## Red and White Oak Characteristics

Comparing the characteristics of white and red oak.

The information on this table is for comparison purpose only. The characteristics of samples vary a great deal. These figures are from several different sources. There is a list after the table.

Oak type | Other Names | Location | ^{1}Modulus of Rupture |
^{2}Stiffness or Modulus of elasticity |
^{3}Janka Hardness |
^{4}Dry Weight |
^{5}Shrinkage |

Red OakQuercus rubra, Quescus borealis |
Northern red oak, Champion Oak | South East and Central Canada, Eastern and Central US | 14,380 lbf/in^{2} (99.2 MPa) |
1,761,000 lbf/in^{2} (12.14 GPa) |
1,220-1290 lbf (5,430 -5,700 N) | 43-47 lbs/ft^{3} (689-752 kg/m^{3}) |
Radial:4% Tangential: 8.6% Volume: 13.7% |

White OakQuercus alba |
Stave Oak, ridge white oak, fork leaf oak | South East and Central Canada, Eastern and Central US | 14,830 lbf/in^{2} (102.3 MPa) |
1,762,000 lbf/in ^{2} (12.15 GPa) |
1,350-1360 lbf (5,990-6,000 N) | 45-50 lbs/ft^{3} (721-801 kg/m^{3}) |
Radial:5.6% Tangential: 10.5% Volume: 16.3% |

The reported values are not standardized and vary depending on who is reporting. For example the values for the Western Red cedar and Yellow cedar are shown higher in State of Alaska figures than in the Wood Database.com. Engineering Data Real cedar.com. Wood Structural Design Data. Engineer's Edge has material data tables. Is there an advantage in reporting high in order to encourage sales? Or is Alaska timber superior to others? A bit of both maybe. At any rate, these figures are for rough comparison only.

Most of my figures come from Gov. and Engineering sources. They usually are similar and if there is a discrepancy I use an average. Don't rely on these figures for engineering purposes or for research. They are not primary sources. I have not done these tests.

## Explanation of the tests and values

#### 1- Modulus of rupture, or Bend Strength

Units: lbf/in^{2} = pounds of force per square inch. MPa = Mega Pascal Mega is one million, Pascal is a unit of force defined as one newton per square meter. A newton, in the metric system, is how much force is required to make a mass of one kilogram accelerate at a rate of one metre per second per second.

Flexural strength, also known as modulus of rupture, or bend strength, or transverse rupture strength is a material property, defined as the stress in a material just before it yields in a flexure test.

A standard size sample is placed with supports at both ends and a force is applied in the middle. The sample gradually bends (flexes) as the force is applied and eventually breaks. The force is measured at the point when the sample breaks.

It is not an absolute test because results can vary. Some woods, for example, might break later if the force was applied more gradually. The test is useful as a comparison between woods.

#### 2- Modulus of elasticity (stiffness)

Units: lbf/in^{2} = pounds of force per square inch. GPa = Giga Pascal Giga is billion (10^{9} or 1,000,000,000). Pascal is a unit of force defined as one newton per square meter. A newton, in the metric system, is how much force is required to make a mass of one kilogram accelerate at a rate of one metre per second squared.

Modulus of elasticity also known as Yong's Modulus measures how stiff a sample is. It is expressed as a ratio of stress over strain. In other words, how much something bends (strain) under a given load (the stress). The higher the number, the stiffer the material.

Don't worry too much about the units. They are mostly useful to compare between the different woods.

Here is my page explaining in greater detail, Yong's Modulus in relation to carbon fibre. Carbon fibre has a yong's modulus of 181 GP compared to Western red cedar which has 7.6 GP.

#### 3- Janka Hardness

Units: lbf = pounds of force. N = Newton, A newton, in the metric system, is how much force is required to make a mass of one kilogram go faster at a rate of one metre per second squared.

The Janka Hardness Test measures the resistance of a sample of wood to denting and wear. It measures the force required to embed an 11.28 mm (.444 in) steel ball into wood to half the ball's diameter. This method leaves an indentation. Commonly used to compare woods that are suitable for use as flooring.

The higher the number, the harder the wood is to dent. BALSA requires 100 pounds of force (lbf) while SUGAR MAPLE requires 1,450 lbf to embed the steel ball halfway in the sample.

#### 4- Average Dried Weight

units: lbs/ft^{3} = pounds per cubic foot. kg/m^{3} = kilograms per Metre cubed.

In doing the measurements for the average dried weight, the moisture content is assumed to be at 12%.

#### 5- Shrinkage

Radial Shrinkage refers to shrinkage across the growth rings. In other words shrinkage of the radius of a log.

Tangential shrinkage is shrinkage in the direction of the growth rings.

Volumetric shrinkage is a combination of shrinkage in all directions.

longitudinal shrinkage is often not reported because it is not usually significant. Wood shrinks little in the length of a plank.

Generally, the greatest shrinkage will occur in the direction tangential to the growth rings. Wood shrinks about half of that tangentially, that is radially from the centre to the outside across the growth rings. Longitudinal shrinkage along the grain is virtually negligible in small pieces.

T/R is the ratio of Tangential over Radial shrinkage and the larger the number the less stable the wood. Less stability implies greater movement, warpage and cracking.

## Books about Wood and Woodworking

- Building cedar strip canoes

email me if you find mistakes, I'll fix them and we'll all benefit: Christine

#### Cedar

Wikipedia.com article on oak

Grades of Hardwood Lumber

My page on strip building

The Wood Database is lots of fun. Great information and articles. Check it out.

Viking Ships were often made of Oak Lumber

Woodwork web, is a great online resource, also available as a book.

### Small Print

I don't claim to be an expert in anything. Use safety equipment when working on your boat and wear a lifejacket when boating. Verify that any material you plan to use is suitable for your purpose. Wood is a natural product that varies a lot depending on growth conditions.