FIELD OF THE INVENTION
[0001] This invention pertains to the construction of log walls and utilizes natural tapered
whole logs which are fit together and laid horizontally on top of each other. Traditionally,
this type of wall construction has always been done by hand, using a chainsaw. A lateral
notch, also known as a groove or cope, is cut with a chainsaw from the underside or
belly of each log, and runs the full length of each wall log. This is an extremely
heavy, labour intensive and repetitive task. This invention will eliminate the time-consuming
hard labour involved, but will still result in the hand-crafted look of tapered log
walls. The art and craft of building with natural logs continues to gain appeal, and
removing this labour intensive aspect of the construction will allow time for log
builders to focus more on innovative and creative hand-crafted corner notches and
other details unique to their own style of building.
DESCRIPTION OF THE PRIOR ART
[0002] There are various means by which horizontally stacked logs or milled timbers are
notched or joined together. With conventional "milled" or "machine-cut" house logs,
there is a huge amount of waste wood created. D-shaped logs and double tongue and
groove style logs are machined out of dimensional timbers and then profiled to resemble
"real logs". Lathed (round) logs are all milled to exactly the same diameter; the
tip size of the tree determines the final size of the log. An enormous amount of waste
wood is generated as the log is lathed down to it's smallest dimension, often being
as little as 6 inches in diameter. Up to 40% of the wood becomes waste.
[0003] Conventional milling systems are also limited in the length of logs that can be used.
An unfortunate consequence is the practice of "end-butting" timbers within a wall;
ie: 2 - 20 ft. pieces of log are butted end to end to create 1 - 40 ft. length. This
negatively affects the building both esthetically and structurally and can cause air
leak problems.
[0004] United States Patent No. 4,312,161 to Goldade teaches the shaping of elongate cylindrical
structural members for their interfitting in the construction of walls or similar
structures. This provides an example of machine profiled timbers that have been cut
from whole logs.
[0005] United States Patent No. 4,903,447 to McDade teaches a variation on machine profiled
logs which utilizes a double tongue and groove type of joinery and creates an exterior
wall profile that resembles shiplap siding.
[0006] United States Patent No. 4,510,724 to Magnuson teaches timber construction which
incorporates the natural taper of the timbers and uses a uniform notching system for
corner joinery. However, this system again relies on each timber being profiled to
exact matching dimensions, again generating substantial amounts of wood waste and
increased costs. There are machines currently utilizing curved planer heads to peel
logs. As well, hydraulic equipment is being widely used in the wood manufacturing
sector to position logs, align them on a determined plane, rotate them and mill them
as required. Laser levellers are used in conjunction to ensure accuracy.
SUMMARY OF THE INVENTION
[0007] There is a growing world-wide shortage of timber, thus, the reduced amount of wood
that is being harvested must be used to maximum advantage, achieving the highest value-added
possible. This invention allows for the full utilization of each naturally tapered
log used in wall construction. Essentially, only the bark and a very small portion
of log are unused, and the bark can be sold as landscape mulch.
COMPARATIVE TABLE SHOWING WOOD CONSUMPTION BASED ON TYPE AND SIZE OF LOGS USED
[0008]
Number of logs required to gain 120 inches (or 10 ft) in wall height: |
6" double tongue and groove |
20 logs high |
maximum obtainable length is 24 feet |
8" double tongue and groove |
15 logs high |
maximum obtainable length is 24 feet |
10" round lathed logs |
12 logs high |
13" average diameter logs must be used and 30-40% of the wood becomes waste; maximum
obtainable length is 28 ft. |
10" tip, 16" butt trees (natural tapered logs) - 13" average diameter |
9.2 logs high |
full length trees can be used (up to 55 ft.long) resulting in maximum height gain
per round |
[0009] There are also substantial savings in the cost of labour due to increased productivity
when using a tapered log milling machine to create lateral grooves. It is estimated
that this process will produce 6-8 times more lineal footage of lateral grooves per
man day than a log builder using a chainsaw. This would allow increased time for the
more individualized and creative aspects of craftsmanship involved in the log construction
industry. As well, it is anticipated that the widespread use of this process would
result in reduced incidence of back-related injuries now common in this industry,
since the repetitive and prolonged use of the chainsaw to create lateral grooves would
be eliminated.
[0010] Increased thermal mass of log buildings and higher R-values of log walls are achieved,
due to the larger diameter of logs using the natural tapered milling method. Greater
flexibility in design is also possible due to the long lengths of logs that can be
used; no end-butting is necessary. Milled natural tapered logs would have the appearance
and appeal of hand-craned or hand-scribed joinery.
DESCRIPTION OF THE DRAWINGS
[0011]
FIG. 1 is a perspective view of a section of log wall illustrating the natural taper
of the logs as they lay, alternating a butt 11 (largest diameter of a log) with a
tip 12 (smallest diameter of a log) and achieving level every 2 rounds (a "round"
is a single layer of logs around the complete perimeter of a building).
FIG.2 is an end view of a log wall illustrating the alternating butts 11 and tips
12 of logs and indicating common curvature 13, matching the milled convex surface
of the top of each log to the milled concave surface on the underside of the log above
it.
FIG.3 is an enlarged end view of a log wall illustrating the use of a common curvature
13 on various diameters of logs resulting in the exact matching of convex to concave
surfaces, joining log to log and illustrating the amount of wood removal in the process:
from the underside of a log 14 and from the top side of a log 15.
DETAILED DESCRIPTION OF THE INVENTION
[0012] This process utilizes a machine to create the lateral notch, also known as a groove
or cope, on the underside of a house building log and to mill a matching convex surface
on the top of each log, creating walls that maintain the natural taper of each whole
log used (refer to FIG. 1). Referring now to FIG. 2, 13 the convex curvature of the
top of each log will be milled to match the concave curvature on the bottom of the
log sitting directly above it, using a common curvature 13 for specified diameters.
A 16 inch diameter curvature is defmed as being equal to any portion of the perimeter
of a 16 inch circle. Similarly, a 10 inch diameter curvature equals any portion of
the perimeter of a 10 inch circle; refer to FIG.3 13. The key factor in this process
is to use logs of similar taper and mill them to
exactly the same degree of taper. This is accomplished by positioning the log that is to
be milled so that the top surface is on a horizontal plane. The concave groove is
then cut into that surface. The log is then mechanically rotated 180 degrees so the
opposite surface of the log is on top. Once again, hydraulic lifters and laser levellers
position the log so that the top surface is essentially on a horizontal plane, with
the log held in position so that the planing process results in creating the identical
degree of taper in every log. A matching convex curvature is then milled on this surface.
By using the same curvature throughout, no matter what diameter of log is used, level
wall height is achieved every 2 rounds* (refer to FIG.1); this is contingent upon
logs being stacked so that, at each end of the wall being built, a butt 11 (or largest
diameter of a log) alternates with a tip 12 (or smallest diameter of a log); refer
to FIG.1.
*A "round" is a single layer of logs around the complete perimeter of a building
[0013] In the process of milling and matching concave to convex surfaces, an extremely small
amount of waste wood 14 and 15, is generated.
[0014] Trees grown in the same area have similar taper. Ideal house logs have 1 inch of
taper in every 10 feet of length. If the taper is greater than that, the machine can
still be used with the same results. Cutting blades with different curvatures would
be used for different diameters of logs, however, with this concept, the same curvature
blade and the same degree of taper in the logs used must be maintained for any one
complete building. Logs ranging from 5 to 10 inches in diameter would use a 10" curvature
blade. Logs ranging from 10 to 16 inches in diameter would use a 16 inch curvature
blade. Logs ranging form 16 to 24 inches would use a 24 inch curvature blade.
[0015] A natural tapered house log milling machine would be designed so that the machine
head would move down the length of the log, as opposed to the equipment being stationary
and the log being turned and moved. This would enable logs of up to 55 feet in length
to be milled.
1. A process for milling whole natural logs for logs wall construction from selected
logs of similar taper, the process comprising steps of:
planing a convex curvature on a longitudinal surface of each of the selected logs,
the convex curvature having a curvature determined in accordance with a diameter range
of the selected logs;
milling an opposite surface of each of the selected logs to form a concave curvature
such that longitudinal surface and the opposite surface have an identical degree of
taper, and to form a lengthwise lateral notch in the opposite surface to identically
match the curvature of the convex curvature.
2. The process of claim 1, further including steps of mechanically rotating the log through
180° to expose the opposite surface and positioning the opposite surface in an essentially
horizontal plane, prior to the planing process.
3. The process of claim 1, wherein the selected logs have a maximum, butt diameter approximately
15 cm (6 inches) greater than the minimum tip diameter.
4. The process of claim 3, wherein for selected logs the determined curvature is approximately
equal to the maximum butt diameter.
5. The process of claim 1, wherein the determined curvature is about 25 cm (10 inches)
when the diameter range of the logs is about 13 - 25 cm (5-10 inches).
6. The process of claim 1, wherein the determined curvature is about 41 cm (16 inches)
when the diameter range of the logs is about 25 - 41 cm (10-16 inches).
7. The process of claim 1, wherein the determined curvature is about 61 cm (24 inches)
when the diameter range of the logs is about 41 - 61 cm (16-24 inches).
8. A method for building a log wall construction from selected logs of similar taper,
comprising:
milling a convex curvature on a longitudinal surface of each of the selected logs,
the convex curvature having a curvature determined in accordance with a diameter range
of the selected logs;
planing an opposite surface of each of the selected logs to form a concave curvature
such that longitudinal surface and the opposite surface have an identical match of
curvature of the convex curvature;
laying a first round of logs such that a butt end of each log abuts a tip end of an
adjacent log, and the convex curvature of each log forms a top of the first round;
stacking a second round of logs on the first round such that each butt end of the
second round of logs alternates with a tip end of the first round, and the lengthwise
lateral notch of each log of the second round faces downwards and coincide with the
convex curvatures of the first round; and
repeating the steps of laying and stacking to form the log wall construction such
that every second round provides a level wall height.