Pattern Development Shortcuts

Question 1

When are shortcut methods not recommended?

Answer 1

When extreme accuracy is important or when a fitting or object has extreme changes in dimension or direction.

Question 2

What are the two common pattern development shortcut methods?

Answer 2

The rollation method and the slipping method

Question 3

What is the difference when rolling a rectangular fitting compared to a rectangular fitting?

Answer 3

The difference when rolling a rectangular fitting is that it must rotate on its corners and the straight edges must be traced once they are laying flat on the material.

Question 4

What does being able to calculate a mitre allow you to do?

Answer 4

Allows you to make an offsetting duct fitting on the job to change position for various reasons such as avoiding obstacles.

Question 5

What is important to remember when making your own offset as opposed to using an ogee offset?

Answer 5

It will have higher resistance to airflow than an ogee offset.

Question 6

What are the limitations to creating your own offset?

Answer 6

The length of the offset needs to be at least 24” and you should not have an offset of more than 6”

Question 7

How do you calculate the mitre allowance when creating an offset?

Answer 7

Multiply the offset amount (O) by the dimension of the side of the duct being offset (W), then divide by the length of duct used (L)

M = OxW
____
L

Question 8

Knowledge of advanced pattern development is necessary for creating a rollation pattern. True or False?

Answer 8

True

Question 9

Extreme differences in opening dimensions and altitude make using pattern development shortcuts more accurate. True or False?

Answer 9

False

Question 10

When is slipping a pattern commonly used?

Answer 10

When developing transitional elbows and offsets

Question 11

You must use a 36” piece of duct when creating an offset in the field. True or False?

Answer 11

False

Question 12

What is the mitre cut-out needed for a 12 x 6 piece of duct, offsetting 4” over 30” in length?

Answer 12

1 5/8”

Question 13

If a piece of duct is needed to drop 3” over 24” to clear a vacuum rough in. What would the mitre cut be when the duct is measured 20 x 8?

Answer 13

2 1/2”

Question 14

What is good practice if an 18” long transition is needed to clear a 6” vent stack?

Answer 14

Order an ogee offset

Question 15

What must be done before a slip pattern can be developed for a transitional elbow?

Answer 15

You must develop the flat cheek pattern, then the heel and throat wrappers.

Question 16

A centre tapering transitional elbow pattern is developed with the slip technique. True or False?

Answer 16

True

Question 17

When developing a pattern for a transitional elbow, what must be done to determine the amount to slip the flat pattern?

Answer 17

Determine the difference between the wrapper’s flat and transitional lengths.