proceed exactly as in the case of round timber, already taught.

To find what square a tree will carry throughout, the shape, or figure, of the tree should be very carefully observed; and if the sides of the tree are straight from end to end, as Fig. 3., then it may be girt, and the square taken in the middle, from the butt-end and top, as in the common practice amongst workmen: or you observe this

RULE.

Take one-fourth of the girt at each of the ends; add them together, and take half of that sum for the side of the square,

which the tree will carry throughout; as you will find exemplified in Example III, page xi.

N. B. If the tree does not taper gradually, but is unequally thick, then you may girt it oftener; always remembering to divide the sum total of the several fourth parts of the girt, by the number of times the piece was girted, and it gives the side of the square the tree will carry throughout.

If you have any odd parts of a foot, in the length of a tree, you are to proceed as directed in the case of square timber, having odd parts in the length.

E[dward] Hoppus.
Hoppus's Tables for Measuring, or Practical Measuring Made Easy, by a New Set of Tables... A New Edition.
London: Printed for Longman and Co., etc., 1837.
Pages xxi-xxiii.

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